Calcification depths and temperatures of planktonic foraminifera off southwest Hainan Island and their paleoceanographic implications

The East Asian monsoon system influences the local oceanographic and climatic conditions of South China Sea (SCS), making the habitat depths of planktonic foraminifera (PF) specific for this region. The previous paleo-ocean reconstructions of SCS have been based on calcification habitat depths deriv...

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Bibliographic Details
Published in:Marine Micropaleontology
Main Authors: Ladigbolu, Ismail Adejare, Li, Hongliang, Li, Baohua （李保华）, Wiesner, Martin G., Zhang, Jingjing, Sun, Lin, Ran, Lihua, Lu, Shaolei, Ye, Ying, Chen, Jianfang
Format: Report
Language:English
Published: ELSEVIER 2020
Subjects:
East Asian monsoon
Planktonic foraminifera
Apparent calcification depth
Thermal gradients
Stable isotopes
South China Sea
OXYGEN ISOTOPIC COMPOSITION
GLOBIGERINOIDES-SACCULIFER BRADY
CHINA SEA
VERTICAL-DISTRIBUTION
SEASONAL-VARIATIONS
STABLE-ISOTOPES
CARBON-ISOTOPE
SEDIMENT TRAPS
ASIAN MONSOON
PANAMA BASIN
Paleontology
Online Access:http://ir.nigpas.ac.cn/handle/332004/32130
http://ir.nigpas.ac.cn/handle/332004/32131
https://doi.org/10.1016/j.marmicro.2020.101878
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Summary:The East Asian monsoon system influences the local oceanographic and climatic conditions of South China Sea (SCS), making the habitat depths of planktonic foraminifera (PF) specific for this region. The previous paleo-ocean reconstructions of SCS have been based on calcification habitat depths derived from other oceans, which may have affected the accuracy of interpretations. In this study, the calcification depths of Globigerinoides ruber, Globigerinoides sacculifer, and Neogloboquadrina dutertrei from sediment traps deployed at 1000 m depth off southwest Hainan Island from July 2012 to April 2013 were analyzed with regard to the stable isotopes of oxygen (delta O-18) and carbon (delta C-13) to calculate their regional apparent calcification depths (ACDs) with the overall aim to improve the reconstruction of the upper ocean thermal structure. ACDs and temperature estimated from foraminifera delta O-18 ranged from 0 to 42 m and 25 degrees C for G. ruber, 30-65 m and 23.3 degrees C for G. sacculifer, and 75-100 m and 20.3 degrees C for N. dutertrei, respectively. The difference between the thermocline-species (N. dutertrei) and mixed-layer species (G. ruber and G. sacculifer) delta O-18 (Delta delta O-18(Th-ML)) and the temperature (Delta T) shows water column stratification. The periods of lower and higher Delta T and Delta delta O-18 were in phase with the changes in regional overlying wind speed. Additionally, this study reveals that N. dutertrei lives and calcifies its shells within the base of the mixed-layer depth (MLD) and upper thermocline depth in SCS. Overall, the results from this study provide a new insight to understand the mixed-layer and thermocline depth in the northern SCS.

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