Lake Sediment Records Of Evironment Changes In The Chaohu Lake Basin Since 9870cal.aB.P.

The Chaohu Lake basin was humanity's important active area in the ancient times. It also was the place that cultural prosperity and decline frequently. People of Chaohu Lake basin have manifested the very high wisdom to the use of natural environment since the New Stone Age. They have created the advanced civilization. Discussing natural environment evolution in this region at early and middle stage of Holocene is very useful to the Peleoenvironment, the human activities, the region culture change and so on all has the certain model significance. Simultaneously, it also can make the foundation for instructing the region environmental archaeology and speeding up the regional sustainable development.Based on the environmental history record which through to gathering lake sediment column type chronology in the west Chaohu Lake and the analysis of spore-pollen, the research of grain-size and the magnetic susceptibility, it has been reconstructed the regional environment evolution sequence since 9870cal.aB.P.. Main conclusion as follows:1 The West Chaohu Lake District 490cm lake sediment column type mainly for turquoise the putty level, partially clamps the thin sand body for green-gray color the putty primarily. 7 AMS14C dating data indicated that lake sediment is the lake sediment since 9870cal.aB.P.2 Multi-proxy index analysis shows the following character of climate and environmental changes since 9870cal.aB.P..1) In about 9870-6040cal.aB.P. period, it is warm and wet, Chaohu Lake is in the high water mark, it is expansion for lake surface; About 8,120-7700cal.aB.P. period,the climate starts to change and possibly corresponds cold-dry period, the temperature and the humidity compares the preceding section of times to have the drop ; About 7,700-6030cal.aB.P. the area climate starts to the warm and wet climatic change. 9600cal.aB.P., around 9240cal.aB.P. and 6160cal.aB.P. possibly were the warm and wet time.2) In about 6040-4860cal.aB.P.period, the region environment was warm and wet. Around 5900cal.aB.P.,it possibly corresponds a time of specially warm and wet time.Around 5650-5500cal.aB.P.,it is corresponding a section of dry periods; 5550-5400cal.aB.P. period,it was warmer and wetter,the rainfall is rich. About 5,400 - 4860cal.aB.P.it starts to the drought, the rainfall to reduce.3) In about 4860-2170cal.aB.P.period,the temperature gradually reduces, and the humidity also drops, it was a cold-dry period in Chaohu Lake basin. Around 3900cal.aB.P., proxy index and so on deposit granularity and magnetic susceptibility appears a time of bigger undulation, reflected possible to correspond a time of dry period. The environment undulation probably continues to around 2980cal.aB.P.. This stage later period 2,980-2170cal.aB.P., in the environment whole continues to the arid transformation, lake surface continue to contract. About 2170cal.aB.P.,it possibly is in the history of Chaohu Lake lake surface a smallest time, Chaohu Lake trough and local area possibly appears above the water surface.4) In about 2170-1040cal.aB.P.period , it is Chaohu Lake basin warm-wet time, the climate is suitable the humanity to live, lake surface starts to expand once more. This issue of Chaohu Lake basin also comes under the intense influence which the human moves. About 2170cal.aB.P. each kind of proxy index rapid change, the synthetic study that is possible the region suddenly to correspond to transfer warm and wet, the lake high water gets up, the area expands, and it possibly creates a time of flood disaster.5) In about 1040-200cal.aB.P.period,multi-proxy indexs reflection overall the climate warmer is wet. In the granularity overall assumes the tendency which reduces, reflected the Lake Chaohu basin warm continues to be wet, lake surface gradually expanded transforms, has established the modern Lake Chaohu lake trough shape. 1,040-750cal.aB.P. is the warm and wet time; 750-620cal.aB.P. environment is warm and wet; 620-200cal.aB.P. environment is arid, lake trough unceasingly reduces, lake surface unceasingly contracts the stage,possibly is Lake Chaohu silts up a more serious time. The humanity produces the activity to strengthen also is causes this time deposit environment proxy index change the important attributes.6) Since recent 200cal.aB.P., the Lake Chaohu basin climate is still the warm and wet stage. The lake organic content increases,the magnetic susceptibility appears the low value. Around 120cal.aB.P., the granularity appears an extremely high value, is possible and humanity's large-scale development operation concerns.3 The article analyzes environment changes recorded by lake sediment from the Chaohu Lake basin since 9870cal.aB.P..On the one hand the regional environment evolution is a part of the global environment changes,it is influenced by the whole world environmental changes.So it is the response to the whole world environment changes. On the other hand, as a result of the Chaohu Lake unique geographical position, with the region physical geography background, the structure mobile belt which locates, locates the basin characteristic and so on, all was changes the regional environmental changes to have more complexity, therefore the environment evolution had the region characteristic. At the same time,since former-middle Holocene Chaohu Lake basin environment evolves,it also has been influenced by the partial humanity moves.