广西来宾蓬莱滩剖面瓜德鲁普统—乐平统(G-L)界线生境型及其意义

The Habitat type and Is Sgnificance of Guadalupian-Lopingian(G-L) Bundary in Penglaitan Sction,Guangxi

对广西来宾地区蓬莱滩剖面瓜德鲁普统茅口组(P_2m)至乐平统合山组(P_3h)进行了详细的生境型分析,共识别出4个大类与5个亚类生境型,包含Ⅱ2型(潮间带与正常浪基面之间),Ⅲ_1型(上部浅海上部),Ⅲ_2型(上部浅海下部)、Ⅳ型(下部浅海)和Ⅴ型(半深海)。生境型总体上反映海平面变化的特点。从瓜德鲁普世末期到乐平世早期,海平面呈缓慢上升至缓慢下降再突然上升变化,表现为:瓜德鲁普世末期处于海退期,而乐平世早期则变为海侵阶段。海退阶段海平面的较低水平对应着该时期主要的生物灭绝,但生物灭绝的详细步调并未与海平面的下降一致,故认为瓜德鲁普世的大规模海退与生物灭绝事件有一定关系,但不是唯一的原因。大规模海退造成海洋生物生存压力增大,尤其是生活在浅海区域的生物,同时伴随的古海洋环境发生恶化,共同导致了大规模的生物灭绝事件。

The authors have carried on the detailed analysis of the habitat type of maokou formation to heshan for- mation in Penglaitan section, Guangxi. They identified 4 major categories and 5 subclasses of habitat type, it con- tained Ⅱ 2 （ between the intertidal zone and normal wave base level）, Ⅲ 1 （ The upper part of the upper shallow seas）, Ⅲ2 （the lower part of the upper shallow sea） , Ⅳ （the lower shallow sea） and Ⅴ （the bathyal region）. Habitat type generally reflected the characteristics of sea level change. From late Guadalupian to early Lopingian, the sea level showed a trend of changes in slowly rising to slowly falling and then suddenly rising. Late Guadalupi- an was in regressive period, while early Lopingian became into transgression phase. In regressive period, the com- paratively low sea level corresponded to the main extinction in this period, but the detailed step of this mass ex- tinction was not consistent with the descending of sea 1 evel. So this article hold that the mass extinction in Guada- lupian was associated with Large-scale regression, however, large-scale regression was not the only cause of this extinction. Large-scale regression increased the survival pressure of Marine biological, espeeially for the organisms living in the shallow water area, at the same time, because of the deterioration of the ancient ocean, a mass ex- tinction event happened in end-guadalupian.