GROUND PENETRATING RADAR OBSERVATIONS OF HOLOCENE REGRESSIONAL SYSTEMS ON THE SOUTHEAST QUEENSLAND COAST, AUSTRALIA

The east coast of Australia has experienced a very different sea level history that the northeast coast of the United States. The coast of New England (NE) is classified as a Type I-II transition while the east coat of Australia is a Type V. The sea-level histories result in different coastal morphologies during the mid-late Holocene resulting from persistent transgression in NE compared with a highstand and regression in Southeast Queensland (SEQLD). Coupled with the sea-level history, sediment supply is much greater in SEQLD, which hosts the world’s largest sand islands with bedrock framed systems to the south and coral reef coasts to the north. The large quantity of available sediment has allowed for a high degree of preservation potential of coastal systems since the mid Holocene and last interglacial highstand.

During late 2012, a team of researchers investigated several coastal systems in SEQLD to elucidate the linkages between coastal landscapes, sea level and climate. The effort focused on two sites, Flinders Beach on North Stradbroke Island and the mainland beach, Nudgee Beach. The initial study applied ground penetrating radar to map the stratigraphic architecture of low-elevation plains in close proximity to the coast. Nearly 25 km of radar data were acquired. The study did not provide for coring and dating of horizons and will be addressed in a detailed follow on study. The results revealed several environments of deposition in various stages of evolution. The Flinders Beach site was composed of beach ridge complexes fronting a wetland and Pleistocene dunes. Stratigraphic relationships suggest that the wetland is older than the beach ridge system and comparable sites in SEQLD return dates of 40 kya for their initiation. The Nudgee Beach site consists of low-elevation barrier system that prograded during the late Holocene regression. The entire barrier is beach ridge complexes and radar stratigraphy suggests penetration through the regressive beach ridge systems into the underlying marine transgressive system. Each of these systems has different environmental variables and care must be taken not to attempt direct comparison without understanding the processes operating at each site that control and/or influence the site evolution.