--> Abstract: Characterization, Variations, and Controls of Reefal Carbonate Foreslopes, by Ted E. Playton, Xavier Janson, and Charles Kerans; #90078 (2008)

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Characterization, Variations, and Controls of Reefal Carbonate Foreslopes

Ted E. Playton1, Xavier Janson2, and Charles Kerans1
1Geological Sciences, University of Texas at Austin, Austin, TX
2Bureau of Economic Geology, Austin, TX

Allochthonous deposits that flank reef margins (reefal carbonate foreslopes) display heterogeneity along strike and dip due to diverse sediment sources and resedimentation processes. This variability accounts for the paucity of predictive relationships that link foreslope composition to stratal architecture, which are critical tools for hydrocarbon exploration and production programs. This study examines outcrop data and examples from literature of carbonate slope and basin systems, and addresses the 1.) depositional elements and seismic-scale stratal geometries of reefal carbonate foreslopes, 2.) compositional and geometrical variations that exist, and the 3.) parameters that control these variations. The depositional elements that compose reefal carbonate foreslopes are 1.) collapse elements (breccias and blocks) from gravitational failure of lithified material, 2.) grain-shedding elements (grainstones and gravels) from offbank transport of sand and pebbles, and 3.) hemipelagic elements (mud-dominated fabrics) from periplatform shedding and background accumulation. In terms of seismic-scale stratal patterns, clinoformal, accretionary margin systems are fundamentally different from escarpment margin systems that exhibit foreslope onlap. Characterization of foreslope examples in terms of their elements and stratal patterns shows a spectrum of gross sediment composition, margin configuration, stratal evolution, internal deposit architecture, depositional profiles, and scales. Groups of foreslope systems that possess similar combinations of compositional and geometrical characteristics delineate major foreslope types. The variations that exist among reefal carbonate foreslopes are linked to the interplay of multiple controls, including accommodation, reef fabric and fauna, platform morphology, slope height, tectonic setting, and siliciclastic input.

 

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas