Origin of organic matter and depositional characteristics of early Cambrian Niutitang Formation from South China: New insights using molecular fossils. Issue 1 (21st September 2022)

• Record Type: Journal Article
• Authors: Awan, Rizwan Sarwar; Liu, Chenglin; Feng, Dehao; Zang, Qibiao; Wu, Yuping; Ali, Sajjad
• Is Part Of: Geological journal. Volume 58:Issue 1(2023)
• Page Start: 298
• Page End: 314
• Publication Date: 2022-09-21
• Subjects: Cambrian -- depositional environment -- molecular fossils -- Niutitang -- organic matter -- salinity; Geology -- Periodicals; 551
• DOI: 10.1002/gj.4593
• Languages: English
• ISSNs: 0072-1050

Abstract

Abstract : The early Cambrian Niutitang Formation is broadly developed in South China, especially in the Yangtze region. This research explains the nature of hydrocarbons through bitumen fractions of the early Cambrian sediments of the Niutitang Formation. For this purpose, source rock samples from two diverse outcrop sections are utilized for total organic carbon content (TOC), solvent extraction, and gas chromatography–mass spectrometry (GC–MS). Results show a lower quantity of extractable organic matter in these older sediments because of higher maturation history. The presence of monomethyl alkanes suggests the contribution of prokaryotic organisms, whereas the presence of hopanoids and C27 –C29 steranes shows the occurrence of eukaryotic algal sources in organic matter. Likewise, C30 ‐4‐methyl sterane, dinosteranes, and ß‐carotene also suggested incorporating prokaryotic and eukaryotic sources during the early Cambrian period. Various hopanoid parameters, alkylated aromatic isomers, triaromatic steroids, and vitrinite reflectance via methyl‐phenanthrene index reveal mature to higher thermal evolution levels of these lower Palaeozoic sediments. Similarly, a higher abundance of polyaromatic pyrene and fluoranthene indicates mature organic matter, and their presence could be due to hydrothermal action. The higher gammacerane index, lower pristine/phytane, and the presence of C30 dimethyl steranes indicate the anoxic saline sedimentary condition throughout the deposition of these lower Palaeozoic Niutitang Formation. The early Cambrian Niutitang Formation is deposited in an oxygen‐deficient environment and contains an adequate amount of mature‐high mature organic matter that could have the potential to produce gaseous hydrocarbons. Abstract : This study focuses on the origin of organic matter and depositional characteristics of early Cambrian Niutitang Formation from South China: New insights using molecular fossils. This research utilized saturated and aromatic hydrocarbons of the early Cambrian Niutitang Formation to elucidate the source of organic matter, thermal maturation level, and its depositional environment during the early Cambrian period.