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1、GeoArabia,Vol.7,No.1,2002GulfPetroLink,BahrainMioceneDamFormation,QatarStratigraphy,micropaleontology,andpaleoecologyoftheMioceneDamFormation,QatarHamadAl-SaadandMohamedI.IbrahimUniversityofQatarABSTRACTTheMiocenecarbonateDamFormationiswellexposedintheJebelAl-Nak
2、hashareaofsouthernQatar.ThreesectionsweremeasuredinadetailedinvestigationoftheFormation’sstratigraphy,micropaleontology,andpaleoecology.Thisbiostratigraphicandpaleoecologicstudywassupportedbytheanalysisofmicrolithofaciesandforaminiferalassemblages.Microfossilsare
3、predominantlybenthicforaminiferarepresentedby38species,manyofwhicharemiliolineandoneisalargerform.ABorelismelomeloLocalRangeZoneofEarlyMiocene(Burdigalian)agewasrecognized.Thenatureanddistributionofthebenthicforaminiferalassemblage,inassociationwithlithofaciesevi
4、dence,indicatedageneralshoaling-upwardtrend.TheDamFormationwasstratigraphicallysubdividedintotwonewformalmembers.ThebasalAl-KharraraMemberismadeupoflimestone,marl,andclaystone,andtheoverlyingAl-NakhashMemberisacyclicassemblageofcarbonate,evaporite,andalgalstromat
5、olitefacies.Thelithofaciesaregroupedintofourmajortypesofwhichlimestone,subdividedintosixsubfacies,isdominant.TheAl-Kharrarawasinterpretedashavingbeendepositedinwarm(25°–30°C),clear,shallowwatersoftheinnerneriticzone(0–35m)thathadanelevatedsalinity(35‰–50‰)andaveg
6、etatedsubstrate.TheAl-Nakhashprobablyformedinanoscillating,veryshallow-marineenvironment(0–10mdeep,includingtidalflats),underwarmclimaticconditionsthateventuallyledtotheaccumulationofevaporitesandalgalstromatolites.INTRODUCTIONExposuresofMiocenerocksinQatararecon
7、finedtothesouthofthecountryintheAl-Nakhash,Al-Kharrara,andAbu-Samraareas(Figure1).TheyarebestexposedatJebelAl-NakhashnearthesouthernendoftheDukhanoilfield.TheMiocenerocksformirregular,isolated,benchedhillsthatrangeinheightfrom15to80m.TheyarerepresentedbytheDamand
8、Hofufformations,thelatterextendingintothePliocene.ThrallsandHasson(1956)formalizedtheDamFormation,thenamehavingbeenintroducedbySteinekeandKochinanunpublishedAr
