西藏台错古湖晚第四纪轮藻类及其生态环境、气候变化探讨

西藏台错TT-1剖面厚369 cm,为一套碳酸盐粘土和粘土碳酸盐沉积,地层测年为41.4-4.5 ka,含丰富的轮藻化石,分属于11个轮藻植物群,群落所在地层的碳酸盐和钙质含量分别为80％和33％.从老到新(剖面自下而上):①41.4-26.64 ka(369-319 cm),处于末次冰期间冰阶MIS3a暖期,湖区气候...

STUDY ON THE LATE QUATERNARY CHAROPHYTES,ECOLOGICAL ENVIRONMENT AND CLIMATE AT PALEOLAKE TAICUO,TIBET

The section TT-1 at Taicuo,Tibet is 369 cm of carbonate-bearing clay and clay-bearing carbonate sequence,aged 41.4—4.5 ka,rich in fossil charophyte which can be subdivided into 11 floras.Five palaeoenvironmental development stages of the palaeolake Taicuo can be recognized.(1) 41.4—26.64 ka(369—319 cm),a warm period in MIS 3a,when the climate was warm and wet,the water was deep and unrest,with lower contents of carbonate and calcium(13%—21% and 4.4%—6.6%),and no charophytes existed.(2) 26.64—20.48 ka(319—284 cm),a flourishing period of the floras,when water plants were lush,and the water had a higher content of calcium and organic carbon,especially during 25.20—22.45 ka(319—301 cm).The climate was still warm and wet,after about 22 ka.However,the climate tended to be cold and dry,and the water temperarure was going down.(3)20.48—14.60 ka(284—217 cm),the charophytes were less flourishing as the climate became colder and drier,which caused by the decline of water temperature and nutrients.All this was a reflection of the global LMG climate in the lake.(4) 14.60—10.40 ka(217—125 cm),the charophytes got flourishing again,but the climate was variable in the lake resulted in the frequent water temperature fluctuation.As a result,there was also an inconstant amount of gyrogonites produced.In the period of 13.62—12.35 ka,as it turned comparatively warm and wet and the water temperature went up,the charophytes got quite lush with adequate nutrients and oxygen.But the reproduction of the floras declined later during the Younger Dryas period.(5) 10.43—4.5 ka(125—0 cm),the climate in the lake tended to be warm and wet,and the charophytes were in a well-growing state.The charophytes became more thriving during 6.20—4.5 ka as the environmental humidity got higher and the water temperature increased,and the floras reproduction ranks the second in the section.