Radiocarbon Calibration Beyond the Dendrochronology Range

• Published in: Radiocarbon
• Main Authors: Stein, Mordechai, Goldstein, Steven L, Schramm, Alexandra
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2000
• Subjects: North Atlantic
• Online Access: https://doi.org/10.1017/s0033822200030344; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033822200030344

The radiocarbon timescale has been calibrated by dendrochronology back to 11.8 ka cal BP, and extended to 14.8 ka cal BP using laminated marine sediments from the Cariaco Basin. Extension to nearly 23.5 ka cal BP is based on comparison between 14 C and U-Th ages of corals. Recently, attempts to further extend the calibration curve to >40 kyr are based on laminated sediments from Lake Suigetsu, Japan, foraminifera in North Atlantic sediments, South African cave deposits, tufa from Spain, and stalagmites from the Bahamas. Here we compare these records with a new comparison curve obtained by 234 U- 230 Th ages of aragonite deposited at Lake Lisan (the last Glacial Dead Sea). This comparison reveals broad agreement for the time interval of 20–32 ka cal BP, but the data diverge over other intervals. All records agree that Δ 14 C values range between ∼250–450‰ at 20–32 ka cal BP. For ages >32 ka cal BP, the Lake Suigetsu data indicate low Δ 14 C values of less than 200‰ and small shifts. The other records broadly agree that Δ 14 C values range between ∼250 and 600‰ at 32–39 ka cal BP. At ∼42 ka cal BP, the North Atlantic calibration shows low Δ 14 C values, while the corals, Lisan aragonites, and the Spanish tufa indicate a large deviations of 700–900‰. This age is slightly younger than recent estimates of the timing of the Laschamp Geomagnetic Event, and are consistent with increased 14 C production during this event.