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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