High-resolution sequence stratigraphy of the Maastrichtian-Ypresian succession along the eastern scarp face of Kharga Oasis, southern Western Desert, Egypt



A thick Maastrichtian-Ypresian succession, dominated by marine siliciclastic and carbonate deposits of the regionally recognized Nile Valley and Garra El-Arbain facies associations, is exposed along the eastern escarpment face of Kharga Oasis, located in the Western Desert of Egypt. The main objectives of the present study are: (i) to establish a detailed biostratigraphic framework; (ii) to interpret the depositional environments; and (iii) to propose a sequence stratigraphic framework in order to constrain the palaeogeographic evolution of the Kharga sub-basin during the Maastrichtian-Ypresian time interval. The biostratigraphic analysis suggests the occurrence of 10 planktonic zones; two in the Early Maastrichtian (CF8b and CF7), four in the Palaeocene (P2, P3, P4c and P5) and four in the Early Eocene (E1, E2, E3 and E4). Recorded zonal boundaries and biostratigraphic zones generally match with those proposed elsewhere in the region. The stratigraphic succession comprises seven third-order depositional sequences which are bounded by unconformities and their correlative conformities which can be correlated within and outside Egypt. These depositional sequences are interpreted as the result of eustatic sea-level changes coupled with local tectonic activities. Each sequence contains a lower retrogradational parasequence set bounded above by a marine-flooding surface and an upper progradational parasequence set bounded above by a sequence boundary. Parasequences within parasequence sets are stacked in landward-stepping and seaward-stepping patterns indicative of transgressive and highstand systems tracts, respectively. Lowstand systems tracts were not developed in the studied sections, presumably due to the low-relief ramp setting. The irregular palaeotopography of the Dakhla Basin, which was caused by north-east to south-west trending submerged palaeo-highs and lows, together with the eustatic sea-level fluctuations, controlled the development and location of the two facies associations in the Kharga Oasis, the Nile Valley (open marine) and Garra El-Arbain (marginal marine).