Minor end moraines of the Wisconsin Valley Lobe, north-central Wisconsin, USA

Abstract

Approximately 35 parallel, discontinuou s glacial ridges occur in an area of about 100 km 2 in north-centra l Wisconsin. The ridges are located between about 6 and 15 km north (formerly up-ice) of the maximum extent of the Wisconsin Valley Lobe of the Laurentide Ice Sheet. The ridges are between 1 and 4 m high, up to 1 km long, and spaced between 30 and 80 m apart. They are typically asymmetrical with a steep proximal (ice-contact) slope and gentle distal slope. The ridges are composed primarily of subglacia l till on their proximal sides and glacial debris-ow sediment on the distal sides. In some ridges the till and debris-ow sediment are underlain by sorted sediment that was deformed in the former direction of ice ow. We interpret the ridges to be recessiona l moraines that formed as the Wisconsin Valley Lobe wasted back from its maximum extent, with each ridge having formed by a sequence of (1) pushing of sorted ice-margina l sediment, (2) partial overriding by the glacier and deposition of subglacia l till on the proximal side of the ridge, and (3) depositio n of debrisow sediment on the distal side of the ridge after the frozen till at the crest of the ridge melted. The moraines are similar to annual recessiona l moraines describe d at several modern glaciers, especiall y the northern margin of Myrdalsjökull, Iceland. Thus, we believe the ridges probably formed as a result of minor winter advances of the ice margin during deglaciation . Based on this assumption, we calculate the net rate of ice-surfac e lowering of the Wisconsin Valley Lobe during the period when the moraines formed. Various estimates of icesurface slope and rates of ice-margin retreat yield a wide range of values for ice-surface lowering (1.7-14.5 m/yr). Given that ablation rates must exceed those of ice-surface lowering, this range of values suggests relatively high summer temperature s along the margin of the Wisconsin Valley Lobe when it began retreating from its maximum extent. In addition, the formation of annual moraines indicates that the glacier toe was thin, the ice surface was clean, and the ice margin experience d relatively cold winters.

Sub‐annual moraine formation at an active temperate Icelandic glacier

“…The sedimentological end products (ice-marginal moraines) in ancient glacial environments can thus be used to reconstruct past glacier dynamics (e.g. Ham and Attig, 2001;Sutherland et al, 2019).…”

Processes of annual moraine formation at a temperate alpine valley glacier: insights into glacier dynamics and climatic controls

“…It also provides modern analogues for the formation of larger features that were formed in front of outlet glaciers of ice caps or even the lobes of continental ice sheets during the Quaternary through the up-scaling of individual processes contributing to moraine formation and their controls (cf. Bennett 2001;Ham & Attig 2001;Evans 2003). This paper presents detailed sedimentological data from a representative selection of annual moraines formed over the last~30 years at the snout of Gornergletscher in the southern Central Alps, Switzerland, with the aims of assessing the applicability of existing models of annual moraine formation to an alpine valley glacier and providing fresh insights into moraine-forming processes and climatic control in such settings.…”

Palaeogeographic reconstruction of the Late Weichselian ice sheet in north‐central Poland based on relief analysis

“…6) may represent sequences of push moraines formed during short-lived icesheet advances, reflecting the extent of the ice-sheet front. These forms, although higher than those recorded in Iceland (Chandler et al, 2020), reached heights similar to those in Wisconsin (Ham, Attig, 2001). The series of lower hills located between the push moraines, as well as at the back of the terminal moraines of the Chalin lobe (Chl) (Fig.…”