古气候变化的石笋同位素记录研究——以桂林盘龙洞为例

Isotope Geochronology Study for “POG Type” Granite in Bayan Har Terrain

本文以桂林盘龙洞的研究工作为例，选择大型石笋剖面，在沉积学分析学研究的基础上，采用目前最先进的测年技术———ＡＭＳ１４Ｃ法，配合Ｕ系及稳定同位素地球化学综合手段，系统提取气候信息，建立了桂林地区３．６万ａ来气候变化的基本模式。该区末次冰期３．２～３．６万ａ时，年平均气温最低８～９℃。全新世在总的暖和、潮湿气候背景下，可划分出由暖到冷的３个气候旋回，每个旋回持续约３０００ａ左右，暖期年平均气温高于现今３～４℃，冷期低于现今３℃左右，可鉴别的次一级冷期可与我国５０００ａ物候记录资料进行对比。

Bayan Har terrain lies in the northern part of the Tibet plateau, and between the Kunlun terrain and Qiantang terrain. there are many granite outcrops in the eastern part of Bayanhar terrain. The 39 Ar- 40 Ar age of biotite and the 207 Pb/ 206 Pb age of zircon indicate the granite body formed at 220～212 Ma. After that, the granite had undergone two times metamorphism and deformation at 148 Ma and 110Ma。