M. Járó - L. Költő szerk.: Archaeometrical research in Hungary (Budapest, 1988)

Prospecting - SŐRÉS László: Geophysical measurements at the site of a Roman homestead at Balácapuszta

SÖRES László * GEOPHYSICAL MEASUREMENTS AT THE SITE OF A ROMAN HOMESTEAD AT BALÁCAPUSZTA Abstract - In 1984 and 1986 direct current dipole-dipole and electromagnetic Slingram measurements were performed in the area of a one-time Roman homestead. The resistivity and the conductivity maps show very good correlation. The anomalies suggest the presence of previously unknown buried ruins. After filtering the direct current profiles the exact site and direction of the walls could be determined. The appendix deals with the planning of the filter and the most important filtering characteristics. Introduction Archaelogocial excavations had already been performed in the area of Balácapuszta lying 8 km south-west of Veszprém, at the beginning of this centjiry. These excavations were aimed at determining the site plan of the buildings belonging to the Roman homestead existing between the 1st and 4th centuries A.D. Detailed excavation of the area was started in 1972, during which very valuable finds came to light. The mosaic floor and the frescoes found in the central building, which has since been reconstructed, undoubtedly prove that archaelogocial excavation gives hopes of very rich results. In order to facilitate the excavations, reconnaissance geophysical research was started, at the request of the Bakony Museum of Veszprém. The aim of the measurements was to localize the buried ruins lying scattered over an area of 16 hectares. Two physically different methods were applied. One was direct current mapping of the dipole-dipole system; the other was electromagnetic Slingram mapping. A Dipair10R type instrument (ELGI, Hungary) and an EM-31 type instrument (Geonics) were used for the measurements. The simultaneous application of measurements of different physical principles enables one to reduce the uncertainties. For example in the case of the direct current measurements, the effect of the highly resistive parts dominates in the electric response, while the electromagnetic method is sensitive to low resistivities, i.e. to highly conductive bodies. Thus, in the two cases the resulting pictures of the area are basically the same, but different in the details. Geophysical measurements and model calculations The research was limited to an area of about 100 x 60 m in the SE foreground of the reconstructed central building. A resistivity map of the area was made from the direct current measurements. From the electromagnetic measurements a conductivity map was constructed. The two parameters can be considered as reciprocals of each other; where one shows a maximum, the other must be a minimum (Fig.l). * Eötvös Loránd Geophysical Institute of Hungary, H-1440 Budapest, P.O.B. 35