Basin-Wide Extent and Local Variability of Rift Climax Deposits: A Regional Perspective from the Miocene Upper Rudeis Formation, Suez Rift, Egypt

Paul Woodman and Rob Gawthorpe
Earth, Atmos and Env Sci, The University of Manchester, Manchester, United Kingdom

Sequence stratigraphic models for marine rift basins suggest that the rift climax phase is dominated by fine-grained basinal facies with locally restricted coarse-grained hangingwall depositional systems, due to fault-controlled subsidence outpacing sedimentation. Furthermore, interaction of local structural control with regional changes in eustasy and sediment supply is suggested to produce highly variable depositional sequences.

Integrating subsurface data along the rift axis and onshore outcrop studies of the rift margin, this study examines the sedimentological and sequence stratigraphic variability of the syn-rift Upper Rudeis Formation (early Miocene) in the Suez Rift, Egypt. We utilise an extensive subsurface database including wireline logs, biostratigraphy, core and 3D seismic together with outcrop data to present a regional synthesis for the Upper Rudeis Formation and discuss the potential interplay of controlling mechanisms upon its development. In marked contrast to established models, the Upper Rudeis Formation reflects a major basinwide renewal of clastic sediment input into the rift. This is interpreted to reflect a series of forced regressions following the previous basinal-dominated facies of the Lower Rudeis Formation, and may signify a reduction in fault activity at the rift margin.

This study highlights how regionally consistent key stratal surfaces, calibrated by biostratigraphic data can be used to correlate rift climax sequences between different structural settings within a rift. Furthermore, despite the marked variations in structurally-controlled palaeotopography in the rift, a basinwide signal within regional-scale depositonal systems can be identified. Such observations are important for reducing the risk associated with determining the presence, facies and geometry of this synrift reservior unit.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas