Sedimentology of a glaciofluvial landsystem, Lough Ree area, Central Ireland: implications for ice margin characteristics during Devensian deglaciation

Abstract

Eskers in a glaciofluvial landsystem in the Lough Ree area, Central Ireland, exhibit two orientations. The most southerly esker in the area, the Athlone Esker, forms part of a dendritic esker system with paleocurrent directions indicating eastward drainage, while the Rooskagh Esker and associated eskers and kames immediately to the north were formed during southward drainage. Sediments indicate that sharp-crested, steep-sided sections of both ridges were formed within subglacial tunnels, while fan-shaped and flat-topped areas were formed as subaqueous outwash fans and deltas in standing water immediately in front of an ice-margin. The deposition of ice-marginal deposits indicating southward paleoflows against the side of the eastward flowing Athlone Esker indicates a 90° shift in the direction of ice surface slope, and a similar shift in the likely orientation of the ice margin. The absence of any evidence of intermediate ice- or water-flow directions indicates that the shift reflects a recession of ice, followed by a readvance from the north.