Subglacial deformation associated with a rigid bed environment, Aberdaron, north Wales

At Aberdaron, north Wales, a complex sequence of homogeneous tills and fluvial sediments overlie a hard rock base. The lower diamicton association at the bottom of the sequence consists of deformed tills and lenses of stratified sediments. It is suggested that these represent deforming bed tills and subglacial fluvial units which have been deformed together by subglacial excavational deformation. The central part of the section is marked by undeformed fluvial sediments along an unconformity which has been folded in places into a series of antiforms. It is suggested that the fluvial sediments were deposited by subglacial fluvial processes, and these three forms represent: i) canal features associated with “steady state” deforming bed conditions and a braided channel network; ii) channel features and iii) Rchannels associated with rigid bed conditions. It is further suggested that this fluvial event was followed by a drumlinising event associated with fast ice flow (subglacial deforming bed erosion).