EVIDENCE OF BIDIRECTIONAL ICE FLOW FROM DRUMLIN MORPHOMETRY AND TILL FABRIC ANALYSIS: A CASE STUDY FROM THE NEW YORK DRUMLIN FIELD

Previous work in the New York State drumlin field has suggested drumlin formation via deformation of subglacial sediment. We reconstructed regional Laurentide Ice Sheet flow direction using till fabric analysis to test this hypothesis. Till fabric analyses were carried out in both central and western New York to compare direction of subglacial deformation to ice flow direction derived from drumlin morphometry. Each site was located within an outcrop along a section of a drumlin thereby allowing in situ measurement of clast orientation within undisturbed till. Several sites were analyzed at each location and compiled to provide an overall representation of clast orientation. The measurements made in central New York indicate a north-south orientation while the western New York site indicates a northeast-southwest orientation. These directions overlap with drumlin long-axis orientations, and thus reinforce the hypothesis of drumlin genesis by subglacial deformation.