川北地区中三叠统层序地层学的对比研究表明,雷口坡组顶界面(T2/T1界面)和底界面(T3/T2界面)具有横向分异规律,由此识别出2个Ⅲ级层序,其上部SQ2层序普遍缺失高水位体系域.层序地层格架内的岩相古地理分析表明,该区中三叠世长期处于蒸发台地、局限台地环境,碳酸盐岩颗粒结构欠发育,可见少量藻屑颗粒灰岩和白云岩、细-中晶白云岩,缺少生物礁标志,藻席大量发育,白云石化作用强烈.识别出了工农镇剖面斜坡角砾,并对台地边缘位置进行了厘定.根据沉积及岩石学研究结果,得出了川北地区中三叠统典型的陡坡封闭型镶边台地模式.

The characteristic correlation of sequence stratigraphy has indicated that there isa differentiation regulation in lateral at the top surface (the T2/T1) and the bottom surface (the T3/T2) of Middle Triassic Leikoupo Formation in lithology in northern Sichuan Basin. Therefore, two芋-order sequences are identified, in which the high-level system tract (HST) is generally absent in SQ2, the upper subsequence. Based on analysis of lithofacies palaeogeography in theⅢ-order sequence stratigraphic framework, it is shown that the environments of evaporative carbonate platform and restricted platform was dominant for a long time during the middle Triassic epoch in northern Sichuan Basin so that the underdeveloping carbonate grain textures indicate lack of mark of reefs but abundant algal mats, which results in existence ofa little algal-clastic grainstone and dolostone and fine-to medium-crystalline dolostone. A sort of slope facies breccia is recognized at Gongnong Zhen outcrop. The location of platform margin is confirmed. According to the research results of sedimentology and lithology, a typical model of Middle Triassic steep-sloped enclosed rimmed platform Facies in epicontinental sea iss recommended for the northern Sichuan Basin.