Characteristics and origins of lee‐side stratification sequences in late pleistocene drumlins, northern Ireland

Spindle‐ and parabolic‐shaped drumlins examined at fifty‐five localities in northern Ireland possess stratification sequences on their lee‐side flanks. These forms lack the distinctive steep stoss‐ and tapering lee‐ends of classical drumlins and tend to occur in linear zones transverse to late Pleistocene ice‐flow. In most cases (90 per cent) the stratified deposits infill embayments excavated in the lee‐side of barkhanoid forms and, in the remainder (10 per cent), they are superimposed on the lee‐side of whaleback forms. The stratification sequences developed as a result of sedimentation in interconnected subglacial water‐filled cavities and are unlike remanie proglacial sediments moulded by ice into drumlin form. Stratigraphic evidence indicates that the lee‐side sequences developed during drumlin streamlining, which supports the view that subglacial hydraulic processes played an important role in drumlin formation.