【摘要】 基于在鄂尔多斯盆地与其北部造山带地域,即沿延川—包头—满都拉地带进行的地震宽角反射和折射波场探测,取得了高分辨率的Pg波震相.通过走时差分层析成像方法进行Pg波波场走时反演,给出了沿剖面辖区的上地壳速度分布,求得了沉积建造和结晶基底折射界面的起伏变化,并给予了解释.研究结果表明,鄂尔多斯盆地上地壳为双层结构,上下层之间存在明显的折射界面,上层速度低,纵向变化梯度大;下层速度高,变化较为均匀.基于沿剖面辖区上地壳的速度分布特征提出自南向北应分为:榆林南凹陷、榆林—刀兔隆起、刀兔北至鄂尔多斯北缘断裂为箕形凹陷及其内部的次级构造、呼包凹陷以及伴随的断裂等沉积建造和结晶基底的起伏变化.阴山造山带上地壳速度明显比两侧地区高,速度呈纵向条带状展布,故呈现出结晶基底结构的分布特征和乌拉山、色尔腾山、和教岩体及白云鄂博群陆壳拼合及增生现象.内蒙造山带上地壳亦为双层结构,但基底折射界面不如鄂尔多斯块体明显.本文基于对该区沉积建造和结晶基底的起伏,讨论了沿剖面各有关凹陷的沉积特征与油气前景.更多还原

【Abstract】 Along the line Yanchuan-Baotou-Mandela in the Ordos basin and adjacent Yinshan mountainous area in the north China,a wide-angle reflection and refraction seismic sounding has been carried out yielding Pg wave data of high resolution.By the traveltime differential tomographic imaging,traveltime inversion of the Pg wave field is performed to determine velovity distribution of the upper crust,and undulation of sedimentary formation and crystalline basement along the profile.And geological interpretation to these features is made.The result shows that the upper crust below the Ordos basin is of a double-layer structure,with a distinct interface between the upper and lower layer.The upper layer is characterized by low velocity and big gradients in vertical direction,while the lower layer has high velocity and changes gently.In the light of the velocity distribution in the upper crust of the study area,it is suggested that the sedimentary formation and crystalline basement undulate in NS direction,generating a series of rising and falling structures.From south to north,they are the depression south to Yulin,Yulin-Daotu swell,listric depression from northern Daotu to the fault on the northern edge of Ordos and secondary structure in it,and Hohhot-Baotou depression and its interior faults.In the north,seismic wave velocity in the upper crust beneath the Yinshan Mountains(Mt.) is obviously higher than that below the areas on the both sides,exhibiting a pattern of longitudinal belt.It reflects the feature of the crystalline basement of this area,which is associated with collage and accretion of several blocks such as the Wula’er shan Mt.,Se’erteng double-layer structure,though its refraction interface of the basement is not so clear as that below the Ordos basin.Based on the structures of sedimentary formation and undulation of the crystalline basement of the study area,we have discussed the sedimentary features and hydrocarbon prospects of every depression along the profile.更多还原