A revised chronostratigraphic framework for the Onshore Otway Basin, implications for understanding the early development of an intra-cratonic rift margin

Abstract

This paper utilises modern reflection seismic data, surface geology and well information, including petrophysical/lithological characteristics and biostratigraphy. The aim is to construct a new chronostratigraphic framework for the Onshore Otway Basin, while answering unresolved questions about the basinâ??s early rift history. These include the order in which individual depocentres were formed, the corresponding timing of deposition of laterally varying stratigraphic packages, and which units were confined to individual rift depocentres. The integration of stratigraphic correlations, petrophysical interpretation, drill-core descriptions, petrological/lithological analysis and biostratigraphy with interpreted seismic data resulted in the identification of at least two extra chronostratigraphic sequences. This study focused on high-resolution volumetric modelling of all stratigraphic sequences within the Otway rift system. Particular attention was paid to the Early Cretaceous stratigraphy following the identification and mapping of the two previously undocumented sedimentary sequences within the Victorian section of the basin. This led to a revised chronostratigraphic framework for the Onshore Otway Basin, which, in-turn, served to explain the relationship between fluvio-lacustrine sedimentation and tectonism during the early history of intercontinental rift systems.