Uplift and denudation of Mt Sanqingshan Geopark, Jiangxi Province, China

摘要

Mt Sanqingshan, a global Geopark and world natural heritage site located in Jiangxi Province, China, is famous for its eroded granite peaks. The uplift and denudation history of the area has been reconstructed using fission track methods for the first time. Apatite fission track ages (AFTAs) cluster into three groups at ca. 25Ma, 45-55Ma, and 70Ma. These ages can be related to ancient multilevel denudation planes at about 900, 1200, and 1500m above sea level, respectively. The apatite data also reveal four cooling stages for the Mt Sanqingshan region, from ca. 90 to 65-60Ma, 65-60 to 45Ma, 45 to 20-15Ma, and 20-15Ma to the present, with cooling rates of 1.96 degrees C, 1.18 degrees C, 0.37 degrees C, and 3.78 degrees C per million years, respectively, and an average cooling rate of 1.80 degrees C per million years. Calculated uplift rates are 0.055, 0.034, 0.011, and 0.11mm year(-1) in the four stages, yielding uplifts of 4140, 570, 290, and 1940m, respectively. The uplift rate of the last stage was significantly faster than that of the other three preceding stages, reflecting rejuvenation of Mt Sanqingshan, as a result of new tectonism. The average uplift rate at Mt Sanqingshan is 0.053mm year(-1), and the average denudation rate is 0.048mm year(-1), resulting in 3550m of uplift and 2540m of denudation relative to eustatic sea level. The 1010m difference is very close to the average elevation of about 1000m at present. A comparison of uplift-denudation histories for Mt Sanqingshan and Mt Huangshan shows that fission track results can be useful for defining geomorphological development stages.