川东南—黔西北桐湾Ⅲ幕岩溶古地貌恢复

摘要

通过对川东南—黔西北灯影组露头、钻井岩芯的详细观察分析,认为灯影组中上部发育一系列的古岩溶标志,包括岩溶角砾岩、充填的溶洞溶缝、含铁质古风化壳等.在结合前人对上扬子桐湾运动研究的基础上,认为川东南—黔西北大部分地区由Ⅲ幕和Ⅱ幕叠加形成了寒武系与震旦系之间的平行不整合面.采用“印模法”恢复桐湾Ⅲ幕岩溶古地貌,“印模”为下寒武统“牛蹄塘组+明心寺组+金顶山组”;“印模”如果包括麦地坪组,“印模”底界将具明显穿时性.根据“印模”地层分布及古地貌指示,研究区岩溶古地貌主体呈南北向展布,具有东高西低的特征,东部发育岩溶高地,西侧为岩溶洼地,中部则发育岩溶斜坡.岩溶高地和岩溶斜坡可以进一步划分为残丘、平台以及上斜坡、下斜坡等次级岩溶古地貌单元.%Through the outcrops and core observation of the Dengying Formation in the Southeast Sichuan and Northwest Guizhou,it is considered that the upper dolomite of Dengying Formation had developmented a series of paleokarst identification,including karst breccias,karst caves and cracks filled,limonite weathering crust,and so on.Based on previous research on the upper Yangtze Tongwan movement,the parallel unconformity between Cambrian and Ediacaran was formed by movement of Episode Ⅲ and Episode Ⅱ in most areas.Moldic thickness methods are comprehensively used to restore the karst paleogeomorphy of Tongwan movement Episode Ⅲ,the moldic thickness include Niutitang Formation,Mingxinsi Formation and Jindingshan Formation,barring Maidiping Formation.Which has obvious diachronism.According to the instructions of moldic thickness and ancient landform,it is indicate that,karst palaeogeomorphology distributed from north to south,the East part was high,the West part was low.Karst highland was developed in the East part,karst depression was developed in the West part,and Karst Slope was developed in the Central part.Which can be furtherly divided into secondary karst palaeogeomorphology units,such as monadnock,platform and upper slope,lower slope.