四川盆地须家河组层序分析与地层对比  

Sequence analysis and stratigraphic correlation of the Xujiahe Formation in the Sichuan Basin

作　　者：郑荣才[1] 李国晖[2] 雷光明[3] 李楠[2] 罗清林[3] 陈虎[4] 

机构地区：[1]"油气藏地质及开发工程"国家重点实验室.成都理工大学 [2]中国石油西南油气田公司勘探开发研究院 [3]川庆钻探工程有限公司地质勘探开发研究院 [4]中国石油西南油气田公司重庆气矿

出　　处：《天然气工业》2011年第6期12-20,121-122,共9页Natural Gas Industry

基　　金：国家科技重大专项"四川盆地岩性油气藏富集规律与目标评价"(编号:2011ZX05001-005)

摘　　要：长期以来,四川盆地上三叠统的须家河组与香溪群存在多种地层分区、划分方案和对比关系,为建立对须家河组进行区域地层划分、对比的统一标准,对该组进行了详细层序分析与地层对比。通过对层序界面和最大洪泛面的识别,将须家河组划分为分别代表"须下盆"和"须上盆"两个成盆期次的两个超长期旋回层序,细分成5个分别对应须二段—须六段的长期旋回层序和17个中期旋回层序。在分析各次级构造单元须家河组层序发育特征的基础上,建立了贯穿盆地东西向、南北向的等时地层格架,并对须家河组进行对比,发现地层格架中上超的超长期和长期层序界面具有很大的穿时性,而洪泛面具有良好等时性,是区域地层对比的最重要标志。地层分布明显受龙门山和米仓山—大巴山两条造山带非同步异方位逆冲推覆活动的控制,具有自盆地周边坳陷带向被坳陷带围绕的川中前陆隆起方向上超变薄的楔形充填特征。最后,建议废弃"香溪群"这一地层单元命名,使用沉积—层序划分方案作为对须家河组进行区域地层划分和对比的统一标准,以符合地层学原理。Various schemes of strata division and correlation exist in the Upper Triassic Xujiahe Formation and the Xiangxi Group in the Sichuan Basin at present.In order to establish unified standards for regional strata division and correlation of the Xujiahe Formation,a thorough and detailed sequence analysis and stratigraphic correlation are performed on this formation.Based on the recognition of sequence boundaries and maximum flooding surface,the Xujiahe Formation is divided into two super-long-term sequence cycles which represent the 'early Xujiahe' and the 'late Xujiahe' basin formation periods respectively,5 long-term cycles which correspond to the 2nd to 6th members of the Xujiahe Formation respectively,and 17 medium-term cycles.Based on an analysis of the sequence development characteristics of the Xujiahe Formation in structural units at each order,an isochronous stratigraphic framework is established crossing the basin from east to west and from north to south.The stratigraphic correlation of the Xujiahe Formation reveals that the onlapping super-long-term and long-term sequence boundaries in the framework show obvious diachroneity and the flooding surfaces show obvious isochronism,both of which are the most important markers for regional stratigraphic correlation.The strata distribution is significantly controlled by asynchronous overthrusting with different azimuths of Longmenshan and Michangshan-Dabashan orogenic belts,and show wedge filling characteristics of onlapping and thinning in the direction from the depression zone around the basin to the forebulge in the central of the Sichuan Basin.It is suggested that the previous stratigraphic unit of the 'Xiangxi Group' should be abandoned and the sedimentary-sequence scheme should be used as the unified standard for regional strata division and correlation of the Xujiahe Formation.

关 键 词：四川盆地 晚三叠世 层序地层学 基准面旋回 地层格架 等时对比 洪泛面 沉积-层序划分方案 

分 类 号：P618.13[天文地球—矿床学]