Sedimentological studies of the Eller Beck bed and the Lower Deltaic series in north-east Yorkshire

Abstract

In this study of the Lower Deltaic Series emphasis has been placed on the field relationships of the various lithofacies types and their correlation with the observed facies of the present day deltaic environment. Deposits representing channel, levee, and interdistributary marsh environments have been recognised. The delta is thought to have advanced very rapidly across a surface of Dogger sediments which were near of even about sea level. Three cycles of channelling are believed to be related to phases of uplift in the hinterland. Analysis of directional data indicates transport from the north and west in the west and from the north and east in the east. This pattern probably reflects the local distribution of main distributaries to the east and west, while the ultimate source is believed to have been a Scandinavian landmass. The Eller Beck Bed transgression spread from the south-east, along an E.S.E. – W.N.W. axis of maximum subsidence. The fauna indicates that fully marine conditions prevailed during deposition of the basal ironstone and of the lower part of the shale. Upward passage from shale into sandstone appears to represent gradual readvance of the delta, culminating on the colonisation of the top of the sandstone by plants. Subsidence along the trough axis appears to have produced a clastic trap, so that to the south much of the sandstone is represented by shale. Upstanding sand-banks developed in the shale unit provided local environments suitable for the formation of chamosite coliths. The coliths from the Winter Gill ironstone indicate formation under very gentle current conditions. The petrography of the sediments has been studies with emphasis on the iron-rich types. Grain-size analysis has been carried out and the results interpreted in terms of the hydrodynamic environment of deposition.