贵州瓮安陡山沱组磷块岩生物标志物特征及对沉积环境的指示

摘要

The fossil assemblages of the Wengan biotas identified in the phosphorites from the Neoproterozoic Doushantuo Formation in Wengan, Guizhou consist of multicelluar algae, cyanobacteria, Acritarchs, dormant eggs and embryos of metazoas, tabular metazoas and bilateral metazoas and so on. The organic geochemical analysis of the phosphorite samples collected from the Doushantuo Formation in Wengan has disclosed that the hydrocarbon fractions contain n-alkanes, terpanes, steranes, and isoprenoid hydrocarbons. The distribution of n-alkanes displays the highest peak of nC21, and a wide range of carbon atom numbers. The OEP value equals to 1.03, and the Pr/Ph ratio equals to 0.95, indicating the phytane dominance. The sterane contents of C27＞C29＞C28 shows the distribution of asymmetrical "V" shape. The dominance of C27 may be caused by abundant acritarchs. The biomarkers cited above indicate that the organisms in the phosphorites are mostly derived from algae and bacteria. Some of the biomarkers also suggest the reducing and high-salinity sedimentary environments of phosphorites.%贵州瓮安新元古界陡山沱组磷块岩中发现的瓮安生物群主要包括多细胞藻类、蓝菌、疑源类、后生动物休眠卵及胚胎、管状后生动物和两侧对称的后生动物等化石类型.对瓮安陡山沱组磷块岩的有机地球化学分析表明,烃类有机组分包括正构烷烃、萜类、甾类和类异戊二烯烃.正构烷烃主峰为C21,碳数分布范围宽;OEP值为1.03,接近1.Pr/Ph比值为0.95,植烷略显优势.规则甾烷呈不对称的"V"字形分布,表现为C27＞C29＞C28的分布特征.C27占优势可能是由大量的带刺疑源类所致.生物标志物特征指示瓮安陡山沱组磷块岩中的有机物来源于藻类和细菌,显示还原性、较高盐度的成磷沉积环境.