A relationship between burial depth and sonic interval transit times has been established for normally compacted Upper Jurassic to Tertiary shale intervals from 32 carefully selected Norwegian Shelf wells located between the Danish-Norwegian sector border and 66°N. The normal shale interval transit time trend is expressed as ?= 191 exp( -0.00027z), where ? is the shale transit time (?s/ft) and z is burial depth in metres. During the late Cenozoic, mainland Norway and the eastern part of the Norwegian Shelf experienced uplift and erosion, which resulted in shale over-compaction. Twenty-nine wells were identified as being located within the uplifted area south of 66°N, and the established normal interval transit time trend was used to quantify magnitudes of net uplift and erosion from shale intervals in each well. The average standard deviation of the quantification was 260 m and the maximum magnitude of net uplift and erosion determined in the wells was 610 m. The late Cenozoic uplift binge-line is sub-parallel to the present-day Norwegian coastline, as are the iso-uplift curves whose magnitudes increase landwards. Compared to earlier studies, the magnitudes presented here differ slightly from those of other workers, probably because of the different methods employed.
Sven Hansen, Geologisk Institut, Aarhus Universitet, DK-8000 Århus C, Denmark.