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Record of Sea-Level Fall in Tropical Carbonates - Falling-Stage Systems Tract Versus Standard Model Architecture

Schlager, Wolfgang 1; Warrlich, Georg 2
1 Earth & Life Sci., Vrije Univ. Amsterdam, Amsterdam, Netherlands.
2 Petroleum Dev. Oman, Muscat, Oman.

The record of sea-level fall in sequence stratigraphy is described by two contrasting models. The standard model (STM) postulates that deposition occurs principally during rise and stillstands of relative sea level; a continuous erosional unconformity develops during sea-level fall. The falling-stage systems tract model (FST) postulates significant deposition during sea-level fall. We treated these models as giant sedimentary structures and used sedimentologic principles, stratigraphic forward modeling and real-world case studies to determine the control parameters and stability domains of the two models. All three lines of evidence indicate that the presence or absence of the FST in tropical carbonates is not simply a function of the rate of sea-level fall but depends on the balance of the rates of erosion, sea-level fall and carbonate production. The FST is favored by high production, slow erosion and slow sea-level fall, the STM by the opposite configuration of rates. Case studies plotted in the parameter space spanned by the rates of sea-level fall, erosion and production support the modeling results. However, case-specific estimates of rates of production, erosion and sea-level fall of the distant geologic past are fraught with uncertainty and the number of case-studies with well constrained rates is rather small. It is clear though that the overall ranges of rates required for the falling-stage systems tract are common in the geologic record. Consequently, the falling-stage systems tract can be expected to be more common in tropical carbonate rocks than published records, particularly seismic data, currently indicate.


AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009