Björkö is a 10 km diameter structure probably of mid-Proterozoic age. It is characterised by an occurrence of Jotnian sandstone which is over 960 m thick The central part is located at the southern rise of the island Björkö. Detailed petrophysical, gravity, airborne magnetic, electromagnetic, gamma radiation, refraction and reflection seismic measurements have been performed as part of a systematic mapping and as a basis for an assessment of the structure for its geothermal energy potential.
Björkö energy
An information folder has been prepared (Björköstrukturen – en meteoritkrater, by Herbert Henkel)
References:
Flodén, T., Söderberg, P., and Wickman, F-E., 1993: Björkö – a possible middle Proterozoic impact structure west of Stockholm. Geologiska Föreningen i Stockholm Förhandlingar 115-1:25-38.
Henkel, H., Bergman, B., Stephansson, O., and Lindström, M., 2004: Björkö Energiprojekt – slutrapport avseende geovetenskapliga undersökningar 2000-2004. Kungliga Tekniska Högskolan TRITA-LWR.REPORT 3010, 61 pp.
Henkel, H., 1992: Geophysical aspects of meteorite impact craters in eroded shield environment, with special emphasis on electric resistivity. Tectonophysics 216: 63-89.