MORPHOLOGY AND SURFACE-STRUCTURES OF MAXWELL CREEK ROCK GLACIERS, ST ELIAS MOUNTAINS, YUKON - RHEOLOGICAL IMPLICATIONS

The dominant role of mass movement processes in the formation of south -west Yukon paraglacial landscapes is exemplified by a tributary of Ma xwell Creek. Rock glaciers occur along most of the length of the mid-v alley. Two large rock glaciers flowing from cirques on the east and we st sides of the valley are confluent in the centre of the valley, and have a combined lobe extending 1 km downvalley. Morphological contrast s between the moraines and flow lobes of the east form, and the flow r idges of the west form, indicate different processes of movement at th e surface. Sections in the surface deposits indicate movement of the m ass of material in the lobes but demonstrate a combination of overridi ng and compression flow in the ridges. Near surface composition varies from large boulders with voids, to boulders with gravel and fines mat rix and with the ice content varying from interstitial to massive infi lling of the voids. Palaeosols sampled 1 m underneath overriding ridge s were dated at 1480 and 660 a sp. The rock glaciers produced a combin ed central valley landform at the end of the Wisconsin. Neoglacial act ivity resulted only in confluence of the rock glaciers, without extens ion downvalley. The combination of the compressional and overriding ri dges with the variability of the sediments and ice content is indicati ve of a complex surface theology. Comparison with the ridges and lobes of rock glaciers in other valleys suggests that this surface variabil ity is common on the rock glaciers of the southwest Yukon. (C) 1998 Jo hn Wiley & Sons, Ltd.