Comminution dating of glacio-marine sediments in A.. (ComAnt)
Comminution dating of glacio-marine sediments in Antarctica and the Southern Ocean
Date du début: 1 sept. 2013,
Date de fin: 31 août 2017
The geological and climatic history of Antarctica during the Late Quaternary is to a large extent unknown due to the Antarctic Ice Sheet (AIS) cover that limits observations on land, yet this information can be retrieved from the study of the provenance and transport times of terrigenous material in marine sediment cores surrounding the continent, which can be used to reconstruct the history of continental weathering and sediment transport mechanisms and timescales.Here, I propose to implement a novel approach termed “comminution dating”, to determine spatial and temporal changes in the transport time of fine clastic sediments produced by Antarctic subglacial erosion during the Late Quaternary, which is connected to the flux of ice and sediment discharge into the Southern Ocean.I will focus on U-series disequilibrium in detrital material, which is a measure of weathering and transport time. The time elapsed since the initial grinding of the bedrock by glacial abrasion that produces rock flour, including the transport process and age of deposition, is defined as the “comminution age” of the sediment, and is determined by the relative degree of 234U-depletion in the samples.The proposed study builds on exciting new results from the Weddell Sea, where comminution ages and provenance of different grain size fractions of terrigenous material indicate that sediment transport times ranged between tens to hundreds of kyrs and varied on glacial-interglacial timescales. I will study the comminution ages of a large number of glacio-marine deposits at sites throughout the Southern Ocean, and further conduct a comprehensive study of natural and analytical biases on the comminution dating approach. The results will yield a transformative data set that will provide new insights into the history of glacial weathering in Antarctica during the Late Quaternary, ocean current histories in the Southern Ocean and their combined role in modulating global climate change patterns.
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