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.     

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.     

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.     

Magnetic detection of ship ballast deposits and anchorage sites in King Herod's Roman harbour,Caesarea Maritima,Israel

Ballast stone deposits are a common feature of sediments in ancient harbour basins but are often overlooked as a potential source of archaeological information. Recent geophysical investigations at Caesarea Maritima in Israel have discovered a thick, laterally extensive ballast layer in the area seaward of the 1st c. BC Roman harbour. The ballast deposits were identified by low-relief mounds on the seabed with elevated magnetic intensities. Jet probing and excavation of magnetic anomalies at several locations revealed a 20–60 cm thick rubble layer containing large quantities of Late Roman and Byzantine pottery, local sedimentary boulders (kurkar sandstone, limestone cobbles) and foreign igneous and metamorphic boulders (granite, schist, volcanics; ca. 50%). The foreign boulders and pottery identify the rubble layer as ballast and ships refuse jettisoned by merchant ships outside the harbour. The strong magnetic contrast between the ballast deposits and the natural seabed sediments is attributed to the high magnetic susceptibility (>10⁻³ SI) of crystalline boulders and pottery materials within the ballast rubble.     

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.

     

Cesium magnetometer surveys at a Pithouse Site near Silver City,New Mexico

The La Gila Encantada Site is located on an isolated ridge top north of Silver City, New Mexico in an area defined culturally as the Mimbres Mogollon region. The 180 m × 80 m (14400 m²) sized site was originally recorded as a dense scatter of ceramics, lithics, and ground stone along with a number of surface depressions that appear to represent pithouses. Cesium magnetometer surveys were conducted to identify hearths, pithouse boundaries, and activity areas outside of pithouses in support of archaeological investigations, and to test this instrument's ability to image these features. This paper presents a characterization of the magnetic signature of a pithouse as a magnetic high in the center caused by the central hearth, low magnetic variability along the floor of the house, and then increased magnetic variability at the pithouse boundary. This characterization was successfully confirmed for three pithouses using cesium magnetometery and archaeological excavation.     

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.     

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.     

3D modelling of magnetic data from an archaeological site in north-western Tlaxcala state,Mexico

In Archaeology, geophysical methods had been applied usually in a qualitative form, limited only to the use of filters that enhance the data display. The main objective in this work is the implementation of a modelling technique that allows us to reconstruct the geometry of buried bodies and the determination of their depths. This is done by means of the estimation of the magnetic moments of archaeological objects using a three-dimensional mesh of individual magnetic dipoles using the least squares method and the singular value decomposition of a weighted matrix to solve the linear problem. The distribution and shape of the underlying archaeological remains can be inferred. This methodology was applied to an archaeological site called Los Teteles de Ocotitla, in the state of Tlaxcala, Mexico. A high-resolution magnetic prospection was carried out in three selected areas (terraces). The most important total field anomalies found on each area were inverted, obtaining results that were corroborated by archaeological excavations. This investigation demonstrates the potential of quantitative geophysical methods for the characterization of archaeological structures, in extension and in depth.     

Joint geophysical measurements to investigate the Rossano of Vaglio archaeological site (Basilicata Region,Southern Italy)

A high resolution geophysical survey was carried out in the archaeological site of Rossano di Vaglio (Basilicata Region, Southern Italy), where an important ancient sanctuary is located. It was built during the IV century B.C. and devoted to the goddess Mephitis. The sanctuary rises in an area affected by a multiple and retrogressive rototraslational landslide, historically and presently subject to reactivation. The main objective of this work was the identification of buried structures of archaeological interest in an area designated by the Archaeological Superintendence of the Basilicata Region. The study was performed by means of the use of high resolution geophysical surveys. In particular, we made use of the joint application of three highly sensitive and non-invasive geophysical techniques, namely the Geoelectrical, the Magnetic and the Ground Probing Radar (GPR) methodologies. In such a way, we obtained two important results: first, we provided the archaeologists with information about the limits of the areas to be excavated; second, we could verify in real time the reliability of the geophysical results. The experimental results showed four main magnetic anomalies in the area of study, in agreement with the GPR results obtained for the same target. Finally, a partial excavation test of the investigated area revealed a buried building structure, located in correspondence of an anomaly identified by means of the geophysical prospecting.     

Integrated geophysical surveys for the subsurface mapping of buried structures under and surrounding of the Agios Voukolos Church in İzmir,Turkey

This work presents the results of the integrated usage of geophysics in the Agios Voukolos Church, one of the unique Orthodox constructions in ?zmir. The surveys had two main objectives: to define subsurface characteristics inside and around the church and search for possible structural damage such as cracks and fissures, that may exist in the subfloor of the church. Magnetic gradiometry, ground penetrating radar and electrical resistivity tomography were used in the investigations; this study is the first indoor application of magnetic gradiometry. The studies revealed that several suspicious relics and crypts might have existed under the floor of the church. In addition, investigations of the courtyard area indicated potential buried structures under the settling area of the church. This study demonstrates the importance of the integrated usage of non-destructive geophysical techniques in searching for possible hidden subsurface structures in standing historical buildings. In addition, magnetic gradiometry might be useful in indoor studies, assuming that there are no important magnetic sources near the site.     

Multi-resolution morpho-bathymetric survey results at the Pozzuoli–Baia underwater archaeological site (Naples,Italy)

Here we show the results of two morpho-bathymetric surveys carried out on the underwater archaeological area of the Pozzuoli Bay (Naples, Italy). Such area is enclosed in the Campi Flegrei active volcanic complex, where bradyseism and recent volcanic activity strongly influenced the coastline shape over the last 2 Ka. The Digital Elevation Model (DTM) of the seafloor allowed to draw the main archaeological features of the Bay, that also include the military complex of Portus Iulius and the ancient thermal and villa complex of Baianus Lacus. The extraction of archaeological features from DTM was achieved thanks to the use of a GIS-derived tool based on the profile curvature algorithm. Thus, the Villa dei Pisoni (1st Century B.C.) and the thermal complex of Secca delle Fumose were investigated by using ultra-high resolution DTMs, that show the presence of Roman pilae for the protection of coastal buildings and also the inner planimetry of the Villa dei Pisoni complex. The observation of coastal engineering structures give also the opportunity to formulate some hypothesis on the evolution of morphology and of the sedimentary pattern of the area, while depth of archaeological remains allowed a rough computation of the rate of subsidence, resulted to be 2.55 (±0.5) mm/y for the Eastern sector (Pozzuoli) and 2.90 (±0.5) mm/y for the western (Baia).     

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.     

Electric and magnetic tomographic approach for the geophysical investigation of an unexplored area in the archaeological site of Pompeii (Southern Italy)

The joint application of electric and magnetic techniques for near-surface exploration represents a very useful tool for archaeological investigation and can provide a quantitative contribution to describe the spatial distribution of buried objects. In this work we show a new advanced tomographic approach, based on the parallel inversion of magnetic and electric observed data, aimed at the reconstruction of the subsoil of a still unexplored area of the archaeological site of Pompeii (Southern Italy). The survey was performed in collaboration with Pompeii's Archaeological Commission. The comparison between the results obtained from the tomographic inversions of both electrical and magnetic data was carried out in terms of the data inversions, which allowed us to obtain information about the location of the buried geophysical sources in the investigated subsoil. The results obtained seem to be in a good agreement, both for the position of the geophysical sources and for their dimensions.     

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.     

An Integrated Survey of Roman Urbanization at Potentia,Central Italy

Abstract

Our research contributes to the study of Roman urbanization in the Italian peninsula, both in the central Adriatic area and beyond. It focuses on the integrated use of archaeological field methods and non-destructive techniques. The study of the urban layout of the city of Potentia is an example of the use of low altitude aerial detection combined with regular grid-walking and geophysical survey to intensively investigate abandoned classical town sites. Information can be combined in a new approach to the study of urbanization processes in the heartland of the Roman world, and this integrated methodology can be applied to any large archaeological site with regular patterning such as orthogonal street layouts and planned civic centers.     

Shallow geophysical survey at the archaeological site of San Miguel Tocuila,Basin of Mexico

A combined near surface geophysical survey conducted in San Miguel Tocuila show that geophysical methods offer the possibility to characterize and reconstruct the geometry of subsurface structures without destroying the deposits, providing a way to find solutions to the questions of archaeological or engineering significance. The survey consisted of the application magnetometry, seismic refraction tomography (SRT) and ground penetrating radar (GPR) within a depth range of 10 m. Before Spanier conquest San Miguel Tocuila was a very prominent suburb of the main Aztec ceremonial complex located on the eastern margin of Lake Texcoco, central Mexico, where several mounds known as Tlateles in Nahuatl language have been identified. Nowadays, the rapid expansion of Mexico City's metropolitan area within the last four decades has strongly influenced Tocuila's environment and has compromised several of its archaeological and ancient human settlements. This study shows how the high resolution imagining of non-invasive geophysical methodologies in addition with surface archaeological studies [Parsons, J.R., 1971. Prehistoric Settlement Patterns in the Texcoco Region, Mexico. Memoirs of the Museum of Anthropology, University of Michigan, Number 3] provide different kinds of information that characterize the subsoil and a buried structure. Based on the history of the ancient settlements in the zone and considering the characteristics of shape and height of the structure, we interpreted that the subsurface images obtained depict a buried Tlatel which corresponds to a ceremonial–civic center of Late Aztec times.     

A MAGNETIC SURVEY OVER LA MAJA,AN ARCHAEOLOGICAL SITE IN NORTHERN SPAIN

A Roman archaeological site in northern Spain (La Maja, province of La Rioja) includes pottery workshops, part of an important ceramic industry that developed from about the first century BC to the first century AD. A geophysical study was planned to determine the extent of the industrial complex in the vicinity of an excavated kiln. Magnetic observations were done on a grid of 30 × 36m, with a sampling interval of 1m. Two dipolar-shaped anomalies were found: one in the north-east and the other in the south-west of the area. Low-pass and band-pass filters were used in the Fourier domain to enhance the characteristics of the magnetic data and to remove noise and undesirable shallow features. Three-dimensional polygonal prisms were used to model the magnetic anomalies based on palaeomagnetic measurements performed over an uncovered kiln that helped to constrain the induced and remanent parameters of the magnetizing fields.     

The use of magnetometry and pole-dipole resistivity for locating Nabataean Hawar archeological site in the SW-Jordan

This paper is focused on the joint use of magnetometry and pole-dipole electrical resistivity geophysical methods for assessing their capability in the detection of a prehistoric site in the southwestern Jordan. The survey area, Auara, was built in the first century BC during the Nabataean time and is located in a very arid environment framed on the east and north by white sandstone hills. In order to test this site, a number of magnetic stations and two pole-dipole resistivity traverses were carried out in the investigated area. Magnetic data were taken with one sensor at height of 0.8 m along survey lines spaced 1 m apart. Resistivity measurements were carried out utilizing the pole-dipole array along two profiles. A total of 32 geoelectrical stations spaced 2 m were made along the two profiles. Magnetic method found structure with contrasting physical properties to those of the surrounding material. The archeological interpretation of such structure is in terms of rectangular cistern (pool) with dimensions 26 × 16 m. A probable location of two buried walls spaced 16 m are indicated by low resistivity values.