摘要:
瓜德鲁普统末期生物灭绝是发生在二叠末期生物灭绝之前的一次独立的生物灭绝事件。该次生物灭绝事件对当时海洋底栖生物危害的严重性曾被认为可与五大生物灭绝事件对生物的影响程度相提并论。近年来,随着地层年龄数据的逐渐增多,地层的年代归属逐渐明朗,瓜德鲁普末期生物灭绝的严重性受到越来越多的质疑。同时,曾被认为是该次生物灭绝的主要原因——峨眉山大火成岩省(LIP)也受到质疑。峨眉山LIP是否仍是该次生物灭绝的主要原因？为了阐明上述问题,文章综述了瓜德鲁普末期生物灭绝、峨眉山LIP的喷发、卡匹敦阶碳、锶同位素变化以及引起该次生物灭绝的主要原因。结合研究数据认为:①瓜德鲁普末期生物灭绝事件对浅海底栖生物的影响不是特别严重,生物多样性减少幅度比五大生物灭绝事件要小;②瓜德鲁普统—乐平统(G-L)界线附近碳同位素负偏受成岩作用和相变的影响较大,卡匹敦阶碳同位素比值的变化存在两次负偏,第一次发生在卡匹敦中期(幅度约为1.0‰至1.5‰),第二次发生在G-L界线(幅度约为1.4‰至2‰);③该次生物灭绝的主要原因很可能不是峨眉山大火成岩省,而可能是大规模海退和海洋缺氧。
Abstract:
End-Guadalupian mass extinction was an independent extinction event before the end-Permian mass extinction. During this biotic crisis, the severity effected on the benthos was believed to be the similar scale as the “Big Five” mass extinction. Recently, owing to the increasing of age data and the precise stratigraphic timescale, more and more researchers began to challenge the severity of this extinction. Meanwhile, the main cause of this extinction, Emeishan LIP, was also questionable. Whether Emeishan LIP was still the main cause of this biotic crisis. In order to figure out this problem, this paper reviews the end-Guadalupian mass extinction, the Emeishan LIP eruption, the C and Sr isotopic changes in Capitanian and the main causes of this mass extinction. Combined with some of the authors' data, they believe that: (1) the impact of end-Guadalupian mass extinction on the benthos was not serious as once to be thought. Decreasing scale of biodiversity was smaller than the “Big Five” mass extinction. (2) the negative excursion of C isotope near the G-LB was affected mostly by diagenesis and facies change. There are two carbon isotopic negative excursions in the mid-Capitanian (excursion amplitude is about 1.0‰ to 1.5‰) and the G-L Boundary (excursion amplitude is about 1.4‰ to 2‰), respectively. (3) The main causes of this mass extinction were probably sea level fall and marine anoxia, instead of Emeishan LIP eruption.
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