Abandonment Facies of high-constructive Lobate Deltas, with an example from the Yoredale Series

Abstract

In high-constructive lobate deltas, the destructive phase of sedimentation which follows abandonment of the lobe, produces a thin, but distinct, stratigraphic marker horizon of variable facies, here termed Abandonment Facies. This horizon terminates the progradational sequences. In Recent deltas, the Facies in the proximal part of the abandonment lobe consist of a laterally persistent peat band, whilst distally thin sheet sands and fossiliferous lithologies occur. A similar facies pattern has been recognised in a Yoredale cyclothem. The model provides an explanation for localised marine bands and demonstrates a relationship between certain coal horizons and marine bands. The Abandonment Facies are also significant in determining delta type, history and palaeogeography.