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Carbonate Slope Systems and Associated Reefs: End-Member Deposit Types, Margin Styles, and Spatial Arrangements

Playton, Ted *1; Kerans, Charles 2; Janson, Xavier 3; Harris, Paul (Mitch) 4; Kenter, Jeroen 4
(1) Chevron ETC, Houston, TX.
(2) Jackson School of Geosciences, Austin, TX.
(3) Bureau of Economic Geology, Austin, TX.
(4) Chevron ETC, San Ramon, CA.

Carbonate slope systems are volumetrically significant parts of carbonate platforms and contain stratigraphic records which reflect the unique growth, evolution, and depositional conditions of each carbonate system. The broad range in resedimentation processes and complex stratal architecture observed in these systems results in a high degree of spatial and stratigraphic heterogeneity.

Twenty outcrop and subsurface datasets were synthesized to develop an approach that organizes the depositional and architectural characteristics of carbonate slopes using classifications and end-member models for deposit types, spatial variability, stratal architecture, and styles of platform-to-slope (margin) transitions. The spectrum of deposit types can be subdivided into debris-, grain-dominated-, and mud-dominated families, where each entails a prevailing suite of sedimentary characteristics, bedding styles, resedimentation processes, and sediment sources. Spatial variations involve the position of deposition along the slope-to-basin profile, the degree of rugosity along margins and slopes, and the development of coalesced, continuous aprons along strike versus laterally-discontinuous sediment bodies. Dip-view attributes, such as clinoform curvature, downlap pattern, and margin progradation: aggradation ratio, describe the large-scale cross-sectional stratal architecture. Finally, two end-member styles of margin exist: 1) accretionary margins, characterized by an interfingered margin transition, and 2) escarpment margins, characterized by an onlapping margin transition.

Such organization of carbonate slopes provides a uniform framework for a wide range of examples, and links sediment heterogeneity with multiple scales of stratigraphic and spatial architecture. Subsequent comparison across datasets offers information on the interplay of intrinsic and extrinsic controls that affect slope development, such as reef type, accommodation setting, temporal constraints, oceanographic effects, external sediment input, antecedent topography, and platform morphology. These associations can be utilized in hydrocarbon exploration and development scenarios through enhanced prediction of reservoir presence, reservoir quality distribution, and natural fracture presence.


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