High-Resolution AMS 14 C Dating of Post-Bomb Peat Archives of Atmospheric Pollutants

• Published in: Radiocarbon
• Main Authors: Goodsite, Michael E, Rom, Werner, Heinemeier, Jan, Lange, Todd, Ooi, Suat, Appleby, Peter G, Shotyk, William, van der Knaap, W O, Lohse, Christian, Hansen, Torben S
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2001
• Subjects: General Earth and Planetary Sciences; Archeology; Greenland
• Online Access: http://dx.doi.org/10.1017/s0033822200041163; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033822200041163

Peat deposits in Greenland and Denmark were investigated to show that high-resolution dating of these archives of atmospheric deposition can be provided for the last 50 years by radiocarbon dating using the atmospheric bomb pulse. 14 C was determined in macrofossils from sequential one cm slices using accelerator mass spectrometry (AMS). Values were calibrated with a general-purpose curve derived from annually averaged atmospheric 14 CO 2 values in the northernmost northern hemisphere (NNH, 30°–90°N). We present a thorough review of 14 C bomb-pulse data from the NNH including our own measurements made in tree rings and seeds from Arizona as well as other previously published data. We show that our general-purpose calibration curve is valid for the whole NNH producing accurate dates within 1–2 years. In consequence, 14 C AMS can precisely date individual points in recent peat deposits within the range of the bomb-pulse (from the mid-1950s on). Comparing the 14 C AMS results with the customary dating method for recent peat profiles by 210 Pb, we show that the use of 137 Cs to validate and correct 210 Pb dates proves to be more problematic than previously supposed. As a unique example of our technique, we show how this chronometer can be applied to identify temporal changes in Hg concentrations from Danish and Greenland peat cores.