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Fault-Propagation Folding and Syn-Rift Sedimentary Response: An Outcrop Case Study from the Hadahid Monocline, Suez Rift, Egypt

Lewis, Matthew M.*1; Jackson, Christopher A.1; Gawthorpe, Robert L.2; Whipp, Paul 3
(1) Department of Earth Science and Engineering, Imperial College, London, United Kingdom.
(2) Department of Earth Science, University of Bergen, Bergen, Norway.
(3) Exploration, Statoil ASA, Bergen, Norway.

The early growth of normal faults is typically associated with the development of fault-propagation folds and the deposition of wedge-shaped syn-rift deposits that typically thin and onlap towards at-surface, monoclinal growth folds. Stratigraphic traps may develop on the limbs of these growth folds, although, due to limited seismic resolution and sparse well data, the architecture and facies distribution of early syn-rift stratigraphy is often difficult to constrain in the subsurface.

To improve our understanding of the along-strike variability in structural style and the control that fault-related folding has on the architecture of early syn-rift strata we focused on a 2.5 km long segment of the Hadahid Monocline in the Suez Rift, Egypt. Field mapping and sedimentary logging indicate that the monocline dips 40-60o towards the SW and that an, overall deepening-upwards, early syn-rift succession onlaps the monocline limb.

Marked variability in the magnitude of erosion along the pre-rift/syn-rift contact and the overall geometry of early syn-rift succession allow us to recognise four stages in the tectono-stratigraphic evolution of the Hadahid Monocline: (i) T1 - base-level fall and sub-aerial erosion of pre-rift stratigraphy prior to the onset of faulting or folding; (ii) T2 - base-level rise and the initiation of shallow marine sedimentation during a period characterised by limited at-surface deformation; (iii) T3 - initiation of at-surface growth folding in response to the onset of fault-tip propagation, development of a hangingwall syncline and deposition of wedge-shaped syn-rift units that thin and onlap toward the growth fold; and (iv) T4 - amplification of the growth fold, linkage with the adjacent fold segment, continued deposition of cross-sectional wedged-shaped syn-rift package, and formation of a single, coalesced, proto-hangingwall, synclinal depocentre.

This study highlights the control that fault-propagation folding and changes in base-level has on the architecture of early syn-rift stratigraphic traps in extensional settings. In addition, here we emphasise the value of well exposed outcrop examples in reducing uncertainty of future hydrocarbon exploration and production.


AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California