Petrography and origin of the Lower Ordovician microbial carbonates in the Songzi Area of Hubei Province,middle Yangtze region,China  

作　　者：Chuan-Tao Xiao Guo-Qi Wei Zhen-Yu Song Yun-Peng Xiao Wei Yang Man Dong Yun-Fei Huang Da Gao 

机构地区：[1]Geosciences School of Yangtze University,Wuhan 430100,Hubei,China [2]Research Institute of Petroleum Exploration and Development,PetroChina,Langfang 065007,Hebei,China

出　　处：《Petroleum Science》2019年第5期956-971,共16页石油科学（英文版）

基　　金：supported by the National Natural Science Fund of China(Grant No.41572322);Hubei Innovation Group Fund(Grant No.2015CFA024)

摘　　要：This study is the first systematic assessment of the Lower Ordovician microbial carbonates in Songzi,Hubei Province,China.This paper divides the microbial carbonates into two types according to growth patterns,namely nongranular and granular.The nongranular types include stromatolites,thrombolites,dendrolites,leiolites and laminites;the granular types are mainly oncolites and may include a small amount of microbiogenic oolite.According to their geometric features,the stromatolites can be divided into four types:stratiform,wavy,columnar and domal.Additionally,dipyramidal columnar stromatolites are identified for the first time and represent a new type of columnar stromatolite.The thrombolites are divided into three types:speckled,reticulated and banded.The grazing gastropod Ecculiomphalus and traces of bioturbation are observed in the speckled and reticulated thrombolites.This paper considers these two kinds of thrombolites to represent bioturbated thrombolites.These findings not only fill gaps in the field of domestic Ordovician bioturbated thrombolites but also provide new information for the study of thrombolites.Based on the analysis of the sedimentary characteristics of microbialites,the depositional environments of the various types of microbialites are described,and the distribution patterns of their depositional environments are summarized.The relationship between the development of microbialites and the evolution and radiation of metazoans during the Early to Middle Ordovician is discussed.Consistent with the correspondence between the stepwise and rapid radiation of metazoans and the abrupt reduction in the number of microbialites between the late Early Ordovician and the early Middle Ordovician,fossils of benthonic grazing gastropods(Ecculiomphalus)were found in the stromatolites and thrombolite of the study area.It is believed that the gradual reduction in microbialites was related to the rapid increase in the abundance of metazoans.Grazers not only grazed on the microorganisms that formed stromatolite

关 键 词：Microbial carbonate STROMATOLITES Thrombolites ONCOLITE Lower Ordovician Songzi Area 

分 类 号：P534.4[天文地球—古生物学与地层学] P588.245[天文地球—地质学]