lower cretaceous calcareous algae and foraminifera from trbušnica

ACTA PALAEONTOLOGICA ROMANIAE (2014) V. 10 (1-2), P. 95-104

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1 Babeş-Bolyai University, Department of Geology and Center for Integrated Geological Studies, str. M. Kogălniceanu nr. 1,

400084 Cluj-Napoca, Romania. [email protected] 2 Faculty of Ecology and Environmental Protection, Department of Geology, Union-Nikola Tesla University, Cara Dusana 62-64, 95

11 000 Beograd, Serbia. [email protected] 3 Kralja Petra I, 38, 11158 Beograd, Serbia. [email protected]

LOWER CRETACEOUS CALCAREOUS ALGAE AND FORAMINIFERA FROM

TRBUŠNICA (VARDAR ZONE, SERBIA)

Ioan I. Bucur1, Svetlana Polavder2 & Rajka Radoičić3

Received: 15 September 2014 / Accepted: 12 November 2014 / Published online: 18 November 2014

Abstract The basal part of the Miocene sedimentary deposits from Trbušnica region (south-west of Belgrade, Serbia,

Vardar zone) consists of conglomerates containing pebbles of Mesozoic limestones. The study of two of these

pebbles led to the identification of an interesting assemblage of dasycladalean calcareous algae with Andreiella

rajkae, Montiella elitzae, Neomeris sp., Salpingoporella muehlbergii, Salpingoporella gr. pygmaea, Salpingoporella

sp., Suppiluliumaella gr. polyreme, ?Suppiluliumaella sp., Suppiluliumaella sp., Triploporella sp. and Zittelina

hispanica. Foraminifera accompany this algal association: in one of the samples Montseciella arabica is dominant,

while the other one contains orbitolinid fragments (possibly Palorbitolina lenticularis). The two orbitolinids point to

a Late Barremian – earliest Aptian (early Bedoulian) age for the studied limestone pebbles.

Keywords: orbitolinids, dasycladaleans, Lower Cretaceous, Serbia

INTRODUCTION AND GEOLOGICAL SETTING

The study area is located southwest of Belgrade, between

Rudovci and Trbušnica localities where Neogene deposits

(Middle Miocene and Pliocene) crop out (Fig. 1, based on

Filipović et al., 1976, geological map 1: 100000, sheet

Obradovac). In the area located between the Bistrička

River and Trbušnica Upper Cretaceous (“Senonian”)

rocks are topped by basal Miocene conglomerates.

These conglomerates contain numerous calcareous

pebbles assigned to the Jurassic or Cretaceous, besides

Paleozoic metamorphic ones. Locally, the composition of

the pebbles is dominated by gabbro, diabase, pyroxenite

and serpentine, imprinting a characteristic feature of these

deposits. The conglomerates are overlain by coarse or

fine sandstones, and rarely by marls with coal interbeds

(Fig. 2).

The conglomerates cropping out in the Trebušnica area

Fig. 1 Geological map of the Trbušnica area (modified from Filipović et al., 1976). The star indicates the location

of the samples; 1. Igneous rocks; 2. Metamorphic rocks; 3.Upper Cretaceous (“Senonian”); 4.Middle Miocene;

5.Pliocene; 6.Fault

mailto:[email protected]

Ioan I. Bucur, Svetlana Polavder & Rajka Radoičić

96

contain numerous limestone pebbles of Early Cretaceous

age, some with microfossil content that can be identified.

We have studied 10 thin sections obtained from two

samples (sample RR013234, thin sections RR4523,

RR4524, RR4525, RR4527, and sample RR013205, thin

sections RR4516, RR4517, RR4518, RR4519, RR 4520

and RR4521). The present paper briefly describes the

calcareous algae and the foraminifera identified in this

material, in order to more closely understand the age

relationships of the pebbles. The samples are part of

Rajka Radoičić’s private collection.

Fig. 2 Succession of the Miocene rocks from Trbušnica area

(modified from Filipović et al., 1976).

MICROFACIES

Three microfacies types have been defined in the

investigated pebbles.

1. Bioclastic coarse grainstone/rudstone with

Montseciella (Fig. 3 a-c). Fragments of corals, bivalves,

gastropods and echinoderms, calcareous algae and

foraminifera are the main biogenic components.

Additionally, rivulariacean-type cyanobacteria,

Bacinella-type structures, oncoids with micritic cortex

and neoformed quartz – the latter mainly located in the

oncoids' cortexes – were also identified. They are

accompanied by dasycladalean algae, rare udoteacean

algae (Arabicodium sp.) and foraminifers – among which

Montseciella is dominant. Locally, lithoclasts of

sandstones, crystalline limestones or siliceous rocks are

present.

2. Bioclastic rudstone with Zittelina (Fig. 3 d). It contains

large coral fragments, sclerospongia fragments, bivalves,

gastropods and echinoderms, dasycladalean algae,

Bacinella-type structures and orbitolinids, which

agglutinate large amounts of terrigenous quartz.

3. Bioclastic rudstone/floatstone with Triploporella (Fig.

3 e, f). It includes fragments of corals, sponges, bivalves

and echinoderms. The corals are sometimes encrusted by

red algae (Polystrata alba and Sporolithon rude).

Besides, we have identified encrusting foraminifers,

fragments of orbitolinids, nodosariids, dasycladalean

algae and the microproblematicum Carpathoporella.

FORAMINIFERA

The studied Lower Cretaceous pebble samples contain

numerous sections of the orbitolinid Montseciella arabica

(sample RR013235). Additionally, rare specimens of

Charentia cuvillieri, Everticyclammina sp.,

?Palorbitolina lenticularis (sample RR013234),

miliolids, nodosariids and other non-identified

foraminifers were found.

Genus Montseciella Cherchi & Schroeder, 1999

Montseciella arabica (Henson, 1948) Schroeder et al.,

2002

Fig. 4 a-l.

Description. Conical test (Fig. 4 a-e), 1.0-2.3 mm in

diameter and 1.0-1.8 mm in height, displaying about 14

chamber layers per millimeter in the axial-sub-axial

plane. We did not observe embryos, with the possible

exception of the specimen illustrated in Fig. 4 l where the

presence of an eccentric one might be assumed. An

eccentric embryo location is also suggested by the overall

configuration of the apical area of the specimen in Fig. 4

e.

One of the typical features for this species is represented

by the rudimentary radial partitions in the external part of

the central area, as extensions of the marginal chambers'

separating walls (Fig. 4 g, h, k) (Schroeder & Cherchi,

1979; Baud et al., 1994; Cherchi & Schroeder, 1999;

Maksoud et al., 2014). Especially based on this feature,

Schroeder et al. (1968) have assigned this species

originally ascribed to Dictyoconus by Henson (1948) to

the genus Paleodictyoconus. Subsequently, Schroeder et

al. (2002) have transferred it to the genus Montseciella.

The inner part of the central area is separated by pillars

displaying vermicular or pillar-like structures (Fig. 4 g,

k). The pillars alternate from one chamber layer to

another (Fig. 4 a-f). The chamberlets from the marginal

area are subdivided by one rather short horizontal plate

(Fig. 4 a-f) and one or two vertical ones (Fig. g-i, k), the

result being the formation of sub-epidermal chamberlets

(Fig. 4 j). The apertural pores with diagonal display are

visible in the subaxial (Fig. 4 a-f), as well as in the

oblique (Fig. 4 h) or the transversal-oblique sections (Fig.

4 g, k).

Remarks. In a recent publication, Schroeder et al. (2010)

have summarized the existing data and revised the

biostratigraphical zonation based on orbitolinids, as well

as on the phyletic lineages of Barremian-Aptian

orbitolinids. Accordingly, the Barremian-Aptian interval

was divided into six zones and three subzones.

Montseciella arabica is present in deposits covering

Lower Cretaceous calcareous algae and foraminifera from Trbušnica (Vardar zone, Serbia)

97

Fig. 3 Microfacies of the Lower Cretaceous limestone pebbles from Trbušnica. a-c Coarse grainstone to rudstone

containing bivalve, gastropod and echinoderm fragments, rare coral fragments, cortoids and bacinellid oncoids as well

as rare metamorphic, siliceous and sandy lithoclasts. Neoformation quartz is preferentially located in the micritic

cortex of some oncoids. Large dasycladaleans (Andreiella, Suppiluliumaella) and orbitolinid foraminifera

(Montseciella) are present; a, thin section RR4516; b, c, thin section RR4518. d Bioclastic rudstone with bivalve,

gastropod, echinoderm, sponge and rare coral fragments. Reworked orbitolinids agglutinating terrigenous quartz

(?Palorbitolina), as well as large dasycladaleans (Zittelina) are present. Thin section RR4524. e, f Rudstone/floatstone

with coral, bivalve, sponge and echinoderm fragments, large dasycladaleans (Triploporella) and foraminifera. The

large bioclasts are encrusted by foraminifera and red algae (Polystrata and Sporolithon); e, thin section RR4525; f,

thin section RR4527. Scale bar = 1 mm.


98

almost the whole Late Barremian to earliest Aptian

interval. This species is extremely abundant in the Late

Barremian, where it represents the index species for the

M. arabica subzone.

DASYCLADALEAN ALGAE

The dasycladalean algae assemblage identified in the

studied samples includes: Andreiella rajkae, Montiella

elitzae, Neomeris sp., Salpingoporella muehlbergii,

Salpingoporella gr. pygmaea, Salpingoporella sp.,

Suppiluliumaella gr. polyreme, ?Suppiluliumaella sp.,

Triploporella sp. and Zittelina hispanica. A brief

description of these species in alphabetical order follows.

We used the following symbols for the measured size

parameters: D = external diameter of the thallus; d =

diameter of the axial cavity; l = length of the primary

laterals; p = width of the primary laterals; l’ = length of

Fig. 4 Foraminifera from the limestone pebbles of Trbušnica. a-l Montseciella arabica (Henson); a-f, l, subaxial

sections; g, k, transverse-oblique sections; h, i, obliques sections; j, tangential-oblique section. a, c, f, g-j, thin section

RR4518; b, e, k, l, thin section RR4521; d, thin section RR4516. Scale bar = 0.25 mm.


99

the secondary laterals; p’ = width of the secondary

laterals; h = distance between two successive verticils; w

= number of primary laterals in a verticil; w’ = number of

secondary laterals per primary one.

Genus Andreiella Bucur, 2014

Andreiella rajkae Bucur, 2014

(Fig. 5 e)

Andreiella rajkae was recently described by Bucur (2014)

from Upper Barremian – lowermost Aptian (lower

Bedoulian) limestones in the Hăghimaş Mountains

(Eastern Carpathians, Romania). It is characterized by a

cylindrical thallus with a narrow main stem and two

orders of laterals. The first order laterals, large and club-

shaped, gradually broaden from the proximal to the distal

part where they slightly narrow towards the exterior. The

secondary laterals are short and vesiculiform to ovoid in

shape. Calcification forms an irregular sleeve around the

distal end of the primary laterals, embedding the

secondary ones.

A single specimen was identified in the studied samples

from Trbušnica (Fig. 5 e), however it is very

representative for the species. Until this study, A. rajkae

has been identified in only three sites: Mount Rujen

(Vardar zone, Macedonia) (Radoičić, 2002), Bicaz

Gorges (Hăghimaş Mountains, Eastern Carpathians,

Romania) (Bucur & Săsăran, 2011; Bucur, 2014), and

Munella Platform (Albania) (Schlagintweit, unpublished;

Bucur, 2014). Thus, Trbušnica represents the fourth

location for this species.

Dimensions (mm): D = 2.60; d = 0.60; p (distal) = 0.30;

p’ = 0.07.

Genus Montiella L. Morellet & J. Morellet, 1922

Montiella elitzae (Bakalova, 1971) Radoičić, 1980

(Fig. 5 d)

Only one specimen, cut in tangential-oblique-longitudinal

section revealing only partly the axial cavity, was

identified. Nevertheless, it displays the typical

arrangement of the fertile and sterile secondary laterals.

Dimensions (mm): D = 1.0; d = 0.11; Diameter of the

fertile ampoules = 0.26.

Genus Neomeris Lamouroux, 1916

Neomeris sp.

(Fig. 5 g, h)

We have identified two specimens in sub-transversal

section, both showing secondary laterals and ovoidal

fertile ampoules similar to those of Neomeris cretacea

Steinmann. However, while oblique or longitudinal

sections are missing, a species assignment cannot be

without doubt.

Dimensions (mm): D = 1.30-1.50; d = 0.65; l’ = 0.20-

0.32; length of fertile ampoules = 0.15-0.20; width of

fertile ampoules = 0.07.

Genus Salpingoporella Pia in Trauth 1918, emend.

Carras et al., 2006

Salpingoporella muehlbergii (Lorenz, 1902) Pia in

Trauth, 1918

(Fig. 6 a, b)

Only a few specimens were identified in thin section

RR4518 that display the typical shape and size features

for the species Salpingoporella muehlbergii. This is one

of the most frequent dasycladaleans found in Barremian –

Aptian deposits in the Tethys area.

Dimensions (mm): D = 0.37-0.50; d = 0.15-0.20; p

(distal) = 0.08-0.10; h = 0.10.

Salpingoporella gr. pygmaea (Gümbel, 1891) emend

Carras et al., 2006

(Fig. 6 d)

Also in the case of this species, only a few specimens

were identified – mainly cut in oblique sections.

Dimensions (mm): D = 0.78; d = 0.35; l = 0.25-0.30.

Salpingoporella sp.

(Fig. 6 c, e)

We have identified a few larger specimens in a poorer

preservation state than that of S. muehlbergii, showing

about eight phloiophorous laterals per verticil and a thick

calcareous wall; however, a distinct species assignment is

difficult.

Dimensions (mm): D = 0.62-0.77; d = 0.15-0.32; l = 0.22;

p (distal) = 0.10-0.15.

Genus Suppiluliumaella Elliott, 1968

Suppiluliumaella gr. polyreme Elliott, 1968

(Fig. 6 f, h)

The specimens identified in the Trbušnica samples are

present in transversal-slightly oblique sections. The

primary laterals are originally tubular but then they

broaden distally, giving rise to 4-6 secondary laterals

directly connected to the distal part of the primary

laterals, without constrictions (like the fingers of a glove).

Dimensions (mm): D = 1.20-2.10; d = 0.80-0.95; l =

0.30-0.65; p’ (distal) = 0.15-0.20; l’ = 0.15-0.20.

Remarks. Bakalova (1971) has described two new species

of Suppiluliumaella: S. praebalcanica and S. elliotti. The

difference between the first and S. polyreme is

represented by the presence of third order laterals, a

feature that still needs to be documented. S. elliotti differs

from S. polyreme …”par l’absence de parois autour de la

cellule axiale” [while it shows no wall around the axial

cell] (Bakalova, 1971: 125). Table A (in Bakalova, 1971)

summarizing the size differences recorded for the three

species (S. polyreme, S. praebalcanica and S. elliotti)

shows little discrimination, being mainly a proof for

some dimensional overlaps. Some of the apparent

differences may be the result of different sectioning

angles: most of the specimens described by Bakalova

(1971) are present in oblique and transverse sections, in

which the inclination of the primary laterals, their length,

the length of the secondary laterals etc. are more difficult

to evaluate. One cannot exclude that the two species

identified by Bakalova (1971) are recent synonyms for

the species S. polyreme. More samples, including

topotype material, need to be studied in order to confirm

this assumption.


0.35-0.65; l’ = 0.15-0.20; p (distal) = 0.15-0.20; p’ =

0.05-0.07; w = 18-20.

?Suppiluliumaella (Fig. 6 g, j, k)


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Fig. 5 Dasycladalean algae from the limestone pebbles of Trbušnica. a-c, f Zittelina hispanica Masse, Arias & Vilas.

Transverse-slightly oblique (a, b) and oblique (c) sections; f, enlargement of the lower part of the specimen in b. a, c,

thin section RR4524; b, thin section RR4523. d Montiella elitzae (Bakalova) in longitudinal-subaxial section; thin

section RR4521. e Andreiella rajkae Bucur in oblique section; thin section RR4516. g, h Neomeris sp. in transverse

sections; thin section RR4518. Scale bar = 0.25 mm.


101

Fig. 6 Dasycladalean algae from the limestone pebbles of Trbušnica. a, b Salpingoporella muehlbergii (Lorenz);

longitudinal-oblique (a) and transverse-oblique (b) sections; thin section RR4518. c, e Salpingoporella sp. in transverse

section (c) and oblique section (e); thin section RR4518. d Salpingoporella gr. pygmaea (Gümbel) in oblique section; thin

section RR4518. f, h Suppiluliumaella gr. polyreme Elliott; transverse-slightly oblique sections; e, thin section RR4516; h,

thin section RR4517. i ?Triploporella sp.; longitudinal-oblique section, thin sectionRR4518. g, j, k ?Suppiluliumaella sp.

in oblique sections (g, j) and longitudinal-oblique (k) sections; g, thin section RR4519; j, k, thin section RR4521. Scale

bar = 0.25 mm.


102

Present as fragments of relatively large thallus with

ovoidal to ovoidal-elongated-cylindrical primary laterals

that are approximately perpendicular to the axial cavity to

which they are connected through a short peduncle, and

with Suppiluliumaella-type secondary laterals.

Dimensions (mm): D = 1.80-2.50; d = 0.60-0.80; p

(maximum) = 0.30; l = 0.55; p’ = 0.08-0.10; l’ = 0.20; h =

0.10-0.12.

Remarks. Similar specimens were identified in Upper

Barremian – basal Aptian limestones from Bicaz Gorge

(Eastern Carpathians, Romania) (Bucur & Săsăran, 2011:

60-61, Plates 10-11). In spite of the similitude of the

laterals' morphology between this form and genus

Dissocladella, the authors (Bucur & Săsăran, 2011) have

considered that they represent sections through the lower

part of the Suppiluliumaella elliotti thallus (see also

Barattolo, 1983, with a reconstruction of

Suppiluliumaella showing different morphologies and

different inclination of laterals along the axis).

Unfortunately, no section illustrating the continuity

between the two parts of the same algae was identified:

thus, this assignment is still questionable.

Genus Triploporella Steinmann, 1880

?Triploporella sp.

(Fig. 6 i)

We have identified a longitudinal-oblique section through

a specimen that shows well-preserved primary laterals.

They are slightly inclined in respect to the axial cavity.

The distal, probably broadened part of these laterals, as

well as the secondary laterals, are not clearly visible.

Dimensions (mm): D = 1.94; d = 0.64; l = 0.60; p (distal)

= 0.22; h = 0.20.

Triploporella sp.

(Fig. 7 a-g)

In three of the studied sections obtained from sample

RR013234 we have identified the rests of a large

Triploporella species present in transversal-oblique

sections (Fig. 7 a-d); one fragment is present in a

longitudinal-oblique section (Fig. 7 b).

The two transversal sections differ in the size of the axial

cavity and in the display of the laterals. The specimen in

Fig. 7 a shows a broad axial cavity, while that in Fig. 7 d

shows a narrower one. Also, the laterals seem to be less

inclined in the first specimen (Fig. 7 a) and more inclined

in the second one (Fig. 7 d). These features point to the

fact that the alga may display a claviform thallus with a

narrower external diameter and axial cavity in the lower

part (Fig. 7 d) broadening towards the upper part (Fig. 7

a). Secondary laterals are not visible (possibly they are

primarily not-calcified). Typical for the specimens from

Trbušnica are the very small cyst-containers (Fig. 7 b, c,

e-g) as compared to those in other Triploporella species

(e.g. Bucur et al., 2013). At a first glance, they seem to be

simple cysts; when investigated in detail, some show

inner round, micritic corpuscles, and can be considered

intracellular receptacles-type reproducing organs – cyst-

containers that are typical for the genus Triploporella and

are present in most species of this genus (Barattolo, 1980,

1981; Barattolo et al., 2013). Such small cyst-containers

were recently noticed also in other Triploporella

specimens identified in Upper Aptian limestones from the

Apuseni Mountains (Romania) (Bucur et al., 2013).


1.40-1.50; p = 0.25-0.30; w = 45-70; diameter of cyst-

containers = 0.050-0.090/0.040-0.070; cyst diameter =

0.020-0.030.

Genus Zittelina L. Morellet & J. Morellet, 1913

Zittelina hispanica Masse, Arias & Vilas, 1993

(Fig. 5 a-c, f)

Three specimens of a large dasycladalean alga were

identified in transverse-slightly oblique (Fig. 5 a, b) and

oblique (Fig. 5 f) sections. The thallus is calcified only

around the central stem and at the distal end of the

laterals. The area between the two calcified zones is filled

with calcified and partly cement-bound cyst-containers,

around the original area of the primary laterals (Fig. 5 f).

Two Zittelina species are known in Lower Cretaceous

deposits: Z. hispanica and Z. massei (Bucur et al., 2010).

Based on their overall appearance, mainly on the width of

the axial cavity and the d/D ratio, we consider that the

Trbušnica specimens correspond to species Zittelina

hispanica.


1.10-1.30; cyst-container diameter: 0.10-0.12/0.18; cyst

diameter: 0.06-0.08.

Remarks. The dimensions of our specimens are slightly

larger than those indicated by Masse et al. (1993) for the

type-specimens. However, a specimen that one of the

authors (I.I.B.) has collected from the type-locality and

that was illustrated in Bucur (2002) shows an external

diameter of 6.8 mm – thus, the Trbušnica specimens fall

in the dimensional range of Z. hispanica.

ACKNOWLEDGEMENTS

Rajka Radoičić thanks her colleague Ivan Filipović who

kindly showed the outcrop of Lower Miocene

conglomerates overlying Cretaceous succession in

Trbušnica area. We thank the two reviewers, Felix

Schlagintweit and Bruno Granier for their critical

remarks, and Stephen Kershaw for English corrections

and further suggestions on the text.

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Fig. 7 Dasycladalean algae from the limestone pebbles of Trbušnica. a-g Triploporella sp. Transverse (a) and transverse-

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lower cretaceous calcareous algae and foraminifera from trbušnica