Contemporary Sedimentary Environments on Baffin Island, N. W. T., Canada: Debris Slope Accumulations

Abstract

Observations are reported of the morphology and processes on debris slopes in Home Bay and northern Cumberland Peninsula regions of east Baffin Island. The area is block-faulted, heavily glaciated Precambrian gneiss and migmatite. The climate is marine Arctic.

Accumulations range from debris mantles on bedding plane slopes, through conical and sheet talus, to slopes on which snow avalanche or water flow has modified features. The classification of Rapp is extended to encompass these forms. Other features include protalus debris accumulations, and “talus rock glaciers.” Most slopes are planar-concave, with mean unconstrained angles in the range 30 to 38° (mode at 32 to 33°): few slopes appear to be near failure. Size gradation of material occurs downslope: size distribution of material also changes, with Rosin-type distributions near the top and log-normal distributions farther down. Below the surface is a matrix of fines. Size distributions of rock lichens suggest that activity on these debris slopes has been greater in the recent past than at present.

Observations of material delivery and slope stability at Ekalugad Fiord reveal that rockfall is the primary rock delivery mechanism, though dirty snow avalanches are also significant. Rock release appears to be associated principally with the seasonal “freeze-burst-thaw” cycle in water-filled joints and fractures. Material is transferred and rearranged on the slope by impact scattering, creep and settlement, and minor slumps and slides.

A concluding discussion compares observations from east Baffin Island with the assumptions and results of models for debris slope development.