滇西北拖顶地区志留系的发现

DISCOVERY OF THE SILURIAN SYSTEM IN THE TUODING AREA OF NORTHWEST YUNNAN

中咱地块南部的志留系有别于三江构造带其他地区的志留系 ,通过区域地质调查研究 ,将这套地层命名为吉仁水组 ,代表中咱地块南部地区志留系的岩相类型 ,时代为志留纪中、晚期。根据岩相类型的差异 ,中咱组可划分为两个岩性段 :第一段主要由白云质灰岩、灰岩、白云岩构成 ;第二段由泥质岩、细粒碎屑岩及白云质灰岩、灰岩、白云岩组成 ,陆源碎屑成分含量较高 。

The Silurian found in the Tuoding area of Zhongza Block is different from the Silurian strata that are distributed in other area of the Sanjiang Tectonic Belt. In this paper, a new lithostratigraphic unit, the Jirenshui Formation, is named on the basis of detailed regional geologic investigation and stratigraphic section research. It represents the Silurian distributed in the southern area of Zhongza Block and belong to Late and Middle Silurian age. The formation can be divided into two members. The first member consists chiefly of dolomitic limestone, limestone and dolomitite, and the second member is composed of mudstone, clastic rock as well as dolomitic limestone, limestone and dolomitite. In latter member, the constituent from land is much more in than the first member, but carbonate is less.