Radiocarbon dating

Photo1. Andra performing the osteometric measurements.

Photo 2. Ionuț cutting the samples to be sent for radiocarbon dating.

Radiocarbon is the best age-dating method for studying the Upper Pleistocene and Holocene mammals. It is one of the most powerful scientific tools that INTEGRATE will use.

The maximum age limit up to which this method can operate is about 50,000 years. To better interpret the obtained results, regarding the paleoecology of the cave bear and the associated fauna, it is desirable to know, as precisely as possible, the period in which these animals lived.

Moreover, knowing the absolute age of the studied specimens, we can contextualize/integrate our data (stable isotopes, dental micro-wear, osteometry, etc) with climate and vegetation data obtained by other specialists, for the same period. Thus, we will be able to better understand the paleoecology of species and the reasons why some disappeared and others survived the last ice age.

A number of seven bone and tooth samples (N = 7) belonging to the species U. spelaeus were sent for radiocarbon dating at ORAU (Oxford Radiocarbon Accelerator Unit), in order to confirm/invalidate some results obtained previously at PRL (Poznan Radiocarbon Laboratory).

At the moment, they represent the youngest cave bear specimens in Europe and if confirmed by ORAU, we will have enough data that will change the previous conception regarding the extinction of the species. About 1-2 g of material (from each sample) was cut and sent for dating. For the next year, other samples are planned to be dated. This time, at PRL, one of our old collaborators, from Poland.

We will expose some technical elements of the methodology used by ORAU, for radiocarbon dating. Radiocarbon measurements are difficult to make with good precision and accuracy because carbon is an abundant element in the environment and contamination by a material of a different (generally younger) age is always possible.

For these reasons, the methods used in a radiocarbon laboratory must be rigorous, well-tested and reproducible. The unit (ORAU) has four stable isotope mass spectrometers. Two Europa Scientific instruments are used with automated gas collection systems for radiocarbon samples. Two others (Finingan and Europa Scientific) are used for stable isotope analysis.

All are usually operated in continuous flow mode (where the sample is transported in a stream of inert He gas). They are configured to measure carbon and nitrogen compositions and stable isotope ratios. Accuracies are typically between 0.1 and 0.2 per mil for δ13C and 0.3 per mil for δ15N. Once the sample has been processed into either carbon dioxide or elemental carbon (as graphite) the proportion of radiocarbon atoms in the sample is determined by AMS (Accelerator Mass Spectrometer). The Oxford AMS system was built specifically for radiocarbon dating by High Voltage Engineering Europa BV. The instrument is designed to provide very high-precision measurements on a routine basis. At ORAU, measurements are always made together with six standards of known composition and two samples of known age.

Measurements on standards and the material of known age allow a constant check of the accuracy of the data. The radiocarbon concentration can then be used to calculate the radiocarbon age of the sample (Source: https://c14.arch.ox.ac.uk/methods.html).