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Title: Monsoon dominated climate, chemical weathering and anthropogenic processes in the Halocene of Southern China and Taiwan
Author: Hu, Dengke
ISNI:       0000 0004 2739 9277
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2013
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Sedimentary cores from northern margin of the South China Sea have been studied to monitor the intensity of physical erosion and chemical weathering associated with the regional monsoonal climates during the Holocene. The tectonically quiescent Pearl River preserved an over 10-meter-thick continuous deposit in its delta, while ODP Site 1144 on the northern slope has captured sediment that has been dominantly discharged by mountainous rivers on the Taiwan island, which are situated in an active tectonic setting. Geochemical, mineralogical and isotopic analyses were performed on the cores at resolution equivalent to decadal years. Reconstructed weathering records in general show coherence with the speleothem rainfall records however with different variation patterns. Since the Early-Holocene climate optimum, chemical weathering remained strong until~5.5 ka in the Pearl River, while ODP Site 1144 only captured a short period of chemical weathering which predates 8 ka. Humidity indicator hematite/goethite, indicative of dry conditions at that time, suggests that the slope deposition was reworked, i.e. sediment that had been strongly weathered during glacial times on the Taiwan Strait was eroded to the slope by strong monsoon rains until the region was submerged by rising sea levels after ~8 ka which finally truncated the sediment supply. In the Pearl River delta, strongly weathered sediment from last glacial is also seen underlying the Holocene sediment. Data from the post-9.5 ka section of this site show a clear trend of more altered sediment correlating with a stronger monsoon. Again, enhanced reworking of fluvial terrace deposits is believed to be the cause of this chemical perturbation. After ~2500 years ago, sediment in Pearl River delta shows a marked rise of weathering intensity towards the highest level measured from modern river basin, despite a slightly strengthened monsoon. This change was most likely driven by human settlement and erosion of older weathered soils following the initiation of agriculture in the river basin.
Supervisor: Not available Sponsor: Swire Educational Trust ; South China Sea Institute of Oceanology
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available