Aspects of the Paleogeography of Beringia During the Late Pleistocene

Hopkins, David M.

doi:10.1016/b978-0-12-355860-2.50008-9

Cited by 175 publications

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“…To our knowledge, cold-climate sand sheets 10 m or more thick have been detailed only from the Kittigazuit Formation in northwest Canada and from the Nushagak, Holitna and Upper Kuskokwim lowlands of southwestern Alaska (Lea, 1990(Lea, , 1996, although others may occur in central Alaska (Lea and Waythomas, 1990). Lea (1990) reported that ice-wedge pseudomorphs are widespread within the sand sheets of presumed full-glacial (DuvannyYar interval; Lea and Waythomas, 1990) (Hopkins, 1982;Dinter et al, 1990), with pervasive sea-ice cover on the Beaufort Sea combined with a very low glacioeustatic sea level minimizing moisture supply from the north (Bateman and Murton, 2006). …”

Section: Palaeoenvironmental Significancementioning

confidence: 99%

Syngenetic sand veins and anti‐syngenetic sand wedges, Tuktoyaktuk Coastlands, western Arctic Canada

Murton

Bateman

2007

Permafrost & Periglacial

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Sand‐sheet deposits of full‐glacial age in the Tuktoyaktuk Coastlands, western Arctic Canada, contain syngenetic sand veins 1–21 cm wide and sometimes exceeding 9 m in height. Their tall and narrow, chimney‐like morphology differs from that of known syngenetic ice wedges and indicates an unusually close balance between the rate of sand‐sheet aggradation and the frequency of thermal‐contraction cracking. The sand sheets also contain rejuvenated (syngenetic) sand wedges that have grown upward from an erosion surface. By contrast, sand sheets of postglacial age contain few or sometimes no intraformational sand veins and wedges, suggesting that the climatic conditions were unfavourable for thermal‐contraction cracking. Beneath a postglacial sand sheet near Johnson Bay, sand wedges with unusually wide tops (≤3.9 m) extend down from a prominent erosion surface. The wedges grew vertically downward during deflation of the ground surface, and represent anti‐syngenetic wedges. The distribution of sand veins and wedges within the sand sheets indicates that the existence of continuous permafrost during sand‐sheet aggradation can be inferred confidently only during full‐glacial conditions. Copyright © 2007 John Wiley & Sons, Ltd.

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Section: Palaeoenvironmental Significancementioning

confidence: 99%

Syngenetic sand veins and anti‐syngenetic sand wedges, Tuktoyaktuk Coastlands, western Arctic Canada

Murton

Bateman

2007

Permafrost & Periglacial

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“…the Arctic Coastal Plain of northern Alaska and Yukon (Hopkins, 1982;Dinter ., 1990). This area occupied the rainshadow of moisture sources in the Gulf of Alaska and the Bering Sea, and it is likely that pervasive sea$ice cover on the Beaufort Sea combined with a very low glacio$ eustatic sea level minimized moisture supply from the north.…”

Section: ! /mentioning

confidence: 99%

The chronostratigraphy of Late Pleistocene glacial and periglacial aeolian activity in the Tuktoyaktuk Coastlands, NWT, Canada

Bateman

Murton

2006

Quaternary Science Reviews

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Aeolian periglacial sand deposits are common in the Tuktoyaktuk Coastlands of Western Arctic Canada. Regionally extensive and thick aeolian sand$sheet deposits have been observed in two major stratigraphic settings: within a sand unit characterized by large aeolian dune deposits; and interbedded with glaciofluvial outwash from the Laurentide Ice Sheet (LIS). Small, localized sand sheets have also been observed along the tops of sandy bluffs, within sequences of drained thermokarst lakes deposits and as an involuted veneer above buried basal ice of the LIS.On the basis of radiocarbon and optically stimulated luminescence (OSL) dates from preserved periglacial aeolian sand sheets and dunes a regional chronostratigraphy is presented which indicates that both extensive dunes and sand sheets accumulated mainly between . 30 and 13 ka. A switch to dominantly sand$sheet aggradation at c. 14-13 ka, with sand sheets forming widely until . 8 ka, is attributed to (a) surface armouring by glacial deposits associated with the advance of the LIS; and (b) amelioration of the climate from cold aridity. An absence of OSL dates between . 8 and 1 ka suggests that sand sheets stabilized during much of the Holocene. Local sand$sheet aggradation during recent centuries has occurred near sandy bluffs and on the floors of drained thermokarst lakes. The OSL dates constrain the maximum extent of the LIS in the Tuktoyaktuk Coastlands to Marine Isotope Stage 2.

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“…During the late Wisconsin glacial episode (28-10 cal ka BP), the Bering land bridge connected the unglaciated parts of Alaska and the Yukon Territory with eastern Siberia to form an extensive continuous landmass known as Beringia (Hopkins, 1982). Beringian environments are of particular interest because they served as glacial refugia for various taxa (Hultén, 1937;Guthrie, 2001) and enabled the migration of plants, animals, and early humans between Eurasia and North America (Morlan and Cinq-Mars, 1982;Mason et al, 2001).…”

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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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Aspects of the Paleogeography of Beringia During the Late Pleistocene

Cited by 175 publications

References 0 publications

Syngenetic sand veins and anti‐syngenetic sand wedges, Tuktoyaktuk Coastlands, western Arctic Canada

Syngenetic sand veins and anti‐syngenetic sand wedges, Tuktoyaktuk Coastlands, western Arctic Canada

The chronostratigraphy of Late Pleistocene glacial and periglacial aeolian activity in the Tuktoyaktuk Coastlands, NWT, Canada

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

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