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Enregistrements sédimentaires des variations de la mousson sud-est asiatique au cours des 2 derniers millions d'années

Abstract : The aim of this work was the study of the impact of the South-East Asian monsoon on the South China Sea (SCS) sedimentary record along the last 2 Ma. The terrigenous fraction of 3 ODP Sites (Leg 184 - Sites 1144, 1145 and 1146) located in the northern part of the SCS, was investigated in terms of sedimentology, mineralogy and geochemistry. X-ray diffraction (XRD) associated with isotopic geochemistry (Rb/Sr and Sm/Nd) allows us to identify the sources of the sediment. The fine fraction (<2µm) comes mainly from the Pearl River with, however, some important inputs (3 to 15% of the <2µm fraction) of smectite from the Luzon volcanic arc when the summer monsoon strengthens (23ka cycles). The grain-size analyses allows us to characterize the sedimentary dynamic by identifying 3 granulometric populations, varying separately along the record et showing grain-size increases during the glacial stages. These variations are attributed to the shelf reworking during the sea level variations. These results are in contradictions with the previous hypothesis, which linked the grain-size increases to eolian inputs associated with enhanced winter monsoon winds. During the last 2 Ma, the summer monsoon intensity shows 3 major periods of variations : 2-1,2 Ma : low amplitude oscillations linked with the high latitude insolation (41ka). 1,2-0,9 Ma : intensification associated with the decrease of the global oceanic circulation strength and the closing of the indonesian thresholds. 0,9-0 Ma : gradual decrease linked with the global cooling of the climate.
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https://tel.archives-ouvertes.fr/tel-00006427
Contributor : Sébastien Boulay <>
Submitted on : Thursday, July 8, 2004 - 3:39:22 PM
Last modification on : Wednesday, September 16, 2020 - 4:53:45 PM
Long-term archiving on: : Friday, April 2, 2010 - 8:40:29 PM

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Sébastien Boulay. Enregistrements sédimentaires des variations de la mousson sud-est asiatique au cours des 2 derniers millions d'années. Minéralogie. Université Paris Sud - Paris XI, 2003. Français. ⟨tel-00006427⟩

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