Late Vendian-?Cambrian glacially influenced deep-water sedimentation, Macduff Slate Formation (Dalradian), NE Scotland

Abstract

The deep-water metasedimentary rocks of the late Dalradian Macduff Slate Formation preserve a record of distal glaciomarine sedimentation in the form of ice-rafted dropstones and related bedding-deformation structures, glaciogenic debris-flow diamictites and an allochthonous slump unit. The input of ice-rafted debris was cyclical and probably related to periodic disintegration of the marine margin of an ice sheet. Downslope resedimentation processes, typical of glaciated continental margins, were responsible for the diamictites and slump deposits which were probably derived from the adjacent outer shelf and upper slope, in common with Pleistocene analogues off NW Britain. The uppermost diamictite bed is an integral part of the deep-marine succession, in contrast to the previously proposed lodgement-till hypothesis.