14C dating of loess

Abstract

Only indirect age determinations up to 50 ka BP can be carried out on loess using the 14C dating method. Organic materials such as charcoal, wood, and bones embedded in loess are suitable for dating. Soil horizons are less suitable due to the mobility of humic acids, which are used for dating. Snail shells constitute the best kind of organic carbonates for age determination. Loess concretions (loess kindl, calcrete) are frequently unsuitable as they may have been formed and/or diagenetically altered long after the loess was deposited. Two dating techniques are available: radiometric detection (by liquid scintillation, proportional, and miniature counters) and accelerator mass spectrometry, which vary as to the amount of sample required (5–5000 mg carbon equivalent) and the dating costs ($100–$1000 per sample). There are various problems inherent in the interpretation of 14C dates of Pleistocene loess samples. For comparison with absolute dates it must be kept in mind that 14C ages may be smaller by several thousands of years than the true ages: this is due to dendrochronological calibration problems which have not yet been satisfactorily solved for samples exceeding 10 000 years in age. Besides this, age deviations of several tens of thousand years may occur due to contamination with allochthonous carbon compounds. In spite of these mentioned problems, 14C dating of samples found embedded in loess will continue, as material suitable for other dating techniques is often not available.