|
Mechanics, Dynamics and Geometry of Basin Inversion |
Alastair Beach Associates, 11 Royal Exchange Square, Glasgow G1 3AJ, UK
The Gulf of Suez (Clysmic) rift is a classic and well documented extensional province and has many similarities to the North Sea rift to which it is often compared. New structural mapping and fault analysis in western Sinai have shown that post-rift crustal shortening and inversion occurred across the Gulf of Suez, demonstrated by the presence of reverse faults formed as a result of overturning of normal faults, widespread sub-horizontal hydraulic fractures due to vertical stretching, low-angle thrusting and associated folding in the hangingwalls of normal faults, and steepening of bedding dips adjacent to basement stress risers, in some cases overturning stratigraphy. These features show the effect that superposition of inversion on extensional structures has on the geometry of the bedding in footwalls and hangingwalls. Observations and data from outcrop can be used to assist in the interpretation of similar structural relations in the North Sea, where post-rift contraction is also seen. Recognition of inversion-related structures is important in exploration, appraisal and development of North Sea reservoirs, for example, in estimating palaeobathymetry of Late Jurassic depocentres, in constructing cross-sections for reservoir zonation, and in evaluating fault seal and reservoir compartmentalization. Shortening in the Gulf of Suez occurred immediately after rift failure and was probably a gravity-driven process. Similar processes may have occurred in other failed rifts.
