Early Bajocian to Early Maastrichtian Calcareous Nannofossils Biostratigraphy of Onshore Kuwait

Abstract

Calcareous nannofossils from onshore Kuwait were studied using cores collected from the Dhruma to Tarayat formations. The age interpretation concludes that the well sections range in age from Early Bajocian to Early Maastrichtian, Zone NJT10 to Zone CC25. The Bajocian to Tithonian strata dominated by carbonate platform, ramp, and intrashelf basin sediments of the tectonostratigraphic megasequence (TMS) AP7. The base of the AP7 is assumed to be marked by the Aalenian hiatus and the top by the early Tithonian hiatus surface. The Dhruma Formation is late Early Bajocian to early Late Bajocian in age, Subzone NJT 10a. The Sargelu-Dhruma transition unit is Late Bajocian, Subzone NJT10b. The Sargelu limestone is barren. The Najmah Shale may range from Late Bathonian to Late Oxfordian, Zone NJT11 to NJT13b. The Najmah Limestone is Late Oxfordian, Subzone NJT13b and the Jubaila Formation is Kimmeridgian in age, Zone NJT14. The evaporate deposits of the Gotnia and Hith formations are probably Kimmeridgian to Lower Tithonian Zone NJT 14 to Zone NJT 17. The Jurassic-Cretaceous boundary is placed within the Makhul Formation based on the presence of Nannoconus steinmannii minor and Nannoconus kamptneri minor. In the Middle East a three-fold Cretaceous sub-division has traditionally been used, with boundaries at the top of the Aptian and at the top of the Turonian, respectively. The Lower Cretaceous Thamama and Middle Cretaceous Wasia groups, dominated by thick carbonate ramp and siliciclastic sediments of the TMS AP8. The top of the AP8 is marked by the middle Turonian unconformity. Three Nanno zones CC1, CC2 and CC3 were identified in the Thamama Group consists of the Makhul, Minagish and Ratawi formations, and other three zones, CC8, CC9 and CC10 were identified in the Wasia Group comprises the Mauddud, Wara, Ahmadi, Rumaila and Mishrif formations. The Upper Cretaceous Aruma Group which consists of the Khasib, Mutriba, Sadi, Hartha, Qurna and Tarayat formations, dominated by Shallow-marine carbonate platform and open-marine carbonate shelf of the TMS AP9. The top corresponds to the Mesozoic and Cenozoic boundary. The Khasib, Mutriba and Sadi Limestones are barren of nannofossils, but six zones, from Zone CC18 to lower CC25 were identified in the Hartha, Qurna and Tarayat interval.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015