Tectonic and Stratigraphic Significance of Growth Stratal Patterns Within Syn-Rift Carbonate Platforms

Steven L. Dorobek
Texas A&M University, College Station, TX

Isolated carbonate platforms are commonly initiated on fault-bounded topographic highs during crustal stretching in regional rift systems, especially those that have low pre-rift topography. Active fault displacements create predictable surface deformation patterns that strongly influence internal facies patterns and stratal relationships within syn-rift carbonate platforms.

Fault scaling laws and rules for fault growth, spacing, and linkage/interaction are important for understanding the internal stratal patterns within syn-rift carbonate platforms. Footwall highs are common nucleation sites for carbonate platforms, although paleo-wind directions and siliciclastic supply also influence facies distributions and overall platform morphology. Active fault displacements and related surface deformations during platform growth can control platform-margin locations, facies distributions across fault-bounded basement highs, siliciclastic-carbonate interactions (especially in fault-bounded depocenters), and the internal growth stratal patterns within syn-rift platforms. Wedge-like growth stratal patterns within syn-rift isolated platforms are characteristic of half-graben structural elements and are well-documented in outcrops (e.g., Red Sea region) and in seismic-reflection data (e.g., South China Sea). Flexural uplift of footwall margins of large, fault-bounded horsts is also convincingly documented by stratal relationships from some syn-rift isolated platforms that were built on horst highs from the South China Sea, although the horizontal distance between horst-bounding fault systems is critical for recognizing these growth stratal patterns.

Syn-rift carbonate platform strata may comprise important reservoirs within rift-related petroleum systems. Composite unconformities and related meteoric diagenetic facies are most common at footwall crests. Basal sandstone facies between basement and overlying syn-rift carbonate platform facies may be important aquifers for petroleum charge systems.

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