内蒙古东乌旗巴彦塔拉盆地新近纪沉积物中粘土矿物特征与古气候指示意义

Clay Mineralogy and Its Paleoclimatic Indicator of the Neogene Sediments of the Bayantala Basin, DongwuQi, Inner Mongolia

摘要: 通过对内蒙古东乌旗巴彦塔拉盆地新近纪钻孔的系统研究，建立了本地区新近系地层的基本格架，对钻孔中所取的粘土矿物样品进行X射线衍射分析，并根据样品中粘土矿物的成分、质量分数对盆地古气候的演化进行探讨。通过对巴彦塔拉盆地内新近系地层的综合研究表明：盆地内发育较完整的新近系中新统通古尔组(N1t)和上新统宝格达乌拉组(N2b)地层；新近纪中新世，粘土矿物组合以蒙脱石、高岭石、伊利石为主，绿泥石仅在局部层位出现，含量较少，该时期盆地古气候变化总体上是由湿热向干冷逐渐变化；新近纪上新世早期，粘土矿物组合为蒙脱石和高岭石，并且含量同时升高，反应了总体气候由干冷向湿热的转变；新近纪上新世中晚期，粘土矿物组合为伊蒙混层和高岭石，高岭石含量呈递减趋势，伊蒙混层矿物含量呈递增趋势，表明上新世气候逐渐转为干旱，总体环境为干旱–半干旱环境。

Abstract: By systematically studying the Neogene drilling in the Bayantala Basin, DongwuQi, Inner Mongolia, the basic framework of Neogene strata in this area was established. The X-ray diffraction was analyzed from the clay mineral samples taken from the drilling, and according to the composition and mass fraction of clay minerals in the sample, the evolution of the paleoclimate of the basin was discussed. A comprehensive study of the Neogene strata in Bayantala Basin shows that the newly developed Miocene Tongguer Formation (N1t) and the Pliocene Baogedawula Formation (N2b) strata were well-developed within the basin; In Miocene Epoch, montmorillonite, kaolinite, and illite are the main components of clay minerals, while chlorite only occurs in local strata, and the content was relatively small. In this period, the paleo-climatic change in the basin generally changes from hot-humid to dry-cold; In the early period of the Pliocene, the clay minerals were composed of montmorillonite and kaolinite, and their contents increased at the same time, reflecting the transition of the overall climate from dry-cold to hot-humid; in the middle and late stages of the Neolithic Pliocene, the clay minerals were mixed with Ehmon and The content of kaolinite and kaolinite showed a decreasing trend. The content of the minerals in the mixed layer of Elemene showed an increasing trend, indicating that the Pliocene climate turned to be arid and the overall environment was arid to semi-arid.