伊通盆地新近纪以来的反转构造特征

郯庐断裂带于新近纪以来呈现强烈的挤压和逆冲活动,使伊通盆地相应地遭受了挤压而反转,盆地西北缘和东南缘地层被强烈抬升和剥蚀并形成逆冲断层、断褶带及断隆带等一系列反转构造。反转构造在盆地西北缘和东南缘具有显著差异性:在盆地西北缘形成宽2～4km的断褶带,该带可能是一个新的油气勘探领域,具备良好成藏条件,油气勘探重点应在褶皱带浅层和逆冲断层下盘;在盆地东南缘尖山和万昌等构造带则形成拱张性断隆带,对早期形成的油气藏起破坏作用,应该寻找深层和构造带斜坡部位的油气藏。反转构造的成因主要为太平洋板块向西俯冲产生的弧后扩张作用及印度洋板块向欧亚板块碰撞的远程挤压作用,还与盆缘刚性块体隆升及侧向挤压作用有关,盆缘刚性块体的分布位置及隆升强度对盆地反转构造的平面展布特征及反转强度具有重要影响。

Characteristics of inversion structures in Yitong Basin since Neogene

The Tan-Lu fault zone experienced intensive compression and thrust since Neogene. The Yitong Basin was also subjected to compression and inversion under the action of compression and thrust. The strata at the northwestern and southeastern edges were apparently uplifted and denudated. Many inversion structures such as thrust fault, faulted folds and faulted uplifts were developed. There is great difference between the inversion structures in the northwestern edge and southeastern edge. A fault-fold belt of 2~4 km in width formed at the northwestern edge. This belt has the good conditions for hydrocarbon accumulation and may be a new area for oil and gas exploration. The shallow level of faulted folds and the footwall of thrust faults are the important areas for hydrocarbon exploration. The inversion structures of the extensional faulted uplifts mainly formed in the Jianshan and Wanchang structural belts of the southeastern edge and could destruct the preexisting hydrocarbon pools. So, the deep level and the slope of structural belt such as Jianshan and Wanchang structures are the important area for hydrocarbon exploration in the southeastern edge. The thrusting activity of the Tan-Lu fault zone and the inversion structures of the Yitong Basin took place in the regional dynamic setting. The back-arc spreading caused by westward subduction of the Pacific plate and the extrusion from the Indian plate collision with eurasian plate also played a partial role in the east-western compression of East China. The distribution and uplift strength of the rigid plates in the basin edge played a great role on the distribution and inversion strength of inversion structures in Yitong Basin.