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Soil analyses and terrestrial cosmogenic nuclide exposure dating are combined and a conceptual model proposed to explain altitudinal weathering contrasts in high-latitude highlands. We show that summits in the Torngat and Kaumajet mountains were covered by ice during the Last Glacial Maximum, and that their felsenmeer cover probably survived multiple glaciation events. For similar lithologies, soils on felsenmeer covered summits are signigicantly more weathered than those below the felsenmeer limit, displaying higher concentrations of crystalline iron, amorphous aluminium, and silicium extracted with oxalate. Secondary minerals such as gibbsite and kaolinite occur in felsenmeer soils, whereas those formed in till lacked these secondary minerals. 10 Be and 26 Al exposure ages for nine of ten samples, from high-elevation tors and autochthonous felsenmeer blocks, range from 73 ± 6 to 157 ± 15 ka. By contrast, ages of 11.4 ± 1.0 and 11.7 ± 1.0 ka are measured for bedrock in the much lower Saglek zone, indicating extensive (>3 m) glacial erosion of this zone during Late Wisconsinan glaciation. 26 Al/ 10 Be ratios demonstrate that exposure of the high-elevation surfaces was interrupted during at least one cosmic ray shielding event by either ice or till cover. In either case, Late Wisconsinan glaciers could not have extensively eroded these surfaces. Five erratics dated above the Saglek zone, including one in the felsenmeer zone, have exposure ages ranging from 11.6 ± 1.0 to 13.6 ± 0.7 ka. This indicates that valley and high-elevation ice persisted through the Younger Dryas Chron and provides further evidence that the highlands were not nunataks during the Late Wisconsinan period.Résumé : Des analyses de sols et la datation d'affleurements ayant des nucléides cosmogéniques terrestres sont combinées et un modèle conceptuel est proposé pour expliquer les contrastes d'altération selon l'altitude dans les hautes terres à des latitudes élevées. Nous démontrons que les sommets dans des monts Torngat et Kaumajet étaient couverts par de la glace au cours du dernier maximum glaciaire et que leur couverture de felsenmeer a probablement subi de multiples événements de glaciation. Pour les lithologies semblables, les sols formés dans les zones de felsenmeer sont significativement plus altérés que ceux formés aux plus basses altitudes. Les tills ont des concentrations plus élevées de fer cristallin, d'aluminium amorphe et de silice extraite par oxalate. Les minéraux secondaires tels que la gibbsite et la kaolinite se retrouvent dans les sols des felsenmeers, alors que ceux formés dans le till ne présentent pas ces minéraux secondaires. Les âges d'exposition obtenus par 10 Be et 26 Al, pour neuf des dix échantillons, provenant de roches isolées de haute élévation et de blocs de felsenmeer autochtones, varient de 73 ± 6 à 157 ± 15 ka. Cependant, des âges de 11,4 ± 1,0 ka et de 11,7 ± 1,0 ka sont mesurés pour le socle dans la zone beaucoup plus basse de Saglek, indiquant une forte (>3 m) érosion glaciaire dans cette zone durant la gla...

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During the Holocene, bison (Bison bison) were key components of the Great Plains landscape. This study utilizes serial stable isotope analyses (tooth enamel carbonate) of 29 individuals from five middle Holocene (∽ 7–8.5·ka) archaeological sites to address seasonal variability in movement patterns and grazing behavior of bison populations in the eastern Great Plains. Stable carbon isotopes (δ13C) indicate a bison diet that is similar to the C3/C4 composition of modern tallgrass prairies, while 87Sr/86Sr values generally indicate very little seasonal movement (b50 km) and relatively limited inter-annual movement (b500 km) over the course of 4–5 yr. Analyses of variability in serial stable oxygen isotope samples (δ18O) further substantiate a model of localized bison herds that adhered to upland areas of the eastern Plains and prairie–forest border.

The juxtaposition of wet-based erosive ice in valleys and cold-based, non-erosive ice atop felsenmeer-covered interfluve plateaus has generated relief in the Torngat Mountains of northeastern Canada. Measurements of in situ terrestrial cosmogenic nuclide (TCN) concentrations from 31 bedrock sites, coupled with soils and geomorphology, indicate that erosion of the valleys has been > > > > >2 m during a single glacial-interglacial cycle. However, on summit plateaus the long-term (over several glacial-interglacial cycles) erosion rate is < < < < <1·4 m Ma. TCN ratios reveal that the exposure plus ice-cover history retained on some summit surfaces probably spans more than 800 ka despite complete ice cover as recently as 11 ka. A thermodynamic ice sheet model with a basal water calculation is used to calculate the sliding distance normalized by the duration of ice cover for the region. We formulate a general glacial erosion rule for the Torngat Mountains, which correlates TCN-derived erosion rates for terrain once partially covered by cold-based ice with modelled average ice basal sliding velocities. Erosion rates vary linearly with average sliding velocity by a glacial erosion coefficient of 5 × × × × × 10. Due to the significant distribution of cold-based ice cover in this high latitude region, our estimates of net regional glacial erosion and glacial erosion coefficient are orders of magnitude lower than a previously published value.

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