Expedition 349 summary

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doi: 10.14379/iodp.proc.349.101.2015
Author(s): Li Chunfeng; Lin, Jian; Kulhanek, Denise K.; William, Trevor; Bao, Rui; Briais, Anne; Brown, Elizabeth A.; Chen Yifeng; Clift, Peter D.; Colwell, Frederick S.; Dadd, Kelsie A.; Ding Weiwei; Hernández Almeida, Iván; Huang Xiaolong; Hyun, Sangmin; Jiang Tao; Koppers, Anthony A. P.; Li Qianyu; Liu Chuanlian; Liu Qingsong; Liu Zhifei; Nagai, Renata H.; Peleo-Alampay, Alyssa; Su Xin; Sun Zhen; Tejada, Maria Luisa G.; Hai Son Trinh; Yeh, Yi-Ching; Zhang Chuanlun; Zhang Fan; Zhang Guoliang; Zhao, Xixi
International Ocean Discovery Program, Expedition 349 Scientists, College Station, TX
Author Affiliation(s): Primary:
Tongji University, Laboratory of Marine Geology, Shanghai, China
Other:
Woods Hole Oceanographic Institution, United States
Texas A&M University, United States
Lamont-Doherty Earth Observatory, United States
Swiss Federal Institute of Technology, Switzerland
University of Toulouse, France
University of Florida, United States
Chinese Academy of Sciences, Guangzhou Institute of Geochemistry, China
Louisiana State University, United States
Oregon State University, United States
Macquarie University, Australia
State Oceanic Administration, China
University of Bern, Switzerland
Korea Institute of Ocean Science and Technology, South Korea
China University of Geosciences-Wuhan, China
Chinese Academy of Sciences, Institute of Geology and Geophysics, China
Universidade de Sao Paulo, Brazil
University of the Philippines, Philippines
South China Sea Institute of Oceanology, China
Ministry of Natural Resources and Environment, Vietnam
Taiwan Ocean Research Institute, Taiwan
Chinese Academy of Sciences, Institute of Oceanology, China
University of California, Santa Cruz, United States
University of South Florida, United States
Japan Agency for Marine-Earth Science and Technology, Japan
Volume Title: Proceedings of the International Ocean Discovery Program; South China Sea tectonics; Expedition 349 of the riserless drilling platform, Hong Kong, China, to Keelung, Taiwan; Sites U1431-U1435, 26 January-30 March 2014
Volume Author(s): Li Chunfeng; Lin, Jian; Kulhanek, Denise K.; Williams, Trevor; Bao, Rui; Briais, Anne; Brown, Elizabeth A.; Chen Yifeng; Clift, Peter D.; Colwell, Frederick S.; Dadd, Kelsie A.; Ding Weiwei; Hernández Almeida, Iván; Huang Xiaolong; Hyun, Sangmin; Jiang Tao; Koppers, Anthony A. P.; Li Qianyu; Liu Chuanlian; Liu Qingsong; Liu Zhifei; Nagai, Renata H.; Peleo-Alampay, Alyssa; Su Xin; Sun Zhen; Luisa, Maria; Hai Son Trinh; Yeh, Yi-Ching; Zhang Chuanlun; Zhang Fan; Zhang Guoliang; Zhao, Xixi
Source: Proceedings of the International Ocean Discovery Program; South China Sea tectonics; Expedition 349 of the riserless drilling platform, Hong Kong, China, to Keelung, Taiwan; Sites U1431-U1435, 26 January-30 March 2014, Li Chunfeng, Jian Lin, Denise K. Kulhanek, Trevor Williams, Rui Bao, Anne Briais, Elizabeth A. Brown, Chen Yifeng, Peter D. Clift, Frederick S. Colwell, Kelsie A. Dadd, Ding Weiwei, Iván Hernández Almeida, Huang Xiaolong, Sangmin Hyun, Jiang Tao, Anthony A. P. Koppers, Li Qianyu, Liu Chuanlian, Liu Qingsong, Liu Zhifei, Renata H. Nagai, Alyssa Peleo-Alampay, Su Xin, Sun Zhen, Maria Luisa, Hai Son Trinh, Yi-Ching Yeh, Zhang Chuanlun, Zhang Fan, Zhang Guoliang and Xixi Zhao; International Ocean Discovery Program, Expedition 349 Scientists, College Station, TX. Proceedings of the International Ocean Discovery Program, Vol.349, 43p. Publisher: International Ocean Discovery Program, Washington, DC, United States. ISSN: 2377-3189 CODEN: IDSDA6
Note: In English. 104 refs.; illus., incl. sects., 1 table, geol. sketch maps
Summary: The South China Sea (SCS) provides an outstanding opportunity to better understand complex patterns of continental margin breakup and basin formation. The SCS is situated at the junction of the Eurasian, Pacific, and Indo-Australian plates and is a critical site linking some of the major western Pacific tectonic units. Despite extensive studies, sampling of basement rock and directly overlying basal sediment in the deep basin is lacking. This leaves a large margin of error in estimated ages of the SCS opening and closing, rendering various hypotheses regarding its opening mechanism and history untested. This also hampers understanding of East Asian tectonic and paleoenvironmental evolution. We drilled five sites in the deep basin of the SCS. Three of these sites (U1431, U1433, and U1434) cored into oceanic basement near the fossil spreading center. The two remaining sites (U1432 and U1435) are located proximal to the northern continent/?ocean boundary. We recovered a total of 1524 m of sediment/?sedimentary rock and 78 m of oceanic basalt and also carried out downhole geophysical logging (triple combination and Formation MicroScanner-sonic tool strings) at the two deepest sites (U1431 and U1433). These materials and data were extensively examined and discussed during the expedition and allowed us to draw the following principal conclusions on the opening of the SCS: Based on shipboard dating of microfossils in the sediment immediately above the basaltic basement and between the lava flow units, the preliminary cessation age of spreading in both the East and Southwest Subbasins is around early Miocene (16-20 Ma). Further postcruise radiometric dating of basement basalt from these sites plus additional calibration of magnetic anomaly models and paleomagnetic measurements will further refine the age range. Overall, a large difference is not apparent in the terminal ages of seafloor spreading between the two subbasins. At Site U1435, we were able to drill into a structural high standing along the continent/?ocean boundary. Coring at this site recovered a sharp unconformity at ∼33 Ma, above which is marine sediment and below which are poorly sorted sandstone and black mudstone, interpreted as littoral deposits. Environmental interpretation will require further shore-based studies because the sequence is almost entirely barren of marine microfossils. Nevertheless, we interpret this unconformity to be likely directly related to the continental breakup during the initial opening of the SCS. The onset of seafloor spreading is therefore estimated to be at ∼33 Ma. All sites contain deep marine deposits but show significant areal variations in postspreading sedimentary environment and provenance. Site U1431 records evidence for deep-marine turbidite deposition from terrestrial sources. The observed coarser silt turbidites may have a source in Taiwan or other surrounding blocks, whereas interbedded calcareous turbidites at this site could be transported from local sources, such as nearby seamounts topped by carbonate platforms. In contrast, the source for upper Miocene clay and silt turbidites at Site U1433 could be Borneo or mainland Southeast Asia, with the source of the interbedded carbonate turbidites likely the Dangerous Grounds or Reed Bank area located south of the site. Sites U1431 and U1434 are close to seamounts developed along the relict spreading center.
Year of Publication: 2014
Research Program: IODP Integrated Ocean Drilling Program
IODP2 International Ocean Discovery Program
Key Words: 07 Marine Geology and Oceanography; Basalts; Basement; Boreholes; Cenozoic; Cores; Crust; Expedition 349; Geophysical methods; Geophysical profiles; Geophysical surveys; IODP Site U1431; IODP Site U1432; IODP Site U1433; IODP Site U1434; IODP Site U1435; Igneous rocks; International Ocean Discovery Program; Lithostratigraphy; Marine geology; Marine sediments; North Pacific; Northwest Pacific; Oceanic crust; Pacific Ocean; Physical properties; Plate tectonics; Sea-floor spreading; Sedimentary rocks; Sediments; Seismic methods; Seismic profiles; Seismic stratigraphy; South China Sea; Surveys; Volcanic rocks; Well logs; West Pacific
Coordinates: N125500 N183400 E1170100 E1145500
Record ID: 2015041865
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute.
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