论文部分内容阅读
The Cenomanian-Turonian oceanic anoxic event (C/T OAE) is developed in southern Tibet. Organic geochemical study of the Cenomanian-Turonian sediments from the Gamba and Tingri areas shows that the mid-Cretaceous black shales in southern Tibet are enriched in organic carbon. The molecular analyses of organic matter indicate marine organic matter was derived from algae and bacteria. In the Gamba area, the organic matter is characterized by abundant tricyclic terpanes and pregane, which are predominant in 191 and 217 mass chromatograms, respectively. Pristane/phytane (Pr/Ph) ratios in the C/T OAE sediments are less than 1, demonstrating the domination of phytane. The presence of carotane can be regarded as a special biomarker indicating oxygen depletion in the C/T OAE sediments in the Tethyan Himalayas. In anoxic sediments, β-carotane and γ-carotane are very abundant. The β- and γ-carotane ratios relative to nC 17 in the Cenomanian-Turonian anoxic sediments vary from 32.28～ 42.87 and 5.10～ 11.01.
The Cenomanian-Turonian oceanic anoxic event (C / T OAE) was developed in southern Tibet. Organic geochemical study of the Cenomanian-Turonian sediments from the Gamba and Tingri areas shows that the mid-Cretaceous black shales in southern Tibet are enriched in organic carbon . The molecular analyzes of organic matter indicate identity marine organic matter was derived from algae and bacteria. In the Gamba area, the organic matter is characterized by abundant tricyclic terpanes and pregane, which are predominant in 191 and 217 mass chromatograms, respectively. Pristane / phytane (Pr / Ph) ratios in the C / T OAE sediments are less than 1, demonstrating the domination of phytane. The presence of carotane can be considered as a special biomarker indicating oxygen depletion in the C / T OAE sediments in the Tethyan Himalayas. The β-carotane and γ-carotane are very abundant. The β-and γ-carotane ratios relative to nC 17 in the Cenomanian-Turonian anoxic sediments vary from 32.28 to 4 2.87 and 5.10 ~ 11.01.