South China Sea tectonics and magnetics; constraints from IODP Expedition 349 and deep-tow magnetic surveys

Author(s): Lin, J.; Li, C. F.; Kulhanek, D. K.; Zhao, X.; Liu, Q.; Xu, X.; Sun, Z.; Zhu, J.
Author Affiliation(s): Primary:
Woods Hole Oceanographic Institute, Woods Hole, MA, United States
Other:
Tongji University, China
International Ocean Discovery Program, United States
University of California, Santa Cruz, United States
Chinese Academy of Sciences, Institute of Geology and Geophysics, China
Guangzhou Marine Geological Survey, China
Chinese Acaademy of Sciences, South China Sea Institute of Oceanology, China
Volume Title: AGU 2014 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2014; American Geophysical Union 2014 fall meeting, San Francisco, CA, Dec. 15-19, 2014. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: The South China Sea (SCS) is the largest low-latitude marginal sea in the world. Its formation and evolution are linked to the complex continental-oceanic tectonic interaction of the Eurasian, Pacific, and Indo-Australian plates. Despite its relatively small size and short history, the SCS has undergone nearly a complete Wilson cycle from continental break-up to seafloor spreading to subduction. In January-March 2014, Expedition 349 of the International Ocean Discovery Program (IODP) drilled five sites in the deep basin of the SCS. Three sites (U1431, U1433, and U1434) cored into oceanic basement near the fossil spreading center on the East and Southwest Subbasins, whereas Sites U1432 and U1435 are located near the northern continent/ocean boundary of the East Subbasin. Shipboard biostratigraphy based on microfossils preserved in sediment directly above or within basement suggests that the preliminary cessation age of spreading in both the East and Southwest Subbasins is around early Miocene (16-20 Ma); however, post-cruise radiometric dating is being conducted to directly date the basement basalt in these subbasins. Prior to the IODP drilling, high-resolution near-seafloor magnetic surveys were conducted in 2012 and 2013 in the SCS with survey lines passing near the five IODP drilling sites. The deep-tow surveys revealed detailed patterns of the SCS magnetic anomalies with amplitude and spatial resolutions several times better than that of traditional sea surface measurements. Preliminary results reveal several episodes of magnetic reversal events that were not recognized by sea surface measurements. Together the IODP drilling and deep-tow magnetic surveys provide critical constraints for investigating the processes of seafloor spreading in the SCS and evolution of a mid-ocean ridge from active spreading to termination.
Year of Publication: 2014
Research Program: IODP Integrated Ocean Drilling Program
IODP2 International Ocean Discovery Program
Key Words: 07 Marine Geology and Oceanography; East Pacific; Expedition 320; Expedition 349; Expeditions 320/321; Geophysical methods; Geophysical surveys; IODP Site U1334; IODP Site U1431; IODP Site U1433; Integrated Ocean Drilling Program; International Ocean Discovery Program; Magnetic methods; North Pacific; Northeast Pacific; Northwest Pacific; Pacific Ocean; South China Sea; Surveys; Tectonics; West Pacific
Coordinates: N080000 N080000 W1315824 W1315824
N152232 N152233 E1170001 E1165959
N125508 N125508 E1150251 E1150250
Record ID: 2015087609
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