Estimates of the Age of the Existing Relief within the Southern Rocky Mountains of Canada

Abstract

U-series ages and palaeomagnetic data for calcite speleothems collected from seven relict phreatic caves preserved in valley walls in the Crowsnest Pass and Columbia Icefield areas of the Canadian Rocky Mountains are used to derive local mean maximum, or mean maximum and minimum, rates of valley deepening for the timespan 180 to >350 Ka BP. Maximum rates range 0.13 to 2.07 m 1000 yr^-1. Minima are >0.04 to 0.07 m 1000 yr^-1. These results are extended to estimate ages for the mean relief of 1340 m that exists between valley floors and adjacent crestlines in these mountains. The age estimates range 0.65 to 33.5 Ma; it is argued that the true age is most likely to fall between 1.2 and 12 Ma, and 6 to 12 Ma is the preferred time range suggested by the results.