Facies analysis and sea-level change at the Guadalupian–Lopingian Global Stratotype (Laibin, South China), and its bearing on the end-Guadalupian mass extinction
Facies analysis and sea-level change at the Guadalupian–Lopingian Global Stratotype (Laibin, South China), and its bearing on the end-Guadalupian mass extinction
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DOI：
10.1144/0016-76492008-118
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发表时间：
2009-06
影响因子：
2.7
通讯作者：
P. Wignall;Stéphanie Védrine;D. Bond;Wei Wang;X. Lai;J. Ali;Haishui Jiang
中科院分区：
文献类型：
--
作者：
P. Wignall;Stéphanie Védrine;D. Bond;Wei Wang;X. Lai;J. Ali;Haishui Jiang
摘要：蓬莱滩瓜达鲁比亚-洛平系界线层型和邻近的中国南部来宾附近的铁桥剖面，记录了中二叠世生物危机期间江南盆地内一系列重大的环境变化。研究了这些剖面的层序地层学、岩石学和古生物记录，并分析了与之相关的锶同位素波动。丝虫有孔虫的大规模灭绝在时间上最明显地与火山作用的爆发和相对海平面的下降有关，这导致了以前以放射虫泥岩为主的环境中坡道条件(来宾石灰岩)的建立。这一回归也与87Sr/86Sr比值的最低点相吻合。低位沉积物中含有记录火山碎屑作用的镁铁质玄武岩颗粒，可能集中在来宾以西800公里处的峨眉山溢流玄武岩省。因此，该省与洪水玄武岩有关的异常猛烈的喷发可能是造成这次灭绝事件的环境压力的原因之一。随后的环境变化包括海侵、缺氧水域的扩散，如小型黄铁矿框体种群所指示的，以及主要的负碳同位素漂移。所有这些现象以前都与瓜达卢皮亚末期的灭绝有关，但实际上它们发生在危机之后，因为此时遇到了灭绝后的有孔虫动物群。
Abstract: The Guadalupian–Lopingian boundary stratotype at Penglaitan, and the nearby Tieqiao section, near Laibin, South China, record a series of major environmental changes within the Jiangnan Basin during a Mid-Permian biotic crisis. The sequence-stratigraphic, petrographic and palaeontological record of these sections has been studied and the associated strontium isotopic fluctuations have been assayed. Mass extinction of fusulinid foraminifers is most clearly associated in time with onset of volcanism and a relative sea-level fall that led to the establishment of mid-ramp conditions (Laibin Limestone) in settings that were previously dominated by radiolarian mudstones. The regression also coincides with a low point of 87Sr/86Sr ratios. The lowstand deposits contain mafic scoriaceous grains that record pyroclastic volcanism probably centred in the Emeishan flood basalt province 800 km to the west of Laibin. Thus, unusually violent eruptions associated with flood basalts in this province may have contributed to the environmental stresses responsible for the extinction event. Subsequent environmental changes included transgression, spread of dysoxic waters, indicated by populations of small pyrite framboids, and a major negative C-isotope excursion. All these phenomena have been previously related to the end-Guadalupian extinction but they in fact post-date the crisis because a post-extinction fauna of foraminifers is encountered at this time.