滇东曲靖、沾益地区下、中泥盆统岩石地层单位沿革概况及修订建议

REVISION OF THE LOWER AND MIDDLE DEVONIAN LITHOSTRATIGRAPHY IN QUJING AND ZHANYI,EASTERN YUNNAN PROVINCE,CHINA

滇东曲靖、沾益地区早、中泥盆世地层出露良好,动植物化石保存颇佳、类型丰富,是研究我国泥盆纪动植物演化及相关古生态和古气候问题的重要区域之一,但因受到地理名称变更等因素的影响,导致不同学者对研究区内岩石地层单位名称的使用持不同意见,甚至存在较大分歧。这些分歧阻碍了研究区内泥盆纪地层的划分与对比,不利于进一步的学术交流与研究。针对该问题,根据在该地区中重新实测的下、中泥盆统剖面数据,并结合《中国地层指南及中国地层指南说明书》(修订版)中的规定和公开发表的相关地层标准化建议的文章,同时参考《中国岩石地层词典》和《中国地层名称》,对研究区内的岩石地层单位的沿革概况进行了重新梳理,整理了研究区内下、中泥盆统地层单位的同物异名和异物同名,并对它们的有效性和合法性进行了讨论。最终提出滇东曲靖、沾益地区下、中泥盆统岩石地层单位由老至新应为:下西山村组、西屯组、桂家屯组、徐家冲组、穿洞组和上双河组,并由前四个地层单位共同组成"翠峰山群",后两个组构成"西冲群"。

Lower and Middle Devonian strata crop out well in Qujing and Zhanyi, eastern Yunnan. Abun- dant animal and plant fossils are well preserved in these strata. They are hence very important for the study of Devonian animal and plant evolution, as well as related issues in palaeoecology and palaeoclimate. However, due to the combined factors of changing geographic names, loss of specimens of index fossils, and the incompleteness of type sections, different researchers use different lithostratigraphic names for the same stratigraphic unit, which creates problems in stratigraphic correlation and hinders scientific communi- cations. Based on measured stratigraphic sections by the present authors and guided by stratigraphic codes and principles （including Stratigraphic Guide of China and Its Specification, Lithostratigraphic Dic- tionary of China, and Geological Formation Names of China）, Lower and Middle Devonian lithostrati- graphic unit names in east Yunnan are discussed with regard to their validity and legitimacy. Finally, we propose a set of lithostratigraphic names for the Lower and Middle Devonian in eastern Yunnan Province. In ascending order, they are the Xiaxishancun Formation, Xit chong Formation, Chuandong Formation, and Shangshuanghe long to the Tzuifengshan Group, and the latter two belong to un Formation, Guijiatun Formation, Xujia Formation. The former four formations be the Xichong Group.