放射性核素^(210)Pb_(uns)、^(137)Cs测定巴丹吉林沙漠湖泊岩心的年代及沉积速率

Determination of Age and Sedimentation Rates Using Radionuclide(^(210)Pb_(uns) and ^(137)Cs)Dating in Inter-dune Lakes of the Badain Jaran Desert,China

巴丹吉林沙漠发育了世界上独一无二的沙漠丘间湖泊群,100多个永久性的丘间湖泊分布于沙漠的东南部。沙漠湖泊岩心是干旱地区重要的气候、环境档案,然而受沙漠湖泊发育极端环境的影响,岩心测年面临很大挑战。本文选择巴丹吉林的沙漠南缘的阿尔吉林和敦德吉林丘间湖泊进行钻探,获取无扰动岩心,利用核素(^(210)Pb_(uns)、^(137)Cs)进行测年,并计算其沉积速率。结果表明:1核素(^(210)Pb_(uns)和^(137)Cs)测年能够获取巴丹吉林沙漠现代丘间湖泊岩心的可靠年代。2巴丹吉林沙漠丘间湖泊岩心Ar-1的CRS模式测年结果为102±8a,沉积速率分布范围为0.13~0.33cm/a,岩心Dd-1的CRS模式测年结果为123±2a,沉积速率分布范围为0.18~0.70cm/a。3沙漠岩心沉积速率的空间分布具有自沙漠腹地向边缘递增的趋势,^(210)Pb_(uns)-CRS平均沉积速率分布范围为0.16~0.57cm/a,^(137)Cs沉积速率分布范围为0.05~0.6cm/a。未来,对于沉积速率空间变化的可能影响因素,如高大沙山的围限、阻挡效应、^(137)Cs的分子扩散效应以及古地震影响等应予以关注。

A unique inter-dune lake group containing over 100 permanent lakes developed in the southeast of the Badain Jaran Desert. Inter-dune lake sediments are important climatic and environmental archives in the dryland, but dating these sediments using radionuclides （^210 pb,^137 Cs）is impeded by the extreme environment in the desert, such as low flux of radionuclides caused by rare precipitation. Two lakes in the southeast of the Badain J aran Desert, Arerjilin and Dundejilin, were drilled and undisturbed core sediments were obtained for dating with ^210Pbuns and ^137Cs. Results show that. ① reliable ages of inter-dune lake sediments can be obtained by radionuclides （^210Pb,^137Cs） dating; ② dating results of Core Ar-1 and Dd-1 are 102±8a and 123±2a respectively based on CRS model, and sedimentation rates of these two cores ranged from 0.13 to 0.33 cm/a, and from 0.18 to 0.70cm/a respectively. ③ Sedimentation rates of interdune lake sediments increased from the center to the margin of the desert spatially, and average sedimentation rates ranged from 0. 16 to 0. 57cm/a if estimated from 7 CRS ages of inter dune lake sediments, and from 0. 16 to 0. 57cm/a if estimated from 11 ^137Cs ages of inter-dune lake sediments. In the future, much atlention should be paid on the possible inpacting factors on sedimentation rates of inte-dune lake sediments, such as barrier effect of mega-dunes, ^137Cs molecular diffusion and even paleo-earthquakes.