Velocity distribution of upper crust, undulation of sedimentary formation and crystalline basement beneath the Ordos basin in North China
Velocity distribution of upper crust, undulation of sedimentary formation and crystalline basement beneath the Ordos basin in North China
复制标题
DOI：
10.1002/cjg2.1348
复制
发表时间：
2009
期刊：
影响因子：
--
通讯作者：
J. Teng;Fu-yun Wang;Wenqing Zhao;Jin-ren Zhao;Ming Li;Xiaobo Tian;Yafen Yan;Yongqi Zhang
中科院分区：
文献类型：
--
作者：
J. Teng;Fu-yun Wang;Wenqing Zhao;Jin-ren Zhao;Ming Li;Xiaobo Tian;Yafen Yan;Yongqi Zhang
在鄂尔多斯盆地的延川-包头-满都拉一线及北部阴山地区进行了广角反射折射地震测深，获得了高分辨率的Pg波资料。通过走时差分层析成像，对Pg波场进行走时反演，确定了剖面上地壳的速度分布、沉积建造的起伏和结晶基底的起伏。并对这些特征进行了地质解释。结果表明，鄂尔多斯盆地下地壳为双层结构，上、下两层界面明显。上层流速低，垂向梯度大，下层流速低，变化平缓。根据研究区上地壳的速度分布，认为沉积建造和结晶基底呈南北向起伏，形成了一系列的升降构造。自南向北依次为榆林以南的坳陷、榆林-道土隆起、道土以北至鄂尔多斯北缘断裂的铲状坳陷及其内部次级构造、呼和浩特-包头坳陷及其内部断裂。在北部，阴山下地壳上部的地震波速度明显高于两侧区域之下，呈纵向带状分布。它反映了本区结晶基底的特征，并与乌拉山等多个地块的拼贴色尔腾山，和角岩基、白云鄂博群。阴山下。上地壳也是双层结构，但其基底折射界面不像鄂尔多斯盆地之下那么清晰。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.
Along the line Yanchuan–Baotou–Mandula in the Ordos basin and adjacent Yinshan mountainous area in the north in 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 velocity distribution of the upper crust, 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 layers. The upper layer is characterized by low velocity and big gradients in vertical direction, while the lower layer has low 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 Mt., Hejiao batholith, and Bayan Obo group. Beneath the Yinshan Mt. the upper crust is also of a 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.