四川盆地下中三叠统发育有多套盐层，具有多层系、厚度大、分布广泛、咸化—盐化旋回清晰的特点。目前对其沉积环境及岩相古地理的研究较多，但针对油气勘探相关的碎屑岩沉积，对于与蒸发成盐过程相关的亚相、微相研究不多。本文在前人研究的基础上，利用四川盆地上世纪找盐、找钾老井，新一轮盐、钾钻井及油气井资料，将四川盆地划分为五个成盐区，18个次级含盐盆地。以碳酸盐岩台地蒸发成盐环境为侧重点，根据沉积构造、生物特征、岩性组合，将四川盆地下中三叠统18种典型岩石类型进行了成因分类。认为其分别形成于开阔台地相—局限台地相—蒸发台地相等3种主要的沉积相，6种沉积亚相及13种沉积微相；进一步根据各成盐区沉积相展布，编制了嘉四2（T1 j 4－2），嘉五2（T1 j 5－2）～雷一1（T2 l 1－1），雷三2（T2 l 3－2）以及雷四2（T2 l 4－2）四个主要成盐期岩相古地理图，认为各成盐阶段沉积相带通常呈环带状分布，以盐湖微相为核心，具有“牛眼式”的岩相分布特点，四川盆地早中三叠世成盐模式可能属于“潮上带牛眼式干化小型盐盆（湖）成盐”。%The Low-Middle Triassic in the Sichuan basin contains several sets of the salt layers. The characteristics of the salt layers are thick, wide distribution and well-marked depositional cycles. Nowadays,the research of the sedimentary and the lithofacies palepgeography in Sichuan basin usually service for the oil and gas exploration.There is few research of the micro-phase related to the evaporation and salt-forming.On the basis of the previous studies and the information about looking for the salt, potash,oil,and gas,this paper divides the Sichuan basin into 18 secondary salt basins and 5 salt forming zones.By taking the carbonate platform as the emphasis,according to the sedimentary structure, biological characteristics and lithofacies associations,18 types rocks in the low-middle Triassic have been classified.They constitute 3 different sedimentary facies (open platform,restricted platform and evaporate platform),6 kinds of subfacies and 13 kinds of sedimentary microfacies.According to the sedimentary distribution of the salt layer,4 pieces of lithofacies paleogeographic map have been drawn in this paper, including 4 main period of the salt forming,T1 j 4-2 ,T1 j 5 -2 - T2 l 1 -1 ,T2 l 3 -2 ,T2 l 4-2 .The every sedimentary facies has the salt lake as the core and distribute as belt,with the form of the bull’s-eye type zoning.In summary,the salt-forming model of Sichuan basin in Early-Middle Triassic could be concluded as “the small playa lake with a bull's-eye type zoning in supratidal environment”.
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