Nordre Etnedal. Beskrivelse til det geologiske gradteigskart
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Cambrian and Ordovician formations: Apart from the Synnfjell Sandstone, the rocks in the southern part of the area consist of marine deposits of Cambrian and Ordovician age, forming an extension of the corresponding deposits in the Oslo area with some change in facies to less of calcareous and more of coarsely clastic material. The Cambrian deposits can be divided into two distinct divisions, a lower one of grey, green or red shales and slates, sandy shales or sandstones (pl. 2, fig. 1), and an upper one of dark bituminous alum shales with nodules of dark stinkstone. In the alum shale division fossils of the Olenus and Paradoxides beds (listed on p. 16) have been found in the area W of Lake Steinsetfjord. The alum shales are thus manifestly of Middle and Upper Cambrian age, the underlying division of least partially Lower Cambrian. At the boundary of the overlying Phyllite Division the Brachiopod Archæorthis christianiæ, an index fossil of Ceratopyge beds (Tremadoc of Britain), has been found at two localities, also Dictyonema flabelliforms is reported from the area. Petrographically the Ceratopyge beds are so similar to the Cambrian deposits to be included with them in the map. The Phyllite Division is a very monotonous sequence of grey and partly dark fissile phyllites.