GEOLOGY OF THE FLUVIAL TRAVERTINE FROM THE JIUZHAIGOU NATIONAL NATURE RESERVE, SICHUAN PROVINCE, SOUTHWESTERN CHINA

The Jiuzhaigou National Nature Reserve is located on the Tibetan Plateau (Sichuan, southwestern China) and is considered to be one of the most spectacular natural travertine deposits in the world. The deposition of fluvial travertine occurs in a spectacular array of shoals, waterfalls, pool-dam systems and multicolored lakes. The evolution of this high altitude (2100 to 2900 m) carbonate system is of particular interest in the understanding of the Tibetan region paleoclimate and the modification that tourism impact may induce. Touristic impact on the area is progressively increasing with over 3.5 million visitors in 2012 and concerns on the preservation of the travertine features are rising. Significant changes in the depositional system, such as reduced carbonate precipitation and spreading of algae colonization have been recently noted (Gu et al., 2013).

The development of the travertine system is driven by two seasonal, but different climate patterns with a wet spring-summer and then a dry fall-winter. The fluvial shoals show two main superimposed facies of alternating low and high turbulence water flow. The low turbulence facies consists of clotted micrite encrustation of mosses and cyanobacteria filaments, and platy calcite crystals covering algal filaments. The high water turbulence facies show seasonal alternation of diatom-rich bundles of Phormidium sp. (late spring) with algal Oocardium stratum levels (summer-fall). The precipitation of carbonate results in the formation of prograding waterfalls and dam-pool systems that encrust logs, branches, tree roots and mosses with microspar and clotted micrite.

Diagenesis of the travertine include “speleomorphization” by the ensuing percolation of carbonate-rich water and also the slow dissolution of diatom frustules that takes place over the span of several years.

Clastic travertine is produced by the partial collapse of the rapidly growing hanging walls of waterfalls and during floods after the dry season exposure of long sections of the valley.

Gu, Y., Du, J., Tang, Y., Qiao, X., Bossard, C., Deng, G., 2013, “Challenges for sustainable tourism at the Jiuzhaigou World Natural Heritage site in western China”, Natural Resources Forum 37, 103-112.