Redating the earliest evidence of the mid-Holocene relative sea-level highstand in Australia and implications for global sea-level rise

Authors

Amy J. Dougherty, University of WollongongFollow
Zoë Thomas, University of New South Wales
Christopher Fogwill, University of New South Wales
Alan Hogg, University of Waikato
Jonathan G. Palmer, University of New South WalesFollow
Eleanor Rainsley, Keele University, University of WollongongFollow
Alan Williams, University of New South Wales
Sean Ulm, James Cook University (JCU), James Cook UniversityFollow
Kerrylee Rogers, University of WollongongFollow
Brian G. Jones, University of WollongongFollow
Chris Turney, University of New South WalesFollow

RIS ID

137784

Publication Details

Dougherty, A. J., Thomas, Z. A., Fogwill, C., Hogg, A., Palmer, J., Rainsley, E., Williams, A. N., Ulm, S., Rogers, K., Jones, B. G. & Turney, C. (2019). Redating the earliest evidence of the mid-Holocene relative sea-level highstand in Australia and implications for global sea-level rise. PLoS ONE, 14 (7), 1-19.

Abstract

Reconstructing past sea levels can help constrain uncertainties surrounding the rate of change, magnitude, and impacts of the projected increase through the 21st century. Of significance is the mid-Holocene relative sea-level highstand in tectonically stable and remote (far-field) locations from major ice sheets. The east coast of Australia provides an excellent arena in which to investigate changes in relative sea level during the Holocene. Considerable debate surrounds both the peak level and timing of the east coast highstand. The southeast Australian site of Bulli Beach provides the earliest evidence for the establishment of a highstand in the Southern Hemisphere, although questions have been raised about the pretreatment and type of material that was radiocarbon dated for the development of the regional sea-level curve. Here we undertake a detailed morpho- and chronostratigraphic study at Bulli Beach to better constrain the timing of the Holocene highstand in eastern Australia. In contrast to wood and charcoal samples that may provide anomalously old ages, probably due to inbuilt age, we find that short-lived terrestrial plant macrofossils provide a robust chronological framework. Bayesian modelling of the ages provide improved dating of the earliest evidence for a highstand at 6,880±50 cal BP, approximately a millennium later than previously reported. Our results from Bulli now closely align with other sea-level reconstructions along the east coast of Australia, and provide evidence for a synchronous relative sea-level highstand that extends from the Gulf of Carpentaria to Tasmania. Our refined age appears to be coincident with major ice mass loss from Northern Hemisphere and Antarctic ice sheets, supporting previous studies that suggest these may have played a role in the relative sea-level highstand. Further work is now needed to investigate the environmental impacts of regional sea levels, and refine the timing of the subsequent sea-level fall in the Holocene and its influence on coastal evolution.

Grant Number

ARC/CE170100015