Development of the East Asian summer monsoon: Evidence from the sediment record in the South China Sea since 8.5 Ma

Shiming Wan, Anchun Li, Peter D. Clift, Hengyi Jiang

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Abstract

128 samples from Ocean Drilling Program (ODP) Site 1143 in the southern South China Sea were analyzed for grain size, clay minerals, biogenic opal content and quartz in order to reconstruct changes in East Asian monsoon climate since 8.5 Ma. An abrupt change of terrigenous mass accumulation rate (MAR), clay mineral assemblage, median grain size and biogenic opal MAR about 5.2 Ma suggests that between 8.5-5.2 Ma the source of terrigenous sediment was mainly in the region of surface uplift and basaltic volcanism in southern Vietnam. A simple model of East Asian summer monsoon evolution was based on the clay/feldspar ratio, kaolinite/chlorite ratio and biogenic opal MAR. The summer monsoon has two periods of maximum strength at 8.5-7.6 Ma and 7.1-6.2 Ma. Subsequently, there was a relatively stable period at 6.2-3.5 Ma, continued intensification about 3.5-2.5 Ma, and gradually weakening after 2.5 Ma. Since I Ma the monsoon has intensified, with remarkable high-frequency and amplitude variability. Simultaneous increase in sedimentation rates at ODP Sites 1143, 1146 and 1148, as well as in MAR of terrigenous materials, quartz, feldspar and clay minerals at ODP Site 1143 at 3.5-2.5 Ma, may be the erosional response to both global climatic deterioration and the strengthening of the East Asian summer monsoon after about 3-4 Ma. (c) 2006 Elsevier B.V. All rights reserved.

Original languageEnglish
Pages (from-to)139-159
Number of pages21
JournalPalaeogeography Palaeoclimatology Palaeoecology
Volume241
Issue number1
Early online date25 Sep 2006
DOIs
Publication statusPublished - 1 Nov 2006

Keywords

  • East Asian monsoon
  • South China Sea
  • Tibetan Plateau
  • mineral composition
  • ODP leg 184
  • qinghai xizang plateau
  • northern hemisphere glaciation
  • stable isotope evidence
  • red clay sequence
  • Loess plateau
  • Tibetan plateau
  • late Miocene
  • Myr Ago
  • paleoclimatic interpretation
  • paleoceanographic changes

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