This study carried out comprehensive analysis on sedimentology, magnetic susceptibility(χlf) and color data of the continental sediments of the Liupanshan Group in Central China so as to obtain climatic change information during the 129.14–122.98 Ma interval. Based on the results of the ?lf and of the redness(a*), the section can be divided into two segments:(1) 129.14–126.3 Ma, with the lowest ?lf values and strongly variable relatively high values of redness and(2) 126.3–122.98 Ma, with high ?lf values and relatively low redness. Analysis of the lithology and facies as well as the magnetic minerals and their contents points to a detrital origin of the magnetic minerals and this allow us to interpret the relationship between magnetic susceptibility variations and climate changes. Our study shows that the climate was significantly dry and hot during the whole studied interval although the interval between 126.3 Ma and 122.98 was a little bit cooler with increased humidity.
Tectonic and environmental patterns and evolution of the present North Tibetan Plateau(NTP) prior to the India collision with Asia is significant to understand the formation of the Tibetan Plateau and its influence on the environment. In this study, we integrated and analyzed the tectonostratigraphy and the special sedimentary layers whose climatic implications are clear in the NTP. Additionally, we stressed the tectonic and environmental events and their evolutions from the Mesozoic to the Early Cenozoic. Our results show that four tectonic phases, which sequentially took place during the Triassic, Jurassic, Cretaceous and Paleogene, played an important role on the formation of the North Tibet. The climate was basically dry and hot from the Triassic to the Eocene and became dry and cool since the Oligocene in this region. The climatic evolution was characterized by a transition from a wet and hot phase during the Triassic- Middle Jurassic, to a dry and hot phase during the Late Jurassic- Eocene. Both phases encompassed 5 wet and hot periods followed by 5 dry and hot climate events, respectively. In addition, we found that the tectonic deformation and the climatic conditions were spatially and temporally different. In detail, in the regions north of the PaleoTian Shan and Paleo-Qilian Mts. the tectonic deformation and climatic condition were stronger and wetter than in regions south of the Paleo-Tian Shan and Paleo-Qilian Mts. during the Late Triassic – Jurassic. Whereas in the Cretaceous, the tectonic movement was intensive in the west but steady in the east, and climate was dry in the south but wet in the north of NTP. The formation of the tectonic and climatic patterns in NTP were the consequence of either global climate change or regional tectonics, including the Paleo-Asian Ocean closure and the Qiangtang block, Lhasa block and India plate collision subsequently to Asia. Furthermore, the regional tectonic events occurred before any global climate change and drove the climatic change in the NTP.
DAI ShuangZHANG MingzhenPENG DongxiangWANG HuaweiWU MaoxianCHEN RuilingZHANG Xiang
