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

• Published in: Geological magazine Vol. 142; no. 6; pp. 723 - 733
• Main Authors: GUO, QING-JUN, STRAUSS, HARALD, LIU, CONG-QIANG, ZHAO, YUAN-LONG, PI, DAO-HUI, FU, PING-QING, ZHU, LI-JUN, YANG, RUI-DONG
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 01.11.2005
• Subjects: Arthropoda; Asia; Balang China; Balang Formation; Bianchong Formation; biozones; C-13/C-12; Cambrian; Carbon; carbon and oxygen isotopic composition; chemical composition; chemostratigraphic correlation; chemostratigraphy; China; correlation; diagenesis; Doushantuo Formation; Far East; geochemistry; Geology; Guizhou China; Invertebrata; isotope ratios; Isotopes; Jialao Formation; Kaili Formation; Loushanguan Formation; Lower–Middle Cambrian; microfossils; Neoproterozoic; Niutitang Formation; O-18/O-16; organic carbon; organic compounds; Organic matter; Original Article; Oxygen; paleoenvironment; Paleozoic; palynomorphs; Precambrian; Proterozoic; Qingxudong Formation; sedimentary organic matter; sedimentary rocks; Sediments; Sinian; stable isotopes; stratigraphic boundary; Stratigraphy; Taijiang China; Trilobita; Trilobitomorpha; upper Precambrian; Yangtze Platform; China; Guizhou China; China, People's Rep., Yangtze Platform; China, People's Rep., Guizhou Prov; carbon and oxygen isotopic composition; sedimentary organic matter; chemostratigraphic correlation; Lower–Middle Cambrian; China
• ISSN: 0016-7568; 1469-5081
• DOI: 10.1017/S0016756805001202

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.