内蒙古额济纳旗嘎顺淖尔XK_1孔揭示的第四纪晚期沉积特点及古环境

Sedimentary features of XK, core and paleaoenvironment in Gaxun Nur of Inner Mongolia since late Quaternary

通过对嘎顺淖尔XK1孔沉积岩芯的岩性特征及多种环境代用指标的综合分析,初步认为:中更新世早中期,29．6 -42．5m(推测时代为距今218．3 kaBP以前),气候温凉偏干,滨湖与洪积相交替;距今218．3-172．8 kaBP气候温凉偏湿, 湖泊面积扩大,以滨浅湖-浅湖沉积为主,并一度出现半深湖环境;距今172．8-93．4 kaBP,沉积环境为湖滨相与洪积相交替,气候特点是冷凉干旱;距今93．4-67．4 kaBP,沉积环境以淡水浅湖为主,夹湖滨相．气候温偏湿;距今67．4-54．0 kaBP ,湖滨相沉积为主,气候温凉偏干;距今54-48．9 kaBP,气候暖湿的浅湖环境,气温较高;距今48．9-42．6 kaBP,凉而且干旱的气候特点,沉积相为湖滨相;42．6-0 kaBP,气候暖湿、凉干交替,浅湖相为主．

Ejinaqi is far from ocean and located in Asian hinterland where the atmospheric circulation is hindered by high mountains. Ejinaqi is controlled by this geographic setting, especially the rapid uplift of Qinghai-Tibet Platean since the late Quaternary, which undoubtedly influences the climate and environment in Ejinaqi. One of our objectives is to establish the palaeoclimatic evolution sequence and to reveal the character of palaeoclimatic changes since the late Quaternary through comprehensively analyzing physical, chemical and biological proxy of sediment in Juyanhai Lake. The sediment character, pollen and ostracode assemblage, minerals, and geochemical elements of 42.5 m long core in middle-west of Gaxun Niir and of JYH-E section in Quyanhai indicate that there are 8 climate stages and the climate was mainly warmer and cool or wanner with obvious fluctuating from dry to wet since middle-Pleistocene. It was cooler and relative wet before 218.3 kaBP; From172.8 kaBP to 218.3 kaBP, the climate was cooler and relative wetter and the lake expanded to a deeper lake; the climate turned to be colder or cooler an dry from 172, 8 to 93.4 kaBP; from 93.4 kaBP to 67, 4 kaBP, the lake shrank to be a shallow lake, showing the climate probably was mild with little humidity ; from 67, 4 to 5.4 kaBP, the salinity of the lake increased and the climate was cooler and relative dry; from 54 kaBP to 48, 9 kaBP, the climate was warmer and wetter; the climate was cool and dry from 48.9 kaBP to 42.6 kaBP ; after 42.6 kaBP , the climate alternated with warmer-wetter and cooler-dry.