NS51C-01
Combined Geophysical Prospecting in Andalusia (Spain): Geomagnetics, GPR and IP Geoelectrics in Munigua, Montes de San Benito and Alcorrín.
According to the special tasks of archaeologists of the German Archaeological Institute (Madrid department) geophysical investigation campaigns were realized at several sites in Andalusia during the last five years. In Munigua (Province of Seville) - a Roman municipium and centre of metal production - building structures like the city wall and production sites extra muro were investigated by means of GPR measurements. A new method permitting virtual or physical reconstructions of archaeological features in the ground is presented using the original geophysical data and avoiding the speculative aspect of previous reconstruction techniques. In addition the Roman archaeo-metallurgical remains were surveyed in order to investigate the economic base of the Roman town and its environs. Geoelectrical measurements were realized recording the complex resistivity. The extension and depth of slag heaps are estimated using 2D and 3D images of resistivity ρ and phase angle φ. The slag heaps are well-defined by IP effects from the bedrock. The results allow estimating the amount of processed metal in Munigua for the first time. The main focus of the survey in Montes de San Benito (Province of Huelva) was the investigation of the structure of a Celtiberic settlement closely connected to iron production as well. Geomagnetic mapping and GPR measurements were applied in order to detect the buried building structures and the street system. Several single buildings, the main axes and remains of furnaces were localized. A similar procedure was chosen prospecting the fortified hill of Alcorrìn (Province of Malaga), a Phoenician settlement nearby the Mediterranean coast. The both spectacular and rarely researched site is surrounded by an up to 5 m thick wall. Main goal of the two survey campaigns was the internal structure of the hill fort. Using geomagnetic mapping and GPR a second fortification system could be identified. Inside the second ring wall building structures made of mud-brick and lime stone were investigated and proved by excavations. The three examples convincingly demonstrate the close cooperation between archaeologists and geophysicist in order to find effective ways to solve archaeological questions by means of geophysical prospecting methods even under challenging conditions. Matter of particular interest has been the search for visualization techniques meeting both scientific standards and ensuring best possible clearness.
NS51C-02
GPR and Magnetic Modeling on an Archaeological Site in Central Mexico
A geophysical study was carried out in an archaeological site called Los Teteles de Ocotitla, which means ‘bunch of rocks'. The area is located within the central portion of the Sierra de Ocotitla, towards the northeast of La Malinche volcano, in the municipality of Altzayanca, State of Tlaxcala. This site is conformed of several artificial terraces with evidence of human occupation, probably from the Teotihuacan or Tenanyecac phase. At first the presence of several hills, which are the remains of small pyramids can be seen. Also, some exposed walls and floors can be appreciated. The geophysical work included magnetic (vertical field) and GPR observations in five terraces. The magnetic data depicted a series of dipolar anomalies probably related to walls, and stairways. A report from a previous archaeological excavation carried out almost 30 years ago on an upper terrace, mentioned the discovery of an ancient burial. The tomb was a room (3x2x2 m3) to a depth of 1 m, where corpse remains were found, along other archaeological artifacts. Magnetic and GPR profiles were observed in this area to define geophysical signatures of the mentioned ancient structure, to later compare with anomalies obtained in other terraces. Two interesting anomalies were observed in two lower terraces that compared well with the signatures obtained. The magnetic anomalies were modeled employing a 3D inverse approach, assuming that the Earth is conformed of a series of magnetic dipoles. The final result produced a magnetic block of 5x3x3 m3 to a depth of 1.5 m, approximately. The GPR anomalies helped to constrain the initial geometry of the archaeological structure.
NS51C-03
Cliff stability assessment using electrical resistivity tomography at the historic WWII D-Day invasion site, Pointe du Hoc, France
The 1944 D-Day invasion site at Pointe du Hoc, Normandy, France is an important WWII battlefield and cultural resource but is at risk from chalk cliff collapse. The American Battle Monuments Commission tasked us to evaluate the geohazard to the observation post and other cliff-side buildings of historical significance. Geophysical multi-electrode resistivity profiling is used to study cliff stability and the condition of the observation- post foundations. Preliminary 2-D geological interpretations are provided of individual profiles. The copious steel, concrete and void spaces at the site renders hydrogeological interpretation challenging but tractable. The cliff face appears to be relatively intact and well-drained. Several routes taken by groundwater into fractures within the chalk were identified mainly on the western side of the site. The eastern side is drier and somewhat sheltered from the Atlantic storms but may contain large void spaces that could efficiently transmit groundwater flow during heavy precipitation events, thereby imperiling the major antiaircraft gun emplacement occupied by Col. Rudder in the early days of the Allied invasion. The forward German observation post perched close to the sea stack, which now hosts the U.S. Ranger memorial, may be moving with the soil and not securely anchored to bedrock. A complex failure mechanism is identified as a combination of groundwater dissolution of the fractured chalk and sea wave attack at the cliff base.
NS51C-04
Geophysical and Rock Magnetic Survey of Archaeological Soils in the Urban and Ceremonial Center of La Campana in Western Mesoamerica
Results of an integrated geophysical and rock magnetic study of archaeological soils from La Campana in western Mesoamerica are presented. La Campana is located in the northern suburbs of the city of Colima over a terrain characterized by volcanic debris avalanche deposits and palaeosols. Our study area of about 12,600 m2 is divided into two sections corresponding to the main archaeological site and to potential extensions north of it. We report results of soil magnetism on 6 vertical profiles in the archaeological excavations, and from a grid of surface sampling in the unexcavated northern area. In the main sector, excavations have uncovered three large structures made mainly of rounded volcanic boulders and built over large platforms. Geophysical anomalies and rock magnetic data provide information on landscape change and susceptibility enhancement in the archaeological soils. Archaeological remains extend over an area, considerably larger than that excavated in the archaeological survey, which is manifested in susceptibility enhancement in the top soils. The characteristics and size of the pyramidal structures, the plazas and channel network and the apparent overall extension of the archaeological site confirm that La Campana constituted a major urban and ceremonial center in westernmost Mesoamerica.
NS51C-05
Combined Survey Format (CSF) Archaeogeophysical (Metal Detecting, Radiometrics and Resistivity) and Archaeochemical (XRF) Investigations of the 19th Century La Hacienda Y Presidio of Babocomari Military Site in Arizona
Recent archaeological investigations of Historic Era Mexican and Anglo-American and Prehistoric and
Protohistoric Hohokam and Sobaipuri culture sites on the Babacomari Land Grant near Sierra Vista Arizona by
Carothers Environmental, LLC (CE), Wondjina Research Institute (WRI) and DMG Four Corners Research (FCR)
led to the discovery of two major 19th Century military sites that were known from the literature but had not been
scientifically investigated.
It was decided by WRI and BABACOMARI RANCH that this project was ideal for an experimental cooperative
training program for archaeologists and geologists from the anthropology and geology departments of UA, ASU,
NAU, PC, and members of AAS, AAHS, AAC, THS and USFS personnel in the use of the new CSF
archaeogeophysical, archaeochemical and airbourne remote sensing technologies and field techniques that
have just been recently introduced in the US. WRI, CE and Statistical Research Inc. (SRI) conducted CSF VLF
Metal Detecting, Radiometrics and Resistivity studies and portable X-Ray Fluorescence (XRF) archaeochemical
studies. The results will be presented along with suggestions as to use of these technologies in CSF studies.
http:www.babacomariranch.com
NS51C-06
Georadar Archaeological Prospection at the Historical Center of the Merida City, Yucatan, Mexico.
This paper shows the results of the georadar archaeological prospection carried out by the Laboratorio de
Prospección Arqueologica from the Instituto de Investigaciones Antropologicas (IIA) of the Universidad Nacional
Autonoma de Mexico (UNAM) verifing the archaeological and historical information recovered by the
Departamento de Patrimonio Arqueologico y Natural del Municipio (DPANM) del Ayuntamiento de Merida en el
Centro Histerico de la Ciudad de Merida under a joint project. The Historical Center of Merida has been classified
as a "zone of high patrimonial value" after the topographic data and the historical documents recovered showed
a long-term occupation, non interrupted since pre-Columbian times, when T Ho was the great capital of the
northern region of the Maya area. For the rehabilitation program of the Historical Center of Merida has been a
great priority to verify the existence of archaeological remains, pre-Columbian or colonial, under the present
streets, gardens and plazas that could be damaged during the public infrastructure works. In order to prevent any
damage to the patrimony a large georadar study was carried out pulling 200 and 400 MHz antennas of the GSSI
SIR System 2 for 16500 m of the city streets, focusing in the areas where infrastructure works were imminent.
After the analysis of the radar data it was possible to build up a map with the location of the most noticeable
archaeological remains under the pavement of the streets that confirmed many of the topographic and
documental proposed places. As a final result, by the first time a city government has available information to take
present urban decisions, while preventing the damage to the archaeological patrimony of the same city.
http:swadesh.unam.mx/laboratorios/prospArqueologica.html
NS51C-07
Archaeomagnetic Investigation at Chapultepec, Mexico City: Case Study of Classical Settlers
During the restoration campaign at the Chapultepec Park in Mexico City downtown, a teotihuacan settlement was found at the south flank of Chapultepec Hill. Samples represent a kind of irregular home kilns with a hole in their central part bounded by andesite rocks. Alternating field demagnetization had been employed. Rock magnetic measurements which included: Hysteresis, continuous susceptibility and isothermal remanence experiments revealed that some spinels, most probably magnetite or Ti-poor Titanomagnetites are responsible for the remanence. An archeomagnetic date obtained here is of 525 AD which is in good agreement with other evidences of the Teotihuacan Classic Metepec period (450-600 AD).
NS51C-08
Geophysical Investigations Over the Archaeological site of Rirha (Morocco)
The roman site of Rirha has been evidenced in the 1920's and loosely studied until nowadays. Archeaological evidences show a pre-roman to medieval occupation of the site. Excavations have revealed thermae and other buildings while their context, rural villa or urban domus was still unknown. A new survey began in 2004, focusing on the pre-roman occupation of the site, as well as the characterization of the roman occupation. The zone of interest, a hill in a river loop, is about 11hectares. A comprehensive geophysical survey was out of reach, so geophysical tests have been carried on with two goals. The first one was to identify the suitable methods adapted to this, the second one was to use these preliminary results to distinguish between rural or urban settings for the roman site. The first survey has been conducted in April 2005, using conductivitymeter (Geonics EM38) in order to get informations about the spatial organization of the site. The selected zone was located in an unsurveyed part of the site. Resistivity maps show orthogonal structures, far from the known roman remains. This result supports the hypothesis of the site being a roman town and not a large farm or a villa. The second survey has been carried on in February 2006 and involved GPR and DC tomography, in very wet conditions. DC survey aimed at constraining the geological context of the site and at finding the remains of a large wall described by early authors. GPR experiment was primarily a test of the tool there and has been conducted on the previously studied area to get some depth information. The geological context has been studied by carrying on a 2D vertical section, 330 m long and 25 meters deep. showing a substratum of river deposit (sand, gravel, pebbles with possible clay layers) located at 8 to 10 m deep. Above this formation, we observe a very conductive layer interpreted as a clay formation (3 to 6 m thick) and finally, just below the surface, a laterally heterogeneous formation with rocks and adobe masonry. 2D DC sections succesfully located the remains of the surrounding wall of the site supporting even more the town hypothesis. GPR 3D results (250 MHz) are in agreement with conductivity maps but are of poor quality due to the very low resistivity of the soil.
NS51C-09
Electrical Resistivity and Archaeology Near Barrow, Alaska
A capacitively coupled resistivity survey was conducted on an archaeological site near Barrow, Alaska in June of 2006. The purpose of this survey was to determine the effectiveness of resistivity studies in determining locations of near-surface burials and other features of interest. This survey was performed on an area 14mx160m, with line spacings of 1 meter. Data was acquired at 6 depths with the nearest to the surface being obtained with an unusually-short n-spacing of (n/4). This allowed for visualization of subsurface features as small as ~20cm, and at depths as shallow as ~20cm. The greatest depths seen were ~2m below the surface. The data was processed in a preliminary fashion during the course of the survey and several near-surface features were seen that were consistent with burials. Upon inspection, the surface vegetation and small-scale topography were visually consistent with burials. An archaeological team dug pits in three of these areas and all three were determined to be burial sites. 3-D inversion processing was carried out after the field season. Comparisons with archaeological field data indicate that all graves encountered in that portion of the survey area tested corresponded to anomalies on the 3-D images.