Quantitative stratigraphy of the Wufeng and Lungmachi black shales and graptolite evolution during and after the Late Ordovician mass extinction
Quantitative stratigraphy of the Wufeng and Lungmachi black shales and graptolite evolution during and after the Late Ordovician mass extinction
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DOI：
10.1016/j.palaeo.2013.08.005
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发表时间：
2013-11
期刊：
影响因子：
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通讯作者：
Junxuan Fan;Qing Chen;M. Melchin;H. Sheets;Zhongyang Chen;Linna Zhang;Xudong Hou
中科院分区：
文献类型：
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作者：
Junxuan Fan;Qing Chen;M. Melchin;H. Sheets;Zhongyang Chen;Linna Zhang;Xudong Hou
华南扬子地台广泛分布着含笔石黑色页岩。本文在系统研究了19个剖面的基础上，对晚奥陶世生物大灭绝期间和之后的笔石生物多样性变化进行了定量的地层分析。图相关和稀疏相结合的方法使采样强度对生物多样性估计的影响成为可能。笔石多样性在复合体dicellograptus complexusChron达到顶峰，然后逐渐下降到p。pacificusChron。随后是两个阶段的大灭绝，第一个也是主要的阶段发生在非凡代谢物时期，第二个也是次要的阶段发生在20世纪晚期。persculptusChron。第二阶段的灭绝主要表现为大灭绝事件中残存的大灭绝，但标准化多样性曲线没有明显下降。此后，笔石丰富度在早期和中期出现了适度的增加，随后在ep后期出现了相当大的下降。【正确答案】c。vesiculosusChron。本研究还表明，从卡天纪中期到鲁达尼世早期，研究剖面的沉积速率缓慢且不均匀，其中赫南天纪的沉积速率相对较慢。后者以及红花园和关武剖面的断陷可能反映了海南田冰期和区域构造运动的影响。
Graptolite-bearing black shales are widely distributed on the Yangtze Platform in South China. Based on 19 sections systematically studied recently, we conducted a quantitative stratigraphic analysis of the graptolite biodiversity change during and after the Late Ordovician mass extinction. The combination of graphic correlation and rarefaction methods make it possible to evaluate the effect of sampling intensity on biodiversity estimates. Graptolite diversity reached its peak in theDicellograptus complexusChron, and then a gradual decline to theP. pacificusChron. It was followed by a two-step mass extinction, the first and major phase occurred in theMetabolograptus extraordinariusChron, and the second and minor phase in the latestM. persculptusChron. The second phase of the extinction was mostly represented by the elimination of the Diplograptina survivors from the major extinction event, but did not show significant decline in standardized diversity curve. Thereafter, a moderate increase in richness appeared in the early and midParakidograptus acuminatusChron, which was followd by a considerable decrease of graptolite richness in the lateP. acuminatusChron and earlyC. vesiculosusChron. The present study also indicates slow and uneven sedimentation rates in the studied sections from mid-Katian to early Rhuddanian, including a relatively slower sedimentation rate during the Hirnantian Epoch. The latter, and the hiatus at the Honghuayuan and Guanwu sections, probably reflect the effects of the Hirnantian glaciation and regional tectonic movements.