Interplay of tectonism and eustasy during the Early Permian icehouse: Southern Sydney Basin, southeast Australia

Abstract

This investigation presents an outcrop-based integrated study of sedimentological analysis and sequence stratigraphy applied to the Lower Permian sedimentary succession in the southern Sydney Basin, Australia. This succession accumulated in several depositional environments and sub-environments that range from non-marine (fluvial) to marine (outer shelf), representing the fill of a sedimentary basin that resembles a fault-bounded, rift basin. The stratigraphic analysis indicates a deepening-upward trend, and the sequence stratigraphic approach has established that these sediments can be attributed to the lowstand, transgressive, and highstand systems tracts. Lowstand sediments can be defined by fluvial facies that are located between the subaerial unconformity and the maximum regressive surface. Transgressive facies correspond to estuarine, upper and lower shoreface, and inner and outer shelf depositional environments and are located between the maximum regressive and the maximum flooding surfaces. Highstand bottomset sediments are accumulated above the maximum flooding surface and are represented by outer shelf facies. The stratigraphic architecture indicates the development of an almost complete depositional sequence, mainly developed under the control of tectonically induced subsidence, but also influenced by the high sedimentation rates and the high gradient of the inherited topography. Eustatic sea-level fluctuations were of minor importance during the deposition of the examined sediments.