--> ABSTRACT: The Role of Biotic and Abiotic Constituents in the Development and Diagenesis of Middle to Late Paleozoic Carbonate Platforms: Outcrop and Subsurface Examples from the CIS, by W. G. Zempolich, H. E. Cook, V. G. Zhemchuzhnikov, A. Zorin, A. Giovvaneli, M. Viaggi, and V. Y. Zhaimina; #91021 (2010)

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The Role of Biotic and Abiotic Constituents in the Development and Diagenesis of Middle to Late Paleozoic Carbonate Platforms: Outcrop and Subsurface Examples from the CIS

ZEMPOLICH, W. G., H. E. COOK, USGS, V. G. ZHEMCHUZHNIKOV, A. ZORIN, A. GIOVANNELI, M. VIAGGI, and V. YA ZHAIMINA

Petrographic and geochemical analysis of Upper Devonian to Lower Permian reef boundstones, cementstones, and oolitic grainstones has been completed on examples from S. Kazakstan and S. Russia. These data indicate that, through time, major shifts took place in the composition and spatial distribution of reef biota and the mineralogy and stable isotopic composition of abiotic marine precipitates. Corresponding shifts in the morphology of carbonate platforms and the spatial distribution of reservoirs suggest a strong biotic and abiotic influence on platform development and diagenesis.

Upper Devonian reefs are composed of algal-stromatoporoid-calcisponge boundstone and form reef-rimmed platforms. Boundstone and slope deposits are cemented by fibrous and radiaxial fibrous calcite; inner shelf deposits are both dolomitized and karsted. Tournaisian carbonates lack a defined organic margin and form ramps; inner-shelf facies are extensively dolomitized. Visean and Serpukhovian carbonates consist of grainstone-rimmed platforms and slope mounds. Mounds are composed of sponge-bryozoan-Tubiphytes-algae boundstone and cementstone. Radiaxial calcite forms thick linings in stromatactis cavities and infills skeletal frameworks; shelf facies are dolomitized and karsted due to repeated exposure. Bashkirian shelf margins consist of phylloid algae-brachiopod boundstone and cementstone; shelf interiors contain prolific oolitic grainstone. Bashkirian ooids and marine cement were predominantly composed of aragonite. Lower Permian shelf margins and slope mounds are comprised of bryozoan-Tubiphytes-algae boundstone and cementstone, Palaeoaplysina rudstone, and foram-rich lithologies. Incomplete infilling of boundstone and rudstone lithologies by radiaxial calcite and subaerial exposure resulted in the preservation of primary growth and shelter cavities.

U. Devonian through L. Carboniferous reefal margins and slope mounds are relatively tight due to marine calcite cementation; porosity in shelf interiors is enhanced by dolomitization and karsting. M. Carboniferous and L. Permian reefal and shelf lithologies are porous due to exposure-related diagenesis of aragonite and calcite components.

AAPG Search and Discovery Article #91021©1997 AAPG Annual Convention, Dallas, Texas.