Abstract
ABSTRACT Downcurrent-dipping sets of cross-stratification occur in late Precambrian fluvial sandstones in northern Norway. The sets form cosets up to 4 m thick. The sets are wedge-shaped or lens-shaped, dip at <= 8° relative to the horizontal and have erosive boundaries. The geometry of the sets suggests that they were formed by the migration of large scale ripples over a bed which was wavy on a scale larger than that of the ripples. This wavy bedform was also moving downcurrent but at a slower rate than the ripples. It is estimated that the downstream faces of the wavy bedforms dipped at <= 11.5° and that the ripples moved at least 3.2 times as fast as the waves. The waves may be comparable with either the major mid-channel waves or the side bars of some modern streams.
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