Pitfalls in the AMS radiocarbon-dating of terrestrial macrofossils

✍ Scribed by B. Wohlfarth; G. Skog; G. Possnert; B. Holmquist

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 157 KB
• Volume: 13
• Category: Article
• ISSN: 0267-8179
• DOI: 10.1002/(sici)1099-1417(199803/04)13:2<137::aid-jqs352>3.0.co;2-6

✦ Synopsis

The AMS 14 C technique has the advantage that small samples of Late Quaternary age can be dated with high accuracy, and that errors due to reservoir effects can be avoided if specifically determined terrestrial micro-and macrofossils are measured. However, to obtain such high-accuracy measurements, it is important how small samples are handled prior to treatment in the radiocarbon laboratories. Here we present a set of 51 AMS 14 C measurements, of which 31 dates gave expected ages and 20 dates resulted in anomalously young ages, despite the fact that all samples consisted of clearly identified Late Weichselian terrestrial plant macrofossils. To evaluate possible sources of error, we compared these samples in respect to preparation methods, sample storage and sample weight. Our results show that the long-term storage of wet macrofossil samples appears to have a significant effect on the radiocarbon age obtained, even when the samples are kept cool. Fungi or micro-organisms may easily be incorporated into a sample during preparation and identification, and can easily contribute to the contamination of a sample, if stored cool and wet for several months.