Abstract


IRREGULAR PLEISTOCENE PLATFORM BENEATH HERON REEF SOUTHERN GREAT BARRIER REEF

The geological record of fossil reefs provides essential information for interpreting palaeo-climatic change during the Holocene. Environmental influences on reef-building corals, such as variations in sea-level and sea-surface temperature, may cause significant differences in reef development and evolution. However, the early development of Holocene reefs is still poorly known. New drilling in the southern Great Barrier Reef is providing insights on classic reef models and relationships between Holocene reefs and Pleistocene antecedent topography. Five new cores collected in 2014 on the windward margin of Heron Reef suggest a much more irregular underlying topography than expected. Cores were recovered to depths of 30 m with new U-series ages constraining growth between 8472±24 and 2287±16 years. One core penetrated Pleistocene basement at ~ 15.3 m with Holocene reef growth initiated by ~ 8.4 ka. However, 1.77 km west along the same margin, four cores failed to penetrate Pleistocene basement at depths of 19.6, 19.7, 24 and 30 m respectively, suggesting that the margin at that location overlies a karst valley or alternatively, there is no local antecedent platform there. A 48 m-long margin-perpendicular transect involving three cores shows that the topographic low is filled by a prograding succession, in places at least 30 m thick, beneath the current reef margin. These findings provide new insights into relationships between antecedent topography and subsequent reef growth and Holocene carbonate production and retention rates.

Authors

Salas-Saavedra, M. E., University of Queensland, Australia, marcos.salassaavedra@uq.net.au

Dechnik, B., University of Sydney , Australia

Webb, G. E., University of Queensland, Australia

Webster, J. M., University of Sydney , Australia

Zhao, J. X., University of Queensland, Australia

Nothdurft, L. D., Queensland University of Technology , Australia

Clarck, T. R., University of Queensland, Australia

Graham, T., Geocoastal Group, Australia

Braga, J. C., Universidad de Granada, Spain

Details

Oral presentation

Session #:34
Date: 06/23/2016
Time: 15:00
Location: 311

Presentation is given by student: Yes