Lagoonal carbonate deposition preceding rifting-related uplift: evidence from the Bartonian–Priabonian (Eocene) of the northwestern Gulf of Suez (Egypt)

Abstract

Sedimentary successions in the northwestern Gulf of Suez provide important clues to the understanding of the geological evolution of NE Africa during the middle and late Eocene. This study focuses on detailed facies analyses in order to characterize the depositional environments and system tracts of the Bartonian–Priabonian succession cropping out in this area. Bartonian–Priabonian carbonate deposits in five stratigraphic sections constitute, from base to top, the Gebel Hof, Observatory, Sannur, Qurn, and Wadi Hof Formations. These formations contain four local assemblage zones of larger benthic foraminifers. Analyses of litho-, bio-, and microfacies in the succession resulted in the recognition of 12 lithofacies types. These litho-facies are represented by packages of lime-mudstones, wackestones, packstones, pack- to grainstones, grainstones, rudstones, boundstones and dolomites. These lithofacies have been grouped into four genetically-related facies associations that represent, respectively, tidal flats/shallow subtidal, restricted-shelf/lagoonal, shoal bar, and outer-shelf lagoon/reefal depositional environments in a downslope shallow-marine inner-ramp setting. The vertical transitions of these facies associations, representing facies changes through time, imply fluctuations of the regional sea level. The two peaks in the Bartonian correspond to well-known global eustatic sea-level rises; the pronounced Priabonian regression must be ascribed to the known global eustatic sea-level fall in combination with regional tectonic activity. The facies distribution suggests that the study area was located in the direct vicinity of some islands during the Bartonian–Priabonian.