川中—川南过渡带嘉陵江组二段沉积相及其展布特征

川中—川南过渡带下三叠统嘉陵江组划分为局限台地相、蒸发台地相、开阔台地相3个相,8个亚相(开阔潮下、台内滩、台内雏滩、局限潟湖、台内洼地、局限潮坪、蒸发潟湖、蒸发潮坪)和18个微相。区域上嘉陵江组二段纵、横向沉积相对比结果表明:嘉陵江组二段沉积相横向上较均一、相变化较小;沉积相垂向上变化在较大范围内具有同步性。嘉二段共分5个作图单元,采取单因素法和优势相法相结合,并融合了层序地层学研究成果,较精确地展示了嘉陵江组二段不同层段的沉积相展布和演化。相对海平面升降变化和碳酸盐台地内隆坳相间古微地貌共同控制着沉积相带展布和演化。嘉陵江组二段以局限台地相和蒸发台地相为主,储集体有利发育相带是台内雏滩亚相和局限潮坪亚相,台内雏滩发育于潮坪与潟湖的过渡区附近相对高能带,局限潮坪则分布广泛。

Sedimentary facies of the Second Member of the Jialingjiang Formation in the central-southern Sichuan transition zone and its distribution characteristics

The Lower Triassic Jialingjiang Formation in the central and southern Sichuan transitional zone may be divided into three facies(restricted platform, evaporative platform and open platform), eight subfacies (open subtidal zone, intraplatform bank, intraplatform embryonic bank, restricted lagoon, intraplatform shallow, restricted tidal flat, evaporative lagoon, evaporative tidal flat) and 18 microfacies. Regional correlation of vertical and lateral sedimentary facies of the 2nd Member of the Jialingjiang Formation indicates that laterally the sedimentary facies of the member are homogeneous and less varied, while vertically the sedimentary facies variation shows synchroneity in a vast areal extent. The 2nd Member of the Jialingjiang Formation is divided into five mapping units. By using the method of combining the single factor analysis and dominant facies method and the outcomes of sequence stratigraphic research, the paper relatively accurately exhibits the distribution and evolution of sedimentary facies of different facies of the 2nd Member of the Jialingjiang Formation. The relatively sea-level change and the microgeomorphology of alternating uplifts and depressions in the carbonate platform together control the distribution and evolution of sedimentary facies. The 2nd Member of the Jialingjiang Formation consists predominantly of restricted platform and evaporative platform facies. The facies belts that are advantageous to the formation of reservoirs are intraplatform embryonic bank and restricted tidal flat subfacies. Intraplatform embryonic banks are developed in relative high-energy zones near the transitional zone between tidal flats and lagoons. Restricted tidal flats are distributed widely.