Helicopter-borne magnetic and radiometric geophysical survey at Kviteseid, Nissedal, Fyresdal and Dalen, Telemark county
NGU conducted an airborne magnetic and radiometric survey at Kviteseid, Nissedal, Fyresdal and Dalen, Telemark county in June 2015 as a part of the MINS project (Mineral resources in Southern Norway). This report describes and documents the acquisition, processing and isualization of recorded datasets. The geophysical survey results reported herein are approximately 7340 line km, covering an area of approximately 1468 km2.
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.
Action map for tunnel planning, Oslofjord - Telemark region: Mapping deeply weathered weakness zones
Joints and fractures were weathered during a sub-tropical climate regime and thus may contain smectite and kaolinite. The presence of such minerals prohibits groundwater flow in fracture and fault zones. The clay-bearing zones may cause mechanical problems during both tunnel construction and later operation. Due to the chemical alteration of magnetic minerals during weathering, weak zones are characterized by negative magnetic anomalies.
The purpose of this report is to present the available data regarding the graphitic schists in the Gjerstad-Kragerø area and to make the data available for explorers and municipal land use planners. The graphite schists that occur southeast of Lake Vegard in the Gjerstad, Kragerø and Tvedestrand area have an average content of graphitic carbon of 2.77 %. Rocks from the abandoned Bjørnås mine have contents up to 33 %.