Late Neogene and Quaternary Vertical Motions in the Otway Coast, Southeast Australia (II): Epeirogenic Uplift Driven by Lithospheric Flexural Deformation

Abstract

Abstract:The relationship between tectonic uplift and geophysical analysis of gravity anomalies and the in-situ stress fields in the Otway Ranges, SE Australia is addressed in this study to understand the nature and possible mechanism for the neotectonic movements. The uplift axis of the ranges is coincident with the regional Bouguer gravity highs whereas thick Tertiary sedimentary successions are highly correlated with the gravity lows along the basin rift geometry. This result suggests that the gravity highs are separated by the thick Tertiary sedimentary successions. Regional structural trends associated with faults and foldings of the deformed surfaces are consistent with the prevailing NW-SE SHmax trend in this part of the continent. The anomalously positive correlation between topography and Bouguer gravity fields suggests possibly a lithospheric flexural deformation mode at a long wavelength (order of 10 2 kms) in the region. It also suggests that the reactivation of pre-existing lithospheric structures driven by plate boundary forces plays a key role in this mode.