Abstract: Based on the observation of cores and thin sections,as well as the detailed survey of outcrops,the ramp mound-shoal complexes of the Lower Cambrian Xiaoerbulake Formation of Tarim Basin can be divided into four types:grain beach,mound shoal,shoal flat,and platform inner flat,in accordance with their differences in geomorphology,sediment category,and sedimentary features.The grain-beach type complex,occurring in relatively flat platform settings in the Tazhong-Badong area,is characteristic of high-energy oolites and intraclastic grainstones growth in slices.The mound-shoal type complex,occurring in ramp settings in the Keping-Bachu area,is characterized by the prosperity of microbial mounds and algae-intraclastic grainstone shoals,displaying a feature of large shoals interspersed by small mounds.The shoal-flat type complex usually occurs in Aksu area with absence of microbial mounds and widespread grain beaches and tidal flats.The platform-inner-flat type complex is developed in the Lunnan-Yaha area,characterized by "isolated platform" with a steep eastern slope (filled with high-energy mound shoal deposits) and a relatively gentle western slope (dominated by low-energy microbial mounds or mats).Reservoirs in different mound-shoal complexes developed distinctive features.The grain-beach and shoal-flat types usually develop Type Ⅱ reservoirs with consistent distribution over large areas; while the mound-shoal and platform-inner-flat types tend to develop Type Ⅰ reservoirs,which are blocky and high-quality reservoirs,and may distribute in a large scale.In conclusion,lithologic traps should be a focus of exploration in the Tazhong-Badong area.While much attention should be paid to those tectonically stable traps with good preservation conditions in the Keping area,the high-energy mound-shoal complexes should be the exploration target in the Lunnan-Yaha area.

Key words: grain beach, mound shoal, shoal flat, platform inner flat, mound-shoal complex, ramp, Xiaoerbulake Formation, Tarim Basin