新疆阿克苏地区新元古代沉积特征对裂谷发育过程的指示

阿克苏地区地处塔里木克拉通西北部的盆-山结合部位，新元古代地层齐全且发育前寒武纪蓝片岩，保留了新元古代从洋壳俯冲汇聚到陆壳拉张伸展过程的记录，是近年塔里木新元古界研究的热点及重点地区。但阿克苏地区新元古代地层层序和沉积体系的研究较为薄弱，构造对沉积充填的控制作用仍不清楚，由此也制约着对塔里木克拉通初期裂谷发育演化的认识。本文综合地层学、沉积学等多种研究手段，分析阿克苏地区新元古代地层展布及垂向发育特征，将多处实测剖面与钻井-地震剖面结合，构建了阿克苏地区新元古代地层发育序列及空间对比格架。明确了由裂陷控制的沉积相类型及演化：南华纪巧恩布拉克组先后发育冲积扇/扇三角洲、水下-冰川亚相（冰碛岩）及深水陆棚相；尤尔美那克组，早期以陆上-冰川沉积为主，晚期以冲积扇沉积为主；震旦纪苏盖特布拉克组由冲积扇过渡到辫状河三角洲和潮坪相；奇格布拉克组以碳酸盐岩台地沉积为主。通过盆-山构造结合沉积序列分析，确定新元古代经历了三个构造-沉积演化阶段：（1）局限深裂谷发育阶段（南华纪），充填冲积扇/扇三角洲及深水陆棚相沉积，其中发育两期不同环境的冰川沉积；（2）裂谷扩张期（震旦纪早期），火山活动强烈，发育冲积扇-辫状河三角洲、潮坪相沉积；（3）坳陷发育期（震旦纪晚期），广盆浅海环境，发育碳酸盐岩台地。

The indication of Neoproterozoic sedimentary characteristics to rift development process in Aksu area, Xinjiang

The Aksu area is located in the basin-mountain jointed belt on the northwestern margin of Tarim basin. The Neoproterozoic strata, with Precambrian blue schist, are completely and well preserved in this area, which recorded the process from the oceanic subduction to continental extension during Neoproterozoic period. It is the vital area for the Neoproterozoic study in Tarim Craton in recent years. However, studies upon the Neoproterozoic stratigraphic distribution and sedimentary system in Aksu area is poor, and the tectonic control on its sedimentary filling process is still unclear, which restricts the understanding of the rift development and evolution in the early stage of the Tarim Craton. This study focuses on the stratigraphy and sedimentology of the Neoproterozoic strata in Aksu area, and analyzes their evolutionary characteristics. Combined with several outcrop profiles, wells and seismic profiles, we construct the Neoproterozoic stratigraphic correlation framework in Aksu area, through which the sedimentary facies and their evolutions controlled by the rift syestem are clarified: the Qiaoenbrak Formation developed in the alluvial fan/fan delta, submarine-glacial facies (tillites) and deep water shelf facies, successively; the Yuermeinak Formation was dominated by terrestrial-glacial facies in the early stage and alluvial fan in the late stage; the Lower Ediacaran Sugetbrak Formation transited from alluvial fan to braided river delta and tidal facies; the Upper Ediacaran Chigebrak Formation was dominated by carbonate platform facies. Combined simultaneous structural and sedimentary sequence analysis, we suggest that the Neoproterozoic experienced three stages of tectonic-sedimentary evolution, including: (1) restricted deep rift valley development stage during Cryogenian, fan dalta and deep water shlef facies developed, and two types of glacial facies in the different environments also developed; (2) rifting expansion stage during the Early Ediacaran, volcanic activities were intensely and alluvial fan-braided river delta and tidal-flat facies developed; (3) depression development stage during the Late Ediacaran, there were widely in shallow marine environment and carbonate platform developed.