Implications of improved radiocarbon dates of Timaru peats on Quaternary loess stratigraphy

Abstract

Peat samples from Timaru Downs, New Zealand, before radiocarbon assay were subjected to seven different chemical treatments which included extractions with alkali-pyrophosphate, a range of organic solvents, acid hydrolyses with 6M Hel, 72% H₂SO₄, 70% HNO₃, and their combined treatments. The results obtained show considerable improvement in the reliability of ¹⁴C dates. The maximum improvement ranges from 490 years in the untreated surficial peat (9610 ± 100 year B.P.) to > 15 300 years in the untreated buried peat (34 400 ± 1200 year B.P.). Major implications of the improved ¹⁴C dates on the loess stratigraphy of South Canterbury are that the maximum age of the surficial peat overlying loess member 1 is confirmed at 10 000 years B.P. and at greater than 49 700 years B. P. for the buried peat overlying loess member 2. This significantly alters the minimum age of this member from the greater than 31000 years B.P. previously suggested.