晚更新世以来地层的形成受气候、构造活动的影响,并记录其过程。因此,建立晚更新世以来的地层序列,对于气候变化、活动构造、地貌成因等研究十分重要。若尔盖盆地位于青藏高原的东部边缘,中国季风区和青藏高原区的交会地带,对气候变化敏感,构造活动也很强烈,建立盆地晚更新世以来的地层序列可以促进气候变化、构造活动研究。根据若尔盖盆地的湖相钻孔、泥炭矿、河流阶地和探槽等揭露的26个典型地层剖面,结合14C和OSL等测年方法获得的200多个同位素年龄,对晚更新世以来的地层进行对比和划分,得到地层综合柱状。晚更新世中期以来划分6个沉积韵律(75~55kaBP,55~33kaBP,33~20kaBP,20~11kaBP,11~4kaBP,4~0kaBP)和6个标志层(75~55kaBP和22~20kaBP的粉细砂层,13~9kaBP的青灰色粉细砂或灰—青灰色砾石沉积,5~4kaBP、3.5~2kaBP、0.5~0.3kaBP的黑色含炭质砂质黏土沉积)。沉积序列和构造-气候关系紧密,一方面沉积韵律与气候旋回基本吻合,与深海氧同位素阶段有较好的对应关系;另一方面,沉积层岩性特征也受到北侧的东昆仑断裂带和西侧的龙日坝断裂带新构造期持续活动的影响,沉积过程主要受气候控制,地层厚度及其空间分布的差异也受到构造活动影响。
Since stratigraphic formation is influenced by tectonic activities and climate since late Pleistocene,it is important to build the stratigraphic sequence to improve the research of active tectonics,climatic change and landform factors. Zoige Basin is located in the eastern edge of Tibet Plateau where the tectonic is active and the Chinese monsoon is strong. The research of stratigraphic sequence is closely related to the tectonic activities and climate changes. Based on 26 typical stratum profiles revealed by lacustrine boreholes,terraces,peat deposits and trenching,203 isotope dating data were obtained by AMS and OSL methods. We conduct a stratigraphic correlation and classification in Zoige Basin since the Late Pleistocene. Sedimentary cycles are divided into six sedimentary rhythms( 75 ~ 42 ka,42 ~ 37 ka,37 ~ 20 ka,16 ~ 11 ka,11 ~ 4ka and 4 ~ 0ka) and six marker beds( fine sand of 75 ~ 55 ka and 22 ~ 20 ka,gray silt deposit or gravel deposit of 13 ~ 9ka,black sandy clay containing carbonaceous deposits of 4ka,2ka and 0. 3ka).There is a close relation between strata and tectonic-climate. On the one hand,sedimentary cycles coincide with climate change and have a good correspondence with ocean oxygen isotope. On the other hand,sedimentation characteristics is influenced by the persistent activities in neotectonic period of the east Kunlun fault zone on the north side and the Longrize fault zone on the west side.Marker beds and sedimentary cycles are compared with the strata in adjacent areas. It shows that climate change is the main factor affecting sedimentary cycle. The difference of stratum thickness and its spatial distribution is also affected by tectonic activity.