Middle Carboniferous and Lower Permian Fusulinacean ... · Middle Carboniferous and Lower Permian Fusulinacean Biostratigraphy of the Akiyoshi Limestone Group, SouthwestJapan. Part

Bull. Kitakyusku Mus. Nat. Hist., 16: 1-97. March 28, 1997

Middle Carboniferous and Lower Permian Fusulinacean

Biostratigraphy of the Akiyoshi Limestone Group,Southwest Japan. Part I

Yasuhiro Ota

Department of Earth and Planetary Sciences, Faculty of Science,Kyushu University33, Hakozaki, Fukuoka 812,Japan

(Received October 31, 1996)

Abstract The Akiyoshi Limestone Group, oneof the most representative stratigraphicstandards ofJapanese Carboniferous and Permian, is widely distributedin the AkiyoshiTerrane, Southwest Japan.

TheJigoku-dani area, the main area for investigation, is located in the northwesternpart of the Akiyoshi Plateau, where the Middle Carboniferous and Lower Permian

limestones are widely exposed. They are mainly composed of micritic limestones,indicating a lagoonal facies, in the relatively low energy environments within theAkiyoshi organicreefcomplex. The limestones are alsocharacterized by abundant andwell-preserved fusulinaccans, and the following nine zones including seven subzones,were recognized in ascending order as: 1. Fusulinella biconica Zone, 2. Fusulina cf.shikokuensis Zone: 2-1. Fusulinella cf. obesa Subzone, 2-2. Pseudofusulitulla hidaensisSubzone, 3. Obsoletes obsolelus Zone: 3-1. Protriticites toriyamai Subzone, 3-2. Protriticitesmatsumotoi Subzone, 4. Montiparus sp. A Zone, 5. Triticites yayamadakensis Zone: 5-1.Triticites saurini Subzone, 5-2. Schwagerina sp. A Subzone, 5-3. Triticites biconicus Subzone,6. Schwagerina (?) cf. satoi Zone, 7. Pseudoschwagerina muongthensis Zone, 8. Pseudqfusulinavulgaris globosa Zone, 9. Pseudofusulina afi". ambigua Zone. The distribution of thesefusulinacean zones shows well the inverted structure of limestones in this area.

The second investigated AK area is located in front of the Akiyoshi-dai Museum ofNatural History, where limestones with nearly complete successions of the MiddleCarboniferous to Lower Permian are well exposed. The following fusulinacean zonesare discriminated alonga measured traverse, in ascending order:Pseudofusulinella hidaensisZone, Protriticites matsumotoi Zone (s. I.), Montiparus sp. A Zone, Triticites simplex Zone (s.1.), Pseudoschwagerina muongthensis Zone, and Pseudofusulina vulgaris Zone. Of them,Protriticites matsumotoi Zone (s. I.) is tentatively subdivided into the lower Protriticitesmatsumotoi Zone (s. s.) and the upper Quasifusulinoides sp. A Zone. Triticites simplex Zone(s. 1.) is tentatively subdivided into the lower Schwagerina sp. A Zone and the upperTriticites simplex Zone (s. s.). Limestones in this area mainly consist of alternation ofmicritic limestones and those with sparry calcite matrices. The facies of limestonesindicate that they represent a marginal lagoon paleocnvironment. The limestones inthis area explain the two sequences.

The third investigated area, Mt. Maruyama, contains Middle and Upper Carboniferous limestones. They represent a sedimentary environment of reef flat or bypassmargin between the fore reef and open sea. They yield the primitive types of thegenusProtriticites, i.e., Protriticites yanagidai Ota, Protriticites masamichii Ota, and Protriticites

Yasuhiro Ota

toriyamai Ota. From viewpoints of their morphological characters and affinities,Protriticites yanagidai Ota represents a primitive stage in the phylogenetic line betweenProtriticites yanagidai Ota and Protriticites matsumotoi (Kanmera), whereas Protriticitesmasamichii Ota is likely to be a transitional species to Montiparus matsumotoi injlatus,reported by Watanabe (1991).

Based on these fusulinacean assemblages and phylogenetic considerations, it is

concluded that the variation of elements among fusulinacean assemblages is caused by

change of lithofacies in development of the Akiyoshi organic reef complex. It has a

large influence in recognition of the biostratigraphic units. The palcoenvironmental

analysis of the Akiyoshi organic reef complex is indispensable for establishment of thereexamined biostratigraphy.

Introduction

The study area is located in the Akiyoshi Terrane of Southwest Japan where the

Middle Carboniferous to Lower Permian Akiyoshi Limestone Group is widely distributed. The Akiyoshi Limestone Group which contains well-preserved fusulina-ceans and many other well-preserved mega-fossils is considered to have originally

formed as an organic reef complex upon a basaltic mound. This paper describes thefusulinacean faunas and discusses the elements of the newly discriminated fusulina

cean zones. It also examines the Middle Carboniferous to Early Permian fusulina

cean phylogenetic transition in the Jigoku-dani area and two other related areas onthe Akiyoshi limestone plateau.

The principal survey area, Jigoku-dani, is located in the northwestern part of theAkiyoshi Plateau. Karst topography characterized by lapie field, is well developedand a valley with a NE-SW trend is located in the middle of the area. Middle Carboniferous to Lower Permian limestones with a number of well-preserved fusulina-

ceans, are widely distributed. Consequently, this area was first selected for the examination of the transition of the fusulinacean assemblages during Middle Carbo

niferous to Early Permian. M. Ota (1977) suggested that the general strikes anddips of the Akiyoshi Limestone Group in the area are nearly horizontal. The authorset a starting point at an altitude of 355 m, and carried out field observation andsampling of materials with a measuring tape. The measured traverses (JI Traverse)were mainly drawn by crossing the general trend of the strike and sometimes drawnby lines parallel to strike. Limestone samples were carefully collected along themeasured traverses.

The second investigated AK area was selected in front of the Akiyoshi-dai Museum of Natural History. In this area, there are nearly complete successions of Carboniferous to Lower Permian limestones with abundant fusulinaceans. This area is

also characterized by a lapie field.The third investigated area, Mt. Maruyama is located in the Isa Quarry, Mine

City. A principal traverse was set and measured along the eastern slope of Mt.

Fusulinacean Biostratigraphy of the Akiyoshi Limestone Group, Part I 3

Maruyama at an elevation of about 200 m with the following abbreviation as MATraverse. This traverse was established by crossing the general strike of E-W trendat right angles. Limestones in this area are variable in their organic compositionwith rugose corals, ammonoids, phylloid algae, brachiopods and fusulinaceans occur

ring alone or together. The lithologic facies of limestones and their fossil components suggest that the paleoenvironment of this area was a reef flat or bypass marginbetween the fore reef part of the Akiyoshi organic reef complex and open sea (Fig. 1).

m 1

;

Fig. 1. Simplified geologic map of the Akiyoshi area, showing locations of the investigationareas, Jigoku-dani area, AK area and Mt. Maruyama area. 1. Akiyoshi LimestoneGroup. 2. Beppu and Ota Groups. 3. Tsuncmori Group. 4. Cretaceous sedimentaryand igneous rocks. 5. Major thrust.

Yasuhiro Ota

Historical review

-I. Geology of the Akiyoshi Limestone

The geology of the Akiyoshi Limestone and surrounding areas was first investi

gated by Ozawa (1923), who established the biostratigraphy by the use of fusulinacean zones. He discovered the inverted succession of the fusulinacean zones and

recognized the inverted sequences as an autochthonous recumbent fold caused by lateral movement from south to north. Ozawa's interpretation was developed byKobayashi (1935) and he proposed the Akiyoshi Phase for the first of the Mesozoic

orogenic movements. Toriyama (1954a, b, 1958) reexamined the geology andfusulinacean paleontology of the Akiyoshi Limestone Group and the surrounding

non-calcareous sedimentary rocks. He studied the Carboniferous and Permianfusulinaceans in detail and established refined fusulinacean zones on the Carbonif

erous and Permian limestones. The fusulinacean zones by Toriyama (1963, 1967,

1978) had been treated as a standard of the Carboniferous and Permian biostratigraphy in Japan. Along with the biostratigraphic work, Toriyama showed his interpre

tation on the geologic structure of the Akiyoshi Limestone Group. Later, Hasegawa(1958, 1963) and Murata (1961) showed different interpretations on the invertedstructure of the Akiyoshi Limestone Group.

Concurrently, a sedimentological study with the biostratigraphy, for the purposeof the paleoenvironmental examination had been started by M. Ota and others.Eto (1967) examined the bio- and lithofacies of the lower part of the AkiyoshiLimestone Group in the Okubo area. He analyzed biofacies of limestones and reconstructed the sediment depositional process of limestones on the volcanic sea-mount. In 1968, M. Ota first suggested for the paleoenvironments of the AkiyoshiLimestone Group that it was formed as an organic reef complex on the basaltic sea-mount like an atoll of the present ocean. This is an epoch-making study from theviewpoint of paleoenvironmental analysis on the Akiyoshi Limestone Group. Thedetailed lithology of the basal pyroclastic rocks was examined and described byYanagida, M. Ota, Sugimura and Haikawa (1971). They showed the sedimentarysequence of the Akiyoshi Limestone in the Shishide-dai area with a columnar sectionand description of the biostratigraphy of the lowest part of the Akiyoshi LimestoneGroup. Schwan and M. Ota (1977) carefully reexamined the geologic structures ofthe Akiyoshi Limestone Group and surrounding non-calcareous rocks. They suggested lateral and rotating pressures caused by gravity movement for the partly inverted succession of the Akiyoshi Limestone Group.

The new interpretation for the tectonics of limestones and the surrounding non-calcareous rocks, based on the plate tectonic theory of the new global tectonics, wasshown by Kanmera and Nishi (1983) and Sano and Kanmera (1988). They considered that the Akiyoshi organic reef was developed on a seamount of basaltic rockand then accreted to the terrigenous sediments of the Permian Tsunemori Formation


at the end of the Middle Permian.

The following palaeontological and geological contributions are important forestablishment of the biostratigraphy and comprehension of the accretionary processof the Akiyoshi Limestone Group: Fujii (1972); Fujii and Mikami (1970); Haikawa(1986, 1988); Haikawa and M. Ota (1978, 1983); Hasegawa (1967); Hashimoto(1979); Ichikawa (1984, 1990); Kawano (1960); Kimura, Hayami and Yoshida(1991); Matsusue (1986, 1988); Miura (1987); Nakamura and M. Ota (1974);Nishida (1971); Nishida and Kyuma (1982, 1984); M. Ota (1971); M. Ota,Toriyama, Sugimura and Haikawa (1973); N. Ota, Sugimura and M. Ota (1969);

Sakagami (1964a, b); Sakagami and Sugimura (1978, 1983); Sano, Iijima andHattori (1987); Sano and Kanmera (1991a, b, c, d); Sugimura (1972, 1974, 1985);Sugimura and M. Ota (1971, 1980); Sugiyama (1984); Uchiyama, Sano andKanmera (1986); Ueno (1991a, b, c); Yanagida (1962, 1965, 1968, 1973, 1979,

1983); Yanagida, M. Ota and Nagai (1977); Yamagiwa and M. Ota (1963).

-II. Middle Carboniferous to Lower Permian biostratigraphic units in theAkiyoshi Limestone Group

The fusulinacean biostratigraphy of the Akiyoshi Limestone Group has beentreated as a standard of the Japanese Carboniferous and Permian. Recently, thechronostratigraphic units of the Middle Carboniferous and Lower Permian have beenvery often discussed in the world to confirm the exact boundary between the Carbon

iferous and Permian. The Middle Carboniferous to Lower Permian biostratigraphic

units in the Akiyoshi Limestone Group also have been discussed by many workers,such as, Ozawa (1923), Kobayashi (1935, 1941), Sugiyama (1939), Toriyama

(1954a, b), Hasegawa (1958, 1963, 1988), Murata (1961), M. Ota (1968, 1977),

Ueno (1989), Ishii (1990), Ozawa and Kobayashi (1990), Watanabe (1991), and

Y. Ota and M. Ota (1993).

In case of the Akiyoshi region, it is well known that the Akiyoshi Limestone

Group was formed as an organic reef complex and that there is a great variation in

the biofacies and lithofacies. Consequently, in the Akiyoshi Limestone, the fusulinacean assemblages of the same age often show different constituents with different typesof the limestone, suggesting different paleoenvironments (M. Ota, 1977). Therefore,it is indispensable to carefully discern the paleoenvironment in the Akiyoshi organicreef complex to establish the standard fusulinacean zones in the Akiyoshi Limestone

Group. A number of stratigraphic units of the same age with different leading fossils

are known in the Akiyoshi Limestone Group. It is understood that the complicatedstate of zonation might be caused by differences of the original habitats of biota in the

organic reef complex. For instance, Ozawa and Kobayashi (1990) proposed 47fossil zones in the Akiyoshi Limestone Group. However, these zones are generally

not mappable and some fossils are not included in these zones (e.g. Sugiyama andHaikawa, 1993). These finely distinguished zones, appear to be reasonable, how-

6 Yasuhiro Ota

ever they are sometimes not practical. A careful examination of the lateral and

vertical distributions and transitions in the biofacies and lithofacies is required so asnot to disregard the original habitats of biota in the various types of limestones.Watanabe (1991) discussed the inflated schwagerinids and proposed some phylogenetic lineages and datum levels among them. His proposals are very interestingand logical. The inflated schwagerinids are well known in world wide distribution.Therefore they are very useful for international correlation. For establishing thechronostratigraphic units, the reconstruction of the evolutionary trend of the inflatedschwagerinids is indispensable. On the other hand, the inflated schwagerinids arealso known to occur in specialized environments of deposition, that show apparentlyimbalanced distribution of them, near the Carboniferous and Permian boundary(Ross, 1964). Therefore, special attention and examination of the constituents of theinflated schwagerinids are essential to establish the standard of both logical andpractical chronostratigraphic units in the local area. Details of examination and

comparison of the biostratigraphic units are discussed in the following chapters.

Research on the chronostratigraphic units near theCarboniferous-Permian boundary

The chronostratigraphic divisions of the Carboniferous and Permian have beendiscussed for many years in and outside Japan. The definition of the Carboniferous-Permian boundary has received special attention. As the Carboniferous-Permianboundary is an intersystem boundary, defining the boundary means to establish the

datum position in the rock sequences and this is essential for worldwide correlation.

The name Carboniferous was derived from the coal bearing beds (Coal Measures) in England, whereas that of the Permian originated from the region of Perm,Russia. The Upper Carboniferous in England is mainly composed of terrigenoussediments. The Lower Permian in Russia, on the other hand, mainly comprises marine sediments. Therefore, it is not easy to confirm the boundary between the Car

boniferous and Permian and to make intercontinental correlations of the UpperCarboniferous to Lower Permian successions. In general the Carboniferous-Permian boundary is defined by marine sediments and fossils, which should be effective

for the world wide correlation. From historical view points, the boundary should be

defined in Russia. However, the Carboniferous and Permian boundary has been left

ambiguously even in the type area. Therefore, it is true that many workers continue

to apply their own definition.

Here, careful considerations are summarized in three cases, relating to the

boundary problems.

(1). The first case is the incompatibility caused by treating the stratigraphicboundary as the chronostratigraphic boundary. This consideration has resultedfrom regarding faunal elements of different ages as being of the same age.


(2). The second case is the confusion caused by applying the personal definition of each worker for the Carboniferous and Permian boundary even in Russia.This trouble is also due to a key fossil which was chosen for defining the Carboniferous-Permian boundary in spite of the inexact state of its taxonomic position.

(3). The third case is shown by applying the evolutionary stage of a fossil fordefining the boundary. There are also some problems, because it is difficult to confirm the key fossil for defining the Carboniferous-Permian boundary.

As mentioned above, each case includes complicated and unsolved problems,and arguments about the definition of the Carboniferous-Permian boundary havecontinued since Murchison first introduced the Permian in 1841.

Some proposals are introduced as follows.According to Rauser and Shchegolev (1979), the Carboniferous-Permian

boundary has been studied intensively since Murchison, and the highest stratigraphic unit in the Carboniferous, namely, the top of "Schwagerina" Horizon waswidely recognized as marking of the Carboniferous-Permian boundary. However,after the Asselian Stage was established by Ruzhencev, some paleontologists arguedthat the Carboniferous-Permian boundary should lie at the base of the Asselian,namely, at the baseof the "Schwagerina" Horizon. Definitions of the boundary of theCarboniferous and Permian boundary have been summarized as follows.

1. Put the boundary between the Carboniferous and Permian at the base of theDaixina sokensis Zone of the Gzhelian.

2. Make the base of the Asselian the boundary between the Carboniferous and

Permian.

3. Put the boundary at the base of the upper fusulinacean zone in the Asselian,(the base of Nenetsky Horizon).

4. Place the boundary at the top of the Asselian (Table 1).Rui and Zhang (1987) summarized the Carboniferous-Permian boundary in the

world. According to them, six proposals for the Carboniferous-Permian boundarywere shown even in Russia as follows.

1. The Carboniferous-Permian boundary is at the base of the Daixina sokensis

Zone in the upper part of the Gzhelian Stage.2. The base of the Daixina bosbylauensis-Daixina robusla Zone is the Car

boniferous-Permian boundary.

3. The basal part of the Asselian Stage in Russia, namely, the Schwagerinavulgaris-Schwagerina fusiformis Zone is the lowest part of the Permian.

4. The basal part of the Schwagerina sphaerica-Pseudofusulina firma Zone of theupper part of the Asselian, namely, the lowest part of the Nenet Horizon is the lowestpart of the Permian.

5. The Carboniferous-Permian boundary is between the top of the Asselian andthe base of the Sakmarian, namely, between the Schwagerina sphaerica-Pseudofusulina

firma Zone and the Pseudofusulina moelleri-Pseudofusulina uralica Zone.

Yasuhiro Ota

Table 1. Correlation of the Carboniferous and Permian boundary among the main provinces (after Rauser and Shcheoolev, 1979).

Russian

Platform &Ural

Zone

m

Hinilft

ii

CamlcAlps

USA

W.Texas NewMexfoo

Formation

Kuma

Zone

si1

l!C3

6. The Carboniferous-Permian boundary is at the boundary between theArtinskian and Sakmarian (Table 2).

In USA Beede and Kniker (1924) considered that "Schwagerina" was a goodindex fossil and its earliest occurrence mightbe safely regarded as revealing the basalpart of the Permian. They proposed that "the zone of Schwagerina" (=Pseudoschwagerina of modern usage) should be recognized as the base of the Permian. According to the Permian Subcommittee of the National Research Council's Committee

on Stratigraphy (Dunbar, Chairman) (1960), the U.S. Geological Survey officiallyrecognized the Permian as a system in 1941. But it was uncertain until 1951 wheth

er the Wolfcampian Series was "Permian". It is common that American geologistsusually put the base of the Pseudoschwagerina Zone as the base of the Permian. They

Fusulinacean Biostratigraphy of the Akiyoshi Limestone Group, Part I

Table 2. Different levels proposed for theCarboniferous-Permian boundary in Russia (afterRui and Zhang, 1987).

Official Carboniferous - Permian boundary in Russia(Russian Platformand Ural)

Horizon

Irgjn

Burtsyev

Styertttamak

Sokotiegor

Zone

Parafusulinalutugtni

Pseudofusulina ccncavutas

Pseudofusulina urdalensis

Pseudofusulina vemeuSi •Psf. uraBca

Pseudofusulina moeBeri

Schwagerina sphaerica -Pseudofusulina firma

Schwagerina moelleri•Pseudofusulina fecunda

Schwagerina vulgaris •SfusHbrmis

Daixina sokensis

JiguHtespgulensis

Rybakov. 1962Lurryak. 1962

Carboniferous

Lever), 1986

S. vulgaris.S. fusttcnnlsZ.Dah&iabosbyt&uoftslsD. robust* Z

Daixinasokensis Z.

Barkhatova,1970

£

NenetHorizon

Carboniferous

Raiser. 1960RertOnger.1969: Koar. 1884Movsrtovich. 1S66

Psf.moeBeri Z.

Carboniferous

Ruzherchev

andSarycheva,196S

Permian

Carboniferous

have the opinion that the base of the Permian in the U.S. is essentially equivalentto the same horizon of the Russia (Fig. 2). Ross (1984) summarized Carboniferous-Permian fusulinaceans of North America and concluded that the base of theAsselian in the Russian type locality, namely, the base of the zone with large, inflatedschwagerinids, was presently widely recognized as the base of the lowest Permianfaunal zone by many invertebrate paleontologists in North America, Japan and southern Europe. Wilde (1984) also published on the Carboniferous-Permian boundaryand he discussed this problem from the viewpoint of fusulinacean taxonomy. Healso remarked that the Carboniferous-Permian boundary had been drawn at the baseof the Asselian Stage in Russia. In addition, he recognized the boundary as equivalent to the middle Wolfcampian unconformity, identified in the type section of theWolfcampian in the United States (Figs. 3, 4).

In China, Rui and Zhang (1987) reviewed the current situations of the Carboniferous-Permian boundary. According to them, before 1970, Chinese workerstraditionally regarded the top of the Pseudoschwagerina Zone in the Maping (Chuan-shan) Formation as the upper most of the Carboniferous, and the lower part of theChihsia Formation, namely, the Schwagerina tschernyschewi Zone or the MisellinaSubzone of the Parafusulina Zone as the lower most of the Permian. In 1981, Rui Linfound the "Carboniferous" (traditional Chinese sense)-Permian mixed fusulinacean

10 Yasuhiro Ota

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fauna in the section of the "Carboniferous" to Permian continuous sediments above

the uppermost Pseudoschwagerina Zone or the Robustoschwagerina schellwieni Zone ofPermian age. This sequence seems to represent the Liangshan Member, and Ruiadvocated that the lower boundary of the Permian should be placed below thislimestone sequence. Afterwards, some workers supplemented and revised thedefinition on the traditional boundary. At present 18 main proposals for theChinese Carboniferous-Permian boundary are known (Rui and Zhang, 1987).These Chinese proposals have been continuously discussed and they are put into sixmain opinions about the definition of the Carboniferous-Permian boundary (Table3).

1. Putting the boundary between the Carboniferous and Permian at the top ofSchwagerina Zone, is known as the traditional boundary in China and used for morethan 40 years. In short, the boundary is compared with the top of the Pseudoschwagerina Zone or the Sphaeroschwagerina Zone, namely the top of the MapingFormation or the Chuanshan Formation, correlated with the boundary between the

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12 Yasuhiro Ota

4. Possible alternate correlation offusulinid zones, Russia-USA (after Wilde, 1984).

Asselian and Sakmarian Stages.

2. The Carboniferous-Permian boundary should be drawn at the base of thePseudoschwagerina morsei- Robustoschwagerina xiaodushanica Zone, namely, the lowermostpart of the Mapingian, characterized by the first appearance of the rapidly evolvingpseudoschwagerinids (Zhou et ai, 1987, Fig.5).

3. The base of the Montiparus Zone is regarded as the lowest part of thePermian. The Montiparus Zone is characterized by the first appearance of thekeriotheca in the wall microstructure (Zhang, 1984, Figs. 6, 7).

4. The Carboniferous-Permian boundary should be placed between the LateCarboniferous Nephelophyllum-Pseudotimania assemblage Zone and the Early PermianKepingophyllum assemblage Zone, namely between the Shazitang Formation and theLongyin Formation of the Longyin section in Guizhou. However, Rui and Zhang(1987) noticed that the lowest part ofthe Kepingophyllum assemblage Zone was higherthan the base of the Pseudoschwagerina Zone.

5. The lowest part of the Pseudofusulina moelleri Zone and the ProtopopanocerasZone in the Longyin section of Guizhou, is correlated with the lowest Sakmarian inRussia and it is regarded as the lowest of the Permian. According to Ruiand Zhang(1987), this consideration of the Carboniferous and Permian boundary is ambiguous,because the Pseudofusulina moelleri Zone contains Sphaeroschwagerina and other characteristic elements of the Asselian Stage.


Table 3. Different levels proposed to the Carboniferous-Permian boundary in China (afterRui and Zhang, 1987).

13

Locality Lower Permian Upper Carboniferous

Nanjing MisChen, 1934,Sheng.1962

Swine Limestone Member Chuanshan FraMdaudaeZ 1 S. tschemyschewi Z PseudoschwaaerinaZ 1 TriMesZ

Chinling RangeWang etaL 1973

YaziFra SanBchongFm.MiseSlmaZ. PamuinaZ PseudoschwacsrhaZ 1 TriMesZ

Nanjing hitsWang,1978

L Permian Upper CarbonSerous

Swine L Mem. ChuanshanFm.

M. daudae Z .Sphaeroschwagerina moelleri Z 1 TriMesZ

Puan,GuizhouWuetal., 1979Yangel al.,1983

Lower Permian Upper CarbonSerous

ChBisia Fm. LiangshanFra Baomoshan Fra Longyin Fra I Shazitang Fm.Robust,

schellwieniZSphaeroschwagerina Z

Triticites ZSph. domerosa ISph. constans

SouthernJiangYu.1981

Lower Permian" UpperCarboniferousChhsiaFm. ChuanshanFm.

Parawenl Z 1Chuanshan. Z 1Yangzistratigraphic provinceRui,1981

Chftsia Stage MapingStage

Misellina Z PseudoschwaaerinaZ. 1 TriMesZSouth China

Sheng., 1982ChBisia Stage Maping Stage

M. daudaeZ 1Schwagerina tschemyschewi Z Pseudosc wagerina Z I Triticites Z

Puan,GuizhouZhang, el al, 1982

Lower Permian Upper CarboniferousChihsia Stage Longyin Fm Shazitang Fra

MiseSna daudae Zone Pseudofusulna moelleri Zone Ps-ZelliaZ TriMesZ

Longlin, GuangaLong, 1982

ChBisia Fra ChannmoFra Mapina FmMisellina,Paratusulina

Pseudofusul'ina inusilata-Robustoschwagerina Z Pseudoschwagerina Z TriMesZ

Longlin, GuangxiHuang, 1984

ChihsiaFm. LortfinStaae Maping Stage

Misellina Z Pamtina- Nagatoella {Daivasies Pseudoschwagerina Z | Triticites Z

Southern HunanZhou, 1982

ChBisia F. Chuanshan Fm

M. daudaeZ Staffollal S.cushmaniZ Pseudoschwagerina Z

Nanjing hBisZhang, 1983

ChBisia Fra Swine Limestone Fm. Chuanshan Fra

M. daudae Z Darvasites oidinatus Z Sphaeroschwagerina moelleri Z Triticites Z

Southwestern Guizhou

Wuetal., 1983

Proposal 1 Lower Permian U.Carb.

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Proposal 2 Lower Permian U.Carb.

Puan,GuizhouZhang, 1983

Lower Permian UpperCarboniferousChBisia Fm. Uanoshan Fm. Baomoshan Fm Longyin Fm. | Shazitang Fm.

Rob.

schellwieni ZSphmoschwaaerina Z.

Triticites ZSph. domerosa\ Sph. constans

Qinling RangeDing etal., 1983

Lower Permian UpperCarbonSerousYaziFra <* SanBchongFm.

M.daudae I <£ Shaa.Robustoschwagerina, Sphaeroschwagerina Triticites

South China

Wu, etal., 1984

Lower Permian Upper CarboniferousChBisia Fm. Liangshan Fra | Baomoshan Fra| Longyin Fm. Shazitang Fm.

M daudae Z Kepingophyllum Assemblage =(P& Z.) Triticites Z

South China

Zhang, 1985

Permian

T.Z M.Z

Luodan, GuizhouXiong etal, 1985

Lower Permian Upper CarboniferousChihsiaFm. Nashui Fm. MapingFra

MisellinaPamirina ZSwoetognathuswhiteiZ

Sphaeroschwagerina,Pseudoschwagerina Triticites

14

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Yasuhiro Ota

1. Protriticites subschwagerinoides Zone2. Triticites montiparus Zone3. Triticites schwageriniformis Zone4. Triticites dictyophorvs Zone5. Triticites shikhanensis compactus Zone6. fteudaschwagerina mo/sej -

Robustoschwagerina xiaodushanica Zone7. fteudoschwagerina parabeedei -

Sphaeroschwagerina sphaerica Zone8. fteudoschwagerina robusta -

Zellia chengkungensis Zone9. Pseudofusulina vulgaris -

laxifusulina iniqua zone10. Chalaroschwagerina tumentis Zone11. Pamirinachinlingensis Zone

Fig. 5. Composite stratigraphic section, showing fusulinacean faunas near the Carboniferous-Permian boundary at Xiaodushan, Guangnan, Easter Yunnan (after Zhou et al.,1987).

6. The top of the Baomoshan Formation, namely the Robustoschwagerina Zone iscorrelated with the base of Artinskian Stage and it is regarded as the lowest part ofthe Permian in China.

In Japan, the definition of the Carboniferous-Permian boundary also has beendiscussed for a long time in several important provinces by many workers. Theauthor presents some recent considerations on this problem, by some workers in theAkiyoshi Limestone Group.

Toriyama (1954a, b, 1958) divided the Akiyoshi Limestone Group into thefollowing seven fusulinacean zones in descending order.

Yabeina Zone

Neoschwagerina ZoneParafusulina Zone

Pseudoschwagerina ZoneFusulinella Zone

Projusulinella Zone

Millerella Zone

He subdivided the Pseudoschwagerina Zone into two subzones, the upper, thePseudofusulina vulgaris Subzone and the lower, the Triticites simplex Subzone. Then

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Yasuhiro Ota

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The second session ofstratigraphic conference

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Fig. 8. The fusulinacean zones of the Akiyoshi Limestone Group (after Toriyama, 1958).

17

18 Yasuhiro Ota

he correlated the base of Pseudoschwagerina Zone (including Triticites simplex Sub-zone) with the base of Sakmarian in Russia, Wolfcampian in North America andSakamotozawan in Japan (Fig. 8).

Hasegawa (1958, 1963) divided the Akiyoshi limestone Group into eight zones.Of them, Profusulinella, Fusulina-Fusulinella and Yabeina-Lepidolina Zones were almostthe same as those by Toriyama (1954a, b, 1958), but he subdivided PseudoschwagerinaZone into an upper, the Pseudoschwagerina muongthensis Subzone and a lower, theTriticites simplex Subzone. At that time, he did not clearly indicate the Carbonifer

ous-Permian boundary. However, he noticed the Mg-rich and oolitic limestones in

the lower part of Pseudoschwagerina Zone.Murata (1961) divided the Akiyoshi Limestone Group into eight foraminiferal

zones. He put the Carboniferous-Permian boundary below the base of the Pseudo

schwagerina Zone, where the subfamily, Schwagerininae first appeared, and the

genera, Fusulinella, Fusulina and Beedeina disappeared.M. Ota (1968, 1977) established 21 fossil zones (Table 4). He considered the

Carboniferous-Permian boundary below the Triticites simplex Zone.

Minato, Kato, Nakamura, Niikawa and Hasegawa (1984) gave a review on

studies of the Carboniferous-Permian boundary in Japan and mentioned that the

Table 4. Biostratigraphic zones of the Akiyoshi Limestone Group (after M. Ota, 1977).

Geologic age Name of the fossil zone Symbol Thickness

Late Lepldollna multiseptata shlraiwensis Zone Puo +25m

CCO

E

Middle

Colania douvillei Zone

Verbeekina verbeekl Zone

Neoschwagerina craticullfera Zone

Afghanellaschenckl Zone

Parafusulina kaerimlzensis Zone

PmS

Pm y

PmjS

Pma2

Pma1

40m

20m

25m

15m

25m

Q_Early

Misellina daudiae Zone

Pseudofusulina ambigua Zone

Pseudofusulina vulgaris ZonePseudoschwagerina (P.) muongthensis Zone

Triticites simplex Zone

PIS

Ply

PI/5

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20m

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20m

±50m

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CO

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Beedeina akiyoshiensis Zone

Fusulinella biconica Zone

Akiyoshiella ozawal Zone

Profusulinella beppensis Zone

Pseudostaftella antiqua Zone

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Nagatophyllum satol Zone

Zahrentoldes sp. Zone

Marginalia toriyama! Zone

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70m

40m

80m


relationship between the Lower Permian and Carboniferous deposits in Japan isvariable from place to place (Fig. 9).

Ozawa and Kobayashi (1990) reexamined the fusulinacean zones of theAkiyoshi Limestone Group, and drew the Carboniferous-Permian boundary betweenthe Daixina robusta-"Pseudoschwagerina" minatoi Zone and the "Sphaeroschwagerina" fusi-formis Zone. Ozawa, Kobayashi and Watanabe (1990) established the new genus"Carbonoschwagerina" with Pseudoschwagerina morikawai Igo as the type species. Theyremarked that this genus represents Carboniferous age. They placed the Carboniferous-Permian boundary at the same horizon as Ozawa and Kobayashi (1990).Watanabe (1991) emphasized the same opinion that the Carboniferous-Permianboundary should be placed under the Sphaeroschwagerina fusiformis Zone.

Fig. 9. Correlation of the Upper Carboniferous and the Lower Permian in Japan (afterMinato et al., 1984).

Biostratigraphy of the Akiyoshi Limestone Group near the Carboniferous-Permian boundary in the three different areas

-1-1. Biostratigraphy of the Jigoku-dani area

The first area investigated, Jigoku-dani, is located in the northwestern of the

Akiyoshi Plateau(s. s.). This area topographically consists of a deep valley with NE-

20 Yasuhiro Ota

SW trend, ranging from about 200 m to 350 m in altitude and well-developed karsttopography. M. Ota (1977) confirmed the following fusulinacean zones in this area:

Fusulinella biconica Zone, Triticites simplex Zone, Pseudofusulina vulgaris Zone and

Pseudofusulina ambigua Zone. The Akiyoshi Limestone Group in this area is consid

ered to have originally accumulated in a lagoonal sedimentary environment within

the Akiyoshi organic reef complex and is geologically inverted in structure. However, in this area, fusulinacean zones such as the Beedeina akiyoshiensis Zone, Triticites(s. 1.) matsumotoi Zone, and Pseudoschwagerina muongthensis Zone of the generalized

fusulinacean zones of the Akiyoshi Limestone Group (M. Ota, 1977) have not beenconfirmed yet and elements of the fusulinacean fauna have remained unknown.

Topography of the Jigoku-dani area is characterized by the limestone lapie fieldand it is difficult to confirm the exact localities of the collected materials. Therefore,

the author selected some traverses to measure with the name ofJI (JI Traverse 1-5)

and collected materials along the traverses. Materials from localities 300 to 788 aremainly discussed here (Fig. 10).

Limestones in the Jigoku-dani area are generally massive. They are white to

gray white, but pardy dark brown in color. The dark brown color is considered tobe caused by the secondary alteration, but the genesis needs to be carefully studied.The limestones in this area are ordinarily composed of micrite, with some intercalating limestone with sparry calcite cements. Frame building organisms of reef environment are almost absent. These features suggest that the limestones in theJigoku-dani area were mostly accumulated under a low energy lagoon sedimentary

environment.

Based on the microscopic study of the collected specimens, 56 fusulinacean species including two subspecies among 23 genera are discriminated (Table 5). Distribution of these fusuhnaceans and distinction of lithofacies are illustrated in Fig. 11.

Distribution of the characteristic fusuhnaceans and the fusulinacean zones along five

traverses, JI Traverse 1-5 are shown in Fig. 12. Furthermore, the detailed distribution of the fusulinacean species and the lithofacies along each traverse are shown inFigs. 13 and 14, respectively.

From these examinations, nine zones including seven subzones were recognizedin the Jigoku-dani area (Table 6). The representative fusuhnaceans of the proposedzones and the thickness of each zone measured along each traverse are shown in

Table 7.

From the distribution of these fusulinacean zones, it is confirmed that the

Akiyoshi Limestone Group in this area has the general strike of N10°W, dipping toward SW with angles of 10 to 20 degrees. Furthermore, the older fusulinacean zonesare recognizable at higher topographical locations than the younger ones along thewestern slope of the valley, and therefore limestones in this area apparently exhibit aninverted succession. In addition, these limestones are mainly composed of micritewithout the frame builders of organic reefs. They are considered to have accumu-

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Fig. 12. Distribution of the characteristic fusulinacean species (shown by the locality numbers) andthe fusulinacean zones (1-9) along the JI Traverse 1-5.The following numbers are used for fusulinacean zones: 1. Fusulinella biconica Zone; 2. Fusulina cf.shikokuensis Zone; 3. Obsoletes obsoletus Zone; 4. Montiparus sp. A Zone; 5. Triticites yayamadakensisZone; 6. Schwagerina (?) cf. satoi Zone; 7. Pseudoschwagerina muongthensis Zone; 8. Pseudofusulinavulgaris globosa Zone; 9. Pseudofusulina aff. ambigua Zone. The characteristic fusuhnaceans withlocalities are as follows: 332, Pseudoschwagerina muongthensis (Deprat); 387, Schwagerina (?) cf. satoi(Ozawa); 392, 439, 569, 605, Triticites yayamadakensis Kanmera; 454, 554, Montiparus (?) sp. A;461, Fusulinella biconica (Hayasaka); 465, Fusulinella cf. obesa Sheng; 468, Protriticites toriyamaiOta; 477, 633, Obsoletes obsoletus (Schellwien); 489, 538, Protriticites matsumotoi (Kanmera); 517,Pseudofiisulinella hidaensis (Kanuma); 520, Protriticites masamichii Ota; 578, Schwagerina sp. A; 663,Montiparus sp. A; 686, Triticites yayamadakensis evectus Kanmera; 723, Pseudofusulina (?) sp. A; 729,Pseudoschwagerina sp.; 736, Paraschwagerina sp.; 766, Pseudofusulina aff. ambigua (Deprat).

26

Fig. 13-1. JI Traverse 1.

Yasuhiro Ota

13. Distribution of the characteristic fusulinacean

species (shown by the locality numbers) and thefusulinacean zones (1-9) along the JI Traverse 1-5.

The following numbers are used for fusulinacean

zones: 1. Fusulinella biconica Zone; 2. Fusulina cf.

shikokuensis Zone; 3. Obsoletes obsoletus Zone; 4. Monti

parus sp. A Zone; 5. Triticites yayamadakensis Zone; 6.Schwagerina (?) cf. satoi Zone; 7. Pseudoschwagerinamuongthensis Zone; 8. Pseudofusulina vulgaris globosaZone; 9. Pseudofusulina a(T. ambigua Zone.

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306

V-'

"31?sir

316

317

319

21 :••:•:••: :

322

323

324

325

37-i

—28~'•::.••

3X

534"

6

;.;....

311

313

318

360 •~~

y.i

361~ss~

354

~356—

—370

375376

375"383 -

-%:•-

Fig. !•!. Distribution of lithofacies along the JI Traverse 1-5.The following numbers arc used for fusulinacean zones: 1. Fusulinella biconica Zone, 2.Fusulina cf. shikokuensis Zone: 2-1. Fusulina cf. obesaSubzone, 2-2. Pseudofusulinella hidaensis

Subzone, 3. Obsoletes obsoletus Zone: 3-1. Protriticites loriyamai Subzone, 3-2. Protriticitesmatsumotoi Subzone, 4. Montiparus sp. A Zone, 5. Triticites yayamadakensis Zone: 5-1.Triticites saurini Subzone, 5-2. Schwagerina sp. A Subzone, 5-3. Triticites biconkus Subzone,6. Schwagerina (?) cf. satoi Zone, 7. Pseudoschwagerina muongthensis Zone, 8. Pseudofusulinavulgaris globosa Zone, 9. Pseudofusulina aff. ambigua Zone.

Fusulinacean Biostratigraphy of the Akiyoshi Limestone Group. Part I 29

Locally

L rrescne

withrriaitematrix

.. rrestc-e

withrrtcriticmatrix

Limestonewithsparrycatate

cerrent

Black anddarkbrowncolor

Imestone

Subzone Zone

4

.

564 | wmm553

561

560 :- ,,,,7,7,",',",",.,559 "••«.••••—

555 l

3-2

3

1

:•:•:•: :-

3-1

2-2

2

2-1

1

Fig. 14-3. JI Traverse 3 (Loc. 509 to Loc.568. left column).

Locality

Limestonewithrriaitematrrx

Limestonewith

micriticmatrix

Limestonewithsparrycalatecerrent

Back anddarkbrawn

colorirrestone

Subzone Zone

34/4

4/3. .

4/2

4/1

4/0

2

i

Fig. 14-2. JI Traverse 2 (Loc. 464 to Loc.

479, left column).

Locally

Lirrestonewithrriaitematrix

Limestonewithrriaiticmatrix

Linesonewithsparrycalate

cement

Backano

darkbrowncolor

Imestone

Subzone Zone

5-3

5

615

613

607

605

5-2

603

601

595

585.

5/9

578

5//

5-1

576 • : ::••:•:•

5/5 • : ::-:-:::-:-:57; :•:::.

570

559

Fig. 11-3. JI Traverse 3 (Loc. 569 to Loc.

616, right column). Loc. 568 (upper

most of the left column) continues to Loc.

569 (lowest of the right column).

Locally

Lirrestone

withrriaitematrrx

Lirrestonewithrriaitic

matrix

Lirrestonewithsparrycalatecement

Biackanddarkbrowncolorrrestrjr.e

Subzone Zone

3

•:.-:•:-•.-:•-:•:

.:•:::•::

483

2-2

2

2-1

•••: •

459iX

506507

Fig. 14-2. JI Traverse 2 (Loc. 507 to Loc.•180, right column).

30 Yasuhiro Ota

Locally

jrreacne

with

rriaitematrix

Limestonewith

micrrticmatrix

Limestonewithsparrycaldte

cerrent

Biackanddarkbrowncolorlimestone

Subzone Zone

5

h;

7a

705704

—

698 • •:•••:•-: "

•:•:-•:•:•:••:•. •

" W

685

4

684

•:.-3

690

679678

669

-••:•:• •: •

™

665

664

663

662

32

3

661

660 •: ::•:•:• • •:•

659• ••:•.-.. .,• ..

657 .?••.-•••••••;,655 ..:•:•: .

•:•:•::•.•:•:• . •

615648 •:•:••:-:•:••:•:•••:••:•

643 .:•••:•.•

642611

616

638

63/

6a 3-1:'.'

222

631

630

659

(27

£5

6202-1

6181

Fig. 11—1. JI Traverse 4 (Loc. 617 to Loc.

712).

Locality

Lirrestone

withrriaitematrix

Lirrestonewithmicriticmatiix

Limestone

withsparrycaloriecerrent

Bac.K ar,adarkbrown

colorlimestone

Subzone Zone

«

9

",

771

8

763

/60

756

7731

6

726

725

5

/14

Fig. 14—5. JI Traverse 5 (Loc. 713 to Loc.

788).


Table 6. Fusulinacean zones in ascending order recognized inthe Jigoku-dani area.

Fusulinacean zones in the Jigoku-dani area

9. Pseudofusulina aff. ambigua Zone

8. Pseudofusulina vulgaris globosa Zone

7. Pseudoschwagerina muongthensis Zone

6. Schwagerina (?) cf. satori Zone

5. Triticites yayamadakensis Zone

5-3. Triticites biconicus Subzone

5-2. Schwagerina sp. A Subzone

5-1. Triticites saurini Subzone

4. Montiparus sp. A Zone

3. Obsoletes obsoletus Zone

3-2. Protriticites matsumotoi Subzone

3-1. Protriticites loriyamai Subzone

2. Fusulina cf. shikokuensis Zone

2-2. Pseudofusulinella hidaensis Subzone

2-1. Fusulinella cf. obesa Subzone

1. Fusulinella biconica Zone

lated in a relatively low energy lagoon environment within the Akiyoshi organic reefcomplex. Distributions of fusulinacean zones are shown in Fig. 15 and the crosssections along A-A', B-B' and C-C, are respectively indicated in Fig. 16.

The detailed characters of each fusulinacean zone are given as follows.1. Fusulinella biconica Zone.

The Fusulinella biconica Zone is the oldest in the Jigoku-dani area and is exposed

in the highest part of the western slope of this area. The thickness is estimated to beabout 2 m + . This zone is typified by the occurrence of Fusulinella biconica (Hayasa-

ka). Limestones have a general NE strike and dip gently to northwest, but occasionally dip toward the southeast. They are mainly composed of micritic limestoneswith intercalation of limestones with sparry calcite cements.


The Fusulina cf. shikokuensis Zone conformably overlies the Fusulinella biconica Zoneand is defined by the occurrence of Fusulina cf. shikokuensis Ishii. This zone issubdivided into two subzones, the lower, the Fusulinella cf. obesa Subzone and the

upper, the Pseudofusulinella hidaensis Subzone.

2-1. Fusulinella cf. obesa Subzone.

The Fusulinella cf. obesa Subzone is characterized by the occurrences of Fusulinellacf. obesa Sheng in association with Fusulinella cf. shikokuensis Ishii. Limestones of this

Tab

le7.

Rep

rese

ntat

ive

fusu

hnac

eans

inth

epr

opos

edzo

nes

and

the

thic

knes

sof

each

zone

mea

sure

dal

ong

the

surv

eyed

trav

erse

s.

Rep

rese

nta

tive

fusu

hn

ace

an

so

fea

chzo

ne

inth

eJi

go

ku-d

an

ia

rea

Th

ickn

ess

9.P

seu

do

fusu

lin

aa

ff.

am

big

ua

Zo

ne

Ji

Ro

ute

1Ji

Ro

ute

3JI

Ro

ute

3Ji

Ro

ute

4Ji

Ro

ute

6

Pse

udof

usul

ina

aff.

amd&

ua[7

66(1

6)],

Psf

.cf.

vulg

aris

b.b.

[766

(6)]

.4

2+

m,

(76

6-7

88

)

8.P

seu

do

fusu

lin

avu

lga

ris

glo

bo

saZ

on

eP

seud

ofus

ulin

avu

lgar

isgl

obos

a[7

38d>

2,75

5(l)

-3,

763(

2>-3

],P

ara

sch

wa

ger

ina

spp

.[7

86

(2),

75

6(2

),7

56

(8).

75

9(1

)-1

].

83

m,

(73

6-7

66

)

7.P

seu

do

sch

ua

ger

lna

mu

on

gth

ensi

sZ

on

eSt

affe

Uam

oelle

ri,S

chub

erte

ttaki

ngi,

Schw

ager

inao

kafu

JiiT

.S12

o.-2

],S.

prim

igen

a[31

3f\,

S.cf

.prt

ncef

w[3

12fj

,5.

sp.

A[3

S2(2

e>7]

,S.

sp.

B[S

32D

2],

S.sp

.C[3

11a,

317D

],5.

sp.D

[382

b-1]

,S.

(7)a

ff.A

u«fc

«ft«

wfa

[S08

c-l)

,P

seu

dosc

hw

ager

lnam

uon

gth

ensi

sVlS

Uli

-l,

33

2(l

a)-

3],

Ps.

sp.[

729(

1)1.

Ps.

(7)

sp.[

800d

-b].

32

+m

,(3

32

-30

0)

17

m,

(72

9-7

36

)

6.S

chw

ag

erin

a(?

)of

.sa

toi

Zo

ne

Oza

wai

nel

laof

f.m

agna

,N

anki

neU

asp

.A

Seh

ube

rtel

lala

ta,

Tri

ticite

sha

yder

uT37

9d],

7.m

ich

iae[

379p

],7.

cf.o

6ai[

S78d

-2?]

,7.

cf.p

seud

osim

plex

[311

B.-2

,72

5(1)

],7.

aff.

stoy

rf«:

[379

c-l]

,7.

aff.

ai»u

Aii

[37S

a-l]

,Sc

hwag

erin

acf

.«to

&ai

s[83

6a-2

,S86

e,33

6d],

S.(?

)cf.

«ato

i[38

7d2]

,"P

seud

ofus

ulin

a"

cf.

oacc

a[33

6b-3

],'P

sf.'

aff

./i

wfb

nni»

[879

1-2]

Psf

.(?

)sp

.A

[360

a,3

87

c-A

723]

,R

wo

sofu

3u

lin

aa

rcli

calS

4B

a-l

,3

54

a-2

].

76

m,

(38

7-3

32

)1

1m

,(7

23

-72

9)

5.T

riti

cit

es

yaya

ma

da

ken

sis

Zo

ne

5-8

.T

rit

icit

es

oic

on

lcu

ssu

bzo

ne

Qua

sifu

sulln

asp

.B[8

90c-

1,61

4(1)

],T

ritic

itesb

icon

icw

>[39

2b-l,

392b

-2],

7.cf

.iso

«nji5

[608

d],

7.A

uroJ

u>a*

/uM

392a

-2],

7.ya

yam

ad

ak

ensi

s[3

92

a-3

.S

92

A-1

.6

05

b-l

l.

15

m,

(39

2-3

87

)3

2+

m,

(60

5-6

16

)

72

m,

(68

6-7

23

)

5-2.

Sch

wa

ger

ina

sp.

Asn

bxo

no

Tri

ticite

sbi

coni

cus,

7.af

f.si

mp/

«x(5

86d]

,7.

su«u

&f[

581c

-3],

7.ya

yam

adak

ensi

slB

Sl})

,S

chw

ag

erin

asp

.A

[57

8(6

).5

86

b-2

,5

86

i-l]

,5

.sp

.B

.1

09

m,

(43

9-3

92

)

43

m,

(57

8-6

05

)

5-1

.T

rit

icit

es

sa

urin

lsu

bzo

ne

Tri

tici

tes

cf.o

onus

[569

k],

7.h

iden

sisl

421e

.-l)

,7.

mfc

Ata

e[69

4-(4

)],

7.8a

uniu

T40

3a-3

,4

03

b,

42

9a

,42

9b,

433a

-l],

7.af

f.si

mpl

ex,T

.yay

amad

aken

sis[

489b

,56

9d],

7.ya

yam

adak

ensi

sev

ectu

s[6

94(1

8),5

69'(1

),68

6(1)

,6

87

(b)-

l].

15

m,

(56

9-5

78

)

4.M

on

tip

aru

ssp

.A

Zo

ne

Qua

sifu

sulin

alon

giss

ima[

675(

2),

675(

4>2]

,Q

uasi

fusu

lina

sp.A

(675

(3)]

,M

ontip

arus

sp.

A[6

63(l

),67

6(1)

,679

(1)]

,M

(?)

sp.

A[4

64

a.

554(

1)].

Tri

tici

tes

hid

ensi

s.7

.cf

.o

tai.

7.

sau

rtro

[67

3(8

)l.

34

m,

(45

4-4

39

)2

0m

,(5

54

-56

9)

24

m,

(66

3-6

86

)

3.

Ob

eo

Ute

eo

bso

letu

sZ

on

e3

-2.

Pro

trit

icit

es

ma

tsu

mo

toi

su

bzo

ne

Obs

olet

esob

sole

tus[

469a

7,63

7(b)

],P

rotr

itic

ites

mat

sum

otol

i4S

9c,

538a

,63

4(1)

],P

wt

yano

£Wai

[540

a],

Qu

asif

usu

lin

oide

s(?

)sp

.[6

39(1

)1.

9m

,(4

54

-47

7)

31

m,

(53

8-5

54

)1

4m

,(6

34

-66

3)

3-1.

Pro

frtf

iclt

eeto

riya

ma

lsu

bzo

ne

Ob

sole

tes

ob

sole

tus[

4T

la,

53

2a

.6

33

-1],

Pro

trit

icit

esm

asa

mic

hU

lBW

a),

Pro

tlo

riya

ma

i[4

68c]

.6

3m

,(5

20

-53

8)

lm,

(63

3-6

34

)

2.

Fu

su

lin

ao

f.sh

iko

ku

en

sis

Zo

ne

2-2.

Pse

udo

fusu

lin

ella

hid

aen

sis

sub

zon

eP

seu

dofu

suli

nel

lafc

dae/

w»[

492(

2)-2

,5

17

a.

517b

],F

usu

lin

act

.sh

ikok

uen

sis[

492&

-l,

492b

].

2m

(48

1-4

77

)

8m

,(4

65

-46

8)

44

+m

,(4

89

-50

7)

2m

,(5

17

-52

0)

2-1

.F

usu

lin

ell

ao

f.o

freso

su

bzo

ne

Fu

suli

na

ct.s

hik

oku

enst

s[62

U2)

],F

usu

lin

ella

cf.©

4e*a

[465

a,46

7a].

2.

Fu

su

lin

ell

ab

ico

nic

aZ

on

eF

usu

lin

ella

bico

nic

a[46

1a,

61

8a

-l].

2+

m,

(46

2-4

61

)

Fig.

15.

Dis

tribu

tion

offu

sulin

acea

nzo

nes

inth

eJig

oku-

dani

area

.Th

efo

llowi

ngnu

mbe

rsar

eus

edfo

rfu

sulin

acea

nzo

nes:

1.Fu

sulin

ella

bicon

icaZo

ne;

2.Fu

sulin

acf.

shiko

kuen

sisZo

ne;

3.Ob

solete

sobs

oletus

Zone

:1.

Mon

tipar

ussp

.A

Zone

;5.

Tritic

itesy

ayam

adak

ensis

Zone

;6.

Schw

ageri

na(?)

cf.M

toiZo

ne;

7.Ps

eudo

schwa

gerin

amu

ongth

ensis

Zone

;8.

Pseu

dofu

sulin

avu

lgaris

globo

saZo

ne;

9.Ps

eudo

fusu

lina

aff.

ambi

gua

Zon

e.

n

34

350m

300m

250m .

200mA

350m

300m

250m.

200m'

B

350m

300m

250m

200m

C

Yasuhiro Ota

5. Triticites yayamadakensis Zone

6. Schwagerina (?) cf. saroi Zone


8. Pseudofusulina

vulgaris globosa Zone

9. Pseudofusulina

aff. ambigua Zone

1. Fusulinella biconica Zone


J v' 3. Obsoletes obsoletus Zone

Montiparus sp. A Zone

1:1

£- S. Triticites yayamadakensis Zone

6. Schwagerina (?)t cf. satoi Zone


^ 3. Obsoletes obsoletus Zone

7. Pseudoschwagerina/ muongthensis Zone

1:1 a-

.4. Montiparus sp. A Zone

^ 5. Triticites yayamadakensis Zone

iiic

Fig. 16. Cross sections along A-A', B-B' and C-C in the Jigoku-dani area.


subzone strike N10°W, gently dipping toward southwest. They are composed ofmicritic constituents, but limestones with sparry calcite cements are intercalated atthe basal partofthis subzone. Additionally, limestones ofblack to dark brown coloroccur in this basal horizon, though the origin of the black to dark brown limestoneshas not been determined.

2-2. Pseudofusulinella hidaensis Subzone.The base of the Pseudofusulinella hidaensis Subzone is marked by the first occur

rence of Pseudofusulinella hidaensis (Kanuma) and this diagnostic species is associatedwith Fusulina cf. shikokuensis Ishii. Limestones of this subzone are estimated to be 2

m in thickness, and have a general NW strike and gentle dip toward the southwest.They are characterized by micrite, but are partly intercalated by limestones with thesparry calcite cements.

3. Obsoletes obsoletus Zone.

The diagnostic species of the Obsoletes obsoletus Zone is Obsoletes obsoletus (Schell-wien). In theJigoku-dani area, this zone is recognized as an interval from the horizon with the first occurrence of the genus Obsoletes or the genus Protriticites, to thehorizon with Montiparus (?) sp. A or Montiparus sp. A. It is subdivided into two sub-zones, the lower, the Protriticites toriyamai Subzone with primitive species of Protriticites,and the upper, the Protriticites matsumotoi Subzone characterized by Protriticites matsumotoi (Kanmera).

3-1. Protriticites toriyamai Subzone.In this subzone, primitive species of Protriticites, such as Protriticites toriyamai Ota

and Protriticites masamichii Ota, are associated with the diagnostic species, Obsoletesobsoletus (Schellwien). These primitive species of Protriticites are very important todetermine the upper limit of the Middle Carboniferous. This subzone was namedafter the characteristic occurrences of Protriticites toriyamai Ota. Maximum thicknessof this zone is estimated as 63 m. Limestones of this zone have a wide variety ofmatrices from micrites to sparry calcites though they are somewhat coarser in grainsize. Black to dark brown limestones previously mentioned are observed in this

zone.

3-2. Protriticites matsumotoi Subzone.

The Protriticites matsumotoi Subzone is defined by the first occurrence of Protriticitesmatsumotoi (Kanmera). The other constituent species of this subzone are Obsoletesobsoletus (Schellwien), Protriticites yanagidai Ota and Quasifusulinoides (?) sp. Thiszone has an estimated maximum thickness of about 31 m. Limestones of this sub-

zone strike NW and have a gentle dip toward the southwest. This zone is mostlylimestones with micrite matrix, but those with sparry calcite cements are intercalatedin the lower part of this subzone. The grains of sparry calcite cements are rathercoarse in size. Black to dark brown limestones are common in this zone.

4. Montiparus sp. A Zone.The Montiparus sp. A Zone is characterized by the occurrence of Montiparus sp. A.

36 Yasuhiro Ota

However, limestones along some traverses, did not yield Montiparus sp. A, but werecharacterized by Montiparus (?) sp. A. Montiparus (?) sp. A is closely similar toMontiparus sp. A, except for some features. Limestones of this zone are estimated tobe about 34 m in maximum thickness. They generally show a NW strike, dippingtoward southwest direction, with an occasional NE strike, dipping toward northwestdirection. The main constituent of limestones is micrite. Black to dark brown

limestones are also present in this zone. The following fusuhnaceans also occur inthis zone: Quasifusulina longissima (Moller), Quasifusulina sp. A, Triticites hidensis Igo,Triticites cf. obai Toriyama, and Triticites saurini Igo.

5. Triticitesyayamadakensis Zone.

The Triticites yayamadakensis Zone is defined by the occurrence of Triticitesyayamadakensis Kanmera. In the Jigoku-dani area, Triticitesyayamadakensis Kanmerais easily recognized, and is a good index fossil. The estimated thickness of this zoneis 124m. This zone is subdivided into the following three subzones by characteristicfusuhnaceans in ascending order.

5-1. Triticites saurini Subzone.

This subzone is characterized by abundance of Triticites saurini Igo. The base ofthis zone is demarcated by the first occurrence of Triticitesyayamadakensis Kanmera orTriticites yayamadakensis evectus Kanmera. The following fusuhnaceans are also inassociation with Triticites cf. bonus Chen and Wang, T. hidensis Igo, T. michiaeToriyama, T. aff. simplex (Schellwien).

Triticites yayamadakensis evectus was first described by Kanmera (1958) from theYayamadake Limestone, Kyushu, Japan. He pointed out the difference of thestratigraphic horizon between Triticites yayamadakensis yayamadakensis Kanmera andTriticitesyayamadakensis evectus Kanmera. However, the difference was not confirmed

in the Jigoku-dani area. The thickness of this subzone attains 15 m at most. Lime

stones of this subzone show general strike of about N14°W and dip about 18° towardSW. Limestones are mainly composed of micritic matrices, and black to dark brownlimestones are intercalated in some horizons.

5-2. Schwagerina sp. A Subzone.

The Schwagerina sp. A Subzone is characterized by the occurrence of Schwagerinasp. A and Triticitesyayamadakensis Kanmera. The lowest boundary of this subzone isdemarcated by the first occurrence of the genus Schwagerina. The occurrence ofSchwagerina sp. A was also ascertained from the AK Traverse in front of the Akiyoshi-dai Museum of Natural History and this species possibly has a wide distribution inthe Akiyoshi Limestone Group. The general strike and dip of limestones in this sub-zone are unknown. However, from the conformable relationship with the underlyinglimestones, they are common to those of the underlying subzone. Furthermore, thelimestone sequence of this subzone intercalates limestones with sparry calcite cementsas were seen in the underlying Triticites saurini Subzone. Limestones of this subzone

yield the following fusuhnaceans such as Triticites biconicus Toriyama, Triticites aff.


simplex (Schellwien), Triticites suzukii (Ozawa), and Schwagerina sp. B.5-3. Triticites biconicus Subzone.

The Triticites biconicus Subzone is characterized by the abundant occurrences ofTriticitesyayamadakensis Kanmera and the characteristicoccurrence of Triticites biconicusToriyama. Therefore, the fusulinacean constituents of this subzone clearly distinguish them from those of other subzones. Triticitesyayamadakensis Kanmera from thissubzone has a rather advanced form, such as larger shell and thicker spirotheca, thanthose in the lower horizon. Limestones of this subzone have a general strike of aboutN10°W and gently dip to the south ward. The basal part of this subzone mainlyconsists of limestones with sparry calcite cements. Matrices of limestones graduallychange from sparry calcites to micrites upward in the section. However, theuppermost part of this subzone contains coarse grains of fossil fragments of framebuilders. In the Jigoku-dani area, this zone is the upper limit of distribution of blackto dark brown limestones. The following fusuhnaceans are recognized in thissubzone: Quasifusulina sp. B, Triticites cf. isaensis Toriyama and Triticites kuroiwaensisToriyama.

6-1. Schwagerina (?) cf. satoi Zone.The lowest part of the Schwagerina (?) cf. satoi Zone is defined by the horizon from

the first occurrence of Schwagerina (?) cf. satoi (Ozawa) or Pseudofusulina (?) sp. A tothe first occurrence of Pseudoschwagerina muongthensis (Deprat) or Pseudoschwagerina sp.The estimated thickness of this zone is 76 m. The following fusuhnaceans are alsorecognized in this zone: Ozawainella aff. magna Sheng, Nankinella sp. A, Schubertella lataLee and Chen, Triticites haydeni (Ozawa), T. michiae Toriyama, T cf. obai Toriyama,T. cf. pseudosimplex Chen, T. aff. simplex (Schellwien), T. aff. suzukii (Ozawa),Schwagerina cf. stabilis (Rauser), "Pseudofusulina" cf. bacca Morikawa and Isomi, "Psf"aff.fusiformis (Schellwien), and Rugosofusulina arctica (Schellwien).

The fusulinacean index fossil, Schwagerina (?) cf. satoi (Ozawa) resembles thespecimen that was first described as Schellwienia satoi by Ozawa (1925). As it hasbeen already pointed out by Ozawa (1925) and Toriyama (1958), Schwagerinasatoi (Ozawa) is intermediate in form between Schwagerina and Pseudoschwagerina.Schwagerina (?) cf. satoi (Ozawa) from the Jigoku-dani area also has an intermediateform between Schwagerina and Pseudoschwagerina morikawai Igo and the present form is

similar to the microspheric form of Pseudoschwagerina. The question whether thepresent species is referable to the inflated schwagerinids is uncertain. This species,however, is very important for regional correlation. Fusuhnaceans of this zone aredistinguished from those of the underlying zone by their rather advanced forms inhaving larger shell, and thicker spirotheca. Weakly developed phrenothecae occurin some specimens. The phrenothecae are generally observed in Pseudofusulina, butthe present specimens are found in a lower horizon than the horizon of Pseudofusulinaas known before in the Akiyoshi Limestone Group. More detailed studies arerequired to solve the problem of the "Pseudofusulina" Horizon.

38 Yasuhiro Ota

Limestones of this zone are mainly composed of micritic matrices. However,the upper part of the underlying zone contains some fragments of fossils of reef framebuilders. No evidence of change in lithofacies of the lower Triticites biconicus Subzoneto the lower part of the Schwagerina (?) cf. satoi Zone suggest a remarkable hiatus.

7. Pseudoschwagerina muongthensis Zone.

The lowest part of the Pseudoschwagerina muongthensis Zone in the Jigoku-dani areais marked by the first occurrence of the genus Pseudoschwagerina, namely, Pseudoschwagerina muongthensis (Deprat) or Pseudoschwagerina sp. In the Jigoku-dani area,well preserved specimens of Pseudoschwagerina were not obtained. Along the AKTraverse near the Akiyoshi-dai Museum of Natural History, microspheric forms ofPseudoschwagerina are obtained from a stratigraphically slightly lower position compared with that of the megalospheric forms. Along the northern JI Traverse, JITraverse 5, the microspheric form of Pseudoschwagerina also occurs in a lower horizon

about 2 m below the megalospheric form. However, along the other JI Traverses,the microspheric form has not yet been confirmed. Therefore, the boundary on the

underlying zone is tentatively drawn between the horizons of microspheric form ofPseudoschwagerina sp. and megalospheric form of Pseudoschwagerina muongthensis (Deprat). The estimated maximum thickness of this zone is 32 m-K Limestones in

the lower part of this zone, consist of rather coarse constituents and intraclasts. Theupper part of the underlying Schwagerina (?) cf. satoi Zone is dominated by micritic

limestones. The changes of lithofacies is present between the upper part of

Schwagerina (?) satoi Zone and the lowest part of the Pseudoschwagerina muongthensisZone. However, each zone is conformably distributed with nearly the same strike

and dip. Therefore, a visible gap is not assumed between the two zones in the field.

On the other hand, limestones gradually become micritic in texture as the stratigra

phy is studied from the lower to the upper part in the present zone. This means that

the energy of the environment decreased.

The recognized species of this zone are as follows: Staffella moelleri Ozawa,Schubertella kingi Dunbar, Schwagerina okafujii Toriyama, Schwagerina primigena Nogami,

Schwagerina cf. princeps (Ehrenberg), Schwagerina sp. A, Schwagerina sp. B, Schwagerinasp. C, Schwagerina sp. D, Schwagerina (?) aff. kueichihensis (Chen), Pseudofusulina regularis(Schellwien) and Pseudoschwagerina (?) sp.

8. Pseudofusulina vulgaris globosa Zone.

The Pseudofusulina vulgaris globosa Zone is characterized by the abundant occur

rence of Pseudofusulina vulgaris globosa (Schellwien) and the association of Para-schwagerina sp. In this zone the author could not directly determine the strike anddip of the limestone. The present zone is considered to conformably overlie thePseudoschwagerina muongthensis Zone. Limestones in this zone are estimated to be atmost 83 m in thickness. They are characterized by micritic texture. However, thelowest part of this zone is composed of sparry calcite cements with rather coarsegrains. The grain size of limestones near the top of the Pseudoschwagerina muongthensis


Zone is micritic. The changes of lithofacies are present between the top of thePseudoschwagerina muongthensis Zone and the lowest part of this zone.

9-1. Pseudofusulina aff. ambigua Zone.The Pseudofusulina aff. ambigua Zone is the youngest zone, characterized by the

occurrence of Pseudofusulina aff. ambigua (Deprat). The index fossil, Pseudofusulinaaff. ambigua (Deprat), is closely similar to Fusulina ambigua of Deprat (1913), andPseudofusulina ambigua by Toriyama (1958). However, the present species differsfrom the above species in having a larger proloculus. More specimens are necessaryto determine the specific position. Distribution of this zone is restricted near thebottom ofJigoku-dani along the northern slope. The estimated thickness is 42 m atleast. This zone is characterized by rather coarse limestones. Near the boundarybetween the underlying zone and the present one, the limestones with sparry calcitecements intercalate with somewhat coarse grained varieties. The limestones gradually decrease in grain size from the lower to the upper, and they become micritic intexture. However, they change to limestones with sparry calcite cements near the

top of this zone.

-1-2. Correlation

The Carboniferous and Permian chronostratigraphic units have been examinedin Japan for a long time and the Middle Carboniferous and Lower Permianbiostratigraphic units and their boundaries are currently being debated around theworld. In the Akiyoshi region, the Akiyoshi Limestone Group has been studiedsince Ozawa (1923) and many important studies of Japanese Carboniferous andPermian geology were carried out there, for example, the establishment of thefusulinacean specific zones of the Akiyoshi Limestone Group (Toriyama, 1958), thepaleoenvironmental investigation of the Akiyoshi Limestone Group as an organic reefcomplex (M. Ota, 1968), the examination on the geologic history of the lowest tolower part of the Akiyoshi Limestone Group in the northeastern part of the AkiyoshiPlateau (Yanagida, et al. 1971), and the establishment of the local standard of the

biostratigraphic units in the Akiyoshi Limestone Group (M. Ota, 1977). Recently,the Middle Carboniferous and Lower Permian biostratigraphic units were activelydiscussed and some important results were reported, namely, by Hasegawa (1988),Ueno (1989), Ozawa and Kobayashi (1990), Ishii (1990), Watanabe (1991) and Y.

Ota and M. Ota (1993). The refinement of the fusulinacean zones will contribute

not only for making clear the stratigraphic transition of fusuhnaceans, but also for

establishing the phylogeny of fusuhnaceans. In addition, the regional examinationof the chronostratigraphic units with sedimentological analysis requires careful at

tention.

In the investigated area, nine fusulinacean zones including seven subzones were

discriminated. The older limestones are successively exposed in topographicallyhigher positions along the slope ofJigoku-dani without any remarkable hiatus. The

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following fusulinacean zones are successively discriminated from the top to the

bottom along the slope: 1. Fusulinella biconica Zone, 2. Fusulina cf. shikokuensis Zone:

Fusulinella cf. obesa Subzone, Pseudofusulinella hidaensis Subzone, 3. Obsoletes obsoletus

Zone: Protriticites toriyamai Subzone, Protriticites matsumotoi Subzone, 4. Montiparus sp. A

Zone, 5. Triticites yayamadakensis Zone: Triticites saurini Subzone, Schwagerina sp. A

Subzone, Triticites biconicus Subzone, 6. Schwagerina (?) cf. satoi Zone, 7. Pseudoschwagerina muongthensis Zone, 8. Pseudofusulina vulgaris globosa Zone, and 9. Pseudofusulina aff.

ambigua Zone.

In this chapter, the author presents a correlation chart (Fig. 17) of each zone inthe Jigoku-dani area with Middle Carboniferous to Early Permian biostratigraphicunits established by workers in different areas of the Akiyoshi Limestone Group.

1. Fusulinella biconica Zone.

The Fusulinella biconica Zone was characterized by the occurrence of Fusulinellabiconica (Hayasaka). This zone was first introduced by Toriyama (1954a) withchronostratigraphic position of the Akiyoshian Series for this zone. According to M.Ota (1977), the lower part of Fusulinella biconica Zone is characterized by ratherprimitive species of Fusulinella, namely, Fusulinella simplicata Toriyama. Fusulinellabiconica (Hayasaka) typified the middle part of the zone and Fusulinella itoi Ozawa,the upper part. Ueno (1989) divided the Fusulinella Zone into the following twozones, the lower, the Fusulinella biconica Zone and the upper, the Fusulinella taishakuensisZone. In Jigoku-dani, the Fusulinella biconica Zone is definitively located at the top ofthe slope of the Jigoku-dani area, but the Fusulinella taishakuensis Zone was not con

firmed in this area. This zone corresponds to Fusulinella Zone in other areas.2. The Fusulina cf. shikokuensis Zone is characterized by the first occurrence of

subfamily Fusulininae, especially by Fusulina cf. shikokuensis Ishii.

This zone is divided into two subzones, the lower, the Fusulinella cf. obesa Sub-

zone, and the upper, the Pseudofusulina hidaensis Subzone. The Fusulinella cf. obesaSubzone, is characterized by Fusulinella cf. obesa Sheng. This subzone probablycorresponds to the Kurikian Series that was proposed by Kanmera (1952) from thefusulinacean biostratigraphy of the Yayamadake Limestone in the outer zone ofKyushu. Furthermore, this subzone is stratigraphically correlative with the Beedeinaakiyoshiensis Zone by M. Ota (1977). According to him, the Beedeina akiyoshiensisZone is typically developed in the Shishide-dai area, the northeastern part ofAkiyoshi-dai with distinguishable litho- and biofacies from the subjacent zone. InJigoku-dani, limestones of this subzone do not contain reef building organisms andare considered to have accumulated in a lagoonal environment within the Akiyoshiorganic reef complex. Beedeina akiyoshiensis (Toriyama) has not been found yet.The difference of the fusulinacean assemblage seems to be dependent on the difference of the bio- and lithofacies of limestones. This subzone is correlated to the

Fusulina Zone elsewhere.

The upper subzone, the Pseudofusulinella hidaensis Subzone, is characterized by the

42 Yasuhiro Ota

occurrence of Pseudofusulinella hidaensis (Kanuma). This zone was first introduced byOzawa and Kobayashi (1990) in the Akiyoshi Limestone Group. However, at

present, the occurrence of this species is confined to particular areas. In the Jigoku-dani area, Pseudofusulinella hidaensis (Kanuma) is found in some localities, but itsdistribution could not be traced widely. This subzone is probably correlated withthe upper part of the upper Fusulina-Fusulinella Zone.

3. Obsoletes obsoletus Zone

The Obsoletes obsoletus Zone is defined by the occurrence of Obsoletes obsoletus(Schellwien). This zone is subdivided into two subzones, the lower Protriticitestoriyamai Subzone and the upper Protriticites matsumotoi Subzone.

The lower, Protriticites toriyamai Subzone comprises primitive species of Protriticites, namely Protriticites toriyamai Ota and Protriticites masamichii Ota. This subzoneseems to be also characterized by the first appearance of very finely perforated wallsin genus. Distribution of this subzone is restricted in its stratigraphic distribution.The Protriticites toriyamai Subzone is considered to be the basal zone of the Hikawanthat was first introduced at Hikawa Valley, Kyushu, by Kanmera (1952). Additionally, this subzone is equivalent to the lower part of Obsoletes-Protriticites Zone orObsoletes Zone in other areas.

The upper, Protriticites matsumotoi Subzone is characterized by the occurrence ofProtriticites matsumotoi (Kanmera) with Obsoletes obsoletus (Schellwien). The basalboundary of the Protriticites matsumotoi Subzone with the underlying Protriticites toriyamai Subzone is marked by the first occurrence of Protriticites matsumotoi (Kanmera).Protriticites matsumotoi (Kanmera) was first described by Kanmera (1955) under thegeneric name of Triticites (s. 1.) and this species is a diagnostic one of the Hikawan.Here, the author treats this species as the genus Protriticites by its having the"Protriticites-tyot wall" only in the outer volution. This subzone may be equivalentto a lower part of Hikawan and the upper part of the Obsoletes-Protriticites Zone, andcan be correlated with the Triticites (s. 1.) matsumotoi Zone by M. Ota (1977). In theAK area and some other regions, the occurrence of the genus Quasifusulinoides wasreported from the upper part ofProtriticites Zone and/or the overlying strata. In theJigoku-dani area, however, the upper part of the present subzone yields Quasifusulinoides (?) sp., but no well-preserved specimen of Quasifusulinoides were obtained. Theupper part of this zone is possibly correlative with the Quasifusulinoides Zone in otherareas.

4. Montiparus sp. A Zone.The Montiparus sp. A Zone is characterized by the occurrence of the genus

Montiparus, and the basal boundary of this zone is drawn by the first occurrence ofMontiparus sp. A or Montiparus (?) sp. A. The upper limit of this zone is defined bythe first occurrence of Triticites yayamadakensis Kanmera and T.yayamadakensis evectusKanmera. The genus Montiparus was first introduced by Rozovskaya (1948) as asubgenus of Triticites (s. 1.) with the name of Triticites montiparus Ehr. em. Moell.


Davydov (1990) showed the phylogenetic line of Protriticites-Montiparus-Rauserites. In

the Jigoku-dani area, continuation of the limestone sequence is confirmed without

any remarkable hiatus from the Protriticites matsumotoi Subzone to the Montiparus sp. AZone. This generic transition from the genus Protriticites to the genus Montiparus inthe above phylogenetic line is acceptable in the Jigoku-dani area. Therefore it ispossible to establish the datum level by the first occurrence of the genus Montiparus.This zone probably corresponds to the Montiparus Zone or the lower part of Triticites(s. 1.) Zone.

5. Triticitesyayamadakensis Zone.

The Triticites yayamadakensis Zone is characterized by the occurrence of Triticitesyayamadakensis Kanmera. This zone is subdivided into three subzones, the lower, the

Triticites saurian Subzone, the middle, the Schwagerina sp. A, and the upper, theTriticites biconicus Subzone. The diagnostic species of this zone, Triticites yayamadakensis Kanmera was described from the Yayamadake Limestone (Kanmera, 1955).Therefore, the Triticitesyayamadakensis Zone in the Jigoku-dani area is correlated to theTriticites yayamadakensis Zone of the upper Hikawan Series (Kanmera, 1952; Toriyama 1967).

The representative species of the lower, the Triticites saurini Subzone, is Triticitessaurini Igo first reported from Fukuji, Hida Massif, central Japan (Igo, 1957). Thisspecies has a shell of large size with highly complicated septa and well-developedchomata. In the Jigoku-dani area, this species is associated with Triticites yayamadakensis evectus Kanmera that was originally reported from a horizon higher than thatof Triticitesyayamadakensis yayamadakensis Kanmera. Therefore, a slight doubt on thestratigraphic position of this subzone still remains. More detailed examinations ofthe fusulinacean constituents of this subzone are necessary to confirm the exactstratigraphic position.

The middle part of this zone, the Schwagerina sp. A Subzone, is characterized bythe abundant occurrence of Schwagerina sp. A. Outside the Jigoku-dani area, thissubzone is also confirmed along the AK Traverse. The boundary with the lowersubzone is defined by the first occurrence of the genus Schwagerina. Therefore, thebasal boundary of this subzone possibly coincides with lower to middle part of theTriticites-Schwagerina Zone(s. s.).

The upper subzone, the Triticites biconicus Subzone, is discriminated by predominance of Triticites biconicus Toriyama. In theJigoku-dani area, the present subzoneis distributed over the Schwagerina sp. A Subzone. This subzone also contains Triticites yayamadakensis Kanmera in association with Triticites biconicus Toriyama. Triticites yayamadakensis from this subzone is very similar to Triticites ozawai originallydescribed by Toriyama (1958) and Schellwienia montipara (Ehrenberg) by Ozawa(1925), respectively from the Akiyoshi Limestone Group. Triticites yayamadakensisfrom this subzone has an intermediate form between the above two species. On theother hand, Triticites ozawai Toriyama was reported from the Triticites simplex Zone in

44 Yasuhiro Ota

the Akiyoshi Limestone Group (M. Ota, 1977). Summarizing these evidences, theTriticites biconicus Subzone possibly corresponds to the upper part of the Triticitessimplex Zone(M. Ota, 1977). These three subzones, are correlative with the middle

and upper part of the Triticites simplex Zone (M. Ota, 1977).6. Schwagerina (?) cf. satoi Zone.

The lower boundary of the Schwagerina (?) cf. satoi Zone is tentatively drawn by

the first occurrence of Schwagerina (?) cf. satoi (Ozawa) and Pseudofusulina (?) sp. A.The distinguishing species, Schwagerina (?) cf. satoi (Ozawa) from the Jigoku-daniarea has an intermediate form between the inflated schwagerinids, e.g. Pseudo

schwagerina, and not inflated ones, and this species is very important for correlation.This zone also contains the following fusuhnaceans: Ozawainella aff. magna Sheng,Nankinella sp. A, Schubertella lata Lee and Chen, Triticites haydeni (Ozawa), Triticitesmichiae Toriyama, Triticites cf. obai Toriyama, Triticites cf. pseudosimplex Chen, Triticitesaff. simplex (Schellwien), Triticites aff. suzukii (Ozawa), Schwagerina cf. stabilis(Rauser), "Pseudofusulina" cf. bacca Morikawa and Isomi, "Pseudofusulina" aff. fusi

formis (Schellwien) and Rugosofusulina arctica (Schellwien). In comparison withfusuhnaceans of the underlying zone, those of this zone are characterized by havingadvanced forms, such as larger shell and thicker spirotheca. It is apparent thatfusulinacean diversity rapidly increased in the Schwagerina (?) cf. satoi Zone. Inaddition, coarse grained limestones with fragments of reef frame builders are intercalated near the boundary between the present zone and the underlying zone. Thechanges of lithofacies and faunas are present near the basal boundary of the presentzone. On the other hand, this zone is also characterized by the appearance of thesefusuhnaceans that possess the phrenothecae typically recognized in the genusPseudofusulina. Degree of the development is weak, but the phrenothecae can beobserved in some specimens. Summarizing these facts, the author tentativelycorrelates the basal boundary of the Schwagerina (?) cf. satoi Zone with the appearance

of "Pseudofusulina" or the basal boundary of the Daixina Zone.7. Pseudoschwagerina muongthensis Zone.The Pseudoschwagerina muongthensis Zone is demarcated from the underlying zone

by the first occurrence of the genus Pseudoschwagerina. This lower boundary possiblycoincides with the first occurrence of the inflated schwagerinids. However, Schwagerina (?) cf. satoi (Ozawa) in the underlying zone has the intermediate form betweenSchwagerina and Pseudoschwagerina. Therefore, the basal boundary of this zone isdrawn by using fusuhnaceans with typically inflated shell. In the Jigoku-dani area,they are represented by Pseudoschwagerina muongthensis (Deprat) and Pseudoschwagerinasp. Unfortunately, well-preserved materials of Pseudoschwagerina have not beenobtained from the Jigoku-dani area, and as a result the detailed stratigraphic discussion of this zone is very hard to make clear. However, an obtained sagittalsection of the microspheric form of Pseudoschwagerina sp. is closely similar to that ofPseudoschwagerina morikawai Igo from the AK area in front of the Akiyoshi-dai Muse-


um. Outside the microspheric form of Pseudoschwagerina, the megalospheric form ofPseudoschwagerina muongthensis (Deprat) was obtained from a slightly higher horizonthan that of the former along the JI Traverse 5. This stratigraphic relationship,however, was not confirmed in other traverses. This zone can be correlated with thestrata containing Pseudoschwagerina and typical inflated schwagerinids. Besides,limestones near the lowest boundary of this zone are composed of rather coarselimestones with sparry calcite cements. Conspicuous changes of lithofacies from thetop of the Schwagerina (?) cf. satoi Zone to the basal part of the Pseudoschwagerinamuongthensis Zone are apparently observed as stated previously. The facies changeseems to be closely related to the appearance of the genus Pseudoschwagerina. Fromthe above facts, the first occurrence of the genus Pseudoschwagerina becomes anexcellent marker for the correlation of the basal part of the Lower Permian. In

Japan, the Lower Permian is represented by the Sakamotozawan Series in Sakamoto-

zawa and Nagaiwa areas, with the Kitakami massif as the type locality. Toriyama

(1963) proposed two subzones for the Sakamotozawan, namely the lower Pseudoschwagerina morikawai Subzone and the upper Pseudofusulina vulgaris Subzone. Accord

ing to Kanmera and Mikami (1965a, b), the basal part of the Sakamotozawan Seriesis absent at the type locality. Therefore, the definition of the Sakamotozawan Series

has become ambiguous. However, the Pseudoschwagerina muongthensis Zone possibly

corresponds to the lower part of Sakamotozawan Series that was defined as the lower

Permian by the first occurrence of the genus Pseudoschwagerina.8. Pseudofusulina vulgaris globosa Zone.

The Pseudofusulina vulgaris globosa Zone is characterized by the abundance ofPseudofusulina vulgaris globosa (Schellwien) . The lower part of this zone in Jigoku-dani area comprises Paraschwagerina spp. Limestones of this zone mostly consist ofmicritic matrices, but those near the base and top of this zone comprise sparry calcitecements with coarse grains. Change of lithofacies from the upper part of the underlying Pseudoschwagerina muongthensis Zone to the present zone is obvious, but thelimestone sequence containing Paraschwagerina sp. and Pseudofusulina vulgaris globosa(Schellwien) seems to represent a nearly complete succession. The present zone iscorrelated with Pseudofusulina vulgaris Zone in other areas. This zone possibly corresponds to the upper or middle part of the Sakamotozawan Series.

9. Pseudofusulina aff. ambigua Zone.

The Pseudofusulina aff. ambigua Zone is defined by the first occurrence ofPseudofusulina aff. ambigua (Deprat). Distribution of this zone is restricted to the

bottom of Jigoku-dani, and therefore the detailed characters are not observed. Therepresentative species of this zone is Pseudofusulina aff. ambigua (Deprat). This

species is closely similar to Pseudofusulina ambigua of Deprat (1913), but it differs fromthe latter species in having a slightly larger proloculus and a more developedphrenothecae. In the Jigoku-dani area, Pseudofusulina aff. ambigua (Deprat) isassociated with Pseudofusulina cf. vulgaris s. s. (Schellwien), which is similar to

46 Yasuhiro Ota

Pseudofusulina vulgaris of Schellwien (1909) and also resembles Chalaroschwagerinainfiata of Skinner and Wilde (1965). This zone is tentatively compared with thestrata containing the genus Chalaroschwagerina, but its precise stratigraphic position is

unknown. In the Akiyoshi region, Toriyama (1954a, b, 1957, 1958) first dividedParafusulina Zone into the lower Pseudofusulina ambigua Subzone and the upper

Parafusulina kaerimizensis Subzone. The present zone possibly corresponds to the

previous Pseudofusulina ambigua Zone in the Akiyoshi Limestone Group.

-1-3. Conclusion

In the Jigoku-dani area, the Akiyoshi Limestone Group is characterized by thefollowing paleontological and lithological compositions and the author's studies led to

the following conclusions.

Biostratigraphically, limestones in this area are divided into the nine fusulinacean zones including seven subzones, ranging from the Middle Carboniferous to theLower Permian. They are as follows in ascending order: 1. Fusulinella biconica Zone,2. Fusulina cf. shikokuensis Zone, 2-1. Fusulinella cf. obesa Subzone, 2-2. Pseudofusu

linella hidaensis Subzone, 3. Obsoletes obsoletus Zone, 3-1. Protriticites toriyamai Subzone,

3-2. Protriticites matsumotoi Subzone, 4. Montiparus sp. A Zone, 5. Triticites yayamadakensis Zone, 5-1. Triticites saurini Subzone, 5-2. Schwagerina sp. A Subzone, 5-3.

Triticites biconicus Subzone, 6. Schwagerina (?) cf. satoi Zone, 7. Pseudoschwagerinamuongthensis Zone, 8. Pseudofusulina vulgaris globosa Zone, 9. Pseudofusulina afT. ambiguaZone.

The above listed zones are easily traceable in this area and indicate that these

limestones are structurally inverted.Lithologically, limestones in this area have micritic matrices without biolithites.

Sedimentary environment of limestones is considered to be lower energy environments like a lagoon within the Akiyoshi organic reef complex. Additionally, anyremarkable stratigraphical gap, such as the lack of an important fossil zone, was notconfirmed through the fusulinacean zones. This evidence indicates that the lagoonal

limestones in the area were continuously accumulated through the Middle Carbon

iferous and Lower Permian.

In the Jigoku-dani area, Pseudoschwagerina muongthensis Zone is defined by the firstoccurrence of the inflated schwagerinids: pseudoschwagerinids, namely, the genusPseudoschwagerina. The inflated schwagerinids including the genus Pseudoschwagerinaare supposed to be planktonic during a part of their life cycle (Ross, 1982) and haveworld-wide distribution. Therefore, they are apparently excellent index fossils and

are the most useful for the correlation of the Lowest Permian. The genus Pseudo

schwagerina is known from some characteristic lithofacies, such as the biohermal limestones (Ross, 1964). For regional correlation, the associated fossils are indispensable

for determining the age and paleoenvironment. In this paper, the author prefers tocorrelate the limestones of the Pseudoschwagerina muongthensis Zone to the Lowest

Fusulinacean Biostradgraphy of the Akiyoshi Limestone Group, Part I 47

48 Yasuhiro Ota

Permian by taking the first occurrence of the inflated schwagerinids (pseudo

schwagerinids) into consideration.

-II-1. The second investigated AK areaThe second investigated AK area is located in front of the Akiyoshi-dai Museum

of Natural History. The details of the stratigraphy and paleontology in this areahave already been described by Y. Ota and M. Ota (1993). Here, the author

reexamines the results of the investigation of the AK area, to compare with those ofthe Jigoku-dani area.

The selected area represented by AK Traverse is in the normal sequence of the

Akiyoshi Limestone Group (M. Ota, 1977). This traverse was established along the

general trend, NE-SW (Fig. 18). The author had thin sections from rock samples of56 localities and reexamined the biofacies and lithofacies.

-II-2. Results of the investigations-2-(l). Biofacies and Lithofacies

The limestones are divided into two types by their color in the field. The first

type is characterized by white limestone whereas the second one is black to dark gray

color limestone. The former is subdivided into micrite, limestones with the sparry

calcite cements and intermediate micritic limestone with micrite and sparry calcite

cements. Dunham's classification (Dunham, 1962) of limestone is used for the

present study. In the classification he emphasized that the limestone texture is

important for the analysis of the energy condition. According to his classification,limestones along AK Traverse are recognized as the alternation of those of micriticmatrices and sparry calcite cements. In addition the black to dark brown color

limestones occur at AK 9, AK 11 and AK 12. The distribution of sedimentary facies

is shown in Fig. 19.

Grain components consisting of abundant fusuhnaceans and phylloid algae wereobtained from many localities in this area, and coarse grained limestones containingfragments of crinoids and bryozoans were interbedded in this limestone sequence(Fig. 20).

Summarizing these facts, the sedimentary environment of this area is reconstructed as the environment near an marginal lagoon within the Akiyoshi organic reefcomplex.

-2-(2). Analysis of fusulinaceans along AK TraverseAlmost all localities along AK Traverse yield many fusulinaceans. Lists of the

identified fusulinaceans on AK Traverse and the composite stratigraphic sectionswith typical fusulinaceans are shown in Table 8 and Figs. 21, 22. On the basis ofthe fusulinaceans along AK Traverse, each horizon of this limestone sequence wascharacterized by the following fusulinacean subfamilies.

AK 1-AK 6: Fusulinellinae


LEGEND

Micrite Matrix

Micritic Matrix

Sparry CalciteCements

Black to Dark Brown

Color Limestone

Fig. 19. Distribution of sedimentary facies along the AK Traverse.

49

50 Yasuhiro Ota

LEGEND

DEBRIS LIMESTONE

INCLUDING

CRINOIDS AND BRYOZOANS

FUSULINACEAN LIMESTONE

PHYLLOID ALGAL LIMESTONE

DASYCLADACEAN ALGAL LIMESTONE

LIMESTONE CONGLOMERATE

9 10 20 30

7

Fig. 20. Route map showing therepresentative biofacies and lithofacies of limestones alongthe AK Traverse.


Table 8. Distribution of the fusulinacean species in the AK area.

S^S; ^Locality in!!11 111 H22!22"Z3 333 3*44 <<US?555>PWeS t J ^4 0/o»03 45fi 7fi01 3456 790 2 4_ 71 _ 3 4S6834S6OzawalneHaso. . ., ., _ __ IIISchuhertelto**iji nimharand SKIfinfif _l , ^HSchubertetaso.n.s. •.fi/suine«asp.A I IObsoletesobsoletus (SeJietlwien) • .„ , • _ObsoletessD. • ...Protimctes matsumota (Kanmera) I 1PseuctotusuHnella hidaensis [ûma) IQuasBusuttnasD. k .. IIQuastmsuilnaso. IQuasifusultooUes so. A • ., _. _ ._..Quasltusutlnoklessp. M __ _._Huaosooiuseneliavn so. I __,,.,Montiparussp.A _, IMwrtfearasttiso. .,.,-.,., . ••pseuaotusuma vwoans s. st (scneuwten •Pseuaotusuma vulgaris globosa (Sctiellw enT _JI _.. _ ._Pseuaotusuma spp. IIScnwaaertnad. compacta (White) •Sctmaoertrmalobulus SponfcaWatanabe •_ ._ _ScftwacrerirtasteMsffauser) , , 1. 1,1Schwaaetina so.A II _ 1Schwaoerin&soo. 1 1

••

Triticites Wcon/cusTortvama _ _______ 17/a/tffes owratfeanKRoawsRaYa ._._..., _.. _ • ._..., _ .Mc//eselibsoAris&Torlvama ImtdtesexsculBtustao _,. I ,r/ês mfcfflaeTorivama .... _ •JWoftesorawa/Torlyama ,., .,.•..., , ,_ •_ __F/«*«esc».ijaraaxffa»Rauser I. ...imiatesa.sauimiwo ,.__ _.•.,__Trttlcttes a. secaucus isas | |M*»escJ.s//i««e)f(Scrtelwlen) ._.,. __...,. ... •7]rtftbfffisso.A 1TritkHesso. B UTriMesso.C •r. m alt. vavamaOaXensts evectus Kanmera pTriticttesmso. ..„ _ I .Sphaeroschwaaerinatf) sd. |Pseudoschwaoertnaworllcawalltio ^NT

Fseudosctiwaaertna so. _______ _______ ____________ _________ _____ _ _

AK 6-AK 9, and AK 11: Fusulininae and Fusulinellinae

AK 9-AK 10 and AK 12-AK 25: Schwagerininae

AK 25 and AK 35: Pseudoschwagerininae and Schwagerininae

(+ Biwaellinae?: Sphaeroschwagerina (?))

AK 35-AK 41: Fusulinellinae

(4-Schwagerininae?: Montiparus (?))AK 41-AK 56: Schwagerininae

( +Fusulininae: Quasifusulina)Here, the author wants to pay special attention to the classification of fusulinaceans,

because different opinions on the systematics of fusulinaceans are recognized in the

obtained fusulinaceans. For examples: Obsoletes should be referred to Schwagerininae (Rozovskaya, 1975; Sheng el al., 1988); Protriticites should be referred to

Fusulininae (Sheng et al., 1988); Quasifusulina should be referred to Schwagerininae

(Sheng etal., 1988).

Based on modes of fusulinacean occurrences, namely transitions and characteris

tics of the faunal elements and lithofacies of limestones, the following zones are

r.

Psf

lls.

hid

aen

sis

'/..

>>

**

ro

w

—i

L

Pro

trit

icit

esm

ats

um

oto

i/..

Qfd

.sp.

AZ

.M

onti

paru

ssp.

AZ

.

CD

>>

ro

co

o^

Sch

wag

erin

asp

.A

Z.

T.s

impl

ex/..

>>

nn

c/>

•5*

pi 5C

re•n

5 re

-1

fo

9 8v: n

o

T.

U&

j2

s7

-re

ps

3X

0

I

,5


AK30.

AK29.

AK2a

AK27.

AK2&

AK23.

AK22

AK21

AK20

AK19

AKia

Pseudofusulina vulgarisglobosa (Schellwien)

Pseudofusulina vulgariss. str. (Schellwien)

Schwagerina stablis (Rauser)

Pseudoschwagerina PseudoSchwaaerina sp Pseudoschwagerinamorikawai Igo rseuoosenwagenna sp. muongthensis (Deprat)

Triticites ellipsoidalis Toriyama

Rugsochusenella (?) sp.

5M

1mm

Fig. 21-2. (Continued).

53

r.-i

AK34. SSiS

AK33

AK3J

AK31.

AK3a

Yasuhiro Ota

Pseudofusulina sp.

Sphaeroschwagerina (?) sp.

5__3Schwagerina

globulus japonicus Watanabe


5M

1mm

discriminated in ascending order.

1. Pseudofusulinella hidaensis Zone

2. Protriticites matsumotoi Zone (s. 1.)

2-(2). Quasifusulinoides sp. A Zone2-(l). Protriticites matsumotoi Zone (s. s.)


4. Triticites simplex Zone (s. 1.)

4-(2). Triticites simp/ex Zone (s. s.)

4-(l). Schwagerina sp. A Zone5. Pseudoschwagerina muongthensis Zone

6. Pseudofusulina vulgaris Zone

The occurrence of these fusulinaceans and the limestone lithology support theconclusion that AK Traverse is composed of two nearly complete depositional sequences. The first sequence is recognized within AK 1 to AK 35, whereas the

second sequence is recognized within AK 35 to AK 56.

The maximum thickness of each zone within the sequences is shown in Table 9.Each zone is characterized by the following diagnostic fusulinaceans and stratig

raphic features (Fig. 23) in ascending order.1. Pseudofusulinella hidaensis Zone

The Pseudofusulinella hidaensis Zone is characterized by the occurrence of Pseudofu-

Fusulinacean Biostratigraphy of the Akiyoshi Limestone Group, Part 1

AK48

AK47

AK46-

AK45

AK44

AK41.

AK40.

AK39

AK38.

AK37J

AK36.

AK35

Triticites ozawai Toriyama Triticites michiae Toriyama

Quasifusulina sp.

Montiparus (?) sp. Protriticites Protriticitesmatsumotoi matsumotoi

(Kanmera) (Kanmera)

5M

Triticites (?) all. Obsoletes Obsoletes sp. Montiparus (?) sp.yayamadakensis obsoletus

evectus Kanmera (Schellwien)

1mm

Fig. 22-1. The composite stratigraphic section in the AK area (Second sequence).

55

56

AK56. ;

AK55.;

iAK54.1

AK53.3

AK52j

AK5tt

AK50. 2

AK49.1

AK48. i

Yasuhiro Ota

Schwagerina stabilis (Rauser)

Schwagerina cf. compact (White)

Schwagerina stabilis (Rauser)

Schwagerina (?) sp.

x4Ozawainella sp.

5M

x4 N - x4 ^55* x4Schubertella kingi Dunbar and Skinner Ozawainella sp. 1mm


Fusulinacean Biostratigraphyof the Akiyoshi Limestone Group, Part I 57

Table 9. The maximum thickness of each zone in the AK area.

Fusulinacean zone Thickness

6. Pseudofusulina vulgaris Zone (AK27-29) 13m

5. Pseudoschwagerina muongthensis Zone (AK25-27) (AK52-56) 11 m 34 + m


4-(2). Triticites simplex Zone (s. s.) (AK 18-25) (AK46-52) 35 m 42 m

4-(l). Schwagerina sp. A Zone (AK15-18) (AK41-46) 16m 20 m

3. Montiparus sp. A Zone (AK9-10, AK12-15) (AK37-41) 14m 12m


2-(2). Quasifusulinoides sp. A. Zone (AK8-9, AK11) 4 m

2-(l). Protriticites matsumotoi Zone (s. s.) (AK6-8) 13m

1. Pseudofusulinella hidaensis Zone (AK1-6) 34+m

sulinella hidaensis (Kanuma) and the associated Fusulinella sp. This zone mainly con

sists of white micrite limestone.


The Protriticites matsumotoi Zone (s. 1.) is characterized by the occurrence ofProtriticites matsumotoi (Kanmera). This zone is subdivided into two zones, namely,

the lower, the Protriticites matsumotoi Zone (s. s.) characterized by Protriticites matsumotoi

(Kanmera), and the upper, the Quasifusulinoides sp. A Zone, characterized byQuasifusulinoides sp. A. The genus Quasifusulinoides was not confirmed from thesecond sequence in AK Traverse. The Quasifusulinoides Zone reported by Ueno(1989) is supposed to be restricted. Therefore, Quasifusulinoides sp. A. Zone istentatively discriminated and it is included in the Protriticites matsumotoi Zone (s. 1.) because the main fusulinacean constituents of the present two zones belong to Fusulinellinae and Fusulininae.

2-(l). Protriticites matsumotoi Zone (s. s.)

The Protriticites matsumotoi Zone (s. s.) yields Obsoletes obsoletus (Schellwien),Protriticites matsumotoi (Kanmera) and Triticites (?) aff.yayamadakensis evectus Kanmera.

Triticites (?) aff. yayamadakensis evectus Kanmera resembles the Late CarboniferousTriticitesyayamadakensis evectus Kanmera from the Yayamadake Limestone, Kumamoto

Prefecture in general shape. However, the stratigraphic horizon of the present species is higher than those of the closely related ones from Jigoku-dani and Yayama

dake, because the present species is associated with Obsoletes obsoletus (Schellwien).The limestones with these species commonly have limestones with micritic ma

trices. Limestones with sparry calcite cements are distributed near the lower

boundary of the Protriticites matsumotoi Zone (s. s.). There is a tendency of increased

micritic matrices toward the upper part of this zone.

58 Yasuhiro Ota

Zone Species

Pseudofusulina vulgaris Zone Pseudofusulina vulgaris s. s. (Schellwien),Pseudofusulina vulgaris globosa (Schellwien),Pseudofusulina sp., Sphaeroschwagerina (?) sp.,Triticites complicatus Rozovskaya

Pseudoschwagerina muongthensis Zone Pseudoschwagerina muongthensis (Deprat),Pseudoschwagerina morikawai Igo,Pseudoschwagerina sp.,Triticites ellipsoidalis Toriyamai,Schwagerina cf. compacts (White),Schwagerina stabilis (Rauser),AugosochuseneJ/a (?) sp.,Schubertella kingi Dunbar and Skinner

Triticites simplex Zone (s. 1.)Triticites simplex Zone (s. s.)

Triticites cf. secalicus (Say),Triticites ozawaiToriyama,Triticites michiaeToriyama,Trinities cf. paraarcticus Rauser,Schubertella kingi Dunbar and Skinner,OzawaineHa sp.

Schwagerina sp. A Zone Triticites biconicus Toriyama,Triticites cf. saurini Igo,Triticites ozawai Toriyama,Triticites exsculptus Igo,Triticites sp. B,Triticites sp.C,Schwagerina sp. A,Quasifusulina sp. A, Quasifusulina sp.,Ozawainella sp.

Montiparus sp. A Zone Triticites sp. A,Triticites (?) sp.,Sciitvageriiiaf?) sp. A,Montiparus sp. A,Montiparus (?) sp. A,Protriticites matsumotoi (Kanmera)?

fro(ritrcires matsumoroi Zone (s. 1.)Quasifusulinoides sp. A Zone

Quasifusulinoides sp. AQuasifusulinoides sp.

Protriticites matsumotoi Zone(s. s.) Triticites (?) aff. yayamadakensis evectus Kanmera,ft-otrific/res matsumotoi (Kanmera),Ohso/eres obsoletus (Schellwien)

Pseudofusulinella hidaensis Zone Pseudofusulinella hidaensis (Kanuma)

Fig. 23. Fusulinacean zones and the faunal elements of each zone in the AK area.

2-(2). Quasifusulinoides sp. A ZoneThe Quasifusulinoides sp. A Zone is discriminated by the first occurrence of

Quasifusulinoides sp. A. This zone is only confirmed in the first sequence in AK Traverse with a maximum thickness of about 4 m.


The diagnostic species of this zone is Montiparus sp. A, and the associated fossilsare as follows: Protriticites matsumotoi (Kanmera), Montiparus (?) sp. A, Schwagerina (?)sp. A, Triticites sp. A, and Triticites (?) sp. In this zone limestones with sparry calcitecements gradually change to micritic in the upper part of the section. Protriticitesmatsumotoi (Kanmera) was found in limestones with sparry calcite cements in thelower part of the present zone. The occurrence of Protriticites matsumotoi (Kanmera)which is the diagnostic species of the underlying zone probably reveals thatProtriticites matsumotoi (Kanmera) and other associated species are derived from the


underlying limestones.


The Triticites simplex Zone (s. 1.) is characterized by the occurrence of Triticitesand Schwagerina, comparing with the Triticites-Schwagerina Zone (s. s.).

4-(l). Schwagerina sp. A Zone

The Schwagerina sp. A Zone is characterized by the predominance of Schwagerinasp. A. The lower boundary of this zone in the first sequence in AK Traverse isdrawn at the horizon characterized by the occurrence of Triticites exsculptus Igo,

Triticites ozawai Toriyama and Triticites cf. saurini Igo, whereas that of this zone in the

second sequence is tentatively drawn at the horizon where Quasifusulina sp. occurs

and lithofacies change from limestones with micrite matrices to those with sparry

calcite cements.

Schwagerina sp. A is similar to Rugosofusulina sp. A reported by Hasegawa (1988).

However, the former is distinguished from the latter by its very weak rugosity of wall.The specific constituents of this zone are as follows: Ozawainella sp., Quasifusulina sp.A, Quasifusulina sp., Triticites biconicus Toriyama, Triticites exsculptus Igo, TriticitesozawaiToriyama, Triticites cf. saurini Igo, Triticites sp. B and Triticites sp. C.

The lower part of the present zone is predominant in limestones with sparrycalcite cements and these contain Schwagerina sp. A. Limestones with micrite matrices

increase toward the upper part of this zone.

4-(2). Triticites simplex Zone (s. s.)

In the AK area, Triticites simplex (Schellwien) was not confirmed. However,

the specific assemblages of fusulinaceans identify them as members of Triticites simplexZone (s. s.), which is equivalent to the upper part of the Triticites simplex Zone (s. 1.)(M. Ota, 1977). The following fusulinaceans are common in this zone: Ozawainellasp., Schubertella kingi Dunbar and Skinner, Schubertella sp., Schwagerina sp., Triticitesmichiae Toriyama, Triticites ozawai Toriyama, Triticites cf. secalicus (Say) and Triticitescf. paraarcticus Rauser. This zone mainly consists of limestones with micritic matri

ces. Limestones with sparry calcite cements appear and are interbedded with themicritic ones in the upper part of this zone. The energy condition of the depositionalenvironment is considered to have shifted from lower to higher.


The Pseudoschwagerina muongthensis Zone is characterized by the occurrence ofPseudoschwagerina muongthensis (Deprat) and the lower boundary of this zone is definedby the first appearance of Pseudoschwagerina (Pseudoschwagerina morikawai Igo). Alongthe first sequence of AK Traverse, Pseudoschwagerina morikawai Igo, the microsphericform first occurs at a horizon about 8 m lower than that of Pseudoschwagerina muongthensis (Deprat), the megalospheric form. However, Pseudoschwagerina muongthensis(Deprat) is associated with Pseudoschwagerina morikawai Igo at AK 26. Furthermore,the boundary of the Pseudoschwagerina muongthensis Zone with the underlying zone wasformerly drawn by the first occurrences of Pseudoschwagerina [Pseudoschwagerina

60 Yasuhiro Ota

muongthensis (Deprat)], including megalospheric and microspheric forms. Therefore, the base of the present Pseudoschwagerina muongthensis Zone is demarcated by thefirst occurrence of the inflated schwagerinid, Pseudoschwagerina. Along the secondsequence, Pseudoschwagerina was not found, but the zone was recognized from a horizon (AK 52), where advanced fusulinaceans occurred.

Limestones of the first sequence yield the following fusulinaceans: Pseudoschwagerina muongthensis (Deprat), Pseudoschwagerina morikawai Igo, Pseudoschwagerina

Fig. 24. Distribution of fusulinacean zones in the AK area (modified from Hasegawa,1992).


sp., Rugosochusenella (?) sp., Triticites ellipsoidalis Toriyama and Schwagerina stabilis(Rauser). The second sequence yields Schwagerina stabilis (Rauser), Schwagerina cf.compacta (White), Schwagerina (?) sp., Schubertella kingi Dunbar and Skinner, andOzawainella sp.

This zone is, as a whole, composed of micritic limestones except for the upperpart. Limestones across the boundary between the present zone and the underlyingzone along the first sequence change upward from those with sparry calcite cementsto micritic. Limestones along the second sequence, however, are mainly composedof micritic limestones on both sides of the boundary. Limestones with sparry calcite

cements are common in the upper part of the present zone. They suggest a relatively high energy environment and yield abundant Schwagerina, such as Schwagerinastabilis (Rauser). The lack of limestones with sparry calcite cements near the lowerboundary of the Pseudoschwagerina muongthensis Zone in the second sequence, probably

suggest that these micritic limestones were accumulated in an environment in whichthe inflated schwagerinids, i.e. Pseudoschwagerina, could not exist.


The Pseudofusulina vulgaris Zone in the AK area is characterized by the diagnostic

species, Pseudofusulina vulgaris (Schellwien), and the following associated species,Triticites complicatus Rozovskaya, Sphaeroschwagerina (?) sp., Pseudofusulina vulgarisglobosa (Schellwien) and Pseudofusulina sp. This zone is characterized by limestoneswith the micritic matrices.

From distribution of the zones (Fig. 24), it has become clear that the succession

of AK Traverse consists of two nearly complete limestone sequences, possiblyseparated by the NE- SW fault (shown by Ozawa and Kobayashi, 1990).

-II-3. Correlation

-3-(l). Correlation (Within Japan)In this chapter the author presents the tentative correlation of fusulinacean zones

of the Akiyoshi Limestone Group of the AK area and a reference proposal for thesubdivision of the Middle Carboniferous and Lower Permian fusulinacean zones

(shown in Fig. 17).


The characteristic species of this zone is Pseudofusulinella hidaensis (Kanuma),originally described by Kanuma (1953) as Wedekindellina (?) hidaensis. Ozawa and

Kobayashi (1990) first treated this species under the generic name of Pseudofusulinellaand established the Pseudofusulinella hidaensis Zone with the diagnostic species. Thephylogenetic trend of Pseudofusulinella was studied by Ozawa (1967) and Wilde

(1971). According to Kanuma (1953), this species has a small elongate fusiformshell with a straight axis of coiling, inflated central area, bluntly pointed poles andslightly concave lateral slopes. In addition chomata are large and massive, andaxial fillings are well developed. Wedekindellina Dunbar and Henbest, 1933 is char-

62 Yasuhiro Ota

acterized by its elongated small shell, and well developed axial fillings and four layered wall with perforations. To the contrary, Pseudofusulinella Thompson, 1951 has aspirotheca composed of a tectum and diaphanotheca with very minute but distinctpores. The massive chomata in the center of the shell cover the lower surfaces of

spirotheca to give it the appearance of spirotheca of four layers as found in Fusulinellaand Fusulina. Pseudofusulinella is distinguished from Fusulinella by its younger occur

rences than the latter and by having different features of the wall and axial fillings.From its general shapes and features, the obtained specimen should be referable to

Pseudofusulinella hidaensis (Kanuma). The Pseudofusulinella hidaensis Zone of the author

is correlated with the same zone by Ozawa and Kobayashi (1990). In this investigated AK Traverse, Beedeina akiyoshiensis (Toriyama) which is the diagnostic speciesof the Beedeina akiyoshiensis Zone (M. Ota, 1977) was not confirmed. Hence it is

very difficult to directly correlate the Pseudofusulinella hidaensis Zone with the Beedeinaakiyoshiensis Zone. Nevertheless the present zone corresponds to the Beedeinaakiyoshiensis Zone based on biostratigraphic relationship between the present zone andthe underlying and overlying zones. Ueno (1989) recognized the Beedeina akiyoshiensis Zone between the upper, Fusulinella taishakuensis Zone and the lower, Protriticitessp. Zone. According to him, only Pseudofusulinella sp. (sp. nov.?) was reported fromProtriticites sp. Zone. Ueno (1991b) reported that Pseudofusulinella (Kanmeraia)praeantiqua Nassichuk and Wilde was found in the uppermost part of the Protriticitessp. Zone and the lower part of the Quasifusulinoides toriyamai Zone (Ueno, 1989), butthe detailed relationships between the Pseudofusulinella hidaensis Zone and these zonesare not clear. However, Fusulinella biconica Zone is correlative with the Fusulinella

biconica Zone of Hasegawa (1988) and Ozawa and Kobayashi (1990). On theother hand, the Fusulinella taishakuensis Zone was first introduced by Okimura (1987)

and is characterized by the occurrence of Fusulinella taishakuensis established by Sadaand Yokoyama (1970). The Fusulinella taishakuensis Zone is associated with thefollowing fusulinaceans: Fusulinella biconica (Hayasaka), Fusulinella simplicata Toriyama, Fusulinella bocki Moller and Fusulinella subsphaerica Toriyama. Judging from

the constituents of the preceding zones, the Fusulinella taishakuensis Zone and theFusulinella biconica Zone (Ueno, 1989) correspond to the Fusulinella biconica Zone (M.

Ota, 1977).


2-(l). Protriticites matsumotoi Zone (s. s.)Protriticites matsumotoi (Kanmera) is the diagnostic species of this zone. This

species was described by Kanmera (1955) as a representative species of HikawanSeries and is known as a primitive species of this genus. In well preserved specimens of Protriticites matsumotoi (Kanmera), the spirotheca of the third to the fourthand occasionally the fifth volutions appear to be composed of four layers. Thespirothecal characters closely resemble those of Fusulinella Moller. In maturespecimens, the spirotheca of the fifth to mature volutions have a clearly discernible


keriotheca. The classification of Triticites (s. 1.) and its evolution have been discussed

since Rozovskaya (1948) classified Triticites (s. 1.) into four subgenera, Triticites (s.s.), Montiparus, Rauserites and Jigulites. Some considerations concerned with theirseveral variations are present. One variation is the "Protriticites-type wall". Rauserand Fursenko (1959) described the wall structure of Protriticites that it is perforatedand composed of four-layers in the inner volutions and three-layers in outer ones,namely a tectum, protheca and outer tectorium. The same structure of Protriticiteswas also noticed by Loeblich and Tappan (1988). Sheng, Zhang and Wang

(1988) also confirmed that the inner spirotheca of Protriticites were composed of fourlayers like Fusulinella, but the outer spirotheca were composed of a tectum and theinner and outer tectoria. They also mentioned that Protriticites was an intermediateform between Fusulinella and Triticites (s. s.). Rozovskaya (1950) clearly illustratedthe keriothecal wall in Protriticites. Putrya (1948) remarked on the complicated wallof Protriticites in his original description of the genus. He noticed that it is composedof a tectum, diaphanotheca and two tectoria. Furthermore, he noticed that the

diaphanotheca, tectoria and chomata possess the structure of fine alveoli, and thecoarser ones are recognizable in the inner tectorium. In the outermost whorl the

alveolers structure reaches diaphanotheca. Davydov (1990) proposed the lineagefrom Protriticites to Rauserites, through Montiparus. According to him, the innertectorium which is considered as a characteristic feature of Montiparus is only presentin the inner whorls where the keriothecal wall is not present. Summarizingpreceding evidence, it is noticed that Protriticites has the inner tectorium in the outer

volution and if we recognize the inner tectorium in outer volution of a specimen, thenit might belong to Protriticites. Triticites (s. 1.) matsumotoi by Kanmera (1955) has aProtriticites-type wall only in the outer volutions. Based on these facts, the authortreats this species under Protriticites. Hasegawa (1988) treated this species as thediagnostic species of the Triticites matsumotoi Subzone. According to hisopinions, thisspecies has very primitive features of Triticites (s. 1.). Additionally, the fauna of theTriticites (s. 1.) matsumotoi Zone is missing in some areas. The fauna of the Triticitessimplex Zone directly overlies the Fusulinella-Fusulina Zone in some cases. Therefore,he interpreted that Protriticites was able to migrate to the place where a fusulinaceanfavorable environment appeared in the early stage. Recently, a primitive-Triticites(s. 1.) fauna, including Protriticites, was reported from the Akiyoshi region and someother districts. Hence, the author correlated the Protriticites matsumotoi Zone (s. s.)with limestones, bearing species of primitive Triticites (s. 1.).

The present Protriticites matsumotoi Zone (s. s.) corresponds to the Triticites (s. 1.)matsumotoi Zone (M. Ota, 1977), the Triticites matsumotoi Zone (Hasegawa, 1988) andthe Protriticites sp. Zone (Ueno, 1989). Furthermore it is correlative with the

Obsoletes obsoletus Zone (Watanabe, 1991) and the Protriticites (P.) matsumotoi Zone(Ishii, 1990).

64 Yasuhiro Ota

2-(2). Quasifusulinoides sp. A Zone

The Quasifusulinoides sp. A Zone is characterized by the occurrence of Quasifusulinoides. The occurrence of this zone is restricted and thus it is included in the

Protriticites matsumotoi Zone (s. 1.) on the basis of its confined distribution and the

stratigraphic relationship between the overlying and underlying zones. Ueno (1989)established the Quasifusulinoides toriyamai Zone and this zone is correlated with theQuasifusulinoides sp. A Zone. The present zone may be also equivalent to the lowerpart of the Montiparus montiparus-Quasifusulinoides ohtanii Zone (Ozawa and Kobayashi,1990) and the upper part of the Obsoletes obsoletus Zone (Watanabe, 1991). In theJigoku-dani area, well-preserved Quasifusulinoides do not occur, but Quasifusulinoides (?)sp. was obtained from the Protriticites matsumotoi Subzone. Therefore, the presentQuasifusulinoides sp. A Zone probably corresponds to the Protriticites matsumotoi Sub-zone of the Jigoku-dani area.

3. Montiparus sp. A ZoneThis datum level is defined by the occurrence of Montiparus. As mentioned

before, Montiparus was first introduced as a subgenus in four subgenera of Triticites (s.1.) with Triticites montiparus Ehr. em. Moell. as the type species by Rozovskaya(1948). However, the variations and definitions of Montiparus are ambiguous, andsome disagreements about the genus are present. Wilde (1984) treated MontiparusRozovskaya, 1948 as a synonym of Schwagerina montipara (Ehrenberg, 1854) emend.Dunbar and Skinner, 1936, and proposed the new name of Eotriticites. In short,Montiparus has historically two different types and thus the definition of Montiparus isunclear. The obtained specimens should be referred to Montiparus Rozovskaya,1948 with the following type species, Triticites (Montiparus) montiparus Rozovskaya,1948=Fusulina montipara Ehrenberg emend. Moller, 1878. Montiparus sp. A is adiagnostic species of the Montiparus sp. A Zone.

The Montiparus sp. A Zone is also associated with Protriticites matsumotoi (Kanmera), Montiparus (?) sp. A, Schwagerina (?) sp. A, Triticites sp. A and Triticites (?) sp.This zone is correlated with the lower part of the Triticites simplex Zone (M. Ota,1977), because Triticites in the present zone has a relatively primitive form. Moreover, this zone probably corresponds to the upper Montiparus montiparus-Quasifusulinoides ohtanii Zone and the Montiparus matsumotoi Zone (Ozawa and Kobayashi, 1990),the Triticites yayamadakensis Zone (Ishii, 1990) and the lower part of the Triticitessimplex Zone (Hasegawa, 1988).

4. Triticites simplex Zone (s. 1.)4-(l). Schwagerina sp. A ZoneThe Schwagerina sp. A Zone is distinguished by the characteristic occurrence of

Schwagerina sp. A. This zone is associated with occurrences of the following species:Triticites biconicus Toriyama, Triticites exsculptus Igo, Triticites ozawai Toriyama,Triticites cf. saurini Igo, Triticites sp. B, Triticites sp. C, Quasifusulina sp. A, Quasifusulinasp. and Ozawainella sp. Zhang (1991) placed the Triticites-Schwagerina Zone under


Pseudoschwagerina Zone and reported the first occurrence of Schwagerina in the lowerpart of the Triticites siuckenbergi Zone. Kanmera, Ishii and Toriyama (1976) alsoestablished the Schwagerina Zone under the Pseudoschwagerina Zone. The presentSchwagerina sp. A Zone corresponds to Triticites-Schwagerina Zone (s. s.) and is tentatively correlated with the lower parts of the Triticites simplex Zone (M. Ota, 1977) andthe Triticitesyayamadakensis Zone in the Jigoku-dani area.

4-(2). Triticites simplex Zone (s. s.)The specific constituents of the Triticites simplex Zone (s. s.) are as follows:

Ozawainella sp., Schubertella kingi Dunbar and Skinner, Schubertella sp., Schwagerina sp.,Triticites michiae Toriyama, Triticites ozawai Toriyama, Triticites cf. paraarcticus Rauser

and Triticites cf. secalicus (Say). Unfortunately, Triticites simplex (Schellwien) was

not collected in this investigation. However, judging from the coexisted fusulina

ceans, the specific assemblage corresponds to that of the upper part of Triticites simplexZone (M. Ota, 1977). It is also similar to those from the upper part of the Triticites

yayamadakensis Zone to Schwagerina (?) cf. satoi Zone of the Jigoku-dani area. Inaddition, the Triticites simplex Zone (s. s.) is correlated with the upper part of theTriticites hidensis Zone (Ishii, 1990), the Triticites (Rauserites) paraarcticus and Triticites(Rauserites) siuckenbergi Zones (Ozawa and Kobayashi, 1990), the upper part of theTriticites simplex Zone (Hasegawa, 1988) and the upper Triticites "simplex" Zone

(Ueno, 1989).


The Pseudoschwagerina Zone was formerly divided into two subzones by Toriyama

(1954a), namely the lower Triticites simplex Subzone and the upper Pseudofusulinavulgaris Subzone (Toriyama, 1954a). Hasegawa (1963) subdivided the Pseudoschwagerina Zone into two subzones, the lower, the Triticites simplex Subzone and the

upper, the Pseudoschwagerina muongthensis Subzone. The Pseudoschwagerina muongthensisSubzone was treated as the Pseudoschwagerina (P.) muongthensis Zone, and the Triticitessimplex Subzone as the Triticites simplex Zone by M. Ota (1977). The datum level of

this zone is formerly demarcated by the first occurrence of inflated schwagerinids, i.e.

Pseudoschwagerina muongthensis (Deprat), including megalospheric and microsphericforms. Therefore, the lowest part of the present zone in the AK area coincides with

the occurrence of Pseudoschwagerina morikawai Igo. Many fusulinacean workers have

studied before on the inflated schwagerinids and their paleoecology and paleo-biogeography. Studies on their provinciality were also presented by Ross (1962,1963a, 1964, 1967, 1982) and Gobbett (1973). Ross (1982) mentioned that several

genera among the schwagerinids were probably planktonic during a part of their lifecycles. Ross (1962, 1963a, 1964, 1967) examined their evolution, migrations and

dispersal in detail. Ross (1967, 1973) pointed out the difference of each provincebased on the paleobiogeographic separation of fusulinid faunas and also discussed the

lineage of Protriticites. A lineage with Montiparus-Obsoletes-Triticites was confirmedonly in the Eurasian- Arctic province. Whereas only Triticites was recognized at the

66 Yasuhiro Ota

same stratigraphic positions in Mid-continent province. Ross (1962, 1963a, 1964)classified the pseudoschwagerinids into eight complexes and he discussed theirdetails. From these studies, he concluded that the greatest diversity of them tookplace in the Tethyan seaway in later Wolfcampian time. On the other hand,Gobbett (1973) discussed Pseudoschwagerina as a cosmopolitan genus. As mentionedabove, it is very effective to use the datum level defined by the first occurrence of the

inflated schwagerinids for accurate global correlation. Rui and Zhang (1987) alsonoticed that pseudoschwagerinids might be used for global correlation, owing to their

rapid evolution and global distribution. The correlation of the PseudoschwagerinaZone has been discussed by many authors, such as Hanzawa (1942), Hayasaka and

Minato (1954), Fujimoto (1959), Fomichev (1960), Kahler (1961), Rauser (1965)

and Lapkin and Kats (1990). Although the inflated schwagerinids show globaldistribution, their occurrence seems to be restricted to somewhat coarser sediments.

Evidences for this was given by Ross (1964). Therefore, examination of their

accompanying fossils is indispensable for accurate correlation. The present zone iscorrelated with the Pseudoschwagerina (P.) muongthensis Zone (M. Ota, 1977), and the

Pseudoschwagerina muongthensis Zone in the Jigoku-dani area. The lower boundary of

this zone approximately coincides with those of the Sphaeroschwagerina fusiformis Zone

(Ishii, 1990, Watanabe, 1991), the "Sphaeroschwagerina" fusiformis Zone (Ozawa and

Kobayashi, 1990) and the Alpinoschwagerina (?)fusiformis Zone (Ueno, 1989).


The base of this zone is marked by the occurrence of the diagnostic species,

Pseudofusulina ex. gr. vulgaris (Schellwien). Several studies of the systematics ofPseudofusulina have been carried out internationally. Davydov (1988a, b) examined

in detail the origin and development of the pseudofusulinids. However, discussionson the systematics, classification and stratigraphic significance of the pseudofusu

linids still continue. Zhang (1983, 1991) discriminated "Pseudofusulina Bed" underthe Pseudoschwagerina Zone, and correlated this bed with lower Daixina sokensis Zone.

According to him, Pseudofusulina stratigraphically occurs in a bed lower than thatbearing Pseudoschwagerina. Rauser (1951) recognized the Pseudofusulina Horizonbeneath the Schwagerina Horizon in association with primitive species of Triticites. Inthe "Pseudofusulina Horizon", the earliest pseudofusulinids, i.e. Pseudofusulina krotowi(Schellwien) and Pseudofusulina paragregaria Rauser occur. Naoumova and Rauser

(1964) reported the occurrence of two different types of these Pseudofusulina fromdifferent stratigraphic horizons. Because of different reports, the correlation of thePseudofusulina Zone is very difficult. An urgent task is the clarification of the origin

and phylogeny of Pseudofusulina.The present Pseudofusulina vulgaris Zone corresponds to the Pseudofusulina vulgaris

Zone (M. Ota, 1977), the Pseudofusulina vulgaris Subzone (Hasegawa, 1988), thePseudofusulina ex. gr. vulgaris Zone (Ueno, 1989), the Chalaroschwagerina vulgaris Zone(Ishii, 1990), the Paraschwagerina akiyoshiensis-Pseudofusulina firm Zone, the Robusto-


schwagerina schellwieni pamirica-Schwagerina krotowi Zone and the Robustoschwagerinaschellwieni schellwieni-Pseudofusulina vulgaris vulgaris Zone (Watanabe, 1991), and the

Dutkevitchia splendida Zone and Pseudofusulina vulgaris Zone (Ozawa and Kobayashi,

1990).

-3-(2). Correlation (International)

In this chapter, tentative correlation between the investigated AK area and the

reference sections is examined. The name of the Carboniferous is derived from

England, and the name of Permian from "Perm" to the west of the Ural Mountains.The Carboniferous and Permian Systems were established in different areas with

different facies. There is so far no consensus of the definition of the boundary

between the two systems. Therefore, each worker has applied his own definition to

each stratigraphical division. Even in the stratotype, several proposals for its

division are present. Because of this situation, the refinement of biostratigraphic

units and accurate international correlation of the Upper Carboniferous and LowerPermian seems to be difficult and chaotic.

The following zones along AK Traverse are tentatively correlated with thebiostratigraphic units in the reference sections (Fig. 25).


This zone is characterized by Pseudofusulinella hidaensis (Kanuma). It is accompanied by Fusulina sp. Although Ozawa and Kobayashi (1990) first introduced thePseudofusulinella hidensis Zone, this zone is not confirmed in many areas. ThePseudofusulinella hidaensis Zone is correlative with the bed over the Fusulinella Zone.

Wilde (1971, 1975, 1984) classified Pseudofusulinella into four specific groups (GroupI: elongate-fusiform species with perched chomata, Group II: small, very slender-fusiform species with perched chomata, Group III: intermediate, thickly fusiformspecies with perched chomata, Group IV: large, thickly fusiform species with massivechomata). Pseudofusulinella hidaensis (Kanuma) probably belongs to Group I: Specieswith elongate-fusiform shell with perched chomata. This zone is possibly correlatedwith his Zone A and Zone 1 (Wilde, 1984). Ross (1984) noticed that Pseudofusulinella is sometimes accompanied by lower Permian Schwagerina, and these species ofPseudofusulinella may be relicts of their Carboniferous ancestors. Gobbett (1973)emphasized that Pseudofusulinella belongs to an element of the boreal fauna and theoccurrence is confined to the Lower Permian. Rui, Ross and Nassichuk (1991)discussed the paleobiogeography of late Moscovian (Desmoinesian) age and discriminated four climatic zones and fusulinacean provinces. They mentioned that bothWedekindellina and Pseudoendothyra are representative of the Arctic province, whereasBeedeina, Fusulina, and Neostaffella are characteristic genera of the Tethyan province.Beedeina was not found along AK Traverse and JI Traverse, and the problem of thefaunal province of the Pseudofusulinella hidaensis Zone and its detailed stratigraphicposition continues to be unclear. However, this zone is possibly correlated with thepreceding Fusulina-Beedeina Zone and the bed under the Zone 1 and Zone A by Wilde

68 Yasuhiro Ota

(1984).


This zone is characterized by the occurrence of Protriticites matsumotoi (Kanmera).The upper part of this zone in the first sequence contains Quasifusulinoides sp. A. Thedistribution of Quasifusulinoides sp. A is definite, so the present zone is tentativelysubdivided into two zones the lower, the Protriticites matsumotoi Zone (s. s.) and theupper, the Quasifusulinoides sp. A Zone.

2-(l). Protriticites matsumotoi Zone (s. s.)

This zone is defined by the occurrence of characteristic species, Protriticitesmatsumotoi (Kanmera). This zone is correlative with beds of other areas, bearingProtriticites. Davydov (1990) showed a lineage of Fusulinella- Protriticites-Montiparus-Rauserites and established the Protriticites pseudomontiparus-Obsoletes obsoletus Zone overthe Fusulinella bocki-Fusulina eopulchra-Fusulina cylindrica Zone. The Protriticites matsumotoi Zone is correlated with the Protriticites pseudomontiparus Zone (Davydov, 1990) fromthe associated fusulinaceans, such as Obsoletes obsoletus (Schellwien). Ross andRoss (1985b, 1988) recognized the Obsoletes obsoletus Zone under the Quasifusulinoides-Protriticites pseudomontiparus Zone. Ozawa and Kobayashi (1990) also discriminatedthe Obsoletes obsoletus Zone under the Protriticites subschwagerinoides Zone in the Akiyoshi

Limestone Group. In the AK area, Obsoletes obsoletus (Schellwien) was foundwithin the biohorizon of the first appearance of Protriticites matsumotoi (Kanmera).Watanabe (1991) established the Obsoletes obsoletus Zone which is correlative with the

Protriticites matsumotoi Zone (s. 1.). Davydov (1990) proposed that the boundarybetween the Middle and Upper Carboniferous should be drawn at the biohorizon

which is characterized by the first appearance of Protriticites. Rauser and Shcher-

bovich (1974) drew the boundary between the Moscovian and Kassimovian Stage at

the lower boundary of the Protriticites Zone. Ross and Ross (1985b, 1988) recognizedthe Fusulina cylindrica-Protriticites ovoides Zone under the Obsoletes obsoletus Zone.

The present Protriticites matsumotoi Zone (s. s.) is correlative with the lower part ofthe Protriticites pseudomontiparus-Obsoletes obsoletus Zone (Leven, 1979, 1980a, 1981;

Leven and Shcherbovich, 1978; Winkler, 1990), the lower part of the EowaeringellaZone (Wilde, 1984), the lower part of the Quasifusulinoides, Eowaeringella, OketaellaZone (Ross and Ross, 1985b, 1987, 1988), the lower part of the Protriticites subschwagerinoides Zone (Zhou et al., 1987), the lower part of the Protriticites-Obsoletesassemblage Zone (Zhang, 1983, 1991) and the lower part of the Obsoletes-MontiparusSubzone (Ding et al., 1991).

2-(2). Quasifusulinoides sp. A ZoneThis zone is tentatively defined by the first occurrence of Quasifusulinoides. The

name Quasifusulinoides was first introduced as Fusulina ex. gr. quasifusulinoides- Quasifusulinoides- Quasifusulina in the table of M. -Maklay, Rauser and Rozovskaya

(1958). After then, Quasifusulinoides was described by Rauser and Fursenko (1959)

with Pseudotriticites fusiformis Rozovskaya, 1952 as the type species. Chen (1963)


and Nikitina (1969) treated Quasifusulinoides as a subgenus of Fusulina. M. -Maklay(1963) considered this genus as a synonym of Pseudotriticites. According to Thompson (1964), the difference between Quasifusulina Chen, 1934 and Quasifusulinoidescannot be recognized. Sheng, Zhang and Wang (1988) noticed that Quasifusulinoides should be included in Fusulina. Rozovskaya (1975) treated Quasifusulinoides asa valid name, and Pseudotriticites as a synonym of Fusulina. Ueno (1991b) stated thatQuasifusulinoides could be distinguished from Fusulina by its wall with fine perforationand its younger stratigraphic occurrence than the latter. Ginkel and Villa (1991)agreed to treat Quasifusulinoides as Fusulina (Quasifusulinoides). In short, the differences between Fusulina and Quasifusulinoides were treated as those of subgeneric level.Collected specimens of Quasifusulinoides sp. A from AK Traverse have advanced wallwith tectum, "protheca" and inner tectorium, and the wall structure is similar to that

of the genus Fusulina. Thus Quasifusulinoides is considered to belong to Fusulininae.Furthermore, the stratigraphic occurrence is higher than that of Fusulina, becauseQuasifusulinoides sp. A was found above the level of the first appearance of Protriticitesmatsumotoi (Kanmera). As the distribution of this zone is narrow and restricted,detailed correlation is difficult. However, Davydov (1990) noticed the coccurrenceof Quasifusulinoides with Fusulinella and Protriticites, and he proposed the boundarybetween the Middle and Upper Carboniferous at a level of the first appearance ofProtriticites. Therefore, this zone is correlative with the Protriticites pseudomontiparus-Obsoletes obsoletus Zone. Ross and Ross (1985b, 1987, 1988) recognized the Quasifusulinoides Zone and Protriticites pseudomontiparus Zone over the Obsoletes obsoletus Zone inN. W. Europe, Moscow Basin and southern Ural. The present Quasifusulinoides sp.A Zone is correlated with the above Quasifusulinoides Zone and Protriticites pseudomontiparus Zone, and more probably with the upper part of the Protriticites pseudomontiparus-Obsoletes obsoletus Zone of Russia (Leven, 1980a, b, 1981; Leven and Shcherbovich,1978; Winkler, 1990), the upper part of the Eowaeringella Zone of U. S. A. (Wilde,1984), the upper part of the Quasifusulinoides, Eowaeringella, Oketaella Zones of thesouthwestern United State (Ross and Ross, 1985b, 1987, 1988), the upper part of theProtriticites subschwagerinoides Zone of South China (Zhou et al., 1987), the upper partof the Protriticites-Obsoletes assemblage Zone summarized by Zhang (1983, 1991), andthe middle part of the Obsoletes-Montiparus Zone of North China (Ding et al., 1991).


The Montiparus sp. A Zone is characterized by the occurrence of Montiparus, andcorrelated with the Montiparus Zone in other areas. Zhang (1984) divided thePermian in South China into the following three stages, based on the fusulinaceanwall structure.

(1). Pre-keriotheca stage (Fusulina: Dalan Stage).(2). Keriotheca stage (Montiparus, Triticites, Pseudoschwagerina, Sphaeroschwagerina,

Robustoschwagerina: a. Mapingian Stage; Pseudofusulina: b. Xiangzhongian Stage;Misellina: c. Qixian Stage; Cancellina, Neoschwagerina, Yabeina: d. Maokouan Stage).

70 Yasuhiro Ota

(3). Post-keriotheca stage (Codonofiisiella: a. Sanyangian Stage;Palaeofusulina: b.Changxingian Stage). Zhang insisted that the base of the Permian System shouldbe placed at the base of (2)-a: Mapingian Stage, and it was reasonable to draw theboundary based on the evolutionary stage, i.e. the development of keriotheca, andthis was suitable for establishing the biostratigraphic boundary. According toZhang (1984), the most primitive fusulinacean with keriotheca is Montiparus, but hedid not remark on Protriticites. The problems of the "Protriticites-type wall" stillremain in question. The present zone's leading fossil belongs to Montiparus, and thusthe zone is correlative with the Lower Permian Mapingian (Zhang, 1984), but thecorrelation based on the first appearanceof keriotheca is very difficult. Ross (1967,1973) pointed out that the rapid evolution of fusulinaceans in the Eurasian Arcticprovince had produced a series of early schwagerinid genera such as Protriticites,Montiparus, Obsoletes and Triticites. Triticites was considered to be the only genus ofthis series which had successfully invaded in the mid-continent province. In short,the genera Obsoletes, Protriticites and Montiparus are representative of the Eurasian-Andean province and therefore the direct correlation based on these genera is verydifficult among the other different faunal provinces.

The present Montiparus sp. A Zone corresponds to the following biohorizons byWilde (1984): Zone 2, Triticites planus, Eotriticites; Zone 3, Kansanella, Triticites ohioensis;Zone 4, Dunbarinella, Triticites beedei- moorei- plummeri, Waeringella, Rauserites}. Inaddition the following zones by Ross and Ross (1985b, 1987, 1988), probablycorrespond to the present zone: the Kansanella (Lowanella) winterensis and Triticites cf.ohioensis Zones; the Triticites ohioensis, Triticites collus, and Triticites nebraskensis Zones;the Triticites primarius and Kansanella neglecta Zones; the Triticites iatensis, Triticites newelliand Kansanella (Kansanella) joensis Zones; the Triticites mcgrewensis and DunbarinellaZones of the southwestern United State. The Montiparus montiparus Zone and theTriticites acutus-Triticites quasiarcticus Zone ofRussia (Winkler, 1990), the upper part ofthe Montiparus montiparus Zone and the overlying Triticites acutus-Triticites quasiarcticusZone of Russia (Popov et al., 1985; Chuvashov et al., 1986), the Montiparus montiparusZone and the overlying Triticites acutus-Triticites ardicus Zone in Russia (Leven, 1980a,b, 1981; Leven and Shcherbovich, 1978) are also correlative with the present zone.The Triticites montiparus Zone in South China (Zhang et al., 1987) and the Montiparusrange Zone or the Triticites acme Zone of Zhang (1983, 1991) are tentatively correlated with the present zone.

4. Triticites simplex Zone(s. 1.)The Triticites simplex Zone (s. 1.) comprises the tentatively discriminated two

zones: the lower, theSchwagerina sp. A Zone, and the upper, the Triticites simplex Zone(s. s.).

4-(l). Schwagerina sp. A ZoneThis zone is characterized by the abundant occurrence of Schwagerina sp. A.The stratigraphic significance of the genus Schwagerina was mentioned by many


authors, for example, Dunbar and Skinner (1936), Dunbar (1958), Ross (1963b),Skinner and Wilde (1965) and Rauser and Shcherbovich (1970). In 1954,opinion 213 designated the type species of Schwagerina sensu Moller, 1877 withBorelis princeps Ehrenberg, 1842= Ehrenberg, 1854 sensu Dunbar and Skinner,1936, non Schwagerina moelleri Rauser, 1937= Schwagerina princeps (Ehrenberg) sensuMoller, 1878. In Japan, many workers use the generic name Schwagerina sensu byDunbar and Skinner (1936, 1937), but internationally, two types and senses forSchwagerina are apparently present. In short, two species of the Schwagerina are usedfor the type species, namely Schwagerina moelleri Rauser, 1936= princeps (Ehrenberg,1942) sensu Moller, 1878, and Schwagerina sensu Moller, 1877, based on thereexamination of Borelis princeps Ehrenberg by Dunbar and Skinner (1936). Wilde(1984) maintained that Rugosofusulina Rauser, 1938 is a synonym of PseudofusulinaDunbar and Skinner, and numerous workers in C. I. S. had included Schwagerina inPseudofusulina. Zhang (1991) noticed that the first appearance of Schwagerina wasrecognized at the base of the Triticites stuckenbergi Zone in Russia. Therefore, thepresent Schwagerina sp. A Zone is correlative with the lower part of the Triticitesstuckenbergi Zone. Wilde (1984) correlated the Triticites-Schwagerina Zone with a partof Triticites (a part of C3b), Rauserites stuckenbergi (C3c), Jigulites (C3d) and Daixina(C3e). Sheng, Zhang and Wang (1988) regarded Daixina as a synonym ofSchwagerina sensu Dunbar and Skinner, 1936. From these facts, the first appearedbiohorizon ofSchwagerina probably corresponds to the base of'theDaixinafragilis Zone(Popov et al., 1985) and the Triticites stuckenbergi Zone in the other area. Rauser(1958) subdivided the Triticites arcticus-Triticites acutus Zone under the Triticites

stuckenbergi Zone into five units as follows: (1) the Triticites irregularis-Fusiella granum-oryzae unit; (2) the Triticites acutus- Triticites rossicus unit; (3) the Rugosofusulina unit; (4)the Triticitesfortissimus unit, and (5) the Triticites praeexilis unit. Of them, the Triticitesirregularis-Fusellagranum- oryzae unit contains Quasifusulina longissima (Moller). Fromthe similarity between the obtained Quasifusulina sp. A and Quasifusulina longissima(Moller), the present Schwagerina sp. A Zone possibly corresponds to the upperTriticites arcticus-Triticites acutus Zone or the biohorizon over the latter zone. How

ever, Quasifusulina sp. A has a more advanced form than Quasifusulina longissima(Moller), and the first appearance of Schwagerina seems to coincide with the lowerboundary of the Triticites siuckenbergi Zone. Taking this evidence into consideration,the Schwagerina sp. A Zone probably corresponds to the Triticites stuckenbergi Zone inother areas, or Zone 5, the lower part of the Triticites-Schwagerina Zone (Wilde, 1984),or the Triticites callosus, Triticites cullomensis and Triticites plummeri Zones (Ross andRoss, 1985b, 1987, 1988).

4-(2). Triticites simplex Zone (s. s.)

This zone is characterized by the following fusulinaceans (M. Ota, 1977):Triticites simplex (Schellwien), Triticites ozawai Toriyama, Triticites montiparus (Ehrenberg, 1854) sensu Moller, 1878, non Ehrenberg: Fusulina montipara (Moller, 1878)

72 Yasuhiro Ota

sensu Ozawa, 1925, Triticites biconicus Toriyama, Triticites suzukii (Ozawa), Triticites

noinskyi paula Toriyama, Triticites arctica (Schellwien), Quasifusulina longissima (Moller) and Schubertella kingi Dunbar and Skinner. The diagnostic species, Triticitessimplex (Schellwien) was not found along AK Traverse and thus this zone wasdivided by the other diagnostic fusulinaceans. In this paper, the Triticites simplexZone by M. Ota (1977) is divided into three zones, namely, the lower, the Montiparussp. A Zone, the middle, the Schwagerina sp. A Zone, and the upper, the Triticitessimplex Zone (s. s.). The Montiparus sp. A Zone probably corresponds to the strati-graphically lower biohorizon, bearing Triticites montiparus sensu Ozawa and Quasifusulina longissima (Moller). The Schwagerina sp. A Zone is correlated with thebiohorizon of Triticites biconicus Toriyama. The Triticites simplex Zone (s. s.) corresponds to the biohorizonof Triticites ozawai Toriyama. Therefore, the Triticites simplexZone (s. s.) in this paper is correlated with the upper part of the Triticites simplex Zone(M. Ota, 1977), a part of the Triticites-Schwagerina Zone, the upper of Zone 5, and 6(Wilde, 1984), and the Triticites subventricosus, Triticites whetstonensis, Schubertellawhetensis Zones, and the Leptotriticites americana, Triticites ventricosus, Schwagerina cf.Schwagerina longissimoidea Zones (Ross and Ross, 1985b, 1987, 1988).

5. Pseudoschwagerina muongthensis ZoneThe datum level of this zone is well defined by the first occurrence of the inflated

schwagerinid, Pseudoschwagerina. This zone is characterized by Pseudoschwagerinamuongthensis (Deprat) and the base coincides with the biohorizon bearing Pseudoschwagerina morikawai Igo. Hence, this biohorizon is correlated with that of the inflated schwagerinids.

Inflated schwagerinids have been studied by many paleontologists for a longtime. The following important studies on inflated schwagerinids should be mentioned: Dunbar and Skinner (1936, 1937), Dunbar (1958), Rauser (1959, 1960), M.-Maklay (1959), Ross (1962, 1963a, b, 1964, 1967, 1972a, 1973, 1982), Tikhvinskiy(1965), Rauser and Shcherbovich (1958, 1970), Sheng, Wang and Zhong (1984),Davydov (1984), Leven (1987) and Yang and Hao (1991). Dunbar and Skinner(1936) defined Schwagerina and established two new genera, namely, Pseudoschwagerinaand Paraschwagerina. Then, they designated Schwagerina uddeni Beede and Kniker,1924, as the type species of Pseudoschwagerina and remarked that the proloculus of thisgenus is commonly large, and the whorls of thejuvenarium are relatively short andthickly fusiform (pi. 11, figs. 6 and 7). Original designation of Schwagerina uddeniBeede and Kniker included both microspheric and megalospheric forms. Dunbarand Skinner (1936, plate 11, figs. 6-7; 1937, plate 50, figs. 1-10; 1937, plate 53, fig.8) regarded a typical form ofPseudoschwagerina uddeni (Beede and Kniker, 1924) sensuDunbar and Skinner as a megalospheric form, but Schwagerina uddeni Beede andKniker, 1924 originally includes the microspheric form also. In their description,Dunbar and Skinner (1936) expressed as "commonly large" for the proloculus, andthey implicitly recognized the existence of the microspheric form. Such being the


case, it is preferable that Pseudoschwagerina has both the two types microspheric andmegalospheric forms. Furthermore, the holotype of Pseudoschwagerina was designatedby Thompson (1948) with the specimen figured by Beede and Kniker (pi. 6, fig. 1,axial section of microspheric form). M. -Maklay (1959) classified SchwagerinidaeDunbar and Henbest, 1930 into 10 genera, recognizing Schwagerina Moller, 1877

and establishing new genera, namely Occidentoschwagerina and Sphaeroschwagerina (in

1956, Sphaeroschwagerina was originally proposed by M. -Maklay, but no description

was done.). Rauser and Shcherbovich (1958) recognized both PseudoschwagerinaDunbar and Skinner, 1936 and Schwagerina Moller, 1877. Rauser (1959) treated

Pseudoschwagerina Dunbar and Skinner, 1936 as distinct from Schwagerina Moller,

1877 based on the form of each juvenarium. Rauser (1960) subdivided Schwagerina

Moller, 1878 into five genera, and Zellia Kahler, 1937 into three groups. Inaddition, she established the new genus Parazellia with Fusulina muongthensis Depart,

1951 (pi. II, fig. 1) as the type species. Rauser and Fursenko (1959) also regardedSchwagerina Moller, 1877 as an independent genus and designated Schwagerinaprinceps sensu Moller, 1878 as the type species. Rauser and Shcherbovich (1970)

discussed characters of Schwagerina Moller, 1877 and they clearly distinguishedPseudoschwagerina Dunbar and Skinner from Schwagerina Moller.

As mentioned before the type species of Schwagerina sensu Moller, 1877 is Borelisprinceps Ehrenberg, 1842 without doubt. If Schwagerina moelleri Rauser, 1936 and

Schwagerina moelleri Rauser, 1949 are distinguishable from Schwagerina uddeni Beede

and Kniker, 1924, a new genus will be established for Schwagerina "moelleri" Rauser.Perhaps, the concept of the above new genus corresponds to that of AlpinoschwagerinaBensh, 1972. However, Alpinoschwagerina Bensh, 1972 is considered to be a synonymof Pseudoschwagerina Dunbar and Skinner, 1936. Sheng, Zhang and Wang (1988)

distinguished Sphaeroschwagerina M. -Maklay, 1959 from Pseudoschwagerina Dunbarand Skinner, 1936 by its having concave pointed poles and small proloculus.However, they treated Alpinoschwagerina Bensh as a synonym of Sphaeroschwagerina M.-Maklay, 1959. In addition, they emphasized that Schwagerina in Russia is the sameas Pseudoschwagerina Dunbar and Skinner. According to Loeblich and Tappan(1988), Sphaeroschwagerina can be distinguished from Pseudoschwagerina by its short axis.To the contrary, Alpinoschwagerina, which was established by its having a muchsmaller proloculus than that of Pseudoschwagerina, practically cannot be distinguishedfrom Pseudoschwagerina Dunbar and Skinner, 1936. In a word, Alpinoschwagerina represents the microspheric form of Pseudoschwagerina. On the other hand, Davydov(1984) studied the origin of "Schwagerina" and discussed two lineages, Biwaella?-Dutkevichites- Sphaeroschwagerina and Biwaella?- Biwaella. Then he proposed the subfamily Biwaellinae, and mentioned that the taxonomic homonym between "Schwagerina" and Pseudoschwagerina still continues. Moreover, he pointed out that theoverestimated "Schwagerina sensu Rauser" should be treated as Sphaeroschwagerina,which was applied to the inflated "Schwagerina" of M. -Maklay (1959). Leven

74 Yasuhiro Ota

(1987) noticed that among the group of "Schwagerina", Occidentoschwagerina, Paraschwagerina, Pseudoschwagerina and Zellia appeared in Asselian time, whereas Robustoschwagerina in Sakmarian time, and Orientoschwagerina appeared in Murgabian time.

Additionally, he mentioned about the origin of Schubertellidae Skinner, 1931 and

agreed with the Davydov's opinion in 1984, in which schubertellid was regarded asan ancestor of Biwaella. Davydov (1988b) regarded the occurrence of Schwagerinasensu Davydov (1988b) as being at the lower horizon of the Daixina (Ultradaixina)postsokensis Zone.

As a result, the collected megalospheric species at AK 26 along AK Traversewas discriminated as Pseudoschwagerina muongthensis (Deprat) because it has a relatively large proloculus, thick spirotheca and inflated outline. Loeblich and Tappan(1988) and Sheng, Zhang and Wang (1988) also regarded it as Pseudoschwagerina.In the AK area, the collected inflated schwagerinids with microspheric proloculus areclosely similar to a variation of Pseudoschwagerina morikawai Igo, 1957. Judging fromthe morphology of Pseudoschwagerina, the collected specimen was identifiable asPseudoschwagerina morikawai Igo. The present Pseudoschwagerina muongthensis Zone isapproximately correlated with the biozone between the first occurrence of inflatedschwagerinids and the occurrence of typical Pseudofusulina in other areas.

5. Pseudofusulina vulgaris ZoneThe characteristic speciesof this zone is Pseudofusulina vulgaris s. s. (Schellwien,

1909). Internationally, several variations of Pseudofusulina are present. Naoumovaand Rauser (1964) reported two different types of Pseudofusulina at different stratigraphic positions. Rauser (1951) reported a primitive type of "Pseudofusulina" faunafrom the "Pseudofusulina Horizon" (C3II) under the Schwagerina Horizon (C3III).According to this, Pseudofusulina ex. gr. vulgaris Schellwien, 1908, occurs from anolder horizon than the Schwagerina Horizon. Davydov (1988a, b), reexaminedpseudofusulinids and discussed their origin. Zhang (1983, 1991) made the biohorizon of the first appearance of the "Pseudofusulina" coincide with the lower boundaryof the Daixina sokensis Zone. If this is so, Pseudofusulina appears under the Pseudoschwagerina Zone. Pseudofusulina was first established by Dunbar and Skinner (1931)with Pseudofusulina huecoensis Dunbar and Skinner, 1931 as the type species. Pseudofusulina, at one time, was regarded as a synonym of Schwagerina (Dunbar and Skinner, 1936). Rauser (1937) proposed the new genus Rugosofusulina with Alveoli priscaEhrenberg em. Moeller as the type species. Thompson (1948) designated theholotype of Pseudofusulina huecoensis (plate 1, figure 5, Dunbar and Skinner, 1931).Rauser (1949) studied Pseudofusulina Dunbar and Skinner, 1931 and referredFusulina moelleri Schellwien, 1908 to Pseudofusulina. Since then, the confusion between Pseudofusulina and "Schwagerina" has continued. Skinner and Wilde (1965,1966) revised the definition of the genus Pseudofusulina, because of the existence ofrugosity in Pseudofusulina huecoensis Dunbar and Skinner, 1931. At the same time,they established the new genus Chalaroschwagerina characterized by having a distinct


phrenothecae. Rozovskaya (1975) treated Rugosofusulina Rauser, 1937 as a validgenus, but did not recognized Chalaroschwagerina Skinner and Wilde, 1965 becausethe latter genus was treated as a synonym of Pseudofusulina Dunbar and Skinner.Thompson (1964) accepted both Pseudofusulina Dunbar and Skinner and Rugosofusulina Rauser. In Loeblich and Tappan (1988) Rugosofusulina Rauser was treated asa synonym of Pseudofusulina Dunbar and Skinner, but Chalaroschwagerina Skinner andWilde, 1965 was treated as valid. Sheng, Zhang and Wang (1988) also recognized

both Pseudofusulina and Chalaroschwagerina as distinct genera. They additionallycommented that Chalaroschwagerina has a special form which is distinct from the genusPseudofusulina. They also pointed out that the sense of Pseudofusulina in Russia was amixed one of Schwagerina sensu Dunbar and Skinner (1936) and Pseudofusulina sensuDunbar and Skinner (1931). Consequently, the stratigraphic position and definition of "Pseudofusulina" are ambiguous and its correlation is very difficult at present.

According to Leven (1970), the following species are the index fusulinaceans ofUpper Artinskian time: Misellina (Brevaxina) dyhrenfurtki (Dutk.), Darvasites ordinatus(Chen), Darvasites contractus (Schellw. and Dyhr.), Rugosofusulina vulgariformis Kalm.,

Pseudofusulina kraffti (Schellw. and Dyhr.) and Pseudofusulina fusiformis (Schellw.

and Dyhr.), Pseudofusulina exigua (Schellw. and Dyhr.). Thus, the upper limit of

the present Pseudofusulina vulgaris Zone becomes older than the base of the UpperArtinskian. Leven (1975) insisted that the Sakmarian Stage with robustoschwager-inids and paraschwagerinids must be assigned to the deposits in the interval between

the lower, the Schwagerina Bed and the upper, the Pseudofusulina Bed with Pseudofusulina vulgaris-Pseudofusulina kraffti. Leven (1979) proposed that the Bolorian Stage is

divided into the upper, the Misellina parvicostata Zone and the lower, the Misellinadyhrenfurtki Zone. He mentioned that the Bolorian species, comparing with theirimmediate ancestors, have larger dimensions, and more intense and regular folding ofsepta and cuniculus. Furthermore, he concluded that the characteristic fusulina

ceans of the Pseudofusulina vulgaris Zone, the Pseudofusulina fusiformis Zone, and thePseudofusulina ambigua Zone (Kanmera and Mikami, 1965a, b), the Pseudofusulinaambigua Zone of Toriyama (1958) and the Pseudofusulina kraffti magna Zone, renamedby Hasegawa (1963), were similar to those which accompanied misellinids inDarvaz, and further more that the Parafusulina kaerimizensis Subzone with misellinids(Nogami, 1961) is probably correlated with the Upper Kubergandian Stage. Leven(1980b) correlated the Yakhtashian Stage, named after Mt. Yakhtash in Darvaz withthe Pseudofusulina vulgaris Subzone (Toriyama, 1958). Leven and Shcherbovich(1980) pointed out that Pseudofusulina vulgaris (Deprat) is a primitive species regardedas Chalaroschwagerina. From these facts and studies, the present Pseudofusulina vulgarisZone probably corresponds to the lower part of the "Chalaroschwagerina" vulgaris Zoneor the biohorizon under the latter zone (Leven and Shcherbovich, 1978), and thePseudofusulina vulgaris-Laxifusulina iniqua Zone (Zhou et al. 1987), the Pseudoschwagerinaconvexa, Pseudofusulina nelsoni, Schwagerina diversiformis, and Eoparafusulina Zones (Ross

76 Yasuhiro Ota

and Ross, 1985b, 1987, 1988).

-II-4. Conclusion

The investigated AK area was selected in front of the Akiyoshi-dai Museum of

Natural History, southern part of the Akiyoshi Plateaus (s. s.).Materials from 56 localities were collected along AK Traverse. 15 genera and

44 species of fusulinaceans were described. Limestones on AK Traverse are mainlycomposed of alternating beds with sparry calcite cements and micritic or micritematrices, and are intercalated with the black to dark brown colored limestones.

These limestones yield abundant fusulinaceans and algae, and interbedded with themare rather coarse limestones containing fragments of crinoids and bryozoans. Fromthese studies, the following six zones including tentatively discriminated four zones ina narrow sense are recognized along AK Traverse: 1. Pseudofusulinella hidaensis Zone,2. Protriticites matsumotoi Zone (s. 1.), 2-(l). Protriticites matsumotoi Zone (s. s.), 2-(2).Quasifusulinoides sp. A Zone, 3. Montiparus sp. A Zone, 4. Triticites simplex Zone (s. 1.),4-(l). Schwagerina sp. A Zone, 4-(2). Triticites simplex Zone (s. s.), 5. Pseudoschwagerinamuongthensis Zone, 6. Pseudofusulina vulgaris Zone. The distribution of these zonesindicates that the limestones in this area have a general northeastern strike and theyounger zones are successively distributed toward the northwest. Furthermore, thelimestones along AK Traverse are recognizableas the alternations of limestone of twodifferent sequences, probably caused by a fault of NE-SW trend (Ozawa andKobayashi, 1990). In addition, the tentatively discriminated Quasifusulinoides sp. AZone was not identified in the second sequence. The lower part of the overlyingMontiparus sp. A Zone is composed of limestones with sparry calcite cementscontaining characteristic fusulinaceans similar to those of the underlying zone,namely Protriticites matsumotoi (Kanmera). The transitions from Fusulininae orFusulinellinae to Schwagerininae are also recognizable between the Quasifusulinoidessp. A Zone or the Protriticites matsumotoi Zone (s. s.) and the Montiparus sp. A Zone.Thus, gaps might be present between the underlying Protriticites matsumotoi Zone (s. 1.)and the overlying Montiparus sp. A Zone. However, these gaps are interpreted as ofsmall scale, because genus level transitions between zones shift gradually asmentioned above. The recognized fusulinacean zones were attempted to be correlated with the biostratigraphic zones in the reference sections. The inflatedschwagerinids have a worldwide distribution and are very useful for internationalcorrelation of the Upper Carboniferous to Lower Permian. On AK Traverse, thePseudoschwagerina muongthensis Zone was characterized by the occurrence of Pseudoschwagerina muongthensis (Depart) and the base of this zone was defined by the firstoccurrence of Pseudoschwagerina morikawai Igo. The author tentatively made thebasal boundary coincide with the first occurrence of pseudoschwagerinids in otherareas.


-III-l. The third investigated area, Mt. Maruyama, Mine City, YamaguchiPrefecture

The third investigated area, Mt. Maruyama, is located in Mine City, YamaguchiPrefecture. In this chapter, the author would like to discuss the phylogeneticconsideration of the species relative to Protriticites yanagidai Ota and Protriticitesmasamichii Ota from the Mt. Maruyama area.

,200m-

Fusulinella simplicata Subzone(Kyuma and Nishida, 1987)

Fusulinella biconica Subzone(Kyuma and Nishida, 1987)

Yr-~->Profusulinella beppensisZone

<ry^: (Kyuma and Nishida, 1987)

Mt. Maruyama area

/

_170rn/

Fig. 26. Distribution of fusulinacean zones in the third investigated area, Mt. Maruyamawith a locality, MA 66.

78 Yasuhiro Ota

The Mt. Maruyama area is underlain by Middle to Upper Carboniferouslimestones, and these limestones generally have a northeast strike and a northwarddip. Furthermore, limestones of this area are regarded as reef facies deposits andcontain stromatolites and chaetetids (M. Ota, 1968). According to Kyuma andNishida (1987), the following zones are distributed in ascending order: the Profusulinella beppensis Zone, the Fusulinella simplicata Subzone and the Fusulinella biconicaSubzone (Fig. 26).

The author measured the section along the traverse, namely MA Traverse toclarify the localities of the collected fusulinids. Locality MA 66 yields the followingspecies: Protriticitesyanagidai Ota, Protriticites masamichii Ota, Protriticites toriyamai Otaand Protriticites aff. matsumotoi (Kanmera) mainly obtained from limestones withsparry calcite cements.

Limestones of the Mt. Maruyama area are composed of biomicrite to biomicru-dite, bryozoa-crinoid biosparite, and shell-crinoid biosparrudite. New species ofgoniatites were described in this area (Kyuma and Nishida, 1987). These sedimentary features suggest that the limestones in this area were formed in a paleoenvironment similar to the reef core in the Akiyoshi organic reef complex. Limestones nearLoc. MA 66 seem to have accumulated on a reeffiat of a bypass margin between thefore reef and open sea, because they yield fragments of ammonoids and fusulinaceans(Y. Ota, 1994).

Form ratio

2.00 .

1.00 4.00

Length(mm)

Fig.27. Each form ratio of the length to width. K: Protriticites afT. matsumotoi. M: Protriticitesmasamichii. T: Protriticites toriyamai. Y: Protriticitesyanagidai.

Fusulinacean Biostratigraphy of theAkiyoshi Limestone Group, Part I 79

-III-2. Phylogenetic ConsiderationThe collected species, Protriticites yanagidai Ota, Protriticites masamichii Ota,

Protriticites toriyamai Ota and Protriticites aff. matsumotoi (Kanmera), are characterizedby their small size, compared to the known species ofProtriticites. Each form ratio ofthe length to widthis shown in Fig. 27. Of these species, Protriticites toriyamai has thesmallest size shell. Protriticites yanagidai and Protriticites masamichii are almost thesame in size. Protriticites aff. matsumotoi is about twice as large as Protriticitesyanagidaior Protriticites masamichii. Protriticitesyanagidai Ota has a small, fusiform to ellipsoidalshell, with slightly and irregularly convex lateral slopes and somewhat sharplypointed poles. The present species is closely similar to Protriticites globulus Putrya,as the type species of the genus Protriticites. Furthermore, it resembles Protriticitesmatsumotoi, which was first described as Triticites (s. 1.) by Kanmera (1955). Therefore the phylogenetic line from Protriticites yanagidai Ota to Protriticites matsumotoi(Kanmera) is similar to the primitive species of Triticites (s. 1.). On the other hand,Protriticites masamichii Ota resembles Montiparus matsumotoi infktus, reported byWatanabe (1991) in having moderately inflated, oval to subspherical shell.Furthermore, this species is similar to the illustration of Montiparus montiparus shownby Rozovskaya (1950). Here, Protriticites masamichii Ota and Montiparus matsumotoiinfktus of Watanabe (1991) are probably linked together with a phylogenetic line(Fig. 28). From these viewpoints, Protriticites yanagidai is considered to be in aprimitive stage of the phylogenetic lines towards Protriticites matsumotoi, while Protriticites masamichii seems to be a transitional species to Montiparus matsumotoi inflatus.

In the investigatedJigoku-dani area, the limestones bearing Protriticites masamichiiin the Protriticites toriyamai Subzone are successively overlain by limestones withProtriticites matsumotoi (Kanmera) in the Protriticites matsumotoi Subzone. From thisfield evidence and the morphological affinities, Protriticites matsumotoi is considered tobe derived possibly from the primitive species of Protriticites, namely Protriticites tori

yamai, Protriticites masamichii and Protriticitesyanagidai. On the other hand, limestonesof the Protriticites matsumotoi Subzone are successively overlain by limestones withMontiparus sp. A in the Montiparus sp. A Zone at the Jigoku-dani area. In the AKarea, the Protriticites matsumotoi Zone (s. s.) are overlain by the Montiparus sp. A Zonewith small gaps, but the limestones are in nearly complete succession. Montiparus sp.A is closely similar to Montiparus matsumotoi inflatus of Watanabe (1991). Therefore,Montiparus sp. A and Montiparus matsumotoi infktus sensu Watanabe are possiblyderived from the primitive species of Protriticites, but it is uncertain whether Protriticitesmatsumotoi is directly connected with above species of Montiparus. Incidentally,Montiparus matsumotoi inflatus of Watanabe (1991) was mainly reported from the OmiLimestone, whereas Protriticites matsumotoi is from the Yayamadake Limestone. Theabove speciations and phyletic transitions might have resulted from the geographicisolation between the Akiyoshi Limestone, the Yayamadake and Omi Limestones.However, the Akiyoshi Limestone yields these fusulinaceans as mentioned above and

80

Yayamadake

Yasuhiro Ota

Geographic Speciation ?or

Chronologic speciation 7

Omi

Fig. 28. Phylogenetic consideration. 1. Protriticites yanagidai Y'. Ota. 2. Protriticites globulusPutrya. 3. Protriticites matsumotoi (Kanmera). 4. Protriticites masamichii Y. Ota. 5, 7.Montiparus matsumotoi inflatus, reported from Watanabe (1991). 6. Montiparus montiparusfrom Rozovskaya (1950). 8. Obsoletes obsoletus (Schellwien).

nearly complete successions of limestones from the Protriticites Zone to the MontiparusZone are confirmed without a remarkable hiatus. Hence, the above speciations andphyletic transitions have a great possibility to be the result of chronological specia-tion. Furthermore, the collected species from the Mt. Maruyama area have closeaffinities with Protriticites praemontiparus Zhou, Sheng and Wang, 1987 and Protriticitesminor Zhou, Sheng and Wang, 1987 from eastern Yunnan, South China. Thefusulinaceans in the Akiyoshi organic reef complex probably are closely related tothose of South China during this period.


Consideration

The purpose of this study is to reexamine the Middle Carboniferous to theLower Permian fusulinacean biostratigraphic units in the Akiyoshi Limestone Group.The details are shown in the previous chapters. Here the author would like tosummarize the paleontology of the Jigoku-dani, AK and Mt. Maruyama areas, whichrespectively contain the characteristic fusulinacean fauna, reflecting slight differencesof paleoenvironmental character.

Jigoku-dani area, AK area in front of Akiyoshi-dai Museum of Natural History,and Mt. Maruyama area were selected and the field investigations were carried out.

First investigated area, Jigoku-dani is located in the northwestern part of theAkiyoshi Plateau (s. s.). The inverted limestones of Middle Carboniferous to theLower Permian are widely distributed in this area. The studies in this area, lead tothe following conclusions: The collected materials from the measured sections, JITraverse comprise 56 fusulinacean species including two subspecies and 23 genera.From the fusulinacean constituents and distinctions of lithofacies, limestones were

tentatively divided into nine zones including seven subzones from the MiddleCarboniferous to the Lower Permian. These zones are well traceable in this area.

They are as follows: 1. Fusulinella biconica Zone; 2. Fusulina cf. shikokuensis Zone, 2-1.Fusulinella cf. obesa Subzone, 2-2. Pseudofusulinella hidaensis Subzone; 3. Obsoletesobsoletus Zone, 3-1. Protriticites toriyamai Subzone, 3-2. Protriticites matsumotoi Subzone;

4. Montiparus sp. A Zone; 5. Triticites yayamadakensis Zone, 5-1. Triticites sauriniSubzone, 5-2. Schwagerina sp. A Subzone, 5-3. Triticites biconicus Subzone; 6.

Schwagerina (?) cf. satoi Zone; 7. Pseudoschwagerina muongthensis Zone; 8. Pseudofusulinavulgaris globosa Zone; 9. Pseudofusulina aff. ambigua Zone. Distribution of these zonesindicates that limestones are inverted in structure. They are composed mainly of

micritic limestones without frame building organisms. The limestone facies suggest

that they were deposited in a relatively low energy environment like a lagoon within

the Akiyoshi organic reef complex. Furthermore, they were successively accumu

lated without a remarkable hiatus, because no remarkable faunal break could be

observed in the limestone sequence. Considerable facies changes are present near

the basal boundaries of the Schwagerina (?) cf. satoi Zone and the Pseudoschwagerina

muongthensis Zone. Limestones near the basal boundary of the Schwagerina (?) cf. satoi

Zone intercalate fairly coarse grainstones with fragments of reef frame builders and

the fusulinacean diversity becomes larger across the boundary. Limestones near thebase of the Pseudoschwagerina muongthensis Zone consist of rather coarse grainstoneswith the sparry calcite cement. In this paper, the author tentatively correlates the

limestones of the Jigoku-dani area with Middle Carboniferous to Lower Permianstrata in other areas of Japan and outside Japan by using the first occurrence of the

inflated schwagerinids, i.e. Pseudoschwagerina. The inflated schwagerinids are veryuseful to correlate the Upper Carboniferous and the Lower Permian, because they are

82 Yasuhiro Ota

widely distributed in many regions and are assumed to be planktonic during a part oftheir life cycle. They seem to be excellent index fossils for the correlation of theUpper Carboniferous to the Lower Permian. However, they are also known to occurin distinctive facies, such as biohermal limestones. Therefore, for regional correlation, examination of the associated fossils along with the inflated schwagerinids isindispensable.

The second investigated AK area is located in front of the Akiyoshi-dai Museumof Natural History. AK Traverse was measured and fossils collected along thetraverse. From the paleontological and lithological viewpoints, the following fusulinacean zones are tentatively discriminated in ascending order: Pseudofusulinellahidaensis Zone, Protriticites matsumotoi Zone (s. s.), Quasifusulinoides sp. A Zone,Montiparus sp. A Zone, Schwagerina sp. A Zone, Triticites simplex Zone (s. s.),Pseudoschwagerina muongthensis Zone and Pseudofusulina vulgaris Zone. Detailed fieldmapping of the area revealed two limestone sequences cut by a fault of northeasterntrend in this area. Limestones appear to have accumulated in a marginal lagoonenvironment in the Akiyoshi organic reef complex.

The Mt. Maruyama area in Mine City, Yamaguchi Prefecture, is the thirdinvestigated area. The limestone facies of this area indicate that the paleoenvironment is probably a true reef within the organic reef complex. Loc. MA 66 wasexamined in detail and the following fusulinaceans were identified: Protriticitesyanagidai Ota, Protriticites masamichii Ota, Protriticites toriyamai Ota and Protriticites aff.matsumotoi (Kanmera). These species are characterized by having rather small shell,as compared with the known species of Protriticites. From their morphologicalcharacters, two phylogenetic lines were shown among the primitive Triticites (s. 1.).The first line is from Protriticites yanagidai Ota to Protriticites matsumotoi (Kanmera).The second one is from Protriticites masamichii Ota to Montiparus matsumotoi infktus,reported by Watanabe (1991). From hypothesis based on the morphologicalaffinities, Protriticitesyanagidai seems to be a primitive stage in the first line, whereasProtriticites masamichii is considered to be a transitional species in the second line.The transition from Protriticites masamichii to Protriticites matsumotoi in association with

Protriticites toriyamai is successively confirmed in the Protriticites toriyamai Subzone tothe Protriticites matsumotoi Subzone in the Jigoku-dani area. Therefore, Protriticitesmatsumotoi (Kanmera) seems to be linked to the above primitive species of Protriticites.Furthermore, the Montiparus sp. A Zone, though small gaps were present, conformably overlies the Protriticites matsumotoi Subzone or Zone along AK and JI Traverses.Therefore, the relevant species of Montiparus sp. A and Montiparus matsumotoi infktusof

Watanabe (1991) are probably linked to the primitive species of Protriticites, but it isdoubtful whether Protriticites matsumotoi (Kanmera) is directly connected with Montiparus matsumotoi infktus sensu Watanabe, because of its morphological characters. Inaddition these fusulinaceans are closely similar to Protriticites praemontiparus Zhou,

Sheng and Wang, 1987 and Protriticites minor Zhou, Sheng and Wang, 1987,


respectively from eastern Yunnan, South China. The examinations of the fusulinacean affinities between China and Japan are very important for studying paleo-biogeography during Carboniferous-Permian time.

The tentative divisions of the fusulinacean zones proposed for the MiddleCarboniferous and Lower Permian Akiyoshi Limestone Group and the relevantsections are shown in Fig. 17. As mentioned before, it is very difficult to obtain aconsensus on the leading and index fusulinaceans of each zone even in the AkiyoshiLimestone. This seems to be caused mainly by the differences of the originalhabitats and the fusulinacean ecological adaptations and has a close relationship withthe paleoecology in the Akiyoshi organic reefcomplex (e.g. M. Ota, 1968; Nagai andM. Ota 1980; Nagai, 1985). M. Ota (1977) already mentioned that habitatsegregation is observable with the fusulinacean distribution in the Akiyoshi Limestone, namely Pseudofusulina kraffti magna Toriyama in the lagoonal facies andPseudofusulina ambigua (Deprat) in the sand facies of the reef flat environment.

The following paleoecology studies were well known before. Ross (1961, 1965,1969, 1972b) tried to establish biostratigraphic zones, by considering their paleoenvironment. He remarked that fusulinaceans lived on the surface of the substratum

and have adapted to the influence of water conditions, such as temperature, salinity,currents and turbidity. Ross (1964) suggested that the morphological changes weredue to ecological adaptation, for example, the inflated schwagerinids occur in specificrock types, such as patch reef accumulations or bioherms. Tikhvinskiy (1965)insisted that the elongated and fusiform genera of Schwagerininae were undoubtedlybottom dwellers, but some genera with inflated form probably had a planktonic

habit. Menner (1971) criticized the above opinions because it was very difficult to

confirm whether the genus "Schwagerina" is planktonic or benthonic. Ross (1972b)reconstructed the isolated bioherms in the lower Wolfcampian Neal Ranch Formation, and discussed the fusulinacean habitats. According to him, the inflatedschwagerinids, including Pseudoschwagerina uddeni (Beede and Kniker), have a

distribution near the biohermal buildups and on associated debris aprons. Moreover, Ross (1982) insisted that some genera in the inflated schwagerinids had aplanktonic phase in the life cycle. Ross and Ross (1988) and Seslavinskiy (1991)made it clear that during late Carboniferous and early Permian time, transgression

shifted to regression. Furthermore, Ross and Ross (1988) suggested that thesedimentary environment from the base to upper part of the Wolfcampian changes

from shelf to basin. Sea level changes may closely relate to the worldwide dispersalof the inflated schwagerinids.

The sedimentary environments of the Akiyoshi Limestone Group in the investi

gated AK Traverse were, as a whole, reconstructed as like a marginal lagoon within

the Akiyoshi organic reef complex. The Jigoku-dani area is recognizable as a

relatively low energy environment like a lagoon. The Mt. Maruyama area, on thecontrary, reveals an environment near the reef core, according to the biofacies and

84 Yasuhiro Ota

lithofacies.

Along AK Traverse, well preserved Pseudoschwagerina were obtained from micriticlimestone. The collected specimens of Pseudoschwagerina from AK Traverse, areconsidered to be preserved in the original living position and form. Machiyama andKawamura (personal communication), examined the biohorizon of Pseudoschwagerinaalong AK Traverse and concluded that the energy level of that environment was verylow because of abundant occurrence of wackestone. In contrast with the AK area,Pseudoschwagerina in theJigoku-dai area rarely occurs in limestones with sparry calcitecements and is poorly preservation. Under high energy condition, Pseudoschwagerinaseems to be difficult to preserve well, because of its thin and not very strong walls.Pseudoschwagerina in the Akiyoshi organic reef complex probably chose its habitat inthe marginal lagoon environment and sometimes extended into the central environment of the lagoon.

The Triticites-Schwagerina Zone (s. s.) outside the Akiyoshi region, approximatelycorresponds to the Triticites yayamadakensis Zone and the Triticites simplex Zone alongAK and JI Traverses. These zones in the investigated areas are typified bydominance of Triticites (s. s.) and are also characterized by abundance of Schwagerinasp. A along two traverses. Triticitesyayamadakensis Kanmera is abundant and easilytraced in the Jigoku-dani area, but this species is rare along AK Traverse. Triticitesozawai Toriyama, a closely related species to Triticitesyayamadakensis Kanmera occursalong AK Traverse. Fusulinacean constituents of these zones along AK and JITraverses are slightly different, but the above zones also yield many mutualfusulinaceans.

The Montiparus sp. A Zone is confirmed in both AK and Jigoku-dani areas. Thelower part of the Montiparus sp. A Zone along AK Traverse is accompanied by theunderlying diagnostic Protriticites matsumotoi (Kanmera). This species might beregarded as a member of a "ghost fauna" or the mixed fauna derived from variouszones, resulting from condensation by sea level changes. Hence, gaps are possiblypresent between the overlying Montiparus sp. A Zone and the underlying Quasifusulinoides sp. A Zone in the Protriticites matsumotoi Zone (s. 1.). Furthermore, the horizonof the gaps coincides with the biohorizon, changing from Fusulininae or Fusulinellinae to Schwagerininae. Consequently the geological event, suggested by the gaps,is considered to play an important role in the transition from Fusulininae orFusulinellinae to Schwagerininae. However, Ross (1989) has already pointed outthat the time for fusulinacean transitions in such a condensed section is too short to

be reason for the evolution of fusulinaceans. Therefore, the rapid transitions fromFusulininae or Fusulinellinae to Schwagerininae observed along AK Traverse aredependent on the original evolutionary cause, which fusulinaceans possess ratherthan that caused by paleoenvironmental change. Hasegawa (1963, 1988) discussed

the origin of the black sparry calcite limestone near the boundary between theCarboniferous and Permian. According to him, the datum level of the lower limits


of the black sparry calcite limestone coincides with the biohorizon, where theFusulina-Fusulinella fauna extinguishes, and the new Triticites (s. 1.) fauna appears.From its chemical composition, this black to dark brown color limestone is not

dolomitic, and changes of sedimentary environments are suggested (Musashino,Hikabe and Arai, personal communication). It is possible that the black to darkbrown color limestone along AK Traverse is the product of a geological event, thattook place after the limestone accumulations of the Quasifusulinoides sp. A Zone.

The Protriticites matsumotoi Zone in the investigated areas was first introduced byM. Ota (1977) as the Triticites (s. 1.) matsumotoi Zone, and is characterized byprimitive species of Triticites (s. 1.), such as Protriticites matsumotoi (Kanmera). Inconnection with this zone, Minato, Kato, Nakamura, Niikawa and Hasegawa

(1984) reported that Protriticites matsumotoi (Kanmera) was widely found in SouthwestJapan. Hasegawa (1988) also reported that the Triticites simplex fauna partlyoverlies in occurrence the rather primitive Triticites (s. 1.) fauna, such as Protriticitesmatsumotoi fauna. He assumed that the primitive Triticites (s. 1.) was probably able tosettle only in the area, where conditions suitable for fusulinacean recovery arrivedearly in the environmental change. Of the study areas, AK Traverse and JITraverse are supposed to be the presumably recovered areas for them, because arather primitive Triticites (s. 1.) fauna, such as Protriticites matsumotoi fauna, was found.

The Fusulina-Fusulinella Zone, comparable with the Beedeina akiyoshiensis Zone ofM. Ota (1977) was not confirmed along AK Traverse and in the Jigoku-dani area.Beedeina akiyoshiensis (Toriyama) is known in limestones with sparry calcite cements,accumulated in a reef environment. Therefore, it is suggested that Beedeinaakiyoshiensis (Toriyama) originally could not live in a relatively low energy environment like along AK and JI Traverses, where the central to marginal lagoonenvironment was predominant.

As mentioned above, in the Akiyoshi Limestone Group the Middle Carboniferous and Lower Permian fusulinaceans of each zone are slightly different in their composition in different areas. This fact suggests that some fusulinaceans have distinctive habitats different from others in the Akiyoshi organic reef complex. Thesedistributional characters control the local bio-divisions and fusulinacean zonations.

Hence, the analysis of the fusulinacean assemblages, relating to their specialdistribution habitat in the Akiyoshi organic reefcomplex, is essential to establish thedetailed biostratigraphic division in the future.

The establishment ofdetailed biostratigraphic units is very important for makingclear the process of formation of the Akiyoshi organic reefcomplex and is essential tolearning the paleogeography of Japan in late Paleozoic time. In this connection,Hill (1973) referred to the relation between the sedimentary environment of theorganic reef and the paleolatitude. In fact, Japanese Islands in late Paleozoic timewas formerly illustrated in many paleogeographic maps nearly at the north latitudeof60° in the Arctic region (e.g. Smith et al. 1973; Boucot and Gray, 1980). Taking

86 Yasuhiro Ota

the Akiyoshi organic reef complex (e.g. M. Ota, 1968; Nagai, 1978, 1979; Sugiyama

and Nagai, 1990) and modern coral reef into consideration, the above location of the

late Paleozoic Japanese Islands, including Akiyoshi region, is unsuitable with present

knowledge. Ross and Ross (1985a) and Scotese and Mckerrow (1990) showed thelocation of the Japanese Islands in late Paleozoic time near the equator. Theirconclusions agree with the results of the present study.

With regard to the changes of fusulinacean genera along AK and JI Traverses,

the following generic transitions are confirmed: Pseudofusulinella- Protriticites-Montiparus- Triticites (Schwagerina)- Pseudoschwagerina- Pseudofusulina. The genus

Pseudofusulinella was first introduced by Thompson (1951) and is considered to haveoriginated from Fusulinella, in the Eurasian Arctic faunas at about the end of lateCarboniferous time (Ross, 1973). According to Rui, Ross and Nassichuk (1991),

the Tethyan province, namely tropical and subtropical climatic zones, is marked bythe transitional series of Fusulinella-Neostaffella-Beedeina-Fusulina fauna. Therefore,during the period of the Pseudofusulinella Zone, corresponding to the Fusulina andBeedeina Zones, the Akiyoshi organic reef complex was formed in a subtropical andtropical environment rather than just an area with a warm temperature. Additionally, the faunal transition from the Protriticites Zone to the Montiparus Zone wasconfirmed along AK and JI Traverses. As respects Triticites (s. 1.), many authors,for examples, Davydov (1990) and Ginkel and Villa (1991) have discussed itbefore. The successive transition from Protriticites to Montiparus has been confirmedin the Tethyan province but not in the Mid-continent province. Hence, the Tethyanfaunal province during the time from the Protriticites matsumotoi Zone to the Montiparussp. A Zone seems to have little connection with that of the Mid-continent faunalprovince. The Pseudoschwagerina muongthensis Zoneis characterized by the widespreadgenus, Pseudoschwagerina. This genus is considered to be planktonic during a part ofits life cycle. In a strict sense, the development of the Pseudoschwagerina muongthensisfauna in the Akiyoshi Limestone Group possibly has a time lag in comparison withthat of Pseudoschwagerina uddeni (Beede and Kniker) in the Mid-continental province,because the pseudoschwagerine faunas arose in western NorthAmerica and after thatthey dispersed and migrated into the Tethys ocean. However, this dispersal timewas short and we can adapt synchronism to the migration rapidity of Pseudoschwagerina. This is the reason why Pseudoschwagerina is very useful for worldwide correlation.The next overlying Pseudofusulina Zone is characterized by a cosmopolitan genus,Pseudofusulina. However, the stratigraphic distribution and definition of this zone arestill left in question.

Acknowledgments

The author expresses his grateful thanks to Professor Juichi Yanagida, KyushuUniversity, who kindly read the manuscript and offered many helpful suggestions to

Fusulinacean Biostratigraphyof the Akiyoshi Limestone Group, Part I 87

accomplish this study. Cordial thanks are due to Professor Hakuyu Okada andAssociate Professor Akihiko Matsukuma, Kyushu University, for reading themanuscript and their giving the author helpful criticisms and suggestions during thecourse of this study. The author also wishes to express his grateful thanks toProfessor Kimiyoshi Sada, Hiroshima University, who kindly read the manuscriptand provided many suggestions about fusulinaceans. Dr. Kametoshi Kanmera,Professor Emeritus, Kyushu University gave him many valuable comments andhelpful suggestions on the fusulinacean paleontology. Dr. Wilbert R. Danner,Professor Emeritus, University of British Columbia, kindly read the manuscript andmade minor changes in grammar and syntax where needed, and provided usefulcomments and suggestions. Dr. Masamichi Ota, Director of the KitakyushuMuseum and Institute of Natural History critically read the manuscript and offeredmany valuable comments and helpful suggestions. The author thanks the followingpersons for their kind help in giving him facilities in field work and valuablesuggestions; Professor Tamio Nishida, Saga University, Assoc. Prof. Koichi Nagai,Ryukyu University, Assoc. Prof. Testuo Sugiyama, Fukuoka University, Dr.Kyoichiro Ueda, Curator of the Kitakyushu Museum and Institute of NaturalHistory, Messrs. Akihiro Sugimura and Takehiko Haikawa, Akiyoshi-dai Museumof Natural History and Mrs. Yuko Kyuma, Primary School of Nagasaki Prefecture.

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Middle Carboniferous and Lower Permian Fusulinacean ... · Middle Carboniferous and Lower Permian Fusulinacean Biostratigraphy of the Akiyoshi Limestone Group, SouthwestJapan. Part