The Odbergrnoen area in lower Numedalen (Lågendalen) is an overdeepened glacial basin with approximately 200 m of Weichselian and Holocene sediments. The area was deglaciated approximately 10,500 yrs B.P. with a Marine Limit of 175 m a.s.l. Seismic refraction, vertical electrical sounding, and gravity
studies indicate the following stratigraphy: 60-110 m high-velocity sediments (till) are found below 60 m Late Weichselian and Holocene clays. 30m of fluvial/estuary sand cover the clay in the central part of the basin. When the area rose above sea-level (7000 B.P.), nearly 300 · 106m3 of sediments bad been deposited above the till. During the following 4000 years, the river eroded a 30 m deep channel, and approximately 63 · 106m3 sand, silt, and clay were transported southwards in the valley/fjord area.