Abstract
Summary: The Silver Pit, in the south-western North Sea, is shown to be a closed trench-like depression cut through till of Weichselian age. Its deeper southern part penetrates marine interglacial deposits below the till. The floor of the pit is probably of Chalk partly covered by Recent sediments. Other trench-like features (Sole Pit, Coal Pit, Well Hole) are described briefly and thought to be sufficiently similar to Silver Pit to imply a similar origin. Two hypotheses of origin of these closed depressions are considered: by subglacial stream erosion (tunnel valleys) and by tidal scour during an early post-glacial low sea level. Neither hypothesis appears to be wholly satisfactory by itself, and the possibility of a composite origin is mentioned.

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