AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
High Resolution Chronostratigraphy of a Carbonate Platform Top to Reef Transition, Upper Devonian, Canning Basin, Western Australia
(1) Chevron Energy Technology Company, San Ramon, CA.
(2) Chevron Energy Technology Company, Aberdeen, United Kingdom.
(3) Institute for Tibetan Research, Beijing, China.
(4) University of Western Australia, Perth, WA, Australia.
(5) Chemostrat Incorporated, London, United Kingdom.
(6) Chemostrat Incorporated, Houston, TX.
(7) University of Washington, Seattle, WA.
(8) Geological Survey of Western Australia, Perth, WA, Australia.
High-resolution chronostratigraphic correlations are integral for the development of stratigraphic frameworks that provide the foundation for reservoir exploitation. Typical subsurface datasets and dating constraints are limited in terms of lateral continuity and resolution, making fine-scale reservoir characterization difficult. To address these challenges, the Canning Basin Chronostratigraphy Project (CBCP) was developed to demonstrate alternative high-resolution correlation techniques on an ancient carbonate outcrop through the integration of magnetostratigraphic, chemostratigraphic, biostratigraphic, and sequence stratigraphic approaches. These integrated approaches can be applied to subsurface datasets with available core and cuttings.
This particular study focuses on an Upper Devonian (Frasnian) outcrop exposure, Canning Basin, Western Australia, that features the transition from platform interior -to- reef flat depositional environments. Two detailed section transects were measured and sampled for magnetostratigraphy (polarity and susceptibility), inorganic stable isotope geochemistry, inorganic whole rock geochemistry, and gamma ray response. Principal correlation constraints include physical traces, conodont biostratigraphy, and U-Pb absolute dating combined with radiogenic 87Sr/86Sr geochemistry. Sequence stratigraphic guidelines, the various data profiles, and the available constraints were integrated to arrive at a high resolution chronostratigraphy across the outcrop exposure.
This high resolution correlation framework allows for detailed examination of the transition from restricted platform interior cycles to open marine reef flat cycles. Firstly, the integrated framework highlights the limitations of traditional unconstrained 1D and 2D stacking pattern-based predictions, where as much as 70m of stratigraphy were incorrectly correlated. Furthermore, facies and cycle analysis within the chronostratigraphic framework sheds insights on the nature of cycle and bed interfingering, the distribution and timing of siliciclastics, and characteristics of significant surfaces such as sequence boundaries. Overall, the results of this study and the CBCP will not only provide additional subsurface correlation techniques, but will also improve our understanding of reefal carbonate shelf-to-basin transitions and platform evolution.