Integrated near-surface geophysical survey of the Cathedral of Mallorca

This paper describes an integrated near-surface geophysical study carried out in order to obtain high-resolution images of the shallow subsurface under and around the Cathedral of Mallorca. The study was a part of a global project focused on determining the state of the building structure and on evaluating the Cathedral's dynamical behaviour (natural frequencies and vibration modes). Ground-penetrating radar (GPR) and the capacitively coupled resistivity method were used to obtain 2D images of the shallow subsurface. Refraction microtremor array measurements (ReMi) were also used to characterize the rock and soil properties and several invasive boreholes provided detailed and exact information on the stratigraphy. The information from the geophysical data was used to determine a final model of the ground, with indications of the most likely vulnerable zones.     

Ground‐Penetrating Radar Velocity Determination and Precision Estimates Using Common‐Midpoint (CMP) Collection with Hand‐Picking,Semblance Analysis and Cross‐Correlation Analysis: A Case Study and Tutorial for Archaeologists

The most crucial parameter to be determined in an archaeological ground‐penetrating radar (GPR) survey is the velocity of the subsurface material. Precision velocity estimates comprise the basis for depth estimation, topographic correction and migration, and can therefore be the difference between spurious interpretations and/or efficient GPR‐guided excavation with sound archaeological interpretation of the GPR results. Here, we examine the options available for determining the GPR velocity and for assessing the precision of velocity estimates from GPR data, using data collected at a small‐scale iron‐working site in Rhode Island, United States. In the case study, the initial velocity analysis of common‐offset GPR profile data, using the popular method of hyperbola fitting, produced some unexpectedly high subsurface signal velocity estimates, while analysis of common midpoint (CMP) GPR data yielded a more reasonable subsurface signal velocity estimate. Several reflection analysis procedures for CMP data, including hand and automated signal picking using cross‐correlation and semblance analysis, are used and discussed here in terms of efficiency of processing and yielded results. The case study demonstrates that CMP data may offer more accurate and precise velocity estimates than hyperbola fitting under certain field conditions, and that semblance analysis, though faster than hand‐picking or cross‐correlation, offers less precision.     

Ground-penetrating radar survey at the pyramid complex of Senwosret III at Dahshur,Egypt, 2008: search for the lost boat of a Pharaoh

A survey at Dahshur, Egypt, employed 3-D ground-penetrating radar (GPR) in an attempt to locate pharaonic boat burials at the pyramid complex of King Senwosret III. In AD 1894, the original excavator reported finding five or six boats; however, only four “Dahshur boats” are known in museum collections today. The suspected site of the lost boat burial(s) lay beneath the large 1894 excavation backfill pile. The steep topography of the backfill required nonstandard GPR processing methods to accurately image the subsurface of the site. Although revealing no definitive traces of any remaining boats, imaging results did indicate discernible strata associated with the original naturally deposited surface, an excavated boat pit, debris and fill associated with either its original creation or its excavation, and deeper, presently unidentified archaeological remains.     

GPR survey at Lapa do Santo archaeological site,Lagoa Santa karstic region,Minas Gerais state,Brazil

In this work we present and discuss the results of a novel and timely GPR-2D and GPR-3D survey performed at an archaeological rock shelter site, Lapa do Santo, localized in the karstic region of Lagoa Santa, central Brazil. A total of 113 ground-penetrating radar profiles were acquired with 200 MHz and 400 MHz shielded antennas aiming in identifying geological and archaeological anomalies in order to assist archaeologists in an excavation program. The GPR results indicated clear geophysical anomalies characterized by hyperbolic reflections and areas with high amplitude sub-horizontal electromagnetic waves. The anomalies observed by GPR were confirmed by the excavation of test units, allowing the identification anthropogenic features such as a fire-hearth structure and wooden artifact, and natural features, such as, tree roots and rocky bodies such as speleothems, boulders and bedrock. The results showed the efficiency of GPR method in identifying potential buried archaeological targets in cave sites within a karstic area, and they oriented to archaeological excavations, reducing costs and increasing the probability of finding archaeological targets in the initial stages of a project.     

MAPPING THE UNDISCOVERED RUINS OF POMPEII (NAPLES,ITALY) USING GROUND PENETRATING RADAR*

The ground penetrating radar (GPR) technique was tested in Pompeii, in an unexplored area where the Roman ruins are partially buried in the volcanic deposits. The method was also combined with time domain reflectometry (TDR) measurements to estimate the dielectric properties of the different volcanic units. In spite of the total thickness of the covering materials and the high signal attenuation measured in some layers, the radar was able to show a detailed image of the volcanic sediments and to locate the manmade structures hidden in the ash deposits. Moreover, the present study shows that the integrated use of GPR and TDR techniques could be successfully employed to evaluate the performance of the radar in specific terrains covering archaeological sites. Since it is unlikely that a large part of Pompeii will ever be excavated, GPR could be successfully used to produce detailed maps of the ruins still hidden in the subsurface, giving archaeologists the possibility of reconstructing the entire urban development of this unique ancient city.     

Non-invasive archaeological exploration in stratigraphically complex rural settings: an example from Ferento (Viterbo, Italy)

This paper presents the results of a ground penetrating radar (GPR) survey conducted in the rural area of the ancient city of Ferento near Viterbo (Northern Latium, Italy), where the visible ruins testify an uninterrupted history from the Etruscan to the Medieval period. The soil covering the ruins has been intensively ploughed, cultivated and used for pasture over the centuries, and is characterised by a high content of clay minerals. In this scenario, the use of GPR is particularly difficult due to both possible ‘false positive anomalies’ and strong signal attenuation. In order to reconstruct the geometrical shape and size of the geophysical anomalies related to a medieval dwelling, multi-profile GPR data were collected in two different areas, using radar equipped with 250-MHz antennas. 2D and pseudo-3D migrated maps were created and signal velocity analysis was performed to estimate the target depths. Despite the clayey-calcareous material, the results show a good signal penetration and allow a clear reconstruction of the shape of the buried ruins, confirming that the anomalies are due to medieval buildings located at a depth in agreement with what was observed on the archaeological stratigraphy. Furthermore, our study suggests that in radar data interpretation, caution should be used if the surveyed area was subjected to prolonged and intensive agriculture.     

Geophysical investigations in the service of Mount Carmel (Israel) prehistoric research

Geophysical investigations in el-Wad Cave, Mount Carmel, Israel, enabled the mapping of the surface of the bedrock and a reconstruction of the depth of the archeological deposits. Seismic refraction and Ground Penetrating Radar (GPR) provided similar results, indicating the potential value of geophysical studies when one seeks to reconstruct site features and establish future excavation strategies. Results of a GPR survey later conducted in the adjacent Jamal Cave were supported, to a high degree, by subsequent archeological excavations in the course of which Lower and Middle Paleolithic layers were unearthed.A Continuous Vertical Electrical Sounding (CVES) geoelectric survey in the (collapsed) Misliya Cave indicates a low resistivity layer at the upper, central part of the cave, suggesting that lithified archeological deposits, of ca. 4 m, are preserved at the site. This has been supported by a test excavation recently conducted at the site.More intriguing is the case of what, on the basis of the outer morphology of the cliff, seemed to be another collapsed cave just to the north of el-Wad. The CVES survey, at the bottom of the cliff and across the hypothesized cave (or chamber), shows a two-layer model, with a low resistivity (100–200 ohm-m) layer, overlying a layer of high resistivity (8000–10,000 ohm-m). A trial trench indicates that here the bedrock is covered by shallow, recent, surface material, with no archeological value.All three methods of geophysical investigation proved applicable and resulted in the successful evaluation of sites' location, depth and spatial extension, thus forming essential tools in future prehistoric research.     

Ground Penetrating Radar in the Northern Great Lakes: A Trial Survey of a Contact Period Occupation in Marquette County,Michigan

ABSTRACT

Timing, inclement weather, and limited budgets can obstruct archaeological survey efforts. Here, we ameliorate some of these with use of ground penetrating radar (GPR) at the Goose Lake Outlet #3 (GLO#3) site (20MQ140). GPR surveys to guide survey and excavation efforts in these well-drained sandy soils are limited. GPR imagery exhibited false positives; however, shovel probes, subsequent site excavation, and artifact analysis led to numerous discoveries at this protohistoric site—including glass trade beads dating to the 1630s. These discoveries solidify evidence for some of the earliest European-made trade items in the region and provide further confirmation for placement of an Indian trail and ancient travel corridor between Lake Superior and Lake Michigan. Two ¹⁴C samples obtained from moose-bone in features with trade goods fall within the expected occupation range of 1633–1668 and 1615–1647. Several anomolies, possible hearth clusters were seen on the GPR imagery; however, many features remained invisible.     

AN APPRAISAL OF THE PROBLEMS INVOLVED IN THREE-DIMENSIONAL GROUND PENETRATING RADAR IMAGING OF ARCHAEOLOGICAL FEATURES

There are a number of problems that are due to the physics involved in the ground penetrating radar (GPR) technique which result in the recorded data giving a distorted representation of the true subsurface structure. Many of these problems are reduced by the experience of the person interpreting the data. This paper is an attempt to remove some of the subjectivity from this process by considering how the distortion in the data could be reduced by applying a migration routine. The amount of data, and the time needed to collect it, place a restriction on the use of the migration process to two dimensions only and result in a compromise approach to the use of GPR. This compromise may, however, result in better integration of GPR with the other geophysical techniques available.     

莫高窟108窟内空气温湿度的变化过程及其对窟内水汽和热量来源的启示

为了对108窟内不同位置的温度、湿度和空气压力进行监测,设置了12个点的传感器。监测结果表明,窟内温度存在着显著的昼夜和长期的变化,其中上层空气的温度变化尤其明显,而下层空气的温度变化则相对较小。在夏天,窟内的上层空气温度高于下层空气的温度。窟内空气的绝对湿度受外部环境严重影响,存在近似昼夜的变化。在分布上,窟内空气湿度在上层和前部高,而在下层和后部则较小。窟内存在着净的水汽输入过程,但水汽不是从洞窟的入口进入的。同样,窟内的空气压力也存在着明显的昼夜变化过程,并受外部环境的影响而升高或下降,窟内东侧的空气压力大于西侧的空气压力。这些结果一致说明,在108窟的东侧上层存在着水汽和热量的来源。研究结果为下一步的盐害防治工作提供了思路,具有重要的科学意义和应用价值。     

The interpretation of stratified sites: A view from underground

This paper reports on an experiment designed to study the role of trampling in the vertical dispersal of artifacts in the soil, and in the mixing of originally separate sets of materials. The experiment is part of a study of the archaeological stratigraphy and patterns of site use at a large stratified cave in southern France. The experiment was designed to replicate conditions prevailing at the cave. The results strongly suggest caution in the interpretation of living floors and stratified assemblages in sandy deposits.     

游客量对炳灵寺第128窟微环境影响初步研究

通过对炳灵寺石窟第128窟连续一年的微环境监测数据分析,结合游客参观统计,探究了游客量对炳灵寺第128窟微环境的影响;其中CO₂浓度与游客量呈正相关,窟内外温差越大,其衰减越快。洞窟温度升高与游客量呈一定程度正相关,温度增量主要为正值,负值与气象条件相关,温度的衰减与温度增量及窟内外温差正相关。窟内相对湿度变化较为复杂,监测期间游客参观对相对湿度影响在-5%～10%范围内,以降低窟内相对湿度为主。研究结果表明,目前的开放模式有助于CO₂浓度衰减,可适当扩大每批次参观人数至10人左右,以应对大客流状况;注重旅游旺季特别是5月、9月下旬至10月中旬时间段洞窟内相对湿度变化的监测,做好游客管理和洞窟相对湿度控制应对措施。本研究对于炳灵寺石窟第128窟及其他相似洞窟的旅游开放管理具有一定指导意义。     

Integrated seismic tomography and ground-penetrating radar (GPR) for the high-resolution study of burial mounds (tumuli)

The study primarily aims at providing adequate imaging resolution of large and prominent targets of archaeological interest, such as pyramids and tumuli, at all depth levels. We implemented an integrated seismic tomography and georadar (STG) technique to perform high-resolution imaging and characterization of tumuli (burial mounds). We tested the proposed technique on a preserved late Bronze Age burial mound in northern Italy, for which STG succeeded in performing an accurate 3-D reconstruction of the structure and stratigraphy as proved by later archaeological excavations. We completed two transmission seismic tomography measurements, at present ground level and at 1.5 m elevation, with a 24-channel seismograph and 15° angular separation between geophones. The ground-penetrating radar (GPR) dataset encompasses 12 250 MHz radial profiles and 12 common mid point gathers for velocity analysis. Shallow layers of the mound are successfully imaged by GPR, whilst the structure of the deep central part of the tomb is reconstructed from seismic traveltime inversion. In particular, GPR images lenses and layers of sediments forming the external part of the tumulus, evidences of a looting attempt, peripheral structures associated with later exploitation of the mound (furnaces) and, in the external sector of the tumulus, the top of the deep layer of silty sediments covering the funeral chamber. Tomographic results reveal seismic velocity anomalies of potential archaeological interest at ground level, which were successively validated by archaeological excavations. The integration of GPR and tomographic datasets is an effective strategy to overcome the imaging and interpretation problems related to the structure of such peculiar funeral monuments. STG can be applied to a virtually unlimited dimensional range and requires a limited data acquisition, processing and inversion effort. The results of the study allowed the identification of the funeral chamber and a detailed imaging of layering and structural details.     

Geophysics of Lager Wick forced labour camp,Grouville, Jersey,Channel Islands

Abstract

Three seasons of fieldwork at the forced labour camp of Lager Wick, Grouville, Jersey (2014–2016) employed resistivity, ground penetrating radar (GPR) and magnetic susceptibility to investigate areas of the camp. Resistivity and magnetic susceptibility produced the most useful results, whilst the GPR survey only revealed a modern pipe. The resistivity survey was undertaken in the south-west corner of the former camp close to the entrance gate posts, whilst the magnetic susceptibility survey was undertaken over the remains of one of the barrack huts along the Gorey Road frontage which had been burnt to the ground in 1943. The resistivity survey produced some high resistance anomalies that appear to resemble a demolition layer or a surface on which the huts were constructed. Magnetic susceptibility results showed zones of burning which appear to relate to the remains of one of the burnt huts; excavation revealed a stone/brick surface.     

Integration of Complementary Archaeological Prospection Data from a Late Iron Age Settlement at Vesterager—Denmark

The complementary use of various archaeological prospection data sets offers a series of new possibilities for the investigation of prehistoric settlements. In addition to the separate interpretations of the single methods, the implementation of image fusion provides an additional tool to obtain an even higher degree of data integration during the interpretation process. To investigate some possibilities and risks of image fusion, a procedure frequently used in the medical field but rarely applied in archaeology, various algorithms inside a dedicated MATLAB toolbox TAIFU (Toolbox for Archaeological Image FUsion) were tested on the geophysical prospection data from an Iron Age settlement near Vesterager in West Jutland, Denmark. The Ludwig Boltzmann Institute for Archaeological Prospection and Virtual Archaeology had conducted large-scale, high-resolution ground-penetrating radar (GPR) and magnetometry surveys at the site in 2014, based on its discovery by the Ringkøbing Museum through aerial photos and the results of a follow-up excavation in 2009. The aim was to determine if, and to what extent, geophysical prospection together with a novel integrative interpretational approach was able to add more detailed information to an already known prehistoric settlement. Results yielded a variety of deeper insights into the separate farms (dated to around AD 400), including the discovery of several new structures and more information about the construction of the longhouses, as well as a first suggestion on how to implement image fusion into the process of analysis and archaeological interpretation of geophysical data sets.     

Determination of the influence of soil parameters and sample density on ground-penetrating radar: a case study of a Roman picket in Lower Bavaria

Ground-penetrating radar (GPR) surveys are very much influenced by the site-specific physical properties, soil parameters and the sample density of the radar pulses. According to the electromagnetic theory, the transmission and reflection of electromagnetic waves is dominated by the conductivity, dielectric permittivity and the soil moisture. Therefore, it is advisable to measure these parameters in advance of a GPR survey. Commonly, this is not possible directly with the standard common-offset GPR arrays. To overcome this problem, we adapted and applied a direct method called time-domain reflectometry to a selected case study of the Roman picket Hienheim at the Raetischer Limes in Lower Bavaria. Furthermore, we present some important results relating to the profile spacing and orientation of GPR surveys and the site-specific soil parameters. The location and the identification of the archaeological features were successful by all geophysical methods. However, the application of all these geophysical methods like magnetometry, resistivity and GPR in addition with aerial photography and Airborne Laserscanning exemplifies the advantages of an integrated survey to achieve a comprehensive result of an archaeological site. The Roman picket of Hienheim shows up differently in all results, as each one traces the archaeological remains according to a specific physical parameter. Resistivity and radar are best to resolve buried stone structures like the walls of the picket or stone-filled ditches. In contrary, magnetometry benefits of the magnetic contrast between the limestone walls and the surrounding soil.     

Ground-Penetrating Radar as a Cultural Resource Management Tool for Assessment of Eroding Shell Middens

ABSTRACT

With an increasing rate of sea level rise inherently linked to climate change, numerous coastal archaeological resources are under threat. In Maine, virtually all 2000+ coastal aboriginal shell middens are eroding. Given limited time and resources, an efficient method for making informed cultural resource management decisions is critical. Herein, we describe a six-step protocol for a minimally invasive and cost-effective ground-penetrating radar delineation of shell midden size and morphology. Benefits of the survey methodology outlined in this study include the efficiency of data collection, the non-destructive aspect of the technique, continuous records of site stratigraphy, and the lower cost as compared to large-scale excavation. Two case studies are presented to illustrate the advantages and challenges associated with this method.     

Contribution of numerical modelling of environmental parameters to the conservation of prehistoric cave paintings: the example of Lascaux Cave

Abstract

This study of Lascaux Cave consisted of simulating the evolution of changes in the levels of temperature and humidity both in the air and in the rock. By choosing different models (one-dimensional, three-dimensional, etc.), it was possible to calculate the required variables (temperature, moisture levels, speeds, etc.) at all points inside the cave, to locate zones of high water vapour concentration and to understand the nature of the airflow. The simulations described here provide the first general data on the airflow within the cave and its hygrothermic behaviour. The temperature fields result from natural convection phenomena, which are influenced by the climate outside the cave. From the point of view of air dynamics, we can observe the presence of an overall airflow that starts in the Machine Room (containing the air conditioning system installed in 1958), runs along the ground to the end of each of the branches of the cave, and returns along the cave vault to its starting point. This slow-moving phenomenon suggests the possibility of passive control of the ambient air from the Machine Room. There are localized risk areas where condensation of water vapour can occur, resulting in rapid deterioration of the limestone. Several of these areas are therefore monitored using condensation indicators placed on the cave walls or by visual observation of painted areas. The higher air speeds detected in some areas of the cave result in decay of the prehistoric paintings. The numerical modelling results, confirmed by observations and measurements in situ, should be taken into consideration when managing the conditions within the cave.     

敦煌莫高窟洞窟内外空气中微生物的对比研究

环境空气中微生物会引起文物的损坏,因此开展针对文物保护的空气微生物研究非常重要。本研究利用Anderson FA-I型空气采样器在莫高窟封闭洞窟(常年不开放)中和洞窟外(检票口)采样,研究了空气中微生物的种群动态和群落。结果表明,洞窟内的细菌数量远远高于洞窟外,而洞窟内外的真菌数量相差不大。空气中的细菌和真菌的季节性变化不明显,但夏季洞窟外环境中真菌数量最高,冬季洞窟内环境细菌数量较多。洞窟外环境空气中的细菌数量与环境空气温度、太阳辐射强度、地表温度以及风速呈显著正相关,而与空气相对湿度呈显著负相关。窟外环境空气中的真菌数量与游客数量呈显著正相关。此外,空气中的细菌主要分布在采样器的第一、三、四级中,而真菌分布以第二、三、四级为主。研究还表明,敦煌莫高窟空气中的主要真菌为枝孢属,无孢菌,青霉属,链格孢属和曲霉属的种类。     

Use of ground penetrating radar to map subsurface archaeological features in an urban area

The ground penetrating radar (GPR) technique was used to investigate the subsurface in an urban area located in Mesagne (Italy) to obtain a map of the archaeological features in the ground. The GPR survey was undertaken at selected locations placed near (about 50 m) to a necropolis dating from the Messapian to the Roman imperial age, using a GSSI Sir System 2 incorporating 200 and 500 MHz centre frequency antennae. The selected areas (A and B) were surveyed along parallel 1 m spaced profiles using a 200 MHz antenna in area A and along parallel 0.5 m spaced profiles using a 500 MHz antenna in area B. For the selected areas the processed data were visualised in 3D space not only by means of the standard time slice technique, but also by means of a recently proposed approach, namely by iso-amplitude surfaces of the complex trace amplitude. The immediacy in revealing the spatial positioning of highly reflecting bodies, such as the anomaly interpreted as an old hypogeum room in area A, makes 3D visualisation techniques very attractive in archaeological applications of GPR. Their sensitivity to the signal/noise ratio is, on the other hand, highlighted by the quite poor performance in area B, where the only reliable result provided by all the techniques was the ancient living surface reflection, whereas none of them could effectively enhance the visibility of weak hyperbola reflections noted on 2D sections and probably related to the walls located on the ancient living surface. The performance of the various techniques in these two different situations allowed insights into their main advantages and drawbacks to be gained.