川南柏香田地区早志留世石牛栏组风暴沉积的发现及意义

通过野外实测剖面和镜下薄片观察，于通过野外实测剖面和镜下薄片观察，在川南柏香田剖面早志留世石牛栏组下部发现一套风暴沉积，具有侵蚀底面、砾屑层、粒序层理、丘-洼状交错层理、沙纹层理以及风暴与平静天气形成的沉积物互层等风暴沉积特征。理想风暴沉积序列由6个沉积单元组成，根据剖面不同沉积单元间的排列组合，将其划分为4种风暴沉积序列，各序列间存在一定继承性，由下向上表现为远源型风暴向近源型风暴的转变、风暴强度逐渐增强的过程。结合更靠扬子东南缘的深水剖面重力流沉积的缺乏，可以推断早志留世石牛栏期研究区的沉积模式为碳酸盐缓坡。结合风暴的形成机制以及石牛栏组风暴沉积的发育特征可知（尤其是正粒序层理和典型丘状交错层理）：研究区早志留世处于中低纬度的古地理位置，可为上扬子区古气候及古扬子海盆演化提供依据；上扬子区早志留世同期异相地层存有争议，风暴沉积特征为石牛栏组、小河坝组、罗惹坪组等地层提供等时性对比标尺；川南早志留世石牛栏组沉积环境意见不一，风暴沉积为其碳酸盐岩缓坡环境提供证据资料。通过总结前人对风暴岩物性认识，结合上扬子区同期地层油气地质条件，可提供油气勘探新途径。川南柏香田剖面早志留世石牛栏组下部发现一套风暴沉积，发育侵蚀底面、砾屑层、粒序层理、丘-洼状交错层理、沙纹层理以及风暴与平静天气形成的沉积物互层等风暴沉积特征。理想风暴沉积序列由6个沉积单元组成，根据剖面不同沉积单元间的排列组合，将其划分为4种风暴沉积序列，各序列间存在一定继承性，由下向上表现为远源型风暴向近源型风暴的转变、风暴强度逐渐增强的过程。结合更靠扬子东南缘的深水剖面中重力流沉积的缺乏，可以推断早志留世石牛栏期研究区的沉积模式为碳酸盐缓坡。结合风暴的形成机制以及石牛栏组风暴沉积的发育特征可知（尤其是正粒序层理和典型丘状交错层理）：研究区早志留世存于中低纬度的古地理位置，可为上扬子区古气候及古扬子海盆演化提供依据；上扬子区早志留世同期异相地层存有争议，风暴沉积特征为石牛栏组、小河坝组、罗惹坪组等地层提供等时性对比标尺；川南早志留世石牛栏组沉积环境意见不一，风暴沉积为其碳酸盐岩缓坡环境提供证据资料；总结前人对风暴岩物性认识，结合上扬子区同期地层油气地质条件，提供油气勘探新途径。

Discovery and significance of the storm deposit within the Early Silurian Shiniulan Formation in the Boxiangtian area, south Sichuan

Based on the outcrop measurement and indoor identification to the Shiniulan Formation in southern Sichuan,it has been found that there is one set of storm deposit in the Early Silurian Shiniulan formation in the Boxiangtian section, southern Sichuan.We found many sedimentary structures,such as erosion surface,storm flow-generated gravelstones,graded bedding,hummocky and swaley cross-stratification,ripple bedding,and sediment interlayer formed by storm and calm weather.Sedimentary structures in different conditions can form different storm sedimentary sequences.Combined with previous studies, the ideal sequence of storm deposits is divided into 6 sedimentary units,and further analysis of the Boxiangtian section shows that it has four types of storm sedimentary sequences, with succession between them.From the bottom to the top, the storm deposits change from the distal storm deposits to the near storm deposits, and the storm intensity increases gradually. The discovery of storm deposits shows that the early Silurian in the study area is located in the middle and low latitudes, which provides the basis for the paleoclimate and the evolution of the ancient Yangtze Basin in Upper Yangtze Region; The early Silurian contemporary heteropical in the Upper Yangtze area are controversial.The characteristics of storm deposits provide isochronal correlation scales for the strata of Shiniulan Formation, Xiaoheba Formation and Luoreping Formation; There are different opinions on the sedimentary environment of the Shiniulan Formation of the Early Silurian in southern Sichuan. Storm deposits provide evidences for the gentle slope environment; We summarized the predecessors'' understanding of tempestite physical properties, Combining with the petroleum geologic conditions of the strata in the same period in the Upper Yangtze area, a new way of petroleum exploration is provided.