乐业县大石围天坑群洞穴第三纪堆积的孢粉组成特征及相关问题的探讨

ISCUSSION ON THE FEATURES OF SPORE-POLLEN COMPOSITION IN THE CAVE SEDIMENTS OF THE TERTIARY SYSTEM AND THE CORRELATIVE QUESTIONS IN DASHIWEI TIANKENG GROUP, LEYE COUNTY

介绍了广西乐业县大石围天坑群中蚂蜂洞、里郎洞新第三纪堆积孢粉组合特征,并由此探讨了大石围天坑四层不同高程上的洞穴的发育时代。蚂蜂洞和里郎洞新第三纪堆积是迄今广西所发现的海拔高程最高的第三纪地质剖面,其孢粉主要以被子类桤木粉属(Alnipollenites)、栎粉属(Quercoidites)、桦粉属(Betulaepollenites)、栗粉属(Cupuliteroipollenites),裸子类双束松粉属(Pinuspollenites),蕨类水龙骨单缝孢属(Polypodiaceaaesporites)、桫椤孢属(Cyathidites)为主,反映当时主要为亚热带温暖、阴湿的森林气候环境。根据与蚂蜂洞的相对位置,推测较之高的南东支洞、最高层洞形成时代应早于新第三纪,比之低的中洞应形成于早—中更新世,而地下河则在全新世时期形成。

The features of the spore-pollen composition in sediments of the Tertiary system from Mafeng cave and Lilang cave are introduced. The formation time of four layers of caves in different altitudes in the Dashiwei Tiankeng group is studied. The sediments of the Tertiary system in Mafeng cave and Lilang cave are the highest geo-profile of the Tertiary period ever found in Guangxi. The spore-pollen, dominated by Alnipollenites, Quercoidite, Betulaepollenite, Cupuliteroipollenites, Pinuspollenites, Polypodiaceaaesporites and Cyathidites, represents warm, shady and wet environment under the subtropical forests. According to the location to Mafeng cave, the relatively high cave-SE sub-cave should be formed before the early Tertiary period by inference, and the relatively low cave-the middle cave in the Pleistocene epoch but the underground river in the Holocene epoch.