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oa Cretaceous Sequence Stratigraphy of Westrenzagros Outcrops from Kurdistan Region, N.Iraq
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, GEO 2010, Mar 2010, cp-248-00338
Abstract
The exposed Cretaceous sequence in Kurdistan region were studied from four outcrops sections<br>(Qamchuqa, Dokan, Smaqwly and Safin),and correlated also with oil wells (Taq-Taq and<br>Chamchaml).They were deposited in pre-foreland and foreland basin within a time framework extends<br>from the Barremian to the late Maastrchtian including Qamchuqa, Dokan, Gulneri, Kometan, Shiranish<br>and Tanjero Formations. In this work Cretaceous sequence subdivided into four 3rd order sequences,<br>bounded by five sequence boundaries of type 1 or 2,and occasioanly type three ,they are; 1-Intra-<br>Barremian (S.B.T.1),2- Upper Early to middle Cenomanian (S.B.T.2),3- Upper most late Cenomanian<br>(S.B.T.2),4- Middle Campanian (S.B.T.2),and 5-late Maastrchtian(S.B.T.1).The nature and duartion of<br>each sequnecs and their bounadries emphasized by large and/or planktonic foraminifera zonations. The<br>first third order ( Intra-Barremian to lower early Cenomanian) represents by Qamchuqa Formation,<br>which consists of aggradational to progradational rudist bearing carbonate ramp facies associations<br>(600m thicK). This sequence was terminated either by drowning or by sub aerial erosion indicated by<br>Cenomanian unconformity and coincides with the international Cenomanian-Turonian euxinic event<br>(OAE2).The Late Cenomanian 2nd third order sequence consists of Oligosteginal carbonates are related<br>to Dokan formation, terminated with submarine erosion .The next third order resembled by Gulneri<br>Formation (Turonian to E. Campanian) present as condensed section of black shale. The fourth 3rd<br>sequences ,represnt by Kometan formation of remarkable shallowing upwards succession from deep<br>outer to middle and inner shelf and capped by hard ground surface within middle Companian<br>unconformity surface. late Campanian to late Maastrchtian third order sequences of outer shelf ,<br>turbidities facies and reef build up(Aqra Fn.), occasionally intercalated with oceanic red bed (ORB),<br>within the Zagros foreland basin acts as the best productive reservoir in the upper Cretaceous of<br>Kurdistan region.