Aranuian radiocarbon dates from moraines in the Mount Cook region, New Zealand

Abstract

18 new radiocarbon dates were obtained for organic materials, associated mainly with soils buried by till, from sites in the lateral moraines of Mount Cook glaciers, particularly the Tasman. The 23 New Zealand (i.e., Institute of Nuclear Sciences, DSIR, Lower Hutt) dates now available from the Tasman Glacier, taken at face value, indicate that there were glacier expansion periods there about 3450-3000, 2280, 1800-1620, 1200-900, 860, 680, 340, and < 250 radiocarbon years ago. Taking into account the statistical counting error, the ages of some of the date sets overlap. Excluding a few problematical age determinations, and those on whole soil samples, the full range of dates now available from moraines of Mount Cook glaciers (including those from the New Zealand laboratory and a laboratory in Hannover, West Germany), taken at face value, shows that glacier expansion episodes have occurred: c. 8000 years ago, probably in the 6th millennium B.P., c. 3690-3000, c. 2550-2280, c. 2110-1620, c. 1255-900, c. 860, c. 680, c. 550, c. 340, and < 250 radiocarbon years ago. The dates and the associated geomorphic evidence indicate that the glacier shrinkage which ensued from about A.D. 1900 to at least A.D. 1984 has been the most profound for at least the last 3500 years.