AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Non-Volcanic Rift Margin Evolution: The Temporal and Spatial Relationships Between Uplift, Extension and Erosion, Gulf of Suez and Northern Red Sea, Egypt
(1) Department of Earth Sciences, Royal Holloway University of London, Egham, United Kingdom.
This research aims to determine the thermochronological evolution of the Gulf of Suez and Northern Red Sea rift margins and relate this evolution to the regional tectonic regimes as well as to the geomorphic evolution of the margin and sediment provision of the syn-rift sequences in the rift depocentres.
Apatite fission track and (U-Th)/He thermochronometry on granitic basement lithologies from the two key margins are used to constrain the timing, rate, and pattern of uplift and denudation associated with the rift. A large range of fission track ages, with short mean track lengths, suggests exhumation from within the partial annealing zone. All (U-Th)/He ages are >19.2 Ma, suggesting that the basement had cooled to below the closure temperature by the early Miocene. Simultaneously modelling both thermochronometric datasets in HeFTy highlights an Eocene-Late Oligocene phase of cooling in the Gulf of Suez. If interpreted as onset of rift activity, this would pre-date the previously interpreted onset at ~25 Ma at the southern Red Sea margin, and necessitate different rifting mechanisms. Alternatively this discrepancy may by the response to a transition of stress regimes from Syrian Arc and Alpine deformation to extension.
DEM data was qualitatively and quantitatively analysed in ArcGIS. Delineated stream networks were compared with fault maps, highlighting fundamental relationships between structure and geomorphic evolution. The drainage network has also been compared with published isopach maps, presenting possible source and fill points for key hydrocarbon reservoirs within the rift basin. Geomorphic indices have been used to assess the development of catchment areas along the rift margin. Variation in these factors have been interpreted as the result of a structural control primarily from pre-existing basement fabrics. Longitudinal stream profile analysis of high-order streams also demonstrates the structural control.
Thermochronometric evidence indicates that the basement was at shallow depth at rift initiation, with prior cooling resulting from, in part Syrian Arc inversion and uplift. As rifting began the basement was quickly exhumed on the flanks. GIS analysis indicates that the drainage patterns are probably ancestral, established prior to or at the initiation of rifting and continued through to the Present Day. This has significant implications for the delivery of syn-rift sediments, and subsequent locations of the reservoirs material.