Tectonic Controls on Carbonate Platform Stratigraphy: A Global Perspective

Steve Dorobek and Paul Crevello

Subsidence/uplift rates and variable scales and styles of deformation are the main tectonic influences that affect stratigraphic thicknesses, facies distribution, and unconformity development within carbonate platform strata.

Syn-rift subsidence in extensional basins is typically episodic and incremental. Coseismic fault slip can produce instantaneous accommodation on order of ten meters; accommodation commonly is asymmetrically generated across the top of the hanging-wall block. Internal stratal geometries within syn-rift isolated platforms record this differential tilting as converging/diverging stratal patterns; areally limited disconformities within the platform stratigraphy may also be affected by differential tilting. Abrupt stratal truncation and faulting along platform margins may occur as extensional basins evolve (Miocene, Egypt). Salt withdrawal can similarly influence carbonate platform evolution during later extension (Jurassic, Gulf Coast).

Platforms in foreland basins typically have ramp profiles that mimic the flexural profile produced by tectonic loading. During active convergence, the migrating flexural profile cratonward forces platforms to on lap or backstep cratonward (Miocene, offshore Borneo; Pliocene-Quaternary, NW Shelf Australia). Carbonate platforms located far inboard of plate margins may also be affected when preexisting basement structures are reactivated during convergence (Devonian-Mississippian, North American Cordillera).

Subsidence in strike-slip basins is not easily predicted, because deformation and subsidence mechanisms vary along-strike and evolve locally during strike-slip deformation. Platform stratigraphy may reflect both "extensional" and "compressional" styles of deformation, with coseismic fault displacement and flexure caused by sedimentary loads having important local effects (Jurassic, Morocco; Miocene, offshore Vietnam).

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California