Distribution and isotopic composition of foraminifera at cold-seep Site 973-4 in the Dongsha area, northeastern South China Sea

A 1375-cm-long gravity core (Site 973-4) was acquired from the Dongsha cold seep area of the northeastern South China Sea (SCS). We measured its stable isotopes of planktonic foraminifera and investigated benthic foraminiferal assemblage compositions. Accelerator mass spectrometry C-14 analysis of p...

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Bibliographic Details
Published in:Journal of Asian Earth Sciences
Main Authors: Zhang, Bidong, Pan, Mengdi, Wu, Daidai, Wu, Nengyou
Format: Report
Language:English
Published: PERGAMON-ELSEVIER SCIENCE LTD 2018
Subjects:
Foraminifera
Assemblage
Stable isotopes
Cold seep
The South China Sea
ORGANIC-CARBON FLUX
LIVING BENTHIC FORAMINIFERA
DEEP-WATER PALEOCEANOGRAPHY
MODERN METHANE SEEPS
CONTINENTAL-SLOPE
COMMUNITY STRUCTURE
DISSOLVED-OXYGEN
HYDROCARBON-SEEP
ADRIATIC SEA
INDIAN-OCEAN
Geology
Geosciences
Multidisciplinary
Indian
Planktonic foraminifera
Online Access:http://ir.giec.ac.cn/handle/344007/29800
https://doi.org/10.1016/j.jseaes.2018.05.007
Description
Summary:A 1375-cm-long gravity core (Site 973-4) was acquired from the Dongsha cold seep area of the northeastern South China Sea (SCS). We measured its stable isotopes of planktonic foraminifera and investigated benthic foraminiferal assemblage compositions. Accelerator mass spectrometry C-14 analysis of planktonic foraminifera shows that some intervals are dated to Marine Isotope Stage (MIS) 3. Pulleniatina obliquiloculata has positive delta C-13 (0.25-1.25 parts per thousand) except for a negative carbon isotopic excursion (up to delta C-13 = 1.15 parts per thousand), but its light -carbon sources remain elusive. The benthic delta C-13 values (Uvigerina) of non -seep and cold-seep boreholes from the SCS have no systematic difference. Therefore, the benthic delta C-13 at Site 973-4 did not record the enhanced seepage activities (if occurred) during the last sea-level lowstand in the Dongsha area. In the pre-Holocene sediments, the foraminiferal assemblages have lower diversities, Shannon-Wiener indices, evenness indices, Simpson indices and higher calcareous proportions like typical cold-seep settings. The changes in oxygen levels (lower in the glacial period than those in the Holocene) indicated by foraminiferal indices reflect either bottom-water oxygen variations on the glacial-interglacial scale or enhanced seepage activities during the last glacial period.

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