西秦岭峡城—晒经滩地区中三叠世碳酸盐台地古斜坡的识别及其古地理意义

 碳酸盐台地斜坡为位于碳酸盐台地和深海盆地之间一个坡折地带，这一环境中，重力作用控制了沉积物的沉积和变形，其研究具有重要的古地理和经济意义。峡城地区中三叠统发现大量碳酸盐碎屑流沉积及同沉积断层和削切构造，而晒经滩中三叠统古浪堤组复理石中同样有大量碳酸盐碎屑流沉积出现。为探索该区中三叠世的古地理环境特征，结合室内碳酸盐岩微相分析，从露头角度对它们进行了识别。对这些沉积物和沉积构造的分析研究表明，沿西秦岭峡城、晒经滩一线存在一个近SEE—NWW向展布的大陆斜坡，该斜坡在峡城地区主要以深水碳酸盐沉积为主，向NWW方向逐渐过渡为以陆源碎屑沉积为主，该斜坡向NNE为碳酸盐台地沉积，向SW方向则过渡为深海沉积。

Identification and Paleogeographical Implications of Middle Triassic Carbonate Slope in Xiacheng-Shaijingtan Area, West Qinling Mountains

The carbonate platform slope is a slope break zone between the carbonate platform and the deep-sea basin. The deposition and the deformation of sediments are controlled by gravity. Its study has important palaeogeographical implications and economic significance. A great number of carbonate debris flows, syndepositional faults and truncation structures have been found in Middle Triassic in Xiacheng. Also, carbonate debris flows exist in flysches of Middle Triassic Gulangdi Formation in Shaijingtan. In order to reconstruct the paleogeographical environment in this area, the carbonate microfacies are analyzed, with identifications and discussions. The analysis on these sediments and sedimentary structures reveals that a continental slope exists from SEE to NWW along Xiacheng—Shaijingtan in Middle Triassic. They are mostly deep-water carbonate sediments in Xiacheng and terrigenous clast in Shaijingtan. This slope is nearly a carbonate platform in NNE, and has a transition to deep-sea sediments in SW.