STRUCTURAL CONTROL OF THE MORPHOMETRY OF OPEN ROCK BASINS, KANANASKISREGION, CANADIAN ROCKY-MOUNTAINS

The morphometry of chutes (couloirs), rack funnels, and open cirques a re related to the structure of dissected rock masses in the Kananaskis region of the Canadian Rocky Mountains. Data for ten morphometric var iables were derived from digital elevation models of 56 open rock basi ns. The basins were classified structurally according to the relative orientations of bedding planes and the rock slopes. A hypothesis of no differences in morphometry among structural classes is rejected from the results of nonparametric analysis of variance and paired compariso ns of rank scores. Basins on dip and overdip slopes have a distinct si ze, and those on anaclinal slopes have a distinct width and shape. Var iation in morphometry from low compactness and area/relief (chutes) to high compactness and low area/relief (funnels) to high compactness an d area/relief (open cirques) corresponds to a change in dominant struc ture from orthoclinal to dip-overdip to underdip to anaclinal. The dip of bedding planes relative to the slope of rockwalls controls the mod e of initial displacement of joint blocks and, thereby, the spatial di stribution of the retreat of rockwalls. The angle between the rock slo pe and the strike of dipping strata determines whether beds of differi ng stability form chutes and buttresses (orthoclinal slopes), or exten d across rockwalls (cataclinal and anaclinal slopes) and retreat at si milar rates to form funnels and open cirques. The optimal structure fo r large compact rock basins is anaclinal, and the least favourable is cataclinal dip-overdip slopes. Topoclimate and other geologic structur es may account for variance in morphometry not explained by difference s among structural classes. (C) 1998 Elsevier Science B.V.