济阳坳陷伸展背景下的变换构造研究

Research on the Extensional Transfer Structures in the Jiyang Depression

济阳坳陷新生代盆地形成过程中经历了剧烈伸展断陷、构造沉降等,由于基底物质结构的差异、先存断裂的诱导以及块体的非均匀伸展变形作用等,形成了类型多样的伸展变换构造来调节盆地内部的伸展变形作用,使盆地在物质、空间上趋于守恒。济阳坳陷发育郑店-商河、阳信-石村、车西-罗西-陈南、埕南-孤西等4个一级变换构造带,主要受NW向基底隐伏断裂控制,走向与盆地轴向直交,调节了整个坳陷的伸展量变化,并分隔了两侧的构造单元和沉积体系,使济阳坳陷整体上呈现出"南西-北东分区"的结构特征。此外,发育有12种二级变换构造,受控于盆地内部的控凹断层,主要调节各凹陷内局部块体的伸展量,形成斜向凸起、走向斜坡以及地垒凸起等,往往成为地表水系的分水岭,在较陡一侧有利于水系的汇聚,形成冲积扇、近岸水下扇等沉积,砂砾岩体比较发育,成为油气聚集的有利区带。

Extensional transfer structure is one of important structural styles in the Jiyang depression. The gravity distribution and well data show that the thickness of the basement varies in different areas, which is the material base of transfer structure. The NW Mesozoic faults distribute along the thin basement zone where the stress usually focused, leading to the transfer structures to accommodate Cenozoic extension. In addition, the uneven deformation of different blocks in local area is the driving force. There are Zhengdian-Shanghe, Yangxin-Shicun, Chenxi-Luoxi-chennan, Chengnan-Guxi regional transfer structures in the Jiyang depression. The four zones are dominated by the hidden NW faults which are perpendicular to the basin axis and accommodate extension of the whole depression. Owing to its ＂segmentation＂, the structure features and sediment systems are divided, and the basin shows the new distribution feature from NW to SE. Based on the attitudes and contact relationships of the dominate faults, twelve kinds of secondary transfer structures have been identified, occurring as relay ramps, cross relief and graben. The secondary transfer structures mainly accommodated the extension of local blocks and resulted in the throw change of dominate faults, where the drainage system flew into the lake and formed alluvial fan and near shore subaqueous fan, which is favourable for hydrocarbon accumulation.