Magnetic surveys of archaeological sites can be influenced by the natural time variations of the Earth’s magnetic field, and to a lesser extent its spatial variations. The influence of the natural time variations could be especially problematic for single sensor surveys with limited base station coverage, and it is this aspect we address in this presentation. At any one location in the UK the magnetic field varies by 10s of nanoTeslas (nT) every single day, and by 100 to 1000s of nT during magnetic storms. We quantify the global characteristics of the time-varying field using hourly standard deviations from approximately 150 sites throughout the world and spanning over 40 years. We illustrate in detail how they vary with location, time of day, month and phase of the solar activity cycle. The most vulnerable magnetic surveys are those done at archaeological sites in or near the high latitude auroral zones, especially during the local night time (fortunately unlikely from a practical point of view) in March and October in the maximum and descending phases of the approximately 11-year solar activity cycle. Surveys done close to the dip equator are also vulnerable. We describe briefly the causes of these patterns. The existence of spatially incoherent signals in archaeological magnetic surveys may sometimes be difficult to deal with in the post-survey analysis and independent data, from a base station or from a nearby observatory or variometer station, could be helpful in this respect. It should be noted that the forthcoming maximum in solar activity is expected in 2013/14. Details are provided of the network of observatories and variometer stations that could help isolate and remove these time-varying signals from archaeological magnetic survey data by providing substitute base station data in near real time. The World Data Centre for Geomagnetism operated by the British Geological Survey in Edinburgh and available online at www.wdc.bgs.ac.uk, is a good first point of contact for magnetic data and metadata from observatories around the world. In the UK continuous magnetic data series are available from the observatories operated by the BGS at Lerwick in Shetland, Eskdalemuir in Dumfries and Galloway and Hartland in Devon.
We exploited ERS-1/2 and ENVISAT Persistent Scatterer Interferometry (PSI) datasets of the Italian Extraordinary Plan for Environmental Remote Sensing (EPRS-E), to analyse ground motions over two Italian cultural heritage sites. The deformation patterns over the archaeological site of Capo Colonna in Calabria Region, confirmed the persistent exposure of the ruins to regional-scale land subsidence, with up to 5-10 mm/yr motion velocity observed for the Column. Similarly, a high level of conservation criticality was assigned to the church of San Romolo in the countryside settlement of Bivigliano, Northern Tuscany. The strong correlation between the observed structural damages, PSI data and the pre-existing landslide maps highlighted the need of updating the inventory, redefining the boundaries of the landslide which actually threatens the preservation of the historical building.
Besides their suitability for multi-temporal and spatial deformation analysis, the Synthetic Aperture Radar (SAR) image archives acquired by space-borne radar sensors can be exploited to support archaeological investigations over huge sites, even those partially or totally buried and still to be excavated. Amplitude information is one of the main properties of SAR data from which it is possible to retrieve evidences of buried structures, using feature extraction and texture analysis. Multi-temporality allows the reconstruction of past and recent evolution of both landscape and built-up environment, with the possibility to detect natural and/or anthropogenic changes, including human-induced damages to the conservation of cultural heritage. We present the methodology and first results of the experiments currently undertaken using SAR data in the Nasca region (Southern Peru), where two important civilizations such as Paracas and Nasca developed and flourished from 4th century BC to the 6th century AD. The study areas include a wide spectrum of archaeological and environmental elements to be preserved, among which: the archaeological site of Cahuachi and its surroundings, considered the largest adobe Ceremonial Centre in the World; the Nasca lines and geoglyphs in the areas of Palpa, Atarco and Nasca; the ancient networks of aqueducts and drainage galleries in the Puquios area, built by Nasca in the 1st-6th centuries AD. Archaeological prospection and multi-purpose remote sensing activities are currently carried out in the framework of the Italian mission of heritage Conservation and Archaeogeophysics (ITACA), with the direct involvement of researchers from the Institute for Archaeological and Monumental Heritage and the Institute of Methodologies for Environmental Analysis, Italian National Research Council. In this context, C- and L-band SAR images covering the Nasca region since 2001 were identified for the purposes of this research and, in particular, the following data stacks were selected: ERS-2 ascending data acquired in 2001-2011, ENVISAT ASAR ascending and descending data acquired in 2003-2007, and ALOS PALSAR descending and ascending data acquired in 2007 and 2008. The feature extraction was specifically addressed to the recognition of buried structures, archaeological deposits and the study of the buried networks of aqueducts, as well as the morphological study of the Nasca geoglyphs. Change detection analysis also included the multi-temporal reconstruction of the evolution of the Rio Nasca catchment basin, while specific tests were performed to demonstrate the usefulness of SAR imagery for monitoring looting activities. The results of the radar-interpretation compared and integrated with the field investigations will support the archaeological activities and contribute to the monitoring and enhancement of archaeological heritage and cultural landscape of the Nasca region.
This report describes a detailed scheme for the mapping and recording of artificial ground. It presents codes and descriptions that underpin the entries in the British Geological Survey stratigraphical lexicon
This report forms part of the Prehistoric Pottery Project, which is aimed at investigating by means of petrographic and electron microprobe analyses the production and distribution of later prehistoric granodiorite-tempered pottery from the East Midlands. Earlier petrographic studies have identified potential production sources in rocks cropping out in the Mountsorrel area of Charnwood Forest (Knight et al., 2003) and it is intended to test this hypothesis by the application of electron microprobe analyses, combined with additional thin section petrography. This is envisaged as the first stage of a 2-phase project, which in the second stage will examine the potential of isotope analysis for refining our knowledge of sources of potting clays and temper.
This report details the reasoning and methodology for the introduction of a revised computer-coding scheme for unlithified deposits, commonly also referred to as superficial deposits, unconsolidated deposits or engineering soils. These include clay, silt, sand, gravel, cobbles, boulders and peat plus all the combinations of these deposits. The report describes the former BGS system for coding such deposits and details a logical system for coding many hundreds of lithological mixtures by the simple use of up to seven letters in various combinations. The scheme is designed to be universal in its application and usable for historical and modern geological information including field data capture. It is not a classification scheme, but a coding scheme, furthermore it is not intended as a replacement for a full lithological description. The report details the implications on this coding scheme of using BS5930 and the AGS (Association of Geotechnical and Geoenvironmental Specialists) borehole recording classifications. It also details how the coding scheme can be applied to other classification schemes including IMAU (Industrial Mineral Assessment Unit) and material recorded by offshore and coastal studies.The report presents an abridged listing of the proposed codes based on the most commonly encountered combinations and the lithological ornament fields currently used in AGS borehole packages.The report also lists a much simplified set of codes for colouring borehole sections and maps using GIS and borehole viewing software where it is desirable to have the detail in the borehole logs, but generalisation is needed for correlation and presentation.
McManus, Kay B.; Donoghue, D.N.M.; Marsh, S.; Brooke, C.;
McManus, Kay B.; Donoghue, D.N.M.; Marsh, S.; Brooke, C.;
Country: United Kingdom
Shallow ground disturbance creates a differential heat flux in the soil column due to a variation in the thermal properties between disturbed and undisturbed soils. When we observe above a canopy, the effect of vegetation growth on the thermal regime of the underlying soils is poorly understood. This paper discusses the potential of airborne thermal prospection, using the response measured by the NERC Airborne Thematic Mapper (ATM) at thermal infrared wavelengths, for detecting shallow ground disturbance where features are known to exist under variable vegetation over archaeology at Bosworth, Leicestershire and over abandoned mine shafts on Baildon Moor, W. Yorkshire. The investigation focuses on qualitative image interpretation techniques, where anomalies on day and night thermal images are compared with those manifest on the multispectral images, and a more quantitative approach of Apparent Thermal Inertia (ATI) modelling. ATI modelling examines the diurnal temperature contrast of the surface, determined from images acquired when the surface exhibits its maximum and minimum temperature, to identify volumetric variations in the soil column potentially relating to buried features. Ground temperature profiling at the Bosworth site indicated that diurnal heat dissipates between 0.20-0.50m at an early stage in vegetation development with progressively lower diurnal amplitudes observed at 0.20m as the vegetation develops. These results emphasise the importance for selecting the optimum times for thermal image acquisition of vegetated surfaces. Extensive ground geophysical prospection and soil sampling were also performed at the Bosworth site to compare the physical soil properties with the anomalies observed from the diurnal thermal, seasonal thermal and ATI response. Results suggest that there is a high correlation (R²=0.98) between ATI and soil moisture properties at shallow depths during both early and late stages in cereal crop development, at 0.15-0.25m and 0.10-0.30m respectively. The high correlation between physical ground disturbance and the thermal response is also corroborated qualitatively with the results of resistivity surveys conducted over the Baildon Moor study site. These results suggest that ATI modelling can provide an indication of physical variations occurring at shallow depths in the soil column, even when a layer of vegetation covers the surface.
This report describes the occurrence, extraction and natural hazards related to Triassic gypsum in the Chellaston and Aston-on-Trent areas, south of Derby. A brief historical review of gypsum working from the Middle Ages onward is given. The stratigraphy of the gypsum and Cropwell Bishop Formation in the Mercia Mudstone Group is described. Details of the mines and quarries in the area are presented along with notes about their geology. Geological hazards, related to gypsum workings and natural gypsum dissolution, are noted. This work was undertaken as part of the BGS project to revise the Loughborough Geological Map (Sheet No. 141).