Last glacial–interglacial environments in the southern Rocky Mountains, USA and implications for Younger Dryas-age human occupation

2012 ◽  
Vol 77 (1) ◽  
pp. 96-103 ◽  
Author(s):  
Christy E. Briles ◽  
Cathy Whitlock ◽  
David J. Meltzer
Keyword(s):  
Rocky Mountains ◽  
Fire History ◽  
Younger Dryas ◽  
Late Glacial ◽  
Subalpine Forest ◽  
Glacial Period ◽  
Last Glacial ◽  
Southern Rocky Mountains ◽  
Late Glacial Period ◽  
Fire Activity

The last glacial-interglacial transition (LGIT; 19–9 ka) was characterized by rapid climate changes and significant ecosystem reorganizations worldwide. In western Colorado, one of the coldest locations in the continental US today, mountain environments during the late-glacial period are poorly known. Yet, archaeological evidence from the Mountaineer site (2625 m elev.) indicates that Folsom-age Paleoindians were over-wintering in the Gunnison Basin during the Younger Dryas Chronozone (YDC; 12.9–11.7 ka). To determine the vegetation and fire history during the LGIT, and possible explanations for occupation during a period thought to be harsher than today, a 17-ka-old sediment core from Lily Pond (3208 m elev.) was analyzed for pollen and charcoal and compared with other high-resolution records from the southern Rocky Mountains. Widespread tundra and Picea parkland and low fire activity in the cold wet late-glacial period transitioned to open subalpine forest and increased fire activity in the Bølling–Allerød period as conditions became warmer and drier. During the YDC, greater winter snowpack than today and prolonged wet springs likely expanded subalpine forest to lower elevations than today, providing construction material and fuel for the early inhabitants. In the early to middle Holocene, arid conditions resulted in xerophytic vegetation and frequent fire.

Jura glacial lakes: a paleoclimatic and paleoenvironmental evolution since the Late Glacial Period.

2020 ◽  
Author(s):  
Brahimsamba Bomou ◽  
Damien Zappa ◽  
Anne-Marie Rachoud-Schneider ◽  
Jean-Nicolas Haas ◽  
Marina Gärtner ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Lacustrine Sediments ◽  
Younger Dryas ◽  
Late Glacial ◽  
Glacial Period ◽  
Glacial Lakes ◽  
Late Glacial Period ◽  
Paleoenvironmental Evolution ◽  
Multiproxy Approach

<p>During the retreat of a Würm ice sheet, numerous glacial paleolakes took place in the Swiss and French Jura. Two sites were investigated: the Amburnex Valley site (Switzerland), which evolved in well-developed peatland and the Lake Val (France), which is still persisted as a lacustrine system. During the Late Glacial period, both sites were glacial lakes characterized by a significant accumulation of lacustrine sediments.</p><p>Using a multiproxy approach, this project aims to reconstruct the paleoclimatic and the paleoenvironmental evolution recorded in lacustrine sediments and peatbog deposits since the last 13’000 years.</p><p>The Amburnex core (7m) exhibit a basal morainic deposit from the Würm period, overlain by three meters of lacustrine deposits and four meters of peatland deposits. The Lake Val core (4.5m) consists of the same lithological succession.</p><p>A multiproxy approach based on palynological analyses, grain-size analyses, mineralogical analyses (XRD) and geochemical analyses (TOC, Nitrogen, Phosphorus and Mercury contents; major and trace elements; organic carbon isotopes) have been used to characterize the hydrological and climatic fluctuations, the trophic level and the origin of organic matter in order to reconstruct the paleoenvironmental and paleoclimatic evolution of this area.</p><p>In the Amburnex site, the Bølling-Allerød, the Younger Dryas and the beginning of the Preboreal period have been recognized by palynological analyses and confirmed by carbon 14 dating. During the Oldest Dryas, oligotrophic conditions took place as suggested by the very low concentrations in nitrogen and organic matter. Then, during the warmer Bølling period, an enrichment in total organic carbon (TOC) associated with a decrease in phosphorus content are observed, implying the development of eutrophic conditions and maybe phosphorus recycling. Later in the Allerød period, low TOC and phosphorus contents, associated with varved carbonate deposits, indicate a return to more oligotrophic conditions. New organic matter enrichments are observed in the interval corresponding to the colder Younger Dryas period. These trends are quite consistent with those observed in the Lake Val and reflect significant changes in runoff and nutrient inputs at least at regional scale.</p>

Deglaciation of the central sector of the Cordilleran Ice Sheet in northern British Columbia

2021 ◽  
Author(s):  
Helen Dulfer ◽  
Martin Margold
Keyword(s):  
British Columbia ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Late Glacial ◽  
Glacial Period ◽  
Last Glacial ◽  
Late Glacial Period ◽  
Alpine Glaciers ◽  
Cordilleran Ice Sheet ◽  
The Last Glacial

<p>The Cordilleran Ice Sheet (CIS) repeatedly covered western Canada during the Pleistocene and attained a volume and area similar to that of the present-day Greenland Ice Sheet at the Last Glacial Maximum. Numerical modelling studies of the CIS during the last glacial-interglacial cycle indicate the central sector of this ice sheet, located in mountainous northern British Columbia, played an important role during both the advance and retreat phases. Additionally, the models indicate that the rapid climate oscillations at the end of the Pleistocene had a dramatic effect on the CIS. The abrupt warming at the onset of the Bølling-Allerød caused significant thinning of the ice sheet, resulting in a fifty percent reduction in mass, while the subsequent cooling caused the expansion of alpine glaciers across the former central sector of the CIS. However, the mountainous terrain and remote location have thus far impeded our understanding of this important region of the CIS, and the ice sheet configuration during the Late Glacial remains poorly constrained. </p><p>Here we use the glacial landform record to reconstruct the deglaciation dynamics of the central sector of the CIS during the Late Pleistocene climate reversals. Numerous high elevation meltwater channels suggests the early emergence of mountain peaks above the ice sheet and the configuration of ice marginal landforms, particularly lateral meltwater channels, eskers, kame terraces and ice-contact deltas, allows the westward retreat of the ice margin to be traced towards ice dispersal centres in the Skeena and Coast mountains. Hundreds of arcuate, sharp-crested terminal moraines delineate the extent of alpine glaciers, ice caps and ice fields that regrew on mountain peaks above the CIS and numerical dating indicates that this readvance occurred during the Late Glacial period. Additionally, at some locations, cross-cutting relationships preserve the interaction of the local readvance glaciers with the trunk glaciers of the CIS, allowing the extent of the central sector of the CIS during the Late Glacial period to be reconstructed for the first time.  </p>

The karst of the Vaucluse, an exceptional record for the Last Glacial Maximum (LGM) and the Late-glacial period palaeoenvironment of southeastern France

2014 ◽  
Vol 339-340 ◽  
pp. 41-61 ◽  
Author(s):  
Evelyne Crégut-Bonnoure ◽  
Jacqueline Argant ◽  
Salvador Bailon ◽  
Nicolas Boulbes ◽  
Claude Bouville ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Late Glacial ◽  
Glacial Maximum ◽  
Glacial Period ◽  
Last Glacial ◽  
Late Glacial Period ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Variations in Sediment Yield from the Upper Doubs River Carbonate Watershed (Jura, France) since the Late-Glacial Period

1999 ◽  
Vol 51 (3) ◽  
pp. 267-279 ◽  
Author(s):  
Vincent Bichet ◽  
Michel Campy ◽  
Jean-François Buoncristiani ◽  
Christian Digiovanni ◽  
Michel Meybeck ◽  
...  
Keyword(s):  
Sediment Yield ◽  
Younger Dryas ◽  
Late Glacial ◽  
Glacial Period ◽  
Mean Values ◽  
Seismic Surveys ◽  
Forest Clearing ◽  
Late Glacial Period ◽  
Erosion Processes ◽  
Detrital Sediment

AbstractThe Upper Doubs River Valley is a 910-km2watershed feeding into Lake Chaillexon. The lake was formed by a natural rockfall at the end of the Bølling Chronozone (around 14,250 cal yr B.P.) and since then has trapped material eroded from the watershed. The filling process and variations in sediment yield have been investigated by mechanical coring, seismic surveys, and electric soundings. The detrital sediment yield of the upstream watershed can be calculated by quantifying the sedimentary stocks for each climatic stage of the Late-Glacial period and Holocene Epoch and estimating the lake's entrapment capacity. This enables us to determine the intensity of the erosion processes in relation to climate and environmental factors. The Bølling–Allerød Interstade produced the greatest yields with mean values of 19,500 metric tons per calendar year (t/yr). The Younger Dryas Chronozone saw a sharp fall (8900 t/yr) that continued into the Preboreal (2100 t/yr). Clastic supply increased during the Boreal (4500 t/yr) before declining again in the Early Atlantic (2400 t/yr). Since then, yields have risen from 4500 t/yr in the Late Atlantic to 6800 t/yr in the Subboreal and 11,100 t/yr in the Subatlantic. Comparison of quantitative data with the qualitative analysis of the deposits and with the paleohydrologic curve of the watershed based on level fluctuations in lakes around Chaillexon shows that climate was the controlling factor of sediment yield until the Late Atlantic. From the Late Atlantic–Subboreal around 5400 cal yr B.P. (470014C yr B.P.) and especially from the end of the Subboreal Chronozone and during the Subatlantic Chronozone (2770 cal yr B.P./270014C yr B.P.–present) climatic constraints have been compounded by human activity related to forest clearing and land use.

Progressive glacial retreat in the Southern Altiplano (Uturuncu volcano, 22°S) between 65 and 14 ka constrained by cosmogenic 3He dating

2014 ◽  
Vol 82 (1) ◽  
pp. 209-221 ◽  
Author(s):  
Pierre-Henri Blard ◽  
Jérôme Lave ◽  
Kenneth A. Farley ◽  
Victor Ramirez ◽  
Nestor Jimenez ◽  
...  
Keyword(s):  
Late Pleistocene ◽  
Late Glacial ◽  
Glacial Period ◽  
Tropical Andes ◽  
Equilibrium Line Altitude ◽  
Glacial Retreat ◽  
Late Glacial Period ◽  
Cold Episode ◽  
Glacial Landforms ◽  
Exposure Ages

AbstractThis work presents the first reconstruction of late Pleistocene glacier fluctuations on Uturuncu volcano, in the Southern Tropical Andes. Cosmogenic 3He dating of glacial landforms provides constraints on ancient glacier position between 65 and 14 ka. Despite important scatter in the exposure ages on the oldest moraines, probably resulting from pre-exposure, these 3He data constrain the timing of the moraine deposits and subsequent glacier recessions: the Uturuncu glacier may have reached its maximum extent much before the global LGM, maybe as early as 65 ka, with an equilibrium line altitude (ELA) at 5280 m. Then, the glacier remained close to its maximum position, with a main stillstand identified around 40 ka, and another one between 35 and 17 ka, followed by a limited recession at 17 ka. Then, another glacial stillstand is identified upstream during the late glacial period, probably between 16 and 14 ka, with an ELA standing at 5350 m. This stillstand is synchronous with the paleolake Tauca highstand. This result indicates that this regionally wet and cold episode, during the Heinrich 1 event, also impacted the Southern Altiplano. The ELA rose above 5450 m after 14 ka, synchronously with the Bolling–Allerod.

Postglacial vegetation dynamics at high elevation from Fairy Lake in the northern Greater Yellowstone Ecosystem, Montana, USA

2019 ◽  
Vol 92 (2) ◽  
pp. 365-380 ◽  
Author(s):  
James V. Benes ◽  
Virginia Iglesias ◽  
Cathy Whitlock
Keyword(s):  
Fire History ◽  
Late Glacial ◽  
High Elevation ◽  
Subalpine Forest ◽  
Greater Yellowstone Ecosystem ◽  
Southwestern Montana ◽  
History Of ◽  
Greater Yellowstone ◽  
High Elevations ◽  
Early Late

AbstractThe postglacial vegetation and fire history of the Greater Yellowstone Ecosystem is known from low and middle elevations, but little is known about high elevations. Paleoecologic data from Fairy Lake in the Bridger Range, southwestern Montana, provide a new high-elevation record that spans the last 15,000 yr. The records suggest a period of tundra-steppe vegetation prior to ca. 13,700 cal yr BP was followed by open Picea forest at ca. 11,200 cal yr BP. Pinus-Pseudotsuga parkland was present after ca. 9200 cal yr BP, when conditions were warmer/drier than present. It was replaced by mixed-conifer parkland at ca. 5000 cal yr BP. Present-day subalpine forest established at ca. 2800 cal yr BP. Increased avalanche or mass-wasting activity during the early late-glacial period, the Younger Dryas chronozone, and Neoglaciation suggest cool, wet periods. Sites at different elevations in the region show (1) synchronous vegetation responses to late-glacial warming; (2) widespread xerothermic forests and frequent fires in the early-to-middle Holocene; and (3) a trend to forest closure during late-Holocene cooling. Conditions in the Bridger Range were, however, wetter than other areas during the early Holocene. Across the Northern Rockies, postglacial warming progressed from west to east, reflecting range-specific responses to insolation-driven changes in climate.

scholarly journals Surface profiles and basal shear stresses of outlet glaciers from a Late-glacial mountain ice field in western Scotland

1991 ◽  
Vol 37 (125) ◽  
pp. 77-88 ◽  
Author(s):  
Peter W. Thorp
Keyword(s):  
Late Glacial ◽  
Shear Stresses ◽  
Glacial Period ◽  
Late Glacial Period ◽  
Bedrock Topography ◽  
Pore Water Pressures ◽  
Basal Sliding ◽  
Ice Field ◽  
Surface Profiles ◽  
Basal Shear

Abstract Surface and basal long profiles are reconstructed for 13 outlet glaciers that drained ice from a large ice field (80 km by 120 km) that formed in the western Grampians of Scotland during part of the Late-glacial period (c, 14000–10000years BP). Basal shear stresses are calculated at 5 km intervals along the central flowlines of the reconstructed outlet glaciers. Individual basal shear stresses for the outlet glaciers range from 10 to 204 kPa. Variations in calculated basal shear stresses within and between the glaciers are mainly explained by differences in bedrock topography, extending and compressional flow, and by differences in basal boundary conditions. Low basal shear stresses (<53kPa) calculated for the terminal zones of Creran, Menteith and Lomond glaciers are partly explained by the overriding of glaciomarine clays with inferred high pore-water pressures and a low yield strength that may have led to rapid basal sliding and thinning of the ice lobes.

Sign in / Sign up

Export Citation Format

Share Document