Development of a Regional Stratigraphic Framework for Devonian Reef Complexes Using Integrated Chronostratigraphy: Lennard Shelf, Canning Basin, Western Australia
The correlation of strata with complex geometries is problematic and often involves invoking a depositional model that dictates how packages of rock interact through a depositional cycle. This ‘model’ based approach is not ideal because of the assumptions made constructing the model and ultimately leads to uncertainty in correlation lines forced through strata. A more elegant approach is to use integrated chronostratigraphy. Integrated chronostratigraphy involves extracting multiple time-related, independent stratigraphic signals from the rock record to maximize the suite of correlation constraints. Iteration is often required to reach a stratigraphic solution where the constraints are in agreement. The main advantage of this approach is the reduction of uncertainty and simplification of correlation decisions. To demonstrate this approach an outcrop-based proof of concept study has been undertaken on the Middle to Upper Devonian Lennard shelf carbonate outcrops, Canning Basin, Western Australia. Samples for biostratigraphy, magnetostratigraphy, stable isotope chemostratigraphy and elemental stratigraphy have been collected from Givetian, Frasnian and Famennian, shelf to basin carbonate environments. Seventeen measured sections and described cores have captured 3.9km of stratigraphy with more than 6750 samples collected approximately every 0.59 m. This paper will discuss the various stratigraphic approaches used, outline the stratigraphic integration workflow, highlight the strengths and weakness of each component, and present the incorporation of a constrained sequence stratigraphic interpretation into a regional stratigraphic framework. This data demonstrates the applicability of the integrated chronostratigraphic approach to ancient carbonate outcrops and subsurface core and cuttings. Regional correlations, not previously possible in platform to slope settings, will be presented. To conclude, this work has resulted in the development of rules & models for how stable carbon isotopes & elemental chemostratigraphy are reflected in carbonates and how they can be used for chronostratigraphic & environmental interpretation. In addition, the high-resolution chronostratigraphic framework developed here has allowed key insights to be made on slope sequence stratigraphy, platform-slope transitions across long-term maximum flooding surfaces, and platform-top cycle architecture & development.
AAPG Datapages/Search and Discovery Article #90189 © 2014 AAPG Annual Convention and Exhibition, Houston, Texas, USA, April 6–9, 2014