Kunming Basin Holocene Environmental Change Research

Environmental Change of Holocene is the key to reconstruct past global change and the way to predict the climate of future. The interglacial unsteady climate of has made big arguments, and the Holocene unsteady climate problem is paid more attention. So, the research of Holocene climate change is urgent and significant.Rebuilding history of regional paleoclimate and environmental change with high resolution and continuous lake sediments is important to predict future changing tendency. Response to climate change in plateau region is more sensitive than in the lower altitude. Accordingly, we use the plateau lake sediments to reconstruct the paleoclimate condition.Kunming basin is the biggest and best developed plateau fault depression basin of late Cenozoic, which is located on the boundary of East Asian monsoon and southwest monsoon and also plateau monsoon. The research on the basin Holocene sediments can demonstrate the Holocene climate change in southwest monsoon and offer evidences and information to the forming and evolution of southwest monsoon.The thesis mainly studied typical core sediments from the northern part of Kunming basin. The relative chronology pattern of sediments was built on the basis of comparison of the lithology and characteristic of peat of the core to others' ¹⁴C dating results in this basin. The environmental changes such as sedimentary environment, paleovegetation, paleoclimate and paleoecology are rebuilded and the regional comparison has also done in detail on basis of sedimentary, environmental magnetic susceptibility, grain size analysis, the employing of spore-pollen and phytolith of core sediments, which might make precise prediction of future.According to synthetical analysis to the multi-environmental proxies, the core sediments represent continuous lake sediments and seven environmental evolvement phases have been recognized.1. (13-10.8m) about 8 600-7 000a B.P.Deep lake with warm and wet climate, at last hardpan appearance which maybe the result of some construct function represents the low lake surface ;2. (10.8-7.8m) about 7 000-5 600 a B.P.Holocene Hypsithemal representing southwest monsoon strong, warmer than now, which is divided two parts, the former period is deep lake with warm and wet climate, during the latter time the lake is becoming lower with warm and dry climate.3. (7.8-7.6m) about 5 600-5 300 a B.P.With the hypsithemal ending, the global middle Holocene low temperature period comes, and the climate characteristic is low temperature and moist.4. (7.6-5.2m) about 5 300-3500 aB.P.The sedimental environments fluctuate strongly between deep and low lake, which caused the unconservation of pollen, the climate is alternative between dry and wet.5. (5.2-3.0m) about 3 500-2 200 aB.P.The rainfall is heavy and climate relatively wet, with a period of deep lake.6. (3.0-0.9m) about 2 200-500 aB.P.The water receding, deep lake period ending, the corresponding climate is warmer than now but not up to Phase 6.7. (0.9-0m) after 500 aB.P.At 0.9m, corresponding climate is cold and with deep lake. After that, the lake is receding gradually with warm and wet climate. The human activity has been found in this phase.According to this research on multi-environmental proxies of the northern Kunming basin core sediments, abundant environment change information has been obtained, the relationship between strong southwest monsoon and the Hypsitermal are also recorded in this study, the time of human activity in this region are ensured primarily.