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Sediment geochronology for bar-built estuaries subject to flood deposition and erosion: a robust multiproxy approach across an estuarine zone

Citation

Gallagher, JB and Ross, DJ, Sediment geochronology for bar-built estuaries subject to flood deposition and erosion: a robust multiproxy approach across an estuarine zone, The Holocene, 28, (3) pp. 341-353. ISSN 0959-6836 (2018) [Refereed Article]

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DOI: doi:10.1177/0959683617729441

Abstract

This paper presents a contiguous late Anthropocene 210Pb sediment geochronology and a late Anthropocene flood/fire event geochronology for an estuary subject to flood deposition and erosion. The procedure used multiple proxies to identify and evaluate flood facies overlying regions of erosion. Reconstructions of the original baseline sediments were undertaken for the major 210Pb geochronological methods. Only the lower estuary core site, which was deficient in inventory of excess 210Pb of baseline sediments, over the expected atmospheric supply for, was chosen to calculate the total amount of erosion. Erosion, as both cumulative mass and thickness, was then proportioned across flood events, relative to the size of the Rp index flood signal. The Rp index is the product of a simple stepwise thermogravimetric procedure. The flood geochronology was constructed by correlating the relative magnitudes of pivotal floods from an existing 100-year rainfall/river flow model and correlations in peak sediment char content outside of the flood facies with contemporary fire records. Overall, it was determined that 210Pb sediment isotope tomography gave the closest convergence with flood and fire events over those of the constant rate of supply and constant initial concentration methods. The agreement signified that around 40% of the original baseline accretion (25 cm) had been eroded by floods over the last 83 years and that there was possibly considerably more erosion at the upper site, which led to the loss of two flood facies.

Item Details

Item Type:Refereed Article
Keywords:Pb, geochronology, bar-built estuary, flood deposits, Little Swanport River Estuary, sediment erosion, sediment isotope tomography
Research Division:Agricultural and Veterinary Sciences
Research Group:Fisheries Sciences
Research Field:Aquaculture
Objective Division:Environment
Objective Group:Ecosystem Assessment and Management
Objective Field:Ecosystem Assessment and Management of Coastal and Estuarine Environments
UTAS Author:Ross, DJ (Dr Jeff Ross)
ID Code:128674
Year Published:2018
Deposited By:Sustainable Marine Research Collaboration
Deposited On:2018-10-05
Last Modified:2019-02-21
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