Tectonophysical Processes and Their Surface Feedback in the Ashmore Platform Region: A Combined 2-D and 3-D Seismic-Reflection Analysis

Abstract

A 2D and 3D seismic-based structural analysis of the Ashmore Platform in NW Australia is aiming to unravel the tectonophysical processes resulting from an early-stage foreland basin deformation in the Timor Sea region. A re-evaluation of lithospheric flexural models proposed for this region (i.e. Londoño & Lorenzo 2004; Langhi et al. 2011) and a comparison against the observed fault pattern reveal various differences. The study area provides an exceptional opportunity to examine the early-stage development of the foreland basin between the colliding Australian continental margin and the Banda arc. The Timor region's abundant normal faulting within a remotely convergent plate-margin setting has been a debated subject with numerous studies devoted to explain this issue. 2D elastic half-beam models of Londoño & Lorenzo (2004) and simple bending elastic beam models from Langhi et al. (2011) evidence that bending of the Australian lithosphere is a key mechanism responsible for the current tectonic development of the Timor Sea. This seismic-based tectonic study constrains these numerical models inferring a combination of mechanisms to explain the modern extensional faulting of the study area. This study integrates interpretations from 2D and 3D seismic-reflection data with standard wireline logs of two wells to subdivide the subsurface of the study area into five seismic units, corresponding to a Paleozoic basement, thick Mesozoic clastic and carbonate sequences and a topmost Cenozoic succession of predominantly carbonate rocks. This sedimentary succession is deformed by numerous normal faults, of which 165 were mapped in 3D, particularly focusing on the displacement of the recent to sub-recent sedimentary cover. The modern structural styles encountered in the study area resulted in the differentiation of three normal-fault sets. This seismic-based tectonic analysis ultimately ground truths theoretical models of lithospheric flexure, highlighting the importance of combining modelling studies with observational field-based constraints.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015