A New Approach to Imaging Deep Crustal Structures: Implications for the Crustal Architecture of Southeast Australia's Passive Margin

Abstract

In the passive margin of southeast Australia, a mosaic of tectonic structures of the Otway Basin records the protracted Cretaceous to Eocene break-up evolution of Australia and Antarctica. Here, we use an innovative approach that combines Euler deconvolution and DBSCAN clustering of global magnetic data and drill-hole-constrained interpretations of deep 2D seismic traverse to image deep-rooted, pre-rifting basement crustal structures now covered by passive margin basins. The method is used to identify the complex network of Early Paleozoic faults that were reactivated and transformed into major basing-bounding listric faults during Cretaceous rifting. Major faults identified include the Bambra, Avoca, Yarramyljup, and Moyston faults. The Yarramyljup and Moyston faults segmented the Cretaceous Otway Basin, demonstrating how basement lithospheric heterogeneities can influence basin development. Our analysis also redefines the northwest margin of the Proterozoic VanDieland microcontinent. This microcontinent acted as a rigid crustal block during the Cretaceous extension and influenced the geometries of the passive margin basin depocenters. These insights transform our understanding of the crustal architecture and structural inheritance in the tectonic evolution of southeast Australia and establish a template for imagining deep crustal structures elsewhere.