豫西P–Tr之交的微生物成因构造与后生动物扰动构造的耦合变化及生态学意义

Coupling variation of microbially induced sedimentary structures and metazoan bioturbation structures in the Permian–Triassic successions,western Henan Province

豫西登封、济源、宜阳、荥阳和巩义等地发育一套连续的二叠纪–三叠纪之交的陆相地层孙家沟组、刘家沟组和和尚沟组,保存着有环境和生物信息的微生物成因构造以及后生动物扰动构造,对二者的深入研究对二叠纪–三叠纪之交的陆相微生物与环境以及早三叠世的生物复苏有着重要的意义。研究区5个剖面保存了丰富的微生物成因构造和后生动物扰动构造,其中微生物成因构造有3大类、25小类,后生动物扰动构造有6属13种。这些构造在地层自下而上有一定的变化规律:微生物成因构造自孙家沟组中上部出现到刘家沟组顶部消失;后生动物扰动构造自刘家沟组上部出现,到和尚沟组上部逐渐增多,至中三叠世油房庄组基本达到灾变事件前的生物水平;二者仅在刘家沟组共生。本研究表明研究区微生物成因构造和后生动物扰动构造在整体上具有负相关性与耦合变化关系。

Microbially induced sedimentary structures(MISS)and metazoan bioturbation structures(trace fossils)are abundant in Upper Permian–Lower Triassic Sunjiagou,Liujiagou and Heshanggou formations in Xingyang,Jiyuan,Dengfeng,Yiyang and Gongyi areas,western Henan,North China.The MISS can be divided into 25 subtypes belonging to three major groups,i.e.,mat growth,mat destruction and mat decay structures.Thirteen ichnospecies of 6 ichnogenera are recognized from the Liujiagou and Heshanggou formations.The MISS and metazoan bioturbation structures(trace fossils)vary from the bottom to the top of the strata with some patterns.The MISS first appeared in the Sunjiagou Formation,became abundant in the Liujiagou Formation and disappeared completely in the Heshanggou Formation.The metazoan bioturbation structures first appeared in the middle and upper parts of the Liujiagou Formation,gradually increased in the upper part of the Heshanggou Formation,and basically recovered to the diversity level of the pre-Permian–Triassic catastrophe in the Middle Triassic Youfangzhuang Formation.The MISS and the metazoan bioturbation structures cooccur only in the Liujiagou Formation.The results show that,in general,there is a negative correlation between the development of the MISS and the metazoan bioturbation structures in the study area,and there is a coupling variation of the two types of structures.