青藏高原中南部天门洞倒三冰消期石笋沉积及其环境意义  

Stalagmite deposition and its environmental significance during the antepenultimate deglaciation in Tianmen Cave,south-central Qinghai-Xizang Plateau

作　　者：栗若馨 蔡演军[1] 黄守毅 王海波[1] 薛刚 卫莹莹 贺梅 宁有丰[1] 贾雪雪 王婷[1] 程海[1] LI Ruoxin;CAI Yanjun;HUANG Shouyi;WANG Haibo;XUE Gang;WEI Yingying;HE Mei;NING Youfeng;JIA Xuexue;WANG Ting;CHENG Hai(Institute of Global Environmental Change,Xi’an Jiaotong University,Xi’an 710049,China;Xi’an Institute for Innovative Earth Environment Research,Xi’an 710061,China;China West Normal University,Nanchong 637009,China)

机构地区：[1]西安交通大学全球环境变化研究院,西安710049 [2]西安地球环境创新研究院,西安710061 [3]西华师范大学,南充637009

出　　处：《地球环境学报》2025年第1期31-42,共12页Journal of Earth Environment

基　　金：第二次青藏高原综合科学考察研究(2019QZKK010102);中国科学院战略性先导科技专项(B类)(XDB40010200);西安交通大学青年拔尖人才(A类)项目。

摘　　要：通过对青藏高原中南部天门洞石笋TM-18b进行230Th测年和稳定同位素测试,建立了倒三冰消期249.89—240.32 ka BP的石笋碳氧同位素记录。结合已发表的、发育在同一洞穴石笋的年代和同位素数据,对倒三冰消期石笋生长记录和同位素序列进行分析,发现天门洞石笋TM-18b和19TM-3在倒三冰消期弱季风区间分别沉积28.5 mm和13.9 mm,持续时间约6.5 ka和5.2 ka,表明倒三冰消期弱季风区间青藏高原气候较为温暖湿润。南极冰芯记录的大气CO_(2)、CH_(4)浓度及δD的上升和δ^(18)O_(atm)的下降,以及全球海平面的上升支持倒三冰消期弱季风区间青藏高原气候的回暖。弱季风区间石笋δ^(18)O记录显示季风降水贡献减少,说明冰川融水和/或西风水汽可能为区域降水增多、气候变湿提供了大量水汽。Background,aim,and scope Among the seven most recent deglaciations,the Antarctic ice core temperature record shows the least but fastest temperature rise during the antepenultimate deglaciation.Additionally,three North Atlantic Ice Rafted Debris(IRD)peaks occurred at T-Ⅲ,while only one or two IRD peaks were present at Termination Ⅰ,Ⅱ,and Ⅳ.This particularity makes the study of the antepenultimate deglaciation one of the entry points for a deeper understanding of the processes and mechanisms behind rapid climate change.However,there are few studies on paleoclimatic reconstruction that span the antepenultimate deglaciation.In this study,we examine the growth and stable isotope records of stalagmites from Tianmen Cave in the south-central Qinghai-Xizang Plateau during the antepenultimate deglaciation and endeavor to understand the climatic and environmental changes and their implications.Materials and methods Stalagmite TM-18b was collected in a cave chamber approximately 200 m from the entrance of Tianmen Cave,measuring 13 cm in height and 4 cm in diameter.At various depths from the top of the stalagmite,seven powder subsamples(around 80 mg)were taken along the growth layer using a hand drill for U-Th dating.The powdered samples were dated using multi-collector inductively coupled plasma mass spectrometry(MC-ICP-MS).A total of 73 subsamples were extracted with a hand drill at 0.5 mm intervals along the stalagmite growth axis for stable isotope analysis,which was carried out using a Delta Ⅴ stable isotope mass spectrometer,equipped with a Kiel Ⅳ Carbonate Device.All of these experiments were conducted in the Isotope Laboratory at Xi’an Jiaotong University,China.Results TM-18b began to grow at about 493 ka BP,and after growing 8 cm,there was a growth hiatus.Then,a growth of 3.6 cm occurred between 248 ka BP and 243 ka BP,followed by a depositional hiatus.Around 0.91 ka BP,with the change of depocenter,the stalagmite was redeposited by 1-2 mm.In this study,we focus on the antepenultimate deglaciation rec

关 键 词：石笋 δ^(18)O 倒三冰消期 印度夏季风 青藏高原 

分 类 号：P532[天文地球—古生物学与地层学]