Sedimentary responses to the Pleistocene climatic variations recorded in the South China Sea |
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Authors: | Sé bastien Boulay,Christophe Colin,Sté phane Clain,Christine Lauer-Leredde |
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Affiliation: | a Intéractions et Dynamique des Environnements de Surface, UMR IDES-CNRS 8148, Bât. 504, Université Paris-Sud, 91405 Orsay Cedex, France b Processus et Bilans des Domaines Sédimentaires, UMR PBDS-CNRS 8110, Université Lille I, 59655 Villeneuve d’Ascq, France c Mathématiques Appliquées, CNRS-UMR 6620, Université Clermont II, 63117 Aubière, France d Marine Geology, Tongji University, Shanghai 200092, People’s Republic of China e Dynamique de la Lithosphère, Université Montpellier II, 34095 Montpellier cedex 05, France |
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Abstract: | Grain-size analyses, coupled with end-member modelling, have been performed on the terrigenous fraction of two Leg 184 Ocean Drilling Program sites (1144 and 1146) from the South China Sea. The grain-size distributions over the last 1.8 Ma enable a new interpretation of their connections to sea-level variations and East Asian monsoon strength. Previous investigations in this area have associated grain-size variability with enhanced eolian input during glacial stages. End-member modelling downgrades the importance of this eolian contribution and indicates that the sediments can be described as a mixture of three end-members: fluvial mud inputs, shelf reworking and river mouth migration. Grain-size variations in the Pleistocene section of the cores indicate a multiple-stage evolution: (i) from 1.8 to 1.25 Ma, the downcore grain-size variations are low but show a correspondence between monsoon rainfall intensity and the fine grain-sized fluvial inputs; no link with sea-level variations is noticeable; (ii) from 1.25 to 0.9 Ma, there is an increase (decrease) in the intermediate (fine) end-member (∼ 100 kyr cycle) that is associated with the onset of a stronger summer monsoon and modest shelf reworking; (iii) from 0.9 to 0 Ma the grain-size record is dominated by global sea-level variations; each glacial stage is associated with extensive shelf reworking and conveyance of coarse particles to the basin. |
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Keywords: | South China Sea Grain size End-members modelling East Asian monsoon Mid-Pleistocene Transition |
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