初论变异性不整合——以滇西北中甸地区为例

VARIABILITY UNCONFORMITY IN ZHONGDIAN REGION, NORTHWESTERN YUNNAN PROVINCE, CHINA

通过对滇西北中甸地区 1∶5万地质填图 ,并结合地质构造综合研究 ,首次提出下三叠统布伦组与下伏上古生界为变异性不整合的新看法 .它是在大陆引张环境下形成的一种地层接触关系 .主要识别标志是 :区域性强烈起伏的不整合面 ;下伏基盘伸展构造和引张环境玄武岩的发育 ;上覆沉积厚度显著变化、相变急剧 ;不整合表现形式多样 ,以及“基质” +“岩块”的图面效应 .它的识别对地质填图。

A variability unconformity is initially proposed between the Bulun Formation of Lower Triassic and the underlying Upper Paleozoic after the systematic analysis of 1∶50?000 geological mapping and the comprehensive research into the geologic structure in Zhongdian region, northwestern Yunnan Province, China. This variability unconformity, a kind of stratigraphic contact relationship that occurred in the continental extension environment, shows the following principal distinguishing features: the strong undulating regional unconformity surface; the extensional structure of the underlying basement and the basalt in the continental extension environment; the marked change in the thickness of the overlying deposits and the abrupt change in the lithofacies; the diversity in the unconformity form, and the particular image effect of “matrix” + “rock mass”. The distinction of the variability unconformity from other unconformities is especially significant for the research into the geological mapping, geological structural evolution, and the time_space transformation in the tectonic movement.