Development of the Great Barrier Reef from the last glacial maximum to present
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Date
2022-12-06
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Publisher
Australasian Quaternary Association Inc.
Abstract
The Great Barrier Reef (GBR) is located on the north-eastern continental margin of the Australian continent and is the largest tropical coral reef system in the world. Reefs are known to form on the continental shelf during interglacial sea level highstands and are exposed and die during glacial sea level lowstands. However, sonar and drilling studies have shown a series of backstepping fossilreefs migrated across the shelf edge during sea level transgression prior to the onset of the modern GBR at approximately 9 ka. While cores drilled through reefs provide direct evidence of reef growth and composition at a fixed point, such cores are often temporally discontinuous. By contrast, distal marine sediment cores can provide a more continuous time series of the development of both reefs and sedimentary processes along the margin. This study focussed on the analysis of piston cores (FR4/92-11 and FR4/92-12) collected from the Queensland Trough. The cores were subsampled at regular intervals for elemental (XRF) and mineralogical (XRD) analyses, and planktic foraminifera (Globigerinoides ruber) for oxygen isotope measurements and radiocarbon dating. A principal component analysis revealed four phases (‘clusters’) of development of the GBR margin from the Last Glacial Maximum to present. These represent 1) primarily hemipelagic carbonate sediments deposited during the glacial sea level lowstand, 2) mid-deglaciation sedimentation dominated by High Mg Calcite as sea level transgression and slope fossil-reefs initiated, 3) late deglaciation (11.8-8 ka) sedimentation dominated by a pronounced spike in terrigenous accumulation as sea level transgression reached the shelf break and 4) reef sedimentation dominated by Sr-rich aragonite in the early to late Holocene. Changes in carbonate mineralogy likely reflect differences in the terrigenous sediment flux and reef assemblages (dominance of corals versus crustose coralline algae and microbialite) between the fossil-reefs and the modern reef system.
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Keywords
Coral reefs, Sea level, Foraminifera, Oxygen isotopes, Sediments, Carbon 14, Algae, Buildup, Queensland
Citation
Husdell, M., Dunbar, G., Bostock, H., Webster, J., & Hua, Q. (2022). Development of the Great Barrier Reef from the last glacial maximum to present. Paper presented to the AQUA 2022 Conference, 6-8th December, Adelaide (pp. 151-152). Retrieved from: https://aqua.org.au/conference/aqua-2022/aqua-2022-conference-program-and-abstracts/