Philippe lanos - Academia.edu (original) (raw)

Papers by Philippe lanos

Quaternary Science Reviews, 2019

Investigations of chronology play a key role in the majority of archaeological research endeavors... more Investigations of chronology play a key role in the majority of archaeological research endeavors and are particularly pertinent to examinations of culture-environment relationships, especially during periods characterized by rapid and marked climatic variability and environmental reorganization. Rigorous evaluations of available data and robust methods are required if one wishes to reconstruct reliable chronologies, and this is especially the case when examining periods that are associated with a relatively few radiometric measurements. Such is the case for the Upper Paleolithic archaeological record documented in present-day France from 32,000 to 21,000 calibrated years BP. We take into account critically examined radiocarbon measurements from contextually secure archaeological contexts and employ a recently-developed method of Hierarchical Bayesian Modeling to reconstruct the chronology of archaeological cultures from the Middle Gravettian to the Badegoulian. The calculated chronological 2 intervals for each typo-technologically defined culture phase are compared to the Greenland ice core climatic record and a terrestrial paleoenvironmental record from Bergsee Lake (Southern Germany)-itself expressed in calendar years calculated with the same calibration curve employed in our age model-thereby permitting each archaeological culture to be correlated accurately with documented paleoclimatic variability.

Physics of the Earth and Planetary Interiors, 2000

Twenty new paleointensity determinations have been obtained from archaeomagnetic sites from Franc... more Twenty new paleointensity determinations have been obtained from archaeomagnetic sites from France. Time intervals investigated range from 65 to 380 AD and from 1370 to 1700 AD. Two hundred forty-two samples of tiles and bricks were treated with the classical Thellier method for paleointensity determination. Rock magnetic studies identify magnetite, substituted maghemite and hematite as the main magnetic minerals. As

Geophysical Journal International, 2007

An intensive archaeomagnetic investigation of an Italian Roman amphorae workshop has been carried... more An intensive archaeomagnetic investigation of an Italian Roman amphorae workshop has been carried out in order to produce high quality data to enhance the European archaeomagnetic database. Additionally, and importantly, this study also investigates within and between structure variations and, the influence of anisotropy and cooling rate corrections. Eighty-six oriented samples were taken from five kilns for full geomagnetic vector (directions and intensity) determination. Additionally, cores from 39 amphorae found at the site were drilled for archaeointensity analysis. The site is archaeologically dated as being between 2nd century BC and 1st century AD, and the amphorae as being 1st century BC. A full suite of rock magnetic experiments were carried out which indicate the samples' suitability for archaeointensity experiments. The classical Thellier method with correction for anisotropy of thermal remanence (TRM) was used to determine the direction of the characteristic remanence and the archaeointensity. Differences between fast and slow cooling during remanence acquisition were investigated and a cooling rate correction applied to the archaeointensity estimates. After correction for anisotropy of TRM, the scatter about the kiln (amphorae) mean value is reduced and the scatter between kilns is also reduced for both directions and archaeointensity, demonstrating the necessity of carrying out the anisotropy of TRM correction for these samples. Application of the cooling rate correction results in a decrease in archaeointensity as expected on theoretical grounds for single domain grains. The correction, whilst not reducing scatter in the mean archaeointensity results, does result in a reduction in the scatter found between the kilns. The directional results are compared to the French, and a preliminary Italian, secular variation (SV) curve and suggest that the kilns may be towards the older limit of the archaeologically given age however the master curves are not well constrained in this time interval. Instead, the five new directional data should be used to help constrain future curves. The Albinia archaeointensity data are consistent with the broad trends seen in the limited high quality Western European and Mesopotamian data sets and with the newly constructed archaeointensity SV curve for Greece. Similar to other studies whilst the archaeointensity results for each kiln (the amphorae) are well constrained (4-7 per cent scatter about the mean) variations are seen between the kilns (mean archaeointensity 62-70 μT). This further supports the suggestion that it is necessary to obtain a number of archaeointensity data for each time Downloaded from 472 M. J. Hill et al.

Global geomagnetic models using archaeomagnetic data can offer important insights in to geomagnet... more Global geomagnetic models using archaeomagnetic data can offer important insights in to geomagnetic field evolution and core mantle boundary processes. However, in order to provide a complete field description it is necessary to have many data giving good spatial and temporal coverage. Due mainly to experimental difficulties there are many more directional data than intensity data, and whilst data coverage

Hervé Gwenaël, Chauvin Annick & Lanos Philippe, 2013

In order to extend the secular variation curve (SVC) of archaeointensity in Western Europe to the... more In order to extend the secular variation curve (SVC) of archaeointensity in Western Europe to the first millennium BC, we studied 24 kilns and hearths in place, 2 displaced hearths and 6 sets of pottery sherds from French archaeological sites. Archaeological artefacts, radiocarbon and dendrochronology dated the acquisition of the thermoremanent magnetization (TRM) carried by the studied objects. Rock magnetism experiments suggest that the main carrier of the magnetization is a Ti-poor titanomagnetite. Archaeointensity was determined by the Thellier-Thellier classical protocol with pTRM-checks. A strict criteria set was applied to select only the most reliable results with linear NRM-TRM diagrams (55% of total specimens). This study demonstrates that pottery sherds with two TRMs give reliable archaeointensities in the low-temperature interval, if the NRM-TRM diagram is adequately adjusted. Eighteen new mean archaeointensities (14 corrected from the anisotropy of TRM and 16 from cooling rate) were computed. The comparison with previously published Western Europe paleointensities show a strong dispersion between data primarily due to their variable quality. Western Europe data were weighted following the archaeointensity protocol, the number of specimens per site and the type of studied materials, in order to better highlight the secular variation of archaeointensity during the first millennium BC. The SVC, built with sliding windows of 160 years shifted every 50 years, presents (at Paris) a maximum of 90µT around 800BC and a minimum of 60µT around 250BC. These archaeointensity maximum and minimum correspond to cusps of the geomagnetic field direction in Western Europe. This new curve is consistent with Mesopotamian and Eastern Europe data. The archaeointensity secular variation in Western Europe predicted by global geomagnetic models CALS3k.4, ARCH3k.1 and ARCH3k_cst.1 is smoother than our SVC. We used our directional dataset (Hervé et al., 2012a) to build a new Western Europe VGPs and VDMs mean curves. Comparison with the predictions given by the global models points out a possible persistent non-dipole fields effect over Europe between 1000BC and 600-500BC. Finally, we note that the strong variations of intensity of the geomagnetic field (with a mean decrease rate per century close to 6µT) will be useful for archaeomagnetic dating purposes.

A partir de l'étude d'un édifice phare de l'Ouest de la France (Eglise Notre-Dame sous Terre au M... more A partir de l'étude d'un édifice phare de l'Ouest de la France (Eglise Notre-Dame sous Terre au Mont-Saint-Michel) mous montrons comment le couplage des études de bâti permettant l'identification d'ensembles maçonnés et leur chronologie relative, avec les méthodes de datation des terres cuites par thermoluminescence et archéomagnétisme, et des charbons de mortier par radiocarbone, aboutit à des informations particulièrement novatrices sur la chronologie de la production des briques, leur éventuel remploi ou sur leur production ad nove, mais aussi, plus inattendu, sur des éléments technologiques de leur production. Les orientations actuelles des recherches méthodologiques pour la datation physique des structures bâties sont également mises en perspective.

Geochronometria, 2011

St Martin's church, Angers, is emblematic of the problems raised in pre-12 th century history of ... more St Martin's church, Angers, is emblematic of the problems raised in pre-12 th century history of architecture. In view of the importance of this building, it was necessary to attempt to define its dating and this study particularly focuses on its bell-tower. In addition to the conclusion resulting from the interpretation of written sources and typological criteria positioning the construction of the site at the beginning of the 11 th century, not only a significant number of 14 C dates were carried out on charcoals from the masonry structures, but also independent dating by archaeomagnetism and thermoluminescence were performed on bricks from the bell-tower. The whole results from these three different methods agree and indicate the lower level of the bell-tower was likely built in the 9 th century, disputing evidence to the theory of construction in the 11 th century of the church. Presented here are the detailed results obtained from the thermoluminescence (TL) dating analysis.

Geophysical Journal International, 2007

An intensive archaeomagnetic investigation of an Italian Roman amphorae workshop has been carried... more An intensive archaeomagnetic investigation of an Italian Roman amphorae workshop has been carried out in order to produce high quality data to enhance the European archaeomagnetic database. Additionally, and importantly, this study also investigates within and between structure variations and, the influence of anisotropy and cooling rate corrections. Eighty-six oriented samples were taken from five kilns for full geomagnetic vector (directions and intensity) determination. Additionally, cores from 39 amphorae found at the site were drilled for archaeointensity analysis. The site is archaeologically dated as being between 2nd century BC and 1st century AD, and the amphorae as being 1st century BC. A full suite of rock magnetic experiments were carried out which indicate the samples' suitability for archaeointensity experiments. The classical Thellier method with correction for anisotropy of thermal remanence (TRM) was used to determine the direction of the characteristic remanence and the archaeointensity. Differences between fast and slow cooling during remanence acquisition were investigated and a cooling rate correction applied to the archaeointensity estimates. After correction for anisotropy of TRM, the scatter about the kiln (amphorae) mean value is reduced and the scatter between kilns is also reduced for both directions and archaeointensity, demonstrating the necessity of carrying out the anisotropy of TRM correction for these samples. Application of the cooling rate correction results in a decrease in archaeointensity as expected on theoretical grounds for single domain grains. The correction, whilst not reducing scatter in the mean archaeointensity results, does result in a reduction in the scatter found between the kilns. The directional results are compared to the French, and a preliminary Italian, secular variation (SV) curve and suggest that the kilns may be towards the older limit of the archaeologically given age however the master curves are not well constrained in this time interval. Instead, the five new directional data should be used to help constrain future curves. The Albinia archaeointensity data are consistent with the broad trends seen in the limited high quality Western European and Mesopotamian data sets and with the newly constructed archaeointensity SV curve for Greece. Similar to other studies whilst the archaeointensity results for each kiln (the amphorae) are well constrained (4-7 per cent scatter about the mean) variations are seen between the kilns (mean archaeointensity 62-70 μT). This further supports the suggestion that it is necessary to obtain a number of archaeointensity data for each time http://gji.oxfordjournals.org/ Downloaded from 472 M. J. Hill et al.

Physics of the Earth and Planetary Interiors, 2000

Twenty new paleointensity determinations have been obtained from archaeomagnetic sites from Franc... more Twenty new paleointensity determinations have been obtained from archaeomagnetic sites from France. Time intervals investigated range from 65 to 380 AD and from 1370 to 1700 AD. Two hundred forty-two samples of tiles and bricks were treated with the classical Thellier method for paleointensity determination. Rock magnetic studies identify magnetite, substituted maghemite and hematite as the main magnetic minerals. As

Global geomagnetic models using archaeomagnetic data can offer important insights in to geomagnet... more Global geomagnetic models using archaeomagnetic data can offer important insights in to geomagnetic field evolution and core mantle boundary processes. However, in order to provide a complete field description it is necessary to have many data giving good spatial and temporal coverage. Due mainly to experimental difficulties there are many more directional data than intensity data, and whilst data coverage is reasonable for some locations it is recognised that many more high quality data are still needed. Here we present results from two Italian sites: a Roman Amphorae workshop (dated to be between 200 BC and 100 AD), Albinia, Tuscany, and from a 7th Century BC site at Incoronata, Pisticii, Basilicata. The classical Thellier technique was used with anisotropy of thermal remanence and cooling rate corrections. At Albinia, samples were taken from five kilns and from the base of 39 amphorae. The mean archaeointensity per kiln / the amphorae range from 62 to 70 microT. This variation may reflect them being of differing ages however it could also reflect the limitations of the experimental protocol and/or samples. Thus it is desirable that a number of archaeointensity data per time interval are obtained in order to reliably determine the past variations of the geomagnetic field. At Incoronata samples were drilled from 39 bricks. The mean archaeointensity of 85 microT obtained for the older Incoronata bricks is consistent with the increase in field intensity seen going back through the first millennia BC in other regions such as Mesopotamia.

Archaeometry, 1987

Magnetic and other measurements are reported for the Guehenno II Gallo-Roman hoard (56-France) wh... more Magnetic and other measurements are reported for the Guehenno II Gallo-Roman hoard (56-France) which, amongst several thousand Tetricus antoniniani, contains 275 coins struck with the same dies. The orientation of the remanent magnetization is systematically directed outwards from the obverse confirming the identity of the anvil die with the obverse. The magnetization vector is statistically distributed around the vertical axis giving no indication of the geomagnetic inclination at the time of striking. Consequently ancient struck coins cannot be used for dating. The origin of the remanent magnetization was also investigated.

Geophysical Journal International, 2005

The German archaeomagnetic data set was supplemented with 35 new directions from German sites mai... more The German archaeomagnetic data set was supplemented with 35 new directions from German sites mainly dating from the past 3000 yr. Together with archaeomagnetic data from the neighbouring countries of Germany a database of 166 reliable archaeomagnetic directions has been compiled for the reference area, which is defined by a 500-km-radius circle around Göttingen. The retrieved directions come from well-dated archaeological structures and about 40 per cent of the dating relay on natural science methods such as radiocarbon, thermoluminescence, dendrochronology dating or historical documents. From this data set a secular variation (SV) reference curve has been calculated using a bivariate algorithm, which fits a natural cubic spline based on roughness penalty to declination, inclination and time, simultaneously. The error tube surrounding this curve was obtained from Bayesian modelling of the experimental errors, which can also take stratigraphic information into account. The obtained SV reference curve for the past 2500 yr is similar to that from France, but also significant differences are seen. Comparison of the curves does not show a simple westward drift of the SV pattern. The German reference curve allows archaeomagnetic dating in the reference area and extends this dating technique to sites situated in middle Europe.

Variations of the Earth magnetic field during the first millennium B.C. in Western Europe remain ... more Variations of the Earth magnetic field during the first millennium B.C. in Western Europe remain not very well constrained, especially archeointensity. Three salt-kilns (MOA, MOB and MOC) sampled in Moyenvic (Lorraine, Eastern France) have been studied to provide new reference data. Each kiln has been dated by radiocarbon in the First Iron Age or Hallstatt period (between VIII and Vth Century BC). Paleomagnetic experiments have been carried out both in laboratories of Leoben (Austria) and Rennes (France). Rock magnetic experiments and hysteresis results suggest the predominance of pseudo single domain (PSD) grains close Ti-poor magnetite. Archeomagnetic directions have been obtained by thermal and alternating field demagnetizations. High values of mean inclination and declination are observed (declination between 19° to 31° and inclination close to 70°). Classical Thellier-Thellier experiments were first conducted on 51 samples with a laboratory field almost parallel to the direction of the characteristic remanent magnetization (ChRM). Even if pTRM checks are positive, the very large dispersion observed within the paleointensity values determined has suggested that some artefacts have not been well recognized. In a second step, Thellier experiments have been conducted on 36 sister specimens with the laboratory field quasi-perpendicular to ChRM. In these cases, mineralogical evolutions during heating and chemical remanent magnetization acquisitions have clearly been recognized. For the whole sample suite the success rate of the palaeointensity determinations is very low with 80% of the samples rejected. Nevertheless, reliable mean archeointensities have been obtained for two of the three kilns (MOA, 77.0 ± 15.2 µT and MOB, 89.2 ± 7.0 µT at the latitude of Paris). The high field strength and the archeomagnetic directions determined, provide further evidence for important changes of the Earth magnetic field in Europe during the first half of the first millennium BC. Large variations of the geomagnetic field during First Iron Age indicate that archeomagnetism should be very efficient to date archaeological structures of this period.

Geochemistry Geophysics Geosystems, 2006

1] A first secular variation (SV) curve for the Iberian Peninsula was computed by hierarchical Ba... more 1] A first secular variation (SV) curve for the Iberian Peninsula was computed by hierarchical Bayesian method using a total of 134 archaeomagnetic directions with ages ranging from À775 to 1959 A.D. A general agreement is observed between the Iberian curve and the French and German SV curves, although some interesting differences were found, such as the occurrence of lower inclinations between the 11th and 14th centuries in the Iberian curve. The analysis of these three reference curves indicates that SV in western Europe is characterized by three major directional changes at À125, 200, and 1350 A.D. It is suggested that these cusps are regional features of the geomagnetic field. The Iberian curve has been compared with the predictions of the Jackson, CALSK7K.2, and Hongre global models. Despite large differences recognized between these models, even for the dipolar terms, they predict reasonably well the Iberian archaeomagnetic SV.

Journal of Geophysical Research, 2003

Citation: Schnepp, E., R. Pucher, C. Goedicke, A. Manzano, U. Müller, and P. Lanos, Paleomagnetic... more Citation: Schnepp, E., R. Pucher, C. Goedicke, A. Manzano, U. Müller, and P. Lanos, Paleomagnetic directions and thermoluminescence dating from a bread oven-floor sequence in Lübeck (Germany): A record of 450 years of geomagnetic secular variation,

Geophysical Journal International, 2011

Variations of the Earth's magnetic field during the first millennium BC in western Europe remain ... more Variations of the Earth's magnetic field during the first millennium BC in western Europe remain poorly constrained, especially archaeointensity changes. Three salt-kilns (MOA, MOB and MOC) sampled in Moyenvic (Lorraine, eastern France) have been studied to provide new reference data. Each kiln has been dated by radiocarbon to originate from the Early Iron Age or Hallstatt period (between VIII and Vth Century BC). Rock magnetic experiments and hysteresis results suggest the predominance of pseudo-single domain (PSD) Ti-poor magnetite. Archaeomagnetic directions obtained by thermal and alternating field demagnetizations have high mean inclination (close to 70°) and declination (between 19 and 31°). A first set of classical Thellier-Thellier experiments was conducted on 46 samples with a laboratory field almost parallel to the direction of the characteristic remanent magnetization (ChRM). Only 24 of these specimens present a linear NRM-TRM plot. For other specimens, NRM-TRM plots are concave-up with positive pTRM checks. The very large dispersion observed between the determined palaeointensity values suggests some artefacts have not been fully recognized. A second set of Thellier experiments was conducted on 34 sister specimens with the laboratory field applied quasi-perpendicular to the ChRM. In these cases, mineralogical evolutions during heating and chemical remanent magnetization acquisitions have been clearly recognized, despite positive pTRM checks. The concave-up shapes of NRM-TRM plots appear mainly due to mineralogical alteration rather than to the presence of PSD-MD grains. For the entire set of samples the success rate of the palaeointensity determinations is very low with 80 per cent of the samples rejected. Nevertheless, reliable mean archaeointensities have been obtained for two of the three kilns (MOA, 80.1 ± 14.5 μT and MOB, 86.6 ± 6.9 μT at the latitude of Paris). The high field strength and the archaeomagnetic directions determined, combined with previous published data, provide further evidence for important changes of the Earth magnetic field in Europe during the first half of the first millennium BC. These large variations of the geomagnetic field during the Iron Ages indicate that archaeomagnetism is highly suitable for dating of structures from this period.

Geophysical Journal International, 2007

An intensive archaeomagnetic investigation of an Italian Roman amphorae workshop has been carried... more An intensive archaeomagnetic investigation of an Italian Roman amphorae workshop has been carried out in order to produce high quality data to enhance the European archaeomagnetic database. Additionally, and importantly, this study also investigates within and between structure variations and, the influence of anisotropy and cooling rate corrections. Eighty-six oriented samples were taken from five kilns for full geomagnetic vector (directions and intensity) determination. Additionally, cores from 39 amphorae found at the site were drilled for archaeointensity analysis. The site is archaeologically dated as being between 2nd century BC and 1st century AD, and the amphorae as being 1st century BC. A full suite of rock magnetic experiments were carried out which indicate the samples' suitability for archaeointensity experiments. The classical Thellier method with correction for anisotropy of thermal remanence (TRM) was used to determine the direction of the characteristic remanence and the archaeointensity. Differences between fast and slow cooling during remanence acquisition were investigated and a cooling rate correction applied to the archaeointensity estimates. After correction for anisotropy of TRM, the scatter about the kiln (amphorae) mean value is reduced and the scatter between kilns is also reduced for both directions and archaeointensity, demonstrating the necessity of carrying out the anisotropy of TRM correction for these samples. Application of the cooling rate correction results in a decrease in archaeointensity as expected on theoretical grounds for single domain grains. The correction, whilst not reducing scatter in the mean archaeointensity results, does result in a reduction in the scatter found between the kilns. The directional results are compared to the French, and a preliminary Italian, secular variation (SV) curve and suggest that the kilns may be towards the older limit of the archaeologically given age however the master curves are not well constrained in this time interval. Instead, the five new directional data should be used to help constrain future curves. The Albinia archaeointensity data are consistent with the broad trends seen in the limited high quality Western European and Mesopotamian data sets and with the newly constructed archaeointensity SV curve for Greece. Similar to other studies whilst the archaeointensity results for each kiln (the amphorae) are well constrained (4-7 per cent scatter about the mean) variations are seen between the kilns (mean archaeointensity 62-70 μT). This further supports the suggestion that it is necessary to obtain a number of archaeointensity data for each time interval in order to reliably record variations of the Earth's magnetic field from archaeological material. The archaeointensity result for the set of amphorae which has the better constrained age falls within the archaeointensity values from the kilns. Combining the results from the five kilns and the amphorae gives a mean archaeointensity of 64 +/- 3 μT at Albinia (69 +/- 3 μT relocated to Paris) during 200 BC-100 AD.

Geophysical Journal International, 2006

The construction of a secular variation (SV) reference curve for a region for which little or no ... more The construction of a secular variation (SV) reference curve for a region for which little or no archaeomagnetic directions are available is presented here. A SV curve is illustrated for Austria, centred on Radstadt (47.38°N, 13.45°E) and based on data from sites in other countries less than 500 km away. The published data were selected on site characteristics of N≥ 3 and k≥ 50, and dated within 400 yr. This yielded 170 directions from which a SV curve was derived using Bayesian techniques. The obtained reference curve represents the past 2300 yr. New data, mainly from Austria, substantiate this curve and confirm the validity of the techniques employed which can, therefore, be applied for similar situations. Another test has been made using the German reference curve for dating the Austrian archaeological sites, here a systematic shift to older times in the order 30–110 yr occurs.

Directional archaeomagnetic reference curves have been published for Austria and Germany some yea... more Directional archaeomagnetic reference curves have been published for Austria and Germany some years ago. Recent determination of new archaeomagnetic directions was mainly concentrated on time intervals with only sparse data. About 60 new directions have been obtained and further 25 new archaeointensities have been determined. The past 3500 years are now covered with one or two intensity values per century, all associated with direction. The data base for direction is much larger and in the order of ten directions per century. Examination of velocity and curvature of the archaeomagnetic calibration curves yielded four major directional changes (sometimes called 'archaeomagnetic jerks'), which are found in Central Europe and all over Europe at the same time. A fifth 'archaeomagnetic jerk' occurring in the 8th century BC is also well documented in the new data. Using the updated archaeomagnetic data set from this study, the hypothesis of correlation between 'archaeomagnetic jerks' and high intensity has been tested. It is not supported by the new results, especially not by the full vector data. However, rapid variations in direction as well as in archaeointensity on centennial timescale are observed during the past 3500 years. In particular, two very pronounced intensity highs occur in the 5th century BC and the 8th century AD. In both cases, archaeointensity increased with a rate of more than 10 µT per 100 yrs during the preceding centuries.

Journal of Geophysical Research, 2003

Citation: Schnepp, E., R. Pucher, C. Goedicke, A. Manzano, U. Müller, and P. Lanos, Paleomagnetic... more Citation: Schnepp, E., R. Pucher, C. Goedicke, A. Manzano, U. Müller, and P. Lanos, Paleomagnetic directions and thermoluminescence dating from a bread oven-floor sequence in Lübeck (Germany): A record of 450 years of geomagnetic secular variation,

Quaternary Science Reviews, 2019

Investigations of chronology play a key role in the majority of archaeological research endeavors... more Investigations of chronology play a key role in the majority of archaeological research endeavors and are particularly pertinent to examinations of culture-environment relationships, especially during periods characterized by rapid and marked climatic variability and environmental reorganization. Rigorous evaluations of available data and robust methods are required if one wishes to reconstruct reliable chronologies, and this is especially the case when examining periods that are associated with a relatively few radiometric measurements. Such is the case for the Upper Paleolithic archaeological record documented in present-day France from 32,000 to 21,000 calibrated years BP. We take into account critically examined radiocarbon measurements from contextually secure archaeological contexts and employ a recently-developed method of Hierarchical Bayesian Modeling to reconstruct the chronology of archaeological cultures from the Middle Gravettian to the Badegoulian. The calculated chronological 2 intervals for each typo-technologically defined culture phase are compared to the Greenland ice core climatic record and a terrestrial paleoenvironmental record from Bergsee Lake (Southern Germany)-itself expressed in calendar years calculated with the same calibration curve employed in our age model-thereby permitting each archaeological culture to be correlated accurately with documented paleoclimatic variability.

Physics of the Earth and Planetary Interiors, 2000

Twenty new paleointensity determinations have been obtained from archaeomagnetic sites from Franc... more Twenty new paleointensity determinations have been obtained from archaeomagnetic sites from France. Time intervals investigated range from 65 to 380 AD and from 1370 to 1700 AD. Two hundred forty-two samples of tiles and bricks were treated with the classical Thellier method for paleointensity determination. Rock magnetic studies identify magnetite, substituted maghemite and hematite as the main magnetic minerals. As

Geophysical Journal International, 2007

An intensive archaeomagnetic investigation of an Italian Roman amphorae workshop has been carried... more An intensive archaeomagnetic investigation of an Italian Roman amphorae workshop has been carried out in order to produce high quality data to enhance the European archaeomagnetic database. Additionally, and importantly, this study also investigates within and between structure variations and, the influence of anisotropy and cooling rate corrections. Eighty-six oriented samples were taken from five kilns for full geomagnetic vector (directions and intensity) determination. Additionally, cores from 39 amphorae found at the site were drilled for archaeointensity analysis. The site is archaeologically dated as being between 2nd century BC and 1st century AD, and the amphorae as being 1st century BC. A full suite of rock magnetic experiments were carried out which indicate the samples' suitability for archaeointensity experiments. The classical Thellier method with correction for anisotropy of thermal remanence (TRM) was used to determine the direction of the characteristic remanence and the archaeointensity. Differences between fast and slow cooling during remanence acquisition were investigated and a cooling rate correction applied to the archaeointensity estimates. After correction for anisotropy of TRM, the scatter about the kiln (amphorae) mean value is reduced and the scatter between kilns is also reduced for both directions and archaeointensity, demonstrating the necessity of carrying out the anisotropy of TRM correction for these samples. Application of the cooling rate correction results in a decrease in archaeointensity as expected on theoretical grounds for single domain grains. The correction, whilst not reducing scatter in the mean archaeointensity results, does result in a reduction in the scatter found between the kilns. The directional results are compared to the French, and a preliminary Italian, secular variation (SV) curve and suggest that the kilns may be towards the older limit of the archaeologically given age however the master curves are not well constrained in this time interval. Instead, the five new directional data should be used to help constrain future curves. The Albinia archaeointensity data are consistent with the broad trends seen in the limited high quality Western European and Mesopotamian data sets and with the newly constructed archaeointensity SV curve for Greece. Similar to other studies whilst the archaeointensity results for each kiln (the amphorae) are well constrained (4-7 per cent scatter about the mean) variations are seen between the kilns (mean archaeointensity 62-70 μT). This further supports the suggestion that it is necessary to obtain a number of archaeointensity data for each time Downloaded from 472 M. J. Hill et al.

Global geomagnetic models using archaeomagnetic data can offer important insights in to geomagnet... more Global geomagnetic models using archaeomagnetic data can offer important insights in to geomagnetic field evolution and core mantle boundary processes. However, in order to provide a complete field description it is necessary to have many data giving good spatial and temporal coverage. Due mainly to experimental difficulties there are many more directional data than intensity data, and whilst data coverage

Hervé Gwenaël, Chauvin Annick & Lanos Philippe, 2013

In order to extend the secular variation curve (SVC) of archaeointensity in Western Europe to the... more In order to extend the secular variation curve (SVC) of archaeointensity in Western Europe to the first millennium BC, we studied 24 kilns and hearths in place, 2 displaced hearths and 6 sets of pottery sherds from French archaeological sites. Archaeological artefacts, radiocarbon and dendrochronology dated the acquisition of the thermoremanent magnetization (TRM) carried by the studied objects. Rock magnetism experiments suggest that the main carrier of the magnetization is a Ti-poor titanomagnetite. Archaeointensity was determined by the Thellier-Thellier classical protocol with pTRM-checks. A strict criteria set was applied to select only the most reliable results with linear NRM-TRM diagrams (55% of total specimens). This study demonstrates that pottery sherds with two TRMs give reliable archaeointensities in the low-temperature interval, if the NRM-TRM diagram is adequately adjusted. Eighteen new mean archaeointensities (14 corrected from the anisotropy of TRM and 16 from cooling rate) were computed. The comparison with previously published Western Europe paleointensities show a strong dispersion between data primarily due to their variable quality. Western Europe data were weighted following the archaeointensity protocol, the number of specimens per site and the type of studied materials, in order to better highlight the secular variation of archaeointensity during the first millennium BC. The SVC, built with sliding windows of 160 years shifted every 50 years, presents (at Paris) a maximum of 90µT around 800BC and a minimum of 60µT around 250BC. These archaeointensity maximum and minimum correspond to cusps of the geomagnetic field direction in Western Europe. This new curve is consistent with Mesopotamian and Eastern Europe data. The archaeointensity secular variation in Western Europe predicted by global geomagnetic models CALS3k.4, ARCH3k.1 and ARCH3k_cst.1 is smoother than our SVC. We used our directional dataset (Hervé et al., 2012a) to build a new Western Europe VGPs and VDMs mean curves. Comparison with the predictions given by the global models points out a possible persistent non-dipole fields effect over Europe between 1000BC and 600-500BC. Finally, we note that the strong variations of intensity of the geomagnetic field (with a mean decrease rate per century close to 6µT) will be useful for archaeomagnetic dating purposes.

A partir de l'étude d'un édifice phare de l'Ouest de la France (Eglise Notre-Dame sous Terre au M... more A partir de l'étude d'un édifice phare de l'Ouest de la France (Eglise Notre-Dame sous Terre au Mont-Saint-Michel) mous montrons comment le couplage des études de bâti permettant l'identification d'ensembles maçonnés et leur chronologie relative, avec les méthodes de datation des terres cuites par thermoluminescence et archéomagnétisme, et des charbons de mortier par radiocarbone, aboutit à des informations particulièrement novatrices sur la chronologie de la production des briques, leur éventuel remploi ou sur leur production ad nove, mais aussi, plus inattendu, sur des éléments technologiques de leur production. Les orientations actuelles des recherches méthodologiques pour la datation physique des structures bâties sont également mises en perspective.

Geochronometria, 2011

St Martin's church, Angers, is emblematic of the problems raised in pre-12 th century history of ... more St Martin's church, Angers, is emblematic of the problems raised in pre-12 th century history of architecture. In view of the importance of this building, it was necessary to attempt to define its dating and this study particularly focuses on its bell-tower. In addition to the conclusion resulting from the interpretation of written sources and typological criteria positioning the construction of the site at the beginning of the 11 th century, not only a significant number of 14 C dates were carried out on charcoals from the masonry structures, but also independent dating by archaeomagnetism and thermoluminescence were performed on bricks from the bell-tower. The whole results from these three different methods agree and indicate the lower level of the bell-tower was likely built in the 9 th century, disputing evidence to the theory of construction in the 11 th century of the church. Presented here are the detailed results obtained from the thermoluminescence (TL) dating analysis.

Geophysical Journal International, 2007

An intensive archaeomagnetic investigation of an Italian Roman amphorae workshop has been carried... more An intensive archaeomagnetic investigation of an Italian Roman amphorae workshop has been carried out in order to produce high quality data to enhance the European archaeomagnetic database. Additionally, and importantly, this study also investigates within and between structure variations and, the influence of anisotropy and cooling rate corrections. Eighty-six oriented samples were taken from five kilns for full geomagnetic vector (directions and intensity) determination. Additionally, cores from 39 amphorae found at the site were drilled for archaeointensity analysis. The site is archaeologically dated as being between 2nd century BC and 1st century AD, and the amphorae as being 1st century BC. A full suite of rock magnetic experiments were carried out which indicate the samples' suitability for archaeointensity experiments. The classical Thellier method with correction for anisotropy of thermal remanence (TRM) was used to determine the direction of the characteristic remanence and the archaeointensity. Differences between fast and slow cooling during remanence acquisition were investigated and a cooling rate correction applied to the archaeointensity estimates. After correction for anisotropy of TRM, the scatter about the kiln (amphorae) mean value is reduced and the scatter between kilns is also reduced for both directions and archaeointensity, demonstrating the necessity of carrying out the anisotropy of TRM correction for these samples. Application of the cooling rate correction results in a decrease in archaeointensity as expected on theoretical grounds for single domain grains. The correction, whilst not reducing scatter in the mean archaeointensity results, does result in a reduction in the scatter found between the kilns. The directional results are compared to the French, and a preliminary Italian, secular variation (SV) curve and suggest that the kilns may be towards the older limit of the archaeologically given age however the master curves are not well constrained in this time interval. Instead, the five new directional data should be used to help constrain future curves. The Albinia archaeointensity data are consistent with the broad trends seen in the limited high quality Western European and Mesopotamian data sets and with the newly constructed archaeointensity SV curve for Greece. Similar to other studies whilst the archaeointensity results for each kiln (the amphorae) are well constrained (4-7 per cent scatter about the mean) variations are seen between the kilns (mean archaeointensity 62-70 μT). This further supports the suggestion that it is necessary to obtain a number of archaeointensity data for each time http://gji.oxfordjournals.org/ Downloaded from 472 M. J. Hill et al.

Physics of the Earth and Planetary Interiors, 2000

Twenty new paleointensity determinations have been obtained from archaeomagnetic sites from Franc... more Twenty new paleointensity determinations have been obtained from archaeomagnetic sites from France. Time intervals investigated range from 65 to 380 AD and from 1370 to 1700 AD. Two hundred forty-two samples of tiles and bricks were treated with the classical Thellier method for paleointensity determination. Rock magnetic studies identify magnetite, substituted maghemite and hematite as the main magnetic minerals. As

Global geomagnetic models using archaeomagnetic data can offer important insights in to geomagnet... more Global geomagnetic models using archaeomagnetic data can offer important insights in to geomagnetic field evolution and core mantle boundary processes. However, in order to provide a complete field description it is necessary to have many data giving good spatial and temporal coverage. Due mainly to experimental difficulties there are many more directional data than intensity data, and whilst data coverage is reasonable for some locations it is recognised that many more high quality data are still needed. Here we present results from two Italian sites: a Roman Amphorae workshop (dated to be between 200 BC and 100 AD), Albinia, Tuscany, and from a 7th Century BC site at Incoronata, Pisticii, Basilicata. The classical Thellier technique was used with anisotropy of thermal remanence and cooling rate corrections. At Albinia, samples were taken from five kilns and from the base of 39 amphorae. The mean archaeointensity per kiln / the amphorae range from 62 to 70 microT. This variation may reflect them being of differing ages however it could also reflect the limitations of the experimental protocol and/or samples. Thus it is desirable that a number of archaeointensity data per time interval are obtained in order to reliably determine the past variations of the geomagnetic field. At Incoronata samples were drilled from 39 bricks. The mean archaeointensity of 85 microT obtained for the older Incoronata bricks is consistent with the increase in field intensity seen going back through the first millennia BC in other regions such as Mesopotamia.

Archaeometry, 1987

Magnetic and other measurements are reported for the Guehenno II Gallo-Roman hoard (56-France) wh... more Magnetic and other measurements are reported for the Guehenno II Gallo-Roman hoard (56-France) which, amongst several thousand Tetricus antoniniani, contains 275 coins struck with the same dies. The orientation of the remanent magnetization is systematically directed outwards from the obverse confirming the identity of the anvil die with the obverse. The magnetization vector is statistically distributed around the vertical axis giving no indication of the geomagnetic inclination at the time of striking. Consequently ancient struck coins cannot be used for dating. The origin of the remanent magnetization was also investigated.

Geophysical Journal International, 2005

The German archaeomagnetic data set was supplemented with 35 new directions from German sites mai... more The German archaeomagnetic data set was supplemented with 35 new directions from German sites mainly dating from the past 3000 yr. Together with archaeomagnetic data from the neighbouring countries of Germany a database of 166 reliable archaeomagnetic directions has been compiled for the reference area, which is defined by a 500-km-radius circle around Göttingen. The retrieved directions come from well-dated archaeological structures and about 40 per cent of the dating relay on natural science methods such as radiocarbon, thermoluminescence, dendrochronology dating or historical documents. From this data set a secular variation (SV) reference curve has been calculated using a bivariate algorithm, which fits a natural cubic spline based on roughness penalty to declination, inclination and time, simultaneously. The error tube surrounding this curve was obtained from Bayesian modelling of the experimental errors, which can also take stratigraphic information into account. The obtained SV reference curve for the past 2500 yr is similar to that from France, but also significant differences are seen. Comparison of the curves does not show a simple westward drift of the SV pattern. The German reference curve allows archaeomagnetic dating in the reference area and extends this dating technique to sites situated in middle Europe.

Variations of the Earth magnetic field during the first millennium B.C. in Western Europe remain ... more Variations of the Earth magnetic field during the first millennium B.C. in Western Europe remain not very well constrained, especially archeointensity. Three salt-kilns (MOA, MOB and MOC) sampled in Moyenvic (Lorraine, Eastern France) have been studied to provide new reference data. Each kiln has been dated by radiocarbon in the First Iron Age or Hallstatt period (between VIII and Vth Century BC). Paleomagnetic experiments have been carried out both in laboratories of Leoben (Austria) and Rennes (France). Rock magnetic experiments and hysteresis results suggest the predominance of pseudo single domain (PSD) grains close Ti-poor magnetite. Archeomagnetic directions have been obtained by thermal and alternating field demagnetizations. High values of mean inclination and declination are observed (declination between 19° to 31° and inclination close to 70°). Classical Thellier-Thellier experiments were first conducted on 51 samples with a laboratory field almost parallel to the direction of the characteristic remanent magnetization (ChRM). Even if pTRM checks are positive, the very large dispersion observed within the paleointensity values determined has suggested that some artefacts have not been well recognized. In a second step, Thellier experiments have been conducted on 36 sister specimens with the laboratory field quasi-perpendicular to ChRM. In these cases, mineralogical evolutions during heating and chemical remanent magnetization acquisitions have clearly been recognized. For the whole sample suite the success rate of the palaeointensity determinations is very low with 80% of the samples rejected. Nevertheless, reliable mean archeointensities have been obtained for two of the three kilns (MOA, 77.0 ± 15.2 µT and MOB, 89.2 ± 7.0 µT at the latitude of Paris). The high field strength and the archeomagnetic directions determined, provide further evidence for important changes of the Earth magnetic field in Europe during the first half of the first millennium BC. Large variations of the geomagnetic field during First Iron Age indicate that archeomagnetism should be very efficient to date archaeological structures of this period.

Geochemistry Geophysics Geosystems, 2006

1] A first secular variation (SV) curve for the Iberian Peninsula was computed by hierarchical Ba... more 1] A first secular variation (SV) curve for the Iberian Peninsula was computed by hierarchical Bayesian method using a total of 134 archaeomagnetic directions with ages ranging from À775 to 1959 A.D. A general agreement is observed between the Iberian curve and the French and German SV curves, although some interesting differences were found, such as the occurrence of lower inclinations between the 11th and 14th centuries in the Iberian curve. The analysis of these three reference curves indicates that SV in western Europe is characterized by three major directional changes at À125, 200, and 1350 A.D. It is suggested that these cusps are regional features of the geomagnetic field. The Iberian curve has been compared with the predictions of the Jackson, CALSK7K.2, and Hongre global models. Despite large differences recognized between these models, even for the dipolar terms, they predict reasonably well the Iberian archaeomagnetic SV.

Journal of Geophysical Research, 2003

Citation: Schnepp, E., R. Pucher, C. Goedicke, A. Manzano, U. Müller, and P. Lanos, Paleomagnetic... more Citation: Schnepp, E., R. Pucher, C. Goedicke, A. Manzano, U. Müller, and P. Lanos, Paleomagnetic directions and thermoluminescence dating from a bread oven-floor sequence in Lübeck (Germany): A record of 450 years of geomagnetic secular variation,

Geophysical Journal International, 2011

Variations of the Earth's magnetic field during the first millennium BC in western Europe remain ... more Variations of the Earth's magnetic field during the first millennium BC in western Europe remain poorly constrained, especially archaeointensity changes. Three salt-kilns (MOA, MOB and MOC) sampled in Moyenvic (Lorraine, eastern France) have been studied to provide new reference data. Each kiln has been dated by radiocarbon to originate from the Early Iron Age or Hallstatt period (between VIII and Vth Century BC). Rock magnetic experiments and hysteresis results suggest the predominance of pseudo-single domain (PSD) Ti-poor magnetite. Archaeomagnetic directions obtained by thermal and alternating field demagnetizations have high mean inclination (close to 70°) and declination (between 19 and 31°). A first set of classical Thellier-Thellier experiments was conducted on 46 samples with a laboratory field almost parallel to the direction of the characteristic remanent magnetization (ChRM). Only 24 of these specimens present a linear NRM-TRM plot. For other specimens, NRM-TRM plots are concave-up with positive pTRM checks. The very large dispersion observed between the determined palaeointensity values suggests some artefacts have not been fully recognized. A second set of Thellier experiments was conducted on 34 sister specimens with the laboratory field applied quasi-perpendicular to the ChRM. In these cases, mineralogical evolutions during heating and chemical remanent magnetization acquisitions have been clearly recognized, despite positive pTRM checks. The concave-up shapes of NRM-TRM plots appear mainly due to mineralogical alteration rather than to the presence of PSD-MD grains. For the entire set of samples the success rate of the palaeointensity determinations is very low with 80 per cent of the samples rejected. Nevertheless, reliable mean archaeointensities have been obtained for two of the three kilns (MOA, 80.1 ± 14.5 μT and MOB, 86.6 ± 6.9 μT at the latitude of Paris). The high field strength and the archaeomagnetic directions determined, combined with previous published data, provide further evidence for important changes of the Earth magnetic field in Europe during the first half of the first millennium BC. These large variations of the geomagnetic field during the Iron Ages indicate that archaeomagnetism is highly suitable for dating of structures from this period.

Geophysical Journal International, 2007

An intensive archaeomagnetic investigation of an Italian Roman amphorae workshop has been carried... more An intensive archaeomagnetic investigation of an Italian Roman amphorae workshop has been carried out in order to produce high quality data to enhance the European archaeomagnetic database. Additionally, and importantly, this study also investigates within and between structure variations and, the influence of anisotropy and cooling rate corrections. Eighty-six oriented samples were taken from five kilns for full geomagnetic vector (directions and intensity) determination. Additionally, cores from 39 amphorae found at the site were drilled for archaeointensity analysis. The site is archaeologically dated as being between 2nd century BC and 1st century AD, and the amphorae as being 1st century BC. A full suite of rock magnetic experiments were carried out which indicate the samples' suitability for archaeointensity experiments. The classical Thellier method with correction for anisotropy of thermal remanence (TRM) was used to determine the direction of the characteristic remanence and the archaeointensity. Differences between fast and slow cooling during remanence acquisition were investigated and a cooling rate correction applied to the archaeointensity estimates. After correction for anisotropy of TRM, the scatter about the kiln (amphorae) mean value is reduced and the scatter between kilns is also reduced for both directions and archaeointensity, demonstrating the necessity of carrying out the anisotropy of TRM correction for these samples. Application of the cooling rate correction results in a decrease in archaeointensity as expected on theoretical grounds for single domain grains. The correction, whilst not reducing scatter in the mean archaeointensity results, does result in a reduction in the scatter found between the kilns. The directional results are compared to the French, and a preliminary Italian, secular variation (SV) curve and suggest that the kilns may be towards the older limit of the archaeologically given age however the master curves are not well constrained in this time interval. Instead, the five new directional data should be used to help constrain future curves. The Albinia archaeointensity data are consistent with the broad trends seen in the limited high quality Western European and Mesopotamian data sets and with the newly constructed archaeointensity SV curve for Greece. Similar to other studies whilst the archaeointensity results for each kiln (the amphorae) are well constrained (4-7 per cent scatter about the mean) variations are seen between the kilns (mean archaeointensity 62-70 μT). This further supports the suggestion that it is necessary to obtain a number of archaeointensity data for each time interval in order to reliably record variations of the Earth's magnetic field from archaeological material. The archaeointensity result for the set of amphorae which has the better constrained age falls within the archaeointensity values from the kilns. Combining the results from the five kilns and the amphorae gives a mean archaeointensity of 64 +/- 3 μT at Albinia (69 +/- 3 μT relocated to Paris) during 200 BC-100 AD.

Geophysical Journal International, 2006

The construction of a secular variation (SV) reference curve for a region for which little or no ... more The construction of a secular variation (SV) reference curve for a region for which little or no archaeomagnetic directions are available is presented here. A SV curve is illustrated for Austria, centred on Radstadt (47.38°N, 13.45°E) and based on data from sites in other countries less than 500 km away. The published data were selected on site characteristics of N≥ 3 and k≥ 50, and dated within 400 yr. This yielded 170 directions from which a SV curve was derived using Bayesian techniques. The obtained reference curve represents the past 2300 yr. New data, mainly from Austria, substantiate this curve and confirm the validity of the techniques employed which can, therefore, be applied for similar situations. Another test has been made using the German reference curve for dating the Austrian archaeological sites, here a systematic shift to older times in the order 30–110 yr occurs.

Directional archaeomagnetic reference curves have been published for Austria and Germany some yea... more Directional archaeomagnetic reference curves have been published for Austria and Germany some years ago. Recent determination of new archaeomagnetic directions was mainly concentrated on time intervals with only sparse data. About 60 new directions have been obtained and further 25 new archaeointensities have been determined. The past 3500 years are now covered with one or two intensity values per century, all associated with direction. The data base for direction is much larger and in the order of ten directions per century. Examination of velocity and curvature of the archaeomagnetic calibration curves yielded four major directional changes (sometimes called 'archaeomagnetic jerks'), which are found in Central Europe and all over Europe at the same time. A fifth 'archaeomagnetic jerk' occurring in the 8th century BC is also well documented in the new data. Using the updated archaeomagnetic data set from this study, the hypothesis of correlation between 'archaeomagnetic jerks' and high intensity has been tested. It is not supported by the new results, especially not by the full vector data. However, rapid variations in direction as well as in archaeointensity on centennial timescale are observed during the past 3500 years. In particular, two very pronounced intensity highs occur in the 5th century BC and the 8th century AD. In both cases, archaeointensity increased with a rate of more than 10 µT per 100 yrs during the preceding centuries.

Journal of Geophysical Research, 2003

Citation: Schnepp, E., R. Pucher, C. Goedicke, A. Manzano, U. Müller, and P. Lanos, Paleomagnetic... more Citation: Schnepp, E., R. Pucher, C. Goedicke, A. Manzano, U. Müller, and P. Lanos, Paleomagnetic directions and thermoluminescence dating from a bread oven-floor sequence in Lübeck (Germany): A record of 450 years of geomagnetic secular variation,