Stratigraphic Context of Old Crow Tephra, Holitna Lowland, Interior Southwest Alaska

AbstractA thick deposit of Old Crow tephra was discovered in a bluff exposure along the middle Holitna River near the Kulukbuk Hills (61°20′N latitude, 157°10′W longitude) in interior southwest Alaska. This locality is the southwesternmost-known deposit of Old Crow tephra in Alaska. Thickness and grain-size data from this site support a source volcano in the eastern Aleutian arc. Pleistocene stratigraphic sequences in the lowland are dominated by upward-fining eolian sand-sheet deposits and loess separated by organic silt. These deposits record at least two episodes of regional glaciation and an intervening nonglacial period (marine oxygen isotope stage 3, stage 5, or both). Old Crow tephra crops out near the top of the lower upward-fining eolian unit, indicating that the ash erupted near the end of an interval of periglacial eolian sedimentation. The sequence of eolian deposits that contain Old Crow tephra probably accumulated during the latter part of marine oxygen isotope stage 6, whereas the overlying eolian sequence formed during the last glaciation (stage 2). This stratigraphic position is consistent with other stratigraphic contexts for the tephra and with fission-track and thermoluminescence ages of ca. 140,000 ± 10,000 yr B.P.

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Oxygen isotope stage 3 fluvial and eolian successions in Europe compared with climate model results

Quaternary Research ◽

10.1016/s0033-5894(03)00002-4 ◽

2003 ◽

Vol 59 (2) ◽

pp. 223-233 ◽

Cited By ~ 24

Author(s):

K.o van Huissteden ◽

David Pollard

Keyword(s):

Oxygen Isotope ◽

Last Glacial Maximum ◽

Climate Model ◽

Regional Climate ◽

Glacial Maximum ◽

Oxygen Isotope Stage ◽

Last Glacial ◽

Wind Speeds ◽

Fluvial Response ◽

Eolian Deposits

AbstractFluvial and eolian successions of oxygen isotope stage 3 are compared with global (GCM) and regional climate (RCM) modeling experiments of the stage 3 and last glacial maximum climate in Europe. Differences in precipitation between stage-3 stades and interstades were minor, which is confirmed by the fluvial successions. The fluvial response to climate variation is non-uniform, and in southern Europe more pronounced than in northern Europe. The model simulations indicate a strong western winter circulation over Europe during stage 3, which is supported by the eolian deposits data. Wind speeds in the last glacial maximum simulation appear modest compared with those of stage 3, which contrasts with the abundance of eolian deposits. This suggests that during glacial climates the stabilizing effect of vegetation determines eolian sedimentation rates, rather than wind speed. Stage 3 can be divided into an older part (>45,000 cal yr B.P.) with a relatively stable landscape and moist climate and a younger part with more frequent climate change and decreasing landscape stability.

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Preliminary paleoenvironmental analysis of permafrost deposits at Batagaika megaslump, Yana Uplands, northeast Siberia

Quaternary Research ◽

10.1017/qua.2016.15 ◽

2017 ◽

Vol 87 (2) ◽

pp. 314-330 ◽

Cited By ~ 26

Author(s):

Julian B. Murton ◽

Mary E. Edwards ◽

Anatoly V. Lozhkin ◽

Patricia M. Anderson ◽

Grigoriy N. Savvinov ◽

...

Keyword(s):

Fine Sand ◽

Climatic Conditions ◽

Stratigraphic Sequence ◽

Oxygen Isotope Stage ◽

Mis 3 ◽

Eolian Sand ◽

Sand Sheet ◽

Mis 5 ◽

Paleoenvironmental Analysis ◽

Key Questions

AbstractA megaslump at Batagaika, in northern Yakutia, exposes a remarkable stratigraphic sequence of permafrost deposits ~50–80 m thick. To determine their potential for answering key questions about Quaternary environmental and climatic change in northeast Siberia, we carried out a reconnaissance study of their cryostratigraphy and paleoecology, supported by four rangefinder 14C ages. The sequence includes two ice complexes separated by a unit of fine sand containing narrow syngenetic ice wedges and multiple paleosols. Overall, the sequence developed as permafrost grew syngenetically through an eolian sand sheet aggrading on a hillslope. Wood remains occur in two forest beds, each associated with a reddened weathering horizon. The lower bed contains high amounts of Larix pollen (>20%), plus small amounts of Picea and Pinus pumila, and is attributed to interglacial conditions. Pollen from the overlying sequence is dominated by herbaceous taxa (~70%–80%) attributed to an open tundra landscape during interstadial climatic conditions. Of three hypothetical age schemes considered, we tentatively attribute much of the Batagaika sequence to Marine Oxygen Isotope Stage (MIS) 3. The upper and lower forest beds may represent a mid–MIS 3 optimum and MIS 5, respectively, although we cannot discount alternative attributions to MIS 5 and 7.

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Vertebrate Tracks in Pleistocene Eolian Sand-Sheet Deposits of Alaska

Quaternary Research ◽

10.1006/qres.1996.0023 ◽

1996 ◽

Vol 45 (2) ◽

pp. 226-240 ◽

Cited By ~ 31

Author(s):

Peter D. Lea

Keyword(s):

Cross Sections ◽

Silty Sand ◽

Large Herbivores ◽

Deformation Structures ◽

Eolian Sand ◽

Vertebrate Tracks ◽

Central Ridge ◽

Eolian Deposits ◽

Sand Sheet ◽

Sand Sheets

AbstractDeformation structures interpreted as vertebrate hoof- and foot-tracks occur within upper-Pleistocene eolian sand-sheet deposits in the stabilized Kantishna sand sea of central Alaska and in the Nushagak lowland of southwestern Alaska. Exposures of tracks are generally limited to cross sections, which reveal concave-up deformation structures in which displacement of preexisting strata diminishes downward. Deposits in both areas contain tracks that are 6 to 16 cm in diameter and are divided by a central ridge, reflecting formation by artiodactyl (even-toed) ungulates. Larger (21–34 cm) tracks without a central ridge, observed in the Nushagak lowland, were formed by proboscideans, probably woolly mammoth. Large vertebrate tracks occur within irregularly stratified sand and silty sand that accumulated upon partially vegetated sand sheets, and within thin, even wind-ripple laminae of unvegetated sand sheets. The presence of tracks at multiple stratigraphic levels and preservation of roots and rhizocretions within the eolian deposits suggest that vegetated sand sheets may have formed a locally important grazing habitat for large herbivores during at least part of the last glaciation. Recognition that vertebrate tracks are preserved in eolian sand-sheet deposits, and in deposits of other environments as well, opens a new source of stratigraphic and paleoecological data to aid reconstruction of the vanished ecosystems of Beringia.

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Late Quaternary (≥MIS 3 to MIS 1) stratigraphic transitions in a highland Beringian landscape along the Kuskokwim River, Alaska

Quaternary Research ◽

10.1017/qua.2019.51 ◽

2019 ◽

Vol 93 ◽

pp. 139-154

Author(s):

Joshua D. Reuther ◽

Jason Rogers ◽

Patrick Druckenmiller ◽

Thomas K. Bundtzen ◽

Kristi Wallace ◽

...

Keyword(s):

Late Quaternary ◽

Soil Development ◽

Bench Mark ◽

Vertical Angle ◽

Oxygen Isotope Stage ◽

Mis 3 ◽

Peaty Soil ◽

Loess Deposits ◽

Sand Sheet ◽

Stratigraphic Sequences

AbstractStratigraphic records extending to Marine Oxygen Isotope Stage (MIS) 3 (57,000–29,000 cal yr BP) or older in Beringia are extremely rare. Three stratigraphic sections in interior western Alaska show near continuous sedimentological and environmental progressions extending from at least MIS 3, if not older, through MIS 1 (14,000 cal yr BP–present). The Kolmakof, Sue Creek, and VABM (vertical angle bench mark) Kuskokwim sections along the central Kuskokwim River, once a highland landscape at the fringe of central and eastern Beringia, contain aeolian deposition and soil sequences dating beyond 50,000 14C yr BP. Thick peaty soil, shallow lacustrine, and tephra deposits represent the MIS 3 interstade (or older). Sand sheet and loess deposits, wedge cast development, and very thin soil development mark the later MIS 3 period and the transition into the MIS 2 stade (29,000–14,000 cal yr BP). Loess accumulation with thicker soil development occurred between ~16,000–13,500 cal yr BP at the MIS 2 and MIS 1 transition. After ~13,500 cal yr BP, loess accumulation waned and peat development increased throughout MIS 1. These stratigraphic sequences represent transitions between a warm and moist period during MIS 3, to a cooler and more arid period during MIS 2, then a return to warmer and moister climates in MIS 1.

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Spatially variable sedimentary responses to orbitally driven pluvial climate during Marine Oxygen Isotope Stage 5.1, Dakhla Oasis region, Egypt

Quaternary Research ◽

10.1016/j.yqres.2010.05.001 ◽

2010 ◽

Vol 74 (2) ◽

pp. 252-264 ◽

Cited By ~ 12

Author(s):

Ian A. Brookes

Keyword(s):

Oxygen Isotope ◽

Intertropical Convergence Zone ◽

Western Desert ◽

Convergence Zone ◽

Oxygen Isotope Stage ◽

Summer Insolation ◽

Stratigraphic Position ◽

Eolian Sediments ◽

Dakhla Oasis ◽

Osl Age

AbstractPleistocene basinal sediments (PBS) in the Dakhla region of Egypt's hyperarid Western Desert comprise four facies: (A) fluvio-lacustrine, (B) mixed lacustrine/pluvio-eolian, (C) pluvio-eolian, and (D) mixed eolian/pluvio-eolian. Contiguity of basins containing each facies, and their stratigraphic position between two bajada gravel formations, P/B-II and P/B-III, confirm their equivalence. Facies A and B, with lacustrine components, are attributed to orbitally forced poleward incursion of the Intertropical Convergence Zone (ITCZ), resulting in increased summer insolation/temperature/precipitation. Facies C and D, comprising pluvio-eolian and eolian sediments, reflect geologic/topographic influences overprinted on regional 'pluvial' conditions, eliminating lacustrine response. A Th/U age of ∼ 62 ka on lacustrine marl within Facies B is minimal, and an OSL age of 110 ± 18 ka on sediments immediately below Facies B is maximal. Since bajada gravels P/B-III are the youngest Pleistocene formation, they must represent the final strong incursion of the ITCZ into the Dakhla region at MIS 5.1, ∼ 80 ka. Because PBS Facies A pass rapidly up into P/B-III bajada gravels, PBS are assigned to the rising limb of the MIS 5.1 insolation/temperature/precipitation curve, slightly younger than 80 ka.

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Lithostratigraphy and limiting optical ages of the Pleistocene fill in Fraser River valley near Clinton, south-central British Columbia

Canadian Journal of Earth Sciences ◽

10.1139/e00-103 ◽

2001 ◽

Vol 38 (5) ◽

pp. 839-850 ◽

Cited By ~ 11

Author(s):

Olav B Lian ◽

Stephen R Hicock

Keyword(s):

Oxygen Isotope ◽

River Valley ◽

Fraser River ◽

Oxygen Isotope Stage ◽

Valley Fill ◽

The North ◽

South Central ◽

Last Glaciation ◽

Stage 4 ◽

Glacial Advance

The Fraser River valley near Clinton contains a thick sediment fill that is presently incised down to bedrock. The sequence, approximately 500 m thick, is generally upward fining and consists of up to 100 m of glacigenic debris flow diamicton and glaciofluvialdeltaic gravel and sand at the base, overlain by about 350 m of glaciolacustrine sediments and minor diamicton, which is in turn capped by several metres of till. The sequence is interpreted to represent (i) valley aggradation in response to glaciation, followed by (ii) the impoundment of the valley by sediment and (or) ice, and the formation of a large proglacial lake(s), and finally (iii) overriding of the valley fill by glaciers. This glacial advance sequence can be readily correlated with previously studied units situated immediately to the north, most of which have been associated with the last glaciation; however, the age of these units has been based only on stratigraphic relations. We introduce limiting optical ages from a widespread glaciolacustrine unit that show that the glacial advance sequence was formed, at the earliest, during the penultimate Okanagan Centre Glaciation (oxygen isotope stage 4; ca. 7459 ka), but almost certainly during the (last) Fraser Glaciation (oxygen isotope stage 2; ca. 2412 ka). It could not have been deposited during oxygen isotope stage 6, or during an older glaciation.

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