辽宁东部地区桥头组微生物诱发沉积构造(MISS)的发现及意义

Discovery and significance of microbial induced sedimentary structure (MISS) from the QiaotouFormation in eastern Liaoning

1研究目的辽宁东部地区位于华北克拉通的东北缘(Zhao Guochun et al.,2012)。该地区中元古代晚期—新元古代早期地层发育,层序保存完整且出露较好,是研究华北克拉通中、新元古界的关键地区之一。桥头组分布于辽宁东部的本溪、辽阳、丹东、大连等地区,曾被认为形成于新元古代晚期南华纪(辽宁省地质勘查院,2017)。近些年随着同位素测年技术的广泛应用,桥头组形成于中元古代晚期—新元古代早期的观点被广泛认可(Zhang Wen et al.,2020,2021;Zhao Hanqing et al.,2020),但目前针对桥头组的研究大多集中在物源分析及其对华北克拉通古地理重建等方面(Zhang Shuahong et al.,2016;He Tianchen et al.,2016;Zhang Wen et al.,2020,2021;Zhao Hanqing et al.,2020),少量文献则根据岩石学、矿物学、地球化学等传统地质方法对桥头组的古气候进行研究(曲洪祥等,2011;田德欣等,2018;吴子杰等,2020),但并未形成统一的认识。

Objectives and Methods:Through the re-investigation and understanding of the "mud crack-like sedimentary structure" in the Qiaotou Formation from late Mesoproterozoic to early Neoproterozoic in the eastern Liaoning,and by comparing with the contemporaneous microbial induced sedimentary structure(MISS) in other areas of the NCC,For the first time,the fractured sedimentary structure discovered in the Qiaotou Formation in Liaoning was identified as MISS.Results:The fissure structure found in the Qiaotou Formation is MISS,which is formed by the physical destruction of microbial mats.Conclusions:The MISS identified in the Qiaotou Formation has spindle-like,three-connected ornithoid and partially connected branched morphology,so it is speculated that the Qiaotou Formation was formed in the sedimentary environment of the upper part of the supratidal zone.This discovery provides basis for stratigraphic and sedimentological studies of the Qiaotou Formation,and is of great significance for studying the evolution of early life on earth and exploring the long-term impact of biota on the atmosphere and hydrosphere.