潜江凹陷潜北地区潜四下段盐湖层序控制因素及层序模式

Controlling Factors and Sequence Models of the Lower 4^(th) Member of Qianjiang Formation in Northern Area of Qianjiang Sag

江汉盆地潜江凹陷潜江组为一典型的陆相盐湖沉积,其中潜四下段盐岩沉积最为发育,盐岩层最厚达1500m。目前关于盐湖层序地层划分及分析研究成果较少,未形成有效的层序模式。以潜四下段为研究目的层段,依据钻井、测井和地震资料,分析了盐湖盆地层序、沉积控制因素及形成模式。研究认为,气候对潜四下段沉积时期的层序发育控制较弱,主要受古构造形成的古地貌及物源供给的影响,潜四下段粉砂岩与蒸发岩呈现"此消彼长"的分布关系。根据潜北地区潜四下段盐岩在层序发育中的地位和作用,将各层序内部划分为湖侵体系域(TST)及湖退体系域(RST),同时提出断坡带层序模式和挠曲带层序模式两种层序模式。

Qianjiang Formation of Qianjiang Sag in Jianghan Basin is a typical continental salt lake deposit. Salt rock sedimentation developed most in the lower fourth member of Qianjiang Formation （Eq4x） with a thickness of 1500 meters. Currently, there are few results for analysis and study related to stratigraphic division of salt rock sequences. No effective sequence model was established. The study targeted at the Eq4x deposit is based on the cores logs and seismic data, which analyzed stratigraphic sequences of salt-lake basin, controlling factors of deposit and development model. According to the study, the sequential development of the Eq4x deposit was less controlled by the climate during the sedimentary period while paleotopography and sedimentary source recharge exerted main influence on the deposit. Siltstone and evaporite were distributed in the Eq4x deposit. The sequences of the Eq4x can be divided into transgressive system tract （TST） and lake regressive system tract （RST） according to the position and role of salt rock in the sequential development of the Eq4x deposit in the northern area of Qianjiang Sag. Meanwhile, two sequence models were put forth -- fault slop-break model, flexure slop-break model.