CGRG Bibliography of Canadian Geomorphology
Search Results
Author : Gosse, J.; Dyke, A.; and Klein, J.
Date : 2001.
Title : Recent and potential applications of in situ terrestrial cosmogenic nuclides in Canada.
Publication : St. John's 2001. Geological Association of Canada - Mineralogical Association of Canada 2001 Joint Annual Meeting / l'Association géologique du Canada - l'Association minéralogique du Canada réunion annuelle conjointe. Memorial University, St. John's, Newfoundland, May 27-30 2001.
Issue :
Page(s) :
Abstract
The TCN exposure age method has developed beyond its trial phase in both analytical and application respects. Measurement precisions for most of the isotopes are routinely 4% or better and total random errors are as low as 10%. Accuracy has also improved in the past 3 years with growing understanding of the cosmic ray interactions involved in the production of the isotopes and with more empirical calibrations of production rates at different latitudes and altitudes. Uncertainty in half lives, the production rates and their spatial scaling calculations, and other parameters now yield an average total systemic error that is approaching 10%. Ages as young as late Holocene have been determined although it may be necessary to compensate for minor production rate effects of secular variation in dipole axis position. The method has already contributed to addressing long-standing questions of Quaternary history in Canada. Exposure ages on boulders on raised beaches on Prince of Wales Island are concordant with radiocarbon driftwood ages and closely replicate the emergence history. Ages on boulders on moraines and other drift have shown the method to be useful in tracking a retreating ice margin, defining limits of glaciation, and helping establish paleo-ice volume. The method has been used to study cold-region landscape evolution, in particular glacial plucking rates, tor development, and non-glacial bedrock erosion. Insights into the controversy over biological refugia on nunataks have also been provided, and cold-based ice cover postulated by detecting evidence of shielding of bedrock surfaces from cosmic radiation. Future applications will be similarly diverse. In glaciated areas lacking fluvial strath terraces it is possible to date deformed or tilted alluvial fill terraces in order to evaluate the late Cenozoic tectonic history of a region. Studies to date mass wasting events that may provide paleoseimic or paleoclimate information have also been successful. Ages on late Pleistocene raised deltas in Tierra del Fuego indicate that the method can be useful for tracking sea level history from topset-foreset contacts along tectonically or isostatically emerging coastlines. Under the right conditions, the technique can also provide useful information for archeological and geoarcheology investigations.
Bibliography of Canadian Geomorphology