The sedimentary signature of ice-contact sedimentation and deformation at macro- and micro-scale: A case study from NW Scotland

Repeated advance and retreat of the East Antarctic Ice Sheet on the continental shelf during the early Pliocene warm period

“…Evidence for this is observed at the top of the unit sampled in thin section 4R1 87/100 where zones of skeleton grains with similarly orientated a-axes are related to subglacial deformation but cross-cutting these zones are large water escape structures that relate to deformational processes post initial subglacial modification probably involving small-scale debris or gravity flows (Fig. 5D) (Reinardy and Lukas, 2009). Indistinct discontinuous bedding at mmscale, dip at varying angles which may represent the base of small debris flow units or thin slurry layers that can occur at the surface of mass flow units (Phillips, 2006;Reinardy and Lukas, 2009).…”

“…5D) (Reinardy and Lukas, 2009). Indistinct discontinuous bedding at mmscale, dip at varying angles which may represent the base of small debris flow units or thin slurry layers that can occur at the surface of mass flow units (Phillips, 2006;Reinardy and Lukas, 2009). This type of poorly developed stratification within diamictons has previously been interpreted as debris flows that have partially sheared the tills (Hiemstra et al, 2004).…”

“…6A, B, Table 1). Previous work has suggested that these sorts of microstructures can be caused by turbulent flow within debris flows (Phillips, 2006;Reinardy and Lukas, 2009). In addition, there are occasional clustering of larger clasts across core giving the impression of flow plus occasional poorly developed stratification identified by thin (b 0.5 cm) layers of fine grey matrix which is distinct from the greyish brown matrix in other parts of the unit.…”

Till genesis at the bed of an Antarctic Peninsula palaeo-ice stream as indicated by micromorphological analysis

“…If, for example, turbate structures occur randomly throughout and are unrelated to other indicators of shear, their presence may suggest a diamicton origin from a gravity flow rather than from subglacial deformation (cf. Hiemstra 1999Hiemstra , 2001Lachniet et al 2001;Phillips 2006;Reinardy & Lukas 2009). The association of microstructures is key to interpreting the formation of different diamictons with low shear strength.…”

Sedimentary imprints of former ice-sheet margins: Insights from an end-Ordovician archive (SW Libya)

“…In this contribution, particular attention is paid to the characterisation of ice-front related stratigraphic architectures and macro-scale deformation structures (see Reinardy and Lukas, 2009 for a micro-scale case study). A well-preserved ice-marginal domain and its related succession were recently identified in the end-Ordovician glacial record of the western Murzuq Basin in Libya (Tihemboka area; Moreau et al, 2005;Moreau 2011;Ghienne et al, 2010;Girard et al, 2012a,b).…”