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