藏南沉错湖泊沉积多指标揭示的2万年以来环境变化

20,000-year Environmental Change Reflected by Multidisciplinary Lake Sediments in Chen Co, Southern Tibet

通过对藏南沉错湖芯TC1孔的研究,分析了TC1孔的粒度、TOC、TN、C/N、Fe/Mn、Sr/Ba以及环境磁学参数等环境代用指标,基本上获得了这一地区2万年以来的环境变化记录.结果显示约19800～18000 Cal aBP的温度下降在各指标中具有明显的反映;约16000Cal aBP左右,温度在一次跃动上升之后,随即出现急剧下降;约15200～12000 Cal aBP,是降温之后的缓慢回升过程;约12000～9500Cal aBP,各种指标均显示湖区环境处于不适宜阶段,特别是11600～10400 Cal aBP,湖区环境显著恶化.进入全新世后,湖区环境经历了3次明显的暖期(约9 500～7600 Cal aBP、约6800～5800Cal aBP、约4800～3800 Cal aBP)和2次冷期(约7600～6800 Cal aBP、约5 800～4800 Cal aBP),呈现出暖干/冷湿的交替规律,具有南亚季风(西南季风)区气候变化的特征.沉错湖区2万年来的气候环境变化序列中的某些特征时段与格陵兰冰芯记录和青藏高原其他记录相比具有较好的一致性,反映了湖区及藏南地区的气候环境演变特征具有全球性特征.

A 20,000-years environmental record is elucidated by analyzing the environmental proxies such as grain size, TOC, TN, C/N, Fe/Mn, Sr/Ba and environmental magnetism parameters from a lake core (TC1) in Southern Tibet area. Results showed that during the period of ca. 19800-18000 Cal aBP, the decreasing temperature was reflected by all analyzed proxies. Temperature appeared a jump rise around ca. 16000 Cal aBP and then had an abrupt decrease. About 15200-12000 Cal aBP, temperature slowly re-rose. However, almost all the proxies indicated that the environment was unsuitable for lives existing during ca. 12000-9500 Cal aBP. Especially during ca. 11600-10400 Cal aBP, the environment became deteriorated. From the beginning of Holocene, the environment experienced 3 obvious warm stages (ca. 9500-7600 Cal aBP, ca. 6800-5800 Cal aBP, ca. 4800-3800 Cal aBP) and 2 cold stages (ca.7600-6800 Cal aBP, ca. 5800-4800 Cal aBP), representing obvious alternation of warm-dry and cold-wet, having the climatic change characteristics of South Asian monsoon (southwest monsoon) zone. Some characters of the 20,000-year climatic and environmental change sequence in Chen Co area had rather good coherence with Greenland ice core records (GISP2) and other environmental records on the Tibetan Plateau, reflecting that the environmental changes in this area had certain global significance.