Occurrence of Quaternary turbidite deposits in the central South China Sea; response to global sea-level changes

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Author(s): Liu Zhifei; Zhang Xiaodong; Christophe, Colin; Peleo-Alampay, A.; Guballa, Jose Dominick S.; Li Pingyuan; Liu Chuanlian
Author Affiliation(s): Primary:
Tongji University, State Key Laboratory of Marine Geology, Shanghai, China
University of Paris-Sud, Orsay, France
University of the Philippines, Diliman, Philippines
Volume Title: AGU 2016 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2016; American Geophysical Union 2016 fall meeting, San Francisco, CA, Dec. 12-16, 2016. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Terrigenous turbidite layers frequently occur at the upper 150-m-thick sedimentary sequence of Hole U1431D (15°22.54'N, 117 °00.00'E, 4240.5 m water depth), International Ocean Discovery Program (IODP) Expedition 349, near the relict spreading ridge in the central South China Sea. This study implies visual statistics combined with grain size, clay mineralogy, and Nd-Sr isotope analyses to reconstruct the occurrence of these turbidite layers. The age-model of combined calcareous nannofossils, planktonic foraminifers, and paleomagnetism suggests that the sedimentary sequence spans the entire Quaternary with an age of ≈2.6 Ma at the depth of 150 mcd below the seafloor. Our results show that the turbidite deposits are dominated by silt with sandy silt and silty clay, poorly sorted, and grading upward with erosion base. The occurrence of turbidite layers are highly frequent with about 3.06 layers per meter and an average thickness of 14.64 cm per layer above 96 mcd (≈1.6 Ma), while the lower part turbidite layers are less frequently developed with 1.16 layers per meter and an average thickness of 5.67 cm. Provenance analysis indicates that Taiwan, about 900 km northward to the studied site, is the major source for these terrigenous sediments, implying the long run-out turbidity current activity over the very low-gradient deep-sea plain of the South China Sea. The frequency of the turbidite layer occurrence is well correlated to the Quaternary global sea-level change history, with the high frequency occurred during the lower sea-level stands. Our study suggests that the glacial-interglacial-scale sea-level change has controlled terrigenous sediment input from Taiwan and the northern shelf of the South China Sea during the Quaternary. The increase of turbidite layer frequency since ≈1.6 Ma in the central South China Sea could be triggered by the enlarged amplitude of sea-level change.
Year of Publication: 2016
Research Program: IODP2 International Ocean Discovery Program
Key Words: 24 Surficial Geology, Quaternary Geology; Cenozoic; Expedition 349; International Ocean Discovery Program; North Pacific; Northwest Pacific; Pacific Ocean; Quaternary; Sea-level changes; South China Sea; Turbidite; West Pacific
Coordinates: N125500 N183400 E1170100 E1145500
Record ID: 2017102569
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