A Proposed Classification of Facies-Fill Styles on Modern Isolated Carbonate Platforms Controlled by Variations in Platform Physiography and External Energy

Steven L. Bachtel
ExxonMobil Upstream Research, Houston, TX

Facies patterns of entire isolated carbonate platform systems are studied with LANDSAT 7 satellite data, and supplemented with literature to define lateral facies relationships along the Holocene time-line. Facies pattern variations between platforms can be studied in context with tectonic setting and modern hydrographic and climate data. Resulting relationships will lead to more predictive process-response models of facies distributions and allow the evaluation of multiple scenarios during exploration, prospect evaluation, and new field assessment.

Modern platforms are subdivided into "drowned" platforms, under-filled platforms, and filled platforms. Differences in fill patterns and the processes that produce them are interpreted to be due to the relationship between platform physiography and the external energy imposed on the platform (waves, currents, and tides). In general, platforms with deeper margins tend to be more current-dominated platforms, whereas platforms with shallow, accreted margins have interiors dominated by wave set-up and tidal current interactions. Thus, the dominant processes acting on platform interiors, and resulting facies-fill patterns, should be expected to change over time and may be correlated to periods of rapid accommodation increase induced by rapid subsidence or rapid increases in eustatic sea level.

Although there are obvious limitations to working in modern environments (observing response to one portion of a relative sea level curve and changing rates of accumulation through time) it does provide a case history where eustasy can be isolated and facies variation observed. The application of these modern observations to ancient examples is the subject of future research.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005