Magnetic and radiometric helicopter measurements in Nissedal area, Telemark

Abstract

NGU conducted an airborne magnetic and radiometric survey in the Nissedal area in July 2011 on behalf of the Region Geologist in Buskerud, Telemark and Vestfold; Sven Dahlgren. This report describes and documents the acquisition, processing and visualization of recorded atasets. The geophysical survey results reported herein covers 525 line km, an area of 105 km2.A Scintrex CS-2 magnetometer in a towed bird and a 1024 channels RSX-5 spectrometer installed under the helicopter belly was used for data acquisition.The survey was flown with 200 m line spacing, line direction 90o (E to W) and average speed of about 115 km\/h. The average terrain clearance was 47 m for the bird and 80 m for the spectrometer. Collected data were processed at NGU using Geosoft Oasis Montaj software. Raw total magnetic field data were corrected for diurnal variation and levelled using standard micro-levelling algorithm.Radiometric data were processed using standard procedures recommended by International Atomic Energy Association. Data were gridded with the cell size of 50 x 50 m and presented as a shaded relief maps at the scale of 1:50.000.