Nature and Distribution of Glaciers, Neoglacial Moraines, and Rock Glaciers, East-Central Brooks Range, Alaska

Abstract

The east-central Brooks Range was just high enough to support cirque glacierization during the middle to late Holocene; presently glaciers are shrinking. The 133 glaciers in the field area are all above 1500 m altitude, and those fronted by stable moraines occur on a trend surface rising from 1600 m south of the Continental Divide to 2000 m, 25 km farther to the north. Glaciers that extend into unstable ice-cored rock glacier deposits occur on a parallel trend 100 m below. Both trend surfaces reflect depletion of moisture derived predominantly from southerly sources. Ice masses associated with both stable and unstable deposits have similar orientations significantly concentrated (asymmetric) about 012°, strongly minimizing exposure to insolation. This contrasts markedly with the symmetric orientation of Pleistocene glaciers. The transition from existing glaciers through tongue-shaped to lobate rock glaciers is characterized by increasingly symmetric orientations and expanding altitudinal and areal distributions. For example, lobate rock glaciers are weakly asymmetric indicating decreased climatic sensitivity and increased screening by surrounding terrain relative to the other forms.