During the last decades several wells giving yields up to 100,000 1/h have been drilled in the reddish Brumunddal Sandstone, which covers an area of approximately 10 km2 near lake Mjøsa, Southern Norway.
Most of these wells have yields below 10,000 1/h, and those with higher yields are situated along prominent fracture zones. Textural data strongly support the assumption of an eolian origin for this sandstone, but water-deposited sediments are found within the formation.
Most of the grains are coated with a hematite pigment, which was probably epigenetically formed. Post-sedimentary but preglacial weathering processes have transformed plagioclase to montmorillonite. This has changed the porosity as well as the permeability and increased the cationic exchange capacity. A transformation of plagioclase is in agreement with the groundwater composition.