Paleoceanographic indicators for early Cambrian black shales from the Yangtze Platform, South China: Evidence from biomarkers and carbon isotopes

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Title:	Paleoceanographic indicators for early Cambrian black shales from the Yangtze Platform, South China: Evidence from biomarkers and carbon isotopes
Authors:	林殿順;Lan, CHEN;Hong, ZHONG;Ruizhong, HU;Jiafei, XIAO;Louis Loung-Yie, TSAI;Andrew Tien-Shun, LIN;Yanrong, ZOU
Contributors:	地球科學學院地球科學學系
Keywords:	Abundance;Algae;Anoxia;Anoxic conditions;Bacteria;Biomarkers;black shales;Cambrian;carbon isotope;Carbon isotopes;China;Deposition;Early Cambrian;Environmental changes;Fossils;Geochemistry;Indicators;Organic carbon;paleoceanography;Saturated hydrocarbons;Shale;Shales;South China;中国南方;古海洋学;成熟度指标;扬子地台;早寒武世;有机碳同位素;生物标志物;黑色页岩
Date:	2012-01-01
Issue Date:	2026-04-23 11:39:49 (UTC+8)
Publisher:	Science Press;Oxford, UK: Blackwell Publishing Ltd
Abstract:	摘要： The lower Cambrian Niutitang Formation, a widespread black shale deposition, is of geological interest because of its polymetallic beds, Cambrian explosion, depositional ages, dramatic environmental changes and so on. Previous study focused mainly on inorganic geochemistry and few studies have investigated the organic fractions of upper Neoproterozoic-lower Cambrian strata in South China. Here we report a study of biomarkers plus organic carbon isotopes for black shales from Ganziping, Hunan Province （China）. All the saturated hydrocarbon fractions have a unimodal distribution of n-alkanes, a high content of short-chain alkanes and maximize at C 19 or C 20 （C 23 for sample Gzh00-1）. The C 27 /C 29 sterane ratio ranges from 0.77 to 1.20 and 4-methylsteranes are in low abundance. These parameters indicate that algae and bacteria are the important primary producers. Furthermore, biomarker maturity proxies show the samples to be higher maturity. The low Pr/Ph values （0.7） suggest that the samples were deposited under anoxic conditions and, likely, under stratified water columns. In addition, 25-norhopanes and gammacerane are present as diagnostic indicators of normal marine salinity and dysoxic to anoxic conditions. During the Early Tommotian, known to coincide with a transgression event, small shelly fossils increased in abundance and diversity. Moreover, positive δ 13 C org excursions close to 1.4‰ occur at the base of the Tommotian stage. In summary, the Early Cambrian black shales were deposited under dramatic paleoenvironmental changes, including oceanic anoxia, higher primary productivity and sea-level rise. 其他題名： Acta Geologica Sinica 出版者： Oxford, UK: Blackwell Publishing Ltd 出版日期： 2012-10 出處： Acta geologica Sinica (Beijing), 2012-10, Vol.86 (5), p.1143-1153 資源來源： China Online Journals (COJ) 版權： 2012 Geological Society of China 版權： Copyright © Wanfang Data Co. Ltd. All Rights Reserved. 識別號： ISSN: 1000-9515 識別號： EISSN: 1755-6724 識別號： DOI: 10.1111/j.1755-6724.2012.00737.x
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