Development of the Rennes Luminescence Dating Laboratory (RenDaL)

The Brittany region, Rennes Métropole and CNRS fund the creation of a new geochronology laboratory within the OSUR.
 Mesolithic site of Beg-er-Vil, southern Brittany.

Guillaume Guérin, CNRS scientist laureate of an ERC grant, became affiliated with Geosciences Rennes on Nov. 1, 2020. At OSUR he wishes to setup a luminescence dating laboratory, not only to fulfil his research projects dedicated to Neanderthals (the ERC project called Quina World started January 1, 2021) but also to add a geochronological method in the Breton research landscape. Luminescence dating can indeed cover periods from a few years to several hundred thousand millennia, a time range that was not accessible in the region so far.

Luminescence dating applications cover a wide range of research problematics in the fields of archaeology and geology, the two areas covered inside OSUR by the CReAAH and Geosciences Rennes, respectively. At a regional scale, interactions with other universities (those of southern Brittany and Brest in particular) are expected.

Luminescence consists of light emission resulting from the recombination of an electron-hole pair in crystalline material such as quartz or feldspar. Indeed, electrons are trapped when set in motion in the crystal by environmental radioactivity and are freed by light exposure or heat. This trapping/detrapping phenomena allow dating the last exposure of mineral grains forming sediment, or rocks, to sunlight. Luminescence-based thermochronometry may also shed light on the cooling of exhumed rocks an thus provide information on the interplay between tectonics, erosion and climate.

Luminescence émise par des grains de sédiments (ici stimulée avec un faisceau d'électrons). La datation par OSL (Luminescence Stimulée Optiquement) consiste à mesurer la luminescence émise lors d'une stimulation optique : plus le signal est intense et plus l'échantillon est ancien. L'évènement daté est alors la dernière remise à zéro du signal, typiquement lors de l'exposition à la lumière durant le transport des sédiments. Fig 1 : Luminescence emitted by sediment grains (here stimulated with an electron beam). Optically Stimulated Dating (OSL) consists of measuring the amount of luminescence emitted upon optical stimulation: the brighter the signal, the older is the sediment.

Ongoing collaborations include, among other studies, the dating of the archaeological site of Beg-er-Vil in southern Brittany, excavated by G. Marchand and C. Dupont (CReAAH).

Mesolithic site of Beg-er-Vil, southern Brittany. Fig 2 : Mesolithic site of Beg-er-Vil, southern Brittany.

Future collaborations should focus on e.g. the chronology of marine cores off the coast of Ecuador, to better valuate seismic hazards in the area.

Figure 3. the North coast of Ecuador is a subduction zone implying serious seismic hazards. Sediment analysis and dating should allow a better understanding of the coupling between the tectonic plates. Fig 3. the North coast of Ecuador is a subduction zone implying serious seismic hazards. Sediment analysis and dating should allow a better understanding of the coupling between the tectonic plates.