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