Extremely Large Variations of Atmospheric ¹⁴ C Concentration During the Last Glacial Period

Abstract

A long record of atmospheric 14 C concentration, from 45 to 11 thousand years ago (ka), was obtained from a stalagmite with thermal-ionization mass-spectrometric 230 Th and accelerator mass-spectrometric 14 C measurements. This record reveals highly elevated Δ 14 C between 45 and 33 ka, portions of which may correlate with peaks in cosmogenic 36 Cl and 10 Be isotopes observed in polar ice cores. Superimposed on this broad peak of Δ 14 C are several rapid excursions, the largest of which occurs between 44.3 and 43.3 ka. Between 26 and 11 ka, atmospheric Δ 14 C decreased from ∼700 to ∼100 per mil, modulated by numerous minor excursions. Carbon cycle models suggest that the major features of this record cannot be produced with solar or terrestrial magnetic field modulation alone but also require substantial fluctuations in the carbon cycle.

Hydrological control of the dead carbon fraction in a Holocene tropical speleothem

“…Beck et al, 2001;Hoffmann et al, 2010). However, the observed link between DCF and local hydrology in the Liang Luar soil-karst system stresses the need for more detailed research (including both additional measurements and modelling) on the transport of 14 C, and hence DCF, within soilhost rock-cave systems.…”

“…Beck et al (2001), and more recently Hoffmann et al (2010), attempted to extend the radiocarbon calibration curve using highresolution 14 C measurements from U-Th dated stalagmites from the Bahamas. The authors noted large, short-term variations in DCF that were superimposed on a constant offset to the IntCal04 radiocarbon calibration curve for the period of overlap (w11e15 thousand years before present).…”

Comment on “Radiocarbon calibration curve spanning 0 to 50,000 years BP based on paired 230Th/234U/238U and 14C dates on pristine corals” by R.G. Fairbanks et al. (Quaternary Science Reviews 24 (2005) 1781–1796)☆☆doi of original article: 10.1016/j.quascirev.2005.04.007 and “Extending the radiocarbon calibration beyond 26,000 years before present using fossil corals” by T.-C. Chiu et al. (Quaternary Science Reviews 24 (2005) 1797–1808)☆☆☆☆doi of original article: 10.1016/j.quascirev.2005.04.002

“…It does not, however, resolve any of the issues of conflict between data sets that led the IntCal group to decline to recommend calibration beyond 26,000 cal BP. Use of the term "comparison curve" instead of "calibration curve" has been advocated until these issues are resolved (Beck et al, 2001;van der Plicht, 2000).…”

The archaeology of western Arnhem Land’s rock art

“…It is also possible to date meaningfully calcite layers that may have accumulated below or above art, thereby potentially revealing maximum or minimum ages for the associated art (e.g. Beck et al 2001;Genty et al 1999Genty et al , 2001Genty et al , 2004Plagnes et al 2003; see also Chapter 7). Those same calcite deposits can be dated by U/Th, allowing for the useful cross-examination of results.…”