Noen stratigrafiske aldersspørsmål i Grong-feltet og den sydøstlige del av Helgeland.
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Some years ago the present writer described the geology and stratigraphy of the district along the Swedish border between 64 50' and 60 45' N (Strand 1953, 1955, Foslie og Strand 1956). In these districts and in adjacent districts on the Swedish side of the border a quartizite or a quartz conglomerate and an overlying limestone form a marker horizon in the stratigraphy. Swedish geologists had correlated the quartzite-llimestone horizon with the Vojtja conglomerate and the Sl\u00CCttdal limestone described by O. Kulling from a part of V\u00CCsterbotten, Sweden. The Sl\u00CCttdal limestone is known to be of youngest Ordovician age on the evidence of well determinable fossils. The pesent writer accepted this correlation in the above-mentioned papers. In the Norwegian districts in question the Liming group of arkoses, conglomerates and other rocks are evidently the youngest deposits. It now seems to the writer that there is good reason to correlate the Liming group with the Volla conglomerate and Hovin sandstone in the Trondheim region and with the Gillik conglomerate in V\u00E4sterbotten. These deposits are known to be of middle or young Ordovician age, but certainly older than the Vojtja and Slåttdal. In the districts here in question the quartzite-limestone horizon is certainly older than the Liming group.