Formation and Evolution of the Travertine Landscape at Huanglong, Sichuan, One of the World Natural Heritages
世界自然遗产-四川黄龙钙华景观的形成与演化

To make people know more about the Huanglong Ravine of Sichuan (one of the world natural heritage sites) and provide scientific basis for protecting it, this paper summarized the authors' research achievements on the travertine deposits reached during the past decades along with the latest monitoring findings in the Huanglong Ravine. The major results and conclusions are: (l) The formation of travertine was because firstly dissolution of carbonate rock in the recharge area produced groundwater rich in calcium and bicarbonate ions under higher par-tial pressure of deep-seated CO_2, and then calcite deposited on the ground surface due to CO_2 degassing from the groundwater-fed spring with much higher P_(CO2) than that in the atmosphere, which made water to be supersaturated with calcium carbonate; (2) The dominant color of Huanglong travertine was yellow, which was mainly related to the interfusion of soil impurities in the rainy season due to soil erosion after rainfall. However, travertine was formed mainly in the clean and clear spring water in the dry season, so, the color of travertine was white, i.e., the native color of pure calcium carbonate. This was also the reason why the travertine section in the Huanglong Cave shows the lamination structure of yellow alternating with white; (3) High resolution uranium-thorium dating indi-cated that the main body of Huanglong travertine has formed since Holocene; (4) the main reason for the decrease in surface flow rate was leakage to the underground river, which results in the dryness and propagation of aerial algae communities on the travertine surface, the latter was the reason for the black color of travertine. Therefore, it is necessary to take measures to prevent leakage and replenish surface water as early as possible; (5) The tourism activity has shown its influences on the Huanglong travertine landscape. These include the filling up of some tra-vertine rimstone pools downstream due to human trampling on the travertine landscapes upstream, and the propa-gation of diatom and possible decrease in travertine deposition rate due to the pollution of the phosphate in the tourism midseason. Therefore, relevant preventing and controlling measures must be taken as soon as possible.