Glacitectonic rafts and their role in the generation of Quaternary subglacial bedforms and deposits

Abstract Landforms and sediments on the palaeo–ice stream beds of central Alberta record glacitectonic raft production subsequent progressive disaggregation moulding, associated substrate ploughing, grooving. We identify a subglacial temporal or developmental hierarchy that begins with incipient rafts, including en échelon hill-hole complexes, pairs, strike-slip all which display patterns typical transcurrent fault activation pull apart. Many jigsaw puzzle–style fragmentation, indicative displacement along shallow décollement zones potentially related to patchy ice freeze-on. Their gradual fragmentation smoothing produces flow-transverse ridges (ribbed moraine), hill-groove paraxial ridge groove associations. Initiator scarp megafluting associations are dislodgement leading formation murdlins, crag-and-tails, stoss-and-lee type flutings drumlins, Type 1 hogsback flutings. Downflow modification rafts creates linear block trains (rubble stripes), megaflutings, horned rubble drumlinoids, diagnostic an immature footprint. Lateral margin migration ingests disaggregated thrust masses form ridged spindles, ladder-type morphologies, narrow ribbed terrain 2 flutings, assemblage shear moraine formation.