Cryostratigraphy of the Klondike "muck" deposits, west-central Yukon Territory

2000 ◽  
Vol 37 (6) ◽  
pp. 849-861 ◽  
Author(s):  
E Kotler ◽  
C R Burn
Keyword(s):  
Abrupt Change ◽  
Late Quaternary ◽  
Yukon Territory ◽  
Valley Bottom ◽  
Glacial Sediments ◽  
The Holocene ◽  
Oxygen Isotope Ratios ◽  
Bottom Deposits ◽  
Late Wisconsinan ◽  
Lower Contact

Four late Quaternary cryostratigraphic units are recognized in the unconsolidated valley-bottom deposits of the Klondike area, Yukon Territory. Three of the units, in ice-rich, loessal sediments of pre-Wisconsinan or Wisconsinan age, collectively compose the King Solomon Formation. They are overlain by a Holocene organic unit. The units are distinguished by their cryostratigraphic characteristics and oxygen-isotope ratios of included ground ice. The basal unit is the Last Chance Creek Member, a pre-Late Wisconsinan deposit, containing preserved ice wedges δ18O ~ -28 to -26‰; δD ~ -225 to -209‰). The overlying Quartz Creek Member, a Late Wisconsinan unit, is dominated by organic-rich loess. Massive ice is noticeably absent, although the sediments are ice rich. The isotopic composition of ice in this unit is characteristic of full-glacial conditions (δ18O ~ -32 to -29‰; δD ~ -234 to -257‰). An abrupt change to warmer and wetter conditions at the end of glaciation, prior to the Holocene, is recorded by the ice-rich, colluviated Dago Hill Member (δ18O ~ -28 to -21‰; δD ~ -164 to -225‰), which began accumulating by 11.62 14C ka BP. Large ice wedges originate in this unit, and, in places, penetrate the underlying full-glacial sediments. Even higher δ18O and δD values occur for ice in the Holocene organic unit (δ18O ~ -25 to -20‰; δD ~ -164 to -189‰). The majority of the massive icy bodies in the King Solomon Formation are ice wedges, but pool ice and aggradational ice are also exposed, especially in the Dago Hill Member. Massive icy beds formed by groundwater intrusion into permafrost occur at the lower contact of the Quartz Creek Member.

Late Quaternary Vegetation Development in South-Central Illinois

1972 ◽  
Vol 2 (02) ◽  
pp. 217-231 ◽  
Author(s):  
Eberhard Grüger
Keyword(s):  
Late Quaternary ◽  
Deciduous Tree ◽  
Deciduous Trees ◽  
Vegetation Development ◽  
Pollen Diagram ◽  
Geological Evidence ◽  
The Holocene ◽  
South Central ◽  
Late Wisconsinan ◽  
Central Illinois

Pollen and macrofossil evidence for the nature of the vegetation during glacial and interglacial periods in the regions south of the Wisconsinan ice margin is still very scarce. Modern opinions concerning these problems are therefore predominantly derived from geological evidence only or are extrapolated from pollen studies of late Wisconsinan deposits. Now for the first time pollen and macrofossil analyses are available from south-central Illinois covering the Holocene, the entire Wisconsinan, and most probably also Sangamonian and late Illinoian time. The cores studied came from three lakes, which originated as kettle holes in glacial drift of Illinoian age near Vandalia, Fayette County. The Wisconsinan ice sheet approached the sites from the the north to within about 60 km distance only.One of the profiles (Pittsburg Basin) probably reaches back to the late Illinoian (zone 1), which was characterized by forests with muchPicea. Zone 2, most likely of Sangamonian age, represents a period of species-rich deciduous forests, which must have been similar to the ones that thrive today south and southeast of the prairie peninsula. During the entire Wisconsinan (14C dates ranging from 38,000 to 21,000 BP) thermophilous deciduous trees likeQuercus, Carya, andUlmusoccurred in the region, although temporarily accompanied by tree genera with a more northerly modern distribution, such asPicea, which entered and then left south-central Illinois during the Woodfordian. Thus it is evident that arctic climatic conditions did not prevail in the lowlands of south-central Illinois (about 38°30′ lat) during the Wisconsinan, even at the time of the maximum glaciation, the Woodfordian. The Wisconsinan was, however, not a period of continuous forest. The pollen assemblages of zone 3 (Altonian) indicate prairie with stands of trees, and in zone 4 the relatively abundantArtemisiapollen indicates the existence of open vegetation and stands of deciduous trees,Picea, andPinus. True tundra may have existed north of the sites, but if so its pollen rain apparently is marked by pollen from nearby stands of trees. After the disappearance ofPinusandPiceaat about 14,000 BP (estimated!), there developed a mosaic of prairies and stands ofQuercus, Carya, and other deciduous tree genera (zone 5). This type of vegetation persisted until it was destroyed by cultivation during the 19th and 20th century. Major vegetational changes are not indicated in the pollen diagram for the late Wisconsinan and the Holocene.The dating of zones 1 and 2 is problematical because the sediments are beyond the14C range and because of the lack of stratigraphic evidence. The zones dated as Illinoian and Sangamonian could also represent just a Wisconsinan stadial and interstadial. This possibility, however, seems to be contradicted by the late glacial and interglacial character of the forest vegetation of that time.

On the nature and origin of "muck" deposits in the Klondike area, Yukon Territory

1997 ◽  
Vol 34 (10) ◽  
pp. 1333-1344 ◽  
Author(s):  
T. A. Fraser ◽  
C. R. Burn
Keyword(s):  
Organic Matter ◽  
Fine Sand ◽  
Yukon Territory ◽  
Low Flow ◽  
Radiocarbon Dates ◽  
The Holocene ◽  
Yukon River ◽  
Laboratory Investigations ◽  
Late Wisconsinan ◽  
Kluane Lake

Organic-rich "muck" deposits, which blanket auriferous gravels in the Klondike area, Yukon Territory, comprise two principal stratigraphic units: (i) a silty Late Pleistocene deposit, and (ii) Holocene organics lying unconformably on the silt. The deposits are found predominantly in valley bottoms and, if undisturbed, are normally perennially frozen. Field and laboratory investigations of particle size, mineralogy, and morphology, as well as organic matter and sedimentary structures, indicate that the silt is both primary (massive) and redeposited (bedded) loess (by weight 87% medium and coarse silt and fine sand). Radiocarbon dates indicate that the loess was deposited during Late Wisconsinan McConnell glaciation, beginning after 27 000 14C years BP. The loess was likely derived from the floodplain of the Yukon River during periods of low flow. Turf in growth position and organic matter in the silt similar to that of loessal grasslands near Kluane Lake suggest a grassland environment for the area during McConnell glaciation. A mummified carcass in the silts indicates that some of these sediments have been frozen since shortly after deposition. Ice wedges are commonly found in the upper portion of the silt, but these wedges rarely extend into the overlying organic material. Separate, smaller ice wedges are found in the Holocene unit. Radiocarbon dates indicate that peat growth began at the start of the Holocene, as in other unglaciated portions of Yukon, when the climate became abruptly wetter.

Late Quaternary events in the Lethbridge area, Alberta

1989 ◽  
Vol 26 (3) ◽  
pp. 551-560 ◽  
Author(s):  
Willem J. Vreeken
Keyword(s):  
Late Quaternary ◽  
Landscape History ◽  
Glacial Lake ◽  
The Holocene ◽  
Green Lake ◽  
Southern Alberta ◽  
Soil Landscape ◽  
Loess Deposition ◽  
Late Wisconsinan

New observations in the Lethbridge area permit a more complete reconstruction of the landscape history in Late Wisconsinan and Holocene time. The plain of glacial Lake Macleod, the Lethbridge moraine, and the plain of glacial Lake Lethbridge became exposed in that order and in quick succession. Almost immediately thereafter, a discontinuous mantle of loess began to accumulate on those surfaces. The presence of Glacier Peak layer G or Manyberries tephra near the base of the loess indicates these events occurred just before 11 200 BP. The similarity of this chronology to that established for the older Green Lake end moraine in the Cypress Hills region and the fact that the younger Buffalo Lake moraine was formed before 11 000 BP indicate that deglaciation of southern Alberta proceeded very rapidly.The oldest buried paleosol observed near Lethbridge began to form shortly after 11 200 BP. Subsequently, and throughout the Holocene, intervals of loess deposition alternated with soil-forming intervals. At least six soil–landscape cycles occurred between 11 200 and 6800 BP (before the Mazama tephra was deposited), and at least five cycles occurred subsequently. Occurrences of postglacial loess more than 3 m thick are common. A column of 6.7 m of loess, including 12 paleosols, was observed at one site.

The late Quaternary stratigraphic record northwest of Montréal: regional ice-sheet dynamics, ice-stream activity, and early deglacial events

2006 ◽  
Vol 43 (4) ◽  
pp. 461-485 ◽  
Author(s):  
Martin Ross ◽  
Michel Parent ◽  
Beatriz Benjumea ◽  
James Hunter
Keyword(s):  
Late Quaternary ◽  
Late Glacial ◽  
Ice Flow ◽  
Glacial Sediments ◽  
Ice Stream ◽  
Digital Elevation ◽  
Flow Features ◽  
Ice Sheet Dynamics ◽  
Late Wisconsinan ◽  
Elevation Model

The Quaternary sediments of previously unstudied buried valleys and sections near Montréal are analyzed and other sites are revisited to further develop the stratigraphic framework of the St. Lawrence Lowland and to establish regional glacial and deglacial models. The southwest-trending buried valleys were investigated by stratigraphic drilling and high-resolution seismic profiling. The Quaternary succession consists, from base to top, of proximal glaciolacustrine sediments, two superposed till sheets (Argenteuil and Oka tills) of inferred Late Wisconsinan age, and Champlain Sea sediments. The glacial sediments of this sequence record an ice advance toward south (Argenteuil Till) followed by an abrupt ice-flow shift toward the southwest (Oka Till). Compositional and geomorphic data indicate that Oka Till is ubiquitous and is associated with a regional set of glacial landforms. The analysis of a regional digital elevation model in combination with published ice-flow indicators shows convergent flow patterns from the Ottawa–Montréal–Adirondack regions toward the Lake Ontario basin. Landforms produced by the inferred ice stream are locally crosscut by southward-trending ice-flow features. Hence southward flow in the upper St. Lawrence Valley seemingly took place in two distinct contexts: (1) during full glacial conditions, as ice margins stood at or near the late glacial maximum limits, and (2) during late deglaciation, as a post-ice stream reequilibration mechanism. Early deglacial events in the study area were also characterized by subglacial meltwater channelling and erosion along the valleys, subaquatic outwash deposition in glacial Lake Candona, and rapid infill of the valleys during the early stages of the ensuing Champlain Sea.

Stratigraphic, isotopic, and mineralogical evidence for an early Holocene thaw unconformity at Mayo, Yukon Territory

1986 ◽  
Vol 23 (6) ◽  
pp. 794-803 ◽  
Author(s):  
C. R. Burn ◽  
F. A. Michel ◽  
M. W. Smith
Keyword(s):  
Oxygen Isotope ◽  
Average Rate ◽  
Climatic Conditions ◽  
Yukon Territory ◽  
Mackenzie Delta ◽  
Delta Area ◽  
The Holocene ◽  
Oxygen Isotope Ratios ◽  
Abrupt Changes ◽  
Mineralogical Evidence

Ice-rich glaciolacustrine sediments near Mayo, Yukon Territory, reveal a thaw unconformity in the form of truncated ice wedges and abrupt changes in cryotexture. The unconformity has been radiocarbon dated at 8870 ± 200 years BP, which is within the Holocene period of optimal climatic conditions in northern Yukon and the Mackenzie Delta area reported by other workers. Analysis of the mineralogy of the sediments indicates that the material above the unconformity is enriched in minerals that are the products of a more intense weathering environment than those deeper in the profile. Oxygen-isotope ratios of ground ice in the sediments suggest the presence of two genetically distinct ice units above and below the unconformity. An average rate of upward permafrost growth in this area of 0.1–0.2 mm year−1 is calculated for the period since the climatic optimum.

Late Quaternary seismic stratigraphy of the inner shelf seaward of the Tuktoyaktuk Peninsula, Canadian Beaufort Sea

1989 ◽  
Vol 26 (10) ◽  
pp. 1990-2002 ◽  
Author(s):  
Arnaud Héquette ◽  
Philip R. Hill
Keyword(s):  
Sea Level ◽  
Land Surface ◽  
Large Scale ◽  
Late Quaternary ◽  
Lower Boundary ◽  
Beaufort Sea ◽  
Seismic Stratigraphy ◽  
Inner Shelf ◽  
The Holocene ◽  
Late Wisconsinan

This paper describes the seismic stratigraphy of the Quaternary sediments on the inner shelf (< 20 m water depth) of the Canadian Beaufort Sea, seaward of the Tuktoyaktuk Peninsula. Two regional unconformities and three seismic sequences are defined from the high-resolution seismic records. The deeper sequence (sequence III) is characterized by large-scale cross-beds. This sequence has been correlated with the Tingmiark Sand lithostratigraphic unit, which was previously defined farther offshore and is thought to be a glaciofluvial unit deposited during lower-than-present sea-level conditions in the Late Wisconsinan. The lower boundary of the overlying sequence (sequence II) is an unconformity (u/c 2), interpreted as the pre-transgression land surface. Sequence II is discontinuous and consists of localized basin-fill and channel-fill units. Most of these are remnants of thermokarst lakes partially eroded during the Holocene transgression. This sequence is separated from the uppermost sequence (sequence I) by another unconformity (u/c 1), which is the shoreface erosion surface generated by the Holocene sea-level rise. Sequence I is composed of a transgressive sand sheet overlain, in deeper areas, by recent marine muds. Seaward of Hutchison Bay, a large subbottom depression within sequence III in interpreted as a Late Wisconsinan fluviatile channel. According to our seismic interpretation, the Tuk Phase morainal and glaciofluvial deposits existing onland on the Tuktoyaktuk Peninsula, previously assigned to the Early Wisconsinan, would be of Late Wisconsinan age.

The sensitivity of Neotoma to climate change and biodiversity loss over the late Quaternary

2021 ◽  
pp. 1-15
Author(s):  
Catalina P. Tomé ◽  
S. Kathleen Lyons ◽  
Seth D. Newsome ◽  
Felisa A. Smith
Keyword(s):  
Body Size ◽  
Late Quaternary ◽  
Climatic Variability ◽  
Isotope Analysis ◽  
Biodiversity Loss ◽  
Bone Collagen ◽  
Cam Plants ◽  
The Holocene ◽  
Carbon And Nitrogen ◽  
Terminal Pleistocene

Abstract The late Quaternary in North America was marked by highly variable climate and considerable biodiversity loss including a megafaunal extinction event at the terminal Pleistocene. Here, we focus on changes in body size and diet in Neotoma (woodrats) in response to these ecological perturbations using the fossil record from the Edwards Plateau (Texas) across the past 20,000 years. Body mass was estimated using measurements of fossil teeth and diet was quantified using stable isotope analysis of carbon and nitrogen from fossil bone collagen. Prior to ca. 7000 cal yr BP, maximum mass was positively correlated to precipitation and negatively correlated to temperature. Independently, mass was negatively correlated to community composition, becoming more similar to modern over time. Neotoma diet in the Pleistocene was primarily sourced from C3 plants, but became progressively more reliant on C4 (and potentially CAM) plants through the Holocene. Decreasing population mass and higher C4/CAM consumption was associated with a transition from a mesic to xeric landscape. Our results suggest that Neotoma responded to climatic variability during the terminal Pleistocene through changes in body size, while changes in resource availability during the Holocene likely led to shifts in the relative abundance of different Neotoma species in the community.

scholarly journals Cosmogenic nuclide dating of cave sediments in the Eastern Alps and implications for erosion rates

2020 ◽  
Vol 49 (2) ◽  
pp. 107-118
Author(s):  
Philipp Häuselmann ◽  
◽  
Lukas Plan ◽  
Peter Pointner ◽  
Markus Fiebig ◽  
...  
Keyword(s):  
Late Quaternary ◽  
Eastern Alps ◽  
Western Alps ◽  
Valley Bottom ◽  
Cosmogenic Nuclide ◽  
Base Level ◽  
Multi Level ◽  
Slow Evolution ◽  
Karst Systems ◽  
Cosmogenic Nuclide Dating

Karstic caves are created by water eroding and corroding rocks that can be dissolved. Since both the spring areas of caves (normally at the valley bottom) as well as the recharge is controlled by superficial processes, the morphology of the cave bears strong links to these influences. Lowering of local base levels promotes the development of horizontal phreatic cave passages at progressively lower elevations, resulting in the formation of multi-level karst systems. Upon the next lowering of base level, these upper systems become fossilized, and sediment trapped within them may remain preserved for millions of years. Dating these sediments gives clues regarding the time when the passages were last active, and thus may yield age information for old valley floors. The present paper presents cosmogenic nuclide datings of twelve samples from eight caves in the central part of the Northern Calcareous Alps of Austria. Besides three samples that gave no results, most of the obtained ages are at the Mio-Pliocene boundary or within the Pliocene, as was expected before sampling. No multi-level caves could be sampled at different elevations, thus, the obtained valley deepening rates are averages between the age of sediment deposition and the present-day valley floor. However, the valley deepening rates of 0.12 to 0.21 km/Ma are in accordance to previous findings and corroborate a comparatively slow evolution of base level lowering in the Eastern Alps compared to the fast (Late Quaternary) evolution in the Central and Western Alps.

Emmons Lake Volcanic Center, Alaska Peninsula: source of the Late Wisconsin Dawson tephra, Yukon Territory, Canada

2003 ◽  
Vol 40 (7) ◽  
pp. 925-936 ◽  
Author(s):  
Margaret T Mangan ◽  
Christopher F Waythomas ◽  
Thomas P Miller ◽  
Frank A Trusdell
Keyword(s):  
Compositional Data ◽  
Late Quaternary ◽  
Yukon Territory ◽  
Volcanic Center ◽  
Pyroclastic Deposits ◽  
Alaska Peninsula ◽  
Aleutian Arc ◽  
Pumice Flow ◽  
North And South ◽  
The Bering Sea

The Emmons Lake Volcanic Center on the Alaska Peninsula of southwestern Alaska is the site of at least two rhyolitic caldera-forming eruptions (C1 and C2) of late Quaternary age that are possibly the largest of the numerous caldera-forming eruptions known in the Aleutian arc. The deposits produced by these eruptions are widespread (eruptive volumes of >50 km3 each), and their association with Quaternary glacial and eolian deposits on the Alaska Peninsula and elsewhere in Alaska and northwestern Canada enhances the likelihood of establishing geochronological control on Quaternary stratigraphic records in this region. The pyroclastic deposits associated with the second caldera-forming eruption (C2) consist of loose, granular, airfall and pumice-flow deposits that extend for tens of kilometres beyond Emmons Lake caldera, reaching both the Bering Sea and Pacific Ocean coastlines north and south of the caldera. Geochronological and compositional data on C2 deposits indicate a correlation with the Dawson tephra, a 24 000 14C BP (27 000 calibrated years BP), widespread bed of silicic ash found in loess deposits in west-central Yukon Territory, Canada. The correlation clearly establishes the Dawson tephra as the time-stratigraphic marker of the last glacial maximum.

Holocene Prehistory of the Northwestern Subarctic

2016 ◽  
Author(s):  
Ben Potter
Keyword(s):  
British Columbia ◽  
Residential Mobility ◽  
Economic Change ◽  
Yukon Territory ◽  
Current Understanding ◽  
The Holocene ◽  
Cultural Transitions

This chapter synthesizes our current understanding of Holocene prehistory (from 11,500 years ago) of the northwest Subarctic, encompassing Alaska, Yukon Territory, and northern British Columbia. Various cultural chronologies are considered, as are new interpretations based on recently excavated sites. These data indicate conservation of lithic technologies concurrent with economic change throughout the region. Periods of cultural transitions occurred at 6,000 and 1,000 years ago. High residential mobility is inferred for most of the Holocene, with radical shifts in settlement and technology throughout the region at 1,000 years ago, though there are elements of continuity. Current debates on ethnogenesis of Athapaskans and the utility of typological approaches are also discussed.

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