Origins of the ice-contact stratified ridges (eskers) of Ireland

An extensive system of ridged landforms composed of ice-contact stratified sediment was deposited in the central lowland of Ireland during the most recent deglaciation (<18 000 BP). The ridges have been interpreted by others as deposits of an ice-sheet drainage system (i.e.' "eskers') and as such have been used with other data to reconstruct the deglacial history. The traditional deglaciation model shows systematic retreat of ice from south to north. We support a new model of deglaciation in which the "esker' system formed in an interlobate area during the simultaneous shrinking of two main glacial outflow centers. An extensive lake system developed in the lowland between the two outflow centers. Ice-contact ridges are polygenetic, and a genetic classification is proposed. Those that formed perpendicular to the ice margin are termed eskers; those that formed parallel are termed moraines. Distinction between esker types (continuous or beaded subglacial tunnel fills, fluvial ice-channel fills, and subaqueous fans) and moraine types (subaqueous or subaerial) is crucial to a reconstruction of the mode and pattern of deglaciation in the central Irish lowlands. -from Authors