The Rhuddanian to middle Aeronian Solvik Formation is a generally prograding sequence deposited on a storm-dominated shelf. Strata in the Asker and Holmestrand districts were deposited more proximal to western source areas than strata deposited in the Oslo District. Two small deepening events recorded in the proximal areas can be correlated with global sea-level changes in early and mid-Aeronian times. The base and top of the formation are only slightly diachronous, while considerable diachronism occurs laterally between the members. A hypostratotype of the Solvik Formation is proposed and two members, the Spirodden Member and the Leangen Member, are defined in the Asker District.