Magnetic imaging and electrical resistivity tomography studies in a Roman military installation found in Satala archaeological site,northeastern Anatolia,Turkey

Satala is one of the last great military centers in the Roman East available for archaeological and historical investigations. This archaeological site is situated on the crossing of two singularly important routes in North-East Asia Minor. Only little archaeological fieldwork in and around Satala has so far been carried out, thus delimiting our knowledge of the site and its role within the Roman military structure of the East. In order to provide further data on the site, we carried out geophysical surveys including the application of magnetic and electrical resistivity techniques in an area north of the Sadak village. The geophysical surveys within this area (supposedly part of the Roman military camp) proceeded in two stages. The first stage saw magnetic gradiometer imaging studies being carried out on 2.1 ha, measured by a Geoscan FM-36 fluxgate gradiometer by using 0.5 × 1 m grid intervals. For the second stage a different geophysical technique was used—resistivity tomography. Resistivity data were collected using a number of combined 2D resistivity pseudosections in the eastern part of the area which contained very regular magnetic anomalies. The 3D data were obtained by the combination of all survey lines collected from 2D data sets, and thereafter the arranged data were processed by using the 3D robust inversion modified from the smoothness-constrained algorithm. Electrical resistivity tomography investigations revealed that the buried archaeological structures might be located near the surface, except for some structures found in the middle of the studied area. The archaeological structures were furthermore determined by realistic model sections and volumetric representations. Magnetic imaging and electrical resistivity tomography surveys show that the combined usage of these techniques advances the understanding of archaeological structures beneath the surface.     

Site Characterization by Geophysical Methods in The Archaeological Zone of Teotihuacan, Mexico

In the present investigation, a geophysical study was carried out in the eastern flank of the Pyramid of the Sun to define potential continuations in this direction of a tunnel discovered beneath the western main entrance of this building. This man-made structure is one of the many extraction tunnels hollowed by the ancient Teotihuacans to obtain construction materials to build their city. Total field and high-resolution vertical gradient magnetic surveys were carried out. The spectral analysis of the total magnetic field enabled us to estimate the thickness of the alluvial cover over the basaltic flow as 3·3 m. It was also found that the main contribution to the observed magnetic field comes from the pyroclastic flow that covers the area of study. The horizontal gradient filter was applied to the low-pass filtered magnetic field to enhance magnetic contacts and structural boundaries. Inferred magnetic trends were related to fracture patterns within the basalts and pyroclasts, and low gradients provided an evidence of voids or tunnels. The Euler deconvolution method was applied as an attempt to confirm the above results. Using a structural index S=0, we determined the boundaries of main magnetic contacts as well as the interface between the basaltic flow and Las Varillas tunnel. Euler depths were found to range between 3 to 6 m, which represent the mean thickness of the basaltic flow.Two parallel ground probing radar (GPR) profiles were surveyed in the NW-SE direction. One passes on top of the known location of a tunnel (Las Varillas) and a second one 10 m to the north, approximately. The tunnel's roof is well outlined at depths between 3·5 and 4 m. On the other hand, little evidences of other buried tunnels or extensions of the known one were found. The second profile depicts a more complex morphology for the pyroclastic sheet. Anomalies related to basaltic flow or eruptive centres are clearly observed. Both profiles depicted the sedimentary base at 3 m, on average. A resistivity profile was undertaken along the first GPR profile. A resistivity image was obtained, that showed the vertical and lateral distribution of the true resistivity. High resistivity values were associated with the tunnel location (Las Varillas). Its geometry could also be inferred, its top is found at about 4 m and extends 20 m in the profile direction to the west. Unfortunately, the depth to its base could not be estimated, since profile length was too short. The sediment-pyroclastic flow interface could also be delimited at a depth of 3 m.Finally, a vertical magnetic field profile taken along the same surveyed line (GPR and resistivity) was inverted applying a two-dimensional algorithm. The initial model was estimated from GPR and resistivity interpretations. A simple model of Las Varillas tunnel was computed, which reasonably well satisfied geological and geophysical considerations.     

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.     

Resistivity Tomography Imaging of the Substratum of the Bedestan Monumental Complex at Nicosia,Cyprus

In the framework of the EU–UNDP project ‘Rehabilitation of Old Nicosia’ (Cyprus, 2004–9), a high‐resolution geoelectrical survey has been performed inside the partially ruined monumental complex of St Nicholas of the English, now called the Bedestan, which was designed to become a venue space for cultural activities. The aim was to detect buried traces of a Byzantine basilica of the sixth century, on the ruins of which, according to tradition, the construction of St Nicholas was begun in the 12th century. The survey has been conducted on the floor of the monument, using a dipole–dipole electrode array along two perpendicular sets of profiles. In order to model the resistivity distribution, the probability‐based electrical resistivity tomography inversion (PERTI) method has been applied. Sets of aligned blocks with resistivity in the range 100–400 ohm·m, bounding a three‐room rectangular space, and traces of a rounded structure with mean resistivity about 150 ohm·m, appearing at one extremity of the central room, are the main resistive features recognized down to 4 m depth, within a conductive background with resistivity in the range 20–40 ohm·m. Altogether, these resistive features, showing in plan the shape of a church characterized by a central nave with an apse and two side aisles, have been interpreted as an evidence of the existence of remains of the earlier Byzantine basilica. Moreover, small volumes with resistivity in the range 10–12.6 ohm·m have been found, scattered underneath the whole surveyed area. Taking into account the PERTI results, ground‐truth has been performed in two sites, designed to become two permanent protected exposures of the archaeological findings beneath the floor of the newly restored Bedestan. At one site, excavations detected remains of masonry in correspondence of the alignment of resistive blocks at the left margin of the left side aisle of the churchlike structure. At the other site, graves, entirely filled with wet debris in an alluvial soil matrix, have, instead, been found in correspondence with the greatest conductive volume, detected outside the perimeter of the churchlike structure. Both findings have been dated back to the sixth century. Since the Bedestan case‐history is one of the first applications of the PERTI algorithm to real field data sets, its performance has been tested using the well‐known ERTLab^TM commercial software as benchmark. The comparison has shown a general consistency between the two inversions, and also confirmed the much higher computing speed, better filtering capacity and greater versatility of the PERTI algorithm, already outlined in a previous paper where only synthetic models were tested.     

Interdisciplinary Research into the Legacy of the Medieval Metropolis of Soba in a Modern Khartoum Suburb

Recent research at Soba focuses on the tangible and intangible heritage of the medieval capital of Alwa kingdom, whose remains cover approximately 275 ha. About 222 ha of this area has been built up or transformed into agricultural land in the past 30 years. An ethnographic survey was also carried out in the built-up area to understand how the residents engage with the archaeological heritage and material remains. The undeveloped area of the capital (53 ha) was the focus of interdisciplinary archaeological fieldwork conducted in 2019 and 2020. A large-scale geophysical survey, using a fluxgate gradiometer and ground-penetrating radar, was initiated in the undeveloped area, and excavation trenches were opened to verify distinctive magnetic anomalies. Along with the ethnographic and geophysical data, the study of the pottery, burials, and stratigraphic sequence (supplemented with radiocarbon dates) provides new insights into the spatial organization of the medieval capital.

     

Quantifying tomb geometries in resistivity images using watershed algorithms

Quantifying the geometries (defined here as width, height and depth of burial) of archeological structures within resistivity models produced as a result of the regularization constraints used in most inversion algorithms is difficult, especially when structures are closely spaced. Here we apply the watershed by simulated immersion method of boundary detection to smooth 2D resistivity images generated for synthetic and field data over 3D targets. The synthetic studies include a single cavity model, a model for two widely spaced cavities (spacing ? unit electrode spacing) and a model for two closely spaced cavities (spacing < unit electrode spacing). We also examine a single-cavity model where a relatively resistive overburden, common at archaeological sites in Egypt, is included. In the case of the single cavity models, the maximum error for any geometries are 18% for the model without the resistive overburden and 10% for the model where the overburden is included, whereas it increases to 24% for the widely spaced model and 40% for the closely spaced model. Despite, the higher errors in the closely spaced cavity model, application of the algorithm confirms the presence of two features, which is not ascertainable from the smooth resistivity images. Boundaries detected with the watershed algorithm are subsequently used to define a disconnect in the regularization, resulting in a markedly improved estimate of the resistivity structure (particularly for the closely spaced cavity model) in a second inversion step using the model obtained from the smoothness constraint inversion as the starting model. This revised resistivity model also results in a lower root-mean-square (rms) misfit between measured and theoretical data, and between synthetic and inverted models. We demonstrate how the method can be applied on images from the archaeological site at Qurnet Murai, Luxor City Egypt.     

The Terramare and the surrounding hydraulic structures: a geophysical survey of the Santa Rosa site at Poviglio (Bronze Age,northern Italy)

The Terramara Santa Rosa is a Middle and Late Bronze Age archaeological site located in the Po alluvial plain, northern Italy. It is constituted of two moated villages delimited by earthen ramparts. The peripheral structures of the site are sealed by fine-textured flood plain deposits and they have not been fully explored through excavation due to their large extent. Because the shape of the villages and their relation to moats and the fluvial network are of paramount importance to understanding the landscape management and the use of water resources in the Terramare civilisation, a geophysical survey was planned to extend the results of the existing archaeological excavations to the site scale. A frequency-domain electro-magnetic sounding (FDEM) and electrical resistivity imaging (ERI) covered an area of approximately 26 ha; ERI was conducted for a total length >9000 m. Despite the predominance of electrically conductive fine-textured sediments, electrical resistivity anomalies were observed and they were attributed to subtle lithological differences in the sedimentary context of the alluvial plain. The geophysical interpretation, after the calibration with the excavation data, revealed the structures of the Terramara and of the surrounding hydraulic network, which are not visible at the surface due to flood plain deposits. The Santa Rosa site was founded in a favourable geomorphological position, on the top of a crevasse splay lobe of the adjoining Po palaeo-channel, rising above the surrounding alluvial plain. The Terramara and their surroundings were delineated through an artificial modification of this pre-existing crevasse splay lobe and a well-targeted urban design, with the objective of diverting water, most likely from a palaeo-channel of the Po River, through the digging of peripheral moats used to collect water around the site and to distribute it to the surrounding fields for irrigation. The water management documented by this study in the Terramara Santa Rosa can be considered as paradigmatic for the whole Terramare civilisation, which is therefore responsible of the introduction of the irrigated agriculture into western Europe for the first time.     

A first note on the excavations at UAQ38, a new Neolithic site in the Emirate of Umm al-Quwain

At the end of 2018, the first season of excavation was carried out at the shell midden site of UAQ38. The site occupies the top of a sand dune not far from UAQ36 and UAQ2, two other recently investigated Neolithic shell middens. Several well-stratified anthropogenic levels were excavated at UAQ38, which can be dated mainly to the 5th millennium BC, although the recorded artefacts suggest a possible older date for the lowest levels. Food waste, post-holes, fireplaces, and burnt shell dumpings attest to human activities that took place at the site over a rather long period of time. Here the stratigraphic sequence will be presented, together with a first overview of the artefactual assemblage. The collected data will be concisely discussed in order to fit the site within the typology of Neolithic settlements that can be proposed for the area. UAQ38 is so far the only Neolithic site along the northeastern coast of the UAE for which stratified charcoal is available for dating.     

Integrated geophysical surveys at the archaeological site of Tindari (Sicily,Italy)

The results of geophysical survey carried out at the archaeological site of Tindari, located 70 km west-north-west of Messina (Sicily, Italy), are presented and discussed. The site is one of the most important archaeological sites, about 90 ha large, on the north-eastern side of Sicily and it was one of the last Greek settlements in Sicily. Keeping in mind the vastness of the site, according to the archaeologists an area, of about 1200 m² was selected, for a geophysical survey. Electrical resistivity tomography (ERT), including induced polarization (IP) measurements, and seismic refraction tomography were applied in the course of geophysical exploration in the area. The objective of this preliminary geophysical investigation was to verify the effectiveness of the technique for a spatial definition of the buried archaeological structures (mostly walls, columns, etc.) to determine their characteristics and to study the presence of collapsed columns within the zone of archaeological interest, in view of their application in the rest of the site, that, for obvious reasons, could not be entirely excavated in brief times. The geophysical data, visualized in 3D space, revealed a distribution of low-contrast shallow anomalies that indicate the presence of different types of buried structures in the surveyed area. Also, the probable accumulations of collapsed columns could be determined. These results confirm the hypothesis of a large northern extension of the archaeological site and provide useful information to design a more efficient excavation plan.     

Three-dimensional image of seismic refraction tomography and electrical resistivity tomography survey in the castle of Occhiolà (Sicily,Italy)

A geophysical survey was carried out at the ruins of Occhiolà Castle (Sicily, Italy), a medieval village located at the north-western part of a hill named “Terravecchia” at 491 m asl. In order to map the archaeological structures (such as walls and burrows), Electrical resistivity tomography (ERT) and seismic-refraction tomography methods were used. The resistivity variations are known to correlate quite well with the lithology, thus providing important information for identifying the buried archaeological remains. On the other hand, seismic velocity variations provide information about the geometrical features of the remains. The two geophysical methods are used in an enjoined way to better aid the interpretation and evaluate the significance and reliability of the results obtained with each single method. The electrical and seismic data are displayed in three dimensions by using the iso-resistivity and iso-velocity surfaces, respectively. This allows us to effectively define the location of the anomalies present in the single electrical and seismic sections. The results obtained in the survey highlight the presence of structures of regular shape, probably due to features of archaeological interest.     

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.     

THE DISCOVERY OF AN ANGLO‐SAXON GRUBENHAUS AT NEW BEWICK,NORTHERN UK USING ELECTRICAL SURVEYING AND PREDICTIVE DECONVOLUTION

Twin‐probe and 33‐fold multiplexed Wenner electrical resistivity surveys were carried out at New Bewick, northern UK to examine the extent of crop marks and potential Grubenhäuser (sunken‐featured buildings, sunken‐floored buildings or SFBs). The twin‐probe method was faster, but provided data with a lower spatial resolution. However, the Wenner array data was affected by characteristic ‘M’‐ or ‘W’‐shaped responses over filled excavations such as those expected to represent a Grubenhaus. The raw Wenner array data have been analysed using one‐dimensional and two‐dimensional predictive deconvolution in order to remove these artefacts. The deconvolution was carried out using an inverse matrix element method. The filtered results indicate the presence of anomalies consistent with the presence of at least six Grubenhäuser and other anomalies concurrent with the linear crop‐marks. One particular anomaly measured about 5 m by 4 m and with a pit depth of 0.6 m below 0.3 m of topsoil. This anomaly was subsequently excavated and a Grubenhaus was discovered at the site. The excavated Grubenhaus measured 4.7 m by 3.9 m with a pit depth of 0.5 m below the base of the topsoil, confirming the electrical survey results.     

Testing the efficacy and reliability of common zooarchaeological sampling strategies: a case study from the Caribbean

Zooarchaeological analysis typically involves implementing a suitable sampling strategy that provides meaningful information representative of a site under investigation. To test the efficacy of how various sampling procedures can influence interpretation of a faunal assemblage, we analyzed in full, a large assemblage of mollusks (minimum number of individuals [MNI] = 58,000+) from the late Ceramic Age (ca. AD 850–1440) site of Coconut Walk on the island of Nevis (northern Lesser Antilles, Caribbean). These remains were recovered from 25 discrete 1 × 1 m units within a larger 5 × 5 m trench that overlaid a dense midden deposit. Using statistical procedures, we compared the results of the number of identified specimens (NISP), MNI, and weight (g) of each mollusk taxon between both units and plana to determine how different sampling strategies would have affected the interpretation of mollusk composition across space and time had different sampling procedures been used. The results reveal that sampling less than 16% (4 out of 25 squares for this study) of a midden is likely to produce results outside of a 95% confidence interval for the population composition, with samples of connected squares having a higher likelihood to lie outside the interval. Discerning change between plana (or layers) may require a larger sample (i.e., 16%+). In addition, samples selected randomly or judgmentally will produce similar results, provided that proper spacing is given between units. The data in this case suggest that the midden was efficiently sampled for midden composition and key species at a rate of 16% of the surface area.     

Marine electrical resistivity tomography for shipwreck detection in very shallow water: a case study from Agropoli (Salerno,southern Italy)

A marine electric resistivity survey was carried out over a submerged beach along the Agropoli shore (Salerno, Italy) to detect buried objects of archaeological interest below the sandy seabed. We found a shipwreck, a military vessel that probably sunk during the Salerno landing operations of the allied forces in the Second World War. Resistivity data provide information on the vertical and horizontal extension of the shipwreck, which is characterized by very low calculated resistivity values (about 2–5 ohm m). Such values differ significantly from the sand and the bedrock values (5–40 ohm m). Although the presence of the shipwreck is clearly visible from geoelectric data, the joint application of electric, magnetic and multibeam bathymetric techniques reduces the ambiguities inherent in each method. As shown in the Electrical Resistivity Tomography (ERT) and confirmed by the Digital Elevation Model (obtained from the processing of bathymetric data), the shipwreck extends more than 30 m in NE–SW direction and it is about 13 m wide. The global extension of the relic is consistent with the magnetic data, that are characterized by a magnetic anomaly with an amplitude of about 1800 nT and similar dimension, as inferred from the estimation of source boundaries obtained from the computation of the analytic signal. The results of our survey encourage the use of marine geoelectrical methods for the detection of buried archaeological targets, particularly in locations where the use of seismic prospecting is not effective (e.g. very shallow water with sandy sea-bottoms). The integration of different geophysical methods allows to better define the extension, depth and thickness of buried objects, suggesting that such an approach is the most effective for underwater archaeological investigations.     

内蒙古赤峰市上机房营子遗址发掘简报

上机房营子遗址位于内蒙古赤峰市松山区初头朗乡上机房营子村北约0.5公里处的山坡上,东南距初头朗乡6公里,距赤峰市约50公里(图一)。遗址位于阴河北岸的山坡上,海拔787米。2005年夏,为配合内蒙古赤峰市三座店水利枢纽工程建设,由内蒙古文物考古研究和吉林大学边疆考古研究中心联合对上机房营子遗址进行了抢救性发掘,并对石城址利用 GPS 全球定位系统进行了测绘和局     

London-Bahrain Archaeological Expedition: 1994 and 1995 excavations at Saar, Bahrain

The long-term aim of the project is to excavate the entire central area of the Dilmun settlement. During the 1994 and 1995 seasons a further twelve buildings were excavated, most of them located along the main arteries of the settlement. A resistivity survey, followed by selective excavation, determined the size and extent of the site. A well excavated on the eastern flank provided valuable information about the level of Bahrain's aquifers in the Early Dilmun period.     

Rapid On‐site Topographic Mapping with a Handheld Laser Range Finder for a Geoarchaeological Survey in Syria

A digital elevation model and a topographic map of an archaeological site in Syria were created from a field topographic survey with a handheld laser range finder and data post‐processing using a notebook personal computer with Geographical Information System software. The method enabled rapid on‐site topographical mapping even under technical and political restrictions in the country. In an area of about 1 km², coordinates of random points on the land surface were measured, and a DEM with a 10 m interval grid was generated from the point cloud using Kriging interpolation. The DEM enables various topographic representations to be constructed, such as contour lines, cross sections and slope distribution maps. The DEM‐derived contour lines with a 1 m interval were combined with vector data showing roads and buildings to provide a topographic map. Topographic cross sections created from the DEM generally agree with sections surveyed with a hand level and a measurement tape. The obtained DEM and map are useful for preliminary field research.     

Marine Magnetic Survey of a Submerged Roman Harbour, Caesarea Maritima, Israel

A marine geophysical survey was conducted at Caesarea Maritima, Israel, to map the buried structure of King Herod's Roman harbour. Magnetic surveys reveal the presence of an extensive hydraulic concrete foundation below the ruined harbour moles. The magnetic anomaly patterns indicate that the concrete foundation was laid out in header fashion along N-S and W-E trending segments to form two large 'artificial islands'. Magnetic lows within the structure identify baffles that were infilled with sand to stabilise the concrete foundation walls.
© 2004 The Nautical Archaeology Society