A Study Of The Highly Unstable Climate In Last Glacial Cycle

Climatic change is a hotspot of recent research in geoscience. Since there are abundant records with high resolution and comparability in the last interglacial, which is close to present Holocene interglacial, the last interglacial become the best period to study climate change in current Holocene interglacial. Though the last glacial, following the last interglacial, has quiet different climate environment with the last interglacial and recently greenhouse effect brought high temperature for the world, it is also important for modern human to study the climate environment during the last glacial in detail. So, the study of the period after the last glacial/interglacial cycle became a key in those important studies of climate change.As Chinese loess records were terrestrial sediment that could be compared to those records in ice core and deep-sea in 1990's, scientists did lots of studies about loess records and made great success. However, limited by low resolution and sedimentary rate in most loess profiles, it is difficult to take further study. Regarding last glacial/interglacial cycle, there are great differences in loess records, especially in the last interglacial. Did those differences represent different climate information recorded in loess stratigraphies? Or were caused by subsequent changes in loess? To answer those questions, we need some new profiles that are more responsible. But, low sedimentary rate in many profiles, especially in S1, and following strong pedogenesis and eluviation would have effect on those climate records. So, the inherent problem limits advanced study of loess profiles. Fortunately, in some special areas of China, there are some thick loess profiles with higher resolution and sedimentary rate, which were formed in the last interglacial. And in this thesis, we discussed two profiles, Wangguan profile in Sanmenxia, Henan Province and Shagou profile in Wuwei, Gansu Province, which are located in east and west side of Liupan Mountains, respectively. With respect to S1, the thickness of S1 in the two profiles is 12.5 m and 11.6 m and the sedimentary rate in the last interglacial period is 23 cm/ka and 21 cm/ka, respectively. To explore and study those loess profiles with high resolution and sedimentary rate would be helpful to investigate some problems about mechanism of climate change in East Asia monsoon region.Comparing Wangguan profile with Shagou profile, we found that both of the two profiles have 5 palaeosol and 4 loess layers in S1 and the time of formation correspond to each other. It represented that strong summer monsoon occurred 5 times and dust deposited 4 times in the last interglacial. It demonstrated that not only East Asia winter monsoon but also East Asia summer monsoon fluctuated many times in both areas. At the same time, it also suggested that East Asia monsoon was probably unstable in the last interglacial and was far from the former mode. According to the extent of proxies' change, East Asia winter monsoon fluctuated less than East Asia summer monsoon and the former more influenced the west areas of East Asia monsoon region while the latter...