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Chapter 83. The biostratigraphy of Cretaceous ostracods from Oman
1188 J. ATHERSUCH
The biostratigraphical data presented herein is based on observations of cuttings samples from
6 wells in the western part of Oman bordering Saudi Arabia (Text-fig. 1).
These data are summarised on Text-fig. 2 which records the stratigraphical ranges of the first
downhole occurrences of each species. Selected index species are also depicted in Text-fig. 5.
All the species listed in Text-fig. 2 are illustrated on Plates 1-5.
Text-figures 3 and 4 compare the stratigraphical ranges of each of these species from Oman with
their previously recorded distributions in the Middle East and North Africa. The text provides
information from a variety of sources on their geographical distribution and stratigraphical
significance. The ages quoted from non-BP sources are those provided by the originating authors,
and in the case of the Oman wells, formation “ages” are in-house assignments based on
palaeontological and regional geological considerations.
References to taxomonic names from unpublished literature are enclosed by quotation marks,
thus “ ”. Previously undescribed species have been given BP (Sunbury) reference codes with the
prefix OMN and all of the illustrated specimens are housed in the BP (Sunbury) reference collection.
Text-figure 1 shows a global reconstruction and a lithofacies map of the Arabian Peninsula for
CENOMANIAN TETHYAN SHELF AREAS I N
N.AFRICA AND THE ARABIAN PENINSULA
SHALLOW CARBONATE SHELF
DEEP CARBONATE SHELF
1-Lithofacies map of the Arabian Peninsula during the Cenomanian (data from various sources).
AGE 8 LITHOSTRATIGRAPHY
(Ranges o f t o p occurrences
i n cuttings f r o m several wells:
Ages and lithostratigraphy based
on BP d a t a )
Hornibrookella divergens 81-Furaih
Brachycythere sp. (OMN I )
Aphrikanecythere phumatoides Damotte EL O e r t l i
Holcopocythere bassiporosa / f a l s o c u l o t a Al-Furoih
Paragrenocythere g r a v i s / Al Furaih
Phalcocythere r e c t a n g u l a r i s / hebes 81-Furaih
Phyrocythere dextrodigitota Al-Furai h
"Eobuntonia c u r t a " ( S a y y a b )
Buntonia I R E 9 G r o s d i d i e r
Occultocythereis proro Al-Furaih
B r a c h y c y t h e r e sp. ( O M N 2 )
? Mehesella c f . iRC 23 Grosdidier
Soudanella dolabrata Al-Furaih
Reticytheretta sp. ( O M N 8 )
Metacytheropteron I R L 3 Grosdidier
Cytherella posterosuicata Al-Abdul-Razzaq
Brachycythere sp. ( O M N 3)
P t e r y g o c y t h e r e sp. (OMN 7 )
Ovocytheridea cf. producta G r e k o f f
B r a c h y c y t h e r e sp. ( O M N 4)
B r a c h y c y t h e r e sp. ( O M N 5 )
B r a c h y c y t h e r e sp. ( O M N 2 )
Brochycythere cf. sapucariensis Krommelbein
Brachycythere cf. I R E 10 Grosdidier
Veeniacythereiscf. m a g h r e b e n s i s ( Bassoullet a D a m o t t e )
Veeniacytherels j e zzineensls Bischoff
Peleriops elasiodictyota Al-Abdul- Rozzoq
Peleriops u l o s a Al-Abdul-R.azzaq
M e t a c y t h e r o p t e r o n b e r b e r i c u s Bassoullet and D o m a t t e
Cythereis algeriana Bassoullet a Damotte
Veeniacythereis streblolophata Al-Abdul-Razzaq 8 Grosdldier
Cytherella khaiidrazzaqi. AI-A bdul-Razzaq
C y t h e r e l l a ,ahmadiensis Al-Abdul- Razzaq
C y t h e r e l l a kuwaitensis Al-Abdul-Razzoq
cf. inpendula" Al-Abdul-Razzaq
Cytherella gigantosulcata Rosenfeld
Eocytheropteron retroversicardinatum Al-Abdul-Razzaq
Glenocythere triangularis Al-Abdul-Razzaq
s p ( O M N) ; 1
Al- Abdul - R a z z aq
Glenocythere reticulata 81-Abdul-Razzaq
V e e n i a sp (OMN 12)
Ahmadiura cf. d i c t y o t a Al-Abdul - Razzaq
Meiacytheropteron IR C 10 Grosdidier
Glenocythere bahreinensis A l - A b d u l - Razzaq
Peleriops sphaerommata AI-A bdul-Razzaq
Cythereis cf. f a h r i o n i B l s c h o f f
Cytherella sp ( O M N 11)
Schuleridea I R J 15 Grasdidirr
Schulerideo baidarensis Damotte EL S t Marc
? Schuleridea sp. ( O M N 9 )
indet. sp. I R P 6 Grosdidier
Cythereis cf. IRK 26 Grosdidier
Planileberis cf. malzi ( B i s c h o f f )
2Stratigraphical distribution of Cretaceous ostracods from Oman.
1190 3. ATHERSUCH
the Cenomanian, with relative positions of Aptian, Cenomanian and Maastrichtian shorelines and
equators. Data used in the compilation of this map come from numerous sources including Murris
(1980), Saint-Marc (1978) and the BP palaeoreconstruction data base.
Only one well yielded ostracods in the Kharaib and Shu’aiba Formations. The sparse fauna
included Cythereis cf. IRK26 Grosdidier and Planileberis cf. malzi Bischoff (Kharaib) and indet. gen.
IRP6 Grosdidier (Shu’aiba). Both of these species have been previously recorded from the Aptian
of Iran. Further work on these formations may identify other species of stratigraphical importance.
The Nahr Umr Formation in Oman has a presumed Early Albian age. It is characterised by
Schuleridea baidarensis Damotte and Saint-Marc and S . sp. OMN 9. According to Standring
(1972), the Nahr Umr in Oman is divisible into three units using ostracods, but the identity of the
index forms used is not known to the present author, and no such subdivision was recognised from
the available material.
Following BP’s practice, the Natih Formation is divided into seven members. Members ‘g’, ‘f’
and the lower part of ‘e’ are thought to be Albian in age; Members ‘g’ and ‘f’ are characterised by
the first downhole occurrence of Cytherella sp. OMN 1 1 and Schuleridea IRJIS Grosdidier in the
lower part and by Metacytheropteron IRClO Grosidier throughout. Member ‘e’ is characterised by
Metacytheropteron IRClO Grosdidier, Cythereis cf. fahrioni Bischoff and Glenocythere spp. together with a number of rarer species. Member ‘d’ typically contains the first downhole occurrences of
Eocytheropteron retroversicardinatum Al-Abdul-Razzaq, Cytherella gigantosulcata Rosenfeld and
“Louza amygdaloidea” Al-Abdul-Razzaq each of which has a well documented Early Cenomanian to Albian age throughout the Middle East. Member ‘c’ and the lower part of the combined ‘a+b’ member are considered to be of Late Cenomanian age and are characterised by a large
number of species in Oman which have been previously recorded from the Middle East and, in
some cases, from N. Africa as well. They include V. jezzineensis (Bischoff), Veeniacythereis cf.
maghrebensis (Bassoullet and Damotte) V. streblolophata Al-Abdul-Razzaq and Grosdidier, Peleriops ulosa Al-Abdul-Razzaq, P. elassiodictyota Al-Abdul-Razzaq, Cythereis algeriana Bassoullet
and Damotte, Metacytheropteron berbericus Bassoullet and Damotte, Cytherella khalidrazzaqi
Al-Abdul-Razzaq, C. ahmadiensis Al-Abdul-Razzaq and C. kuwaitensis Al-Abdul-Razzaq. The
upper part of the combined ‘a+b’ member contains Brachycythere cf. sapucariensis and B. cf.
IRE10 Grosdidier in some wells. These are the only index species from the presumed latest Cenomanian to Turonian in Oman.
Few of the species of Coniacian to Early Santonian age from Iran or elsewhere in the Arabian
Gulf area are also known from Oman. This may be considered as evidence for the absence of
sediments of this age from Oman and supports the notion of a regional unconformity between
Turonian and younger Senonian sediments.
The Fiqa Formation in Oman is probably ?Santonian to Campanian in age and is characterised
by a large number of Brachycythere spp. most of which are not attributable to previously described
species. They are accompanied by Soudanella cf. dolabrata Al-Furaih, Pterygocythere sp., “Mehesella” cf. IRC23 Grosdidier and sometimes by Reticytheretta sp. and Cytherella posterosulcata
The Simsima Formation is probably Maastrichtian in age and contains large numbers of reticulate
trachyleberid ostracods including Hornibrookella divergens Al-Furaih and Paragrenocythere gravis
Al-Furaih as well as Holcopocythere sp., Phalcocythere sp. and Phyrocythere dextrodigitata AlFuraih. Many of the species from this formation are known to cross the Cretaceous/Tertiary
S A N CMP M A A P
B r a c h y c y t h e r e sp
Brachycythere s p
- - - -7
Aphrikanecythere phumatoides DarnotteBOertli
N A M E
4 - 14
(OMN I )
2 - 5
B r a c h y c y t h e r e sp
2 - 9,IC
2 - 3
Cytherella posterosulcato Razzaq 1981
-- - --7
nolcopocythere bassiporosa/falsoculata AI-Furaih
1 @@I ?:- ?!?I
Hornibrookella divergens Al-Furaih,
I R C 2 3 Grosdidier, 1 9 7 3
Metacytheropteron I R L 3 Grosdldier, 1 9 7 3
- - - -3
Occullocythereis p r o r a
Paragrenocythere g r a v l s AI-Furalh. 1 9 7 7
I - 21
Phalcocythere rectangularis/hebes AI-Furaih,
Phyrocythere dextrodigitata AI-Furaih, 1980
I - 10
Reticytheretta sp. ( O M N 8 )
Soudanella dolabrata Ai-Furaih, 1984
TEXT-FIG.3-Comparison of stratigraphical ranges of Late Cretaceous ostracods in the Middle East and North
Africa (in alphabetical order).
ALGERIA-1, Bassoullet and Damotte, 1969; 2, Bismuth ef al., 1981; 3, Glintzboeckle and Magne,
1959; 4, Dome et al., 1982. EGYPT-5, Van den Bold, 1964. IRAN-6, Grosdidier, 1973. IRAQ-7,
Al-Sheikly, 1980. ISRAEL-8, Rosenfeld and Raab, 1974; 9, Rosenfeld and Raab, 1984; 10, Hirsch ef al..
1983. LEBANON-11, Bischoff, 1963; 12, Damotte and St. Marc, 1972. KUWAIT-13, Al-Abdul-Razzaq,
1977; 14, Al-Abdul-Razzaq, 1979a; 15, Al-Abdul-Razzaq, 1979b; 16, Al-Abdul-Razzaq, 1980; 17, Al-AbdulRazzaq and Grosdidier, 1981; 18, Al-Abdul-Razzaq, 1981. SAUDI ARABIA/% ARABIAN GLJL.F19, Al-Furaih, 1977; 20, Siddiqui and Al-Furaih, 1980; 21, Al-Furaih, 1980; 22, Sayyab, 1956; 23,
Al-Furaih, 1983. OMAN-24, this paper.
APT ALB CEN TUR
N A M E
Ahmodiura cf. dlctyolo R o z z o q , I 9 7 7
I - I!
Brochycythere ct. sapucariansls Kmmnulbein,
1964(ssnru B i s m u t h e t a l , 1981)
Brachycythere cf. I R E IOGrosd1diar,1973
Cythefei6 algeriano Ba8owllet 8 Damotte,
Cytheralo cf I R K 2 6 Grosdldler
Cytharslla ahmadimsir Rarzaq, 1981
Cytherelia kholidrozzaql Razmq. 1981
Cytherella kuwaitanais Razzaq, h981
Cytherello gigantosulcata Roscnftld, 1981
Cytheralla r p . (OMN II 1
Eocy theropteron relrovarsicardinatum Razzaqt
- ?-- @
Cytherello sp. ( O M N 10)
Glenocythere bahreinensir Razzoq. 1 9 7 9 0
7 - - - - - ? 2
Glsnocythere roticuIota Rozroq, 19790
1 7,&l?m 1 1
4 - I,
"Louza omygdaloided' Rozraq , 1 9 7 7
4a-Cbmparison of stratigraphical ranges of Middle Cretaceous ostracods in the Middle East and North
Africa (in alphabetical order).
ALGERIA-1, Bassoullet and Damotte, 1969; 2, Bismuth er al., 1981; 3, Glintzboeckle and Magne, 1959;
4, Dome et al., 1982. EGYPT-5, Van den Bold, 1964. IRAN-6, Grosdidier, 1973. IRAQ-7, Al-Sheikly,
1980. ISRAEL-8, Rosenfeld and Raab, 1974; 9, Rosenfeld andRaab, 1984; 10, Kirsch et al.. 1983.
LEBANON-11, Bischoff, 1963; 12, Damotte and St. Marc, 1972. KUWAIT-13, AI-Abdul-Razzaq, 1977;
14, Al-Abdul-Razzaq, 1979a; 15, Al-Abdul-Razzaq, 1979b; 16, Al-Abdul-Razzaq, 1980; 17, AI-AbdulRazzaq and Grosdidier, 1981; 18, Al-Abdul-Razzaq, 1981. SAUbI ARABIA/% ARABIAN GULF19, Al-Furaih, 1977; 20, Siddiqui and Al-Furaih, 1980; 21, Al-Furaih, 1980; 22, Sayyab, 1956; 23, AlFuraih, 1983. OMAN-24, this paper.
ICEN ITUR I I
N A M E
Metocytheroptemn I R C lo
Gmdidier, I 9 7 3
Peldops slassiodictyota Razzoa. 1 9 7 9 b
Peldop. uloso Razzaq
Planileberls malzi (Biachoff), 1963
4 - 16
Schuleridea I R J 15 (Grmdidier),1973
Schuleridea r p (OMN9)
Vaenia sp. (OWN 12)
? - - 7 0
o r r h s ~(Bixhoffl.1963
D o m o t t d , I969
Vaeniacythsrels moghrebmsa (Bassoullet 8
Veeniacythereia streblalaphdo Rozmq 0
Grosdidler ( 0 ;8ubtp.schiatq b; wbap. stretio-
Indsl.genua e t . w I R P 6 Grordidier, 1973
TEXT-FIG.4b-Comparison of stratigraphical ranges of Middle Cretaceous ostracods in the Middle East and North
Africa (in alphabetical order).
ALGERIA-1, Bassoullet and Damotte, 1969; 2, Bismuth et al., 1981; 3, Glintzboeckle and Magne,
1959; 4, Dome et a/., 1982. EGYPT-5, Van den Bold, 1964. IRAN-6, Grosdidier, 1973. R
7,AlSheikly, 1980. ISRAEL-8, Rosenfeld and Raab, 1974; 9, Rosenfeld and Raab, 1984; 10, Hirsch, et al.,
1983. LEBANON-1 1, Bischoff, 1963; 12,Damotte and St. Marc, 1972. KUWAIT-13, Al-Abdul-Razzaq,
1977; 14, Al-Abdul-Razzaq, 1979a; 15, Al-Abdul-Razzaq, 1979b; 16, Al-Abdd-Razzaq, 1980; 17, AlAbdul-Rauaq and Grosdidier, 1981; 18, Al-Abdul-Razzaq, 1981. SAUDI ARABIA/S. ARABIAN
GULF-19, Al-Furaih, 1977; 20, Siddiqui and Al-Furaih, 1980; 21, Al-Furaih, 1980; 22, Sayyab, 1956;
23, Al-Furaih, 1983. OMAN-24, this paper.
Biostratigraphy of Cretaceous Ostracods from Oman 1195
boundary in Saudi Arabia, but Occultocythereisprora Al-Furaih and Aphrikanecytherephumato ides
Damotte and Oertli apparently signify the presence of Maastrichtian or older sediments. Another
important marker is “Eobuntonia curta” Sayyab,
A comprehensive study of the palaeogeography of Tethyan Cretaceous ostracods is beyond the
scope of this paper which deals principally with the species represented in Oman. Nevertheless, the
data presented herein are sufficient to allow some speculation on the palaeogeographical distribution of these faunas. The following remarks are tentative since the extent to which the known occurrences reflect the actual distributions is uncertain. This is due mainly to incomplete research in
As a result of a gradual marine transgressive trend throughout the Aptian to Cenomanian (see
Text-fig. l), a broad carbonate platform developed along the southern shore of Tethys (SaintMarc, 1978). In the Aptian and Early Albian there was some similarity between the ostracod faunas
of Oman, Iran and, to a lesser extent, between Oman, Lebanon and Iraq (see Text-fig. 3).
During Late Albian to Cenomanian times, very similar assemblages of ostracods characterise
a vast palaeogeographical province comprising Algeria, Tunisia, Libya, Egypt, Israel, Lebanon,
Iraq, the Arabian Gulf, Iran, Oman, Somalia and N. Ethiopia. This area is coincident with the
known extent of the southern shelf of Tethys at that time (see Text-fig. 1). A notable exception is the
distribution of the genus Glenocythere which is characteristic of the Arabian Gulf Coast area, but
which is absent from N. Africa and the Levant. The fauna as a whole differs from those known
from France, Spain and Syria to the north, Morocco and Senegal to the west and Tanzania to the
So few ostracods are known from the latest Cenomanian to Turonian of this area that the full
extent of their distributions is largely unknown. This is probably largely due to epiorogenic movements during the Turonian and early Senonian which resulted in widespread nondeposition or
erosion of Turonian sediments. However, Brachycythere sapucariensis and similar forms are known
from Brazil, W. Africa, N. Africa and the Middle East at this time, a fact which has been used to
support the idea of a trans-Saharan marine passage during the Turonian.
In Oman, the study area appears to have been emergent during early Senonian times, as evidence
for Conacian to Santonian sediments is missing.
The great similarity between the faunas of the coastal Fars region of Iran and Oman seen
during the Late Albian to Cenomanian is lost by the ?Santonian/Campanian, presumably as a
result of basinal facies developing throughout the region of the Arabian Gulf and northern Oman
During the Campanian and Maastrichtian, essentially the same faunas are seen in Oman, N.
PLATE1-Fig. 1. Holcopocythere bassiporosa/falsoculata Al-Furaih. Simsima Fm. Fig. 2. Phalcocythere rectangularislhebes Al-Furaih. Simsima Fm. Figs. 3,4. “Mehesella” cf. M. IRC23 Grosdidier. Fiqa Fm. Fig. 5. Soudanella cf. dolobrata Al-Furaih. Fiqa Fm. Figs. 6, 7. Occultocythereis prora Al-Furaih. Fiqa Fm. Figs. 8, 9.
Metacytheropteron IRClO Grosdidier. Natih ‘f +g’ Fm. Fig. 10. Phyrocythere dextrodigitata Al-Furaih. Simsima Fm. Fig. 11. Eocytheropteron retroversicardinatum Al-Abdul-Razzaq. Natih ‘d‘ Fm. Figs. 12, 13.
Metacytheropteron berbericus (Bassoullet and Damotte). Natih ‘d’ Fm. Figs. 14, 15. Buntonia cf. IRE9
Grosdidier. Fiqa Fm. Fig. 16. Schuleridea sp. [OMN9]. Shu’aiba Fm. Fig. 17. “Eobuntonia curta Sayyab”.
Fiqa Fm. Fig. 18. Eobuntonia cf “E. curta Sayyab”. Fiqa Fm. Fig. 19. Ahmadiura cf “A. dictyota Al-AbdulRazzaq”. Natih ‘e’ Fm. Fig. 20. ?Reticytheretta sp. [OMNS]. Natih ‘a+b’ Fm. Fig. 21. Metacytheropteron
IRW Grosdidier. Fiqa Fm. Fig. 22. Schuleridea baidarensis (Damotte and St. Marc.) Nahr Umr Fm.
Fig. 23. Schuleridea IRJ15 (Grosdidier). Natih ‘e’ Fm. (scale bar = 500 pm). Fm.=Formation.
Biostratigraphy of Cretaceous Ostracods from Oman 1197
Ethiopia, Somalia and Saudi Arabia. No extensive survey of the literature outside these areas was
made, but it would appear that the ostracod faunas of this region are significantly different from
those of the rest of the Middle East and N. Africa at this time (see Text-fig. 4), although there are
apparently some species which are found in TunisiaIAlgeria and Oman (e.g. A. phumatoides and
? ‘Eobuntonia curta’). This marked endemism may result from the irregular submarine topography
which developed on the shelf as a result of tectonism and differential subsidence during Turonian
and early Senonian times, and which may have isolated various parts of the shelf and the associated
Variations in the distribution patterns of ostracods throughout this time may also be related to
changes in oceanic circulation in Tethys or to changes in climate due to the northward drift of the
Arabian plate (see Text-fig. 1).
ON SELECTED INDEXSPECIES
The stratigraphical ranges of index taxa in Oman are shown in Text-fig. 2; distributions and ranges of these taxa for all areas are tabulated in Text-figs. 3 and 4. The following remarks provide
additional data which affect the overall knowledge of stratigraphical and geographical distributions
of these species.
Aphrikanecythere phumatoides Damotte and Oertli, 1982 (Pl. 4, fig. 14): First illustrated by
Sayyab (1956) as “Anchycythereis quadrata” from the Upper Cretaceous of the Gulf Coast of Saudi
Arabia and Qatar. Similar to Peleriops levisulcata of Al-Sheikly (1980) and P . nodosa Al-Furaih
(1984a) from the Maastrichtian of Iraq and Saudi Arabia, respectively. Comparable specimens
occur in the Sadi Formation and the Tanuma Formation in Iraq of ?Campanian and ?Coniacian
Cytherella posterosukata Al-Abdul-Razzaq (198 1) (Pl. 5, figs. 1, 2): Described by Al-AbdulRazzaq (1977; 1981) from the Santonian Gudair Formation of Kuwait. Also present in Somalia/
Ethiopia, Iran and Iraq where it has a Santonian to Coniacian age range (unpublished data).
“?Eobuntonia curta” Sayyab, 1956 (Pl. 1, figs. 17, 18): Probably identical with Buntonia B816
of Bellion, Donze and Guiraud (1973) from the Campanian of Algeria. Described by Sayyab (1956)
from the Late Cretaceous of the S. Arabian Gulf coast area; occurs in the Campanian Sadi Formation and the ?Coniacian Tanuma Formation, Iraq and the Santonian-Coniacian of Ethiopia
Holcopocythere bassiporosalfalsoculata Al-Furaih, 1980 (Pl. 1, fig. 1) : Resembles both H.
bassiporosa Al-Furaih (1980) and H. falsoculata Al-Furaih (1980) from the Late Maastrichtian and
Early Palaeocene of Saudi Arabia.
YMehesella’ cf. ‘Mehesella’ IRC23 Grosdidier, 1973 (Pl. 1, figs. 3, 4): Unpublished data indicate its presence in Somalia and Ethiopia and a stratigraphical range of Santonian to Coniacian.
Occultocythereis prora Al-Furaih, 1984a (Pl. 1, figs. 6, 7): It is similar but not identical to
PLATE 2-Figs. 1, 2. Brachycythere sp. [OMN2]. Fiqa Fm. Fig. 3. Bruchycythere sp. [OMN4]. Fiqa Fm. Fig. 4.
Bruchycythere sp. [OMNS]. Fiqa Fm. Fig. 5. Brachycythere sp. [OMNl]. Simsima Fm. Fig. 6. Bruchycythere
cf. B. IRE10 Grosdidier. Natih ‘a+b’ Fm. Figs. 7, 8. Bruchycythere cf. sapucurier$s Krommelbein (sensu
Bismuth et ul.) Natih ‘a+b’ Fm. Figs. 9, 10. Brachykythere sp. [OMN3]. Fiqa Fm. Figs. 11, 12. Pterygocythere
sp. [OMN 71. Fiqa Fm. (scale bar = 500 pm). Fm. =Formation.