EVIDENCE, FROM MICROSTRUCTURES, OF DEFORMABLE BED CONDITIONS WITHIN DRUMLINS, CHIMNEY BLUFFS, NEW-YORK-STATE

Discussion on the process of drumlin formation has been ongoing for ov er a century. At present, two dominant schools of thought prevail, viz , formation by (a) subglacial hydraulic mechanisms, and (b) due to sub glacial sediment deformation. The latter mechanism depends on the exis tence of a subglacial deformable bed. Evidence from part of the large central New York drumlin field reveals evidence of syn-depositional de formation during the emplacement of diamictons that constitute the maj or portion of drumlins exposed along shore bluffs in Chimney Bluffs St ate Park. These diamictons cannot be lodgement till facies members but appear to comprise facies indicative of melange-style deposition unde r subglacial deformable bed conditions. The evidence obtained from mic rostructures and plasma fabric within these diamictons supports the ex istence of a deformable bed during diamicton emplacement. It is likely that formation of the drumlins occurred under these same subglacial b ed conditions.