| 湖北松滋地区下奥陶统叠层石沉积特征 |
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| 引用本文： | 肖传桃,吴彭珊,李沫汝,杨志伟,周思宇,郭瑞,张超.湖北松滋地区下奥陶统叠层石沉积特征[J].沉积学报,2018,36(5):853-863. |
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| 作者姓名： | 肖传桃 吴彭珊 李沫汝 杨志伟 周思宇 郭瑞 张超 |
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| 作者单位： | 长江大学地球科学学院, 武汉 430100 |
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| 基金项目： | 国家自然科学基金项目（41572322）；湖北省创新群体基金（2015CFA024） |
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| 摘 要： | 系统性地对湖北松滋地区下奥陶统叠层石特征进行的详细研究。结果显示，叠层石在研究区下奥陶统南津关组、分乡组和红花园组均有分布，在纵向上具有规模、厚度和数量逐渐减小的特征，横向上叠层石类型也发生有规律的变化，由水平层状、波状逐渐变为柱状的类型。新发现并命名了两种叠层石类型，即凝块状叠层石和双锥柱状叠层石。根据几何形态特征，可以将研究区的叠层石分为层状、波状、柱状、丘状以及凝块状五种类型。在对各类型叠层石的沉积特征进行详细阐述基础上，根据叠层石发育的形态类型，结合不同类型叠层石内部的岩性、微相及显微特征，对研究区各类叠层石沉积环境进行了分析，并总结了研究区叠层石的沉积模式。根据中奥陶世初期后生动物的大量增加与叠层石突然减少的对应关系，结合研究区叠层石中发现大量后生底栖食草腹足类Ecculiomphalus化石等现象，认为叠层石的逐渐减少、衰退与后生动物丰度增加有一定关系，食草动物不仅啃食了形成叠层石的菌藻类微生物，造成叠层石数量的不断减少，而且破坏了叠层石的生长状态，并形成了独具研究区特征的凝块状叠层石。此外，研究认为，中奥陶世开始，海平面的快速上升也是研究区叠层石减少直至消失的原因之一。
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| 关 键 词： | 叠层石 凝块状叠层石 沉积特征 后生动物大辐射 下奥陶统 松滋地区 |
| 收稿时间： | 2017-06-14 |
Sedimentary Characteristics of Lower Ordovician Stromatolites in Songzi Area,Hubei Province |
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| Institution: | School of Geosciences, Yangtze University, Wuhan 430100, China |
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| Abstract: | The characteristics of Lower Ordovician stromatolites in the Songzi area of Hubei province were studied systematically for the first time, and the stromatolites were distributed in the Lower Ordovician Nanjinguan, Fenxiang and Honghuayuan formations in the study area. They were characterized by decrease of scales, thickness and quantity gradually on the vertical profiles. The stromatolite types were changed laterally from the horizontal bedded, wavy-shaped and gradually into columnar type. According to the geometric classification scheme, the stromatolites in the study area could be divided into the following types, namely, lamellar-shaped, wavy-shaped, columnar-shaped, mound-shaped and clotted-shaped stromatolite, respectively. Among them, the clotted-shaped stromatolite and double cone-shaped stromatolite were discovered for the first time and newly named by the authors. Based on detailed analysis for the sedimentary characteristics of each type of stromatolite, combined with lithology, microphase and microscopic characteristics, the depositional environments were studied for different types of stromatolite, and their sedimentary models were also summarized. According to the corresponding relationship between the increase of metazoon in the early stage of Middle Ordovician period and the rapid reduction of the stromatolites, combined with the phenomenon of a lot of drilling and predatory gastropods Ecculiomphalus fossils inside the stromatolites, the authors believed that the reduction and decline of stromatolites could be related to the increase in abundance of metazoan. Drilling predators not only grazed bacteria algae microorganisms forming stromatolites and resulted in a decrease of stromatolites, but also destroyed the growth of stromatolites, and lead to the formation of clotted-shaped stromatolite. In addition, the author argues that the rapid rise of the sea level could be also one of the reasons for the reduction and disappearance of stromatolites from the beginning of the Middle Ordovician period in the study area. |
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