地下水H、O、C同位素揭示的末次冰盛期以来青海东部岩溶发育响应

Response of Karstification in Eastern Qinghai Since the Last Glacial Maximum Revealed by Groundwater H, O and C Isotopes

青海东部岩溶发育在青藏高原持续隆升的高海拔、高寒的构造和气候背景,具有其独特性。岩溶水作为气候记录档案不仅记录了古气候的变化,也对岩溶发育特征及其变化有所反映。本文通过青海东部岩溶水的H、O、C同位素组成,探讨温度和湿度变化,揭示气候变化下青海东部岩溶发育的响应。结果表明,青海东部地区岩溶水化学类型以HCO_(3)-Ca和HCO_(3)-Ca·Mg型为主,水化学组分来源于碳酸盐岩的溶解,岩溶水末次冰盛期以来以大气降水补给为主。从末次冰盛期到全新世早期,总体温度较低,降雨量较多,并在青藏高原持续抬升的地史阶段的夷平面塑造下,青海东部地区形成了独有的高寒-高山岩溶地貌。其中,青海湖流域降雨量较少,温度偏高,岩溶发育不强烈。湟水河流域气候变化频繁,总体气温较低,降雨量较多,是岩溶主要发育地区,且岩溶发育良好。在末次冰盛期,青海东部气候寒冷,降雨量偏多,岩溶较为发育;进入全新世冰后期,气温开始回升,降雨量减少,限制了青海东部岩溶发育强度和深度。末次冰盛期是青海东部地区地表岩溶发育主要时期,岩溶发育方式主要以冻融、冰劈作用为主。

The karstification in eastern Qinghai is unique in the high-altitude and high-cold tectonic and climatic background of the continuous uplift of the Qinghai-Tibet Plateau. As a climate record file, karst water not only records the changes of paleoclimate, but also reflects the characteristics and changes of karst development. Based on the H, O and C isotope composition of karst water in eastern Qinghai, this paper discusses the changes of temperature and humidity, and reveals the response of karst development in eastern Qinghai under climate change. The results show that the chemical types of karst water in eastern Qinghai are mainly HCO_(3)-Ca and HCO_(3)-Ca·Mg types, and the hydrochemical components are derived from the dissolution of carbonate rocks. Karst water is mainly supplied by atmospheric precipitation since the last glacial maximum. From the last glacial maximum to the early Holocene, the overall temperature was low and the rainfall was high. Under the shaping of the planation surface in the geological history stage of the continuous uplift of the Qinghai-Tibet Plateau, a unique alpine-alpine karst landform was formed in the eastern part of Qinghai. Among them, the Qinghai Lake Basin has less rainfall, high temperature, and weak karst development. The Huangshui River Basin has frequent climate changes, low overall temperature and more rainfall. It is the main karst development area, and the karst development is good. In the last glacial maximum, the climate in eastern Qinghai was cold, but the rainfall was abundant and the karst was more developed. Into the post-glacial Holocene, the temperature began to rise, but the rainfall decreased, which limited the intensity and depth of karst development in eastern Qinghai. The last glacial maximum is the main period of surface karst development in eastern Qinghai, and the karst development mode is mainly freeze-thaw and ice splitting.