--> Abstract: Stratigraphy and Stromatolites in a Late Devonian Reef Tract, Canning Basin, Western Australia, by N. P. Stephens; #90925 (1999)

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STEPHENS, NAT P., University of California, Department of Geology, Davis, CA

Abstract: Stratigraphy and Stromatolites in a Late Devonian Reef Tract, Canning Basin, Western Australia

The Late Devonian reef tract of the Canning Basin with spectacular outcrops and generally undolomitized carbonates provides an excellent venue for applying stable isotope curves to help build a sequence stratigraphic framework and document the paleoecologic relationships between the microbial ecosystem and a reef enviroment during a mass extinction. Microbial communities in the Late Frasnian and Famennian compose much of the reef and appear to be responsible for the occlusion of much of the primary porosity due to microbially induced calcite precipitation. Microbial communities in the Late Frasnian may have developed in response to regional changes in basin circulation or to global environmental stress prior to the mass extinction at the Frasnian-Famennian boundary. Placing these microbial communities in a temporal framework and correlating sequences between outcrops has proven difficult in the reef facies due to poor biostratigraphic time control and lack of sequence-defining exposure surfaces. Preliminary isotopic data suggest that carbon isotopic excursions from the Canning Basin correlate to excursions from Europe and Canada and can be used for relative time control within the basin. Objectives of this research are to 1) build a temporal framework through carbon isotopic curves for the Late Devonian in the Canning Basin, which will aid in unifying a sequence stratigraphic model for the basin, 2) outline the distribution and cementation of microbial dominated reefs, which will contribute to models of primary porosity in reef, hydrocarbon traps, and 3) test paleoecologic hypotheses of microbial proliferation prior to the Late Devonian mass extinction.

AAPG Search and Discovery Article #90925©1999 AAPG Foundation Grants-in-Aid