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

ICE CONTACT STRATIFIED GENETIC MATERIALIce contact stratified drift is deposited by glacial ice with local reworking by flowing and ponded glacialmeltwater . The result is extreme vertical and lateral textural variability over short distances . Inessence, ice contact stratified drift is a mixture of morainal and glaciofluvial sediments individuall yinseparable at a scale of 1 :50,000 . Glaciolacustrine sediment, common in many ice contact stratifie ddrift deposits in the Rocky Mountain national parks (Walker et al. 1982a, 1984a), was not found inMRNP and GNP . Ice contact stratified drift and morainal material are collectively called glacial de -posits .Ice contact stratified drift forms moraine-like landforms on benchlands and lower walls of major valleys. Hummocky and ridged surfaces, primarily depositional, are typical of benchland deposits . Asbenchland grades to valley wall, surface expression becomes more regular and reflects inclined bed -rock . The complex slopes of hummocky and ridged topography commonly are 15 to 45% and th esimple, inclined slopes are 30 to 70% . Occasionally, complex slopes of 5 to 15% occur and some ic econtact stratified drift landscapes include gently sloping glaciofluvial terraces too small to map separatelyat the study scale of 1 :50,000. The most important modifying processes are slope failure, channelling(Eroded modifer, C.S.S.C . 1978a) on benchlands, and gullying on steep slopes . Snow avalanchingalso modifies some tracts . All add to topographic complexity .Thin, discontinuous, eolian veneer occasionally mantles gentle to moderately sloping ice contact stratifieddrift on benchlands, and is most abundant in the Revelstoke townsite area . A limited amount ofhummocky to ridged landscape has poorly drained, seepy depressions in which organic and, occasion -ally, fluvial materials have accumulated . The organic materials are occasionally thick enough (>4 0cm) to be classed as fen landforms .Ice contact stratified drift deposits are generally downvalley from two or more source bedrock area s(Fig. 2) . For example, ice contact stratified drift in the Beaver River valley was derived mainly fro mHorsethief Creek and Hamill Group bedrock . The deposit above Revelstoke townsite was derive dfrom Shuswap Metamorphic Complex strata plus other rock types occurring upstream in the ColumbiaRiver valley . Deposits are lithologically complex but only one genetic material unit, Ice Contac tStratified Drift C, was recognized . Its chemical and textural characteristics (Table 9) span the constituentmorainal (Tills A and B) and glaciofluvial (Glaciofluvial material A) materials. The definitionis consistant with KNP (Walker et al . 1984a) except that weakly calcareous drift is not included .Acidic soils (usually pH