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Northwest Directed Obduction of the Batain Group on the Eastern Oman

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Northwest Directed Obduction of the Batain Group on the Eastern Oman VU Research Portal WNW-directed obduction of the Batain Group on the E-Oman continental margin at the Cretaceous-Tertiary boundary. Schreurs, G.; Immenhauser, A.M. published in Tectonics 1999 DOI (link to publisher) 10.1029/1998TC900020 document version Publisher's PDF, also known as Version of record Link to publication in VU Research Portal citation for published version (APA) Schreurs, G., & Immenhauser, A. M. (1999). WNW-directed obduction of the Batain Group on the E-Oman continental margin at the Cretaceous-Tertiary boundary. Tectonics, 18(1), 148-160. https://doi.org/10.1029/1998TC900020 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. E-mail address: [email protected] Download date: 04. Oct. 2021 TECTONICS, VOL. 18, NO. 1, PAGES 148-160, FEBRUARY 1999 West-northwestdirected obduction of the BatainGroup on the easternOman continentalmargin at the Cretaceous-Tertiaryboundary Guido Schreurs GeologicalInstitute, University of Bern,Bern, Switzerland Adrian Immenhauser Facultyof EarthSciences, Vrije Universiteit,Amsterdam, Netherlands Abstract. The Batain coast area in eastern Oman is dominated 1. Introduction by allochthonousPermian to Late Maastrichtiansedimentary and volcanicrocks (Batain Group), unconformably overlain The Batain coast area is situated in northeasternOman and by neoautochthonousTertiary sediments.The allochthonous coversabout 4000 squarekilometers (Figure 1). It is bounded rocks of the Batain coastwere previouslyattributed to the to the north by the Gulf of Omanand to the eastby the Hawasina complex, the Permian to Coniacian/Santonian ArabianSea. The QuaternaryWahibah Sands separate the sedimentaryinfill of the neo-TethyanHawasina basin off Batain coast area from interior Oman. The area has a low to northernOman. Previous structural interpretations suggested moderaterelief and is dissectedby numerous,roughly E-W thatthe BatainGroup, along with the Hawasinacomplex and trendingwadis. Recentsand and gravel depositscover the Semail ophiolite, was obducted in the Coniacian to extensiveparts of thearea. The Batain Plain is dominatedby Campanian from NE to SW onto the northern Oman allochthonousPermian to Maastrichtiansedimentary and continentalmargin. Results of our work in the Batain area volcanic rocks. These rocks documentthe evolution of a differ from previousinterpretations, with most significant basinoff the easterncoast of Omanand are referredto as the differencesconcerning timing and directionof obduction.Our Batain Group [Immenhauseret al., 1998]. They are results show that WNW directed tectonic movements formed unconformablyoverlain by autochthonousupper Paleocene a fold-and-thrust belt and led to the obduction of to Miocene marine and continentalsediments. The rocks of allochthonousrocks onto the eastOman continental margin theBatain Group were obducted onto the continental margin during latest Maastrichtian/earliest Paleocene times. This is of Oman,parts of whichare exposed near Jabal Ja'alan (Figure coevalwith emplacementof ophioliticfragments along the 1). Here Precambriangneisses, migmatites, and schists were easterncoast of Oman (easternophiolite belt) but is about 15- intrudedby UpperProterozoic plutonic rocks and dykes 20 Myr later than emplacementof Hawasinacomplex and [Rogeret al., 1991;Wiirsten et al., 1991]and covered by Semail ophiolite in northern Oman. Posternplacement neoautochthonousMaastrichtian and Tertiary sediments [Le structuralevolution during the Tertiaryinvolved intraplate Mdtouret al., 1995].On the basisof reflectionseismic data, extension, possibly reflecting the Red Sea/Gulf of Aden welldata, geochemical data, and surface geology, Beauchamp opening,and late Tertiaryshortening related to convergence et al. [1995] suggested a hidden Cretaceous rift basin betweenArabia and Eurasia.Late Tertiary contractional (MasirahGraben) underlying the allochthonous sequence of deformationresulted in refoldingof the Batainnappes and in the Batain coast.The Cretaceousrift-related normal faults are foldingof the overlyingTertiary sediments. A palinspastic believedto havebeen reactivated in the late Tertiary because reconstruction of the Batain area indicates that the Permian to of riftingof theArabian Sea/Gulf of Aden[Beauchamp et al., UpperCretaceous sediments were formerlydeposited in the 1995] Batainbasin, a part of the proto-IndianOcean, along the Previous studiesinterpreted the allochthonousrocks of present-dayeastern Oman margin. This leadsus to propose theBatain Plain as part of theHawasina complex exposed in that Permian breakup of Gondwanaland created both the OmanMountains [Glenhie et al., 1974;Cooper 1990; continentalmargins of Omanand led to the openingof two Shackletonet al., 1990;Roger et al., 1991;Bdchennec et al., major basins:the neo-TethyanHawasina basin in the north 1992;Wyns et al., 1992].The Hawasinacomplex represents andthe proto-IndianOcean Batain basin in the east,the latter thePermian to Coniacian/Santoniansedimentary infill of the separatingArabia from greaterIndia. formerneo-Tethyan Hawasina basin. This paleodepositional realmwas considered to be locatedalong the northernOman marginand bounded to thenorth by a spreadingridge. In the scenarioof the authorscited above, the rocks of the Batain Group along with sediments of the Hawasina basin Copyright1999 by the American Geophysical Union. (Hawasinacomplex) and ophiolites (Semail ophiolites) were thrusttoward the SW and obductedonto the northernOman Papernumber 1998TC900020. continentalmargin during the Coniacianto Campanianat 0278-7407/99/1998TC900020512.00 about 85-80 Ma. 148 SCHREURSAND IMMENHAUSER: OBDUCTION ON EASTERN OMAN MARGIN 149 . .58,:,.? 60? ?:'4..........* '::::........ s Al.:.:!H.'ad•d A1 'Kin Jabat WAHIBA, SANDS • Eastern ! i• OphioliteBelt o• • NappesBatain .• OphioliteSemail • .•.• NappesHawasina ........[--'] Quaternary / /AxisNormal of fault• [• ............ TertiaryCarbonates •. structural -- highs :-¾•CarbonatesCretaceous Thrustfront "=:• Huqf-Haushi Thrust(inferred)fro'nt<• ":5• 'ProterozoicBasement A JabalJa'alan MasirahGraben Sealevel B. Figure 1. (a) Simplifiedgeological map of northeasternOman, (b) Schematicsection across the Batainarea. Locationof sectionis given in Figure la. 150 SCHREURS AND IMMENHAUSER: OBDUCTION ON EASTERN OMAN MARGIN Ophiolites also build Masirah Island, situated over 100 km to the SSEof the Batainarea (Figure 1). The uppermost Formationsdistal proximal(A1v• Group Units Lithology -- Pliocene Jurassic/lowermostCretaceous Masirah ophiolites, however, I!lllllllllllllllll I [ I I I [ I I [ I I Miocene formedearlier than the mid-CretaceousSemail ophiolite in the Fars 5Fms I I I I I I I I • I -- OmanMountains [Beurrier, 1987; Immenhauser, 1995] and I i I i I [ I I I I --Oligocene were obducted in a NW direction onto the eastern Oman Dhofar anuwayropuqm,1111111• I I I I I I I I I I [ I [ I I I [ --Eocene margin [Immenhauser, 1995; Gnos et al., 1997; Peters and DAMM./RUS I [ I I t [ I [ I [ -- 50 Mercolli, 1997, 1998)]. Paleomagneticstudies of the Masirah HadramautUMM ER RADH I [ I I I I I [ [ [ [ [ [ [ ] I [ I I [ [ --Paleocene [ i i i i i i i i i i [ [ [ i i i • ......... ophiolites corroboratedthese conclusionsand ruled out the mrumaSims./Hasad ......•( : ."•::.•:••_•:•i ..... - - possibilityof a commonor relatedorigin with respectto the Semail ophiolite [Gnos and Pertin, 1996]. The Masirah I I I I II I I FayS-'"•&•&••;4--Late " "' -- Cret. Island ophiolitesalong with other fragmentsof oceanic lithospherealong the easternOman margin (Ra's Madrekah, northof SawquirahBay, seeFigure 1) weretermed the eastern • Fm mnmn•••••• vvvvvy mnmn.mn • --Early Cret. ophiolitebelt, and it was postulatedthat emplacementwas • • X.....• • •'.•-• •T--•-- related to transpressional motions between the Indo- Pakistaniand the Afro-Arabianplates at about65 Ma [Gnos et al., 1997]. m ..... M&GL+•½•- Jurassic It now becameapparent that we shouldfollow up the new data obtainedfrom Masirah Island by investigatingthe 5 / unditt Batain coast area. The stratigraphy,sedimentology, and depositionalenvironment of the BatainGroup is discussedin detailby Immenhauseret al. [1998].In thepresent paper we • / glJil '2• • X ••2•• - Triassic documentresults of structuralstudies in the Batainarea, which differ in several aspectsfrom previousstructural • • • ' - 250 interpretations.Most significant differences concern timing of obductionand associatedtectonic transport direction. Our • QarariU ['•- Vemian structural and kinematic findings, supported by biostratigraphicand sedimentologicdata [Immenhauseret al., 1998],allow us to proposea new interpretationof the Pillow basalts Lst congl. Oolitic 1st Manganese structuralevolution of the Batainarea and to brieflyoutline its palinspasticimplications. Nodular Halobia Radiolarian Shallow marine limestone limestone limestone
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