GROWTH AND DECAY OF PALSAS AND PEAT PLATEAUS IN THE MACMILLAN PASS TSICHU RIVER AREA, NORTHWEST-TERRITORIES, CANADA

Macmillan Pass, at 1350m asl, is located in the Selwyn Mountains at the Yukon - Northwest Territories border (63o15'N, 130o02'W). This area lies within the discontinuous but widespread permafrost zone. Palsa-peat plateau complexes cover 0.7% of the 235km2 study area and are found in bog and fen depressions at elevations from 1285-1690m. Palsa heights range from 0.15-9.75m and diameters from 3.25-75.0m; peat plateaus have maximum heights of 2.5m and maximum diameters 225m. These permafrost features have formed since the White River volcanic ash fall of 1220 BP. On palsas and peat plateaus this ash occurs at an average depth of 21cm and has an average thickness of 11.6cm. Shrinkage and (or) total decay of palsas and peat plateaus has occurred during the past 34 years. -from Authors