【作者】 韩鹏；

【导师】 刘池阳；

【作者基本信息】 西北大学 ， 构造地质学， 2008， 硕士

【摘要】 宁南盆地群主体位于宁夏南部,现今不具盆地形态,为经过后期改造残留的沉积体。展布范围泛指银川盆地之南第三纪地层集中广泛出露和分布地区,其主要为大面积红色地层,且分布零星,无固定规律。其地理和大地构造位置重要,东接中生代鄂尔多斯盆地西南缘,与鄂尔多斯地块周缘诸新生代断陷盆地遥相呼应,西接青藏高原东北犄角部位,是青藏高原隆升最直接的响应。故其发生演化和消亡历程的研究,对鄂尔多斯盆地新生代改造及其区域动力学环境及演变,中生代原盆地恢复,该地区进一步油气勘探,及青藏高原隆升的环境效应,具有重要的、不可替代的意义。前人对宁南地区新生界做了许多探索性的研究,但研究时代比较局限,研究内容相对简单,对于该盆地的形成演化和后期改造,特别是新生代盆地形成的区域动力学环境和构造属性涉及较少,尚有一系列关键问题有待进一步研究解决。因此对盆地三条典型剖面进行了实测,并结合80天的野外踏勘探明了盆地现今第三系分布状况和地层特征、前第三系分布特征及与第三系接触关系规律,并绘制成图。同时本论文利用古地磁方法,问隔0.3—0.5m采样,并通过系统热退磁建立磁性序列得出盆地新生代第一套沉积寺口子组记录了15个正极性和14个反极性,沉积年龄为47.906Ma—29.401Ma。另外分析了鄂尔多斯盆地及周缘构造单元上多个裂变径迹和周缘盆地孢粉的研究成果并配以实测剖面来探讨新生代宁南盆地群的构造和演化,结合鄂尔多斯周缘其他新生代断陷盆地的发生时间,地层特征及构造属性和特征来探讨整个鄂尔多斯及周缘盆地的演化和响应关系。结合鄂尔多斯盆地周缘山脉的抬升及盆地东西反转时间初步认为鄂尔多斯盆地与周缘新生代断陷盆地有着很好的响应关系,鄂尔多斯周缘新生代的断陷盆地断陷具有同时性,以河套盆地和渭河盆地于古新世局部断裂为最先,随后始新世整个盆地周缘开始大面积发育。更多还原

【Abstract】 The Ningnan Basin Group, mainly located at the south of Ningxia province, is the sediment after the late reformation without basin shape. The spread scope generally refers to the Tertiary strata that are massively uncovered and distributed to the south of the Yin Chuan basin. Most of the strata is red, scattered and ruleless. It has important significance for its special status of geography and tectonics. The residual basin adheres to the southwest of the Mesozoic Ordos basin to the east and the northeastern horn of the Tibet Plateau to the west, which correspond with the Cenozoic faulted basins in the neighboring area of the Ordos basin from afar, and is the most immediate response to the uplift of Tibetan plateau. Hence, the study on the formation, evolution and disappear of the Ningnan Basin Group is crucial and irreplaceable to the Cenozoic reformation and the regional geodynamic environment of the Ordos Basin, the recovery of original Mesozoic basin, the oil-gas exploration in this area, and the uplift of Tibetan plateau.Many predecessors make exploratory research on the Cenozoic in Ningnan area, but the age their studied is limited, so the work is exploratory and very simple, rarely concerning formation, evolution and late reformation of the basin, especially the regional geodynamic environment and tectonic attribute of the Cenozoic basin. There are a series of problems should be resolved, still.Through high-resolution test about three typical sections and 80 days’ field reconnaissance, the current distribution and tectonic characters of the Tertiary and Neozoic and the contact relation between each other are all explored.Based on the high-resolution sampling at the distance of 0.3-0.5m and systematic heating demagnetization, the regional magnetic sequence composed of 15 normal zones and 14 reversed zones is put forward. From the magnetic result, it is shown that the first sediment of Cenozoic Sikouzi Formation is in the range from 47.906Ma to 29.401MaB.R. In addition, many fission tracks on Ordos Basin and its neighboring tectonic units are analyzed. Combining with the spore-pollen findings and sections, tectonics and evolution of the Cenozoic Ningnan Basin Groups are discussed. In combination with the age, strata features and tectonic attribute of the other Cenozoic faulted basins around Ordos Basin, the evolution and response relationship between Ordos Basin and its neighboring basins are also discussed. The uplift period of the surrounding mountains and the reverse time of the east and west of Ordos Basin is worked out. It is revealed that the Ordos Basin have a very well response to its Cenozoic ambient faulted basins which are ordered and begins with the part of Hetao basin and Weihei basin, and the next is all the Ordos’ neighboring basins.更多还原