Process Of Deposition And Climate Environment Information Of Tufa At Binglingshan, Qinghai

This thesis reviewed the achievement of global change research and paleoenvironment reconstructed by tufa, simultaneously pointed out the vital significance of tufa in restoring or reconstructing the palaeoclimate and palaeoenvironment research in northwest region and Qinghai-Tibet Plateau, but such research still was a blank. Tufa is a good carrier which records the information of palaeoclimate-environment, and has the unique superiority: (1)The resolution is high, may achieve the resolution of season or month. (2) The geology age could be measuresed accurately and sensitively . (3) The thickness is big, and time spans greately (about equal to loess). (4)In northwest region, when tufa deposits, the land source detritus (for example loess) mixes in along with the climatic change periodically. It has enriched the substitution of climate-index.This thesis is based on the theory of relation between karst and environment. The goal and significance lies in finding out the deposition process and the change rule of the tufa in Binglingshan, and clarifying the applicability and the concrete significance of the climate-indexes which are often used in karst in the tufa. Morever, some new substitution of climate-index were strength to explore. In premise of full understanding geologic background, the analysis of hydrochemistry, carbon-oxygen isotope and rare earth element(REE) were made , then the results yielded as follow :1.The re.ason for Binglingshan tufa forming is that massive CO₂ releasing from water causes CaCO₃ oversaturate and deposit, which can be described by the chemical formulation:Ca²⁺+2HC0₃^- (?) CaCO₃ ↓ +CO₂↑ +H₂O.For this reason, Ca²⁺ reduces rapidly along the brook , but other ions keep stable.2. According the principle of geothermy increasing, the Binglingshan spring-water cycle depth is 640m. The lithological character of the water-bearing stratum which Binglingshan spring-water comes from is consistent with that exposited by the ZK10 well .mainly conglomerate, gravel clamping siltstone, siltstone and so on .3. There is massive CO₂ in spring-water, which reaches as high as 59238.60 Pa. By the influence of CO₂, the water δ¹⁸O value loses remarkablily, average -11.81‰ .4. The massive CO₂ is from depth, therefore it is geothermal tufa. The δ¹³C value averagely is 11.04 ‰ and obviously higher because the...