摘要
对扬子地台湘黔地区早寒武世黑色页岩有机碳同位素的组成变化进行野外地质观察与室内分析研究表明:研究区灯影组白云岩主要为碳酸盐台地沉积环境,牛蹄塘组黑色页岩主要为陆棚沉积环境,湖南地区有可能水体更深,过渡到斜坡相沉积区。通过分析,湘黔地区黑色页岩有机碳含量(TOC)为0.05%~12.31%,平均为4.97%。有机碳同位素(1δ3Corg)组成的变化幅度很大,从-29.49‰^-34.41‰(PDB),平均为-31.78‰,最大偏移量为4.3‰。牛蹄塘组黑色页岩的1δ3Corg和TOC含量变化也很大,具有明显的3个升降旋回,代表海平面具有海进海退变化特征。而下伏地层灯影组白云岩1δ3Corg值相对比较高,代表海平面下降。研究区两个典型剖面的有机碳同位素变化曲线反映了该期海平面变化,海洋原始生产率以及上涌洋流的变化情况,揭示湘黔地区早寒武世的古海洋信息。
This paper mainly demenstrated the composition of organic carbon isotope of Early Cambrian black shales from the ＂Xiang-Qian＂ area, Yangtze Platform. Detailed study showed that the Dengying Formation dolomites of Late Sinian were deposited in carbonate platform environ ment, whereas the Niutitang Formation black shales of Early Cambrian in continental shelf facies. In Ganziping area, Hunan Province, the water may be deeper than that in Songlin area, Guizhou, and perhaps it was transited into slope facies. Organic carbon contents （TOC/%） rang from 0.05% to 12.31% with an average of about 4. 97%. The organic carbon isotopic values （δ^13Corg） fluctuate sharply from -29.49‰ to --34.41‰ PDB with a mean value of -31.78‰ PDB,showing a negative excursion close to 4. 3‰. In Niutitang Formation black shales, the changes of δ^13Corg values and TOC contents are more obvious than those in Dengying Formation dolomites of Late Sinian. They show three remarkable fluctuation in the whole profiles, which indicates that the sea-level changes were in the transgression or regression. In Late Sinian, the δ^13Corg values of the dolomites are slightly higher than those in Early Cambrian black shales,show ing the desecent of sea level. The carbon isotope curves exhibit the changes of sea level, primary productivity and rise oceanic currents, therefore, this study provides some significant information about Early Cambrian palaeocean in south China.
出处
《矿物岩石》
CAS
CSCD
北大核心
2006年第1期81-85,共5页
Mineralogy and Petrology
基金
中科院"百人计划"
关键词
早寒武世
黑色页岩
有机碳同住素
古海洋
湘黔地区
Early Cambrian,black shales
organic carbon isotope
palaeocean
Xiang-Qian area
