Limits of mountain and continental glaciations east of the Continental Divide in northern Montana and north-western North Dakota, U.S.A.

Fullerton, David S.; Colton, R.B.; Bush, Charles A.

doi:10.1016/s1571-0866(04)80194-5

Cited by 10 publications

(11 citation statements)

References 60 publications

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“…Jennings, 2006), whose landform and sedimentary characteristics resemble those of a surging glacier landsystem (Evans et al, 1999). During the LGM, Laurentide ice streams flowed into the province of Alberta from the north and west, extending to the ice sheet limit in northern Montana (Fullerton and Colton, 1986;Fullerton et al, 2004aFullerton et al, , 2004b. We here present evidence for fast glacier flow and possible palaeo-ice streams in the southeastern and east-central parts of the province of Alberta and assess the implications of this evidence for ice sheet palaeodynamics.…”

Section: Introductionmentioning

confidence: 79%

Landform and sediment imprints of fast glacier flow in the southwest Laurentide Ice Sheet

Evans

Clark

Rea

2008

J Quaternary Science

117

167

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Evidence for former fast glacier flow (ice streaming) in the southwest Laurentide Ice Sheet is identified on the basis of regional glacial geomorphology and sedimentology, highlighting the depositional processes associated with the margin of a terrestrial terminating ice stream. Preliminary mapping from a digital elevation model of Alberta identifies corridors of smoothed topography and corridor-parallel streamlined landforms (megaflutes to mega-lineations) that display high levels of spatial coherency. Ridges that lie transverse to the dominant streamlining patterns are interpreted as: (a) series of minor recessional push moraines; (b) thrust block moraines or composite ridges/hill-hole pairs constructed during readvances/surges; and (c) overridden moraines (cupola hills), apparently of thrust origin. Together these landforms demarcate the beds and margins of former fast ice flow trunks or ice streams that terminated as lobate forms. Localised cross-cutting and/or misalignment of flow sets indicates temporal separation and the overprinting of ice streams/lobes. The fast-flow tracks are separated by areas of interlobate or inter-stream terrain in which moraines have been constructed at the margins of neighbouring (competing) ice streams/outlet glaciers; this inter-stream terrain was covered by more sluggish, non-streaming ice during full glacial conditions. Thin tills at the centres of the fast-flow corridors, in many places unconformably overlying stratified sediments, suggest that widespread till deformation may have been subordinate to basal sliding in driving fast ice flow but the general thickening of tills towards the lobate terminal margins of ice streams/outlet glaciers is consistent with subglacial deformation theory. In this area of relatively low relief we speculate that fast glacier flow or streaming was highly dynamic and transitory, sometimes with fast-flowing trunks topographically fixed in their onset zones and with the terminus migrating laterally. The occurrence of minor push moraines and flutings and associated landforms, because of their similarity to modern active temperate glacial landsystems, are interpreted as indicative of ice lobe marginal oscillations, possibly in response to seasonal climatic forcing, in locations where meltwater was more effectively drained from the glacier bed. Further north, the occurrence of surging glacier landsystems suggests that persistent fast glacier flow gave way to more transitory surging, possibly in response to the decreasing size of ice reservoir areas in dispersal centres and also locally facilitated by ice-bed decoupling and drawdown initiated by the development of ice-dammed lakes.

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Section: Introductionmentioning

confidence: 79%

Landform and sediment imprints of fast glacier flow in the southwest Laurentide Ice Sheet

Evans

Clark

Rea

2008

J Quaternary Science

117

167

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“…At the peak of the late Pleistocene (Wisconsinan) glaciation, the Laurentide Ice Sheet coalesced with the Cordilleran Ice Sheet and montane and piedmont glaciers (Pinedale glaciation in Montana) over much of the Northern Front, with tracts of unglaciated land separating them on the Porcupine Hills and just south of the Alberta-Montana border (Bobrowsky and Rutter, 1992;Cannon, 1996;Fullerton et al, 2004;Jackson et al, 2008;Dalton et al, 2020). Ice sheets and glaciers left a dramatic mark on the landscape, with deep U-shaped valleys in the mountains and thick glacial deposits on the foothills and the plains (Fenton et al, 2013;Atkinson et al, 2020).…”

Section: Geomorphologymentioning

confidence: 99%

“…Detailed information for each kettle is listed in Table1. Boundaries of glacial maxima fromFullerton et al (2004); location of chert-bearing exposures fromCannon (1996) andMudge and Earhart (1983).…”

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confidence: 99%

Glacial kettles as archives of early human settlement along the Northern Rocky Mountain Front

Lanoë

Zedeño

Jansson³

et al. 2021

Quat. res.

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The Northern Rocky Mountain Front (hereafter Northern Front) is a prominent geographic feature in archaeological models of human dispersal in the terminal Pleistocene and Early Holocene of North America. Testing those models has been arduous because of local geomorphological factors that tend to obliterate or otherwise limit access to archaeological finds of relevant age. In this paper, we present well-stratified archaeological and environmental records dating back to 14,000–13,000 cal yr BP from the site of Billy Big Spring (Blackfeet Indian Reservation, Montana), located on a glacial kettle, a type of landform that has been largely ignored by regional archaeological research to date. Findings from Billy Big Spring show the continuous use of the Northern Front foothills throughout the major climatic and environmental disturbances of the Early Holocene, and possibly the terminal Pleistocene as well. As such, Billy Big Spring contributes to refining several archaeological models of early settlement of the Northern Front, particularly those that posit differential use of foothills versus plains settings during the midst of the Holocene Thermal Maximum. The record at Billy Big Spring also suggests that kettles, regardless of physiographic setting, provide a yet unsuspected and unsampled potential for preserving high-quality and easily accessible early archaeological and paleoenvironmental records.

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“…A second, relatively deep divergence (0.43 Ma) between the NWL, NEL, and SL falls within local glacial cycles beginning with the Sacajawea Ridge (0.6 Ma) (Pierce 2004) and ending with the initiation of Bull Lake glaciation (Fullerton et al . 2004).…”

Section: Discussionmentioning

confidence: 99%

Fire and ice: genetic structure of the Uinta ground squirrel (Spermophilus armatus) across the Yellowstone hotspot

et al. 2008

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The range of the Uinta ground squirrel, Spermophilus armatus, is centred over one of the most tectonically active regions today, the Yellowstone hotspot. We document the role of Quaternary tectonic and climatic history on the genetic structure of this species by screening museum and extant individuals throughout its range. Phylogeographic, divergence time, and demographic analyses of partial mitochondrial cytochrome b and control region DNA sequences yield insight into the cadence of evolution across three spatiotemporal scales: (i) a relatively deep intraspecific divergence of S. armatus into three lineages coincident with the last major volcanic eruption in the region and maintained by the Snake River Plain; (ii) demographic expansion in two lineages corresponding to the time of last deglaciation of the region; and (iii) a recent (< 50 years) local extinction of the third lineage coincident with climatic change and conversion of habitat for agricultural purposes in eastern Idaho. Beyond these inferences, our study highlights the unique value of museum material to phylogeography, and shows that small mammal recolonization of previously glaciated montane 'islands' differs from northward postglacial expansion observed in areas previously covered by continental ice sheets. Montane 'islands' may harbour high genetic diversity because of admixture and recurrent expansion/extinction.

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Limits of mountain and continental glaciations east of the Continental Divide in northern Montana and north-western North Dakota, U.S.A.

Cited by 10 publications

References 60 publications

Landform and sediment imprints of fast glacier flow in the southwest Laurentide Ice Sheet

Landform and sediment imprints of fast glacier flow in the southwest Laurentide Ice Sheet

Glacial kettles as archives of early human settlement along the Northern Rocky Mountain Front

Fire and ice: genetic structure of the Uinta ground squirrel (Spermophilus armatus) across the Yellowstone hotspot

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