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

Dougherty, Amy J., Thomas, Zoë A., Fogwill, Christopher, Hogg, Alan, Palmer, Jonathan, Rainsley, Eleanor, Williams, Alan N., Ulm, Sean, Rogers, Kerrylee, Jones, Brian G., and Turney, Chris (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). e0218430.

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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.

Item ID: 58953
Item Type: Article (Research - C1)
ISSN: 1932-6203
Keywords: sea-level
Copyright Information: © 2019 Dougherty et al. This is an open access article distributed under the terms of the Creative Commons Attribution (CC x 4.0) License.
Funders: Australian Research Council
Projects and Grants: Australian Research Council Centre of Excellence for Australian Biodiversity and Heritage (CE170100015), Australian Research Council Future Fellowship (FT120100656), Australian Research Council Laureate (FL100100195)
Date Deposited: 19 Jul 2019 05:00
FoR Codes: 04 EARTH SCIENCES > 0406 Physical Geography and Environmental Geoscience > 040606 Quaternary Environments @ 50%
21 HISTORY AND ARCHAEOLOGY > 2101 Archaeology > 210102 Archaeological Science @ 25%
21 HISTORY AND ARCHAEOLOGY > 2101 Archaeology > 210101 Aboriginal and Torres Strait Islander Archaeology @ 25%
SEO Codes: 95 CULTURAL UNDERSTANDING > 9505 Understanding Past Societies > 950503 Understanding Australias Past @ 50%
96 ENVIRONMENT > 9603 Climate and Climate Change > 960307 Effects of Climate Change and Variability on Australia (excl. Social Impacts) @ 50%
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