TECTONIC AND DEPOSITIONAL CONTROLS ON SYN-RIFT CARBONATE PLATFORM SEDIMENTATION

All scales of tectonic deformation influence the location, sizes, shapes, and internal stratigraphy of carbonate platforms that form in active rift settings. Normal and oblique-slip faults bound the tectono-geomorphologic features that are typically found across rift settings. These fault-bounded structural elements can provide substrates for shallow-water carbonate platforms if they are submerged to shallow water depths. Thus, the incremental and long-term growth of tectonic structures, and interactions between Surface processes and carbonate depositional systems that develop around or on top of these structures, determines nearly all stratigraphic aspects of syn-rift carbonate platforms. Isolated carbonate platforms are the most common type of platforms in active rift settings because the), form on fault-bounded syn-rift highs. Steeply dipping fault scarps and tilted to flat-topped depositional Surfaces control where shallow-marine carbonate deposition is possible. Faultscaling laws and rules for fault growth, spacing, and linkage/interaction are important for understanding the internal strata[ patterns within syn-rift carbonate platforms. Footwall highs are common nucleation sites for carbonate platforms, although paleo-wind directions and siliciclastic Supply to adjacent depocenters also influence facies distributions, platform morphology, and overall stratigraphic development. 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 updip fault-bounded depocenters), and the internal growth stratal patterns within syn-rift platforms. Wedge-like growth strata] patterns within syn-rift isolated platforms are characteristic of half-graben structural elements and are well documented in outcrop and subsurface examples. Flexural uplift of footwall margins of large, fault-bounded horsts is also documented by stratal relationships from syn-rift isolated platforms that build on hors thighs. Syn-rift thermal subsidence may influence where carbonate facies are distributed across the rift system, as well as time dependent accumulation rates for each platform. Syn-rift carbonate platform strata can form important petroleum reservoirs within rift-basin systems. They also provide critical records for understanding the tectonic evolution and depositional history of rift systems.