Search

The in-phase response collected by portable loop–loop electromagnetic induction (EMI) sensors operating at low and moderate induction numbers (≤1) is typically used for sensing the magnetic permeability (or susceptibility) of the subsurface. This is due to the fact that the in-phase response contains a small induction fraction and a preponderant induced magnetization fraction. The magnetization fraction follows the magneto-static equations similarly to the magnetic method but with an active magnetic source. The use of an active source offers the possibility to collect data with several loop–loop configurations, which illuminate the subsurface with different sensitivity patterns. Such multiconfiguration soundings thereby allows the imaging of subsurface magnetic permeability/susceptibility variations through an inversion procedure. This method is not affected by the remnant magnetization and theoretically overcomes the classical depth ambiguity generally encountered with passive geomagnetic data. To invert multiconfiguration in-phase data sets, we propose a novel methodology based on a full-grid 3-D multichannel deconvolution (MCD) procedure. This method allows us to invert large data sets (e.g. consisting of more than a hundred thousand of data points) for a dense voxel-based 3-D model of magnetic susceptibility subject to smoothness constraints. In this study, we first present and discuss synthetic examples of our imaging procedure, which aim at simulating realistic conditions. Finally, we demonstrate the applicability of our method to field data collected across an archaeological site in Auvergne (France) to image the foundations of a Gallo-Roman villa built with basalt rock material. Our synthetic and field data examples demonstrate the potential of the proposed inversion procedure offering new and complementary ways to interpret data sets collected with modern EMI instruments. [ABSTRACT FROM AUTHOR]

The IGEAN (Innovative Geophysical Approaches for the study of Early Agricultural villages of Neolithic) Thessaly project focused on Early and Neolithic settlements in Thessaly, Central Greece. The aim of the project was to highlight in an extensive way differences in settlement layouts while investigating commonalities as a way to understand Neolithic use of space. To accomplish this, a suite of geophysical prospection techniques (geomagnetic, electromagnetic induction, and Ground Penetrating Radar (GPR)), aerial platforms (historic aerial imagery and Remotely Piloted Aerial Systems (RPAS)) as well as very high resolution spaceborne sensors were integrated to acquire comprehensive pictures of settlements. Results of the IGEAN project provide archaeological information on the dynamic character of enclosures, the structure of architectural features and open spaces within sites as an indication of economic or communal spaces. At the same time, they demonstrated the importance of employing a suite of different geophysical techniques to reveal different aspects of the hindered prehistoric settlements that could not be highlighted with a single geophysical approach. [ABSTRACT FROM AUTHOR]

Measuring magnetic viscosity significantly improves the information brought by the magnetic susceptibility about the history of soils. In the field its mapping can be achieved by TDEM measurement. Here we study the applicability of multi-frequency FDEM viscosity measurement in the low frequency range using a commercial EMI instrument. The dependence of the in-phase and quadrature out-of-phase components of the ratio of secondary magnetic field to primary magnetic field, electrical conductivity, magnetic susceptibility and magnetic viscosity is first described. The procedure allowing the determination of the three apparent properties is then proposed. It delivers first the conductivity using the differences between the quadrature responses at two different frequencies. Then, after removing the conductivity effects both in the in-phase and quadrature components, it provides the values of the magnetic susceptibility and viscosity. This procedure is tested on 1D and 3D synthetic cases to assess any arising uncertainty. The application of the method is attested in two archaeological case histories in Thessaly in conductive and magnetic soil contexts. The apparent magnetic viscosity maps are significantly different from magnetic susceptibility and conductivity maps thus bringing new information into the game. [ABSTRACT FROM AUTHOR]

ABSTRACT Statute laws concerning preventative archaeology adopted in France in 2001 for threatened sites required development of evaluation techniques. The common methodology used during the past 10 years has been extensive excavation. This method delivers a direct record of the discovered archaeological features and of their distribution. However, the success of visual observation can be variable, depending on geological context and the feasibility of envisaging the entire archaeological settlement from the part that is observed. We report here a case study from an early Middle Age settlement located on a floodplain. It was partially excavated and the alluvial context makes the features difficult to recognize for archaeologists. We show how the geophysical survey complemented the archaeological survey and allowed the detection of previously unrecognized features. In a second step, we compare the results of surveys with magnetic and electromagnetic methods on a topsoil stripped area and the neighbouring surface. From this analysis we conclude that a significant part of the unrecognized features discovered were present above the level of stripping. This example underlines that the practice of topsoil stripping has to be reconsidered, and should be integrated with geophysical survey to limit the potential loss of archaeological information. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Two peptide based dendrimers containing l-aspartic acid as the branching unit and succinic acid/terephthalic acid as the core unit were synthesized, characterized, and studied. These dendritic peptides form gels in various organic solvents including n-hexanol, benzene, toluene, chlorobenzene, 1,2-dichlorobenzene, o-xylene, tetralin, and nitrobenzene. Gels were characterized by freeze fracture transmission electron microscopic (FF-TEM), field emission scanning electron microscopic (SEM), transmission electron microscopic (TEM), wide angle X-ray powder diffraction (WAXPD), and variable temperature FTIR (VT-FTIR) studies. The VT-FTIR study indicates that amides and ester groups are involved in intermolecular hydrogen bonding in the gel state. Two transitions have been observed for both the dendrimer gels upon heating: the first one corresponds to the gel to sol transition and corresponds to the breaking of hydrogen bonds between esters and amides; the second one corresponds to the breaking of hydrogen bonds between amides. In the case of dendrimer 1 structural reorganization occurs in the sol state after the first transition, which is absent in the dendrimer 2 in the sol state. FF-TEM observations showed that both dendritic peptides form a platelet structure in gel state. SEM images of these dried gels indicate different geometry in different solvents in their self-assembled gel state. [Copyright &y& Elsevier]

Diamides containing alkyne and azido were self-assembled into nanotubes and were reacted under their self-assembled state with small molecules by "click chemistry"; the resulting compounds remain self-assembled into new nanotubes that cannot be formed by simple self-assembly of the constituting molecules. [ABSTRACT FROM AUTHOR]

• Multi-geophysical properties interpretation of a multi-device EMI dataset. • Joint 1D inversion of four electromagnetic properties. • Spatial and vertical characterization of hydromorphic soils in volcanic context. We used two different loop-loop electromagnetic induction (EMI) devices to determine the 3D geometry and morphology of the pedo-sedimentary filling and underlying basaltic bedrock of a former wetland in a volcanic soil area, the Lac du Puy depression (Auvergne, France). Electrical conductivity (or resistivity) is usually sufficient for environmental and soil science applications, but the local volcanic context of the survey area results in high values of magnetic susceptibility and possible electrical polarization effects. Therefore we investigated the roles of the four properties: electrical conductivity, magnetic susceptibility, magnetic viscosity and dielectric permittivity. We created models using these four properties for the two coil configurations of each device in order to assess the degree to which each of the properties contributed to the recorded electromagnetic signal. The results show that electrical conductivity controls the quadrature component of the secondary field response but that it can be affected by high values of magnetic viscosity, while magnetic susceptibility controls the in-phase component. Moreover, the low frequencies imply a limited contribution of dielectric permittivity to the in-phase component, except in the cases of higher permittivity or frequency values or greater inter-coil separation. Based on these observations, we propose a way to map the apparent properties from field measurements. We then carried out a 1D inversion, first by considering the electrical conductivity alone and secondly by taking all the electromagnetic properties into account. The results show that there is a marked contrast in the complex magnetic susceptibility between the sedimentary in-fill and the border of the Lac de Puy depression, (stronger than for the electrical conductivity), and that permittivity is unlikely to have a significant influence. The shape and nature of the sedimentary in-fill was thus considerably refined by the second inversion results based on the three other properties. These data, combined with litho-stratigraphic observations from a previous study, allowed the lateral continuity and geometry of the in-fill to be assessed across the whole basin. Results are also consistent with previous interpretations of the depression as a pseudo-sinkhole, a relatively common morphology in volcanic plateaus. Analysis of the magnetic properties also made it possible to characterize the spatial variation of some key features related to hydromorphic processes, such as clayey granularity and the development of iron oxides/hydroxides. This opens up the possibility for using new methods for rapid spatial and pedological characterization of hydromorphic soils and palaeosoils. [ABSTRACT FROM AUTHOR]

The in-phase response collected by portable loop-loop electromagnetic induction (EMI)sensors operating at low and moderate induction numbers is typically used for sensing themagnetic permeability (or susceptibility) of the subsurface because it contains a rather small"induction" fraction depending on the electrical conductivity. The magnetization fraction ofthe in-phase signal, which is sensitive to the surrounding magnetic permeability, follows themagneto-static equations similarly to the magnetic method but with an active magneticsource. The use of an active source offers the possibility to collect data with several loop-loopconfigurations, which illuminate the subsurface with different sensitivity patterns (Klose etal., 2018). Such multi-configuration soundings thereby open the door to the imaging ofsubsurface magnetic permeability/susceptibility variations by an inversion procedure.Such an imaging procedure, which focuses on the induced magnetization effect,overcomes the classical depth ambiguity generally encountered with passive geomagneticdata.To invert multi-configuration in-phase data sets, we apply the 3D full-grid multi-channeldeconvolution (MCD) procedure presented in Guillemoteau et al. (2017). This fast imagingalgorithm allows us to invert large in-phase data sets (e.g., consisting of more thana hundred thousand data points) for a dense voxel-based 3D model of magneticpermeability subject to smoothness constraints. In this study, we first present anddiscuss synthetic examples of our inversion strategy, which aim at simulating realisticconditions. Finally, we demonstrate the applicability of our method to field data collectedacross an archaeological site in Auvergne (France) to image the foundations of agallo-roman villa consisting of basaltic rock material. Our synthetic and field dataexamples demonstrate the potential of the proposed inversion procedure offeringnew and complementary ways to interpret data sets collected with modern EMIinstruments.References:Guillemoteau, J., Christensen, N. B., Jacobsen, B. H., Tronicke, J. (2017): Fast 3Dmulti-channel deconvolution of electromagnetic induction loop-loop apparent conductivitydata sets acquired at low induction numbers. Geophysics, 82(6), E357-E369.Klose, T., Guillemoteau, J., Simon, F.-X., Tronicke, J. (2018): Toward subsurface magneticpermeability imaging with electromagnetic induction sensors: Sensitivity computation andreconstruction of measured data. Geophysics, 83, E335-E345 [ABSTRACT FROM AUTHOR]

ALS-derived raster visualization techniques have become common in recent years, opening up new possibilities for subtle landform detection in earth sciences and archaeology, but they have also introduced confusion for users. As a consequence, the choice between these visualization techniques is still mostly supported by empirical knowledge. Some attempts have been made to compare these techniques, but there is still a lack of analytical data. This work proposes a new method, based on gradient modelling and spatial statistics, to analytically assess the efficacy of these visualization techniques. A selected panel of outstanding visualization techniques was assessed first by a classic non-analytical approach, and secondly by the proposed new analytical approach. The comparison of results showed that the latter provided more detailed and objective data, not always consistent with previous empirical knowledge. These data allowed us to characterize with precision the terrain for which each visualization technique performs best. A combination of visualization techniques based on DEM manipulation (Slope and Local Relief Model) appeared to be the best choice for normal terrain morphometry, occasionally supported by illumination techniques such as Sky-View Factor or Negative Openness as a function of terrain characteristics. [ABSTRACT FROM AUTHOR]

Abstract: Electromagnetic induction (EMI) is one of the geophysical techniques widely used in soil studies, the slingram devices being held horizontally over the soil surface, i.e. with the coils located at the same height above the ground surface. Our study aims assessing the abilities of slingram devices when held vertically. 1D and 3D modelling have been achieved in order to compare the theoretical responses of vertical devices to the horizontal ones. Some comparative surveys were also undertaken in archaeological contexts to confirm the reliability of theoretical conclusions. Both approaches show that vertical slingram devices are suitable for survey and can constitute an alternative to the usual horizontal orientation. We give a table in Appendix A which contains the calibration coefficient allowing transforming of the values given by some of commercially available devices which would be advantageous to use in vertical orientation [Copyright &y& Elsevier]

Abstract This work is the first geomorphological analysis of La Narse de la Sauvetat , a hydromorphic basin located in the southern Limagne plain (French Massif Central) which had never been studied despite its great palaeoenvironmental interest. We explore the potential of its sedimentary archives to provide valuable data on Holocene geomorphic dynamics and their sensitivity to local and regional hydro-climatic changes. In order to characterize the nature and the morphostratigraphic and pedosedimentary evolution of the basin, we used an integrative approach involving geomorphological mapping, hand auger stratigraphic cross-sections, topographic analysis based on LiDAR data and stereophotogrammetric reconstruction, geophysical prospection and radiocarbon dating. Results revealed a palaeotopography fossilized under 6 m of sedimentary infilling, with a clear shift from fluvial to hydromorphic conditions circa 2800 cal BCE, separated by a level with colluvial and lacustrine features. A detailed analysis of the eastern border of the basin also suggests the existence of a former open valley in place of the current closed depression, now locked in by a topographic threshold forming a dam. The sedimentary aggradation of the basin started with an alluvial phase during the Upper Pleistocene and probably continued into the Middle and Late Holocene, consistently with regional alluvial dynamics. In the early Subboreal, a massive landslide occurred on the western slopes of the Puy-de-Corent volcanic plateau, thereby damming the valley and forming a closed depression. This episode coincided with the mid-Holocene climatic shift and an associated phase of slope instability and increased landslides in Western Europe due to changing climatic conditions. This depression evolved into a hydromorphic basin with several high energy hydro-sedimentary episodes after 2800 cal BCE; however hydro-sedimentary conditions gradually became more stable towards the Late Holocene. Around 500 cal CE, the drainage deteriorated towards palustrine conditions and caused the formation of a marsh and its consequent evolution into a shallow lake throughout the Middle Ages. This lake was drained in the late XVIIIth Century. The long-term sedimentary record of La Narse de la Sauvetat , sensitive to climatic instability periods of the Middle Holocene, makes this landslide-dammed basin a valuable site with an important potential to further development of palaeoenvironmental and geoarchaeological studies. Graphical abstract Unlabelled Image Highlights • A palaeovalley was found under Pleistocene and Holocene alluvio-colluvial sediments. • A landslide dammed the valley in the early Subboreal, forming a short-lived lake. • The depression became hydromorphic between 2800 cal BCE and late Antiquity. • The basin was a marsh then a shallow lake during the Middle Ages. • La Narse de la Sauvetat has high potential for further palaeoenvironmental research. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the first results of the geoarchaeological study of an unusual hilltop wetland, located within the protohistoric proto‐urban site of Corent in the French Massif Central. This small depression offers an exceptionally local sedimentary record that provided valuable data on long‐term human–environment interactions, as well as proto‐urbanization of the first millennium B.C.E. Field survey revealed a major archaeological discovery: a large ensemble of 114 Iron Age storage pits excavated in clayey deposits. The geoarchaeological analysis of stratigraphic logs and cross‐sections completed by geophysical survey and radiocarbon dating allowed us to refine the chronology of these structures. Here, we suggest these structures are probably contemporary with the Hallstatt occupation of the site (600–425 B.C.E.), consistent with the emergence at Corent of a short‐lived proto‐urban environment during this period. These investigations also allowed us to characterize the main evolution phases of the basin and the diversity of human impacts from first disturbance in the Early Neolithic to its final destruction in the Roman period. These findings highlight the nonlinear nature of the socio‐environmental interactions and the definitive shift to an “anthroposystem” as a consequence of major disturbance in the first Iron Age, centuries before the development of urban settlements in the oppida period. [ABSTRACT FROM AUTHOR]

The systematic exploration of large archaeological sites in the Mediterranean has evolved considerably since the “big dig” excavations. Pedestrian field surveying and remote sensing applications, including satellite and airborne image analysis, are now practical and relatively cost-efficient methods of characterizing large and diachronically diverse landscapes on regional scales. However, the use of geophysical techniques as a means for exploring manifold archaeological contexts is still in its infancy. In this paper, we highlight the advantages of archaeological geophysics to conduct regional surveys in the Mediterranean. Through a multi-site geophysical fieldwork campaign to investigate the patterns and dynamics of ancient cities in Greece, we show how geophysics offer new opportunities for characterizing the spatial attributes and regional dynamics of urban landscapes, and, in doing so, we make an argument for its wider adoption on regional survey projects. [ABSTRACT FROM PUBLISHER]