--> Abstract: Controls on Rift Margin and Intra-Rift Depositional Systems: Examples from the Jurassic North Sea Rift and the Oligo-Miocene Suez Rift, by Ian R. Sharp, Ian Carr, Tom Dreyer, Hege Fjellbirkeland, Rob Gawthorpe, Thomas Sperre, and Mike Whittaker; #90039 (2005)

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Controls on Rift Margin and Intra-Rift Depositional Systems: Examples from the Jurassic North Sea Rift and the Oligo-Miocene Suez Rift

Ian R. Sharp1, Ian Carr2, Tom Dreyer1, Hege Fjellbirkeland3, Rob Gawthorpe2, Thomas Sperre3, and Mike Whittaker3
1 Norsk Hydro Research Centre, Bergen, Norway
2 University of Manchester, Manchester, United Kingdom
3 Norsk Hydro, Bergen, Norway

Sedimentary fill of rift basins is controlled by; relative sea level, rates of subsidence/uplift around normal faults, climate, sediment supply/provenance, and changes in fault block/drainage basin size and physiography. The relative importance of these controls varies spatially with structural location and with time due to fault growth, linkage and interaction.

We examine the interaction between rift margin/hinterland drainage systems and local intra-rift (fault block) drainage systems using subsurface and outcrop data from the Jurassic North Sea Rift and Oligo-Miocene Suez Rift. Both examples address transects from the extended rift margin to the first main fault block within the rift. In both examples high sediment supply rift margin depositional systems filled developing fault controlled accommodation space and effectively smoothed out basin physiography, such that depositional systems prograded right across developing half graben.

Intra-rift (fault block) depositional systems are characterized by limited drainage basin size. The area available to erosion is strongly dependant on the interplay between footwall uplift and relative sea level (minor changes dramatically increase/decrease drainage basin size). Sediment supply and depositional architecture is also strongly controlled by type of material available to erosion. In both North Sea and Suez examples hangingwall dipslope depositional systems are dominated by forced regression.

Where coeval rift-margin and intra-rift depositional systems meet, complex interfingering occurs, and depositional systems are “forced” axially following structural plunge and available accommodation space. Alternatively, during sea level highstand rift margin depositional systems can prograde over intra-rift fault block crests into adjacent half graben in a fill-and-spill fashion.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005