Ecological Accommodation; A Key to the Interpretation of Carbonate Platform Architecture Variability

Luis Pomar¹ and Christopher G. St. C. Kendall^2
1Departament de Ciencies de la Terra, Universitat de les Illes Balears, Palma de Mallorca, Spain
²Department of Geological Sciences, University of South Carolina, Columbia, SC

The complex spectrum of heterogeneous facies architectures of carbonate platforms includes: 1) low-relief carbonate ramps that match a shelf-equilibrium profile and are composed of either loose, fine-grained sediments produced in shallow areas but shed downdip, or sediment mostly produced and accumulated in the deeper part of the depositional profile, 2) open shelf platforms involving large-skeleton metazoans with moderate capacity to build above the shelf-equilibrium profile, 3) platforms with biotic components capable of building up to sea level with a maximum ecological accommodation, and 4) platforms with steep, massive and thick marginal slopes.

The depositional order of the basic accretional units (sequences, cycles, parasequences, and/or beds), their geometry and stacking patterns provides a template for the interpretation of each platform succession. The interpretation rebuilds each platform in terms of its distinctive and unique response to geotectonic setting and the physical, chemical and biological conditions at deposition, expressed in terms of changes in both physical and ecological accommodation. Physical accommodation relies in basin floor conditions and hydrodynamics, while ecological accommodation relies on the potential to build upward. Changes in ecological accommodation depend of biological evolution, changes in ecological conditions and on the temporal/spatial evolution of the depositional settings.

Each succession has a distinct depositional profile, facies belt distribution, and platform architecture that guides the analysis of the inferred character of the ecology of ancient biota and reduces the uncertainty of interpretation. This system formulates new questions leading to realistic interpretations and enhanced predictions of lithofacies heterogeneities.

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