Results from Marine geological investigations outside Forsmark

A detailed marine geological survey was conducted in a 10 km2 large area outside Forsmark comprising hydro acoustic, 100 m spacing between survey lines, and groundtruthing. These data, together with reanalyzed survey data retrieved in 2002 from the same area, were used to produce maps of seabed and underlying bedrock surface morphology as well as horizontal and vertical extension of sediments. An esker is discovered running approximately in a north northwesterly-south southeasterly direction in the area, which may be causing submarine groundwater discharge. Pockmarks, which are caused by sediment gas of thermogenic and/or microbial origin, are detected in the area. In addition to the original commissioned survey, bedrock surface and seabed morphology as well as horizontal and vertical extension of sediments in a larger adjacent area were reanalyzed and produced from survey lines retrieved during a commission by SKB in 2002 and during SGUs regular mapping program in 2002, 2008 and 2009.