Litho- and chronostratigraphy of holocene sedimentary successions preserved in Lake Illawarra, NSW, Australia

Abstract

Using a Holocene barrier estuary, Lake Illawarra, New South Wales, Australia, as an example, a detailed litho- and chrono-stratigraphy of the Holocene estuarine deposits has been investigated. Forty kilometres of seismic surveys, 61 vibracores, supplemented by auger drill holes and trenches, and faunal analysis were used in this study. A detailed chronology of the infilling of the barrier estuary has been established using 121 aspartic acid derived ages and 14 radiocarbon ages. The results provide a detailed chronology for the deposition of marine transgressive deposits between ca. 8 and 5 ka years ago. Barrier growth, initiated with rising sea levels during the post-glacial marine transgression and subsequent Holocene sea level highstand, resulted in the development of a low-energy back-barrier depositional environment from ca. 5 ka years ago, and fluvial progradation into the present Lake Illawarra basin from ca. 2 ka years ago. The results from Lake Illawarra indicate that the generalised evolution of the barrier estuary occurred in five geomorphologically distinct phases associated with rising sea levels following the last glacial maximum and the subsequent Holocene sea level highstand.