Direct dating in archaeology
In order to carry out this dating, a leading-edge methodology was employed, combining high-resolution Uranium-Thorium analysis using laser ablation coupled to a mass spectrometer and measurements of a fragment of enamel by Electron Spin Resonance (ESR).
"We used the same special protocol that had previously worked successfully with the fossil remains of Homo naledi and the oldest Homo sapiens found outside Africa" says Mathieu Duval, member of the Geochronology and Geology Program of the CENIEH and now at the Australian Research Center for Human Evolution at Griffith University (Australia) "By combining direct dating of the piece with a new, more precise paleomagnetic study of the deposits of the stratigraphic unit TD6, it was possible to obtain a dating which is consistent with the previous indirect estimates based on the sediment or fauna associated to the hominin remains," the researcher adds.
In fact, relatively recently the chronology of the level TD4, where the oldest lithic industries of the site were identified, was successfully refined.
In TD1, it has likewise been possible to date a level at the base of the sedimentary fillings, where a change of magnetic polarity, identified as the Jaramillo event, was observed: this is very difficult to detect at archaeological sites in caves and it marks a very well-defined moment approximately one million years ago.
Gran Dolina: a dating undergoing constant evolution With the constant improvement over time of the analytical techniques and dating methods, it has been possible to progressively refine the chronology of the archaeological site of Gran Dolina since its initial study, published in 1995.
The present work joins other recent studies centering on the lower levels.
Now, maybe I didn't see the optimal stuff--that's a possibility.
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Geologist Matthew Bennett of Bournemouth University, who discovered the tracks together with Gonzalez and David Huddart (also of Liverpool John Moores), is heading up an innovative program of mapping and scanning at the site.