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The Holmestrand Formation of Turner (1974a) is exposed on both the east (Jeløya) and west coast of outer Oslofjorden in the Holmestrand district. Turner defined the type section of the formation between Engenes and Smørstein (NL723999) in the Holmestrand area. An approximately 600 m thick sequence is dominated by medium‑grained sandstones with extraformational conglomerate clasts, a development which Turner & Whitaker (1976) contrasted with the red beds seen in the Ringerike district. They suggested deposition of the Holmestrand Formation's sandstones by braided streams draining westwards, citing clast composition and sandstone mineralogy as suggesting the erosion of Precambrian basement complexes to the east of the Oslo graben. This interpretation contrasts with the results of other workers (F. Andreasen pers. comm. 1978) which suggest deposition of the Holmestrand Formation on coastal floodplains with palaeoccurrents from the northwest. An explanation of these conflicting views is suggested by recent studies of the junction between the Ringerike and Asker Groups (Olaussen 1981a); these indicate that some of the red beds assigned by Turner & Whitaker to the Holmestrand Formation may in fact be Carboniferous in age. More detailed work is clearly necessary; and studies of the metamorphosed 300 m‑thick sequence generally assigned to the Ringerike Group in Eiker and Skien are also needed before reliable palaeogeographical interpretations can be presented.