广西浪平地区黄龙组底部的核形石及其意义

Oncoids and Its Significance from the Base of Huanglong Formation in Langping,Guangxi

广西浪平地区石炭纪地层出露完整,在黄龙组底部发育一套核形石生物碎屑灰岩.为了深入认识核形石的形成环境及地质意义,开展了古生物学、沉积学和岩相学研究.核形石生物碎屑灰岩中虫筳类化石表现出Profusulinella aljutovica-Taitzehoella taitzehoensis extensa带的特征,指示其发育在莫斯科期的初期.本文共识别出4种核形石类型:泥晶核形石、富屑纹层核形石、藻(菌)纹层核形石和复合纹层核形石;以及4种沉积微相:MF1,MF2,MF3和MF4.在莫斯科期初期,海平面开始回升,使该地区的沉积环境发生变化,为核形石的形成提供了微生物活动基础和水动力条件.

The Carboniferous strata completely outcrops in Langping area,Guangxi.Oncoid-bioclastic limestone develops at the base of Huanglong Formation.To reveal the depositional environment and geological significance of the oncoids,the studies relating to paleontology,sedimentology,and petrography were carried out.The fusulinids in oncoid-bioclastic limestone establish an earliest Moscovian age,which corresponds to Profusulinella aljutovica-Taitzehoella taitzehoensis extensa subzone in South China.Four oncoid types have been recognized:micrite oncoid,debris envelope oncoid,algae envelope oncoid,and composite oncoid.Four microfacies types have been identified:MF1,MF2,MF3,and MF4.In the earliest Moscovian,the sea level started to rise,which changed the depositional environment,providing the basis for microbial activity and high water energy for the formation of oncoids in the study area.