Tectonostratigraphic evolution, seismic interpretation and 2D section restoration of the offshore eastern Otway Basin, Victoria, Australia, The

Abstract

The Otway rift basin is located on the northwest trending passive margin that extends from southeast Australia to the neighboring the Sorell Basin, west of King Island. The formation of the Otway Basin is associated with the breakup of Gondwana during the late Jurassic/early Cretaceous, and the basin comprises two rifting and multiple inversion events reflected by eight basin supersequences. The basin contains sediments deposited from Upper Jurassic to Holocene and the extent of the basin is 150,000 km2, of which 80% lies offshore. Although the eastern Otway Basin has been investigated in both the onshore and the shallow marine section, a tectonostratigraphic framework for the offshore part still needs to be developed in detailed explanation, which will be rewarding for hydrocarbon exploration purposes. This study aims to interpret and reconstruct the structural evolution of the Otway Basin by integrating tectonostratigraphy, well data, 2D seismic profiles, 3D seismic cubes, and 2D structural restorations. Seismic interpretation is performed for each 3D seismic survey by creating structure maps and labeled seismic profiles. Regional structure maps were also generated at each individual basinal phase by using 2D & 3D seismic data together to apply seismic interpretation techniques. Schlumberger`s Petrel software is used for structural and stratigraphic interpretation on 2D and 3D seismic data set provided by Geoscience Australia whereas Midland Valley`s Move software is used for 2D kinematic reconstruction and restoration throughout the basin. Structural characteristics and depocenter developments for rifting phases, fault types, quantification of extension amounts and designation of regional deformation model is conducted within the scope of this study. Different structural trends composed due to two separate rifting phases are mapped and investigated through seismic profiles and four cross sections restored from Investigator 3D Survey from the Offshore Eastern Otway Basin used to calculate extension amounts (IL 300 - 6.63% [2.626 km], IL – 700 11.11% [5.56 km], IL – 1150 11.16 % [5.63 km], IL – 1700 11.05% [5.53 km]). In addition, regional lithospheric extension model is determined by comparing and contrasting with the existed deformation models.