Study On The Tufa And The Environment Information Significance From Annual Laminations In Huangguoshu, Guizhou

Large scale of surficial tufa developed in Huangguoshu area of Guizhou province. Studying the contributing mechanism, we can understood tufa's conformation and evolvement discipline, which provided scientific foundation for tufa landscape in maintenance and management. Furthermore, tufa annual laminations had the character of high resolution in recording climate information, taking advantage of this, we can reconstructed the palaeoenvironment in Huangguoshu area, and also help us for forecasting the trend of climate change.Based on the hydrogeology conditions, hydrochemical methods, rare earth element and trace element geochemical methods were used to analyze the hydrochemical characteristics, the rule of REE in tufa laminations and Mg/Ca ratio, then the results yield as flow:1. The tufa deposit in was affected by tiny physiognomy, water trait, biological action and hydrodynamic conditions. The quantity of living creature in water was rich, and chemical compositions of the surface water were controlled of fusible lithostrome in Triassic period, so the hydrochemical facion in Huangguoshu area was HCO3.SO4-Ca type. In nine sampling points, only the tufa where developed in Maoshuitang was dissolving, because of physiognomy affect. Totally, the environment in Huangguoshu area was still helpful in precipitation and formation for the tufa at present.2. The LREE was positively correlated with HREE(R2=0.988).It showed the chemical separate between LREE and HREE was restrained, and week redoxomorphism. The sedimentary condition may be a little dry at that time in all.3. There is low fractionation between LREE and HREE, and it can be denoted with the ratio of LREE/HREE. It was helpful with HREE migrate in wet climate environment, then resulted in lower LREE/HREE ratio. On the contrary, in dry environment the LREE/HREE ratio will get higher.4. In tufa annual laminations, Mg/Ca ratio was good at correlating with LREE/HREE ratio (R2 = 0.60)in positively. According to LREE/HREE ratio change, we can know about the rule of rainfall variety that reflect in every annual lamination. The result was that Mg/Ca ratio can served as indicator for reconstructing the palaeoenvironment in Huangguoshu area Guizhou province.5.With the LREE/HREE ratio and Mg/Ca ratio change implied the feature of rainfall variety, beside with the REE variety characteristic, the research generalized the feature of palaeoenvironment in Huangguoshu area, that was hot and drought, warm and drought, cold and moist, hot and drought, warm and moist, warm and drought.