The Norwegian–Danish Basin: a dynamic setting for subsurface sand remobilization – established concepts on distribution and controlling factors

Abstract

Abstract The Norwegian–Danish Basin is characterized by a depositional environment governed by incised valleys, localized sand deposition and rapid progradation of thick sediment packages during the Paleogene and Neogene. Subsurface sand injectites occur at five locations, with distinctive geometries and injection styles. Such vary from short-distance injectites where injected dykes and sills are in direct contact with the parent sand, to a long-distance sand extrudite >1 km vertically above the proposed parent sand. These endmembers establish the Norwegian–Danish Basin as a dynamic environment for subsurface sand remobilization. Although formation models exist for the injectites at each of the five locations, general considerations of sand injection mechanisms in the Norwegian–Danish Basin remain untested. This study presents a synthesis of geometrical characteristics, sand injection style and controlling factors for sand injection in the Norwegian–Danish Basin. By reviewing the existing literature and including new data, the study qualitatively addresses the effects of parent-sand distribution on injection style at the five locations, the overpressure generating mechanisms and the importance of faulting as a trigger mechanism. The results show that short-distance injectites typically occur in areas with a confined parent sand and that salt-related faulting is locally important as a trigger mechanism for sand remobilization. The main overpressure generating mechanism is differential loading and lateral transfer of pressure. The case studies also show a trend between larger depocentres required for remobilization of more distal parent sands relative to the depocentre. The results confirm the prevailing consensus that local conditions related to parent sand distribution and burial depth partly control injection geometry and style.