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Paleontological study on the early phase of Cambrian Explosion based on the small shelly fossils and ichnofossils

基于小贝化石和化石的寒武纪大爆发早期古生物学研究

基本信息

批准号：
21540482
负责人：
OJI Tatsuo
金额：
$ 2.75万
依托单位：
Nagoya University (2010-2011)The University of Tokyo (2009)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2009
资助国家：
日本
起止时间：
2009 至 2011
项目状态：
已结题

项目摘要

We investigated pattern of rapid evolution of metazoa occurred in the Early Cambrian, based on the ichnofossils and small shelly fossils sampled or observed from Newfoundland, Canada, Guizhou and Yunnan provinces, China and Gobi-Altai, Mongolia. As a result, following three things were clarified. 1. Two-staged, stepwise increase in the diversity and bedding plane bioturbation index were detected in the Treptichnus pedum and the Rusophycus avalonensis zones, the lowest biozones in the Lower Cambrian. In these zones, there were no development of a clear differentiation of ichnofossils according to different sedimentary facies, and also there is no clear ichnofossils detected on the upper surface of microbial mats. 2. Based on the detailed morphological studies on the protoconodonts from the lower Meishucun Stage in Yunnan Province, some of these are considered as grasping spines of chaetognaths(arrow worms). This discovery in turn suggests that there were predatory animals present in the mid-water column of the pelagic environment in the Early Cambrian. 3. We compared ichnofossils from two late Early Cambrian formations(Chintingshan and Balang), the former formation deposited slightly shallower environment than the latter. In this time, there was already differentiation of ichnofossils according to the different environments, which character was not detected in the ichnofossils from the earliest Cambrian of Newfoundland.

根据加拿大纽芬兰省、中国贵州、云南省和蒙古戈壁-阿尔泰等地的遗迹化石和小壳化石，探讨了早寒武世后生动物的快速演化模式。结果，澄清了以下三件事。1.两个阶段，逐步增加的多样性和层面的生物扰动指数检测的Treptichnus pedum和Rusophycus avalonensis带，在下寒武统的最低生物带。在这些带中，没有发育出明显的遗迹化石按沉积相的分异，也没有在微生物席的上表面检测到明显的遗迹化石。2.根据对云南梅树村阶下段原牙形刺的详细形态学研究，认为其中部分原牙形刺为毛颌类（箭蠕虫）的抓刺。这一发现反过来又表明，在早寒武世的中上层环境中，存在着食肉动物。3.本文对早寒武世晚期金顶山组和八郎组的遗迹化石进行了比较，金顶山组的沉积环境略浅于八郎组。这一时期的遗迹化石已经出现了因环境而异的分化现象，这是纽芬兰早寒武世遗迹化石所没有的。