The sandstone dyke swarm of Vang, Bornholm (Denmark)

Abstract

A very well exposed sandstone dyke swarm in the basement of Bornholm (Vang and Hammer granite) has been discovered recently north of Vang. It strikes 120° to 125° on average. Individual dykes are up to 23 cm thick. The fillings consist of pale, greyish to brownish, fine-grained to medium-grained quartz sandstone. It has a grain-supported structure, and the porespace is filled with argillaceous-limonitic material and carbonate (dolomite) cement. The opening and filling of the fissures were caused by normal extension movements in NNE-SSW direction in several steps, probably during the early Cambrian. The overlying Balka sands were implosively sucked down into the fissure vacuums caused by the sudden opening. The downwards moving of the water saturated sediments led to a loss of material above and to the creation of funnel structures. Tapering down ring structures in the Hardeberga sandstone at the east coast of Scania (Sweden) are interpreted as such funnel structures.