Ecological Land Classification of Mount Revelstoke and Glacie r ...

Glaciation was a major factor shaping the landscapes of MRNP and GNP . Moraine (M) is extensiveand frequently dominates cirque and pass floors, valley wall shoulders, and broad mountain tops .Moraine also occurs on moderately sloping valley walls and with ice contact stratified drift on bench -lands of some broader valley floors .Moraine usually occurs as blankets and veneers . On valley walls, surface form reflects inclined bed -rock . Slopes are most often 45 to 65% and uncommonly up to 70% . Such long straight slopes frequentlyhave gullies oriented perpendicular to the contour . Less often slopes of 30 to 45% occur ,usually on upper and lower slopes transitional to more irregular terrain . These slopes are more characteristicof pass, cirque, and valley floors, valley shoulders, and broad mountain tops . This complextopography may be ridged and, less often, hummocky or a combination of inclined and ridged, all reflectingbedrock control . Deep, ridged and occasionally hummocky till, reflecting deposition ratherthan bedrock control, is virtually restricted to Neoglacial lateral and terminal moraines. Some irregularlandscapes have been produced or accentuated by slope failure (modifier F) of overburden or bed -rock. However, not all failed slopes have complex topography . Complex slopes are commonly 30 to45% although tracts with 0 to 30% or 30 to 70% also occur .Snow avalanching and solifluction also modify morainal landforms . Modification is primarily to vegetationor soils and is not sufficient to produce colluvial landforms .Colluvial, residual, eolian, and fluvial materials occur locally or as a thin mantle in some morainallandscapes . Colluvium occurs on local, steep slopes, particularly on terrain affected by slope failure .Residual veneer underlies till at some sites and was produced by bedrock weathering . It most oftenoccurs on gently sloping, high elevation areas with recessive, highly jointed bedrock . Discontinuou sfluvial or eolian veneers often thinly mantle gently to moderately sloping, high elevation moraines .The former are associated with morainal wetlands affected by seepage, the latter occur on drier ter -rain. Both are important to soil formation .The last major deglaciation in south central British Columbia was probably complete before 10,000years ago (Fulton and Smith 1978, Ryder 1978) . However, source bedrock lithology is more importantto textural and chemical properites of morainal material than is glacial chronology (Wittneben1980, Walker et al. 1982a) . These properties were imparted by the strata and remain distinct eventhough the products were mixed by glaciation . The deposits are divided into three morainal geneticmaterial units, Tills A, B, and C, on chemical and textural characteristics (Table 8) .Till ATill A is noncalcareous, coarse textured, and derived from noncalcareous, medium to coarse grained ,metasedimentary (mainly quartzitic) and granitic strata of the Hamill Group, granitic intrusive andShuswap Metamorphic Complex bedrock areas (Fig . 2) . Soils developed in Till A are normall ystrongly to extremely acid (pH