Middle to late Holocene initiation of the annual flood pulse in Tonle Sap Lake,Cambodia |
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| Authors: | Mary Beth Day David A Hodell Mark Brenner Jason H Curtis George D Kamenov Thomas P Guilderson Larry C Peterson William F Kenney Alan L Kolata |
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| Institution: | (1) Department of Geological Sciences, University of Florida, Gainesville, FL 32611-2120, USA;(2) Godwin Laboratory for Palaeoclimate Research, Department of Earth Sciences, University of Cambridge, Cambridge, CB2 3EQ, UK;(3) Department of Geological Sciences and Land Use and Environmental Change Institute, University of Florida, Gainesville, FL 32611-2120, USA;(4) Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA, USA;(5) Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL, USA;(6) Department of Anthropology, University of Chicago, Chicago, IL, USA;(7) Present address: Department of Earth Sciences, University of Cambridge, Cambridge, CB2 3EQ, UK |
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| Abstract: | Tonle Sap Lake, Cambodia, possesses one of the most productive inland fisheries in the world and is a vital natural resource
for the country. The lake is connected to the Mekong River via the Tonle Sap River. Flow in the Tonle Sap River reverses seasonally,
with water exiting the lake in the dry season and entering the lake during the summer monsoon. This flood pulse drives the
lake’s biological productivity. We used Sr, Nd, and Pb isotopes and elemental concentrations in lake sediment cores to track
changes in the provenance of deposits in Tonle Sap Lake. We sought to determine when the lake first began to receive water
and sediment input via the Mekong River, which initiated flood pulse processes. The transition from a non-pulsing lake to
the Mekong-connected system is marked by shifts to values of 87Sr/86Sr, εNd, and 207Pb/204Pb that are characteristic of Mekong River sediments. In addition, magnetic susceptibility increased and sediment elemental
composition changed. Elemental (P) measures point to enhanced phosphorus loading and C/N and isotope ratios of bulk organic
matter indicate a shift to greater relative contribution of organic material from aquatic versus terrestrial environments,
coinciding with the initiation of flood pulse processes. On the basis of radiocarbon dating in two cores, we estimate the
initiation of the annual flood pulse occurred between ~4,450 and 3,910 cal year BP. |
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