Geophysical indicators of culturally emplaced soils and sediments

Archaeologists dealing with earthen forms must distinguish those constructed by humans from those with a natural origin. Geophysical techniques can help identify culturally loaded soils and sediments. We suggest that intrinsic changes in geophysical properties, due to cultural loading, can serve as fingerprints in determining whether a mound or other earthen form is natural or culturally constructed. Culturally emplaced soils might be identified through anomalous values in geophysical properties or through unusual spatial or stratigraphic complexity. The identification of this “lumpiness” in geophysical properties may involve geophysical techniques quite different from those employed in traditional archaeogeophysical surveys. Experiments at three prehistoric mound sites (the Cahokia Mounds State Historic Site, Effigy Mounds National Monument, and the Hopeton Earthwork) illustrate a number of these techniques including studies of the anisotropy (directionality) of geophysical properties, seismic Rayleigh (surface) waves, and magnetic susceptibility. © 2002 Wiley Periodicals, Inc.     

Usefulness of electrical and magnetic methods in finding buried structure of the Alabanda Ancient Cistern in Çine Town,Aydın City,Turkey

In this paper, the Electrical Resistivity Tomography and magnetic methods, including Tilt Angle and Euler Deconvolution, have been used in a comperative manner to determine the lineaments and depths of buried archeological structures. The zero contours of the tilt angle correspond to the boundaries of buried structures and the half distance between ±π/4 rad corresponds to the depth to the top of the structures. Also, in order to estimate the positions and depths of buried structures in the study area, the Euler Deconvolution method was applied to the total magnetic field data. All of the methods have a good correlation about determination of the horizontal locations and depths of the buried structures. The archeological excavations based on the geophysical investigations have demonstrated that the buried structure is an ancient cistern building because of the unearthed pools. Therefore, the interpretations of the geophysical methods and fiction of the paper were made according to the ancient cistern building. With this study, a buried ancient cistern structure was modeled and revealed by the geophysical methods for the first time. Additionally, using of these geophysical techniques in a comparative manner for the archaeogeophysical work will greatly contribute to future studies.     

Seismic tomography: Application for archaeological purposes

Work on the excavations at the ancient Etruscan settlement of Marzabotto (Bologna) restarted in 1988. These excavations, as they were worked, brought to light a complete urban layout represented primarily by foundations, courtyards, roads and wells. The site has been the focus of intensive experimentation to assess the feasibility of geophysical remote sensing in exploration archaeology. Different geophysical techniques have been tested at this site: geoelectric, electromagnetic, magnetic, and seismic methods. One of the methods tested was geophysical seismic tomography. This method utilizes straightray algorithms to map subsurface properties by analyzing the first signal arrival time. Seismic tomography treats the problem of identifying a buried structure as a wave propagation process by inverting the linearized wave equation to compute the spatial distribution of the slowness of the velocity. The purpose of our tomographic study is to further test the method and to guide archaeologists in their future excavations by locating and identifying buried structures. In particular, analyses are performed on the geometries, signal characteristics, discretization of the area, and constraints of the inversion algorithm in order to enhance the effectiveness of the tomographic reconstruction process and to reduce costs. A controlled experiment is presented for a typical Marzabotto buried structure with which it is possible to verify the effectiveness of the applied technique. It is demonstrated how proper field measures and an inversion test can provide reliable information that can be used to guide excavation work. © 1994 John Wiley & Sons, Inc.     

Detection of the near surface structure through a multidisciplinary geophysical approach

The present survey aimed to image the subsurface structure, including karstic voids, and to evaluate the extent of the heterogeneities that can result in potentially dangerous collapse of road segments overlying these features. A multidisciplinary geophysical approach (seismic refraction, frequency domain electromagnetic and ground penetrating radar) in combination with a detailed geological survey indicated the presence of tectonic faults as well as velocity and conductivity anomalies along an old road within the area of Akrotiri at Chania (Crete). Due to the presence of subsurface fuel pipes, perpendicular to the direction of the road, 2D resistivity imaging was excluded from the applied geophysical methods. Interpretation of the geophysical data revealed that the section of the road investigated overlies prominent voids attributed mostly to karst features. The conductivity and velocity anomalies are interpreted to indicate an area where the host limestone rock has been downthrown by faulting and associated karstification. The continuation of this fault zone was observed in the slope of the road during later excavations. Interpretation, using geographic information systems (GIS) to integrate data, allowed these controls and relationships to be understood and monitored. The above methodology was proved successful for areas where the application of resistivity method is not possible.     

Frozen mounds in Gorny Altai: geophysical and geochemical studies

The importance of pre-excavation permafrost detection within ancient burial mounds in the Altai by geophysical methods is hard to overestimate. There was no way of detecting small quantities of frozen ground or ice under stone mounds, and this is a topical issue in Russian archeology. Frozen mounds, which retain organic matter owing to natural processes, are an exceptional source of information about historical and cultural processes in the Early Iron Age. Pre-excavation geophysical prospecting is especially important in the context of global warming, which might destroy a whole layer of cultural and historical information.The integrated geophysical studies conducted in recent years focused on a group of archeological sites of the Pazyryk culture whose burial constructions are very likely to contain frozen artifacts. As a rule, such burial mounds are located at a considerable altitude and contain permafrost, which creates unique conditions for the preservation of artifacts. Such localities include the Ukok high plateau (southern Altai) and the northwestern part of Mongolian Altay. Systematic field studies were conducted on the Ukok Plateau in 2003 and 2007 and in the adjacent territory of Mongolian Altay in 2005 and 2006. The following geophysical methods were used: vertical electrical sounding (VES), electrical tomography (ET), shallow frequency scanning, georadiolocation, magnetic susceptibility measurements, gamma-ray spectrometry, and chromatography. The field works were planned with a heavy reliance on the 3D mathematical simulation of electric and EM fields, which is meant for a realistic estimate of the possibilities of geoelectrics and the best ways of its application to burial-mound studies and data interpretation.The excavations conducted in 2006 in northwestern Mongolia within the Altai Mts. confirmed the geophysical prediction of permafrost at all the sites identified by the geophysical studies in 2005. In one of the mounds, they yielded a unique intact tomb of a Scythian warrior.     

Surveying the Townscape of Roman Ammaia in Portugal: An Integrated Geoarchaeological Investigation of the Forum Area

Geoarchaeological research, integrating traditional excavations, and ground truthing with intensive geophysical surveys, aerial photography, and GIS‐based data processing, has revealed the full intramural plan of the abandoned Roman city of Ammaia in central Portugal. Although this multidisciplinary effort also focussed on understanding the town/territory relationships and the system of resource exploitation, this paper presents the most important results from fieldwork in the central monumental area of the town, the Roman Forum. Here, excavations, geomorphological survey, and an array of geophysical methods illuminate the long history of the site, from the first settlement and monument‐building phases in early Imperial times, to the ongoing post‐abandonment processes. This paper discusses some of the benefits of compiling these complementary data sets and proposes the use of a wide array of approaches in order to achieve full understanding of the complex topography and evolution of a classical urban site. It further demonstrates the need for effective stratigraphical control and geomorphological analysis of crucial areas revealed by high‐quality geophysics.     

Geophysical Surveys in the Jebel Hamrat Fidan,Jordan

The Jebel (Jebel is mountain in Arabic) Hamrat Fidan marks the “gateway” to the Feinan district of southern Jordan—one of the largest sources of copper during the prehistoric and Early Bronze Ages in the eastern Mediterranean. Preliminary excavations and surveys at sites along the Wadi Fidan have revealed a long history of settled occupation extending from the Pre‐Pottery Neolithic (ca. 6,500 B.C.) to early medieval times. Because of this long history of occupation, and the fact that this area was a regional center for the production of copper, the study of this area is important for understanding early metallurgy, craft specialization, and social evolution. During the summer of 1997, geophysical investigations at a series of Neolithic and Bronze Age sites identified specific areas within Wadi Fidan for future intensive excavations. Three geophysical techniques (electromagnetic induction, ground‐penetrating radar, and magnetometry) were used to help locate buried architectural and industrial features remaining from early mining and metallurgical operations, including copper ore bodies or voids. Geophysics was not used at the actual mining sites because of scheduling constraints; however, geophysics did delineate buried stone walls at three distinct Wadi Fidan sites. Magnetometry and ground penetrating radar provided little useful information. Buried stone walls were apparently “masked” by numerous magnetic stones on the ground surface making magnetometry useless. Reflections from known strata demonstrated that radar penetrated the ground adequately; however, known shallowly buried walls were not recognizable. Electromagnetic induction produced maps of linear and rectilinear features that suggested spatial distribution of widespread buried stone walls suitable for future excavation. A significant and unexpected finding was that electromagnetic induction proved capable of delineating buried stone walls. © 2000 John Wiley & Sons, Inc.     

Archaeological exploration using magnetic and GPR methods at the first court of Hatshepsut Temple in Luxor, Egypt

The Hatshepsut Temple at Luxor, southern Egypt was built as a garden for Amun, and the first court indeed had exotic trees and vegetations. The pathway to the temple was along a sphinx-lined causeway linking the valley to pylons, which are missing now. As an effort to outline remains of the vanished garden and missing pylons and any other possible archaeological structures at this first court site, an extensive integrated magnetic/ground-penetrating radar (GPR) geophysical survey was conducted. The magnetic survey covered the entire area of the first court (100?×?60 m), while the GPR survey covered only an area of 50?×?50 m. The acquired GPR data were processed and presented as 2-D depth sections providing a reasonable vertical/horizontal resolution for the upper 6 m of the investigated site. The acquired magnetic data was processed and presented as 2-D image. The integrated interpretation of the acquired GPR and magnetic data revealed some archaeological features including a rectangular depression which is presumably an ancient man-made pond in the garden of the temple, a rectangular feature that may be a foundation of the missing pylon of the temple, and a suite of aligned anomalies that could be the remnants of sphinx. Such findings reflect the archaeological potentiality of the surveyed site and outline the extension of the temple. Meanwhile, these results necessitate further geophysical investigation or archaeological excavation to be confirmed.     

The formation of farm mounds on the Island of Sanday,Orkney

A recent archaeological site survey of the island of Sanday on Orkney has identified a distinct concentration of 15 farm mounds. An immediate need is to determine the nature, age, and processes of formation of these very distinctive landform features. This paper reports a geoarchaeological investigation of three mounds at Westbrough, Langskaill, and Skelbrae. For the island as a whole, the mounds vary in diameter from 50 to 205 m, with deposits up to a thickness of 4.3 m. The mounds vary in their morphology, reflecting complex processes of accumulation, often intense disturbance, and in some cases, erosion by the sea. Sections at the three sites are described with analytical data also being given for particle size, percent loss-on-ignition, total phosphate, δ¹³C, and radiocarbon dating. The Westbrough and Skelbrae mounds were formed post-7th century A.D.; more detailed dating was possible for the Langskaill site, which was initiated in the early to mid 13th century. A steady and relatively rapid sedimentation rate (ca. 1.9 cm year⁻¹) took place over the 200 years following the initiation of the mound. The lower part of the Westbrough mound is distinguished by the presence of peat, interpreted as discarded bedding material, but the remainder of the investigated sections are composed dominantly of mineral sediments containing organic matter of terrestrial origin. It is suggested that these materials accumulated from the ash of domestic hearths as well as from the residues of bedding material from the byres (cattle sheds). Turves (vegetation plus some underlying soil) would have been cut, dried, and then used in the byres and such turves would have retained a significant mineral content. The implication is that the inherent fertility of the island made it unnecessary for the farmers to spread the dung over the fields. This may explain why there is the distinct concentration of these mounds on the island of Sanday, an island noted in earlier times for its fertile soils developed on calcareous sands.     

庐枞地区1:5万综合物化探调查的初步应用

庐江—枞阳地区是长江中、下游铁铜成矿带的重要组成部分,近年来开展了1:5万综合物化探调查,提供了丰富的地质信息,为普查找矿提供了重要的线索。本文侧重介绍该区综合物化探调查在解决基础地质问题方面的应用。     

大比例尺综合物探方法在深部矿产远景调查试点中的应用

开展深部找矿预测,地球物理方法发挥着重要作用,但是受多解性困扰。本文以湖南东北某金矿为例,探讨运用多种地球物理方法,提高深部找矿预测的准确性。开展了大比例尺重力测量、地面高精度磁法及可控源音频大地电磁测深法观测,圈定了深部找矿靶区,经钻孔及地球物理电、磁测井验证,效果突出,确定了本区的地球物理找矿标志。表明应用综合物探方法在本区深部矿产远景调查评价中是快捷有效的,建议将这一地球物理勘查模式在全国的深部矿产远景调查评价中予以推广。     

综合物化探方法在地质找矿“攻深找盲”中的应用

物化探找矿方法面临着新形势下复杂地质条件中找矿的新挑战,单一物化探分析方法很难具有说服力,综合各种地质信息和勘探方法显得尤为重要。笔者结合河南省某矿床的找矿实践,介绍了高精度磁测、X荧光土壤分析和EH4测深等物化探综合分析方法,在工作区内发现了与成矿有关的物化探异常,经查证与地表地质现象吻合较好,说明该综合物化探评价技术方法在该矿床的应用是成功的,显示了其快速、高效和精准的特点。     

Archaeomagnetic record from Modoc Rock Shelter,Illinois, for the time range of 6200–8900 B.P.

The Modoc Rock Shelter is located in Randolph County, Illinois at the base of the Mississippi River bluffs, and is documented as having human occupation from 9000 B.P. to as recently as 800 B.P. Two hundred twenty-eight archaeomagnetic samples were collected from 28 surface hearths in two different excavation areas. Pilot samples from each hearth were A.F. demagnetized to 100 mT to establish the optimum demagnetization level for all samples from a specific hearth. The magnetic directions for individual hearths after appropriate demagnetization have high precision with α-95 values between 2° and 4°. Independent inclination and declination records from the two excavations, which were correlated with conventional radiocarbon dates, overlap in time and show good correlation. The composite record shows a prominent eastward declination swing of 15° from 6500–7800 yr B.P., followed by a westward swing of equal magnitude from 8000–8900 yr B.P. The inclination record is less varied. This secular variation record correlates well with soft sediment records from lakes in the north-central United States and is perhaps the longest and oldest archaeomagnetic secular variation record from a single site in North America. © 1997 John Wiley & Sons, Inc.     

物探在金伯利岩型原生金刚石矿勘查中的应用——以辽宁瓦房店金刚石矿田为例

辽宁瓦房店金刚石矿田是我国重要的金伯利岩型金刚石矿集区.为了更好地发挥物探在该区寻找金刚石矿的作用,对以往物探工作程度、使用的方法、取得的成果进行了系统梳理.通过总结发现,地面磁测在圈定浅地表金伯利岩体中发挥了重要作用;在寻找深部隐伏金伯利岩体时,音频大地电磁测量、井中物探发挥了重要作用;在研究金刚石矿控矿因素等问题时,1∶5万区域重力测量、大地电磁剖面测量发挥了重要作用.总之,物探是瓦房店矿田金刚石矿勘查中的重要组成部分,合理的方法组合能够解决相应的地质问题.     

冀北步古沟一带萤石矿地物化找矿技术方法组合研究

地物化综合信息在热液充填型萤石矿找矿的应用探索具有重要意义。本文以冀北步古沟一带萤石找矿为例,通过综合物化探方法进行有效性试验,总结该地区萤石矿地物化找矿技术方法组合。在地质调查基础上,系统开展了1:5万水系沉积物地球化学测量、1:1万土壤剖面测量、高精度磁法测量、天然电场选频测量、电阻率联合剖面测量及高密度电阻率测量等找矿技术方法探索。结果表明,1:5万水系沉积物测量及1:1万土壤剖面测量等化探方法可辅助锁定找矿目标区;高精度磁法及天然电场选频测量,可初步判定断裂的位置;电阻率联合剖面及高密度电阻率法测量可进一步探测含矿断裂构造的位置、产状及延伸。通过以上试验研究,建立了冀北地区萤石矿地物化找矿技术方法组合,经工程验证在研究区内新发现萤石矿点1处,取得了较好的效果。实践表明,该套地物化找矿技术方法组合可进一步指导冀北地区的萤石矿找矿工作。     

综合物化探技术在中-南祁连山察汗诺北部航磁异常检查中的应用

文章以青海中-南祁连山察汗诺北部的青C-2012-280和青C-2012-281号航磁异常检查为例,在综合前人地质、物化探和矿产资料的基础上,采用地质剖面测量、高精度磁法剖面测量、岩石磁参数测量和岩石地化剖面测量方法进行航磁异常地面检查。分析磁异常形成的地质原因,对航磁异常做出定性判断,对异常的成矿潜力进行评价,对下一步的工作提出了建议。综合物化探方法在青海省中-南祁连山的航磁异常检查和找矿工作中取得了良好的效果。     

Contribution of electrical tomography methods in geotechnical investigations at Mavropigi lignite open pit mine,Northern Greece

In this paper, the application of 2D and 3D electrical resistivity methods in geotechnical investigations is explored through a case study in Northern Greece. These two methods were employed at a lignite surface mining operation where fracture zones and discontinuities have been recently observed close to the pit boundaries. The main aim of the geophysical survey was to estimate the inclination of the contact between the Neogene and Schist/Carbonate formations near the southern limits of the pit, as well as to estimate the thickness of the carbonate rocks on top of the Schist formations to evaluate the stability of the southern slopes. Synthetic data were initially generated to help plan an efficient electrical tomography survey, in a region with complex geology and irregular terrain. Three configurations (Wenner–Schlumberger and dipole–dipole or pole–dipole) proved essential in such conditions and helped improving the resolution of the resistivity section. The sections were then calibrated by boreholes. Finally, the geophysical survey provided invaluable data regarding the geometry of the bedrock and possible faults, which was essential for the slope stability calculations.     

地球物理方法在塔里木盆地孔雀河斜坡带砂岩型铀矿预测评价中的应用

对塔里木盆地孔雀河斜坡带主要地质单元(岩石)的电性、密度、地震波阻抗等参数特征进行了分析研究,将地面γ能谱测量、土壤氡法、瞬变电磁测深、浅层地震勘探等方法,在这一地区找铀矿的应用效果综合评价后,认为本区具有开展多种地球物理方法的物性前提。孔雀河斜坡带北部盖层产状平缓,具有冲积扇-河流相沉积体系,且有放射性元素富集的迹象,是砂岩型铀矿成矿的有利地区。     

重力和磁力勘探进入新时期

评论了航空重力测量和航空磁测观测技术,认为重力和磁力勘探进入一个新时期的标志是:航空矢量磁测、全张量磁力梯度测量、航空重力测量、重力梯度测量和无人飞行器地球物理探测。