Late Cenomanian–Early Turonian ammonites of the southern Tethys margin from Morocco to Oman: Biostratigraphy, paleobiogeography and morphology

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Cretaceous Research xxx (2013) 1e21

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Cretaceous Research

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Late CenomanianeEarly Turonian ammonites of the southern Tethys margin fromMorocco to Oman: Biostratigraphy, paleobiogeography and morphology

Christian Meister*, André PiuzNatural History Museum of Geneva, Geology and Paleontology Department, CP 6434, 1211 Geneva 6, Switzerland

a r t i c l e i n f o

Article history:Received 28 November 2012Accepted in revised form 29 March 2013Available online xxx

Keywords:AmmonitesLate CretaceousSouthern Tethys marginBiostratigraphyPaleobiogeographyMorphology

* Corresponding author.E-mail addresses: [email protected] (C

ge.ch (A. Piuz).

0195-6671/$ e see front matter � 2013 Elsevier Ltd.http://dx.doi.org/10.1016/j.cretres.2013.03.009

Please cite this article in press as:Meister, C.,to Oman: Biostratigraphy, paleobiogeograph

a b s t r a c t

The CenomanianeTuronian ammonite biostratigraphical framework for the southern Tethys margin(North Africa, Middle East and the Arabian Peninsula) is becoming better understood. A first attempt at asynthetic range chart is presented, with 85 taxa and precise correlations for ammonites along a westeeast transect from Morocco to Oman, inclusive of the Trans-Saharan Seaway as far south as northernNigeria. On the basis of a critical review of ammonite taxonomy, 13 bioevents can be identified in theinterval from the Late Cenomanian to the Early Turonian (c. 3.5 myr) with each bioevent correspondingto a time interval of approximately 270,000 years, on average. They are consistent throughout severalregions along the southern Tethys margin, though some gaps remain, at least at the stage boundary.These bioevents are correlated with the zonation defined for the stratotype (GSSP) of the base of theTuronian in the Western Interior (USA). The paleobiogeographic distribution of ammonites reveals someendemism but the predominant picture is that of a homogeneous fauna throughout the area, eventhough distinct Boreal and Western Tethys (Atlantic domain) marine influences are evident. An inter-pretation of the evolution of conch morphology and ornamentation through the zones of the LateCenomanianeEarly Turonian is proposed.

� 2013 Elsevier Ltd. All rights reserved.

1. Introduction

The present study analyses the spatial and temporal distributionof ammonites of the Upper Cenomanian and Lower Turonian alongthe southernmargin of the Tethys fromMorocco to Oman, inclusiveof the Trans-Saharan Seaway as far south as northern Nigeria(Fig. 1). It is based on a critical compilation of our own data andthose taken from the literature. The latter sources include Basse andChoubert (1959), Charrière et al. (1998), Meister and Rhalmi (2002),Kennedy et al. (2008), Lehmann and Herbig (2009) and Cavin et al.(2010) for Morocco (Pre-African Trough, High and Middle Atlas);Amédro et al. (1996), Busson et al. (1999), Chikhi-Aouimeur et al.(2011) and Benyoucef et al. (2012) for Algeria (Pre-African Trough,Atlas, Sahara); Robaszynski et al. (1990, 1993), Chancellor et al.(1994), Meister and Abdallah (1996, 2005, 2012) for central andsouthern Tunisia; Meister et al. (1992, 1994) for Niger (Damergou,Tenere); Reyment (1954), Barber (1957), Meister (1989), Courvilleet al. (1991), Zaborski (1993, 1995, 1996) and Courville (1993) fornorthern Nigeria; Rossi Ronchetti and Albanesi (1961) for Libya(Tripolitania); Allam (1986), Luger and Gröschke (1989), Kassab

. Meister), andre.piuz@ville-

All rights reserved.

Piuz, A., Late CenomanianeEay and morphology, Cretaceo

(1991, 1996), Wiese and Schulze (2005), Nagm et al. (2010a, b)and Nagm and Wilmsen (2012) for Egypt (Libyan Desert, EasternDesert); Freund and Raab (1969), Lewy and Raab (1978), Lewy et al.(1984), Aly and Abdel-Gawad (2001) and Kassab and Obaidalla(2001) for Egypt and Israel (Sinai and Negev); Basse (1940, 1954),Dubertret (1950), Dubertret and Wetzel (1956), Saint Marc (1974)and Wiese and Schulze (2005) for Lebanon; Mouty et al. (2003)for Syria (Palmyrides Chain); Aly et al. (2008) for Jordan; Powerset al. (1966), El-Khayal (1986) for Saudi Arabia; Kennedy andSimmons (1991) and Meister and Piuz (in prep.) for Oman (Adamfoothills). These data are of variable reliability. The currently knowndistribution of the fauna and the high diversity in some areas couldsimply be a historical artefact due to the longer and more intensiveinvestigation of areas such as northern Nigeria, Tunisia or Egypt, incomparison to regions such as Libya, Syria, Lebanon and theArabian Peninsula, where knowledge is at a preliminary stage.

2. Biostratigraphical framework

For the first time, a tentative synthetic range chart is proposedfor Late CenomanianeEarly Turonian ammonites of the southernTethys margin from Morocco to Oman (Figs. 2 and 3). This rangechart is based on data published for this region. It should be bornein mind that the taxonomy and the stratigraphic records rely

rly Turonian ammonites of the southern Tethysmargin fromMoroccous Research (2013), http://dx.doi.org/10.1016/j.cretres.2013.03.009

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http://dx.doi.org/10.1016/j.cretres.2013.03.009



Fig. 1. Geographic location of the main regions studied.

C. Meister, A. Piuz / Cretaceous Research xxx (2013) 1e212

heavily on the precision in collecting faunas bed-by-bed and on thetaxonomic concepts of the authors. However, while these condi-tions clearly vary from one author to another, and from one regionto another, much recent progress has been made in CenomanianeTuronian ammonite biostratigraphy. In constructing this chart wehave encountered several problems such as virtually coexistingspecies (presence of a taxon A below a taxon B in some areas andthe reverse elsewhere) and different local zonal schemes, whichmake interpretations difficult. The paucity of precise data availableon total ranges, associations and correlations of ammonites is alsoproblematic. Moreover, ammonite range within a zone is oftenunclear, making accurate discussion and formal definition of thezonal boundaries complicated.

To avoid a proliferation of regional zonations we propose asuccession of 13 biostratigraphic units (bioevents) characterizedby faunal markers and we try to correlate these bioevents directlywith the zonation in the Western Interior, where the Globalboundary Stratotype Section and Point (GSSP) for the base of theTuronian Stage is defined (Colorado, USA) and, in part, with thatfrom Tunisia (Chancellor et al., 1994) (Fig. 4). However, most taxafrom the stratotype are either poorly represented or absentalong the southern Tethys margin, making some correlationsconjectural.

Upper CenomanianCalycoceras guerangeri ZoneThis zone is characterized by the presence of three main markers:Neolobites vibrayeanus (d’Orbigny), Calycoceras naviculare (Mantell)and Eucalycoceras pentagonum (Jukes-Browne). The Neolobitesvibrayeanus Zone is a possible Tethyan zonal equivalent (for furthersynonymy see Nagm et al., 2010b, p. 23).

Please cite this article in press as: Meister, C., Piuz, A., Late CenomanianeEato Oman: Biostratigraphy, paleobiogeography and morphology, Cretaceo

Bioevents A1eA2. Two bioevents characterize this zone, withbioevent A1 at its very base and typified by the presence ofNeolobites fourtaui Pervinquière, Neolobites vibrayeanus, Cun-ningtoniceras tinrhertense Collignon and Calycoceras, and bio-event A2 by the association of Calycoceras naviculare, Calycocerasgr. haugi Pervinquière/guerangeri (Spath), Eucalycoceras penta-gonum and Neolobites vibrayeanus, including N. vibrayeanusbrancai Eck.

Bioevent A1 is correlated with the lower part of Calycocerascanitaurinum Subzone (lowermost part of Calycoceras guerangeriZone) and bioevent A2 in part with the Calycoceras canitaurinumSubzone and, less precisely, with the Metoicoceras mosbyenseSubzone (lower-middle and upper parts of the Calycoceras guer-angeri Zone, respectively).

Eucalycoceras rowei (Spath), Forbesiceras sp. and Metengonocerasdumbli (Cragin) have also been recorded from this zone. Thetopmost part of the zone is difficult to delineate, even thoughMetengonoceras acutum Hyatt and the first Pseudocalycoceras arepresent.In Algeria Neolobites occurs below Calycoceras naviculare; inTunisia, Egypt and Lebanon Calycoceras sp. is also present abovethe N. vibrayeanus beds and only in Oman do we observe thepresence of Calycoceras below it (Figs. 5 and 6). Locally, wehave observed a succession among the Neolobites with Neo-lobites fourtaui followed by Neolobites vibrayeanus in Egypt,possibly in Oman, and Neolobites vibrayeanus followed byN. vibrayeanus brancai in Tunisia. Neolobites vibrayeanus (d’Or-bigny) is often associated with nautilids such as Eutrephocerasand Angulithes (see Basse and Choubert, 1959; Meister andRhalmi, 2002).


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Fig. 2. Synthetic range chart proposed for Late CenomanianeEarly Turonian ammonites of the southern Tethys margin from Morocco to Oman, with the potentially reproducible bioevents and correlation with the zonation (part 1).Kennedy and Cobban, 1991; Kennedy et al., 2000, Chancellor et al., 1994.

C.Meister,A

.Piuz/Cretaceous

Researchxxx

(2013)1e21

3

Pleasecite

thisarticle

inpress

as:Meister,C.,Piuz,A

.,LateCenom

anianeEarly

Turonianam

monites

ofthesouthern

Tethysmargin

fromMorocco

toOman:

Biostratigraphy,paleobiogeographyand

morphology,Cretaceous

Research(2013),http://dx.doi.org/10.1016/j.cretres.2013.03.009

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Fig. 3. Synthetic range chart proposed for Late CenomanianeEarly Turonian ammonites of the southern Tethys margin from Morocco to Oman, with the potentially reproducible bioevents and correlation with the zonation (part 2).Kennedy and Cobban, 1991; Kennedy et al., 2000; Chancellor et al., 1994.

C.Meister,A

.Piuz/Cretaceous

Researchxxx

(2013)1e21

4Pleasecite

thisarticle

inpress


.,LateCenom

anianeEarly

Turonianam

monites

ofthesouthern

Tethysmargin

fromMorocco

toOman:




NAI

NO

RU

TR

EP

PU

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R C

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KENNEDY and COBBAN 1991 Potential faunal markers for the southern Tethys margin

Neolobites vibrayeanus

Calycoceras haugi-guerangeri

Euomphaloceras septemseriatum

Nigericeras gadeni

Pseudaspidoceras pseudonodosoides

Vascoceras gamai

Vascoceras cauvini

Vascoceras proprium

Pseudotissotia nigeriensis

Pseudaspidoceras flexuosumor Vascoceras durandi

Wrightoceras wallsiWrigthoceras munieri

Kamerunoceras turoniense

Fig. 4. Bioevents and potential faunal markers amongst Late CenomanianeEarlyTuronian ammonites of the southern Tethys margin. Kennedy and Cobban, 1991;Kennedy et al., 2000; Chancellor et al., 1994.

C. Meister, A. Piuz / Cretaceous Research xxx (2013) 1e21 5

Correlation. For the period considered, bioevent A1 is the mosthomogeneous and the most representative bioevent throughoutthe province. Relatively short in duration, species of Neolobitesmake very precise markers. Bioevent A1 is recorded throughout theprovince from Morocco to Oman, except for northern Nigeria, aregion which was not affected by the marine transgression in theearly Late Cenomanian. Further west, in Morocco, this bioeventseems to be confined to the Goulmima area (Pre-African Trough). Itis the bioevent which is most easy to correlate for the whole timespan considered. It has been cited from Libya and Saudi Arabia,though only limited data are available. Biovent A2 is found moreepisodically, with different taxa in different regions that do notfacilitate exact correlations. Nevertheless, the association of Caly-coceras and Eucalycoceras pentagonum represents the best markerof this bioevent (Figs. 5 and 6). Bioevent A2 is less widely distrib-uted; it is not evident in Morocco, clearly recognizable in Algeriaand Tunisia and less clearly so elsewhere in the area underinvestigation.

Metoicoceras geslinianum ZoneThe Sciponoceras gracile Zone is an equivalent biochronologic unit(for further synonymy see Nagm et al., 2010b, p. 24).Metoicoceras geslininaum (d’Orbigny), Euomphaloceras septemser-iatum (Cragin), Nigericeras gadeni (Chudeau) and Nigericeras jac-queti Schneegans are characteristic of this zone.

Bioevents B1eB2. Metoicoceras geslinianum, index species of thezone, is the primary marker for bioevents B1 and B2, in view of itswide geographical distribution throughout the study area.

Please cite this article in press as:Meister, C., Piuz, A., Late CenomanianeEato Oman: Biostratigraphy, paleobiogeography and morphology, Cretaceo

Metengonoceras dumbli is a longer-ranging species, partiallycovering bioevents B1 and B2.The occurrence of Euomphaloceras septemseriatum, Pseudocaly-coceras gr. angolaense (Douvillé) and Gentoniceras, (?)Eucalycocerastenereensis Meister et al. and M. geslinianum, mainly in the lower-middle parts of the zone, and Nigericeras gadeni, Nigericerasjacqueti, Burroceras sp., (?)Fikaites africaensis Meister et al. andM. geslinianum, mainly in the upper part of the zone, suggests apossible subdivision of this bioevent into two parts. B1 and B2,respectively, can be correlated with the Sciponoceras gracile andBurroceras clydense subzones.

Again, the lack of precision in data published does not allow avery efficient range chart for this fauna, or definition of the totalrange of these forms. Other taxa such as (?)Thomelites numidicusMeister and Abdallah provide only local information.

Correlation. Bioevents B1eB2 are not represented in Syria, Lebanonand, possibly, Jordan. The lower part of the Metoicoceras geslinia-num Zone, corresponding to bioevent B1, is present in Tunisia,possibly in Niger, Nigeria, Egypt and Oman. The upper part of thezone, corresponding to bioevent B2, is well represented in thewestern part of the area, the Maghreb (doubtfully in Morocco) andsouth Saharan regions, but not clearly so towards the east, in Egypt,in the Middle East (maybe in Israel where Vascoceras cauvini Chu-deau is present), doubtfully in Oman and absent in all other regions.

Nigericeras gadeni shows a broadly northesouth trend fromTunisia to northern Nigeria and represent a good marker for thisarea.

Neocardioceras juddii ZoneThe Vascoceras cauvini Zone could be an equivalent biochronologicunit (for further synonymy see Nagm et al., 2010b, p. 25 and re-marks below).

In the area investigated, several taxa are good markers for thiszone with Pseudaspidoceras pseudonodosoides (Choffat), severalVascoceras [V. gamai Choffat, V. crassum (Furon), V. ellipticum Barber,V. barcoicensis exile Cobban et al., V. glabrum (Barber), and possiblyV. cauvini (see below)], Fikaites laffitei Collignon/subtuberculatumCollignon, Nigericeras cf. scotti Cobban and Neocardioceras sp. Thiszone is characterized by two bioevents.

Bioevents C1eC2. These units are correlated to the lower part of theNeocardioceras juddii Zone (N. juddii Subzone). Bioevent C1 istypified by the presence of Pseudaspidoceras pseudonodosoides andbioevent C2 has V. gamai as the main marker. The first is correlatedwith the lower part of the Neocardioceras juddii Subzone and thesecond with the upper part of the same. Also present are rare formssuch as “Euomphaloceras” costatum Cobban et al., Nigericeras jac-queti involutus Meister et al. and Pseudaspidoceras tassaraensisMeister et al.

Correlation. Pseudaspidoceras pseudonodosoides, and the alliedspecies, P. grecoi Collignon and P. tassarensis, are widely representedin the western region from Morocco to Egypt and Nigeria, as isVascoceras cauvini, which is also present in Egypt and, in places, inthe Middle East. Further east, C1 is missing while C2 appears to berestricted to the Saharan regions.

Bioevent D. This bioevent is correlated with the upper part of theNeocardioceras juddii (Nigericeras scotti Subzone). It is character-ized by the presence of numerous species of Vascoceras (e.g.V. cauvini, V. ellipticum, V. crassum) and in Tunisia only byN. cf. scotti,Rubroceras burroense Cobban et al. and V. crassum. The topmost part


Stag

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ZONATION

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Zones Subzones

?

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NIGER NORTH NIGERIA

Horizons

?

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?

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KENNEDY and COBBAN, 1991

KENNEDY et al., 2000

CHANCELLOR et al., 1994 (partim*)

Mammites nodosoides

V. (G.) birchbyi(? = ~ T. rollandi)

Nigericeras scotti



(? = ~ W. coloradoense)


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Metoicoceras mosbyense*

Calycocerascanitaurinum*

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(High, Middle Atlas, Pre-African through)

BASSE and CHOUBERT, 1959CHARRIERE et al., 1998

MEISTER and RHALMI, 2002KENNEDY et ., 2008

Faunal assemblages

MOROCCO

Faunal assemblages

Mammites nodosoidesChoffaticeras segne

Fagesia peroniH. mirabilis - wohltmanni

Wrightoceras munieri

Neoptychites / VascocerasPseudotissotia ?

Pseudasp. flexuosum

Neoptychites ?

(Pre-African through*Sahara, Saharan Atlas °)

Pseudaspidoceras sp.Vascoceras sp.

Vascoceras gr. cauvini

Pseudaspidocerascf. pseudonodosoides


Nigericeras ? sp.

F. peroni/Choffati./P. nigeriensisPseudotis. nigeriensis

V. cauvini

Neolobites vibrayeanus +*° Neolobites vibrayeanus Neolobites vibrayeanus Neolobites vibrayeanus

AMEDRO et al., 1996

BUSSON et al., 1999

CHIKHI-AOUIMEUR et al., 2011

BENYOUCEF et al., 2012LEHMANN and HERBIG, 2009CAVIN et al., 2010

Pseudaspidoceras grecoi

V. gamaiFikaites

Nigericeras gadeni

Eucalyco. pentagonumCalycoceras naviculare

(Central Tunisia)

ROBASZYNSKI et al., 1990, 1993

CHANCELLOR et al., 1994

MEISTER and ABDALLAH,

2012

Horizons - Faunal assemblages

(Gafsa-Chott)

MEISTER and ABDALLAH, 1996, 2005

Faunal assemblages

Mammites nodosoides


K. turoniense

Choffaticeras

Thomasites rollandiF. peroni

Wrightoceras munieri

Pseudaspidoceras pseudonodosoides

Euomphallocerascf. septemseriatum

Eucalycoceras / ThomelitesCalyco. haugi-guerangeri

Horizons - Faunal assemblages

MEISTER et al, 1992, 1994

REYMENT; 1954, BARBER, 1957

MEISTER, 1989

ZABORSKI, 1993, 1995, 1996

COURVILLE et al., 1991

COURVILLE, 1993

Mammites nodosoides

T. roll. meslei / B. yoko.

S. (Jeanrogi.) / C. luciae

P. barberi / T. rollandi

M. nodosoides

?Choffaticeras

P. flexuosum

Vascoceras crassum

P. paganum

BurrocerasNigericeras

? Thomelites numidicusM. geslinianum

T. rollandi / S. (Jeanrogi.)/ V. durandi

V. gamai

P. pseudonodosoides

Metengonoceras dum

bli

? Eucal. tenereensis

? Fikaites africaensis

N. jacqueti/M. geslinianumN. gadeni /

Neol. vibrayeanus brancai

M. dum

bli

P. tassaraensis

V. cauvini

Vascoceras glabrum

Wrightoceras wallsi

V. proprium - tectiforme

Metengonoceras dumbli

Choffati./P. nigeriensisPseudotis. nigeriensis

M. geslinianum

Nigericeras gadeni

P. pseudonodosoides

V. gamai

V. crassum/ V. nigeriensis

Fikaites

Vascoceras glabrum

P. flexuosum /V. costatum

P. barberiP. nigeriensis /

Eotissotia/F. superstes

Kamerunoceras ?Mammites nodosoides/

P. nigeriensis /W. wallsi/F. levis

W. munieri/H. ingens/F. levis

Watinoceras

Thomasites gongilensis

Mammites sp.°

E. costatum/Neocardioc.°

Metengonoceras°

W. coloradoense

W. colo-

radoense

Rubroceras burroenseNigericeras cf. scotti

?Vascoceras durandi

Bio

even

ts

D

E

F

H

A1

A2

B1

B2

C1

C2

G1G2G3

(Damergou, Tenere)

Fig. 5. Ammonite correlations from Morocco to northern Nigeria, with potentially reproducible ammonite bioevents and the zonation (part 1). Kennedy and Cobban, 1991; Chancellor et al., 1994; Kennedy et al., 2000.

C.Meister,A

.Piuz/Cretaceous

Researchxxx

(2013)1e21

6Pleasecite

thisarticle

inpress


.,LateCenom

anianeEarly

Turonianam

monites

ofthesouthern

Tethysmargin

fromMorocco

toOman:




Stag

es

ZONATION

Zones Subzones

?

KENNEDY and COBBAN, 1991

KENNEDY et al., 2000

CHANCELLOR et al., 1994 (partim*)

Mammites nodosoides

V. (G.) birchbyi(? = ~ T. rollandi)

Nigericeras scotti



(? = ~ W. coloradoense)


Burroceras clydense


Metoicoceras mosbyense*

Calycocerascanitaurinum*

M.

nodo

-so

ides

W. c

olor

adoe

nse

N. j

uddi

iM

. ges

linia

num

= S.

gra

cile

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C. g

uera

nger

i*

LO

WE

R T

UR

ON

IAN

UP

PE

R C

EN

OM

AN

IAN

ROSSI RONCHETTI

and ALBANESI, 1961

Faunalassemblage

SAUDIARABIA

LIBYA

?


M. geslinianum

P. pseudonodosoides

V. durandi

P. flexuosum

Mammites nodosoides

P. nigeriensis

EGYPT(Libyan Desert, Eastern Desert)

EGYPT (Sinaï) LEBANON CENTRAL SYRIA JORDANISRAEL (Negev)

Faunal assemblages Faunal assemblages Faunal assemblages Faunal assemblages Faunal assemblages

LUGER and GRÖSCHKE, 1989ALLAM, 1986, KASSAB, 1991

WIESE and SCHULZE, 2005NAGM et al., 2010ab

NAGM and WILMSEN, 2012

FREUND and RAAB, 1969LEWY and RAAB, 1978

LEWY et al., 1984ALY and ABDEL-GAWAB, 2001

KASSAB and OBAIDALLA, 2001

BASSE, 1940, 1954DUBERTRET and WETZEL,

1956, DUBERTRET, 1950SAINT MARC, 1974

WIESE and SCHULZE, 2005

MOUTY et al., 2003 ALY et al., 2008

Kameruni. turonienseW. munieri / H. ingens

C. luciae

Mammites nodosoides Mam. nodosoides

?

Choffaticeras ssp.

Thomasites rollandi

Choffaticeras ssp.

Choffaticeras ssp.

Choffaticeras ssp.

Choffaticeras ssp.

Thomasites rollandi T. rollandi T. rollandi

V. pioti / V. durandi

Euomphaloceras sp.

V. cauvini

Vascoceras proprium Vascoceras proprium

inivuac.Vinivuac.V

Eucalycoceras sp.

Neolobites sp. Neolobites sp. N. vibrayeanus? N. aff. fourteaui

M. dumbli

Neoptychites

ParamammitesPseudaspidoceras

H. ingens

VascocerasP. flexuosum

OMAN

Faunal assemblages

KENNEDY and SIMMONS, 1991

MEISTER and PIUZ, in prep.

V. durandi

N. vibrayeanus/Calycoceras

Calycoceras sp.

M. geslinianum

T. cf. gongilenseParamammites sp.

Pseudaspidoceras sp.

Fagesia sp.

Eotissotia / Wrightoceras

Euomphaloceras (= Kanabiceras)

Neolobites fourteauiNeolobites sp. N. vibrayeanus

POWERS et al., 1966

EL-KHAYAL, 1986

Faunalassemblage

P. cf. pseudonodosoides

Calycoceras sp. Calycoceras sp. Calycoceras sp.

? ?

M. geslinianum -? V. cauvini

Calycoceras sp.

Bio

even

ts

D

E

F

H

A1

A2

B1

B2

C1

C2

G1G2G3

(Tripolitania) (Palmyrides chain) (Adam foothills)

Fig. 6. Ammonite correlations from Libya to Oman, with potentially reproducible ammonite bioevents and the zonation (part 2). Kennedy and Cobban, 1991; Chancellor et al., 1994; Kennedy et al., 2000.

C.Meister,A

.Piuz/Cretaceous

Researchxxx

(2013)1e21

7

Pleasecite

thisarticle

inpress


.,LateCenom

anianeEarly

Turonianam

monites

ofthesouthern

Tethysmargin

fromMorocco

toOman:





of this zone is also characterized by the first V. glabrum andV. tectiforme, as well as by S. (Jeanrogiceras) subconciliatum (Cour-tiller), which probably persists into the Lower Turonian. A subdi-vision of bioevent D may be possible, but more precise data are stillneeded.

Correlation. The uppermost zone of the Cenomanian is well repre-sented throughout the province.The Neocardioceras juddii Subzone, corresponding at its base tobioevent C1, can be correlated precisely fromMorocco to Egypt, andbioevent C2 has a similar reproducibility as far as Jordan. InMorocco, the presence of bioevent D is not clear, and no data areavailable for the Arabian Peninsula. In between, it is well repre-sented from Tunisia to the Middle East, encompassing Niger andnorthern Nigeria.

Remark. Based on Lewy et al. (1984), Vascoceras cauvini Chudeau co-occurs with M. geslinianum, then succeeds alone in the Negev re-gion (Israel). This observation challenges the validity of a Vasco-ceras cauvini Zone. In other areas, V. cauvini is clearly situatedstratigraphically higher. For example in Morocco, Algeria, Niger andEgypt it is correlated with the lower part of the Nigericeras scottiSubzone (upper Neocardioceras juddii Zone) and corresponds tothe Vascoceras cauvini Zone in the literature. In other countries theposition of V. cauvini remains ambiguous because the data for levelsbelow or above the V. cauvini beds are imprecise or lacking.

CenomanianeTuronian boundary

The primary marker for the CenomanianeTuronian boundary isan ammonite and the base of the Turonian coincides with the firstappearance of Watinoceras devonense Wright and Kennedy. Theabsence of Watinoceras devonense in the study area precludesprecise placement of the CenomanianeTuronian boundary asdefined for the GSSP of the Turonian in Pueblo (Colorado, USA)(Kennedy et al., 2000). The presence of the genusWatinoceras, withWatinoceras sp. in Morocco and W. aff. coloradoense in Nigeria, therange of which cover the first two (maybe three) subzones of theTuronian, does not allow delineation of the boundary, so theWatinoceras devonense Subzone cannot be recognized and is hy-pothetical. Placing the CenomanianeTuronian boundary at the firstoccurrence of Vascoceras proprium Reyment only solves the prob-lem in part, in view of the rather restricted distribution of thisspecies (Egypt and Jordan). Moreover, it is uncertain whether thisrepresents a real equivalent to the (first) occurrence of Watinocerasdevonense. In the absence of a better solution, we follow this pro-posal, which can be roughly correlated with the other localitiesalong the southern Tethys margin, and assume correspondencewith the Watinoceras devonense Subzone of the Western Interior.Other fossil markers or isotope stratigraphy could probably providemore precise answers.

The Upper Cenomanian is fairly well characterized by ammon-ites, unlike the lowermost Turonian with its ammonite paucity,making the boundary difficult to place. Nevertheless, some taxa arepresent around the C-T boundary. The so-called bioevents DeEcontain several Vascoceras among which V. tectiforme (Barber) andV. globosum s. l., S. (Jeanrogiceras) subconciliatum and Pseudaspido-ceras paganumefooteanum. These rare species are not widelydistributed and thus add to the difficulty in tracing the lowermostTuronian throughout the study area.

Lower TuronianWatinoceras coloradoense ZoneFollowing Nagm et al. (2010b), the Vascoceras propriumZone corresponds to a period from the lower part of the


zone, W. devonense Subzone, to its middle part, the P.flexuosum Subzone (for further synonymy see Nagm et al.,2010b, p. 26). The Thomasites rollandi Subzone is equivalentto the upper part of the zone [V. (Greenhornoceras) birchbyiSubzone].

Bioevent E. This bioevent is correlated with the lower part of theW. coloradoense Zone (W. devonense Subzone). At the very base ofthe Turonian V. proprium occurs alone, at least in Egypt and Jordan,then the association with other Vascoceras such as V. durandi(Thomas and Peron) indicates the upper part of this biovent, at leastin Egypt. In northern Nigeria V. proprium belongs to a wide group ofVascoceras [V. globosum (Reyment) s.l.] that already appeared in theUpper Cenomanian, making it difficult to place the boundaryprecisely.Pseudaspidoceras paganum Reyment/footeanum (Stoliczka), Vasco-ceras sp. and V. globosum (Nigeria), and probably S. (Jeanrogiceras)subconciliatum (Tunisia) and Watinoceras sp. (Morocco), could alsobe present at the base of this subzone. In the upper part, V. durandiand Pseudaspidoceras flexuosum Powell occur. Neoptychites cepha-lotus (Courtiller), Fagesia sp., Thomasites gongilense (Woods), whosetotal ranges are not well known, could also be present in biovent E(e.g. northern Nigeria).

Bioevent F. The presence of P. flexuosum and V. durandi (withoutV. proprium) characterizes this bioevent. It classically correspondsto the P. flexuosum Subzone. Also present are T. gongilense, S.(Jeanrogiceras) tavense (Faraud), Choffaticeras massipianum (Per-vinquière), the total range of which remains unknown. Bioevent F iscorrelated with the middle part of the W. coloradoense Zone (P.flexuosum Subzone).

In the study area this bioevent, which has a relatively widegeographical distribution, rather than the less well-distributedbioevent E, represents the real marker of the Lower Turonianfrom Morocco to Oman.

Bioevents G1eG2eG3. These are the most diversified bioevents,with very good markers such as Thomasites rollandi (Thomasand Peron), Fagesia peroni Pervinquière/levis Renz, Pseudotissotianigeriensis (Woods), W. coloradoense (Henderson) and Wright-oceras. They are correlated with the upper part of the Colo-radoense Zone (middle part of the Lower Turonian), correspondingto the V. (Greenhornoceras) birchbyi Subzone, which more or lesscalibrates with the T. rollandi Subzone of the southern Tethysmargin. Paramammites polymorphus (Pervinquière) and S. (Jean-rogiceras) ssp. occur also within this bioevent. This subzone istentatively subdivided into three parts, with bioevent G1 charac-terized by Pseudaspidoceras barberi Meister, Choffaticeras secur-iforme (Eck), the first Pseudotissotia nigeriensis (Woods) and maybeN. (Betiokyites) gr. pioti (Peron and Fourteau). This association oftaxa could be seen as a marker. Bioevent G2 contains Pseudo-tissotia nigeriensis, Wrightoceras wallsi (Reyment), Eotissotia sim-plex Barber and Choffaticeras quaasi (Peron). Wrightoceras wallsiand combinations of these associations are also seen as a marker.The last of these possible bioevents, G3, groups Hoplitoides ingens(von Koenen) and several Choffaticeras (mainly Choffaticeras luciae(Pervinquière)), Hoplitoides mirabilis Pervinquière, Wrightocerasmunieri (Pervinquière) and rare heteromorph ammonites such asBaculites gr. yokoyamai Tokunaga and Shimizu and Eubos-trychoceras sp. Wrightoceras munieri and Hoplitoides ingenscould be seen as markers. Some Desmoceratidae are present inTunisia.

Remark. In Egypt, Nagm et al. (2010b) proposed a detailed succes-sion for Choffaticeras, and this local proposition is in part followed



here. However, while Choffaticeras massipianum Pervinquière andChoffaticeras securiforme seem to be two of the oldest species andC. luciae one of the youngest, the stratigraphic distribution of theother species varies from one region to another. Different associa-tions of Choffaticeras have been observed, for example in Tunisia ornorthern Nigeria; moreover, the variability of this genus is not yetwell understood.

Correlation. The Lower Turonian (bioevent E) still needs to bedefined in northern Nigeria and is only clearly present in Egypt(Eastern Desert) and in Jordan. Elsewhere, it cannot be determinedwith precision using ammonites. Bioevent F, with P. flexuosum andV. durandi, is a good marker and allows correlations betweenMorocco, Tunisia, northern Nigeria, Egypt and probably Lebanon,Jordan and Oman. The upper part of the Watinoceras coloradoenseZone is well represented throughout the area and allows goodcorrelations for this period, locally permitting more precise sub-divisions into bioevents G1, G2 and G3 (e.g., northern Nigeria andTunisia). Every part of the study area has evidence of at least one ofthese bioevents.

Mammites nodosoides ZoneThis is the final zone of the Lower Turonian (no availablesynonymy).

Bioevent H. Mammites nodosoides (Schlüter) and Kamerunocerasturoniense (d’Orbigny) are classically attributed to this bioevent,even though their total ranges are longer. They probably alreadyappeared earlier, in the T. rollandi Subzone, and the range ofK. turoniense also covers part of the Middle Turonian. This bioeventcan be correlated with the M. nodosoides Zone (M. nodosoidesSubzone).

Associated are Neoptychites cephalotus, H. wohltmanni (vonKoenen), F. superstes (Kossmat) and perhaps some Choffaticeras,taxa with long ranges during the Lower Turonian. In Tunisia, Mor-rowites subdepressus Cobban and Hook occurs within this bioevent.

Correlation. The Mammites nodosoides Zone, corresponding tobioevent H, is missing in Niger and presumably also in the easternpart of the Middle East (Syria, Jordan) and in the Arabian Peninsula.

The succession of 13 bioevents A1 to H allows correlations with thezonation of the Late CenomanianeEarly Turonian, in spite of thefact that many Tethyan taxa are not represented in the stratotypeand that ammonite time ranges remain poorly known. At the zonallevel, all standard zones are recognized and this is also the case atthe subzonal level, although the lowest subzone of the Turonian(W. devonense Subzone) is less clearly evident in the area investi-gated. The period studied corresponds to a time interval of c.3.5 myr, with each bioevent corresponding more or less to a periodof 270,000 years. Thus, the scale of resolution remains only slightlywider and oftenmore questionable than, for example, that for EarlyJurassic ammonites (Meister, 2010).

Remarks. In our opinion, a proliferation of zonations should beavoided. For the Early Jurassic only the consensus standard zona-tion is applied and a similar approach would be desirable for theCenomanianeTuronian, bearing in mind that the stratotype (GSSP)of the Turonian is defined in Colorado (USA). The proposal of Nagmet al. (2010b) for a regional zonation for Egypt (Eastern Desert) isinteresting, but for wider correlations a large synonymy is neces-sary because the zonal concept varies from one author to the next(a zone or subzone being defined by its base only). For Egypt, theregional zonation matches that for the Late Cenomanian, but it isless precise for the Early Turonian.


3. Paleobiogeographical framework

The paleobiogeographical framework of the southern margin ofthe Tethys and adjacent areas (Fig. 7A) for the Late CenomanianeEarly Turonian, is based on the palinspastic reconstitution byBlakey (2011). Several maps (Figs. 7e12) illustrate the distributionof 77 ammonite taxa from Morocco to Oman during this timeinterval.

Bioevent A1During the early Late Cenomanian, the geographical distribution ofNeolobites covers the entire study area, except for the deep marineenvironment of the Tarfaya Basin in the far west of Morocco(Collignon, 1966), as shown in Fig. 7B.

The Neolobites vibrayeanus bioevent (A1) can be followed fromMorocco to Oman. It precisely corresponds to the Calycocerasguerangeri Zone (lower part of the Late Cenomanian) and marksthe maximum southerly extension of the sea on the North Africancraton at this period. Almost everywhere this bioevent seems to beassociated with the onset of the marine transgression during theearly Late Cenomanian.

To the west, in the Pre-African Trough (Morocco), this bio-event appears not to have crossed a NEeSW line that connectsTazougart (Belkassem) to Agoult (Gara Sbaa) and indicates thepossible western border of the shallow sea at this time. To thesouth, the sea reached the south of the Saharan region as far asDamergou in Niger (Meister et al., 1992, 1994). To the east it ispresent at least as far as Oman, as well as in North Africa, theMiddle East and Saudi Arabia. Neolobites is closely linked toshallow-marine environments which marks the influence of thesouthern Tethys ocean in a newly opened sea (transgressivephase), as indicated by frequent small and ‘primitive’ plank-tonic foraminifera (e.g. Morocco and Oman) (Cavin et al.,2010).

Bioevent A2

The distribution of the Acanthoceratinae is more scattered, withCalycoceras covering the whole area from Morocco to Oman, withthe exception of the Middle East. Eucalycoceras seems to berestricted to Algeria and Tunisia. Calycoceras is fairly abundant inOman, but these Acanthoceratinae seem uncommon elsewhere(Fig. 7C).

Bioevent B1Metoicoceras geslinianum is widely represented throughout thearea, confirming its status as good zonal marker. The genus Met-engonoceras appears to be confined to the central part of the areafrom Algeria to the Middle East and northern Nigeria, as doesEuomphaloceras septemseriatum. The genus Euomphaloceras isrecorded from the Tarfaya Basin and (?)Eucalycoceras tenereensis ispresent exclusively in Niger (Fig. 8A).

Bioevent B2In this bioevent, the distribution of Nigericeras gadeni, N. jacqueti,Fikaites and Burroceras seems to follow a longitudinal trend. Solelythe genus Nigericeras is thought to occur to the west in Algeria andto the east in Oman (Fig. 8B).

Bioevent C1The sole widely distributed form for this bioevent is Pseudaspi-doceras, including P. pseudonodosoides. An allied species,P. tassaraensis, is recorded from Niger. Euomphaloceras costatum isknown only from Tunisia and Egypt (Eastern Desert), whileNigericeras jacqueti involutus has been recorded from Niger andTunisia (Fig. 8C).


Cenomanian - Turonian (93.5 my)

after R. Blakey, 2011

Calycoceras naviculare (Mantell)

Calycoceras gr. haugi (Pervinquière)

Bioevent A2

*

*

*

Eucalycoceras pentagonum (Jukes-Browne)

EE Eucalycoceras

E

C Calycoceras

C

A

Neolobites vibrayeanus (d’Orbigny)

Neolobites fourtauiPervinquière

N Neolobites

N

Bioevent A1

Cunningtoniceras tinrhertense Collignon

**

N

B

C

Fig. 7. Paleobiogeographic reconstitution for the CenomanianeTuronian after Blakey (2011) (A) and ammonite distribution for bioevents A1 and A2 along the southern Tethysmargin from Morocco to Oman (B and C). The yellow line indicates the western and southern limits of distribution of the genus Neolobites [Illustrations of ammonites are from


Please cite this article in press as: Meister, C., Piuz, A., Late CenomanianeEarly Turonian ammonites of the southern Tethysmargin fromMoroccoto Oman: Biostratigraphy, paleobiogeography and morphology, Cretaceous Research (2013), http://dx.doi.org/10.1016/j.cretres.2013.03.009


Bioevent C2Characteristic forms of this period are not abundant and theirdistributions are restricted to the central part of the area studied,with Vascoceras gamai present from Tunisia to Egypt and innorthern Nigeria, and to a lesser extent (?)Neocardioceras in Algeriaand Vascoceras barcoicensis in Tunisia (Fig. 9A).

Bioevent DThis bioevent, which characterizes the Late Cenomanian, is domi-nated by Vascoceratidae (Vascoceras cauvini, V. glabrum, V. crassum,Rubroceras burroense), which have the widest geographic distri-bution, covering the whole area, except for Oman, V. cauvini beingthe most abundant. Fikaites gr. varicostatum is restricted to sub-Saharan regions (Algeria and northern Nigeria). Pseudaspidoceraspaganum has been recorded exclusively from Morocco, Algeria andnorthern Nigeria (Fig. 9B and C).

A few rare taxa such as Spathites (Jeanrogiceras) subconci-liatum, Vascoceras globosum and V. tectiforme are not widelydistributed geographically; stratigraphically they cross the Cen-omanianeTuronian boundary and are also present in bioevent E(Fig. 10A).

Bioevent ETwo taxa are characteristic of this bioevent, with Watinocerasdistributed in the west (Tarfaya Basin in Morocco) and in the south(southern Benue in Nigeria) and with Vascoceras proprium innorthern Nigeria and in more easterly regions (Egypt and Jordan)(Fig. 10B).

Bioevent FThe index species, Pseudaspidoceras flexuosum, covers the mainregions, although it is absent further east (Arabian Peninsula). Thedistribution of Vascoceras durandi follows a latitudinal trend;surprisingly, it is absent in southern regions (Niger, northernNigeria) where sphaerocone Vascoceras are very abundant andhighly diverse. Spathites (Jeanrogiceras) tavense is known onlyfrom Tunisia and possibly the Negev desert (Israel). Thomasitesgongilense, described from Nigeria, also occurs in the EasternDesert (Egypt) and doubtfully in the Middle East and Oman(Fig. 10C).

Bioevents G1eG3Thomasites rollandi has a geographic distributionwhich is similar tothat of Vascoceras durandi in bioevent F, with a latitudinal trend.Pseudotissotia nigeriensis also has awide distribution covering mostof the area, as does Fagesia peroni/levis which extends as far asOman. Paramammites polymorphus is present along the Trans-Saharan sea from Tunisia to northern Nigeria, in the Middle Eastand Oman. Watinoceras coloradoense is restricted to the westernpart (Tunisia, Morocco) (Fig. 11A).

Bioevents G1eG2. The ammonites of these two bioevents donot yield reliable data for the western and central Maghreb.Choffaticeras (C. quaasi and C. securiforme) is present in the cen-tral part from Tunisia into the Middle East and northern Nigeria.Wrightoceras wallsi is restricted to the southern part of theSaharan sea (Niger, Nigeria), and Eotissotia simplex has beenrecorded only from northern Nigeria and Oman. Pseudaspidocerasbarberi has a fairly longitudinal distribution from Nigeria toTunisia (Fig. 11B).

Pervinquière, 1907, pl. 8, figs. 4a, 5a, pl. 14, fig. 1; Wright and Kennedy, 1990, pl. 78, fig. 3; Mei9BeC, p. 202, fig. 10AeB]. Remarks: The ammonites illustrated (without scale) are provided tothe study area.


Bioevent G3. The distributions of species of Choffaticeras such asC. segne, C. pavillieri and C. luciae cover the entire area. Their dis-tribution and diversity mean that they represent the main taxa inbioevents G1-G3. Heteromorph forms, i.e., Eubostrychoceras(Eastern Desert, Egypt) and Baculites yokoyamai (Tunisia), are veryrare and geographically restricted (Figs. 11C and 12A).

In bioevents G1, G2, G3 and H, some longer-ranging taxa such asHoplitoides wohltmanni, Neoptychites cephalotus and Fagesia super-stes show a wide distribution throughout the study area, althoughF. superstes is unknown in the western and central Maghreb. In theArabian Peninsula only the genus Fagesia is on record (Fig. 12B).

Bioevent HMammites nodosoides and Kamerunoceras turoniense show a widedistribution, except in Arabian Peninsula, where no data for thisperiod are available (Fig. 12C).

Unsurprisingly, the best reproducible bioevents, A1 and FeG (G1,G2, G3) are closely associated with global sea level changes(Hardenbol et al., 1998; Hallam and Wignall, 1999; Sharland et al.,2001), despite local tectonic and environmental constraints.

A1 is connected to the marine transgression onto the Africancraton, more generally corresponding to the major sea level riseduring the early Late Cenomanian (lower part of the C. guerangeriZone). During this period, we can trace and precisely date theextension of the sea by means of the distribution pattern of Neo-lobites vibrayeanus as far west as the Goulmima area (Morocco),south into the Damergou (Niger) and east into the Central Adamfoothills (Oman).

Bioevents FeG1, G2, G3, corresponding to the middle and upperpart of theW. coloradoense Zone, are concomitant with the generalsea level rise during the Early Turonian. In part, this could explainthe Tethys-South Atlantic marine connection via the Benue Trough(Nigeria) that occurs during this period. This short-lived marineevent corresponds, at least, to the Pseudotissotia nigeriensis andWrightoceras wallsi bioevents G1 and G2 (upper W. coloradoenseZone) (Meister et al., 1992, 2003). Bioevents FeG (G1, G2, G3)represent a homogenization of the fauna throughout the wholearea, just prior to a new and short-lived regressive marine trendcorresponding more or less to bioevent H, and probably explainingthe deficit of information for the M. nodosoides Zone in the easternregions.

To a lesser extent, bioevent C1, at the base of the N. juddii Zone,is also well represented in the western part up to the Middle East. Ifwe follow the interpretation of Hallam and Wignall (1999) for theeustatic curve, it could be situated just near the turnover betweenthe brief regression peak, immediately prior the N. juddii Zone andthe transgression recovery. The same authors placed an extinctionevent within the Latest Cenomanian. This crisis could explain thepaucity of information from around the CenomanianeTuronianboundary in the area studied.

The low diversity and rarity and/or absence of species of thesubfamilies Acanthoceratinae, Euomphaloceratinae and Mammiti-nae in the study area and the abundance and high diversity of thePseudotissotiinae (Choffaticeras, Pseudotissotia orWrightoceras) andparticularly of the family Vascoceratidae confer an original char-acter to the province of the southern margin of the Tethys and at alarger scale, to the Tethyan realm (¼warm-water VascoceratidProvince of Wiedmann, 1988).

ster et al., 1992, pl. 1, fig. 1; Meister et al., 1994, pl. 7, fig. 1; Amédro et al., 1996, p. 199, fig.yield data on the morphology of taxa; wherever possible these are based on taxa from


Euomphaloceras septemseriatum (Cragin)

Metengonoceras dumbli (Cragin)

Metengonoceras acutum Hyatt

(?) Eucalycoceras tenereensis (Meister et al.)

Metoicoceras geslinianum (d’Orbigny)

Bioevent B1

+

+

XX X

X

X

X

X

X

X

M M Metengonoceras

M

E Euomphaloceras

E

A

Nigericeras gadeni (Chudeau)

? N Nigericeras

Nigericeras jacquetiSchneegans

? Fikaites africaensis Meister et al.

? N

? N

Bioevent B2

F Fikaites

B Burroceras

B

B

F

F

B

Pseudaspidocerastassaraensis Meister et al.

Pseudaspidoceras pseudonodosoides (Choffat)

PPseudaspidoceras

PP

P

Bioevent C1

Euomphaloceras costatumCobban et al.

*

*Nigericeras jacqueti

involutus Meister et al.

P

*C

+

Fig. 8. Ammonite distribution patterns for bioevents B1 (A), B2 (B) and C1 (C) along the southern Tethys margin from Morocco to Oman [Illustrations of ammonites are fromSchneegans, 1943, pl. 7, fig. 2; Kennedy, 1988, pl. 9, figs. 11, 12; Cobban et al., 1989, fig. 83DeE; Meister et al., 1992, pl. 1, fig. 7; pl. 2, figs. 1, 6; pl. 3, fig. 1; pl. 4, fig. 3; pl. 7, fig. 5; pl. 10,fig. 1; Amédro et al., 1996, p. 201, fig. 9AeB; Meister and Abdallah, 2005, pl. 4, Fig. 3; Nagm and Wilmsen, 2012, p. 70, fig. 6B].



Vascoceras cauvini Chudeau

Bioevent D

Nigericeras cf. scotti Cobban

Pseudaspidoceras paganum Reyment- footeanum (Stoliczka)

Rubrocerasburroense Cobban et al.

*

*

Vascocerascrassum (Furon)

Vascoceras glabrum (Barber)? ?

Bioevent D

Fikaites gr. varicostatum Zaborski

Vascoceras gamai Choffat

Bioevent C2

Vascoceras barcoicensis ChoffatN Neocardioceras

? N

R Rubroceras

R

A

B

C

Fig. 9. Ammonite distribution patterns for bioevents C2 (A) and D (B and C) along the southern Tethys margin fromMorocco to Oman [Illustrations of ammonites from Choffat, 1898,pl. 17, fig. 1; Cobban, 1971, pl. 19, figs. 1e3; Meister, 1989, pl. 1, fig. 1; pl. 9, fig. 4; pl. 16, fig. 1; Cobban et al., 1989, fig. 75QeR; Meister et al., 1992, pl. 8, fig. 3; pl. 7, fig. 1; Meister andAbdallah, 2005, pl. 13, Fig. 1, 2; Meister and Abdallah, 2012, pl. 10, fig. 4].


Please cite this article in press as:Meister, C., Piuz, A., Late CenomanianeEarly Turonian ammonites of the southern Tethysmargin fromMoroccoto Oman: Biostratigraphy, paleobiogeography and morphology, Cretaceous Research (2013), http://dx.doi.org/10.1016/j.cretres.2013.03.009

Vascoceras globosum (Reyment)

Vascocerastectiforme(Barber)

Bioevents D-E Spathites (Jeanrogiceras)subconciliatum (Courtiller) *

*

*

Vascoceras proprium Reyment

Bioevent E

W Watinoceras sp.

W W W W W W

W W

Thomasites gongilensis (Woods)

Pseudaspidoceras flexuosum Powell

Vascoceras durandi (Thomas and Peron)* **

***?

?

Bioevent F

Spathites (Jeanrogiceras )tavense (Faraud)

*

P Pseudaspidoceras

W W

?

P?

A

B

C

Fig. 10. Ammonite distribution patterns for bioevents DeE (A), E (B) and F (C) along the southern Tethys margin from Morocco to Oman [Illustrations of ammonites are fromCollignon, 1966, pl. 19, figs. 14, 15; Barber, 1957, pl. 7, fig. 2; Wiedmann and Kauffman, 1978, pl. 7, fig. 2; Meister, 1989, pl. 8, fig. 1; pl. 19, fig. 2; Meister and Abdallah, 2005, pl. 7, fig. 1;pl. 12, fig. 2; pl. 26, fig. 1].



? ?

?

Thomasites rollandi (Thomas and Peron)

Bioevents G1-G2-G3

Pseudotissotia nigeriensis (Woods)

P

P

*

*

*

*

*

*

*

?

Paramammites polymorphus(Pervinquière)

Fagesia peroni Pervinquière- levis Renz

Pseudaspidoceras barberi Meister

**

Bioevents G1-G2

Choffaticeras securiforme (Eck)

O

O

O

Choffaticeras quaasi (Peron) Wrightoceras wallsi (Reyment)

Eotissotia simplex Barber

*

O

Hoplitoides ingens (von Koenen)

Hoplitoides mirabilis Pervinquière

Bioevent G3

Wrightoceras munieri(Pervinquière)

W Wrightoceras

*

*

*

*

W

*

Pseudotissotia

Watinoceras coloradoense (Henderson)O

OO

?

A

B

C

Fig. 11. Ammonite distribution patterns for bioevents G1, G2, G3 (AeC) along the southern Tethys margin from Morocco to Oman [Illustrations of ammonites are from Barber, 1957,pl. 3, fig. 3; pl. 24, fig. 2; Meister, 1989, pl. 2, fig. 2; pl. 23, fig. 1; pl. 27, fig. 4; Zaborski, 1990, p. 8, fig. 27; Chancellor et al., 1994, pl. 2, figs. 2, 3; pl. 9, figs. 4, 5; pl. 14, figs. 8, 10; pl. 28,figs. 2, 3; pl. 35, figs. 2, 3; Meister and Abdallah, 1996, pl. 9, fig. 1; Zaborski, 1996, p. 82, fig. 55; Meister and Abdallah, 2005, pl. 23, fig. 1].


Please cite this article in press as:Meister, C., Piuz, A., Late CenomanianeEarly Turonian ammonites of the southern Tethysmargin fromMoroccoto Oman: Biostratigraphy, paleobiogeography and morphology, Cretaceous Research (2013), http://dx.doi.org/10.1016/j.cretres.2013.03.009

Neoptychitescephalotus(Courtiller)

Bioevents G-H

Hoplitoideswohltmanni

(von Koenen)

Fagesiasuperstes(Kossmat)

*

***

*

*

*

Choffaticeras luciae (Pervinquière)

CC Choffaticeras

CC

Choffaticeras sinaiticum (Douvillé)

Choffaticeras pavillieri(Pervinquière)

*

*

*

*

X

X

X

X

Bioevent G3

E Eubostrychoceras

Baculites cf. yokoyamai Tokunaga and Shimizu

EChoffaticeras segne (Solger)

A

B

Mammites nodosoides (Schlüter)

?

Kamerunoceras turoniense (d’Orbigny)

Bioevents H

M Mammites

M

K Kamerunoceras

K

C

Fig. 12. Ammonite distribution patterns for bioevents G3 (A), G-H (A and B) and H (C) along the southern Tethys margin fromMorocco to Oman [Illustrations of ammonites are fromFreund and Raab, 1969, pl. 9, fig. 3; Chancellor et al., 1994, pl. 4, figs. 2, 3; pl. 13, figs. 1, 2; Meister and Abdallah, 1996, pl. 6, fig. 1; pl. 11, fig. 1; pl. 12, fig. 1; pl. 13, fig. 1; Wright et al.,1996, p. L246, fig. 4b; Meister and Abdallah, 2005, pl. 8, fig. 2; pl. 18, fig. 2; Nagm and Wilmsen, 2012, p. 82, fig. 19A].




Details of this picture are more complex; some examples serveto illustrate this fact. Evidently, this wide province was open tomarine influence and faunal exchange with the northern Tethyanmargin (Europe and Central Asia), with the Eastern Pacific via theCentral Atlantic Ocean (Kennedy and Cobban, 1976; Wiedmann,1988; Lehmann and Herbig, 2009), sporadically directly with theSouth Atlantic through the Trans-Saharan sea (Meister et al., 1992,1994, 2003) and south-east to the Indian Ocean (Madagascar andIndia).

Strong endemism is suggested by rare taxa such as Nigericerasgadeni, N. jacqueti, the genus Fikaites, T. gongilense (maybe recordedfrom France; see Kennedy et al., 2003), Wrightoceras wallsi andseveral species of Vascoceras (V. crassum, V. globosum s. s., V. glabrumand V. tectiforme). Choffaticeras also reveals an endemic trend alongthe southern margin of the Tethys, mainly due to their abundanceand taxonomic diversity, although the genus is known inMadagascar (Basse, 1931) and in the Western Interior (Cobban andScott, 1973). Choffaticeras luciae or C. quaasi, for example, remainrestricted to this margin.

Neolobites vibrayeanus s. s. seems to be endemic to the TethyanRealm (southern and northern margin of the Tethys); its presencein South America is doubtful (Benavides-Caceres, 1956) but,if confirmed, this taxon would show a clear subequatorialdistribution.

Pseudaspidoceras pseudonodosoides and Vascoceras gamai showsome Tethyan affinities; however, both are also known from theWestern Interior (Eastern Pacific) (e.g., Cobban et al., 1989) and, inthe case of P. pseudonodosoides, from the South Atlantic (Brazil)(Gale et al., 2005).

Cosmopolitan taxa, which are mainly represented by Neo-ptychites cephalotus, Vascoceras durandi, Thomasites rollandi, Fagesiasuperstes-tevesthensis, Mammites nodosoides and, to a lesser extent,by Metoicoceras geslinianum, Pseudaspidoceras flexuosum, Wright-oceras munieri, Kamerunoceras turoniense and Fagesia peroni/levis,help calibrate regional sequences. Many other taxa, such as Para-mammites polymorphus, Metengonoceras dumbli, M. acutum, Cibo-laites,Hoplitoides mirabilis and H. wohltmanni, showa subequatorialdistribution along the Tethyan Realm and Eastern Pacific (W.I.) viathe Central Atlantic (Cobban and Hook, 1980; Renz, 1982). This isalso the case for Vascoceras proprium, considered the marker of thebase of the Turonian in the southern Tethyan margin, which is alsorecorded in the eastern Pacific (USA) (Kennedy et al., 1987). Simi-larly, Euomphaloceras gr. costatum has also been recorded from thenorthern Tethyan margin (southern England), the South Atlantic(Brazil) and the eastern Pacific (W.I.) (Wright and Kennedy, 1981;Cobban et al., 1989; Gale et al., 2005).

Faunal exchange directly with the South Atlantic via the BenueTrough appeared episodically during the Turonian, with the dis-tribution of some Tethyan forms such as Pseudotissotia nigeriensis,an endemic Saharan form known from as far east as Gabon (Meisteret al., 2003) and Brazil (Gale et al., 2005), or with H. ingens, also ofTethyan affinity, as far as Cameroon (Reyment, 1955), and with thepresence of other Tethyan forms such as Wrightoceras wallsi, Vas-coceras globosum and V. simplex in Brazil (Reyment and Tait, 1972;Gale et al., 2005). It should be noted that some authors haveconsidered that the CentraleSouth Atlantic marine connection hadbeen open since the Aptian (e.g., Jacobs et al., 2009) or the EarlyAlbian (e.g., Torsvik et al., 2009).

On the southeast African coast there are a lot of taxa in commonwith Madagascar (Collignon, 1965), such as Kamerunoceras tur-oniense, Pseudaspidoceras flexuosum, Mammites nodosoides, Fagesiasuperstes/tevesthensis, N. cephalotus, and further east with India (e.g.,Neoptychites cephalotus, Fagesia superstes/tevesthensis) (Kossmat,1897). Some taxa are also shared with the Far East (Japan), such asVascoceras durandi, N. cephalotus, Fagesia superstes/tevesthensis and


Mammites (e.g., Matsumoto, 1973, 1978) and with northwest Europe(e.g., Wright and Kennedy, 1990), such as C. naviculare,E. septemseriatum, Eucalycoceras pentagonum, which are also present,though rare on the southern Tethyan margin.

The presence of some Spathites (Jeanrogiceras) in Tunisia high-lights the close connections with the northern Tethyan margin(Europe), such as the Iberian Peninsula and southern France, wherethis subgenus is abundant (Wiedmann, 1964; Thomel, 1992;Kennedy, 1994; Barroso-Barcenilla, 2007).

Even direct East Pacific (Western Interior) influences can bediscerned through the Central Atlantic, for example in Tunisia withthe presence of Nigericeras cf. scotti, Rubroceras burroense or Vas-coceras cf. barcoicensis exile (Cobban et al., 1989; Meister andAbdallah, 2012). This influence is underlined by the presence ofWatinoceras in southern Nigeria (Zaborski, 1993), in the far west ofMorocco (Tarfaya Basin) (Collignon, 1966) and in Tunisia.

4. Morphological framework

During this period of general sea level highstand, biota inhabi-ted epicontinental seas belonging to relatively shallow basins orplatforms, except for the deeper Tarfaya Basin in the far west ofMorocco.

MorphogroupsTwo morphogroups, one based on ornamentation, the other onshell morphology, are discussed, with only a qualitative interpre-tation (Fig. 13). For shell (conch) morphology we use the nomen-clature of Westermann (1996) and Oloriz et al. (2002). All taxa areshown in Figs. 2 and 3. Twelve shell morphologies are distin-guished: (1) platyconeeplanorbicone; (2) evolute platycone; (3)involute platycone; (4) discocone; (5) involute discocone; (6) oxy-coneediscocone; (7) oxycone; (8) platyconeesubsphaerocone; (9)discoconeecadiconeesphaerocone (10) subsphaerocone; (11)sphaerocone; (12) vermicone and orthocone. The circles indicatethe proportion of taxa with each shell morphology occurring in azone. The position of the circles in the figure indicates more or lessprecisely the morphology of the shell. The morphology rarelymatchs the morphopatterns exactly; occasionally the position ofthe circles is situated in between different morphopatterns and thedefinition of the shell is composite. The piecharts indicate thepercentage of ornament intensity for each zone with four levels ofornamention: (1) smooth; (2) slightly ornamented; (3) orna-mented; (4) spiny.

In the C. guerangeri Zone, the most frequent morphologies arethe oxyconeesuboxycone and involute platycone forms, with theornamented ones slightly predominant. In the M. geslinianumZone, there is a shift to involute platycone and discocone mor-phologies, with an increasing proportion of ornamented forms. Theoxycone and associated morphologies are very rare.

In the N. juddii Zone, conch morphologies are more diversewithout a dominant morphology, although platycones (evolute andinvolute) form the largest group. Note that subsphaerocone andsphaerocone morphologies appear in this zone. Oxycones andassociated morphologies remain poorly represented. For theornamentation, the proportion of the morphogroups is morebalanced than in the other zones but the ornamented forms alwaysdominate.

In the W. coloradoense Zone, the range of morphologies ismore diverse, with platyconeeplanorbicone, orthoconeevermi-cone, sphaerocone and suboxycone forms represented, althoughthe sphaerocone and suboxycone forms are still dominant. Forthe first time, smooth and slightly ornamented formspredominate.


1

2

3

4

5

6

7

9 10

11

12

C. guerangeri Zone

8

1

2

3

6

7

8

9 10

11

12

M. geslinianum Zone

4

5

1

2

3

4

5

6

7

8

9 10

11

12

M. judii Zone

1

2

3

4

5

6

7

8

9 10

11

12

W. coloradoense Zone

1

2

3

4

5

6

7

8

9 10

11

12

M. nodosoides Zone

1

3

4

5

6

7

8

9 10

11

12

2

smoothslightly ornamentedornamentedspiny

123456789101112

sphaeroconeserpenticone

planorbicone cadicone

platycone

discocone

oxyconeorthocone

vermicone

= 10 %

Fig. 13. Evolution and distribution of shell shapes and ornamentation for Late CenomanianeEarly Turonian ammonites along the southern Tethys margin from Morocco to Oman[modified after Westermann, 1996; Oloriz et al., 2002]. (1) platyconeeplanorbicone, (2) evolute platycone, (3) involute platycone, (4) discocone, (5) involute discocone, (6) oxyconeediscocone, (7) oxycone, (8) platyconeesubsphaerocone, (9) discoconeecadiconeesphaerocone, (10) subsphaerocone, (11) sphaerocone, (12) vermicone and orthocone.


In the M. nodosoides Zone, more extreme morphologies arepresent with platyconeeplanorbicone, oxycone and suboxyconeand, to a lesser extent, sphaerocone forms. The proportion ofsmooth forms is similar to that of the N. juddii Zone and equivalentto that of the ornamented ones.


As expected, there is concomitance between the suboxyconeand sphaerocone morphologies and smooth and slightly orna-mented forms. In contrast, the presence of platycone (evolute andinvolute) or platyconeeplanorbicone morphologies is associatedwith ornamented and spiny forms. No real trend can be seen as far



as the evolution of ornamentation for the period studied isconsidered, each period (zone) having its own characteristics.Smooth and slightly ornamented forms occur in similar pro-portions, approximately 43 per cent in the C. guerangeri, M. juddiiand M. nodosoides Zones, they are weakly represented in the M.geslinianum Zone (28 per cent), but dominate assemblages in theW. coloradoense Zone (68 per cent). Conversely, the ornamentedand spiny forms predominate, except for theW. coloradoense Zone,with a maximum in the M. geslinianum Zone (72 per cent).

Considering the evolution of conch morphology through time,several observations can be made: the oxycone (7) and suboxycone(6) morphologies, well represented and fairly constant in propor-tion in the C. guerangeri (46 per cent), W. coloradoense (41 percent) and M. nodosoides (43 per cent) zones, show a drastic declineduring the M. geslinianum and M. juddii Zones, replaced by invo-lute platycone (3) and discocone (4) forms, respectively, then byinvolute platycone (3), evolute platycone (2) and disco-cadi-sphaerocone (9), subsphaerocone (10) and sphaerocone (11)morphologies.

The group of platyconeeplanorbicone (1) and evolute platycone(2) are relatively rare, except in the N. juddii (25 per cent) and M.nodosoides (29 per cent) Zones. The involute platycones (3), dis-cocones (4) and platyconeesubsphaerocones (8) are quite wellrepresented during the Late Cenomanian, with a maximum in theM. geslinianum Zone (72 per cent). In contrast, these morphologiesare totally absent in the Early Turonian.

The sphaerocone (11), subsphaerocone (10) and allied mor-phologies (9) appear in the N. juddii Zone, but are never dominantamong the fauna; their maximum is in the W. coloradoense Zone(29 per cent).

For heteromorph shell shapes (12), their presence (vermiconeEubostrychoceras and orthocone Baculites) data remain anecdotalwith 5 per cent of the fauna and only recorded from the W. colo-radoense Zone [V. (G.) birchbyi Subzone]. This could indicate in-fluence from more open seas, if we follow the interpretationfavoured by Westermann (1996).

5. Conclusion

A first synthesis of the spatial and temporal distribution of LateCenomanianeEarly Turonian ammonites fromMorocco to Oman hasrevealed 13 bioevents that can be correlated throughout the prov-ince and allows paleobiogeographic distributional patterns to bedefined. These bioevents are correlatedwith the zonation defined forthe stratotype, even though not all zonal or subzonal index speciesare represented along the southern Tethys margin, especially for theCenomanianeTuronian boundary. Specifically, the limits of zonesand subzones of the scheme possibly do not appear to correspondexactly to the potential limits of the different ammonite bioeventsdetermined herein. The main markers throughout the provinceduring the Late Cenomanian are Neolobites vibrayeanus, Calycocerashaugi/guerangeri, C. naviculare and Eucalycoceras pentagonum for theCalycoceras guerangeri Zone; Metoicoceras geslininaum, Euomphalo-ceras septemseriatum, Nigericeras gadeni, Nigericeras jacqueti for theMetoicoceras geslinianum Zone and Pseudaspidoceras pseudonodo-soides and several Vascoceras (among them V. gamai, V. cauvini) forthe Neocardioceras juddii Zone. For the Early Turonian, P. flexuosum,V. durandi, Thomasites rollandi, Fagesia peroni/levis, Pseudotissotianigeriensis, Wrightoceras wallsi, Hoplitoides ingens, Wrightocerasmunieri, several Choffaticeras and Hoplitoides and, to a lesser extent,V. proprium are goodmarkers for theWatinoceras coloradoense Zoneand Mammites nodosoides and Kamerunoceras turoniense for theMammites nodosoides Zone.

Endemic trends for the southern margin of the Tethys areobservable at two levels: in more general terms, by the rarity of


members of the subfamilies Acanthoceratinae, Euomphalocer-atinae and Mammitinae (mainly stratigraphic key markers of NWEuropean affinity) and the contrasting abundance and high di-versity of Pseudotissotiinae and Vascoceratidae. Notable differ-ences exist between the northern and southern margins, more orless stressed in the western part [e.g., with the distribution ofSpathites (Jeanrogiceras)]. On a smaller scale, the presence of severaltaxa such as Nigericeras (N. gadeni, N. jacqueti), Fikaites, Thomasitesgongilense and several species of Vascoceras, reveals a strong localendemism in Saharan regions, the south-central portion of the areainvestigated.

In addition to cosmopolitan faunal elements such as Fagesiasuperstes/tevesthensis or Pseudaspidoceras flexuosum or the sub-equatorially distributed forms such as Paramammites polymorphus orHoplitoides mirabilis, faunal exchanges with other paleobiogeo-graphical realms are indicated by the presence, in the western part,of PacificeCentral Atlantic forms such as Nigericeras cf. scotti,Rubroceras burroense or Vascoceras cf. barcoicensis exile. On the otherhand, the presence in the South Atlantic of Pseudotissotia nigeriensis,Wrightoceras wallsi, Vascoceras simplex and V. globosum indicatesdirect Tethyan influence via the Trans-Saharan sea even if theEquatorial Atlantic Seaway also provided interchange between theNorth Atlantic and South Atlantic faunas. However, records for thesetaxa from the North and Central Atlantic are uncertain. A similarfauna in southeast Africa (Madagascar), and even in India, alsodemonstrates a close connection between these different realms.

There are no real trends in the variability of the morphology ofthese ammonites in space and time. Each period (zone) has its owncharacteristics. Possibly, this is due to the general sea level high-stand and to a relatively homogeneous environment along thesouthern Tethyan margin during this time period. The best repro-ducible bioevents (A1 in the C. guerangeri Zone and FeG in the W.coloradoense Zone) are closely linked to global sea level changes.The first bioevent, A1, shows little morphological and taxonomicdiversity, with oxyconeesuboxycone, slightly ornamented formsand rare ornamented platycones. It is closely related with themarine transgression onto the African craton and onto the ArabianPeninsula during the early Late Cenomanian. In contrast, the sec-ond (bioevents FeG1, G2, G3) is the most diversified, with a highnumber of taxa and with almost all morphological forms, inclusiveof heteromorphs, although dominated mainly by suboxycone andsphaerocone, slightly ornamented forms. This episode is concom-itant with a sea level rise during the Early Turonian. It also coincideswith direct marine connections between Tethys and South Atlanticvia the Benue Trough. During the middle-late Late Cenomanian (M.geslinianum and N. juddii Zones), in between two marine trans-gresssive phases, the oxycone and suboxycone forms disappearalmost completely, while ornamented platycones develop. In thelate Early Turonian (M. nodosoides Zone), a marine regressiveperiod starts, and morphologies predominantly comprise orna-mented evolute platycone and relatively smooth suboxyconeforms.

If an extinction event did occur during the latest Cenomanian(see above), this crisis could explain the rarity of ammonites andthus the dearth of data from around the CenomanianeTuronianboundary along the epicontinental seas of the southern Tethyanmargin, which probably were more sensitive to environmentalconstraints such as sea level variations.

Acknowledgements

We thank John Hollier (Natural History Museum of Geneva) forlinguistic correction; the journal reviewers and the handling editor,John W.M. Jagt (Natuurhistorisch Museum Maastricht) for helpfulcomments on an earlier typescript. Salim Omar Al-Ibrahim,



Director General of Minerals (Ministry of Commerce and Industryof Oman) and Ali Al Rajhi, Director of Survey and Research arethanked for their logistic support.

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Late Cenomanian–Early Turonian ammonites of the southern Tethys margin from Morocco to Oman: Biostratigraphy, paleobiogeography and morphology