U.S. Geological Survey radiocarbon dates, [Part] 6.

Abstract

Dates in this list have been determined at U.S. Geological Survey radiocarbon laboratory, Washington, since the 1960 date list (U.S.G.S. V) [GeoScience Abstracts 2-2007]. Procedures for the preparation of acetylene gas used in the counting, and the method of counting, (2 days in 2 separate counters) remain unchanged. However, the modern standard used is no longer wood grown in the 19th century, but 95% of the activity of NBS oxalic-acid radiocarbon standard, as recommended at the 1959 Groningen Radiocarbon Conference. Measurement of the oxalic-acid standard at U.S. Geologic laboratory indicates 6.2 + or - 1% more C (super 14) activity than our modern wood standard, so use of the new standard should make no appreciable difference when comparing samples computed by the old method. W.F. Libby's half-life average for C (super 14) , 5568 + or - 30 years, was used for the decay equation.