The potential application of taphonomy-AMS 14C analysis in modelling reef island geomorphic response to climate change
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Date
2011-07-21
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Publisher
18th INQUA Congress
Abstract
The Great Barrier Reef (GBR) is the largest known reef system in the world with more than 2900 individual reefs and over 900 reef islands. As climate change progresses reef islands become increasingly vulnerable to sea-level rise, increased SST’s and ocean acidity, and more frequent tropical storms, through alterations to sediment production, transport and deposition. We focus on large benthic foraminifera, an important sediment component of reefs and reef islands globally. Using taphonomy coupled with more than 35 AMS 14C ages of individual foraminifera tests, we develop a novel approach to understanding the spatial and temporal patterns and rates of sediment production and delivery across a reef flat and how this relates to island formation and future change. Our study site was a platform reef and vegetated sand cay in the northern GBR (Raine Island, 11°35’28”S 144°02’17”E). Only four reef flat samples predate 1950 AD while all beach sediments are younger than ~1970 AD, indicating a remarkably short residence time for sediment on the reef flat. Calibrated 14C ages increase from the outer reef flat to the island consistent with the main transport pathways. At all sample sites, percent modern carbon (pMC) decreases as shell degradation increases (poorly abraded tests are ca. 10-20 yrs older than pristine tests). While the maximum residence time for foraminiferal sediment on the reef flat is in the order of 100-200 yrs, the bulk of sediment reaches the island within 10-15 yrs. These findings are of significant importance to the future stability and sustainable management of reef islands because such rapid exchange of sediment from the reef flat to the island would suggest a high degree of sensitivity to environmental change and an immediate island geomorphic response to any alteration to the reefs ability to produce sediment. Copyright (c) 2011 INQUA 18
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Keywords
Climatic change, Reefs, pH value, Sediments, Geomorphology, Carbon 14
Citation
Dawson, J. L., Hu, Q., Smithers, S. G. (2011). The potential application of taphonomy-AMS 14C analysis in modelling reef island geomorphic response to climate change. Presentation to the 18th International Union for Quaternary Research Congress, 21th-27th July 2011, Berne Switzerland.