Abstract

"Comparison of streaked-out 'ripples' formed by the drag effects of a current passing over a watery, yet cohesive sediment bottom with convoluted laminae formed within beds of fine-grained sandstone suggests a common origin. Application of Bagnold's recent discoveries on the behaviour of cohesionless sediment in flowing fluids to the problem results in a modification of Kuenen's hypothesis of origin of the convolutions. According to the new interpretation, convolutions arise when formerly cohesionless sand grains become cohesive after deposition and respond to increased shearing due to higher current velocity by a decollement-type of adjustment with the plane or planes of adjustment located within, or in some cases at or below the base of the growing sandstone bed."

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