We found a match
Your institution may have rights to this item. Sign in to continue.
- Title
Carbon and sulfur isotopic compositions of Early Cambrian black shales, NW Hunan, China: Implications for the Paleoceanographic sedimentary environment.
- Authors
Ma, Dongsheng; Cao, Shuanglin; Pan, Jiayong; Xia, Fei; Yao, Chunyan; Ding, Haifeng
- Abstract
In order to better understand the paleoceanographic sedimentary environment of the Lower Cambrian black shales extensively distributed in South China, outcropped along the present southern margin of the Yangtze Platform with a width of ca. 200-400 km and a length of more than 1500 km, we present new paired δC data on carbonates (δC) and associated organic carbon (δC) and δS data on sedimentary pyrite in black shales from three sections (Ganziping, Shancha and Xiaohekou) located in NW Hunan, China. In these sections, a total of 82 Lower Cambrian black shale samples have δC values ranging from −4.0‰ to 1.7‰ with an average value of −2.1‰, and δCorg values between −34.9‰ and −28.8‰, averaging −31.9‰. The δS values of 16 separated sedimentary pyrite samples from the black shales vary between +10.2‰ and +28.7‰ with an average value of +19.5‰, presenting a small isotope fractionation between seawater sulfate and sedimentary sulfide. The model calculation based on credible data from the paired analyses for δC and δC of 11 black shale samples shows a high CO concentration in the Early Cambrian atmosphere, about 20 times higher than pre-industrial revolution values, consistent with previous global predictions. The small sulfur isotope fractionation between seawater sulfate and sedimentary sulfide in black shales, only 15.5‰ on average, implies a low sulfate level in the Early Cambrian seawater around 1 mmol. In combination with a high degree of pyritization (DOP) in the black shales, it is suggested that sulfidic deep-ocean water could have lingered up to the earliest Cambrian in this area. The black shale deposition is envisaged in a stratified marine basin, with a surface euphotic and oxygenated water layer and sulfidic deeper water, controlled by a continental margin rift.
- Subjects
HUNAN Sheng (China); CHINA; BLACK shales; CARBON isotopes; SULFUR isotopes; CAMBRIAN stratigraphic geology; PALEOCEANOGRAPHY; SEDIMENTARY rocks; TRACE elements
- Publication
Chinese Journal of Geochemistry, 2011, Vol 30, Issue 3, p332
- ISSN
1000-9426
- Publication type
Article
- DOI
10.1007/s11631-011-0517-3