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Geophysical prospection has been applied in the Hüttenberg area (Carinthia, Austria), where important parts of the Roman iron production in the province of Noricum between the first century bc and the fourth century ad are located. A combination of geomagnetic, geoelectric and electromagnetic measurements at different scales yielded information about the extent of the industrial complex and the location of yet undiscovered subsurface monuments in the surrounding area of the Semlach-Eisner archaeological site. The vertical and lateral extension of a slag deposit from the smelting activities could be determined by means of geomagnetic mapping and multi-electrode geoelectric profiles. For the prediction of the continuation of walls in the subsurface outside the excavated area, the total horizontal derivative of the magnetic anomaly as well as geoelectric measurements were most suitable, whereas electromagnetic measurements were not successful owing to the high conductivity of widely spread pieces of slag. Copyright © 2011 John Wiley & Sons, Ltd.

HUSSAIN, A., WALACH, G. and WEBER, F. 1981. Underground Gravity Survey in Alpine Regions, Geophysical Prospecting 29, 407-425. An underground gravity study was carried out under extreme conditions of the Alpine regions. The lead-zinc mine Bleiberg, Carinthia, was selected as an example to show the possibilities and limitations of the subsurface gravity method. For in situ density determinations, gravity measurements were made in two vertical mine shafts passing through Triassic sedimentary rocks of the Bleiberg Unit. The main pr blem in gravity data reduction in extremely rugged topography is the accurate calculation of the terrain effect on underground stations. A general discussion of the various corrections required for the gravity measurements in the mine is presented. The mean interval densities in the two shafts, in limestone, dolomite, and schists formations, were determined as 2.76 and 2.77 g/cm3, respectively, with an accuracy of better than 0.01 g/cm3 for a depth interval of 50 m. The interval densities provide valuable information about the lithological and structural changes in the shaft surroundings and also agree well with the representative hand sample densities.In the second part, the applications of subsurface horizontal gravity surveys in exploration are discussed. Since the influence of topography is less underground because of the greater distance to the surface, subsurface surveys have definite advantages over surface surveys and can be very helpful in locating anomalous density zones in the mines. An example of gravity survey with a station spacing of 10 m at a depth of about 540 m is presented.

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