Stratigraphic and Micropaleontologic Studies of the Upper Cretaceous Reservoir Formations in Abu Sennan Area, Western Desert, Egypt

Abstract

Study of the subsurface Upper Cretaceous (Early Cenomanian - Santonian) succession penetrated by five boreholes drilled in the southwest Abu Sennan area of Abu El-Gharadig basin, Western Desert of Egypt revealed the differentiation of three main rock units: the Khoman Formation (Khoman B Member) at the top, underlain unconformably by the Abu Roash Formation (subdivided into seven members denoted the symbols A, B, C, D, E, F, G from top to base), underlain conformably by the Bahariya Formation at the base. Investigation of the studied succession for foraminifera, ostracods and calcareous nannoplankton yielded 94 foraminifera species belonging to 50 genera, 102 ostracod species and subspecies assigned to 50 genera and 97 calcareous nannofossil species assigned to 39 genera. Biostratigraphically, 8 planktonic/benthic foraminiferal zones, 11 ostracod zones and 7 calcareous nannofossil zones could be identified; these zones have been successfully used in relative age dating and correlation of the studied rock units in the investigated boreholes. From older to younger, the Bahariya Formation is assigned as Early Cenomanian, the members from Abu Roash G to base Abu Roash E as Late Cenomanian to Early Turonian, the members from upper Abu Roash E to Abu Roash B as Turonian, the Abu Roash A Member from Turonian to Coniacian, whereas the Khoman B Member is dated as Santonian. The analysis of the tripartite biostratigraphic tools (foraminifera,