Bergevika Member
(Bergevikleddet)
(Opalinski & Harland 1981).
Main Lithologies. Mudstones, calcareous sandstones, limestone.
Basal Stratotype. Mjøsa (Nes-Hamar): Bergevika south (Opalinski & Harland, Fig. 9) (PN 101 364).
Definition. The Bergevika Member is restricted to Helgøya, (Nes-Hamar) where the only complete section is at Bergevika south and where the member is 35.45m thick. Its base marks the development of 8.6m of alternating mudstones and calcareous sandstones overlying the Furnesfjorden Member. The succeeding 21.25m is composed entirely of limestones with stromatoporoid 'reefs' up to 15m thick developed in the upper part (Opalinski & Harland 1981 pp.70-73; Harland 1981a pp.181-186; Webby 1979). The uppermost 5.6m of the member comprises thickly bedded dark micrites similar to those of the Gålås Member but lacking reticulate weathering.
Fauna and Flora. The lower part of the member contains bioclastic limestones rich in brachiopods and sparse, large, strophomenid brachiopods occur in the uppermost dark micrites. The 'reefs' of the central part of the Bergevika Member comprise a variety of facies with algae, stromatoporoids, corals and echinoderm fragments the most abundant fossils.
(From Owen et al., 1990: The Ordovician Successions of the Oslo Region, Norway. NGU Special Publication 4. Figs. refer to the printed version.