INFORMATION OF HOLOCENE ENVIRONMENTAL CHANGE FROM LACUSTRIAN DEPOSITS OF THE FOYECHI LAKE SECTION,TAIBAI MOUNTAIN

Foyechi Lake,located at an elevation of 3300 m above sea level,near the summit of Taibai Mountain(3767 m), is an alpine ice-scour lake developed in a bergschrund.A section of 210 cm thick lacustrian deposits in the lake was measured. Analyses of the grain size,sporo-pollen and samples for dating show the climate has undergone marked cold-warm and dry-wel changes since 8200 a BP in the Holocene.The 8200-6800 a BP interval was a warm and humid phase,with temperature increasing significantly at 7200 a BP.The climate fluctuated at 6800-5900 a BP,with a short cooling phase at 6300 a BP,and a significant warming phase at about 6000 a BP.Temperature and precipitation decreased at 5900 a BP,which ended at 5200 a BP with the lowest values.Then the temperatures rose slowly and became warm and humid at 4800-2600 a BP.It is believed that the climate was warmest around 3000 a BP.The climate became cold and wet again at 2600-900 a BP,with the temperatures and precipitation reaching their the lowest values at 1500 a BP.The climate becomes better since 900 a BP.