--> ABSTRACT: The Influence of Tectonics and Sediment Supply on Forced Regressive Deposits, by Lesley S. McMurray, Robert L. Gawthorpe; #91020 (1995).

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The Influence of Tectonics and Sediment Supply on Forced Regressive Deposits

Lesley S. McMurray, Robert L. Gawthorpe

Although eustacy is a key factor in controlling sequence development, controls such as sediment supply and tectonics are also of importance in determining stratal geometries and facies stacking patterns. This study investigates and attempts to quantify these controls comparing the architectures observed in Quaternary sequences, from the northern Peloponnesos, Greece with geometries and stacking patterns produced by computer simulations.

Quaternary sequences from the northern Peloponnesos form an offlapping and downstepping, forced regressive sequence set. The long-term relative fall in sea level is the result of tectonic uplift, although individual sequences are related to high frequency glacioeustatic sea-level change. Major strike variations in sequence geometry occur as a result of differences in sediment supply, which are largely controlled by drainage basin evolution. In the west, large antecedent drainage basins provide high rates of sediment supply allowing highstand progradation of Gilbert-type fan deltas. Progressively younger deltas offlap, downstep and are located further basinwards. Further east, low rates of sediment supply has resulted in a mainly erosional topography. Sequences here are limited to mari e terrace deposits (<10 m thick), which offlap and downstep in a similar manner to the laterally equivalent delta deposits.

The recent analogues and computer simulations provide a better understanding of processes controlling the stratal architecture of forced regressive systems tracts and sequence sets. Thus they better constrain predictions of location, geometry and lateral continuity of forced regressive reservoirs.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995