ABSTRACT This paper presents a detailed sedimentologic data set of minor moraines (heights ≤2.0 m, widths ≤14 m, lengths ≤108 m) that formed beginning near the end of the Little Ice Age by Schwarzensteinkees, a valley glacier in Austria. Sorted sediment and stratified diamict dominate five exposures, and compact massive diamict exists in one exposure. This sediment is interpreted as proglacial outwash and subglacial till. Most moraine sediment shows deformation structures (e.g., smaller and larger folds), and some units contain evidence of water escape. Other units maintain their original subhorizontality. All moraines contain unequivocal evidence of having formed through deformation by pushing during ice-margin fluctuations. Minor moraines formed more specifically by three identified processes: (1) pushing of outwash sediment; (2) stacking and pushing of outwash sediment; and (3) pushing of outwash sediment and freezing-on of subglacial till. Our data suggest that the sedimentologic composition of the valley fill influences the style of push-moraine formation. In this case, the friable nature of outwash sediments can increase the efficiency of the pushing ice front and the likelihood of sediment collapse down the proximal ice-contact slope after ice retreat. This study contributes to our understanding of sediment transport and deposition in high-mountain environments.

ABSTRACT The Tuya-Kawdy region of northern British Columbia is well established as a place where glaciation and volcanism overlapped in space. However, no modern work has integrated observations from the region’s volcanic and glacial deposits with geochronologic constraints to summarize how they might overlap in time. Here, we provide a general overview of such characteristics and 23 new 40 Ar/ 39 Ar eruption ages of glaciovolcanic deposits ranging from 4.3 Ma to 63 ka to constrain the timing, location, and minimum thicknesses and distributions of coincident ice. Subaerial lava fields interspersed with glaciovolcanism record periods of ice-sheet absence in presumably warmer climate conditions. These generally coincide with interglacial marine isotope stages. Many of the volcanoes have a secondary record of posteruption glacial modification, cirques, erratics, and mega-lineations, which document later climate changes up to the present. We used edifice-based terrain analysis to reconstruct changes to local minimum Cordilleran ice-sheet thicknesses, extents, and flow directions at specific locations and times during the late Pliocene and the Pleistocene.

ABSTRACT The Eagle Lake basin was formed by collapse of the ablating Lake Michigan lobe over a tunnel valley and subsequent reoccupation of the collapse basin by the lobe during local final phase of glaciation. Latest collapse occurred prior to about 16,250 but after 18,600 cal yr B.P. A hydrologically open lake occupied Eagle Lake basin from 16,250 cal yr B.P. to the present. The lake was described in 1834 by the original land survey, but was drained for agriculture by 1939.

ABSTRACT Lobes, or ice streams, of the southern Laurentide ice sheet readvanced periodically during their overall retreat after the Last Glacial Maximum in the Great Lakes region. The Saginaw Lobe readvanced around 20 ka to form a prominent moraine, the Sturgis moraine, near the Michigan-Indiana border. Detailed mapping of nineteen 7½ min quadrangles at a scale of 1:24,000 in and adjacent to Calhoun County, Michigan, supports the interpretation that a large drumlin field behind the moraine was formed at this time, when the basal drainage of the glacier was distributed with high basal pore pressure. During retreat, after moraine construction, the drainage mode switched to a conduit-type system, in which meltwater drained to recessional ice-marginal positions through tunnel valleys. We mapped at least three discontinuous ice-marginal positions on the basis of coarse-grained, subaerial fans beginning at the ends of the tunnel valleys. There is a close association of kames with the tunnel valleys at these locations, suggesting that supraglacial meltwater contributed to the subglacial drainage. Our results support a model in which the drumlins were produced by deformation of the basal diamicton during ice advance prior to the formation of the tunnel valleys during ice retreat. This hypothesis rebuts a previously proposed model for this area in which the drumlins and tunnel valleys, along with boulder gravel deposits, were attributed to formation during a single, catastrophic subglacial sheetflood.

ABSTRACT The northern Puget Lowland of Washington State, USA, provides an exceptional opportunity not only to examine grounding line processes associated with marine-based ice sheets, but also to relate subaerial outcrop to marine geological observations of grounding line landforms and sedimentary processes in Antarctica and the deglaciated Northern Hemisphere. During this trip, we visit outcrops that record the interaction of the Cordilleran Ice Sheet and its bed, starting with locations where the ice sheet slowly flowed across crystalline bedrock. We also visit locations where the ice flowed across unconsolidated deposits, allowing discussions of subglacial bed deformation and grounding zone wedge development. Evidence shows that grounding line retreat across Whidbey Island was punctuated by periods of grounding line position stability and local ice advance during the growth of multiple grounding zone wedges. We will discuss the criteria for identifying grounding zone wedges, including diamicton units with foreset bedding that downlap onto a regional glacial unconformity at the base, and are truncated at the top by localized unconformities indicative of ice advance across the foreset beds. Grounding zone wedge foreset beds are composed of debris flows sourced from a deformation till and from sediment transported to the grounding line by subglacial meltwater. The overlying surface unconformity is associated with a laterally discontinuous till and pervasive glacial lineations. Other field stops focus on iceberg scouring and evidence of subglacial meltwater drainage, as well as the transition from marine to subaerial conditions during retreat of the Cordilleran Ice Sheet from the northern Puget Lowland.