STEINVIKA FORMATION
(Steinvikformasjonen)
(Harland 1980)
(Previously termed: 4e, 4b-γ, Encrinitenkalk, Encrinite Limestone)
Main Lithology. Limestone (Steinvika Limestone, Steinvikkalken)
Basal Stratotype. Skien-Langesund: Steinvika (Harland 1980 Fig. 4) (NL 429 397).
Hypostratotype. Eiker-Sandsvær Lindset (NM 355 021).
Definition. The Steinvika Formation is a limestone unit comprising a variety of lithofacies (Harland 1980, 1981). Its base is slightly transitional but marks a change from the pale limestones, sandstones and shales of the Fossum Formation to dark, thickly bedded bioclastic limestones. The top is an abrupt change from pale limestones and mudstones to the dark shales of the Venstøp Formation.
Harland (1981) recognised 13 different lithofacies within the Steinvika Formation representing environments from intertidal to well circulated shelf. He subdivided the formation into four members (see below and Fig. 18 herein), the formation as a whole being 41.4m thick in its type development. The formation in Eiker-Sandsvær is too poorly known at present for any formal subdivision or estimate of thickness to be made.
Fauna and Age. The Steinvika Formation is richly fossiliferous at some horizons and contains local bioherms of calcareous algae, stromatoporoids and corals (Harland 1980, 1981, 1981a). As noted by Harland (1980 p.277) the occurrence of the trilobite Toxochasmpos extensus (Boeck) suggests a correlation with the upper Caradoc units elsewhere in the Oslo Region.
(From Owen et al., 1990: The Ordovician Successions of the Oslo Region, Norway. NGU Special Publication 4. Figs. refer to the printed version.