--> Abstract: Variation in Fan Delta Stacking Patterns Related to Synsedimentary Growth of Extensional Fault-related Folds, Miocene Suez Rift, Egypt, by S. Gupta, J. R. Underhill, I. R. Sharp, and R. L. Gawthorpe; #90937 (1998)

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Abstract: Variation in Fan Delta Stacking Patterns Related to Synsedimentary Growth of Extensional Fault-related Folds, Miocene Suez Rift, Egypt

GUPTA, SANJEEV and JOHN R. UNDERHILL, The University of Edinburgh, Edinburgh, UK; IAN R. SHARP and ROB L. GAWTHORPE, The University of Manchester, Manchester, UK. ([email protected])

Growing structures exert an important control on the architecture of coeval basin margin sedimentary systems. We investigate how the synsedimentary growth of extensional fault-related folds has influenced the evolution of coarse-grained deltaic depositional systems in a Miocene marine half graben, on the eastern margin of the Gulf of Suez rift. Excellent exposures of syntectonic strata permit analysis of patterns of fan delta progradation in relation to fold development.

The footwall-sourced Alaqa delta complex comprises multiple, stacked, prograded Gilbert-type deltas, which are characterized by shoreline migration distances of several kilometers. The succession records multiple episodes of delta progradation punctuated by abrupt pulses of delta top drowning. Stacking patterns of the Gilbert deltas show marked variation when traced along fault strike. At fault tips or in zones of fault intersection, deltas are characterized by vertical stacking.

Traced laterally, towards the center of blind fault segments, however, the stacked deltas exhibit progressive rotation. Here, successive deltas prograde across the rotated tops of older drowned delta wedges indicating that the delta systems were deposited above actively growing fault-related fold.

Repeated cycles of delta progradation and drowning may be a response to either early Miocene glacioeustatic sea-level fluctuations or sediment supply variations, superimposed upon fault-controlled subsidence. Variation in delta stacking geometries results from along-strike variation in fold amplification due to displacement variation on blind, but upwards- and laterally-propagating extensional fault segments. Complex offlap-onlap delta geometries arise in response to the interaction of fold growth and baselevel/supply variations.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah