Ages and magnetic structures of the South China Sea constrained by deep tow magnetic surveys and IODP Expedition 349

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doi: 10.1002/2014GC005567
Author(s): Li Chunfeng; Xu Xing; Lin, Jian; Sun Zhen; Zhu, Jian; Yao Yongjian; Zhao Xixi; Liu Qingsong; Kulhanek, Denise K.; Wang Jian; Song Taoran; Zhao Junfeng; Qiu Ning; Guan Yongxian; Zhou Zhiyuan; 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 Zhifei; Nagai, Renata H.; Peleo-Alampay, Alyssa; Su Xin; Tejada, Maria Luisa G.; Trinh Hai Son; Yeh Yiching; Zhang Chuanlun; Zhang, Fan; Zhang, Guoliang
Author Affiliation(s): Primary:
Tongji University, Laboratory of Marine Geology, Shanghai, China
Other:
Guangzhou Marine Geological Survey, China
Woods Hole Oceanographic Institution, United States
Chinese Academy of Sciences, China
Texas A&M University, United States
Lamont-Doherty Earth Observatory, United States
Swiss Federal Institute of Technology, Switzerland
University of Toulouse, France
University of South Florida, United States
Louisiana State University, United States
Oregon State University, United States
Macquarie University, Australia
University of Bern, Switzerland
Korea Institute of Ocean Science and Technology, South Korea
China University of Geosciences, China
Tongji University, China
Universidade de Sao Paulo, Brazil
University of the Philippines, Philippines
Japan Agency for Marine-Earth Science and Technology, Japan
Ministry of Natural Resources and Environment, Vietnam
Taiwan Ocean Research Institute, Taiwan
Volume Title: Geochemistry, Geophysics, Geosystems - G<sup>3</sup>
Source: Geochemistry, Geophysics, Geosystems - G>3`, 15(12), p.4958-4983. Publisher: American Geophysical Union and The Geochemical Society, United States. ISSN: 1525-2027
Note: In English; illus., incl. 3 tables, sketch map
Summary: Combined analyses of deep tow magnetic anomalies and International Ocean Discovery Program Expedition 349 cores show that initial seafloor spreading started around 33 Ma in the northeastern South China Sea (SCS), but varied slightly by 1-2 Myr along the northern continent-ocean boundary (COB). A southward ridge jump of ∼20 km occurred around 23.6 Ma in the East Subbasin; this timing also slightly varied along the ridge and was coeval to the onset of seafloor spreading in the Southwest Subbasin, which propagated for about 400 km southwestward from ∼23.6 to ∼21.5 Ma. The terminal age of seafloor spreading is ∼15 Ma in the East Subbasin and ∼16 Ma in the Southwest Subbasin. The full spreading rate in the East Subbasin varied largely from ∼20 to ∼80 km/Myr, but mostly decreased with time except for the period between ∼26.0 Ma and the ridge jump (∼23.6 Ma), within which the rate was the fastest at ∼70 km/Myr on average. The spreading rates are not correlated, in most cases, to magnetic anomaly amplitudes that reflect basement magnetization contrasts. Shipboard magnetic measurements reveal at least one magnetic reversal in the top 100 m of basaltic layers, in addition to large vertical intensity variations. These complexities are caused by late-stage lava flows that are magnetized in a different polarity from the primary basaltic layer emplaced during the main phase of crustal accretion. Deep tow magnetic modeling also reveals this smearing in basement magnetizations by incorporating a contamination coefficient of 0.5, which partly alleviates the problem of assuming a magnetic blocking model of constant thickness and uniform magnetization. The primary contribution to magnetic anomalies of the SCS is not in the top 100 m of the igneous basement. Abstract Copyright (2014), . American Geophysical Union. All Rights Reserved.
Year of Publication: 2014
Research Program: IODP Integrated Ocean Drilling Program
IODP2 International Ocean Discovery Program
ODP Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; 20 Geophysics, Applied; Expedition 349; Geophysical methods; Geophysical surveys; IODP Site U1433; IODP Site U1434; IODP Site U1435; International Ocean Discovery Program; Leg 184; Magnetic methods; Marine methods; North Pacific; Northwest Pacific; ODP Site 1145; ODP Site 1146; ODP Site 1148; Ocean Drilling Program; Ocean floors; Pacific Ocean; South China Sea; Surveys; West Pacific
Coordinates: N120000 N200000 E1200000 E1120000
Record ID: 2016077716
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom, Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union