Climate and geomorphology in the uppermost geomorphic belts of the Central Mountain Range, Taiwan

摘要

The Central Mountain Range of Taiwan is in its lower parts exposed to strong denudation by mass movements caused by extreme rainfalls and active tectonics. Even though the uppermost regions of the mountains are also influenced by earthquakes and typhoon rains, present geomorphic activity is low. Investigations based on field work and air photo study in Nanhuta Shan (3742 m) and Yushan (3952 m) and the analysis of climate data indicate the presence of a periglacial belt with a lower limit at 3600-3700 m. The upper limit of the periglacial belt in Taiwan is not met. Ground temperature measurements in Nanhuta Shan show that freeze-thaw activity at 3560 m during the winter is restricted to the top few centimetres of the ground and the maximum frost depth is ～25 cm. The only indicator landforms within the periglacial belt are smooth slopes. The high relief energy and a lack of fine material account for the absence of other periglacial landforms. Relict solifluction terraces, debris cones and slope failures found between 3400 and 3600 m in Nanhuta Shan are strong evidence for a period of increased slope activity during the Holocene, which in two cases were dated by OSL to approx. 3 ka. At least one solifluction unit developed during a cooler phase between 3 ka and today.