Cretaceous (Albian–?early Santonian) palynology and stratigraphy of the Abu Tunis 1x borehole, northern Western Desert, Egypt

Abstract

A palynological analysis has been conducted on the Cretaceous sediments of the Abu Tunis 1x borehole, in the northern Western Desert, Egypt. The palynomorphs recovered have been analysed both qualitatively and quantitatively, and permit a refinement of the original stratigraphy with the identification of four time-rock units. These have been divided into four informal sporomorph units and one dinoflagellate cyst palynozone. These biozones are, from oldest to youngest: the Afropollis jardinus-Tricolporopollenites-Elaterosporites klaszii Assemblage Zone (early–mid Albian), the Elaterosporites verrucatus-Sofrepites legouxae-Cretacaeiporites Assemblage Zone (late Albian–early Cenomanian), the Sofrepites legouxae Partial Range Zone (early–?mid Cenomanian), the Proteacidites cf. africaensis Total Range Zone (mid–late Cenomanian) and the Canningia senonica Total Range Zone (early? Santonian). A barren interzone has been identified immediately below the youngest palynozone, and this may be related to the unfavourable lithology (i.e., limestone and dolostone). The absolute abundances of spores and pollen represent the first quantitative description of an Egyptian Albian–Cenomanian palynofloral, a flora that is characteristic of the Albian–Cenomanian Elaterate Phytogeographical Province. The early Santonian palynoflora is exclusively marine phytoplankton; terrestrial palynomorphs representative of the Senonian Palmae Province are completely absent. The quantitative and semi-quantitative distributions of Afropollis jardinus are compared with similar semi-quantitative distributions of this species from other wells in the northern Western Desert of Egypt, and this permitted the identification of a mid Albian–early Cenomanian Afropollis jardinus ‘acme’ as an important local biostratigraphical event in the mid Cretaceous.