Volume 6, numéro 2, june 1979

EN :

Landslide modes in the Canadian Cordillera are regionalized into eight zones according to the dominance of specific types of failure and mass transport. The Coast-Insular Zone is dominated by rock falls, rock avalanches, debris and earth flows; the St. Elias Zone by rock slumps and debris flows; the Plateau Zone by earth flows and rock slumps; the Skeena Zone by rock slumps; the Yukon-Selwyn Basin Zone by rock slumps; the Cassiar-Columbia Zone by deep-seated slope-sagging and gravitational spreading; the Eastern Carbonate Zone by rock avalanches and debris flows; the Foothills Zone by soft-rock slumps and earth flows. Landslide abundance in the Canadian Cordillera is related to the complex interaction of local geology on the one hand and regional factors such as relief, intensity of precipitation, and seismicity on the other. The landslide hazard deserves special attention in the recreational hinterland of Vancouver and Calgary.

EN :

Recent developments in mass spectrometry, using some of the apparatus and techniques of nuclear physics, have made possible the detection of the cosmic ray created ''C, U)Be and -«-'C1 nuclei at natural concentrations by atom counting. The small sample size, a few milligrams, promises to revolutionize' aC dating and to introduce new dating methods for the Pleistocene

EN :

Evaporites are precipitated in marginal bays from hypersaline brines generated in an arid climatic regime and replenished by a sustained surface influx of waters. The resulting density stratification leads to an entrapment of solar energy in the brine, a depletion of oxygen and an enrichment in organic matter. A continuous bottom outflow flushes those compounds not found adequately represented in the sedimentary record of the evaporite basin. The vertical sequence of precipitates is reversed either in cooler years or by tectonic causes, and is always a function of inflow velocities dictated by the need to maintain a common sea level with the open ocean.

FR :

Les evaporites sont précipitées en baies marginales par des saumures hypersa-lines, qui sont engendrées par un régime climatique aride et qui sont remplies d'une influxion des eaux soutenues à la surface. La stratification par densité prend au piège d'énergie solaire dans la saumure, épuise l'oxygène et enriche la matière organique. Ces sels sont nettoyés avec une chasse d'un effluve continu au fonde, qui no se trouve pas proportionellemont dans la colonne sédimentairo du bassin évaporitiquo. La séquence verticale dos précipités est intervertée dans les années plus fraîches ou par des causes tectoniques Elle est toujours une fonction des vélocités de l'influxion commandées par >la nécessité de conservir un niveau commun avec l'océan.