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3D Resistivity Interpretation of Helicopter-borne Frequency-domain EM (HEM) Data from Ramså Basin and Around in Andøya,Normal access

Authors: V.C. Baranwal, E. Dalsegg, H. Elvebakk, J.-S. Rønning and Norwegian University of Science and Technology and M. Brönner and Norwegian University of Science and Technology
Event name: Second European Airborne Electromagnetics Conference
Session: Data Visualization, Integration and Interpretation
Publication date: 03 September 2017
DOI: 10.3997/2214-4609.201702169
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 1.39Mb )
Price: € 20

Summary:
The Ramså Basin on Andøya, Northern Norway is the only known Mesozoic basin onshore Norway. The primary basement rocks in the area are granodiorite. The Mesozoic sedimentary strata of the Ramså basin comprise sandstones and different clay stones of Cretaceous and Jurassic ages. Resistivity of the subsurface can be investigated by electric and electromagnetic (EM) geophysical methods to delineate the extension of the Ramså basin. Borehole logging, electrical resistivity tomography (ERT) and helicopter-borne frequency-domain EM (HEM) surveys were performed in the area in the frame of different projects to gain a better understanding of the basin geology and structural settings. A quasi-3D inversion of HEM data shows a good agreement with borehole resistivity and ERT resistivity. HEM interpretation presents a 3D subsurface resistivity image of a larger area in comparison to what could have been drawn from few ERT lines and borehole logging. HEM interpretation together with other ERT and borehole resistivity indicates extension of Ramså basin boundary beyond presently mapped boundary. Two new highly conductive areas are identified by HEM data interpretation and one of the areas is confirmed with presence of graphite and sulfide minerals by geological observations.


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