Engervik Member
(Engervikleddet)
(New name)
(Previously termed: 4a-α-3 Ogygiocarisskifer, Ogygia Shale, Ogygiocaris Shale).
Main Lithologies. Grey shale with limestone horizons.
Basal Stratotype. Oslo-Asker: North of Engervik (Fig. 12) (NM 845 306).
Definition. The base of the Engervik Member is taken at the first continuous limestone bed which at the type locality succeeds 18.5m of black shale with scattered ellipsoidal limestone nodules of the underlying Sjøstrand Member. The Engervik Member consists of black shales with isolated nodules and continuous limestone beds commonly 5-10 cm thick. Above 8.8m above the base in the type section, the trace fossil Chondrites is abundant. The Engervik section is the only one known to contain the base and top of the Engervik Member without obvious tectonic disturbance. However, the measured thickness of 15.5m Should be viewed as no more than an approximation for the thickness of the member as at least three slickensided calcite sheets are present parallel to the bedding (Fig. 12).
Fauna and Age. The shelly fauna of the Engervik Member is more diverse than that of the underlying unit. The fauna includes trinucleid Størmer 1930, Owen 1987) asaphid (Henningsmoen 1960) telephinid (Nikolaisen 1963) and remopleuridid (Nikolaisen 1983) trilobites as well as brachiopods (Spjeldnæs 1957) and cephalopods (Sweet 1958). Amongst the trilobites, Botrioides bronnii (Boeck) appears in the member and ranges up into the lowest part of the Vollen Formation (Owen 1987, p.82). This species also occurs in the Lower Dicellograptus Shale (including the Killeröd Formation) in Skåne S.E. Sweden which broadly equates with the G. teretiusculus graptolite Zone. Berry described the graptolites of the Engervik Member and concluded (1964 p.78) that the Didymograptus murchisoni -Glyptograptus teretiusculus Zone boundary lies within the unit.
(From Owen et al., 1990: The Ordovician Successions of the Oslo Region, Norway. NGU Special Publication 4. Figs. refer to the printed version.