黄骅坳陷港中地区沙二段高分辨率层序地层格架与沉积体系分布

摘要

Based on Cross T.A. genetic sequence stratigraphy theory and through a variety of data analysis, the Shahejie formation is divided into 5 long term cycles, 10 middle term cycles and 41 short term cycles. The Second member of Shahejie formation includes 1 long term cycle, 3 middle term cycles and IS short term cycles. The main sequence structure of long term cycle is C-symmetrical structure which becomes darker up and then lighter, and the main sequence structure of middle and short term cycle is A-symmetrical structure which becomes lighter up or B-symmetrical structure which becomes darker up. Identified Shahejie Formation is developed into 3 types of sedimentary facies, i.e. subaqueous fan, gravity flow channel and lake sediments, including 11 microfacies. In MSC3 and MSC4 period, provenance is mainly from the Gangxi Ancient raised, MSC3 period, provenance direction is from the single West into an integrated provider of multi-source direction. The sufficient source supply is the primary factor of the development of gravity flow channel. The staged broken-off slots is the major control factor of the distribution of braided gravity flow channel.%应用T A.Cross高分辨率层序地层学理论,并综合运用地震、测井、岩心和分析化验资料,将港中地区古近系沙河街划分为5个长期基准面旋回、10个中期基准面旋回和41个短期基准面旋回.其中重点层位沙二段包括1个长期基准面旋回、3个中期基准面旋回和15个短期基准面旋回.长期旋回层序结构类型以向上变深再变浅的对称的C型结构为主,中短期旋回层序结构类型是以向上变深的A型或向上变浅的B型非对称型为主.识别出古近系沙二段主要发育3种沉积相类型:近岸水下扇、重力流水道和湖泊沉积,包括11种沉积微相;沙二段MSC3和MSC4时期,物源主要来自于西部的港西古凸起,至MSC5时期,物源方向由单一西部方向转为多方向物源供应.辫状重力流水道全都发育在近岸水下扇的前方,充足的物源供应是重力流水道发育的首要因素;辫状重力流水道的发育及分布与沉积期的古地貌有关,而断阶式断槽是港中地区古地貌的主要特征,因此,断阶式断槽是控制沙二段辫状重力流水道分布的主要因素.