A geophysical survey in the archaeological site of Archontiko, Yannitsa

The ancient settlement of Archontiko is 4.5 km NW of ancient Pella in North Greece (Figure 1). The findings showed that the area was first occupied by the end of the Iron Age, i.e. 650-550 B.C. Also, showed that the topographic table of Archontiko was a major settlement of the Yannitsa province due to its concessive position by the main roads of Macedonia (Chrysostomou A. and Chrysostomou P., 1993). At the upper layers of the ruins, findings of the Roman and Byzantine times were also unearthed. The geophysical methods have been used in order to detect and map antiquities in various sites in Greece (e.g., Tsokas et al., 1994; 1995; Sawaidis et al., 1999). The resistivity mapping employing the twin probe array, the total magnetic field variations, the airborne photos and the Ground Probing Radar are the most popular methods in this respect. However, almost all geophysical methods can be used to tackle specific problems. From 1992 till 1994, many geophysical surveys were carried out in the area of Archontiko to collect mainly magnetic data. Resistivity measurements were also conducted in a small part of the area. The data presented in this study cover the northern side of the topographic table of Archontiko and they were collected during two campaigns during the summer of the years 1992 and 1993 (Figure 2).

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Spectral method for processing hydromagnetic survey data at shallow depths

10.5194/egusphere-egu21-11168 ◽

2021 ◽

Author(s):

Kirill Kuznetsov ◽

Kiryukhina Elena ◽

Bulychev Andrey ◽

Lygin Ivan

Keyword(s):

Magnetic Field ◽

Spectral Method ◽

Magnetic Field Gradient ◽

Geophysical Methods ◽

Temporal Variations ◽

Magnetic Data ◽

Field Reconstruction ◽

Anomalous Magnetic Field ◽

Single Moment ◽

Magnetic Field Variations

Magnetic surveys are commonly used for solving variety of geotechnical and geological challenges in offshore areas, jointly with a set of other geophysical methods. The most popular technique employed is hydromagnetic surveying with towed magnetometers. One of the most significant challenges encountered during processing of the magnetic data is related to temporal variations of the Earth's magnetic field. Accounting for diurnal magnetic field variations is often done by carrying out differential hydromagnetic surveys, a technique developed in the 1980-s. It is based on simultaneous measurements of the magnetic field using two sensors towed behind the vessel with a given separation. This technique allows to calculate along-course gradient which is free of magnetic field temporal variations. This measurement system resembles a gradiometer, with the distance between two sensors being referred to as the base of the gradiometer. It is possible to calculate anomalous magnetic field by integrating obtained magnetic field gradient. Studies have shown that accuracy of its reconstruction decreases with increasing base of the gradiometer. This becomes most significant when distance between the sensors and sources of magnetic field anomalies is small. This situation occur when the survey area is located in shallow water (i.e. for shallow marine, river or lake surveys).An approach for deriving magnetic anomalies and accounting for diurnal variations in differential hydromagnetic surveys based on the frequency (spectral) representation of the measurements was proposed in 1987 [Melikhov, 1987]. This approach utilizes the fact that it is possible to reconstruct the spectrum of magnetic field anomalies along the vessel course from the spectra of measured signals from the first S1(&#969;) and second S2(&#969;) sensors. Assuming that the sensors are located at the same depth, it can be achieved via the following transform:<img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gepj.3d3911bac60061487501161/sdaolpUECMynit/12UGE&app=m&a=0&c=ff23bad5ed5181be02f7ef7ab5e8d6e4&ct=x&pn=gepj.elif&d=1" alt="" width="192" height="43">where &#969; - spatial frequency, l - base of the gradiometer, and i - imaginary unit. Assuming that at a single moment in time magnetic field variations equally affect both sensors, resulting Fourier spectrum T(&#969;) will correspond the spectrum of anomalous magnetic field, free of the magnetic variations. It should be noted that, similar to the along-course gradient integration approach, anomalous magnetic field is restored to a certain accuracy level.Estimates made on model examples showed that accuracy of the field reconstruction using this method is comparable to the accuracy levels of modern marine magnetic surveys (&#177;1-3 nT). It could be noted that for gradiometer bases comparable or larger than depths to magnetic anomaly sources, errors of the field reconstruction are significantly lower for the spectral transformation-based approach compared to along-course gradient integration.References:Melikhov V.R., Bulychev A.A., Shamaro A.M. Spectral method for solving the problem of separating the stationary and variable components of the geomagnetic field in hydromagnetic gradiometric surveys // Electromagnetic research. - Moscow. IZMIRAN, 1987. - P. 97-109. (in Russian)&#160;

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Exploring the Consistency of Data Collected in Archaeological Geophysics: A Case Study from the Iron Age Hillfort of Villasviejas del Tamuja (Extremadura, Spain)

Remote Sensing ◽

10.3390/rs12121989 ◽

2020 ◽

Vol 12 (12) ◽

pp. 1989

Author(s):

Carmen Pro ◽

Bento Caldeira ◽

Maria Teresa de Tena ◽

Cristina Charro ◽

Rui Jorge Oliveira ◽

...

Keyword(s):

Spatial Correlation ◽

Iron Age ◽

Geophysical Methods ◽

Archaeological Site ◽

Resistivity Tomography ◽

Archaeological Interpretation ◽

Ground Penetrating ◽

Magnetic Gradiometry ◽

Strong Agreement

Different geophysical methods applied at the settlement of Villasviejas del Tamuja (Botija, Spain) have identified robust anomalies located at the same position, but some anomalies are reflected by only one method. Furthermore, analysing the spatial correlation of these anomalies is of fundamental importance for obtaining a correct archaeological interpretation. In this work, we analysed the main results of electrical resistivity tomography (ERT), ground-penetrating radar (GPR) and magnetic gradiometry methods in a particular area of the archaeological site. In this analysis, we performed graphical and numerical spatial correlation analyses of the anomalies and observed strong agreement among the results provided by each method. Certain anomalies were reflected only in the magnetic and ERT studies. The results highlight the importance of applying several geophysical methods and performing spatial correlational analyses. Furthermore, the methodology that we have applied to evaluate the spatial correlation offers interesting results.

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Sites of archaeology in Ulvivok and its surroundings in the research of Lviv scientists

Materials and studies on archaeology of Sub-Carpathian and Volhynian area ◽

10.33402/mdapv.2019-23-337-361 ◽

2019 ◽

Vol 23 ◽

pp. 337-361

Author(s):

Dmytro Pavliv

Keyword(s):

Bronze Age ◽

Iron Age ◽

Archaeological Site ◽

Large River ◽

Archaeological Sites ◽

Archaeological Heritage ◽

History Of ◽

Almost All ◽

Xix Century ◽

The Village

The old village of Ulvivok, located above the Bug River in Sokal district, Lviv region, is extremely rich with archaeological sites. Relief, favourable for living, fertile soils, large river have contributed to appearing of human settlements on this area since ancient times. This fact is witnessed by finds of numerous archaeological artifacts near Ulvivok and discovery of significant archaeological sites – cemeteries and settlements, which have an interesting history of research since the late XIX century and till nowadays, associated with many famous Lviv scientists. An important role in the preservation and study of local archaeological finds was played by Dzieduszycki Museum. The first references to finds from Ulvivok and the surrounding villages – Horodylovychi, Stargorod, Skomorokhy and Telyazh – are found at the works of local historian B. Sokalski and geologist A. Lomnitcki, published in 1899. J. Nykorovych – the owner of the village and amateur archaeologist contributed noticeably preservation and research of sites during XIX – beginning of XX century. The first extensive exploration in Ulvivok in 1923 was conducted by archaeologist and local historian, guardian of the prehistoric monuments of Lviv district B. Janusz, who discovered a tomb of Globular Amphorae culture and part of the burials of the most famous archaeological sites near Ulvivok – inhumation cemetery from the end of Bronze Age of “Ulvivok-Rovantsi type”. The same cemetery was investigated in 1931 by archaeologist T. Sulimirski, who published the results of excavations. Local archaeological finds were studied by famous Ukrainian archaeologist J. Pasternak, J. Bryk, K. Żurowski, J. Dąmbrowski, I. Sveshnikov, L. Krushelnytska. Nowadays, the exploration work was conducted by N. Wojceschuk, surveys in Ulvivok, Horodylovychi, Stargorod and excavation of Early Iron Age site were carried out by D. Pavliv. At least 14 archaeological sites (8 settlements and 6 cemeteries) and about 100 individual finds have been found on the territory of the village and surrounding area. This territory on the western part of Ukraine is extremely rich with archaeological sites of almost all epochs. It is witnessed by the great historical importance of this region and requires continuation of professional archaeological examinations and protective actions for the preservation of archaeological heritage. Key words: Ulvivok, archaeological site, Lviv scientists, Globular Amphorae culture, burial complex of Ulvivok-Rovantsi type.

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Remote and geophysical methods in the study of the uniguely preserved early iron age landscape of the upper part of the Lake Donuzlav in Crimea

Proceedings of the International conference “InterCarto/InterGIS” ◽

10.35595/2414-9179-2020-4-26-213-227 ◽

2020 ◽

Vol 26 (4) ◽

pp. 213-227

Author(s):

Sergej Muld ◽

Anna Antipenko ◽

Andrej Gavrilyuk ◽

Sergej Fridrikhson ◽

Ivan Zhivanyuk

Keyword(s):

Iron Age ◽

Cultural Landscape ◽

Building Materials ◽

Local Population ◽

Geophysical Methods ◽

Structural Features ◽

Aerial Photographs ◽

Survival Strategies ◽

Early Iron Age ◽

Geophysical Surveys

The article discusses the results of remote and geophysical studies, as well as selective excavations in the upper reaches of one of the largest and deepest lakes of Crimea — Donuzlav, which separate Tarhankut from the rest of the peninsula. Due to the unique landscape features, this region had important economic and communicative significance in all historical periods, especially in the early Iron Age: nomadic paths from the steppes to winter pastures and natural shelters of the Tarkhankut Peninsula extended to the sea and Chersonessian trade and military routes resembled here. To study the cultural landscape of Lake Donuzlav and its branched ravines system, a comprehensive technique was developed combining the methods of cartography, remote sensing, GIS, geophysics, ground-based automobile-foot archaeological explorations and selective excavations. With the help of detailed historical maps, the main routes and crossings of the autochthonous population of the early Iron Age and ancient Greek colonists were revealed. The presence of natural shelters (deep ravines and balkas, capes and cliffs) and the richness of natural resources of Donuzlav (the abundance of fresh water, fertile soil, building materials (stone, clay, wood, reeds), food (fish, shellfish, wildfowl), led to dense population in the early Iron Age. The use of archival aerial photographs of 1943 and 1971, as well as satellite photographs of 1966 in combination with modern high-resolution satellite imagery revealed at least two dozen of settlements of the Early Iron Age along the shores and in the ravine system of the upper reaches of Lake Donuzlav. Terrestrial archaeological explorations were accompanied by geophysical surveys (magnetic, electromagnetic surveys) of the most promising objects. Using magnetic maps of the identified settlements, locations for archaeological spotting were determined. Excavations at the sites selected based on the results of remote and geophysical studies have revealed typical structural features of houses and outbuildings of the local population of the early Iron Age. These features were determined by the presence of local natural building materials: dense building limestone of the Sarmatian geological layer, clay and reeds growing in the lower reaches of the ravines that flow into Donuzlav Lake. As a result of the study, it was concluded that the unique natural-historical landscape of the upper reaches of Lake Donuzlav is the key to adaptation methods, survival strategies, and economic models of the Early Iron Age population in Northwest Taurica.

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Multi-sensing geophysical surveys at the Archaeological Park of Paestum: the discovery of a small Doric temple

10.5194/egusphere-egu21-13191 ◽

2021 ◽

Author(s):

Ilaria Catapano ◽

Luigi Capozzoli ◽

Giovanni Ludeno ◽

Gianluca Gennarelli ◽

Gregory De Martino ◽

...

Keyword(s):

Ground Penetrating Radar ◽

Spatial Scales ◽

Geophysical Methods ◽

Construction Materials ◽

Archaeological Site ◽

Heritage Management ◽

Magnetic Characteristics ◽

Geophysical Surveys ◽

Earth Magnetic Field ◽

Ground Penetrating

Nowadays, non-invasive sensing technologies working at different spatial scales represent a recognized tool to support archaeological researches, because their deployment and cooperative use allow detection and localization of buried ruins before performing excavation. Therefore, they get significant advantages in planning the stratigraphic assays, while reducing costs and times, and support holistic approaches where cultural heritage management, protection and fruition aspects are considered under a unified context.As a further example among those available in literature, this communication summarizes a successful case study carried out at the Archaeological site of Paestum, sited in the southern Italy [1].Based on the analysis of aerial imagery and several unexpected archaeological findings, terrestrial measurement campaigns, involving magnetometer (MGA) [2] and ground penetrating radar (GPR) [3] methodologies, were carried out in the northwest quarter of the ancient city near the fortification wall and few meters away from the gate of Porta Marina. As detailed in [4], the MGA was exploited to investigate a large subsurface area in a relatively short time and allowed the identification of the most significant archaeological anomalies, by accounting for the variations of the earth magnetic field due to the different magnetic susceptibilities of construction materials and the magnetic characteristics of the shallow subsoil. The georeferenced MGA image was exploited to select the area requiring a further and more detailed survey, which was performed by means of GPR. Then, GPR data were processed by means of a microwave tomography based approach [4], which allowed a high resolution three dimensional reconstruction of buried targets starting from the electromagnetic field that they backscatter when illuminated by a known incident field. By doing so, detailed information about depth, shape, and orientation of the buried targets were retrieved and an impressive visualization of the the basement of the structure was achieved.The area is currently under excavation and the initial discovered ruins fully confirm the hypotheses formulated on the basis of the elements found on the surface, the photo interpretations and geophysical investigations. The proposed reconstructive hypothesis of the building as a whole is a stylobate of 10.83 m x 6.80 on which 4 x 7 columns were arranged, with a significantly increased intercolumniation on the short sides (2.02 m) compared to the long sides (1.68 m).[1] https://www.museopaestum.beniculturali.it/?lang=en[2] A. Aspinall, C. Ga&#64256;ney, A. Schmidt, A Magnetometry for archaeologists. Geophysical methods for archaeology, Altamira Press, Lanham, (2008).[3] D. J. Daniels, Ground penetrating radar, IET, (2004).[4] Capozzoli, L.; Catapano, I.; De Martino, G.; Gennarelli, G.; Ludeno, G.; Rizzo, E.; Soldovieri, F.; Uliano Scelza, F.; Zuchtriegel, G. The Discovery of a Buried Temple in Paestum: The Advantages of the Geophysical Multi-Sensor Application. Remote Sens. 2020, 12, 2711.

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AIRBORNE GRAVITY GRADIOMETRY SURVEY IN THE SOUTHEASTERN PORTION OF PIMENTA BUENO GRABEN IN PARECIS BASIN: INTEGRATED 2D FORWARD MODELING AND ITS IMPLICATIONS IN DEFINING A NEW STRUCTURAL FRAMEWORK

Brazilian Journal of Geophysics ◽

10.22564/rbgf.v33i1.605 ◽

2015 ◽

Vol 33 (1) ◽

pp. 101 ◽

Cited By ~ 2

Author(s):

Alan De Souza Cunha ◽

Fábio Andre Perosi ◽

Luiz Fernando Braga ◽

Leandro Barros Adriano ◽

Marlon Cabrera Hidalgo-Gato ◽

...

Keyword(s):

Geophysical Methods ◽

Forward Modeling ◽

Magnetic Data ◽

Airborne Gravity ◽

Gravity Gradiometry ◽

Seismic Section ◽

Technical Data ◽

Geophysical Surveys ◽

Well Data ◽

Airborne Gravity Gradiometry

ABSTRACT. Airborne geophysical surveys are widely used in geological prospecting of hydrocarbon reservoirs. The efficiency and acquisition speed of these methods in covering large areas accredit them as a key tool for any exploration project where there are sparse technical data available to support the exploratory decisions. Among the airborne geophysical methods, potential methods, namely, gravity and magnetics are the most spread in oil & gas projects of this nature. Such methods are used to support the generation of regional geological knowledge and also in detailed approaches, integrated with seismic, geochemical and well data. The objectives of this work were to describe the FalconTM Airborne Gravity Gradiometry System, explaining acquisition and processing steps, and crosscheck the results of its application in the southeastern portion of the Parecis Basin with two proposed models for the structural genesis and evolution proposed by the academy. Throughout the integration of the airborne gravity gradiometry and magnetic data along 2D seismic section it was possible to infer the geometry of the Pimenta Bueno Graben. While many works have mapped basement depth about 7,000 m, the current modeling shows basement deeper than 10,000 m.Keywords: airborne gravity gradiometry, 2D forward modeling, Parecis Basin, FalconTM, tectonic framework.RESUMO. Levantamentos aerogeofísicos são amplamente utilizados na prospecção geológica de reservatórios de hidrocarbonetos. A eficiência e a velocidade de aquisição desses métodos na cobertura de grandes áreas os credenciam como uma ferramenta fundamental para qualquer projeto de exploração onde há poucos dados técnicos disponíveis para apoiar as decisões exploratórias. Dentre os métodos geofísicos aéreos, os potenciais gravimétricos e magnetométricos são os mais utilizados em projetos da natureza de prospecção de óleo e gás. Tais métodos são utilizados para apoiar a geração de conhecimento geológico regional e também em abordagens de detalhe, integrados com seções sísmicas, dados geoquímicos e de poço. Este trabalho pretende apresentar o Sistema FalconTM de Gravimetria Gradiométrica, descrevendo suas etapas de aquisição e processamento, e interpretação dos resultados de sua aplicação na porção sudeste da Bacia do Parecis, em confronto com dois modelos propostos para a gênese e evolução estrutural da Bacia. Através da integração dos dados de gravimetria gradiométrica com dados magnéticos extraídos ao longo da secção sísmica 2D foi possível inferir a geometria detalhada do graben de Pimenta Bueno. Enquanto trabalhos anteriores mapearam a profundidade do embasamento em cerca de 7.000 metros, uma modelagem 2D direta e vinculada mostra que o mesmo pode alcançar, de forma localizada, profundidades maiores que 10.000 metros.Palavras-chave: gravimetria gradiométrica aérea, modelagem direta 2D, Bacia dos Parecis, FalconTM, arcabouc¸o tectônico.

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Electrical and GPR prospecting at Palo Blanco archaeological site, northwestern Argentina

Geophysics ◽

10.1190/1.2345193 ◽

2006 ◽

Vol 71 (6) ◽

pp. B193-B199 ◽

Cited By ~ 15

Author(s):

Luis Martino ◽

Néstor Bonomo ◽

Eugenia Lascano ◽

Ana Osella ◽

Norma Ratto

Keyword(s):

Ground Penetrating Radar ◽

Complex Structure ◽

Geophysical Methods ◽

Archaeological Site ◽

2D Inversion ◽

Residential Units ◽

Geophysical Surveys ◽

Ground Penetrating ◽

Different Levels ◽

Age Estimates

We conducted a geophysical survey at the Palo Blanco archaeological site located in Catamarca, Argentina. Age estimates from radiocarbon dating indicate first occupation of the site around 1500 years ago. The first description of thesite was done in 1960. At that time, five residential units with different architectural arrangements were reported. These structures had different levels of deterioration caused by exposure and human activities. Some of these original structures have become completely covered by sediments. To aid in the design of efficient excavation plans, detailed maps are required to locate the buried walls. For this purpose, we conducted geophysical surveys over one of the structures. We had poor documentation about the structure at the time of the survey. Only one of the walls described in the earlier report was partially visible. We used two geophysical methods: ground-penetrating radar (GPR) and electrical resistivity. We performed 2D inversion of the resistivity data, together with numerical GPR simulations. These helped to distinguish the expected reflection events from others, aiding in a correct interpretation of the data. Finally, we made a complementary interpretation of the resistivity and GPR data to compile a detailed map of the selected structure. We found that considering the two methods independently would have led to an incomplete map. We delineated a much more complex structure than originally expected and designed an excavation plan which was carried out. The layout of the rooms of the structure fully matched the predictions based on the interpretation used in detecting the walls and their depths. In this way, the geophysical forecasts were confirmed after excavation.

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Geophysics for urban mining and the first surveys in Denmark: rationale, field activity and preliminary results

Geological Survey of Denmark and Greenland Bulletin ◽

10.34194/geusb.v44.5240 ◽

2020 ◽

Author(s):

Alessandro Sandrin ◽

Aleksandar Maricak ◽

Björn H. Heincke ◽

Rune J. Clausen ◽

Lars Nielsen ◽

...

Keyword(s):

Seismic Refraction ◽

Geophysical Methods ◽

P Wave ◽

Magnetic Data ◽

Seismic Velocities ◽

Quaternary Sediments ◽

Development Activity ◽

P Wave Velocity ◽

Geophysical Surveys ◽

Field Activity

Geophysical methods have been widely used in recent decades to investigate and monitor landfill sites for environmental purposes. With the advent of the circular economy, waste contained in old landfills may be considered a resource that can be developed. Since the content of old landfills is largely unknown, the occurrence and quantity of valuable materials must be investigated before embarking on any development activity. Two landfills on Sjælland, Denmark (located at Hvalsø and Avedøre) were selected for a pilot study to characterise their content. At both locations, a set of geophysical surveys is underway. Here, we present the data obtained from magnetic and 2D seismic refraction surveys. Magnetic data show various anomalies that can be interpreted as caused by iron-rich waste. At both sites, the landfill material results in generally low P-wave velocity (<400 m/s), lower than those obtained for Quaternary sediments at Avedøre. The seismic velocities appear to increase in the presence of metals or by compaction with depth (>550 m/s). We propose that seismic refraction can thus define the bottom of the landfill and possibly its internal structure, especially when combined with other methods.

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Cooperative use of non invasive sensing methodologies for the geophysical monitoring of the archaeological park of Paestum

10.5194/egusphere-egu2020-7077 ◽

2020 ◽

Author(s):

Luigi Capozzoli ◽

Francesco Soldovieri ◽

Enzo Rizzo ◽

Ilaria Catapano ◽

Giovanni Ludeno ◽

...

Keyword(s):

New York ◽

Ground Penetrating Radar ◽

Geophysical Methods ◽

Archaeological Site ◽

Campania Region ◽

Non Invasive ◽

Novel Approach ◽

Ancient City ◽

Geophysical Surveys ◽

Ground Penetrating

The deployment of non-invasive sensing methodologies capable of providing information useful to characterize, monitor and manage archaeological sites represents a fundamental step for the conservation/preservation of cultural heritage assets. In the framework of the national project VESTA (funded by the Campania Region), several non invasive activities have been carried out for testing a novel approach of analysis including in situ methodologies, drone and satellite technologies.This communication deals with a case study carried out at the monumental archaeological site of Paestum, sited in the southern Italy, where Greek settlers founded the ancient city of Poseidonia (6th century B.C.) [1]. At this site, geophysical surveys based on the combined use of magnetometric analyses [2], geoelectrical surveys [3] and ground-penetrating radar measurements [4] have been performed. Specifically, the areas immediately close to the temples of Ceres and Neptune have been investigated to identify unknown and buried archaeological features and characterise the paleo-morphological context. The different resolution and depth of investigations related to the application of each one of the considered methodologies as well as the use of tomographic methodologies for the data processing allowed the collection of images showing different subsurface features of the investigated area at different spatial scale. These images made possible the identification of anomalies of the subsoil, which were useful both to respond to the questions of the archaeologists and give new perspectives for managing the site. At the conference, the results of the integrated geophysical surveys, as well as their archaeological interpretation, will be presented with a focus on the cultural and social value of the &#8220;water resource&#8221; for the ancient city of Poseidonia.&#160;[1] https://www.museopaestum.beniculturali.it/?lang=en[2] A. Aspinall, C. Ga&#64256;ney, A. Schmidt, A Magnetometry for archaeologists. Geophysical methods for archaeology, Altamira Press, Lanham (2008).[3] A. Binley, A. Kemna, DC resistivity and induced polarization methods. InHydrogeophysics Water and Science Technology Library; R. Yuram, S.S- Hubbard, S.S., Eds.; Springer: New York, NY, USA (2005).[4] D. J. Daniels, Ground penetrating radar, IET (2004).

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Integration of Multi-geophysical Approaches to Identify Potential Pathways of Heavy Metals Contamination - A Case Study in Zeida, Morocco

Journal of Environmental and Engineering Geophysics ◽

10.32389/jeeg9-067 ◽

2020 ◽

Vol 25 (3) ◽

pp. 415-423

Author(s):

Ahmed Lachhab ◽

El Mehdi Benyassine ◽

Mohamed Rouai ◽

Abdelilah Dekayir ◽

Jean C. Parisot ◽

...

Keyword(s):

Heavy Metals ◽

Seismic Velocity ◽

Seismic Refraction ◽

Geophysical Methods ◽

Low Frequency ◽

Electrical Current ◽

P Wave ◽

Low Resistivity ◽

Refraction Tomography ◽

Geophysical Surveys

The tailings of Zeida's abandoned mine are found near the city of Midelt, in the middle of the high Moulouya watershed between the Middle and the High Atlas of Morocco. The tailings occupy an area of about 100 ha and are stored either in large mining pit lakes with clay-marl substratum or directly on a heavily fractured granite bedrock. The high contents of lead and arsenic in these tailings have transformed them into sources of pollution that disperse by wind, runoff, and seepage to the aquifer through faults and fractures. In this work, the main goal is to identify the pathways of contaminated water with heavy metals and arsenic to the local aquifers, water ponds, and Moulouya River. For this reason, geophysical surveys including electrical resistivity tomography (ERT), seismic refraction tomography (SRT) and very low-frequency electromagnetic (VLF-EM) methods were carried out over the tailings, and directly on the substratum outside the tailings. The result obtained from combining these methods has shown that pollutants were funneled through fractures, faults, and subsurface paleochannels and contaminated the hydrological system connecting groundwater, ponds, and the river. The ERT profiles have successfully shown the location of fractures, some of which extend throughout the upper formation to depths reaching the granite. The ERT was not successful in identifying fractures directly beneath the tailings due to their low resistivity which inhibits electrical current from propagating deeper. The seismic refraction surveys have provided valuable details on the local geology, and clearly identified the thickness of the tailings and explicitly marked the boundary between the Triassic formation and the granite. It also aided in the identification of paleochannels. The tailings materials were easily identified by both their low resistivity and low P-wave velocity values. Also, both resistivity and seismic velocity values rapidly increased beneath the tailings due to the compaction of the material and lack of moisture and have proven to be effective in identifying the upper limit of the granite. Faults were found to lie along the bottom of paleochannels, which suggest that the locations of these channels were caused by these same faults. The VLF-EM surveys have shown tilt angle anomalies over fractured areas which were also evinced by low resistivity area in ERT profiles. Finally, this study showed that the three geophysical methods were complementary and in good agreement in revealing the pathways of contamination from the tailings to the local aquifer, nearby ponds and Moulouya River.

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