安第斯山脉中段的地质过程和冷生作用(英文)

Geological Processes and Geocryogenic Effects in the Central Andes

本文描述了安第斯山脉中段南纬35°,西经70°附近面积为370km^2的一个地区的地质情况和冻土情况。附有地质图、冻土图及露头-碎屑分布图。文中探讨了不同地质条件下的冻融作用及多年冻结效应。岛状多年冻土分布下界处在海拔3000m,这与安第斯山脉纬度较低地区的纬度-高度梯度相符。在5个地点发现了大型的古山坡堆积物,这些堆积物可能是由融冻泥流作用、碎石流和滑坡所形成的。在实验室内将不同种类的岩块在饱水条件下进行了250次冻融循环试验。根据以下4个方面来考虑这些岩类的野外地质冻融敏感性指标(FGFSC):1)露头指数(％);2)地貌情况;3)冻融过程的次数以及4)实验室冷生破碎情况。用这一指标解释各类岩石山地的高度规律。

The geology and geocryology of a 370 km2 area in the Central Andes at 35° S, 70° W is depicted. Maps of geology, geocryology, and outcrop-debris are shown. Frost action and permafrost effects under different geological conditions are considered. The lowest sporadic permafrost boundary in the area is at about 3 000 m a.s.l., in agreement with its lati-altitudinal slope indicated for the lower latitudes of the Andes. Large fossil mass wasting deposits, probably produced by gelifluction, debris flows and slides are present in five places.Different rock types were subjected to 250 cycles of freeze and thaw under saturation laboratory conditions. Field geological frost-susceptibility criterion for different rock types is considered based on 1) Outcrop index, 2) Geomorphology, 3) Number of geocryogenic processes and 4) Laboratory cryofraction. Such criterion is used to explain the elevation of mountains made from different rock types.