Anomalous scallop distributions in Joint Hole, Chapel-le-Dale, North Yorkshire, UK

Observations and subsequent measurements made by cave divers in the Joint Hole active phreatic conduit have revealed two distinct and adjacent scallop distributions. Analysis using well established hydraulic equations show that the scallops are indicative of very different sub-critical, turbulent flow regimes. That derived for scallops observed on the floor of the passage agrees with evidence gained from previous studies of the sediment populations (Murphy, 1999). No over-printing of scallop signatures either on the roof or floor is observed, suggesting that another (as yet unknown) mechanism may give rise to the preferential enlargement of erosional features on the roof of the passage. This study illustrates the importance of direct observations and measurements made by cave divers.