桂林岩溶地区粘土砾石层中第三纪地层的发现及其意义

DISCOVERY OF TERTIARY STRATA IN A CLAYGRAVEL LAYER OF GUILIN KARST AREA AND ITS IMPLICATIONS

桂林岩溶地区粘土砾石层中发现第三纪地层的存在，由下至上发现３个孢粉化石组合，即：第Ⅰ组合（乐群组组合），栎粉属—栗粉属—柏科—杉科组合；第Ⅱ组合（乌石岭组组合），栎粉属—栗粉属—光面水龙骨单缝孢属组合；第Ⅲ组合（望城岗组组合），栗粉属高含量组合。它们分别代表中始新世、中晚始新世、上新世的地层。同时还发现了早第三纪时有海水沿古漓江河道间断入侵的现象。所有这些将对长期有争议的粘土砾石层（所谓“泥砾层”）的成因及形成时代会有更深入的认识，也将对该区相应时代热带岩溶发育的研究提供有价值的资料。

It has been found that Tertiary strata exists in the claygravel layers of Guilin karst area. There are three pollen fossil groups, i.e.,from bottom to top, the first group(Lequn group):oakchestnutcypressfir; the second group(Wushiling group):oakchestnutpolypodiaceaesporites sp.; the third group (Wangchenggang group): high percentage of chestnut. They correspond to middle Eocene, middleupper Eocene and Pliocene respectively. The authors also found the evidences of intermittent sea transgression along paleoLi River during early Tertiary. These findings would be useful in understanding the origin and age of the claygravel layer (socalled“muddy gravel layer”),which is a longterm disputed issue,and in studying the tropical karst development of the area during relevant times. 