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Aridity in the monsoon zone as indicated by desert dune formation in the Gregory Lakes basin, northwestern Australia

2012; Taylor & Francis; Volume: 59; Issue: 4 Linguagem: Inglês

10.1080/08120099.2012.686171

1440-0952

Kathryn E. Fitzsimmons, Gifford H. Miller, Nigel A. Spooner, John W. Magee,

Geological formations and processes

Abstract Desert dunes within the monsoon-fed Gregory Lakes basin form valuable archives for Quaternary paleoenvironments, in a region where such records are scarce. Optically stimulated luminescence (OSL) chronologies from two dunes identify the timing of eolian processes, interpreted as a complex response to aridification and increased sediment availability during lake transgressions and associated fluvial activity. The earliest eolian deposition in our record occurred ca 91.5 ka, which postdates the last 'mega-lake' phase but predates a smaller lake transgression during early MIS 3. Sand plain accretion took place around ca 47 ka during contemporaneous periodic high lake levels. This was followed by intermittent linear dune building, between ca 35 and 11.5 ka, which most likely took place during an interval of relative aridity. Close spacing of mid-Holocene ages within one dune indicates rapid sediment accumulation in a single arid event ca 5 ka. At no time in the last 50 ka have lake levels reached those of the last 'mega-lake' phase prior to ca 91.5 ka, suggesting a substantially weakened present-day monsoon. KEY WORDS: Gregory LakesLake MulanGreat Sandy Desertdesert dunesOSL datingaridity ACKNOWLEDGEMENTS We would like to acknowledge the substantial input of J. M. Bowler to this paper, through initiation of the PD component of the study and collection of the dating samples from this site, in addition to critical comments on the manuscript during the drafting process. We are indebted to the generous support of the Mulan Aboriginal Community and Elders in allowing us to undertake work on their tribal lands. This work was funded by the Kimberley Land Council and Australian Institute of Aboriginal and Torres Strait Islander Studies. High-frequency dating at Gidgee Dune was undertaken by GHM and analysed by JWM, NAS and GHM, and dating at Parnkupirti Dune was undertaken by KEF. S. Pack assisted with coring at GD, including collection of the LG99-30 core. D. Questiaux and N. Hill (formerly ANU) are thanked for data analysis and sample preparation for the OSL samples analysed by GM/JWM/NAS, and E. Rhodes (UCLA) provided advice on the OSL samples for the PD dating component. The majority of this work was undertaken while KEF was a postdoctoral fellow at the Research School of Earth Sciences, ANU. GHM acknowledges sponsorship from the US National Science Foundation from the Earth System History Program under grant ATM-9709806. JWM acknowledges fellowship and research funding from the Australian Research Council. KEF thanks A. Guhl for assistance with software troubleshooting.