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The permian sequence reconstructed from reworked carbonate clasts in the Batain Plain (northeastern Oman)
C. R. Acad. Sci. Paris, Sciences 0 2000 Acadbmie des sciences S1251805000001336/FLA Stratigraphy Geomaterials
deja Terre et des plan&es / Earth and Planetan/ Sciences 330 (2000) / Editions scientifiques et medicales Elsevier SAS. Tous droits r&en&
273-279
/ Stratigraphie / GComatCriaux
The Permian sequence reconstructed from reworked carbonate clasts in the Batain Plain (northeastern Oman) Marc Hausef,
Daniel Vachard b* , Rossana Martini’,
a Geologisch-Mineralogisches
Institut,
Universittit
Bern,
Albert Mattef,
Baltzerstrasse
1, CH-3012
Tjerk Petersa, Louisette Bern,
Zaninetti’
Switzerland
b UFR des sciences de la Terre, Upresa 8014 du CNRS, universitC des sciences et technologies
de Lille, 59655 Villeneuve-d’Ascq
cedex,
France
’ DCpartement de gCologie et pal6ontologie, Received 11 October Communicated
universite de Cen&e,
13, rue
des Maraichers, 1211 Cenhve, Switzerland
1999; accepted 3 January 2000
by jean Dercourt
Abstract - An almost complete Permian sequence is reworked in the conglomerates and sandstones of the Aseelah Unit forming the lower part of the Batain Group. This series of Late Permian to Earliest Triassic age overlies conformably the Qarari Unit, dated as Middle Permian by ammonoids. The bioclastic limestone pebbles and boulders deposited on shallow marine-shelf environments yield diversified assemblages of dasyclads, red algae, fusulinids and smaller foraminifers, indicating Yakhtashian, Bolorian, Kubergandian, Early Murgabian, Midian and Dzhulfian ages (systematic work in progress). 0 2000 Academic des sciences / Editions scientifiques et medicales Elsevier SAS Permian
/ Batain
Plain / Oman
/ biostratigraphy
/ fusulinids
/ palaeogeography
R&um6 - La sikie permienne de h phine de Batain, Oman, reconstitui?e d’aprks des lithoclastes. L’unit6 d’A.seelah, d’sge Permien superieur 5 Trias inf&ieur, est situCe dans la partie infirieure du Groupe de Batain (Oman) et recouvre en concordance l’unitk de Qarari, datee du Permien moyen par des Ammondides. Elle se compose de gr&s et de conglom&ats, dont les galets calcaires, provenant de d&p&s de plates-formes marines peu profondes, livrent de nombreuses algues, de petits Foraminiferes et des Fusulines de plusieurs &ages du Permien : Yakhtashien, Bolorien, Kubergandien, Murgabien infkrieur, Midien, et Djoulfien. Les principaux marqueurs stratigraphiques sont illustr6s. 0 2000 Acad6mie des sciences / Editions scientiliques et mkdicales Elsevier SAS
Version
d’Huqf-Haushi, ticuli&ement phique.
abregtte
Dans la plaine de Batain, au nord-est du sultanat d’Oman yigure I>, les conglom6rat.s de l’uniti: d’Aseelah (Permien sup&ieur 2 Trias infgrieur) contiennent des galets de calcaires permiens riches en microfaunes et microflores carbonatkes, dont 1’6tude systkmatique est en tours. Le Permien fossilif&e avait deja 6t6 identifi6 dans plusieurs secteurs du sultanat: peninsule de Musandam, montagnes centrales &Oman et region
* Correspondence
and reprints:
Daniel.Vachard@univ-lillel
mais les nouvelles associations sont parimportantes sur le plan paKobiog6ogra-
La plaine de Batain, actuellement couverte de sables et de graviers, possede un substratum compose de nappes P mat&iel s’Ctageant du Permien au C&a& sup& rieur. Ces nappes sont cachetees par des d&pats autochtones, du Paleoc&ne au Miocene. La nomenclature lithostratigraphique de la plaine de Batain a fait l’objet d’ajustements successifs, depuis le
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travail princeps de Glennie et al. Bl, la cartographic des Cquipes du BRGM au debut des annees 90 et jusqu’a la notice recente de Peters et al. 1151, 013 fut introduit le nom d’unite d’Aseelah. Celle-ci mesure une trentaine de metres d’epaisseur, et comporte des chenaux remplis d’une matrice sableuse et de galets calcaires centimetriques a metriques. L’etude des microfacies prouve que les formations remaniees s’echelonnent du Yakhtashien au Djoulfien (echelle de Leven [141). Les niveaux de la partie superieure du Permien infirieur (Yakhtashien-Bolorien) montrent des Fusulines surtout connues au Japon; le Kubergandien livre des microfaunes et microflores algaires nouvelles; le Murga-
bien et le Midien sent typiquement tethysiens et apparent& aux regions classiques de 1’Asie du Sud-Est; le Djoulfien possede des a&it& biogeographiques avec la Chine du Sud. Trois conclusions s’imposent : (1) le Permien de la plaine de Batain, depuis le Yakhtashien, se depose sur ou en bordure dune plate-forme carbonatee tropicale ; (2) il se distingue sensiblement, par ses associations microfaunistiques, du Permien des Montagnes d’Oman, d’une part, et de celui d’Huqf-Haushi, d’autre part ; (3) le peuplement ressemble souvent plus a celui de 1’Asie du Sud-Est (Chine, Japon, Cambodge) qu’a celui de regions moins lointaines (Turquie, Iran, Pamir).
1. Introduction
west from interior Oman. Recent sand and gravel deposits cover an extensive part of the area. The Batain Plain comprises the Batain nappes, which are composed of Permian to Late Cretaceous marine sediments, as well as volcanic rocks [4, 17, 221 and the eastern Ophiolite nappes [I 51. Tectonically the Batain Plain is characterized by intense NNE-SSW-trending folds and faults indicating a WNW directed nappe transport [19]. The nappes are unconformably overlain by neo-autochthonous Late Palaeocene to Miocene continental siliciclastic and shallow marine limestones. The Aseelah Unit is often associated with the Qarari Unit (figure2), dated as Middle Permian (Wordian or Murgabian/Midian), based on an ammonoid assemblage [ll].
In the course of a research project in the Batain Plain (NE Oman), conglomerates and sandstones with Permian microfaunas were discovered; these deposits belong to the Aseelah Unit [15] of Late Permian to Earliest Triassic age, i.e., indicative of the end of the major transgressive-regressive cycle at the Permianfiriassicboundary [9, lo]. In Oman, Permian outcrops are well exposed in the Musandam Peninsula, in the Central Mountains and in the Huqf-Haushi area (e.g., [131). For the Batain Plain, Shackleton et al. [21] mentioned the occurrence of Permian fossiliferous grits and limestone breccias with Permian fusulinid boulders, about 2 km NNW of Jabal Qarari (figure 7). In the Huqf area, the Guadalupian Khuff Formation is unconformably overlain by continental sandstones and siltstones of the Minjur Formation (2, 7, 181, which could be at the same time as the Aseelah Unit in the Batain Plain. This preliminary paper presents mainly a biostratigraphic analysis (by foraminifers and algae) of the carbonate pebbles found in the conglomerates. Their microfacies indicate shallow marine-shelf palaeoenvironments during almost the whole Permian along the Oman margin. Conspicuous and astonishing for this fauna is the resemblance with occurrences known from several formations of South China and the Akiyoshi group in Japan, contrarily to the Oman mountains or the Huqf-Haushi area [l, 2, 61. The systematic descriptions of the microfauna and microflora will be published as separate papers.
2. Geological
setting
The conglomerates of the Aseelah Unit are situated in the Batain area in eastern Oman to the south of the town Sur (figure 7). The Batain Plain extends about 130 km northeast-southwest and 40 km in the east-west direction. It is delimited to the northeast by the Arabian Sea. The Wahibah Sands separate the Batain Plain in the
274
3. Previous
work
Geological survey in Oman began in the early 1960s by the Petroleum Development Oman (PDO), and the classic study of the Oman Mountains by Glennie et al. [81 became the basis for subsequent research. These authors interpreted the Batain sediments as part of the Hawasina allochthonous units. Centimetre to several IOO-m-sized blocks and boulders of reworked Permian and Triassic limestones, which display an ‘Oman Exotic’ facies, have been previously considered as the lbra and the Al Aridh Formations [8] were included in the Batain M&nge 1211. The sandy Permian conglomerates found in the Batain area were attributed to the ‘fossiliferous grits’ by these authors. Geologists from the Bureau de recherches ge’ologiques et mini&es (BRGM) introduced a new lithostratigraphic nomenclature for Oman and the Batain Plain [4, 5, 17, 221. They assigned the Permian conglomerates and boulders to the Al Jil Formation, which was defined by Bechennec [3] and later redefined by Bechennec et al. [5], in the Oman Mountains. Pillevuit et al. [16] were the first to subdivide the Oman Exotics by their depositional time and to present a revised classification with different palaeogeographic
M. Hauser et al. / C. R. Acad. Sci. Paris, Scier ices de la Terre et des planbtes / Earth and Planetary Sciences 330 (2000) 273-279
al Hadd
AdDaft&
Ru’ays
Aseelah
Simplified topographic map of the Batain Plain showing the locations of the sampled Permian pebbles in the conglomerates of the Aseelah Unit. Figure 1. Carte topographique simplifiee de la plaine de Batain, montrant I’emplacement des &hantillonnages de galets permiens dans les cong1omCrat.sde I’unite d’Aseelah. Figure
1.
Om
units. They connected the reworked Permian rocks from the Batain Plain to the ‘reworked Permian platform limestones’ in the Hawasina basin. We support this new concept, but following our field observations and biostratigraphic data, we attribute the Batain nappes to the Batain Group and no longer to the Hawasina Complex [I 21. Based on the different lithostratigraphic and biostratigraphic results, it was necessary to replace the Al Jil Formation in the Batain Plain by the newly defined Qarari Unit, the Aseelah Unit and the Ad Daffah Unit [151.
4. Lithostratigraphy
of the Aseelah
Unit
The Aseelah Unit can be subdivided from the base to the top in two members. The lower member is made up of sandy conglomerates, which consist of exclusively reworked shallow marine Permian limestone boulders.
J
The quartz amount of the matrix increases up-section, and the conglomerates grade into a whitish coarsegrained sandstone with a calcareous matrix of the upper member. The Permian shallow-marine fauna was found at several outcrops throughout the Batain Plain; continuous sections are exposed at 6 km northwest of Bu Fashiqah and at 3 km southwest of Aseelah (figure 1). At the locality northwest of Bu Fashiqah, the sequence is overturned (figure 2). The Aseelah Unit rests upon brown-reddish dolomite, which forms the uppermost part of the Qarari Unit. The Qarari limestones show karst phenomena and erosion horizons that are overlain by around 5 m of decimetre-sized bedded dolomite. This brown-reddish dolomite is overlain by a moderate to very poorly sorted, but well-rounded polymict clast-supported carbonate conglomerate. The conglomerate is composed of centimetre up to metresized fossiliferous boulders and recrystallised limestone blocks. The clast-supported conglomerate grades into a sandy matrix-supported conglomerate and into a calcar-
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Gastropods
Limestone
Crinoids
Nodular bedded limestone
Fusulinids
Dolomite
Bivalves
Marly
Ammonoids
shales
Nautiloids
Sandstone
Brachiopods Conglomerate Bryozoa Breccia beds Conglomerate
Ripple beds
Slump
Figure 2. Scheme showing the overturned lithological section and an overview of the Bu Fashiqah outcrop at locality (UTM coord. 7757691246896). Figure 2. Schdma la skrie renversee et rama de I’affleurement Fashiqah dans la om -
eous
sandstone
Unit
measures
approximately
(figure
2). At this locality, 25 m, and southwest 35 m. There, the Aseelah circa
the Aseelah of Aseelah, Unit is com-
posed of 5-IO-m-thick bedded channels of calcareous conglomerate with a sandy matrix. The conglomerate passes over in a IO-m-thick succession of cross-bedded white sandstone. This sandstone, the same as that forming the conglomerate matrix, with an exposed thickness of 20 m, is very coarse grained, well sorted and subangular horizons ing early
to rounded. The sandstone beds show a dark brown hematite-rich duricrust, diagenetic weathering surfaces.
5. Biostratigraphy Permian The chronostratigraphic here is that of Leven
276
in two indicat-
of the reworked
[4]
scale (figure
of the Permian used 3), because it is based
10m
J
on biozones the ‘official’ Permian
de cdordonnkes 246896.
2Qm
of Tethyan fusulinids; scale proposed by
stratigraphy
(see
the
montrant le panode Bu localite
UTM
it slightly differs Subcommission
775769/
from of
[2]).
One sample is homogeneously Yakhtashian in age (H233), another one contains a mixed assemblage of Yakhtashian and Dzhulfian microfossils, probably in a pedogenetic breccia, which formed prior to the definitive reworking into the Aseelah Unit (H253). The Yakhtashian assemblages are represented by a new codiacean alga, some dasyclads Epimastopora sp., and the fusulinids leeina kraffti (figure 4. l), Schubertella cf. simplex and Minojapanella cf. elongata. The
Bolorian
Minojapanella ‘Parafusulina’
ex
sample HI9 shows cf. elongata, M. gr. japonica (figure
Neoendothyra cf. parva 4.2).
sp., and
Four bioclastic rudstones (HI 80, H236, H240, H241), which however lack the Cancellina marker, may belong to the Kubergandian. Assemblages are rich in algae with
M. Hauser
et al. / C. R. Acad.
(= Late Permian)
Sci.
Paris,
DMULFIAN
Sciences
HZ45
de
H253,
la Terre
et des
I
KUBERGANDIAN
H256
H180;
H236;
CISURALIAN
H240;
HI9
YAKHTASHIAN
H233;
H253
BAKMARIAN
(= Early Perrnian)
ASSELIAN
Figure [141),
Sciences
330
(2000)
273-279
3. Adopted
Permian
corresponding
3. Chronostratigraphie avec les numeros
chronostratigraphy sample numbers. du d’echantillons
consequences
I
L
and
Planetary
6. Palaeogeographic
H241
I
BOLORIAN
1141)
and
Permian)
I
Figure
/ Earth
Gallowayinella ( ?) sp., ‘Pseudofusulina’ (s.1.) sp. and a new Pseudodunbarula ( ?) (figure 4.8). Three levels belong to the Late Permian (Lopingian) and probably to the Dzhulfian: a recrystallised wackestone (H245) with Robuloides cf. gibbus (figure 4.70), and two packstones (H253 see above, and H256) with Hemigordius [Midiella) irregulariformis (figure 4.72), H. ( I) ex gr. spectabilis, Robustopachyphloia annectena (figure 4.17), ‘Glomospira’ cf. guangxiensis, Codonofusiella schubertellinoides (figure 4.9), and Ognibella ( ?) sP.
GUADALUPIAN , (= Middle
plan&es
(according
Permien adoptee correspondants.
(d’apres
to Leven Leven
numerous morphotypes of Tubiphytes obscurus, dasyclads of the genera Anthracoporella, Epimastopora, Diplopora and Kochanskyella, and a new genus of the family Archaeolithophyllaceae (red algae). Foraminifers are represented by several species of Skinnerella (figure 3), Neoendothyra ex gr. parva, Endoteba ex gr. controversa (figure 4), Toriyamaia ex gr. laxiseptata, Nodosaria spp., and Agathammina sp. The sample H249 yields the index fossil of the Early Murgabian: Neoschwagerina simplex (figure 4.5). The Early Midian bioclastic floatstones (H132, H133, H489, H541) are rich in characteristic algae and pseudo-algae, especially Sphaerionia sikuoides and a new species of this genus, and in various foraminifers: Neoendothyra reicheli, Linendothyra dnopha, Postendothyra novizkiana, Reichelina cribroseptata (figure 4.7), Neoschwagerina haydeni, N. minoensis, N. occidentalis, N. margaritae, Colania douvillei (figure 4.6), and representatives of the genera Globivalvulina, Abadehella, Dagmarita, Septaglobivalvulina, Lasiodiscus, Lasiotrochus, Hemigordius, Neodiscus, Hemigordiopsis, Kamurana ( ?), Streblospira ( ?), Multidiscus, Pachyphloia, Nankinella, Staffella, Sphaerulina, Yangchienia, Dunbarula, Rauserella, Ognibella ( ?), Chusenella, Orientoschwagerina, Kahlerina, Pseudokahlerina, Verbeekina, Toriyamaia ( ?I and Codonofusiella. The only Late Midian sample is an algal boundstone (H250) with Anthracoporella, Archaeolithophyllum, Archaeolithoporella, other algae and some foraminifers: Pseudovermiporella elliotti, Pseudovidalina involuta,
The shallow marine boulders and their microfossil assemblages are evidence for an extensive tropical shallow carbonate shelf located during the Permian off the Batain Plain. The underlying Middle Permian Qarari limestone is the hemipelagic basin sediment, deposited laterally on the distal slope of the Arabian carbonate platform. The maximum age of the depositional event (sheddings) is constrained by the Dzhulfian age of the youngest reworked boulders. The Earliest Permian is not present among the pebbles from the Batain Plain, as this part of Oman, as well as the Huqf-Haushi area, were probably covered by cold temperate or cold waters, which did not generate fusulinid-bearing carbonates, similarly to Afghanistan, until the late Sakmarian [14]. A warm temperate or tropical climate during the Yakhtashian permitted the immigration of fusulinids with Leeina kraffti, an eastern species known from Japan, Thailand, Pamir and Iran. The Yakhtashian and Bolorian microfaunas are dominated by species often found in Japan, whereas the Kubergandian is represented by endemic assemblages. The presence of Neoschwagerina simplex suggests the delayed migration of Verbeekinoids into the western Tethys. Primitive forms of this superfamily, like Misellina and Cancellina, are very rare in the central and western Tethys, and widespread in the eastern Tethys, especially in China and Japan. This difference is probably related to the development of a narrow ocean called Permotethys or Neotethys (see the compilation of [6]). Midian microfaunas are comparable with those of the eastern Asian realm (Akiyoshi, Laos, Kampuchea), and apparently richer than the Iranian (Zagros) and Turkish (Taurides) assemblages. The Dzhulfian of the Batain Plain differs from the same Iranian and Turkish associations by the weak diversification of the Nodosariids and Hemigordiopsids, and the absence or great paucity of the genera Rectostipulina, Paraglobivalvulina, Paradagmarita, Louisettita, Neohemigordius, etc. Finally, many species of Palaeofusulinidae, Boultoniidae, Miliolina and Nodosariacea like Robustopachyphloia, from the Batain Plain, can be found in the Lopingian of South China.
277
M. Hauser
et al. / C. R. Acad.
9
and Razgallah, (Ozawa, 1925).
Figure emend. Vachard
Sciences
de
270
et des
1988. Early
(Schellwien Hl9(2).
Kubergandian; Midian; H541(3).
9: Codonofusiela 11: Robustopachyphloia H256(1). Scale
and Dyhrenfurth, 1909). 3: Skinnerella cf. dronovi H241(4). 5: 7: Reichelina
schubertellinoides annecfena bars measure 500
plan&es
/ Earth
and
Planetary
1%
Lin, pm.
Neoschwagerina cribroseptafa
Sheng, 1980.
Yakhtashian; Leven, 1967.
1956. Dzhulfian; Dzhulfian; H256.
330
(2000)
273-279
12
H253(1). 2: ‘Parafusulina’ex Kubergandian; H240(1).
simplex Erk, 1941.
Sciences
Ozawa, 1927. Early Midian; H256(1). 10: 12: Hemigordius
4:
gr. japonica (Gtimbel, 1878) hdoteba ex gr. controversa
emend. Vachard
Early H132(4).
Murgabian; H249(1). 8: Pseudodunbarula
6: Colania douvillei ( ?) sp. Late Midian;
Robuloides (Midiella)
cf. gibbus irregulariformis
1945. Dzhulfian. Zaninetti et al., 1981.
Reichel,
4. 1 : Leeina kraffti (Schellwien et Dyhrenfurth, 1909). Yakhtashien; H253(1). 2 : (( Parafusulina D ex gr. japonica (COmbel, 1878) Toriyama, 1975. Bolorien ; Hl g(2). 3 : Skinnerella cf. dronovi Leven, 1967. Kubergandien ; H240(1). 4 : Endoteba ex gr. confroversa et Razgallah, 1988. Kubergandien ; H241(4). 5 : Neoschwagerina simplex Ozawa, 1927. Murgabien inf&ieur ; H249(1). 6 : Colania
douvillei (Ozawa, 1925). Midien inferieur ; H541(3). ru/a (?) sp. Midien superieur ; H250(3). 9 : Codonofusiela Reichel, 1945. Djoulfien ; H245(2). 11 : Robusfopachyphloia formis
la Terre
IO
Figure 4. 1: Leeina kraffti Toriyama, 1975. Bolorian;
H250(3). H245(2). Dzhulfian;
Sci. Paris,
Zaninetti
et al.,
1981.
Djoulfien
; H256(1).
7 : Reichelina cribrosepfata Erk, 1941. Midien schuberfellinoides Sheng, 1956. Djoulfien annectena Lin, 1980. Djoulfien ; H256.
Les Cchelles
graphiques
mesurent
500
pm.
inf&ieur ; H132(4). 8 : Pseudodunba; H256(1). 10 : Robuloides cf. gibbus 12 : Hemigordius (Midiella) irregulari-
M. Hauser
et al. / C. R. Acad.
Sci.
Paris,
Sciences
de
la Terre
7. Conclusions In the mosaic of the Perigondwan elements, the Oman Mountains and the Batain Plain could represent a palaeogeographic equivalent of the Central Mountains of Afghanistan, but their fusulinid assemblages show some differences (for example the maximal diversity is Murgabian in Afghanistan and Midian in Oman), and the affinities with South China are greater in the Batain
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Plain. A palaeoclimatic boundary (conventionally 305) probably existed between two Omanese Permian provinces: the Batain Plain and the Huqf-Haushi, as indicated by the rich Verbeekinid fauna in the Midian of the Batain Plain, which is absent from the Huqf-Haushi area 121, where the sea waters were probably warm temperate and not tropical. The Oman Mountains formed a third province, possibly the Shanita province of Altiner (in 1201).
Acknowledgements.
The present paper is a result of a geological mapping and research program (sheets Sur and Al Ashkahrah 1:lOO’OOO) of the Universities of Bern and Geneva supported by the Swiss National Foundation (projects No. 20-43’056.95 T.P. and No. 20-50577.97 L.Z.); and the Director General of Minerals, Mohammed Bin Hussein Bin Kassim, Ministry of Commerce and Industry, Sultanate of Oman, and Dr. Hilal Al Azry, Director of the Geological Survey.
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[121 lmmenhauser A., Schreurs G., Peters T., Matter A., Hauser M., Dumitrica P., Stratigraphy, sedimentology and depositional environment of the Batain Group, Eclogae geologicae Helvetiae 91 (1998) 217-235. (131 Lee C.W.A., A review of platform sedimentation in the Early and Late Permian of Oman, with particular reference to the Oman Mountains, in: Robertson A.H.F., Searle M.P., Ries A.C. (Eds.), The Geology and Tectonics of the Oman Region, Spec. Publ. Geol. Sot. London 49 (1990) 3947. 1141 Leven E.Y., Permian stratigraphy and fusulinida of Afghanistan with their palaeogeographic and palaeotectonics implications, Geological Society of America, Special Paper 316, 1997, pp. l-1 34. 1151 Peters T., Hauser M., Moser L., lmmenhauser A., Bl;isi H.R., Bataschi M., Raijh A.S., Geological map of Sur and Al Ashkahrah sheet NF 40-8F and 40-l 2C, scale 1:lOO 000 with explanatory notes, Directorate General of Minerals, Oman Ministry of Industry and Commerce, Muscat (in press). I161 Pillevuit A., Marcoux J., Stampfli G., Baud ics: a key to the understanding of the Neotethyan tion, Geodin. Acta 10 (5) (1997) 209-238.
A., The Oman Exotgeodynamic evolu-
[17] Roger J., Bechennec F., Janjou D., Le Metour rier M., Geological map of Ja’alan sheet NF 40.8E, with explanatory notes, Directorate General, Oman leum and Minerals, Muscat, 1991.
J., Wyns R., Beurscale 1 :lOO 000 Ministry of Petro-
[18] Roger J., Plate1 J.P., Dubreuilh J., Wyns R., Geological map of Mafraq Sheet NF 40-l 1, scale 1:250 000 with explanatory notes, Directorate General of Minerals, Oman Ministry of Petroleum and Minerals, Muscat, 1992. [19] Batain Tertiary
Schreurs G., lmmenhauser A., WNW-directed abduction of the Group on the E-Oman continental margin at the Cretaceousboundary, Tectonics 18 (1) (1999) 148-l 60.
[20] SengGr A.M.C., Altiner D., Cin A., Ustaiismer T., Hsii K., Origin and assembly of the Tethyside erogenic collage at the expense of Gondwana Land, in: Audley-Charles M.G., Hallam A. (Eds.), Gondwana and Tethys, Spec. Publ. Geol. Sot. London 37 (1988) 119-l 81. [21] Shackleton R.M., Ries A.C., Bird A.C., Filbrandt J.B., Lee C.W., Cunningham G.C., The Batain Melange of NE Oman, in: Robertson A.H.F., Searle M.P., Ries A.C. (Eds.), The Geology and Tectonics of the Oman Region, Spec. Publ. Geol. Sot. London 49 (1990) 673-696. [221 Wyns R., Bechennec F., Le M&our J., Roger I., Chevrel S., Geological map of Sur sheet NF-40-08, scale 1:250 000 with explanatory notes, Directorate General of Minerals, Oman Ministry of Petroleum and Minerals, Muscat, 1992.
279
deja Terre et des plan&es / Earth and Planetan/ Sciences 330 (2000) / Editions scientifiques et medicales Elsevier SAS. Tous droits r&en&
273-279
/ Stratigraphie / GComatCriaux
The Permian sequence reconstructed from reworked carbonate clasts in the Batain Plain (northeastern Oman) Marc Hausef,
Daniel Vachard b* , Rossana Martini’,
a Geologisch-Mineralogisches
Institut,
Universittit
Bern,
Albert Mattef,
Baltzerstrasse
1, CH-3012
Tjerk Petersa, Louisette Bern,
Zaninetti’
Switzerland
b UFR des sciences de la Terre, Upresa 8014 du CNRS, universitC des sciences et technologies
de Lille, 59655 Villeneuve-d’Ascq
cedex,
France
’ DCpartement de gCologie et pal6ontologie, Received 11 October Communicated
universite de Cen&e,
13, rue
des Maraichers, 1211 Cenhve, Switzerland
1999; accepted 3 January 2000
by jean Dercourt
Abstract - An almost complete Permian sequence is reworked in the conglomerates and sandstones of the Aseelah Unit forming the lower part of the Batain Group. This series of Late Permian to Earliest Triassic age overlies conformably the Qarari Unit, dated as Middle Permian by ammonoids. The bioclastic limestone pebbles and boulders deposited on shallow marine-shelf environments yield diversified assemblages of dasyclads, red algae, fusulinids and smaller foraminifers, indicating Yakhtashian, Bolorian, Kubergandian, Early Murgabian, Midian and Dzhulfian ages (systematic work in progress). 0 2000 Academic des sciences / Editions scientifiques et medicales Elsevier SAS Permian
/ Batain
Plain / Oman
/ biostratigraphy
/ fusulinids
/ palaeogeography
R&um6 - La sikie permienne de h phine de Batain, Oman, reconstitui?e d’aprks des lithoclastes. L’unit6 d’A.seelah, d’sge Permien superieur 5 Trias inf&ieur, est situCe dans la partie infirieure du Groupe de Batain (Oman) et recouvre en concordance l’unitk de Qarari, datee du Permien moyen par des Ammondides. Elle se compose de gr&s et de conglom&ats, dont les galets calcaires, provenant de d&p&s de plates-formes marines peu profondes, livrent de nombreuses algues, de petits Foraminiferes et des Fusulines de plusieurs &ages du Permien : Yakhtashien, Bolorien, Kubergandien, Murgabien infkrieur, Midien, et Djoulfien. Les principaux marqueurs stratigraphiques sont illustr6s. 0 2000 Acad6mie des sciences / Editions scientiliques et mkdicales Elsevier SAS
Version
d’Huqf-Haushi, ticuli&ement phique.
abregtte
Dans la plaine de Batain, au nord-est du sultanat d’Oman yigure I>, les conglom6rat.s de l’uniti: d’Aseelah (Permien sup&ieur 2 Trias infgrieur) contiennent des galets de calcaires permiens riches en microfaunes et microflores carbonatkes, dont 1’6tude systkmatique est en tours. Le Permien fossilif&e avait deja 6t6 identifi6 dans plusieurs secteurs du sultanat: peninsule de Musandam, montagnes centrales &Oman et region
* Correspondence
and reprints:
Daniel.Vachard@univ-lillel
mais les nouvelles associations sont parimportantes sur le plan paKobiog6ogra-
La plaine de Batain, actuellement couverte de sables et de graviers, possede un substratum compose de nappes P mat&iel s’Ctageant du Permien au C&a& sup& rieur. Ces nappes sont cachetees par des d&pats autochtones, du Paleoc&ne au Miocene. La nomenclature lithostratigraphique de la plaine de Batain a fait l’objet d’ajustements successifs, depuis le
.fr
273
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et al. / C. R. Acad.
Sci. Paris, Sciences
de la Terre et des plan&tes
/ Earth
and
Planetary
Sciences
330 (2000)
273-279
travail princeps de Glennie et al. Bl, la cartographic des Cquipes du BRGM au debut des annees 90 et jusqu’a la notice recente de Peters et al. 1151, 013 fut introduit le nom d’unite d’Aseelah. Celle-ci mesure une trentaine de metres d’epaisseur, et comporte des chenaux remplis d’une matrice sableuse et de galets calcaires centimetriques a metriques. L’etude des microfacies prouve que les formations remaniees s’echelonnent du Yakhtashien au Djoulfien (echelle de Leven [141). Les niveaux de la partie superieure du Permien infirieur (Yakhtashien-Bolorien) montrent des Fusulines surtout connues au Japon; le Kubergandien livre des microfaunes et microflores algaires nouvelles; le Murga-
bien et le Midien sent typiquement tethysiens et apparent& aux regions classiques de 1’Asie du Sud-Est; le Djoulfien possede des a&it& biogeographiques avec la Chine du Sud. Trois conclusions s’imposent : (1) le Permien de la plaine de Batain, depuis le Yakhtashien, se depose sur ou en bordure dune plate-forme carbonatee tropicale ; (2) il se distingue sensiblement, par ses associations microfaunistiques, du Permien des Montagnes d’Oman, d’une part, et de celui d’Huqf-Haushi, d’autre part ; (3) le peuplement ressemble souvent plus a celui de 1’Asie du Sud-Est (Chine, Japon, Cambodge) qu’a celui de regions moins lointaines (Turquie, Iran, Pamir).
1. Introduction
west from interior Oman. Recent sand and gravel deposits cover an extensive part of the area. The Batain Plain comprises the Batain nappes, which are composed of Permian to Late Cretaceous marine sediments, as well as volcanic rocks [4, 17, 221 and the eastern Ophiolite nappes [I 51. Tectonically the Batain Plain is characterized by intense NNE-SSW-trending folds and faults indicating a WNW directed nappe transport [19]. The nappes are unconformably overlain by neo-autochthonous Late Palaeocene to Miocene continental siliciclastic and shallow marine limestones. The Aseelah Unit is often associated with the Qarari Unit (figure2), dated as Middle Permian (Wordian or Murgabian/Midian), based on an ammonoid assemblage [ll].
In the course of a research project in the Batain Plain (NE Oman), conglomerates and sandstones with Permian microfaunas were discovered; these deposits belong to the Aseelah Unit [15] of Late Permian to Earliest Triassic age, i.e., indicative of the end of the major transgressive-regressive cycle at the Permianfiriassicboundary [9, lo]. In Oman, Permian outcrops are well exposed in the Musandam Peninsula, in the Central Mountains and in the Huqf-Haushi area (e.g., [131). For the Batain Plain, Shackleton et al. [21] mentioned the occurrence of Permian fossiliferous grits and limestone breccias with Permian fusulinid boulders, about 2 km NNW of Jabal Qarari (figure 7). In the Huqf area, the Guadalupian Khuff Formation is unconformably overlain by continental sandstones and siltstones of the Minjur Formation (2, 7, 181, which could be at the same time as the Aseelah Unit in the Batain Plain. This preliminary paper presents mainly a biostratigraphic analysis (by foraminifers and algae) of the carbonate pebbles found in the conglomerates. Their microfacies indicate shallow marine-shelf palaeoenvironments during almost the whole Permian along the Oman margin. Conspicuous and astonishing for this fauna is the resemblance with occurrences known from several formations of South China and the Akiyoshi group in Japan, contrarily to the Oman mountains or the Huqf-Haushi area [l, 2, 61. The systematic descriptions of the microfauna and microflora will be published as separate papers.
2. Geological
setting
The conglomerates of the Aseelah Unit are situated in the Batain area in eastern Oman to the south of the town Sur (figure 7). The Batain Plain extends about 130 km northeast-southwest and 40 km in the east-west direction. It is delimited to the northeast by the Arabian Sea. The Wahibah Sands separate the Batain Plain in the
274
3. Previous
work
Geological survey in Oman began in the early 1960s by the Petroleum Development Oman (PDO), and the classic study of the Oman Mountains by Glennie et al. [81 became the basis for subsequent research. These authors interpreted the Batain sediments as part of the Hawasina allochthonous units. Centimetre to several IOO-m-sized blocks and boulders of reworked Permian and Triassic limestones, which display an ‘Oman Exotic’ facies, have been previously considered as the lbra and the Al Aridh Formations [8] were included in the Batain M&nge 1211. The sandy Permian conglomerates found in the Batain area were attributed to the ‘fossiliferous grits’ by these authors. Geologists from the Bureau de recherches ge’ologiques et mini&es (BRGM) introduced a new lithostratigraphic nomenclature for Oman and the Batain Plain [4, 5, 17, 221. They assigned the Permian conglomerates and boulders to the Al Jil Formation, which was defined by Bechennec [3] and later redefined by Bechennec et al. [5], in the Oman Mountains. Pillevuit et al. [16] were the first to subdivide the Oman Exotics by their depositional time and to present a revised classification with different palaeogeographic
M. Hauser et al. / C. R. Acad. Sci. Paris, Scier ices de la Terre et des planbtes / Earth and Planetary Sciences 330 (2000) 273-279
al Hadd
AdDaft&
Ru’ays
Aseelah
Simplified topographic map of the Batain Plain showing the locations of the sampled Permian pebbles in the conglomerates of the Aseelah Unit. Figure 1. Carte topographique simplifiee de la plaine de Batain, montrant I’emplacement des &hantillonnages de galets permiens dans les cong1omCrat.sde I’unite d’Aseelah. Figure
1.
Om
units. They connected the reworked Permian rocks from the Batain Plain to the ‘reworked Permian platform limestones’ in the Hawasina basin. We support this new concept, but following our field observations and biostratigraphic data, we attribute the Batain nappes to the Batain Group and no longer to the Hawasina Complex [I 21. Based on the different lithostratigraphic and biostratigraphic results, it was necessary to replace the Al Jil Formation in the Batain Plain by the newly defined Qarari Unit, the Aseelah Unit and the Ad Daffah Unit [151.
4. Lithostratigraphy
of the Aseelah
Unit
The Aseelah Unit can be subdivided from the base to the top in two members. The lower member is made up of sandy conglomerates, which consist of exclusively reworked shallow marine Permian limestone boulders.
J
The quartz amount of the matrix increases up-section, and the conglomerates grade into a whitish coarsegrained sandstone with a calcareous matrix of the upper member. The Permian shallow-marine fauna was found at several outcrops throughout the Batain Plain; continuous sections are exposed at 6 km northwest of Bu Fashiqah and at 3 km southwest of Aseelah (figure 1). At the locality northwest of Bu Fashiqah, the sequence is overturned (figure 2). The Aseelah Unit rests upon brown-reddish dolomite, which forms the uppermost part of the Qarari Unit. The Qarari limestones show karst phenomena and erosion horizons that are overlain by around 5 m of decimetre-sized bedded dolomite. This brown-reddish dolomite is overlain by a moderate to very poorly sorted, but well-rounded polymict clast-supported carbonate conglomerate. The conglomerate is composed of centimetre up to metresized fossiliferous boulders and recrystallised limestone blocks. The clast-supported conglomerate grades into a sandy matrix-supported conglomerate and into a calcar-
275
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et al. / C. R. Acad.
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de
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and
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Gastropods
Limestone
Crinoids
Nodular bedded limestone
Fusulinids
Dolomite
Bivalves
Marly
Ammonoids
shales
Nautiloids
Sandstone
Brachiopods Conglomerate Bryozoa Breccia beds Conglomerate
Ripple beds
Slump
Figure 2. Scheme showing the overturned lithological section and an overview of the Bu Fashiqah outcrop at locality (UTM coord. 7757691246896). Figure 2. Schdma la skrie renversee et rama de I’affleurement Fashiqah dans la om -
eous
sandstone
Unit
measures
approximately
(figure
2). At this locality, 25 m, and southwest 35 m. There, the Aseelah circa
the Aseelah of Aseelah, Unit is com-
posed of 5-IO-m-thick bedded channels of calcareous conglomerate with a sandy matrix. The conglomerate passes over in a IO-m-thick succession of cross-bedded white sandstone. This sandstone, the same as that forming the conglomerate matrix, with an exposed thickness of 20 m, is very coarse grained, well sorted and subangular horizons ing early
to rounded. The sandstone beds show a dark brown hematite-rich duricrust, diagenetic weathering surfaces.
5. Biostratigraphy Permian The chronostratigraphic here is that of Leven
276
in two indicat-
of the reworked
[4]
scale (figure
of the Permian used 3), because it is based
10m
J
on biozones the ‘official’ Permian
de cdordonnkes 246896.
2Qm
of Tethyan fusulinids; scale proposed by
stratigraphy
(see
the
montrant le panode Bu localite
UTM
it slightly differs Subcommission
775769/
from of
[2]).
One sample is homogeneously Yakhtashian in age (H233), another one contains a mixed assemblage of Yakhtashian and Dzhulfian microfossils, probably in a pedogenetic breccia, which formed prior to the definitive reworking into the Aseelah Unit (H253). The Yakhtashian assemblages are represented by a new codiacean alga, some dasyclads Epimastopora sp., and the fusulinids leeina kraffti (figure 4. l), Schubertella cf. simplex and Minojapanella cf. elongata. The
Bolorian
Minojapanella ‘Parafusulina’
ex
sample HI9 shows cf. elongata, M. gr. japonica (figure
Neoendothyra cf. parva 4.2).
sp., and
Four bioclastic rudstones (HI 80, H236, H240, H241), which however lack the Cancellina marker, may belong to the Kubergandian. Assemblages are rich in algae with
M. Hauser
et al. / C. R. Acad.
(= Late Permian)
Sci.
Paris,
DMULFIAN
Sciences
HZ45
de
H253,
la Terre
et des
I
KUBERGANDIAN
H256
H180;
H236;
CISURALIAN
H240;
HI9
YAKHTASHIAN
H233;
H253
BAKMARIAN
(= Early Perrnian)
ASSELIAN
Figure [141),
Sciences
330
(2000)
273-279
3. Adopted
Permian
corresponding
3. Chronostratigraphie avec les numeros
chronostratigraphy sample numbers. du d’echantillons
consequences
I
L
and
Planetary
6. Palaeogeographic
H241
I
BOLORIAN
1141)
and
Permian)
I
Figure
/ Earth
Gallowayinella ( ?) sp., ‘Pseudofusulina’ (s.1.) sp. and a new Pseudodunbarula ( ?) (figure 4.8). Three levels belong to the Late Permian (Lopingian) and probably to the Dzhulfian: a recrystallised wackestone (H245) with Robuloides cf. gibbus (figure 4.70), and two packstones (H253 see above, and H256) with Hemigordius [Midiella) irregulariformis (figure 4.72), H. ( I) ex gr. spectabilis, Robustopachyphloia annectena (figure 4.17), ‘Glomospira’ cf. guangxiensis, Codonofusiella schubertellinoides (figure 4.9), and Ognibella ( ?) sP.
GUADALUPIAN , (= Middle
plan&es
(according
Permien adoptee correspondants.
(d’apres
to Leven Leven
numerous morphotypes of Tubiphytes obscurus, dasyclads of the genera Anthracoporella, Epimastopora, Diplopora and Kochanskyella, and a new genus of the family Archaeolithophyllaceae (red algae). Foraminifers are represented by several species of Skinnerella (figure 3), Neoendothyra ex gr. parva, Endoteba ex gr. controversa (figure 4), Toriyamaia ex gr. laxiseptata, Nodosaria spp., and Agathammina sp. The sample H249 yields the index fossil of the Early Murgabian: Neoschwagerina simplex (figure 4.5). The Early Midian bioclastic floatstones (H132, H133, H489, H541) are rich in characteristic algae and pseudo-algae, especially Sphaerionia sikuoides and a new species of this genus, and in various foraminifers: Neoendothyra reicheli, Linendothyra dnopha, Postendothyra novizkiana, Reichelina cribroseptata (figure 4.7), Neoschwagerina haydeni, N. minoensis, N. occidentalis, N. margaritae, Colania douvillei (figure 4.6), and representatives of the genera Globivalvulina, Abadehella, Dagmarita, Septaglobivalvulina, Lasiodiscus, Lasiotrochus, Hemigordius, Neodiscus, Hemigordiopsis, Kamurana ( ?), Streblospira ( ?), Multidiscus, Pachyphloia, Nankinella, Staffella, Sphaerulina, Yangchienia, Dunbarula, Rauserella, Ognibella ( ?), Chusenella, Orientoschwagerina, Kahlerina, Pseudokahlerina, Verbeekina, Toriyamaia ( ?I and Codonofusiella. The only Late Midian sample is an algal boundstone (H250) with Anthracoporella, Archaeolithophyllum, Archaeolithoporella, other algae and some foraminifers: Pseudovermiporella elliotti, Pseudovidalina involuta,
The shallow marine boulders and their microfossil assemblages are evidence for an extensive tropical shallow carbonate shelf located during the Permian off the Batain Plain. The underlying Middle Permian Qarari limestone is the hemipelagic basin sediment, deposited laterally on the distal slope of the Arabian carbonate platform. The maximum age of the depositional event (sheddings) is constrained by the Dzhulfian age of the youngest reworked boulders. The Earliest Permian is not present among the pebbles from the Batain Plain, as this part of Oman, as well as the Huqf-Haushi area, were probably covered by cold temperate or cold waters, which did not generate fusulinid-bearing carbonates, similarly to Afghanistan, until the late Sakmarian [14]. A warm temperate or tropical climate during the Yakhtashian permitted the immigration of fusulinids with Leeina kraffti, an eastern species known from Japan, Thailand, Pamir and Iran. The Yakhtashian and Bolorian microfaunas are dominated by species often found in Japan, whereas the Kubergandian is represented by endemic assemblages. The presence of Neoschwagerina simplex suggests the delayed migration of Verbeekinoids into the western Tethys. Primitive forms of this superfamily, like Misellina and Cancellina, are very rare in the central and western Tethys, and widespread in the eastern Tethys, especially in China and Japan. This difference is probably related to the development of a narrow ocean called Permotethys or Neotethys (see the compilation of [6]). Midian microfaunas are comparable with those of the eastern Asian realm (Akiyoshi, Laos, Kampuchea), and apparently richer than the Iranian (Zagros) and Turkish (Taurides) assemblages. The Dzhulfian of the Batain Plain differs from the same Iranian and Turkish associations by the weak diversification of the Nodosariids and Hemigordiopsids, and the absence or great paucity of the genera Rectostipulina, Paraglobivalvulina, Paradagmarita, Louisettita, Neohemigordius, etc. Finally, many species of Palaeofusulinidae, Boultoniidae, Miliolina and Nodosariacea like Robustopachyphloia, from the Batain Plain, can be found in the Lopingian of South China.
277
M. Hauser
et al. / C. R. Acad.
9
and Razgallah, (Ozawa, 1925).
Figure emend. Vachard
Sciences
de
270
et des
1988. Early
(Schellwien Hl9(2).
Kubergandian; Midian; H541(3).
9: Codonofusiela 11: Robustopachyphloia H256(1). Scale
and Dyhrenfurth, 1909). 3: Skinnerella cf. dronovi H241(4). 5: 7: Reichelina
schubertellinoides annecfena bars measure 500
plan&es
/ Earth
and
Planetary
1%
Lin, pm.
Neoschwagerina cribroseptafa
Sheng, 1980.
Yakhtashian; Leven, 1967.
1956. Dzhulfian; Dzhulfian; H256.
330
(2000)
273-279
12
H253(1). 2: ‘Parafusulina’ex Kubergandian; H240(1).
simplex Erk, 1941.
Sciences
Ozawa, 1927. Early Midian; H256(1). 10: 12: Hemigordius
4:
gr. japonica (Gtimbel, 1878) hdoteba ex gr. controversa
emend. Vachard
Early H132(4).
Murgabian; H249(1). 8: Pseudodunbarula
6: Colania douvillei ( ?) sp. Late Midian;
Robuloides (Midiella)
cf. gibbus irregulariformis
1945. Dzhulfian. Zaninetti et al., 1981.
Reichel,
4. 1 : Leeina kraffti (Schellwien et Dyhrenfurth, 1909). Yakhtashien; H253(1). 2 : (( Parafusulina D ex gr. japonica (COmbel, 1878) Toriyama, 1975. Bolorien ; Hl g(2). 3 : Skinnerella cf. dronovi Leven, 1967. Kubergandien ; H240(1). 4 : Endoteba ex gr. confroversa et Razgallah, 1988. Kubergandien ; H241(4). 5 : Neoschwagerina simplex Ozawa, 1927. Murgabien inf&ieur ; H249(1). 6 : Colania
douvillei (Ozawa, 1925). Midien inferieur ; H541(3). ru/a (?) sp. Midien superieur ; H250(3). 9 : Codonofusiela Reichel, 1945. Djoulfien ; H245(2). 11 : Robusfopachyphloia formis
la Terre
IO
Figure 4. 1: Leeina kraffti Toriyama, 1975. Bolorian;
H250(3). H245(2). Dzhulfian;
Sci. Paris,
Zaninetti
et al.,
1981.
Djoulfien
; H256(1).
7 : Reichelina cribrosepfata Erk, 1941. Midien schuberfellinoides Sheng, 1956. Djoulfien annectena Lin, 1980. Djoulfien ; H256.
Les Cchelles
graphiques
mesurent
500
pm.
inf&ieur ; H132(4). 8 : Pseudodunba; H256(1). 10 : Robuloides cf. gibbus 12 : Hemigordius (Midiella) irregulari-
M. Hauser
et al. / C. R. Acad.
Sci.
Paris,
Sciences
de
la Terre
7. Conclusions In the mosaic of the Perigondwan elements, the Oman Mountains and the Batain Plain could represent a palaeogeographic equivalent of the Central Mountains of Afghanistan, but their fusulinid assemblages show some differences (for example the maximal diversity is Murgabian in Afghanistan and Midian in Oman), and the affinities with South China are greater in the Batain
et des
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and
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Plain. A palaeoclimatic boundary (conventionally 305) probably existed between two Omanese Permian provinces: the Batain Plain and the Huqf-Haushi, as indicated by the rich Verbeekinid fauna in the Midian of the Batain Plain, which is absent from the Huqf-Haushi area 121, where the sea waters were probably warm temperate and not tropical. The Oman Mountains formed a third province, possibly the Shanita province of Altiner (in 1201).
Acknowledgements.
The present paper is a result of a geological mapping and research program (sheets Sur and Al Ashkahrah 1:lOO’OOO) of the Universities of Bern and Geneva supported by the Swiss National Foundation (projects No. 20-43’056.95 T.P. and No. 20-50577.97 L.Z.); and the Director General of Minerals, Mohammed Bin Hussein Bin Kassim, Ministry of Commerce and Industry, Sultanate of Oman, and Dr. Hilal Al Azry, Director of the Geological Survey.
References 111 Angiolini L., Bucher H., Pillevuit A., Plate1 J.P., Roger J., Broutin J., Baud A., Marcoux J., Al Hashmi H., Early Permian (Sakmarian) brachiopods from southeastern Oman, Geobios 30 (1997) 379405. [21 Angiolini L., Nicora A., Bucher H., Vachard D., Pillevuit A., Al Hashmi H., Marcoux J., Evidence of a Guadalupian age for the Khuff Formation of Southeastern Oman: preliminary report (with palaeontological appendix by A. Nicora), Rivista ltaliana di Paleontologia e Stratigrafia 104 (3) (1998) 329-349. [31 Bechennec F., Geologic des nappes Hawasina orientale et centrale des Montagnes d’Oman, these Paris-6, BRGM, Document 127, 1987, 417 p.
dans d’ctat,
les parties universitk
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