Model of patchwork landsystem development inferred from geomorphic imprints of variable ice‐flow dynamics: New insights into the evolution of an ice‐sheet marginal lobe

The reconstruction of ice‐sheet dynamics can be achieved by analysing changes in the morphology of landforms that form an evolutionary sequence, in which individual features may either align with or be transverse to the direction of ice flow. Over time, the transformation of these landforms in response to ice‐sheet processes demonstrates reorientation and successive changes in the relationship between processes and forms, typically in the direction of ice flow. This paper explores the evolving structure of a landsystem and the dynamics of the lobate margin of the Scandinavian Ice Sheet, along with its palaeoglaciological conditions during the Late Weichselian glaciation near Rajgród (NE Poland), where ridges transverse to the ice‐sheet flow have been identified. These features include large‐scale ribs, highly transformed ribs with superimposed smaller ribbed moraine and controlled moraine. The identified ribbed bedforms represent incipient linear and transitional types (characterised by up‐ice‐pointing horns), reflecting changes in the stick–slip sliding behaviour at the base of the ice‐sheet lobe. The zone of controlled moraine suggests the presence of debris‐rich ice, likely frozen to its bed, where permafrost may have extended from the proglacial area. The occurrence of small‐scale ribs and the zone of controlled moraine further confirm the patchwork system and band‐like pattern of increased basal shear stress, which would have decelerated ice‐flow velocity within the ice lobe formed by the Mazury Palaeo‐ice Stream. These landforms, along with flute‐like features, were superimposed on pre‐existing large‐scale ribs, indicating the potential for multiple slowdowns in ice flow, interrupted by phases of faster movement. Consequently, the landforms represent a complex palimpsest in the lobate margin of the ice sheet, which evolved during the waning stages of the Weichselian deglaciation, reflecting the changing dynamics of compressional ice flow. Lastly, the doughnut‐shaped and hummocky moraine most likely developed under differential redistribution of supraglacial debris, resulting from the down‐wasting of stagnant ice.