Aspartic Acid Racemization in Late Wisconsin Lake Ontario Sediments

Abstract

We have determined aspartic acid racemization and [14C] ages in sediment from a 17-m piston core recovered from Lake Ontario. This core represents a depositional record extending back into the Late Wisconsin. Total organic radiocarbon ages of the glaciolacustrine lower section of the core are older than the true depositional age. Hence we suggest that these ages do not represent time elapsed since deposition but rather may be up to several thousand years too old due to mixing with 14C-depleted organic matter and possibly also D-amino acids contained by the glacier and deposited as the glacier receded. Further studies are suggested that might test this hypothesis as well as establish the general applicability of racemization dating to clay sediments.