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Carbon and oxygen isotopic composition of Lower to Middle Cambrian sediments at Taijiang, Guizhou Province, China

Published online by Cambridge University Press:  15 November 2005

QING-JUN GUO
Affiliation:
State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China
HARALD STRAUSS
Affiliation:
Geologisch-Paläontologisches Institut, Westfälische Wilhelms-Universität Münster, Corrensstrasse 24, 48149 Münster, Germany
CONG-QIANG LIU
Affiliation:
State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China
YUAN-LONG ZHAO
Affiliation:
Institute of Resource and Environmental Engineering, Guizhou University of Technology, Guiyang 550002, China
DAO-HUI PI
Affiliation:
State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China
PING-QING FU
Affiliation:
State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China
LI-JUN ZHU
Affiliation:
Institute of Resource and Environmental Engineering, Guizhou University of Technology, Guiyang 550002, China
RUI-DONG YANG
Affiliation:
Institute of Resource and Environmental Engineering, Guizhou University of Technology, Guiyang 550002, China

Abstract

Secular variations in the carbon isotopic composition of organic and carbonate carbon characterize the Lower to Middle Cambrian transition that is exposed on the Yangtze Platform at Taijiang, Guizhou Province, southern China. δ13C values for organic matter range between −33.4 and −26.5‰. The carbon isotopic composition for carbonate carbon fluctuates between −2.7 and +3.1‰. A progressive decrease in the isotopic difference (Δδ) between these two isotope records reflects a decrease in the proportional contribution of bacterial biomass to the total sedimentary organic matter. In general, the observed changes are interpreted to reflect primary depositional values, notably variations in the burial rates of organic matter. These, in turn, are linked to biological changes across the Lower to Middle Cambrian transition. No distinct shift in the carbon isotopic composition marks the proposed Lower–Middle Cambrian boundary.

Type
Original Article
Copyright
© 2005 Cambridge University Press

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