【摘要】 不同学者针对四川盆地上三叠统地层特征及沉积演化规律从不同角度进行了诸多研究,但各自获得的地质认识却存在一定的差异。为此,在地表露头和钻测井资料分析、地震层序分析的基础上,将四川盆地须家河组划分为2个超长期基准面旋回层序,为须上盆、须下盆2大成盆期的沉积响应;盆地周缘造山旋回变化是控制2大成盆期砂体分布的主导因素,纵向上总体具阶梯状分布特征,由坳陷中心向周边逐层超覆并阶梯状退积。须家河组主要为陆相河湖三角洲沉积体系,主要发育冲积扇—冲积平原—曲流河或辫状河三角洲—湖泊和冲积扇—扇三角洲—湖泊沉积体系模式。须下盆沉积体系受西低东高大型缓坡古地貌特征控制,总体具有不对称分布特点,湖盆中心位于川西坳陷中南段;前陆造山对须上盆沉积体系分布具有明显的控制作用,沉积体系呈近于对称的环带状分布,前陆隆起及湖盆东移,湖盆走向明显的受古龙门山控制。更多还原

【Abstract】 Many researchers have studied the stratigraphic features and sedimentary evolution patterns of the Triassic reservoirs in the Sichuan Basin.However,certain differences exist in their achieved geological understandings in this study area.Based on an analysis of outcrops,drilling and logging data,and seismic sequence,two super-long-term base level cycles are recognized in the Xujiahe Formation of the Sichuan Basin,which correspond to the sedimentary responses during the 2 basin-forming stages,i.e.the Late and the Early Xujiahe.The change of an orogenic cycle in the periphery of the basin is the major factor controlling the distribution of sandbodies deposited during these 2 basin-forming stages.Vertically,the sandbodies show step-like distribution,overlapping layers and retrograding step-wise outwards from the center of depression.The Xujiahe Formation is dominated by continental fluvial-and lake-delta sedimentary systems.The main sedimentary system models are alluvial fan-alluvial plain-meandering river/braided-river delta-lacustrine and alluvial fan-fan delta-lacustrine.The Early Xujiahe sedimentary system is controlled by a large ramp low in the west and high in the east and is asymmetrical as a whole,with the center of the lake basin occurring at the south segment of the western Sichuan depression.In contrast,the Late Xujiahe sedimentary system is significantly controlled by the foreland orogeny.It shows nearly symmetrical ring distribution.The eastward migration of the lake basin is due to the uplifting of the foreland and its trend is obviously controlled by the Longmenshan Mountain.更多还原