Papers by Guillaume Guérin
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In this study we compare different infrared stimulated luminescence (IRSL) signals for dating arc... more In this study we compare different infrared stimulated luminescence (IRSL) signals for dating archaeological deposits. The IRSL and the more recently developed post-IR IRSL (pIR-IR) methods were investigated using polymineral fine grains extracted from the Middle and Upper Palaeolithic western excavation area in the site of La Ferrassie (SW France). The IRSL data measured at 50 °C (IR50) are compared to those obtained with the elevated pIR-IR signals measured for two stimulation temperatures, 225 °C (pIR-IR225) and 290 °C (pIR-IR290). The signals are documented in terms of bleaching and fading rates. In addition, comparisons of the IR50 ages corrected either with the H + L method (Huntley and Lamothe, 2001) or with the dose rate correction method (DRC, Lamothe et al., 2003) are presented. Results show that the polymineral fine grains give a reasonable estimate of the burial age of the samples. The IR50 and pIR-IR225 provide the most reliable ages when they are corrected using the DRC method (because of saturation effects). The polymineral ages are then compared with the previously obtained ages of K-feldspars coarse grains, quartz OSL (Guerin et al., 2015) and radiocarbon ages with the aim of accessing information on the depositional processes. It appears that further comparison of polymineral fine grains to coarse grains is beneficial to evaluate bleaching. Moreover, the polymineral results either confirm or refine the chronology of the La Ferrassie sequence proposed by Guérin et al. (2015), that is, the Mousterian layers range from marine isotope stage (MIS) 5 to the middle of MIS 3. In particular, i) the base of Layer 3 is pushed back to the end of MIS 4 or beginning MIS 3 and ii) the chronological attribution of Layers 4 and 5 is confirmed as MIS 3. Finally, the chronology of the Aurignacian layer (Layer 7) is strengthened by all the feldspars results.
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Within the framework of the studies focusing on the Pleistocene peopling of the Americas, our Fre... more Within the framework of the studies focusing on the Pleistocene peopling of the Americas, our French-Brazilian team has undertaken a pluridisciplinary research on different archaeological sites, inside and in the neighborhood of the Serra da Capivara National Park, in Brazilian Nordeste. The present study regards an archaeological site, Vale da Pedra Furada, situated in the Piauí state in Brazil. The results of technological and functional studies suggest the existence of different successive human occupations during the Pleistocene in this region. Moreover, the geological and geomorphological studies shed new light on our understanding of sedimentary processes and confirm that the levels were not subject to any significant post-depositional processes. This is also confirmed by macro- and micro-analysis of quartz artefact surfaces. The chronological study has recently been completed employing both radiocarbon and luminescence techniques; radiocarbon dates were obtained on charcoal, multi-grain and single-grain OSL ages on sedimentary quartz grains. The results obtained with the different methods are consistent with each other: the most recent archaeological level is dated to around 8 ka and the oldest to 24 ka, indicating the open-air site of Vale da Pedra Furada to be a succession of human occupations beginning from OIS 2. These results are discussed in the context of some archaeological sites studied in the Serra da Capivara National Park of the last few decades.
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Boreholes drilled in 8 different rocks situated in the vicinity of the Clermont TL laboratory hav... more Boreholes drilled in 8 different rocks situated in the vicinity of the Clermont TL laboratory have been used for testing and calibrating methods devoted to measure the natural radioactivity. The present paper gives updated data for the nuclide contents and internal dose-rates for those reference media. Two examples of application are presented. The first example shows dose-rate calibration of a scintillator gamma probe using a threshold method. The second example shows a routine technique for TL dosimetry, based on the rocks for dose-rate reference.
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Located in southwest France, Roc de Marsal is a cave with a rich Mousterian stratigraphic sequenc... more Located in southwest France, Roc de Marsal is a cave with a rich Mousterian stratigraphic sequence. The lower part of the sequence (Layers 9e5) are characterized by assemblages dominated by Levallois lithic technology associated with composite faunal spectra (including red deer, roe deer and reindeer) that shows a gradual increase in the frequency of reindeer. The top of the sequence (Layers 4e2) are characterised instead by Quina lithic technology (both in terms of technology and typology) with the faunal remains dominated by reindeer. Roc de Marsal thus provides a very interesting case study to place behavioural changes in a context of changing climates and environments in western Europe during the late Pleistocene. To link the occupations at Roc de Marsal with global and regional climatic conditions known independently, a robust chronology is needed. With this aim in mind, we applied three luminescence dating methods (TL, OSL and IRSL) on different minerals (flint, quartz and K-feldspar extracts). Here the results of two of these methods are presented in detail (TL and OSL) and compared with preliminary IRSL data. At Roc de Marsal, a comparison of methods was necessary to overcome a complex sedimentary history, with very heterogeneous dose rate distributions, both at the beta (mm) and gamma (dm) dose rate scales. The results indicate that the lower Levallois layers are dated to ~65e70 ka, while overlying Quina layers are dated to ~49 ka. These ages for the lower layers fit well with some models that place mixed faunal assemblages in the initial MIS 4; however, while the Quina ages overlap with several other Quina assemblages from the region, they place the reindeer dominated fauna well after the peak cold of MIS 4 and suggest a more extended and complex period of contemporaneous lithic techno-complexes than posited by some current models.
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Encyclopedia of Earth Sciences Series, 2015
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Radiation Measurements, 2012
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Journal of Archaeological Science, 39 (10) : 3071-3084, Oct 2012
Roc de Marsal has yielded numerous remains of Mousterian occupations, including lithics, fauna an... more Roc de Marsal has yielded numerous remains of Mousterian occupations, including lithics, fauna and combustion features. It was made famous by the discovery of the skeleton of a Neanderthal child. Given the need to date the sequence, TL and OSL were applied on heated flints and quartz, and OSL on unheated quartz. Chronological results combined with palaeoenvironmental data – faunal remains and micromorphological features in the sediments from the cave, pollen proxies and faunal remains from the region – allowed us to place climate variations in southwest France on a numerical time scale. Denticulate Mousterian occupations were dated to the middle of MIS 4 (65–70 ka) and Quina layers either to the very end of MIS 4 or to MIS 3. Interestingly, a faunal pattern showing a mix of red deer, roe deer and reindeer was found to have occurred during MIS 4, which was shown to be consistent with data from other similar sites in southwest France.
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The effects of sediment heterogeneity on beta dose rate have been investigated by simulation with... more The effects of sediment heterogeneity on beta dose rate have been investigated by simulation with the DosiVox software. Basic sediment cases, as well as a model of a micro-stratified sediment from the Mas d'Azil cave have been modeled at a few centimeters scale. The results of the simulations have highlighted different factors having a significant impact on the beta dose rate dispersion, among which the heterogeneity
of the radioactive elements, the distribution of grains in the matrix and their proportion in
the sample. These factors contribute to enlarge beta dose distributions and even create complex ones, and inevitably induce errors in the dating process. These effects are discussed, as well as the potential of the simulation to calculate beta dose rates in sediment samples and the necessity of using sampling protocols adapted to sediment complexity.
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A new interdisciplinary project was initiated to excavate a portion of the Palaeolithic site of L... more A new interdisciplinary project was initiated to excavate a portion of the Palaeolithic site of La Ferrassie left intact by earlier excavations. One of the aims of this project was to provide chronological information on the succession of Middle and Upper Palaeolithic layers, as well as on the skeletons unearthed by Capitan and Peyrony in the early 1900’s. We report here preliminary results on the lithics, faunal remains, site formation processes, and on the stratigraphic context of the La Ferrassie 1 and 2 skeletons that were found adjacent to our excavations. Finally, results from luminescence dating of the sediments and a preliminary set of radiocarbon ages are presented. Quartz OSL, both at the multi-grain and single-grain levels of analysis, and post-IR IRSL of feldspar at various stimulation temperatures are compared. The quartz/feldspar comparison revealed a bleaching problem for the quartz OSL (and the feldspar pIRIR signals) from Layer 2; as a consequence, the age of this Layer was determined using a minimum age model.
A Mousterian industry with bifaces, at the base of the sequence, has been dated between 91 ± 9 and 44 ± 3 ka. The Ferrassie Mousterian layers are attributed to MIS 3, between 54 ± 3 and 40 ± 2 ka, and thus appear very late in the final Middle Palaeolithic of the region; furthermore, these ages constrain the chronology of the La Ferrassie 1 and 2 skeletons, which have been attributed to one of these Ferrassie Mousterian layers. The Châtelperronian layer is dated to 42 ± 3 ka and the Aurignacian to 37 ± 2 ka. Implications of the ages for the La Ferrassie 1 and 2 skeletons, and for the variability of late Mousterian, are discussed.
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Single grain OSL has become a widely used approach in Quaternary geochronology. However, the orig... more Single grain OSL has become a widely used approach in Quaternary geochronology. However, the origins of De distributions and the sources of variation in individual dose estimates are still poorly understood. The amount of scatter in these distributions on top of the known uncertainties in measurement and analysis is defined by overdispersion and this quantity is generally used for weighting individual De values to calculate a central equivalent dose. In this study, we address the nature and amount of different sources of dispersion in quartz single grain De estimates, by (i) using appropriate statistical tools to characterize De populations and (ii) modelling, with a specifically designed GEANT4 code, dose rate distributions arising from the presence of potassium feldspar grains in well-sorted sands. The model uses Monte Carlo simulations of beta emissions and interactions in a random close packing of quartz and feldspar spheres representing a sand sample. Based on the simulation results, we explain the discrepancy between intrinsic and natural overdispersion values in a well-bleached sample, thus validating the model. The three parameters having the most influence on dispersion in dose rate distributions, and modelled in this study, appear to be grain size, potassium content and total dose rate.
Finally an analysis of measurement uncertainties and other sources of variations in equivalent dose estimates leads us to conclude that all age models (both logged and unlogged) which include an overdispersion value to weight individual De values rely mainly on unknown parameters; this ignorance may lead to an inadvertent bias in De estimates. Assuming counting statistics make a small contribution to dispersion (as is often the case), we suggest that in some cases it is most appropriate to use unweighted averages of equivalent doses when dividing by commonly measured average dose rates.
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Papers by Guillaume Guérin
of the radioactive elements, the distribution of grains in the matrix and their proportion in
the sample. These factors contribute to enlarge beta dose distributions and even create complex ones, and inevitably induce errors in the dating process. These effects are discussed, as well as the potential of the simulation to calculate beta dose rates in sediment samples and the necessity of using sampling protocols adapted to sediment complexity.
A Mousterian industry with bifaces, at the base of the sequence, has been dated between 91 ± 9 and 44 ± 3 ka. The Ferrassie Mousterian layers are attributed to MIS 3, between 54 ± 3 and 40 ± 2 ka, and thus appear very late in the final Middle Palaeolithic of the region; furthermore, these ages constrain the chronology of the La Ferrassie 1 and 2 skeletons, which have been attributed to one of these Ferrassie Mousterian layers. The Châtelperronian layer is dated to 42 ± 3 ka and the Aurignacian to 37 ± 2 ka. Implications of the ages for the La Ferrassie 1 and 2 skeletons, and for the variability of late Mousterian, are discussed.
Finally an analysis of measurement uncertainties and other sources of variations in equivalent dose estimates leads us to conclude that all age models (both logged and unlogged) which include an overdispersion value to weight individual De values rely mainly on unknown parameters; this ignorance may lead to an inadvertent bias in De estimates. Assuming counting statistics make a small contribution to dispersion (as is often the case), we suggest that in some cases it is most appropriate to use unweighted averages of equivalent doses when dividing by commonly measured average dose rates.
of the radioactive elements, the distribution of grains in the matrix and their proportion in
the sample. These factors contribute to enlarge beta dose distributions and even create complex ones, and inevitably induce errors in the dating process. These effects are discussed, as well as the potential of the simulation to calculate beta dose rates in sediment samples and the necessity of using sampling protocols adapted to sediment complexity.
A Mousterian industry with bifaces, at the base of the sequence, has been dated between 91 ± 9 and 44 ± 3 ka. The Ferrassie Mousterian layers are attributed to MIS 3, between 54 ± 3 and 40 ± 2 ka, and thus appear very late in the final Middle Palaeolithic of the region; furthermore, these ages constrain the chronology of the La Ferrassie 1 and 2 skeletons, which have been attributed to one of these Ferrassie Mousterian layers. The Châtelperronian layer is dated to 42 ± 3 ka and the Aurignacian to 37 ± 2 ka. Implications of the ages for the La Ferrassie 1 and 2 skeletons, and for the variability of late Mousterian, are discussed.
Finally an analysis of measurement uncertainties and other sources of variations in equivalent dose estimates leads us to conclude that all age models (both logged and unlogged) which include an overdispersion value to weight individual De values rely mainly on unknown parameters; this ignorance may lead to an inadvertent bias in De estimates. Assuming counting statistics make a small contribution to dispersion (as is often the case), we suggest that in some cases it is most appropriate to use unweighted averages of equivalent doses when dividing by commonly measured average dose rates.
LF1 and LF2 were found close to our western excavation section. Field and micromorphological observations of sediments associated with the Middle Paleolithic revealed a sequence of basal fluvial sands (Layer 1) overlain successively by frost-affected, cryoturbated chalky deposits (Layer 2) and finely bedded silty sand anthropogenic deposits, rich in burned bone and flint (Layers 3, 4, and 5). Macroscopic comparisons of the sediments attached to the LF2 foot show a strong affinity to our Layer 4 and/or Layer 5, showing that the specimen clearly postdates Layer 3 [3]; a similar attempt to assign a layer to loose sediments found near LF1 was inconclusive. Although LF1 and LF2 cannot be positioned stratigraphically with certainty, our microstratigraphic results and comparisons show inconsistencies with Peyrony’s ‘yellow’ and ‘red’ attributions to the deposits associated with them. Radiocarbon and luminescence (14C, OSL, IRSL) ages attribute the Layer 4/5 deposits to MIS 3: Layer 5b was dated to between 44 and 47 ka cal BP based on radiocarbon, while luminescence ages for Layers 4 and 5 range between 40 ± 2 ka and 54 ± 4 ka [3, 4, 5].
Although the LF8 skeleton and much of the associated objects were removed during the 1970s excavation, the deposits in the area where LF8 was found are very different from those of the western section, being much stonier and generally consisting of yellow, brown silty clays with generally platy éboulis. We excavated this area of the site and recognized several layers: Layer A (base) through Layer D (top). Evaluation of Delporte’s records showed that the LF8 child was most probably at the same elevation as our Layer B. The underlying Layer A, along with the base of Layer B, were deformed by the formation of several cryogenic patterned ground hummock formations. Similar features (called “monticules”) were recorded during Peyrony’s excavations [1]. This deformation likely occurred at the same time as the deposition of Layer 2 in the western section. Therefore, from a stratigraphic standpoint, Layer B appears to be the temporal equivalent of Layer 2 in the western area. A preliminary OSL age for sediments from the same altitude as LF8 suggests that it dates to MIS 4 (~66 ka). OSL ages obtained for Layer 2 in the western area [3, 4] are consistent with this preliminary age and support the link between these two Layers. In the remaining deposits, there were no indications for a distinct infill in this area, neither in the profile nor in the artifact plots. Fauna associated with LF8 are currently being radiocarbon dated. There are also clear differences in artifact density in these different loci of the site, with LF8 associated with archaeologically poor Middle Paleolithic sediments as compared with the artifact-rich deposits further toward the western section where LF1 and LF2 were uncovered. Thus, when considered in their totality, all of the data clearly show that LF1 and LF2 are stratigraphically above the sediments that were at the same level as LF8.