Devonian conodont and ammonoid succession of the eastern Tafilalt (Ouidane Chebbi section), Anti-Atlas, Morocco

Devonian conodont and ammonoid succession of the eastern Tafilalt (Ouidane Chebbi section),

Anti-Atlas, Morocco

ZDZIS¸AW BE¸KA1, CHRISTIAN KLUG1, BERND KAUFMANN1, DIETER KORN1, SASCHA DÖRING1, RAIMUND FEIST2 & JOBST WENDT1

1 Geologisch-Paläontologisches Institut der Universität, Sigwartstraße 10, D-72076 Tübingen, Germany

2 Institut des Sciences de l’Evolution, Laboratoire de Paléontologie, Université de Montpellier II, Place E. Bataillon, F-34095 Montpellier, France

ABSTRACT:

BE¸KA, Z. & al. 1999. Devonian conodont and ammonoid succession of the eastern Tafilalt (OuidaneChebbi section), Anti-Atlas, Morocco. Acta Geol. Polon., 49 (1), 1-23. Warszawa.

Devonian conodonts and ammonoids occurring in association in the Ouidane Chebbi section of theeastern Tafilalt (Anti-Atlas, Morocco) are described and analysed in terms of stratigraphy. The excel-lently exposed sequence spans the entire Devonian; it includes open-marine carbonates and shalesdeposited outside the tropical realm. Except for its Middle Devonian part, the Ouidane Chebbi sectionis not condensed. Although the sequence was only sampled in a preliminary fashion, most of it litho-logical units have been dated with some precision. The study is an attempt to enhance the precision inthe correlation between the Devonian conodont and ammonoid sequences. Graphic correlation methodwas used for estimating the precise position of the zonal and stage boundaries for the Middle and UpperDevonian intervals. The stratigraphy of the Lower Devonian at Ouidane Chebbi is still poorly defined.The Eifelian/Givetian boundary is well constrained, especially by both conodonts and ammonoids. Itoccurs within the uppermost part of the Kaãak Event-Level, a characteristic shale horizon that beginsin the ensensis Zone and ranges into the hemiansatus Zone. Biostratigraphic indications from con-odonts show that the top of the Pharciceras limestone unit is located within the norrisi Zone and theGivetian/Frasnian boundary should be placed within the characteristic black styliolinites level of theFrasne Event. The onset of the Kellwasser facies falls within the Zone 12 (winchelli Zone) of theFrasnian and it extends into the rhomboidea Zone. The combined evidence from ammonoid and trilo-bite data suggests that the marine deposition persisted at Ouidane Chebbi at least up to the time of theUpper praesulcata Zone.

Acta Geologica Polonica, Vol. 49 (1999), No. 1, pp. 1-23

INTRODUCTION

Excellent exposures, a great number of well-pre-served fossils and apparently continuous sedimenta-tion in the Anti-Atlas of southern Morocco make itone of the most important areas for study of the

Devonian stratigraphy and palaeontology in theworld. Unfortunately, the commercial collecting offossils – economically significant for the populationliving in this marginal part of the Sahara desert – hasresulted in devastation of many Devonian sectionsand exposures. Evaluating the biostratigraphy of the

2

Devonian sequence in this region requires base-linedocumentation of its faunas. As a contribution tothis we describe the conodont and ammonoid faunafrom the Ouidane Chebbi section (Text-fig. 1), along and complete section representing all ofDevonian time. Except for its Middle Devonian part,this section is not condensed. It is unique alsobecause of the continuous exposure of strata inclu-ding thick portions of soft rocks (shales and marls),which are generally not well exposed at other placesin the eastern Anti-Atlas. Additionally, some singlebedding planes are exposed over hundreds of squaremetres. The only disadvantage is the occurrence of afew dolerite sills within the sequence.

Although the value of conodonts and goniatitesin the Devonian biostratigraphy is well established,correlation of conodont and ammonoid zonalschemes remains rather inaccurate (see BECKER &HOUSE 1994) and needs to be improved. The mainobjective of this study, therefore, was to attempt

integration of conodont and ammonoid biostrati-graphic data derived from the same non-condensedsection. An additional goal has been to documentand analyse the conodont fauna throughout a sedi-mentary sequence deposited outside of the tropicsduring Devonian times. This survey is importantbecause the Devonian conodont biostratigraphyhas come to be based primarily on conodont suc-cessions from areas lying within the equatorial beltat that time. In general, successions of Devonianconodont faunas from regions with temperate cli-mate were not taken into account (e.g. ZIEGLER &SANDBERG 1990).

The Ouidane Chebbi section is situated in theeastern part of the Tafilalt, about 45 km southeastof Erfoud (Text-fig. 1), close to the geomorpholog-ical edge of the Hamada, where the Palaeozoicrocks are concealed under flat-lying Cretaceous-Tertiary cover (Pl. 1, Fig. 1). The Devoniansequence at Ouidane Chebbi (Text-fig. 3) was

ZDZIS¸AW BE¸KA & al.

Rissani

Erfoud

Rabat

Casablanca

250 km

Mediterranean Sea35¡

10¡

5¡

30¡

HIGH ATLAS

MIDDLE ATLAS

ANTI-ATLAS

ATLANTIC O

CEAN

15 km

- Devonian

- Cretaceous andTertiary

Ouidane Chebbi

Fig. 1. Simplified geological map of the northeastern Anti-Atlas showing distribution of Devonian rocks and location of the Ouidane

Chebbi section (asterisked); boxed area indicates field of Text-fig. 2; inset shows regional geology and location of the study area

studied by us along three measured sections loca-ted NW and N of the “Tower Rock”, a conspicuousoutlier left by erosion in front of the Hamada(Text-fig. 2; and Pl. 1, Fig. 1). The conodont,ammonoid, other megafossil, and lithological sam-ples on which this report is based were collectedbetween 1991 and 1998.

GEOLOGICAL BACKGROUND

The palaeogeographic position of the Anti-Atlas during the Devonian is still not satisfactorilyconstrained and thus remains a matter of debate.SCOTESE & MCKERROW (1990), for instance,placed the margin of North Africa at about 40°south of the equator during the Early Devonian,whereas TAIT & al. (1997), based on palaeomag-netic data, postulated a position at a much highersouthern latitude of about 60° during this time.Taking no account of difference in the palaeolati-tude position for Africa in those reconstructions,there is general agreement that the North Africanmargin of Gondwana drifted northwards during theDevonian, but it did not reach the equatorial realmuntil Early Carboniferous times.

The Anti-Atlas area of southern Morocco laywithin the passive continental margin ofGondwana during the Devonian. This passivemargin had already formed during the Ordovicianafter the rifted Peri-Gondwana plates, such asArmorica and Avalonia, moved away fromGondwana. Its depositional and tectonic evolutionwere controlled by regional, E-W trending strike-slip faults. They were reactivated several timesduring Palaeozoic, influenced the subsidence pat-tern, and led to formation of sea-floor relief withcarbonate platforms and small intracratonicmarine basins during the Early Devonian (BELKA

& al. 1997b). In the easternmost part of the Anti-Atlas, WENDT (1988) discriminated an asymmetricbasinal realm, the Tafilalt Basin, bordered on thenorth and west by the pelagic Tafilalt Platform.The Devonian sequence of Ouidane Chebbi wasdeposited in the marginal zone of the TafilaltPlatform. The Lower and Middle Devonian under-went similar lithologic development to centralparts of the platform (KAUFMANN 1998). Duringthe Late Devonian, however, the eastern part ofthe Tafilalt Platform evolved into a south-trendingcarbonate ramp, sloping gently into the TafilaltBasin. The sequence studied of Ouidane Chebbirepresents a deep ramp setting at that time.

PREVIOUS STRATIGRAPHIC STUDIES

The fact that the Devonian rocks at OuidaneChebbi have remained essentially unstudied for along time was primarily because of distance fromErfoud (Text-fig. 1). Unlike other sections of theTafilalt Platform, this locality is not readily acces-sible by car. WENDT & BELKA (1991) provided thefirst columnar section and the preliminary con-odont stratigraphy of the Upper Devonian ofOuidane Chebbi. Frasnian and Famennian con-odont fauna from this locality was used subse-quently in analysis of conodont distribution withinthe Kellwasser facies of the Anti-Atlas (BELKA &WENDT 1992). More recently, BELKA (1995) pre-sented a detailed conodont sequence through theFrasnian-Famennian boundary interval at OuidaneChebbi.

Conodont faunas and associated records ofammonoids about the Middle/Upper Devonianboundary have been reported (ZIEGLER & KLAPPER

1982, BENSAID & al. 1985) from Achguig in theeastern Tafilalt (Text-fig. 2); this section is about 6km N of Ouidane Chebbi. Much of the stratigraph-ical work in the Anti-Atlas related to Devonianconodonts and ammonoids, however, was done inthe central part of the Tafilalt Platform where theBou Tchrafine and the Hamar Laghdad sectionsreceived most attention (e.g. MASSA 1965;BULTYNCK & HOLLARD 1980; BULTYNCK 1985,1987; BECKER & HOUSE 1994; BELKA & al. 1997a).

LITHOLOGY AND BIOTIC COMPONENTS

The Devonian sequence of Ouidane Chebbi isapproximately 350-360 m thick. Neither the basenor the top of the Devonian, however, cannot be pre-cisely identified (Text-fig. 3); neither conodonts norammonoids were found in the critical intervals. Thesequence is dominated by rather monotonous shale,but it contains many very fossiliferous carbonatehorizons (Text-fig. 3; Pl. 1, Figs 1-2). Details of con-odont and ammonoid records are presented in sepa-rate sections (see also Text-figs 4-5 and 7-9) andtherefore they will not be discussed here.

Lower Devonian

The Lower Devonian, about 240-250 m thick,is composed mainly of shales, in which there areseveral characteristic limestone intervals and con-

DEVONIAN SUCCESSION OF MOROCCO 3

cretions (Text-fig. 3). The first limestone key beds,about 2 m thick, contain abundant loboliths andisolated sclerites of Scyphocrinites elegans associ-ated by bivalves, orthoconic cephalopods and raregastropods. These beds, usually referred to as theScyphocrinites limestone, are followed by analmost 60 m thick unit of dark grey shales whichgradually become darker towards the top of theunit. Layers of limestone nodules and, in the mid-dle and upper part, calcareous siltstones are inter-calated. Fossils are restricted to the calcareous layers and are dominated by orthoconiccephalopods, bivalves and rare ostracods anddacryoconarids. Scarcity of benthic organisms andblack colouration of sediments (presumably due tohigh organic carbon content) suggest a presence ofanoxic conditions on the sea floor during middle tolate Lochkovian times. The contact with the over-lying Pragian rocks is marked by a conspicuouscolour change of the shales from dark to light grey

(Text-fig. 3), which was also documented byALBERTI (1981) in the Bou Tchrafine and JebelAmelane sections of the central Tafilalt.

The Pragian interval is about 35 m thick andbegins with a 15 m thick unit of light grey shalesintercalated with thin-bedded nodular limestones.It is followed by 14 m grey, fossiliferous, nodularlimestones which form the first, small ledge in thesection (Pl. 1, Fig. 2). These carbonates show tex-tures from wackestone to packstone and containtrilobites (dominant), crinoids, orthoconiccephalopods, gastropods, bivalves, tabulate andsolitary rugose corals, and occasionally bra-chiopods. The rich benthic fauna and trace fossils(Fucoides) indicate well-oxygenated bottomwaters.

The Emsian part of the section is about 130 mthick and composed predominantly of monoto-nous, greenish shales containing very rare bra-chiopods, orthoconic cephalopods, trilobites,

ZDZIS¸AW BE¸KA & al.4

Oued Chebbi

Hamada du GuirHamada du Guir

Ouidane Chebbi

Achguig

31° 15'

3° 45'

OC I

Middle Devonian Cretaceous

faults

dolerites

Lower Devonian

Upper Devonian

N0 1 2

km

OC III

OC II

Fig. 2. Simplified geological map of the Achguig-Ouidane Chebbi area, to show the distribution of Devonian rocks and location of sam-

pled sections (OC I, OC II and OC III)

ACTA GEOLOGICA POLONICA, VOL. 49 Z. BE¸KA & al., PL. 1

1 – General eastward view of the Ouidane Chebbi area showing the continuous exposure of the Upper Devonian rocks dipping to the right,

discordantly overlain by the Upper Cretaceous carbonates; the most prominent dolerite sills are asterisked; approximately 150 m of Devonian

section is visible and the arrow indicates the upper part of the Givetian condensed carbonates bearing the rich ammonoid Pharciceras fauna

2 – Westward view of the Lower Devonian crest (section OC I); see a person (arrowed) for scale

1

2


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Fig. 3. Lithological column of the Devonian section at Ouidane Chebbi with sample distribution and general stratigraphy

crinoids, dacryoconarids and small solitary rugosecorals. This sequence includes three carbonateunits being very rich both in benthic and nektonicfossils (Text-fig. 3). The lower one consists ofnodular, bioclastic wackestone. Its faunal contentand diversity, are similar to those of the Pragiancarbonates below (Text-fig. 4; Pl. 1, Fig. 2). Thebioclastic limestones are followed by light greyshales bearing, in their upper part, the oldest

ammonoid fauna found in the section, associatedby gastropods and brachiopods. The shales aretopped by a 0.6 m thick biostrome (“Favosites”-biostrome I, Text-figs 3 and 5) with a lateral extentof about 15 m. Apart from a highly diverse tabulatecoral fauna, trilobites, solitary rugose corals,crinoids, brachiopods, orthoconic cephalopods,bivalves and gastropods are common. The coralboundstone is overlain by a 6 m thick, nodular and


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Fig. 4. Lower Emsian part of Ouidane Chebbi section (OC I) with goniatite and conodont distribution; conodont zonation

in parentheses after YOLKIN & al. (1994)

thin-bedded carbonates represented by fossilifer-ous wackestones. This unit, known as theErbenoceras beds, is very distinct morphological-ly, forming the first major crest of the OuidaneChebbi section (Pl. 1, Fig. 2). The fauna containscephalopods (various ammonoids and large ortho-conic cephalopods), trilobites, dacryoconarids, anda few solitary rugose corals. One of its prominentfeatures is a sharp contact between the

Erbenoceras beds and the overlying shales. Theabrupt lithological change can be observed in theEmsian sections over the entire eastern Anti-Atlas;it possibly correlates with the Daleje event, basedtypically on sequences in Bohemia (CHLUPAC &KUKAL 1986). This event corresponds to an appar-ently global transgression (the younger of the twointra-Ib transgressions of JOHNSON & al. 1985,1996) that occurred in the lower part of the inver-


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Dark grey shale

“ Favosites”-biostrome II

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Fig. 5. Emsian/Eifelian boundary interval of Ouidane Chebbi section (OC I) with goniatite and conodont distribution

sus Zone. The thick, overlying shales are poorlyfossiliferous. They become almost black in theirupper part and then pass gradually into the marl-limestone sequence. This third Emsian carbonateunit, called informally as the Sellanarcestes beds,is only 3 m thick. It includes several limestoneinterbeds, among which is another coral biostrome(“Favosites”-biostrome II; Text-figs 3 and 5). Itsfauna of tabulate corals is here much less diversewhen compared with the older biostrome, and con-sists almost exclusively of Favosites (F. bohemi-cus MAURER; see POTTHAST & OEKENTORP 1987).

Middle Devonian

As usual in the eastern Anti-Atlas, the highestDevonian crest of the Ouidane Chebbi section ismade up of carbonates of the Middle Devonian age(Text-fig. 6). The sequence is only 27 m thick, con-densed and very uniform in lithology. The Eifelianpart of the section, about 12 m thick, is characte-rized by nodular, fossiliferous wackestones withintercalations by medium-bedded limestone. Therich fauna includes goniatites, orthoconiccephalopods, dacryoconarids, trilobites, bra-chiopods and bivalves. At the top, there is a 0.7 m

thick shale intercalation forming a conspicuouscavetto; it contains a diverse haematitizedammonoid fauna (Text-fig. 7). It represents TheKaãak Event, a deepening event recognized world-wide and having an unquestionably eustatic charac-ter (cf. HOUSE 1985, JOHNSON & SANDBERG 1988).

There is no significant lithological differencebetween the Eifelian and Givetian interval.However, the Givetian carbonates, about 15 mthick, has higher carbonate content and thickerbedding. The character of the fauna is very similarto that of the Eifelian carbonates. In the upper part,a very thin (about 5 cm), distinctive marker bed ispresent. It contains many small lenticular bra-chiopods (Ambocoelia aff. mesodevonica). Thislayer has also been identified in the adjacent sec-tion at Achguig by LOTTMANN (1990) and correla-ted with the upper part of the Upper pumilio hori-zon (Text-fig. 8). In the Middle Devonian atOuidane Chebbi, as in the section at Achguig, otherbeds bearing the brachiopod pumilio fauna are notpresent.

Upper Devonian

The Upper Devonian sequence is at least 110 mthick and differentiated with respect to facies(Text-fig. 3). It begins with a 3.6 m black carbon-ate unit that is conspicuous due to its high organiccarbon content (Text-fig. 8). The rocks are styli-olinid/tentaculitid packstones and wackestoneswith thin shale intercalations. In addition to abun-dant styliolinids and tentaculites, entomozoanostracods and small orthoconic cephalopods arepresent. We also found rare specimens of Buchiola(bivalve). This unit represents the so-called FrasneEvent (sensu HOUSE 1985), the first episode duringthe Late Devonian characterized by oxygen-deple-ted water on the sea floor. It is widespread through-out the Tafilalt and is a useful key horizon forregional and intercontinental correlation (WENDT

& BELKA 1991). Contact between these black car-bonates and the overlying nodular limestones issharp and marked by a distinct change in colour.The nodular limestones, about 5 m thick, are thick-bedded, light-coloured wackestones and mud-stones. They are burrowed in places and containrelatively common cephalopods. This unit is gen-erally well exposed in the whole Tafilalt region andis lithologically rather uniform.

In all localities, where the Frasnian nodularlimestones appear, they are overlain by a very


Fig. 6. View of the main crest of the Ouidane Chebbi section

built up of the Middle Devonian condensed carbonates; eastern

wall of Hamada with flat-lying Upper Cretaceous carbonates

visible as an outlier in the background

prominent sequence of black shales and/or lime-stones representing the Kellwasser facies in south-ern Morocco. At Ouidane Chebbi, this unit attainsa thickness of about 50 m, ranges high into theFamennian, and consist of black shales with thininterbeds of black marly mudstones (Text-fig. 3).In contrast to the Kellwasser sediments of theVariscan Europe, these sediments are extremelyfossiliferous containing predominantly nektonicand planktic fauna represented by goniatites, ortho-conic nautiloids, conodonts, and styliolinids (formore details see WENDT & BELKA 1991). The con-tact between the black Kellwasser sediments andthe overlying well-oxygenated carbonates is sharp

but generally masked by rock waste of a doleritesill. Together with igneous rocks, these limestonesform the third major crest of the Ouidane Chebbisection (Pl. 1, Fig. 1).

The characteristically yellow-coloured lime-stones are about 8 m thick and characterized by anodular fabric and textures from wackestone topackstone. They contain a relatively rich cephalo-pod fauna (ammonoids and orthoconic nautiloids),in places associated with scattered brachiopods.The unit consistently occurs above the Kellwassersediments in the entire Tafilalt region (WENDT &BELKA 1991). It is lithologically variable, contain-ing predominantly coarse crinoidal packstones in


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sesi

Sob

olew

ia n

ucifo

rmis

Ago

niat

ites

obliq

uus ST

AG

ES

27

[m]

26

25

28

29

30

31

32

33* 26

25* 25

24

23* 2322

* 20

* 19

18

17

Gon

iatit

es

Con

odon

ts

Sub

anar

cest

es m

acro

ceph

alus

Wer

nero

cera

s cf

. tes

tatu

m

SA

MP

LES

OC

II

Limestone

Nodular limestone

Shale

21

Wer

nero

cera

s cf

. rup

pach

ense

Agoniatitesobliquus

Subanarcestesmacrocephalus

Fig. 7. Eifelian/Givetian boundary interval of Ouidane Chebbi section (OC II) with goniatite and conodont distribution; boundaries

of conodont zones are calculated by graphic correlation with the Anti-Atlas regional composite (AARC; see BELKA & al. 1997a);

conodont zonation after BELKA & al. (1997a)

the central, more shallow-water areas of theTafilalt Platform, and fine-grained cephalopodwackestones to mudstones in marginal situations.In the Ouidane Chebbi section, this carbonate unitis followed by more than 50 m of light-colouredshales (Text-fig. 3).

In general way, the lower part of the overlyingunit is composed of greenish shale with severallimestone intercalations in which the carbonatelayers are commonly disrupted into lenses and nod-ules. The common fossils include ammonoids, gas-tropods, brachiopods and placoderm skulls. Thetop of this interval is marked by a thin (about 0.5m) black shale horizon that probably represents theLate Devonian Hangenberg Event (Text-fig. 3).The middle part of the interval is about 15 m thick,it consists of the most terrigenous-rich rocks of the

entire Devonian section at Ouidane Chebbi. Tracefossils and sole marks are abundant in the siltstoneand sandstone interbeds, whereas fossils are scarceand poorly preserved. The only exceptions are twoprominent but thin sideritic intercalations. The firstone, approximately 16 m above the HangenbergEvent horizon, has an ammonoid fauna withAcutimitoceras intermedium. The second interca-lation, 2 metres higher, contains common trilo-bites: Belgibole abruptrirhachis and Macroboleaff. funirepa. Both taxa co-occur in manyEuropean sections; for instance, in the Carnic Alps(Grüne Schneid), Rhenish Slate Mountains(Drewer, Stockum), Franconia (Gattendorf) andMontagne Noire (Puech de la Suque). Their occur-rence at Ouidane Chebbi is the first known outsideEurope.


Table 1. Numerical distribution of conodont species in the Ouidane Chebbi I section (OC I)

rhenanus

Zone 5 (punctata)

CO

NO

DO

NT

ZO

NA

TIO

N

Zone 4(transitans)

FR

AS

NIA

NG

IVE

TIA

NS

TA

GE

S

Zone 1(pristina)

norrisi

ansatus

latifossatus

C O N O D O N T S

Mes

otax

is fa

lsio

valis

Pol

ygna

thus

dub

ius

Pol

ygna

thus

den

gler

iP

olyg

nath

us o

rdin

atus

Sch

mid

togn

athu

s pe

racu

tus

Pol

ygna

thus

pen

natu

sP

olyg

nath

us p

ollo

cki

Anc

yrod

ella

rot

undi

loba

Anc

yrod

ella

rug

osa

Pal

mat

olep

is tr

ansi

tans

Pol

ygna

thus

ling

uifo

rmis

ling

uifo

rmis

Pol

ygna

thus

var

cus

Pol

ygna

thus

rhe

nanu

sP

olyg

nath

us li

ngui

form

is w

eddi

gei

Pol

ygna

thus

ling

uifo

rmis

muc

rona

tus

Kla

pper

ina

oval

isP

alm

atol

epis

pun

ctat

a

Pol

ygna

thus

aff.

P. p

lana

rius

Pol

ygna

thus

sp.

F K

LAP

PE

R &

LA

NE

Icrio

dus

sym

met

ricus

Pal

mat

olep

is tr

ansi

tans

→ p

unct

ata

Anc

yrod

ella

gig

as (

form

2)

Pol

ygna

thus

den

gler

i (n

arro

w fo

rm)

Anc

yrod

ella

gig

as (

form

1)

Pharcicerastridens

Beloceras tenuistriatum

GO

NIA

TIT

E S

UC

CE

SS

ION

Maenioceras terebratum

Zone 2(rotundiloba)

Zone 3(rugosa)

Zone 6(primus)

Mesobeloceras kayseri

Man

ticoc

eras

cor

datu

mS

andb

erge

roce

ras

cost

atum

Man

ticoc

eras

art

umC

arin

ocer

as s

p.

G O N I A T I T E S

Pha

rcic

eras

kay

seri

Eob

eloc

eras

taou

zens

eP

harc

icer

as tr

iden

s

Tor

noce

ras

sim

plex

(ty

pum

?)

Syn

phar

cice

ras

clav

ilobu

mS

ynph

arci

cera

s c

f. pl

urilo

batu

m

Pse

udop

robe

loce

ras

nebe

chen

se ?

Ste

noph

arci

cera

s ks

eire

nse

Ste

noph

arci

cera

s lu

nulic

osta

Mer

opha

rcic

eras

dis

cifo

rme

Pon

ticer

as k

ayse

riP

ontic

eras

sp.

Pet

tero

cera

s er

rans

40

[m]

39

38

41

42

43

44

45

46

47

48

30

34

38*

**

*

39

32

*

*

Gon

iatit

es

Limestone

Nodular limestone

Black, bituminous,laminated limestone

Marl

Upper pumilio-bed

FR

AS

NE

EV

EN

T

OC III/9

OC III/10

29

3031

35

37

33

39

40

Con

odon

ts

Sel

lago

niat

ites

disc

oide

s

Wed

ekin

della

psi

ttaci

na

Ago

niat

ites

sp.

Wed

ekin

della

bril

onen

sis

lata

Mae

nioc

eras

tere

brat

umM

aeni

ocer

as c

rass

um

Pha

rcic

eras

bec

heriSA

MP

LES

OC

II

Pha

rcic

eras

cf.

aren

icum

Man

ticoc

eras

sp.

Mes

obel

ocer

as k

ayse

riM

esob

eloc

eras

sp.

Bel

ocer

as te

nuis

tria

tum

disparilis

hermanni

Petteroceras errans

Sellagoniatitesdiscoides

Givetian/Frasnian boundary interval of Ouidane Chebbi section (OC II) with goniatite and conodont distribution; Givetian conodont zonation after BELKA & al. (1997a) and KLAPPER & JOHNSON (1990); Frasnian conodont zonation after

KLAPPER & al. (1996); boundaries of conodont zones are calculated by graphic correlation with the Frasnian composite standard (KLAPPER 1997)

ACTA GEOLOGICA POLONICA, VOL. 49 Z. BE¸KA & al., FIG. 8

CONODONT FAUNA

Conodonts were recovered mainly from carbon-ate lithologies. The collection has been assembledfrom samples collected during several periods offieldwork. For this study a total of 90 samples, eachbetween 1-2 kg, was processed. From these, only 71samples yielded identifiable conodont elements. Itshould be noted that all but one barren sampleswere from the Lower Devonian. In that part of thesection, the recovery rate of conodonts was alsorather low (generally below 50 elements/kg). Themost abundant faunas were isolated from sedimentsof the Kellwasser facies. Occurrences of conodonts(listed in Tables 1-3) depict the abundance andranges of Pa elements in the Ouidane Chebbi sec-tion. Although we have not noted sedimentarystructures suggesting significant redeposition in thesection, the platform (Pa) elements remarkably out-number other elements (Pb, S and M) in the studiedsamples. Synsedimentary, posthumous transport ofconodont elements seems most likely to be respon-sible for the unbalanced composition of the fauna.There is evidence, such as oriented fossils, indica-ting the presence of current activity, even in settingswith an anaerobic depositional regime in the easternAnti-Atlas during the Devonian (WENDT & BELKA

1991, WENDT 1995).The low number of the Early Devonian con-

odonts obtained during this study does not allowreliable statistical comparison with coeval faunasknown from other continents (e.g. CARLS &GANDEL 1969, KLAPPER 1969, KLAPPER & MURPHY

1975, AL-RAWI 1977, SCHÖNLAUB 1985, MAWSON

1987, VALENZUELA-RIOS 1990). It appears, howev-er, that the fauna in the Anti-Atlas is both lessabundant and less diverse, but it do not contain anyendemic forms (see also BULTYNCK 1985).Possible ecological cause(s) of the paucity and lowdiversity of the fauna might have been the positionof the Anti-Atlas at very high palaeolatitudes dur-ing Early Devonian time or local facies control.

Conodonts recovered from the condensedEifelian and Givetian carbonates include taxawhich were cosmopolitan during the MiddleDevonian. It shows a similar level of diversity tothat recognized in the localities of the marginalzone of the Mader Basin (BULTYNCK 1985, BELKA

& al. 1997a). Both the conodont abundance anddiversity at Ouidane Chebbi are lower than in theadjacent Bou Tchrafine section, although theMiddle Devonian in both sections displays a simi-lar lithological development and a comparable

level of sediment condensation. We interpret thisphenomenon as an effect of sampling because theBou Tchrafine section was sampled several times(see BELKA & al. 1997a) and thus a large volumeof rock was processed previously.

The conodont fauna of the Kellwasser facies isabundant but slightly less diverse than time-equiv-alent faunas in the Upper Devonian of theEuropean Variscides. This feature can be observedthroughout the whole area of the Anti-Atlas, bothin basinal sequences and on carbonate platforms(BELKA & WENDT 1992). Typical is the lack of se-veral late Frasnian species of Palmatolepis (e.g. P.linguiformis, P. rhenana) that are widespread incentral Europe and North America. In terms ofdiversity, the Frasnian conodont fauna in the Anti-Atlas is similar to that of the Montagne Noire inFrance (see for comparison KLAPPER 1988), but itis dominated by polygnathids. In addition, theFrasnian portion of the Kellwasser sequence atOuidane Chebbi yields lower numbers of taxa thanequivalent sediments in the inner parts of theTafilalt Platform. This pattern has been discussedby BELKA & WENDT (1992), who showed that asimple ecological model of conodont distributioninvolving distance from shore and water depth, asproposed by SANDBERG & al. (1988), is not valid inthe Upper Devonian of the Anti-Atlas.

AMMONOID FAUNA

Compared to most of the Devonian successionsof the eastern Anti-Atlas the Ouidane Chebbi sec-tion is very rich in ammonoids. More than 1100specimens of over 100 species of ammonoids werecollected. They were extracted from various litholo-gies and consequently are preserved in variousways: as calcareous, haematitic or sideritic internalmoulds, sometimes with imprints of the externalsculpture, and also as calcareous steinkerns withshell remains. All collected specimens are three-dimensionally preserved. Deformation as a conse-quence of tectonic stress or compaction is rare.Haematitic specimens are abundant in the Emsianshales, in the Kaãak Event-Level (upper Eifelian),and in the black shales of the Kellwasser facies.Ammonoids preserved in sideritic nodules, howev-er, occur only in the topmost part of the Famennian.

The Ouidane Chebbi section is rich in earlyEmsian (Zlichovian) ammonoids exhibiting thehighest diversity observed in the Anti-Atlas. Thefauna is predominantly composed of cosmopolitan



Table 2. Numerical distribution of conodont species in the Ouidane Chebbi II section (OC II)


Table 3. Numerical distribution of conodont species in the Ouidane Chebbi III section (OC III)

genera but it is generally less diverse than faunasknown from regions located at lower latitudes duringEmsian times such as Bohemia, North Ural, Guangxi(China), Bretagne, and Germany. A distinct biogeo-graphic pattern, however, cannot be recognized at thegeneric level. The late Emsian (Dalejan) faunas aredominated by anarcestid ammonoids, i.e. the generaLatanarcestes, Praewerneroceras, Sellanarcestes,and Anarcestes, which are known to occur in theRhenohercynian belt of Germany, and also inBohemia.

The Eifelian ammonoids from Ouidane Chebbiare among the most diverse faunas of this time-slice worldwide (see Tables 4-6). Similar faunasare known especially from the Wissenbach Shale(Germany) and from the Chotec Limestone of theBarrandian (Czech Republic). During the Eifelianmost of the ammonoid genera and possibly alsosome species were cosmopolitan. The speciesSubanarcestes macrocephalus, for instance,which is present in the faunas of the Anti-Atlas, isknown from the Rhenohercynian belt of Germany,the Brittany, the Cantabrian Mountains, and theNorth Urals, but was not yet reported from theBarrandian.

The early Givetian ammonoid fauna of OuidaneChebbi is relatively poor (Table 5). It shows theclosest relationship to ammonoids occurring in theRhenohercynian belt of Germany and England.The late Givetian ammonoid fauna, however, con-tains highly diverse populations and belongs to therichest faunas known from this time-span. Most of

the genera are widely distributed throughoutVariscan Europe. Faunas of other areas in theworld (the Altay in Kazakhstan, eastern UnitedStates, and Guangxi) are considerably poorer ingenera and species.

Despite the extremely large numbers ofammonoid specimens which can be collected in theFrasnian of the Tafilalt, only rather few genera andspecies are known. The fauna consists mainly ofManticoceras and the closely related genera(Carinoceras, Crickites), Mesobeloceras, as wellas Beloceras. Compared with other regions (east-ern United States, the Rhenohercynian belt, theTiman, the North Urals, and the Canning Basin),this fauna displays much lower diversity. It is con-spicuous, however, that the largest known Frasnianammonoids, attaining more than 60 cm in diame-ter, were observed in several localities of the east-ern Anti-Atlas.

Ammonoids are also extremely frequent in theFamennian part of the Kellwasser facies, but unlikethe Frasnian, the fauna is highly diverse (BECKER

1993) and comparable to those of other regions,e.g. the Rhenohercynian belt, the Montagne Noire,and the South Urals. Many of the genera appear tobe cosmopolitan, but there are also endemic taxa,such as Acrimeroceras, which is very common inone distinct horizon across the Tafilalt.Interestingly, the Prolobites fauna is under-repre-sented. Horizons rich in advanced tornoceratids aswell as diverse faunas containing Prolobites andthe earliest clymeniids, which are well known fromthe Rhenohercynian belt, the Holy CrossMountains, and the South Urals, have not beenfound in North Africa at all. Clymeniid faunas ofthe Tafilalt are comparatively rich, but are lessdiverse than faunas known from Germany, Poland,Russia (South Urals) and Kazakhstan. Severaltaxa, however, such as Platyclymenia annulata,Platyclymenia subnautilina, Prionoceras divisum,and Prionoceras frechi, have a cosmopolitan dis-tribution and are common.

STRATIGRAPHY

Conodont biostratigraphy already offers a high-resolution framework for the Devonian but the cur-rently used zonal schemes still have potential forbeing made more precise (see Text-fig. 10).Moreover, there is no conodont zonal scheme forthe Devonian which has obtained universal accep-tance. Progress in recent years has been due not


Table 4. Numerical distribution of ammonoid fauna in the

Ouidane Chebbi I section (OC I); specimens collected from

scree are asterisked

only to the abundance of new stratigraphic data butalso because of introduction of new concepts instratigraphical practice, including multielementtaxonomy, shape analysis, and graphic correlation(e.g. MURPHY & BERRY 1983, KLAPPER & FOSTER

1993, KLAPPER & al. 1996, BELKA & al. 1997a).The fact that we do not yet have a “standard” conodont scheme for the Devonian is just a reflec-tion of the current dynamics in development

towards a high-resolution Devonian chronostrati-graphic scale based on conodonts.

Because of the long stratigraphic range of theOuidane Chebbi section, we were constrained touse various conodont zonal schemes in our study.For the Lochkovian and Pragian we applied thezonation established by KLAPPER (1977), KLAPPER

& ZIEGLER (1979), and LANE & ORMISTONE (1979).The Emsian zonation follows a scheme proposed


Table 5. Numerical distribution of ammonoid fauna in the Ouidane Chebbi II section (OC II); specimens collected from scree

are asterisked

by YOLKIN & IZOKH (1988) and its refined version(YOLKIN & al. 1994). For the Middle Devonian andFrasnian intervals, we used the chronostratigraphicframeworks (the Anti-Atlas regional compositeand the Frasnian Composite Standard) and the co-nodont zonations recently constructed by graphiccorrelation (BELKA & al. 1997a, KLAPPER 1997).Both frameworks provide much higher stratigra-phic resolution than traditionally used conodontzonations. The Frasnian Composite Standard, inci-dentally, is based on several dozen sections world-wide located in different climatic settings during

Late Devonian times (KLAPPER 1997); it offers animproved basis for intercontinental correlation.

There are a number of other advantages to bios-tratigraphy when it is based on graphic correlationand composite standards (see CARNEY & PIERCE

1995). Among the most important of these aresimultaneous visual comparison of all fossil rangesavailable for the correlation and the ease withwhich the composite standard (CS) is enhancedeach time. The zonal markers, in contrast with con-ventional biostratigraphy, do not have the status ofbench marks to which the ranges of other species


Table 6. Numerical distribution of ammonoid fauna in the Ouidane Chebbi III section (OC III); specimens collected from scree

are asterisked

are compared. Thus, the impact of all species on aCS are similar and the result is certainly moreobjective. By biostratigraphic evaluation of newsections the position of zonal boundaries can beestimated with great precision. Based on data pro-vided by KLAPPER (1997), we made use of thismethod, even for the lowest Famennian, althoughwe used in fact the classical zonation proposed byZIEGLER & SANDBERG (1990) for that stage.

Ammonoid stratigraphy differs conceptuallyfrom conventional conodont biostratigraphy,because ammonoid appearances provide a morestroboscopic rather than continuous picture of thefossil record. This is probably why the ammonoidzones, as defined by BECKER & HOUSE (1994) forthe Lower and Middle Devonian, for instance, arein fact faunal intervals having in most cases thecharacter of assemblage zones. Another problem inpractice is that ammonoid faunas very ofteninclude specimens collected from scree; these donot allow the recognition of the precise stratigra-phic range in the section. During our study, there-fore, ammonoid records have been carefully docu-mented (Tables 4-6) in order to achieve precisecorrelation with the conodont stratigraphy. In thisway we are endeavouring to establish a detailedammonoid stratigraphic sequence for the Devonianof the Anti-Atlas, which then can be applied inde-pendently where conodonts are absent.

Although ammonoids are generally very fre-quent in the Devonian of the eastern Anti-Atlas,the species on which the Devonian ammonoidzonation of Becker (in WEDDIGE 1997) is based areeither relatively rare or absent. From the 59 indexspecies of this scheme proposed for global use only16 were found at Ouidane Chebbi. The globalammonoid zonation, which has been amalgamatedfrom various local and regional ammonoid zona-tions around the world, is thus not readily applica-ble in southern Morocco. We discriminated there-fore horizons based on the most characteristicammonoid species occurring abundantly in theAnti-Atlas (Text-figs 7-8).

Lower Devonian

As already mentioned above, theSilurian/Devonian boundary cannot be preciselyrecognized at Ouidane Chebbi section, but itprobably lies within the upper third of a 120 mthick shale unit that underlies the LochkovianScyphocrinites limestone. Conodonts isolated

from these carbonates are indicative of theeurekaensis conodont Zone. Although the co-nodont record in the Lower Devonian is poor andwe were not able to recognize any of the Pragianconodont zone, correlation with other sections inthe region is facilitated by the conspicuous colourchange (see Text-fig. 3) which probably corre-lates with the end-pesavis event (sensu TALENT &al. 1993) at the end of the Lochkovian. This eventis manifested by a reduction in diversity of theconodont faunas. In eastern Australia, it is relatedto a regional regression, the global extent ofwhich is still uncertain (TALENT & al. 1993).

The Pragian/Emsian boundary could not bedetermined but it must occur within the interval oflight grey shales below the first Emsian carbonateunit (Text-fig. 3; Pl. 1, Fig. 2), which contains co-nodonts assignable to the dehiscens and gronbergiconodont zones. The ammonoid fauna is extraordi-narily rich in this interval. Striking is the occur-rence of the species Gyroceratites laevis, whichmakes its first appearance with the Mimagoniatitesfauna. In the ammonoid zonation of BECKER (inWEDDIGE 1997), this taxon defines a zone(Gyroceratites laevis Zone) succeeding theMimagoniatites fecundus Zone. Obviously theappearance of Gyroceratites laevis around theworld was diachronous. It is thus not suitable forprecise stratigraphic correlations.

The third last Emsian carbonate band bearingthe Sellanarcestes ammonoid fauna lies evidentlywithin the serotinus Zone. Due to scattered sam-pling the position of the Emsian/Eifelian boundaryin the section cannot be precisely indicated. Takinginto account the similar lithological developmentof the Bou Tchrafine section and its stratigraphy(BULTYNCK 1985), we place this boundary tenta-tively about 3-4 m below the base of the thick-bed-ded Eifelian limestones of the costatus conodontZone (Text-fig. 5). Unfortunately, we have notfound any ammonoids in this interval.

Middle Devonian

The Eifelian is very much condensed but ourconodont data are insufficient to state whether thesequence is continuous or not. The ammonoidfauna documents only the upper part of the stage.The genus Sobolewia (Table 5) is stratigraphicallyimportant in the rich Eifelian Subanarcestes fauna;this is the oldest records of the genus globally (cf.BECKER & HOUSE 1994). The Eifelian/Givetian


boundary is well constrained by both conodontsand ammonoids. Graphic correlation with the Anti-Atlas regional composite reveals its position with-in the uppermost part of the Kaãak Event-Level(Text-fig. 7). This characteristic shale horizon

begins in the ensensis conodont Zone and rangesinto the hemiansatus conodont Zone of theGivetian. The first specimens of Agoniatites havebeen found in the limestone bed directly underly-ing the Kaãak Event-Level. Thus, the entry of this


34

[m]

33

32

35

36

37

38

39

40

41

42

15

16

1718

192021

22

24

25

2643

CO

NO

DO

NT

ZO

NA

TIO

N

FR

AS

NIA

NF

AM

EN

NIA

N

C O N O D O N T S

Pal

mat

olep

is a

ff. P

. bog

arte

nsis

Pal

mat

olep

is w

inch

elli

Pal

mat

olep

is h

assi

Pol

ygna

thus

web

bi

Pal

mat

olep

is b

ogar

tens

is

Anc

yrod

ella

cur

vata

(la

te fo

rm)

Anc

yrog

nath

us a

sym

met

ricus

Pol

ygna

thus

pol

itus

Icrio

dus

alte

rnat

us a

ltern

atus

Icrio

dus

alte

rnat

us h

elm

siA

ncyr

ogna

thus

ubi

quitu

sP

alm

atol

epis

tria

ngul

aris

Icrio

dus

iow

aens

isP

olyg

nath

us b

revi

lam

inus

Pal

mat

olep

is c

lark

i

Anc

yrog

nath

us s

inel

amin

us

Icrio

dus

corn

utus

Pal

mat

olep

is d

elic

atul

a

Pal

mat

olep

is m

inut

a m

inut

a

Pal

mat

olep

is te

nuip

unct

ata

Pal

mat

olep

is q

uadr

antin

odos

alob

ata

Limestone

Limestone nodules

Black, bituminous shale

CO

NO

DO

NT

SA

MP

LES

OC

III

ST

AG

ES

Zone 13(bogartensis)

Upp

er

tria

ngul

aris

Mid

dle

Low

.

Fig. 9. Frasnian/Famennian boundary interval of Ouidane Chebbi section (OC III) with conodont distribution; Frasnian conodont zonation

after KLAPPER & al. (1996); Famennian conodont zonation after ZIEGLER & SANDBERG (1990); boundaries of conodont zones

are calculated by graphic correlation with the Frasnian composite standard (KLAPPER 1997)

genus can be correlated with the basal part of theensensis Zone.

Conodonts and ammonoids provide evidencethat, like the Eifelian, the Givetian sequence atOuidane Chebbi is much condensed.Biostratigraphically diagnostic conodonts wererecovered from the basal and uppermost parts of theGivetian only. Thus, we were able to identifyunequivocally the hemiansatus, timorensis,rhenanus, and norrisi conodont zones (Text-figs 7-8). The fragment of the section, in which the ansa-tus to disparilis conodont zones are to be expected,is about 4 m thick; i.e. it constitutes only ca. 25% ofthe studied Givetian sequence. In contrast, the timo-rensis and rhenanus conodont zones together (for-merly the Lower varcus Zone) comprise at least60% of the measured thickness. HOUSE (1995) cal-culated the duration (in real time) of the Givetianconodont zones and showed similar time-propor-tions for these intervals, namely 30% and 58%,respectively. Therefore, we do not expect any sig-nificant stratigraphic gaps in the poorly constrained(by conodonts) ansatus to disparilis interval. Usefulevidence here is the record of Sellagoniatites dis-coides which first appears immediately below theUpper pumilio level and ranges upwards to occurwithin the terebratum ammonoid fauna. The entryof S. discoides at Ouidane Chebbi is the oldestrecord of this species in southern Morocco (cf.BECKER & HOUSE 1994). The uppermost part of theGivetian has produced both rich ammonoid and co-nodont faunas. The detailed ammonoid sequence,however, is not completely straightforward becauseof great number of loose specimens collected fromthe Pharciceras limestone (Text-fig. 8 and Tab. 5).Conodont information obtained from the OC II andOC III sections shows evidently that the top of thelight-coloured, pharciceratid-bearing carbonates islocated within the norrisi conodont Zone. Usinggraphic correlation between the Ouidane Chebbiconodont succession and the Frasnian CS (KLAPPER

1997), the Givetian/Frasnian boundary should beplaced about 20 cm above the base of the blackstyliolinites of the Frasne Event.

Upper Devonian

Currently, only conodonts offer useful evidencefor dating sedimentary events in the Frasnian por-tion of the studied sequence. Biostratigraphic con-trol is first of all confined to intervals close to thelimits of lithological units; it provides no indication

of stratigraphic gaps associated with those boun-daries. The first black carbonate unit of the FrasneEvent, the base of which almost coincides with thelower Frasnian stage boundary (Text-fig. 8),ranges into the Zone 4 (transitans). Detailed bios-tratigraphy of the overlying light-colouredcephalopod-bearing carbonates, in terms of co-nodont zones, remains unknown but the conodontfauna collected at its top (Table 3, sample OC-III-11) is diagnostic of the Zone 12 (winchelli). Thefirst limestone band within the black shales of theKellwasser facies (Text-fig. 3) has the same age.The Frasnian/Famennian boundary cannot be iden-tified on the basis of lithology. It must occur with-in the 1.5 m thick shale interval between the sam-ple OC-III-21 and OC-III-22 (Text-fig. 9) contain-ing, respectively, the last Frasnian and the firstFamennian conodont fauna. Graphic correlation ofconodont data against the Frasnian CS place thisboundary in the lower part of the interval, about 25cm above the last Frasnian carbonate horizon. Thefirst carbonate band with Famennian conodontscan be easy identified as it contains numerousspecimens of the ammonoid Phoenixites frechi (Pl.5, Figs 3-4). As already demonstrated by WENDT &BELKA (1991), the Kellwasser lithology at OuidaneChebbi extends into the rhomboidea Zone. Ofgreat significance for stratigraphic correlation is,however, the fact that the top of this unit is marked-ly diachronous through its area of distribution inthe eastern Anti-Atlas. Contrary to that, the onsetof the overlying nodular limestones dated as Lowermarginifera conodont Zone marks a synchronoussedimentary event resulted from worldwide trans-gression at that time. Above this level, the bios-tratigraphy of the upper part of the Famennian atOuidane Chebbi is based only on ammonoids andtrilobites. The ammonoid fauna documents wellthe interval from the biferum to the paradoxaammonoid Zone. Stratigraphically important is theoccurrence of the goniatite Acutimitoceras inter-medium (Pl. 5, Figs 7-8) above the last black shalehorizon in the section (Text-fig. 3), indicating theUpper praesulcata conodont Zone. The trilobites(Belgibole abruptrirhachis and Macrobole aff.funirepa) found also in this interval represent theyoungest Devonian trilobite association knownfrom southeastern Morocco. In all European local-ities, where these taxa are present, they occur with-in the Upper praesulcata Zone. Thus, both trilo-bites and ammonoids strengthen the contentionthat the underlying black shales equate with theHangenberg Shale developed in the Rhenish Slate



STAGES CONODONTZONES

SERIES

costatus

rhenanus

Zone 12(winchelli)

triangularis

crepida

rhomboideamarginifera

posteraexpansa

praesulcata

timorensis

patulus

inversus

pesavis

delta

excavatus(gronbergi)

eurekaensis

Pra

gian

Loch

kovi

an

LOW

ER

DE

VO

NIA

N

serotinus

Thickness[m]

200

100

300

Em

sian

woschmidti

AGEEPOCH

Pra

gian

Loch

kov.

EA

RLY

DE

VO

NIA

N

Em

sian

Eife

lian

Giv

etia

n

LAT

E D

EV

ON

IAN

Fra

snia

nF

amen

nian

MID

DLE

DE

VO

NIA

N

AGE[Ma]362.0

376.5

382.5

387.5

394.0

409.5

413.5

417.0

OUIDANE CHEBBI SECTIONDEVONIAN TIMESCALE

UP

PE

R D

EV

ON

IAN

Fam

enni

an

Frasnian

MID

DLE

DE

VO

NIA

N Givetian

Eifelian

Zone 11 (jamieae)

kitabicus (dehiscens)

sulcatus

kindlei

pirenae

nothoperbonus

Fig. 10. Comparison of stage thicknesses in the Ouidane Chebbi section with the numerical Devonian timescale of TUCKER & al. (1998);

note the stratigraphic condensation of the Middle Devonian

Mountains. Furthermore, it bears to continuousmarine sedimentation continuing to the very top ofthe Devonian in the eastern Tafilalt. The wide-spread distribution of trilobites of the abrup-tirhachis-funirepus group makes these fossils as auseful biostratigraphic marker for the uppermostFamennian, immediately below the Devonian/Car-boniferous boundary.

Acknowledgements

The Authors thank M. BENSAID, M. DAHMANI and A.FADILE (all Ministere de l’Energie et des Mines, Morocco)for a work permit and logistic advice. The research wassupported by the Deutsche Forschungsgemeinschaft. Thisis a contribution to the IGCP Project No. 421 “NorthGondwana mid-Palaeozoic bioevent/biogeography patternin relation to crustal dynamics”. Special thanks are to J.TALENT (Sydney) for several suggestions that significantlyimproved the manuscript. Technical assistance during thelaboratory work was provided by W. GERBER and H.HÜTTEMAN (both Tübingen).

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Manuscript submitted: 23rd September 1998Revised version accepted: 17th December 1998

PLATE 2

1-2 – Latericriodus postwoschmidti (MASHKOVA, 1968)1 – Sample OC-I-1, × 502 – Basal cavity partly broken, sample OC-I-1, × 55

3 – Latericriodus sigmoidalis (CARLS & GANDEL, 1969); sample OC-I-22, × 55

4 – Latericriodus beckmanni (ZIEGLER, 1956); sample OC-I-28, × 55

5 – Pandorinellina steinhornensis steinhornensis (ZIEGLER, 1956);sample OC-I-28, × 70

6 – Polygnathus bultyncki WEDDIGE, 1977; sample OC-I-38, × 50

7 – Polygnathus gronbergi KLAPPER & JOHNSON, 1975; lower view, freeblade broken, sample OC-I-21, × 80

8 – Polygnathus costatus patulus KLAPPER, 1971; sample OC-I-39, × 55

9 – Polygnathus hemiansatus BULTYNCK, 1985; sample OC-II-23, × 40

10 – Polygnathus aff. planarius KLAPPER & LANE, 1985; sample OC-II-40, × 40

11 – Polygnathus cf. linguiformis transversus WITTEKINDT, 1965; sampleOC-II-25, × 40

12 – Polygnathus linguiformis weddigei CLAUSEN, LEUTERITZ & ZIEGLER;1979, sample OC-II-29, × 50

Unless otherwise stated, all figures are upper views


1


1

5 6 7 8

1211109

2 34

PLATE 3

1-2 – Palmatolepis punctata (HINDE, 1879)1 – Sample OC-II-39, × 502 – Sample OC-II-41, × 40

3 – Palmatolepis aff. proversa KLAPPER, 1988; sample OC-II-41, × 70

4 – Palmatolepis bohemica KLAPPER & FOSTER, 1993; sample OC-II-41, × 40

5 – Palmatolepis mucronata KLAPPER, KUZMIN & OVNATANOVA,1996; oblique upper view, sample OC-II-41, × 40

6 – Ancyrognathus “sp. A” of WANG & ZIEGLER, 1983; sample OC-II-41, × 80

7 – Polygnathus aff. pennatus HINDE, 1879; sample OC-II-41, × 65

8 – Polygnathus decorosus STAUFFER, 1938; sample OC-II-41, × 65

9-10 – Polygnathus sp. F of KLAPPER & LANE, 19859 – Sample OC-II-41, × 65

10 – Oblique lateral view, sample OC-II-40, × 65

Unless otherwise stated, all figures are upper views


1


1 2 3

654

7 8 9 10

PLATE 4

1-2 – Latanarcestes noeggerathi (VON BUCH, 1832); lateral and ventralview, loosely collected specimen from shales below theSellanarcestes beds, GPIT 1849-145, × 1.1

3-4 – Sellanarcestes wenkenbachi WALLISER, 1965; lateral and ventralview, bed OC-I-35, GPIT 1849-758, × 1

5-6 – Agoniatites obliquus (WHIDBORNE, 1889); lateral and ventralview, bed OC-II-27, GPIT 1849-314, × 1.1

7-8 – Maenioceras terebratum (SANDBERGER & SANDBERGER, 1851);lateral and ventral view, bed OC-II-32, GPIT 1849-323, × 1

9-10 – Petteroceras errans (PETTER, 1959); lateral and ventral view,loosely collected specimen from the Upper Givetian Pharciceraslimestone, GPIT 1849-780, × 1.1

11-12 – Ponticeras kayseri (WEDEKIND, 1918); lateral and ventral view,loosely collected specimen from the Upper Givetian Pharciceraslimestone, GPIT 1849-388, × 1.1


1


1

5

9 10 11 12

6 7 8

2 3 4

PLATE 5

1-2 – Triainoceras costatum (D’ARCHIAC & DE VERNEUIL, 1842); lateraland ventral view, loosely collected specimen from the lowerFrasnian nodular limestones below the Kellwasser unit, GPIT1849-390, × 1

3-4 – Phoenixites frechi (WEDEKIND, 1918); lateral and ventral view,OC-III-23, GPIT 1849-530, × 1

5-6 – Acrimeroceras falcisulcatum BECKER, 1993; lateral and ventralview, loosely collected specimen from the middle Famennian nodu-lar limestones overlying the Kellwasser unit, GPIT 1849-520, × 1.1

7-8 – Acutimitoceras intermedium SCHINDEWOLF, 1923; lateral and ven-tral view, OC-III-49, GPIT 1849-751, × 1.3

9-11 – Macrobole ex gr. funirepa FEIST, 19889 – Incomplete pygidium, partially external mould; trilobite

horizon above sample OC-III-49, UM2-RF 123, × 7.510 – Incomplete pygidium, partially external mould; trilobite

horizon above sample OC-III-49, UM2-RF 124, × 4.511 – Incomplete pygidium, partially external mould; trilobite

horizon above sample OC-III-49, UM2-RF 122, × 8

12 – Pseudowaribole conifer gibber ALBERTI, 1975; fragmentary crani-dium, external mould, sample OC-III-48, UM2-RF 127, × 6.5

13 – Belgibole abruptirhachis RICHTER & RICHTER, 1951; incompletepygidium, latex cast of external mould, trilobite horizon above sam-ple OC-III-49, UM2-RF 121, × 6

14 – Phacops (Omegops) “sp. T ” of STRUVE, 1976; incompletecephalon, plasticine cast of external mould, marlstone above sam-ple OC-III-48, UM2-RF 125, × 1.5

15 – Pseudowaribole conifer gibber ALBERTI, 1975; pygidium withdamaged axis, external mould, sample OC-III-48, UM2-RF 128, × 5.5


1


1

5

9

13 14 15

10 11 12

67 8

2 3 4

Documents

Devonian conodont and ammonoid succession of the eastern Tafilalt (Ouidane Chebbi section), Anti-Atlas, Morocco