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Geochemical sedimentary evidence from core 973-2 for methane activity near the Jiulong methane reef in the northern South China Sea

Pan Mengdi, Wu Daidai, Yang Fei, Sun Tiantian, Wu Nengyou and Liu Lihua
Geochemical sedimentary evidence from core 973-2 for methane activity near the Jiulong methane reef in the northern South China Sea
Interpretation (Tulsa) (February 2018) 6 (1): T163-T174

Abstract

The Jiulong Methane Reef, located on the northern slope of the South China Sea, is characterized by several features, such as bottom-simulating reflections and authigenic carbonates, which are indicative of methane seeps that are currently occurring as well as those that occurred in the past. However, to date, the effect that these methane seeps have on the sedimentary environment is not completely clear. To provide further insights into the biogeochemical processes involved in methane seeps, a 6.73 m piston core (973-2) was retrieved from this area in 2011 to perform an in-depth analysis. The chronology of the core has been established by AMSC14 dating, and sedimentary events since the last glacial period have been recorded. The results indicate abnormally low abundance and diversity, as well as high infaunal percentages of benthic foraminiferal assemblages in the lower part of the core from 673 to 350 centimeters below the sea floor (cmbsf), indicating impacts from methane activities. Major elemental barium, bromine, and titanium, which serve as proxies of the paleoproductivity, organic contents, and terrestrial supply, respectively, are found to make little contribution in CaCO (sub 3) content. However, regardless of the factors mentioned above, the CaCO (sub 3) content is still higher in the lower part of core, indicating the presence of authigenic carbonates. In addition, the total organic carbon/total sulfur ratios of less than 400 cmbsf are found to be beyond the normal range, which is 2.8+ or -0.8, reflecting the effects of methane oxidation. In one of the sections, the trace metals and molybdenum profiles show enrichments that are closely related to those of the methane seeps. The results indicate that this area experienced methane seep events in the last glacial period.


ISSN: 2324-8858
EISSN: 2324-8866
Serial Title: Interpretation (Tulsa)
Serial Volume: 6
Serial Issue: 1
Title: Geochemical sedimentary evidence from core 973-2 for methane activity near the Jiulong methane reef in the northern South China Sea
Affiliation: Chinese Academy of Sciences, Guangzhou Institute of Energy Conversion, Guangzhou, China
Pages: T163-T174
Published: 201802
Text Language: English
Publisher: Society of Exploration Geophysicists, Tulsa, OK, United States
References: 77
Accession Number: 2019-006783
Categories: Geochemistry of rocks, soils, and sedimentsEconomic geology, geology of energy sources
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. strat. col., geol. sketch map
N22°00'00" - N23°00'00", E118°00'00" - E120°00'00"
Secondary Affiliation: Qingdao Institute of Marine Geology, CHN, China
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute.
Update Code: 201906
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