黄骅坳陷歧口凹陷古近系层序地层格架及其特征分析

以经典层序地层学为指导,利用先进的解释系统,通过井—震互动反馈,从层序划分原则入手,对一级、二级、三级层序和体系域界面特征和识别标志进行研究,提出了该地区的层序划分方案。将该地区古近系地层划分为1个一级层序、3个二级层序和11个三级层序。一级层序和二级层序是构造层序,对应于不同级别的构造运动;三级层序是由盆缘不整合面及与其对应的盆内整合面所限定的地层单元,在盆地范围内可追踪对比。研究区内主要发育同生断裂坡折带和挠曲坡折带,这两种坡折带引起沉积斜坡明显突变,控制着坡折带两边的层序和砂体的发育。最终建立了两种坡折带与沉积体系配置关系,指出坡折带下部是低位砂体的有利发育带。

Sequence Stratigraphic Framework and Characteristics of Palaeogene in the Qikou Sag, Huanghua Depression

In order to understand stratigraphy characteristics and contact relationship,it's necessary to establish sequence framework of Palaeogene in the Qikou Sag.On the basis of the theory of sequence stratigraphy,sequences are subdivided and the boundaries of different orders of sequences are discussed.The sequence framework for different orders of stratigraphic successions in the Palaeogene has been established with an integrated analysis of seismic,logging and core data.The Palaeogene consists of 1 first-order,3 second-order sequences and 11 third-order sequences in the Qikou Sag.First-order and second-order sequences are tectonic ones,which correspond to tectonic movements.Third-order sequences are bounded by unconformities at basin margin and conformities in basin center.And third-order sequences can be identified in the whole basin.By the studies,it is proposed that the abrupt change of the depositional slopes resulting from the structural slope break zone or flexure slope break zone,has an important effect on the accommodation and sedimentation in the basin.The structural slope break zone or flexure slope break zone controls the development of the sequence and the lowstand sand bodies.Two models of slope break zones and sequences have been established and the areas below the slope break zones are favorable for the deposition of lowstand sand bodies.