Surficial Geology of northern Yukon Territory and northwestern District of Mackenzie, Northwest Territories

Hughes, O L

doi:10.4095/102354

Cited by 61 publications

(46 citation statements)

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“…HUGHES era/. (1981) conclude that the Laurentide Ice Sheet reached its all-time limit in the northeastern Yukon during the Late Wisconsinan, reversing the earlier conclusion (HUGHES, 1972) that the limit was of Early Wisconsinan age. DYKE (in press) argues that the Early Wisconsinan (or Sangamonian) limit of VINCENT (1983) on Banks Island is to Late Wisconsinan age, reverting to the age assignment of PREST (1969).…”

Section: The Glacial Limitmentioning

confidence: 99%

Late Wisconsinan and Holocene History of the Laurentide Ice Sheet*

Dyke

Prest

2008

gpq

833

478

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AbstractEleven paleogeographic maps and a summary ice retreat map outline the history of advance, retreat, and readvances of the Laurentide Ice Sheet along with associated changes in proglacial drainage and relative sea level oscillations for Late Wisconsinan and Holocene times. The text outlines pertinent chronological control and discusses the paleoglaciology of the ice sheet, with attention to location and migration of ice divides, their attendant domes and saddles, and to ice streams, ice shelves, and mechanisms of déglaciation. At 18 ka the ice sheet consisted of 3 sectors with an interlocked system of ice divides joined at intersector saddles. A throughgoing superdivide is recognized and named the Trans Laurentide Ice Divide. The ice sheet retreated slowly from 18 to 13 ka, mainly along the west and south margins, but still held a near maximum configuration at 13 ka. A regional change in flow pattern over the Prairies just before 14 ka is thought to represent a large reduction in ice volume, but not in extent, and likely was triggered by a switch from nondeforming to deforming bed conditions. Retreat between 13 and 8 ka was vastly more rapid in the west than in the east, which resulted in eastward migration of the divide system of Keewatin Ice but relatively static divides of Labrador and Foxe Ice. By 10 ka the Trans Laurentide Ice Divide had been fragmented as Hudson Ice became increasingly autonomous. By 8 ka Hudson Ice had disappeared, little ice was left in Keewatin, but Foxe Ice still held its near maximum configuration and Labrador Ice was still larger than Foxe Ice. Repeated surging along aquatic margins and calving back of margins thinned by surging probably was the most important mechanism of deglaciation of Keewatin and Hudson Ice. The core of Foxe Ice disintegrated at 7 ka but retreat and readvance of Foxe Ice remnants continued throughout the Holocene.

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Section: The Glacial Limitmentioning

confidence: 99%

Late Wisconsinan and Holocene History of the Laurentide Ice Sheet*

Dyke

Prest

2008

gpq

833

478

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“…The study area lies beyond the maximum limit of Pleistocene glaciations (Fig. 1); Hughes (1972) and Rampton (1982) have pointed out that the last major ice advance (Buckland glaciation of Wisconsin age) was restricted to the YCP to the north and northeast of Trout Lake.…”

mentioning

confidence: 99%

Late glacial and Holocene sedimentation, vegetation, and climate history from easternmost Beringia (northern Yukon Territory, Canada)

et al. 2012

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Beringian climate and environmental history are poorly characterized at its easternmost edge. Lake sediments from the northern Yukon Territory have recorded sedimentation, vegetation, summer temperature and precipitation changes since ~ 16 cal ka BP. Herb-dominated tundra persisted until ~ 14.7 cal ka BP with mean July air temperatures ≤ 5°C colder and annual precipitation 50 to 120 mm lower than today. Temperatures rapidly increased during the Bølling/Allerød interstadial towards modern conditions, favoring establishment ofBetula-Salixshrub tundra. Pollen-inferred temperature reconstructions recorded a pronounced Younger Dryas stadial in east Beringia with a temperature drop of ~ 1.5°C (~ 2.5 to 3.0°C below modern conditions) and low net precipitation (90 to 170 mm) but show little evidence of an early Holocene thermal maximum in the pollen record. Sustained low net precipitation and increased evaporation during early Holocene warming suggest a moisture-limited spread of vegetation and an obscured summer temperature maximum. Northern Yukon Holocene moisture availability increased in response to a retreating Laurentide Ice Sheet, postglacial sea level rise, and decreasing summer insolation that in turn led to establishment ofAlnus-Betulashrub tundra from ~ 5 cal ka BP until present, and conversion of a continental climate into a coastal-maritime climate near the Beaufort Sea.

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“…The lower lacustrine unit, at river level, was originally thought to have formed in late Pleistocene time during one of the periods when glaciers blocked eastward drainage through the Richardson Mountains. This blockage caused lowlands west of the mountains, such as Old Crow Basin, to be flooded with diverted meltwater (HUGHES, 1972). The age of the lower lake unit in Old Crow Basin is not known, but recent evidence suggests that it is older than early Wisconsinan (MORLAN, n.d.a.…”

Section: Stratigraphy and Sample Provenancementioning

confidence: 99%

Taphonomy and Paleoecology of Fossil Insect Assemblages from Old Crow River (CRH-15) Northern Yukon Territory, Canada

Morlan¹,

Matthews²

2007

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The paleoenvironmental message delivered by any fossil assemblage is nearly always filtered to some degree by taphonomic and preservational biases. This paper discusses some of the types of biases that affect the composition of fossil Coleoptera (beetles) assemblages. Eight samples from a single site in the northern Yukon provide the raw data for the analysis. They represent different types of host sediments — ranging from autochthonous peats to organic rich alluvial sands. For each assemblage the authors noted the state of preservation of the fossils, counted the individual anatomical parts (pronota, heads, elytra) referred to each taxon and the number of articulated or partially articulated specimens, and sorted the fossils on the basis of predefined ecological groups. The resulting data were then examined statistically, and compared with paleoenvironmental conclusions derived by examination of the present distribution of the taxa in each assemblage. The content of the insect assemblages varies with the type of host sediment. Insect fossils from autochthonous sediments deliver a reliable local environmental signal. Allochthonous sediments, such as alluvium, might be expected to contain fossils that provide an integrated picture of the regional environment, but in the Yukon such samples are seriously overrep resented by Lepidophorus lineaticollis, a weevil that lives on or near sandy floodplains. Deviations in the representation of particular anatomical elements of L. lineaticollis from one sample to another warn of other more subtle taphonomic biases that may also skew the content of northern fossil insect assemblages.Le message paléoenvironnemental transmis par toute association de fossiles est presque toujours plus ou moins dénaturé par des facteurs liés à la taphonomie et à la préservation. Le rapport présente certaines catégories de facteurs qui influent sur la composition des associations de coléoptères fossiles. Les données brutes sont tirées de huit échantillons provenant d'un seul emplacement dans le nord du Yukon. Ces échantillons représentent divers types de sédiments encaissants. Pour chaque association, on a noté l'état de préservation des fossiles, compté le nombre de parties anatomiques (pronota, têtes, élytres) par taxon et le nombre d'échantillons articulés ou partiellement articulés, et trié les fossiles selon des groupes écologiques prédéterminés. Les données ont été étudiées statistiquement, puis comparées aux conclusions paléoenvironnementales tirées de l'étude de la répartition actuelle des taxons dans chaque association. Le contenu des associations d'insectes varie en fonction du type de sédiment encaissant. Les insectes fossiles dans les sédiments autochtones fournissent des données fiables sur l'environnement local. Les sédiments allochtones comme les alluvions devraient contenir des fossiles qui donneraient une image intégrée de l'environnement régional; toutefois, au Yukon, ces échantillons sont gravement surreprésentés par le Lepidophorus lineaticollis. Les écarts dans la représentati...

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Surficial Geology of northern Yukon Territory and northwestern District of Mackenzie, Northwest Territories

Cited by 61 publications

References 0 publications

Late Wisconsinan and Holocene History of the Laurentide Ice Sheet*

Late Wisconsinan and Holocene History of the Laurentide Ice Sheet*

Late glacial and Holocene sedimentation, vegetation, and climate history from easternmost Beringia (northern Yukon Territory, Canada)

Taphonomy and Paleoecology of Fossil Insect Assemblages from Old Crow River (CRH-15) Northern Yukon Territory, Canada

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