The micromorphology of loess‐paleosol sequences in central Alaska: A new perspective on soil formation and landscape evolution since the Late Glacial period (c. 16,000 cal yr BP to present)

2020 ◽  
Vol 35 (5) ◽  
pp. 701-728
Author(s):  
Jennifer Kielhofer ◽  
Christopher Miller ◽  
Joshua Reuther ◽  
Charles Holmes ◽  
Ben Potter ◽  
...  
Keyword(s):  
Landscape Evolution ◽  
Soil Formation ◽  
Late Glacial ◽  
Glacial Period ◽  
Late Glacial Period ◽  
New Perspective

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.

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.

Late-glacial deposits at Llyn Dwythwch and Nant Ffrancon, Caernarvonshire

1962 ◽  
Vol 244 (716) ◽  
pp. 459-481 ◽  
Keyword(s):  
Vegetation History ◽  
Late Glacial ◽  
Glacial Period ◽  
Late Glacial Period ◽  
Lacustrine Deposits ◽  
Kettle Hole ◽  
Lycopodium Annotinum ◽  
Northern Distribution ◽  
History Of ◽  
Zone Ii

The stratigraphy of sediments in two lake basins in the Caernarvonshire mountains at 600 and 900 ft. O.D. is described and it is shown that the basal layers were deposited in the Late-glacial Period. The deposits of a third site occupying a kettle-hole in morainic gravels at 1223 ft. O.D. are described and here the Late-glacial Period is not represented. The relation of these sites to the youngest corrie moraines of the district indicates that the latter were formed during the post-Allerod climatic regression (Zone III). The vegetation history of the district was studied by means of pollen analysis of lacustrine deposits from the two first-mentioned sites (above). The vegetation of the Late-glacial Period at first formed tundra (Zone I) in which arctic-alpines, notably Betula , flourished together with species of oceanic and oceanic-northern distribution and calcicolous, eutrophic and moderately thermophilous plants. The spread of juniper scrub preceded the arrival of tree birches, which form ‘park-tundra’ in Zone II at Nant Ffrancon but failed to grow as high as Llyn Dwythwch. The birch ‘ parktundra’ is considered to have covered Britain south of the Forth-Clyde at low altitudes and to have occupied central and eastern Ireland at this time. The climatic deterioration of Zone III is clearly registered by the decline of juniper and tree birch and the local severity of conditions is demonstrated by the increased abundance of the chianophilous fern, Cryptogramma crispa, Lycopodium selago, Saussurea alpina and other montane herbs. The extensive occurrence of solifluxion, augmented by glacier streams, brought down silt and clay into the lakes. The ensuing amelioration in climate and the course of forest development through the Post-glacial Period is briefly traced and the persistence of certain elements of the present mountain flora from the Late-glacial Period demonstrated. A description is given of the spores of Cryptogramma crispa which together with Lycopodium annotinum and Saussurea alpina are new to British Late-glacial records.

Local and regional vegetation change on the northeastern Olympic Peninsula during the Holocene

1995 ◽  
Vol 73 (10) ◽  
pp. 1618-1627 ◽  
Author(s):  
J. S. McLachlan ◽  
L. B. Brubaker
Keyword(s):  
Late Holocene ◽  
Vegetation History ◽  
Late Glacial ◽  
Early Holocene ◽  
Thuja Plicata ◽  
Alnus Rubra ◽  
Glacial Period ◽  
Olympic Peninsula ◽  
The Holocene ◽  
Late Glacial Period

The postglacial vegetation history of the northeastern Olympic Peninsula was investigated at different spatial scales by comparing the pollen, macrofossil, and charcoal records from a low elevation lake (Crocker Lake) and a nearby forested swamp (Cedar Swamp). The regional pollen record from Crocker Lake revealed a parkland of coniferous species with divergent modern ecological tolerances, including Pinus contorta, Picea sitchensis, and Abies lasiocarpa during the late glacial period (~ 13 000 – 10 000 BP). Disturbance-adapted species such as Alnus rubra and Pseudotsuga menziesii dominated forests during the early Holocene (10 000 – 7000 BP). Modern forests containing mesic late-successional species such as Tsuga heterophylla and Thuja plicata were established during the late Holocene (7000 BP to present). During the late glacial period, the local vegetation at Cedar Swamp was dominated by Alnus sinuata. Hydrologic changes resulted in the establishment of a deep marsh during the early Holocene. Hydrosere succession from an open aquatic environment to a forested wetland and disturbance-mediated alternations between Thuja plicata and Alnus rubra characterized the local vegetation during the late Holocene. Throughout the Holocene, the vegetation of the northeastern Olympic Peninsula was governed by broad climatic and physiographic parameters at the regional scale and the effects of local geomorphologic constraints and disturbance history at the finer landscape scale. Key words: fossil pollen, vegetation history, Olympic Peninsula, Quaternary.

Glacier fluctuations in the southern Peruvian Andes during the late-glacial period, constrained with cosmogenic 3 He

2011 ◽  
Vol 26 (1) ◽  
pp. 37-43 ◽  
Author(s):  
Gordon R.M. Bromley ◽  
Brenda L. Hall ◽  
Joerg M. Schaefer ◽  
Gisela Winckler ◽  
Claire E. Todd ◽  
...  
Keyword(s):  
Late Glacial ◽  
Glacial Period ◽  
Peruvian Andes ◽  
Late Glacial Period ◽  
Glacier Fluctuations
Sign in / Sign up

Export Citation Format

Share Document