High-resolution C-isotope chemostratigraphy of the uppermost Cambrian stage (Stage 10) in South China: implications for defining the base of Stage 10 and palaeoenvironmental change
High-resolution C-isotope chemostratigraphy of the uppermost Cambrian stage (Stage 10) in South China: implications for defining the base of Stage 10 and palaeoenvironmental change
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华南最上寒武纪（第10阶段）高分辨率C同位素化学地层学：对确定第10阶段底部和古环境变化的意义
DOI：
10.1017/s0016756817000188
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发表时间：
2017
影响因子：
2.3
通讯作者：
Shen Yanan
中科院分区：
文献类型：
--
作者：
Li D;an;Zhang Xiaolin;Chen Kefan;Zhang Guijie;Chen Xiaoyan;Huang Wei;Peng Shanchi;Shen Yanan
摘要华南地区的瓦尔岗剖面是寒武系第10阶基底的一个潜在的全球层型剖面和点。在本研究中，我们报告了高分辨率的碳同位素组成，并确定了三个大的负δ 13 C偏移，即N1，N2和N3在瓦尔岗。N1位于Lotagnostus americanus的首次出现基准面（FAD）之上，对应于Proconodontus posterocostatus牙形刺带的可能基底。N2在Micragnostus chuishuensis三叶虫带和Proconodontus muelleri牙形刺带中被鉴定。N3位于Leiagnostus cf. bexelli - Archaeuloma taoyuanense三叶虫带或Eoconodontus牙形石带。N1和N2可以与全球观测到的寒武纪碳同位素漂移（TOCE）顶部之前的负δ 13 C漂移相关。N3可以与TOCE或HEllnmaria-Red Tops Boundary（HERB）事件相关。N1和L. americanus强烈支持第10阶的基底最好由L.美国人利用箱形模型对华南地区δ 13 C负漂移的成因进行了定量分析。我们的数值模拟表明，台地上富含有机质的沉积物的风化作用可能是导致华南瓦尔岗第10阶段δ 13 C负漂移的原因之一，这可能是由于间歇性的海平面下降和/或海水中溶解有机碳（DOC）储层的氧化作用所致。
Abstract The Wa'ergang section in South China has been proposed as a potential Global Stratotype Section and Point (GSSP) for the base of Stage 10, the uppermost stage of the Cambrian System. In this study, high-resolution C-isotopic compositions are reported and we identified three large negative δ13C excursions, namely N1, N2 and N3, at Wa'ergang. The N1 is located just above the First Appearance Datum (FAD) of Lotagnostus americanus, corresponding to the possible base of the Proconodontus posterocostatus conodont Zone. The N2 was identified within the Micragnostus chuishuensis trilobite Zone and the Proconodontus muelleri conodont Zone. The N3 is located in the lowermost part of the Leiagnostus cf. bexelli – Archaeuloma taoyuanense trilobite Zone or Eoconodontus conodont Zone. The N1 and N2 can be correlated with the negative δ13C excursions preceding the Top of Cambrian Carbon Isotope Excursion (TOCE) observed globally. The N3 can be correlated with the TOCE or the HEllnmaria–Red Tops Boundary (HERB) Event. The inter-basinal correlation of N1 and L. americanus strongly supports that the base of Stage 10 may be best defined by the FAD of L. americanus. We also used a box model to quantitatively explore the genesis of the negative δ13C excursions from South China. Our numerical simulations suggest that weathering of the organic-rich sediments on the platform, probably driven by intermittent sea level fall and/or the oxygenation of the Dissolved Organic Carbon (DOC) reservoir in seawater, may have contributed to the generation of the negative δ13C excursions observed in the Stage 10 at Wa'ergang in South China.