Unraveling Upper Devonian Reefal Carbonate Platform Heterogeneity and Architecture Using Integrated Chronostratigraphy: Lennard Shelf, Canning Basin, Western Australia

Abstract

High-resolution chronostratigraphic correlations are integral to meaningful stratigraphic frameworks in depositional systems, but may be difficult to achieve using traditional sequence stratigraphic or biostratigraphic approaches, particularly in geologically complex settings. In steep-sided carbonate platform systems, such correlations are essential for platform-to-slope models, characterization of strike variability and predictive sequence stratigraphy. The Canning Basin Chronostratigraphy Project (CBCP) integrates multiple independent signals (including biostratigraphy, magnetostratigraphy, elemental and isotopic chemostratigraphy, and sequence stratigraphy) extracted from Upper Devonian (Frasnian and Famennian) reefal platform exposures along the Lennard Shelf, Canning Basin, Western Australia, to arrive at well-constrained chronostratigraphic correlations and a robust shelf-to-basin composite reconstruction of the system. The resultant integrated framework allows for unprecedented examination of Lennard Shelf carbonate heterogeneity, depositional architecture and sequence stratigraphy. For example, platform-top cycles with poor age control were successfully correlated to well-dated, yet stratigraphically-complex, foreslope intervals, allowing for definition of detrital slope systems tracts and sequences. Furthermore, the approach utilizes signals that are independent of lithology or environment (i.e. magnetic polarity reversals), thus comparison of age-equivalent margin and slope systems in different paleogeographic, tectonic and depositional settings was made possible. Additional highlights include: 1) definition of a spectrum of high-frequency, reef flat-to-platform interior cycle types that exhibit non-tabular, complex internal facies architectures; 2) high-resolution correlation of a middle slope-to-platform interior transition showing variations in margin style, slope deposits and platform cycle types related to position within the Frasnian 2nd-order shift from aggradation to progradation; and 3) development of a Famennian regional sequence stratigraphic framework, where little control was previously available. This study not only proves the utility of the integrated chronostratigraphic approach, but emphasizes the implications that arise from examination of facies and architecture within such frameworks revealing insights that were not achievable with traditional sequence stratigraphic or biostratigraphic techniques alone.

AAPG Datapages/Search and Discovery Article #90189 © 2014 AAPG Annual Convention and Exhibition, Houston, Texas, USA, April 6–9, 2014