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Abstract: Controversy persists in western Newfoundland regarding Pleistocene, particularly Late Wisconsinan, glacial ice volumes. Independently, a set of alpine glacial deposits on the flanks of the Tablelands in Gros Morne [...]

Abstract: Light detection and ranging (LIDAR) is an emerging technology to generate high-resolution digital elevation models (DEMs). Subtle topographical differences among three flow units of the Jurassic North Mountain Basalt, [...]

We assessed annual home-range area for 23 adult, resident American martens (Martes americana atrata) in a low-density population in eastern Newfoundland, Canada (1996-2003), and evaluated seasonal habitat requirements during a peak in abundance of snowshoe hares (Lepus americanus). Home-range estimates were 29.54 [km.sup.2] and 15.19 [km.sup.2] for males and females, respectively, and reflect significantly larger territories than those maintained by martens across most of their geographic range. We suggest that these exceptionally large territories reflect the low diversity and abundance of small mammals available to martens as prey. Seasonal requirements were examined by using an index to home-range area. The relationship between the index and snowshoe hare abundance indicated that movement rates of individuals decreased during winters when snowshoe hares were abundant, but that this relationship was not apparent during summer. Analyses of stand-scale habitat use indicated that mature coniferous forest was the dominant cover type in most home ranges (49.6% of area) and was the only forest type used proportionately more than its availability by resident martens. Other forest types used in proportion to their availability included coniferous scrub and insect-defoliated stands. Open areas and sites recently disturbed by fire were avoided at this scale. Key words: American marten, habitat use, home range, Martes americana, Newfoundland, prey abundance

Reliable chronology of sediment landforms is required to establish rates for a wide range of pedogenic and geologic processes. Cosmogenic nuclide depth profile exposure dating provides a useful means of [...]

Glacial erosion exerts a dominant control on the earth's terrestrial landscape. Through the excavation of material, glacial erosion plays a fundamental role in mountain range exhumation, isostatic processes, and biogeochemical [...]

The late Miocene and Pliocene Beaufort Formation and equivalent units throughout the Canadian Arctic Archipelago captured a rich record of landscape evolution, Arctic paleoclimatology, and paleo-ecosystem changes caused by a [...]

Deglaciation of the northwestern Laurentide Ice Sheet in the central Mackenzie Valley opened the northern portion of the deglacial Ice-Free Corridor between the Laurentide and Cordilleran ice sheets and a drainage route to the Arctic Ocean. In addition, ice-sheet saddle collapse in this section of the Laurentide Ice Sheet has been implicated as a mechanism for delivering substantial freshwater influx into the Arctic Ocean on centennial timescales. However, there is little empirical data to constrain the deglaciation chronology in the central Mackenzie Valley where the northern slopes of the ice saddle were located. Here, we present 30 new 10Be cosmogenic nuclide exposure dates across six sites, including two elevation transects, which constrain the timing and rate of thinning of the Laurentide Ice Sheet from the area. Our new 10Be dates indicate that the initial deglaciation of the eastern summits of the central Mackenzie Mountains began at ~15.8 ka (17.1 - 14.6 ka), ~1,000 years earlier than previous reconstructions. The main phase of ice-saddle collapse occurred between ~14.9 and 13.2 ka, consistent with numerical modelling simulations, placing this event within the Bølling-Allerød interval (14.6 - 12.9 ka). Our new dates require a revision of ice margin retreat dynamics, with ice retreating more easterly rather than southward along the Mackenzie Valley. In addition, we quantify a total sea level rise contribution from the Cordilleran-Laurentide ice saddle region of ~11.2 m between 16 ka and 13 ka. [ABSTRACT FROM AUTHOR]

We measured cosmogenic 36Cl in 56 samples from boulders on moraines and fluvial terraces in the vicinity of the Wind River Range, Wyoming. We also measured 10Be in 10 of the same samples. Most of the 10Be ages were in good agreement with the 36Cl ages, indicating that rock-surface erosion rates were very low. The oldest moraine investigated, the type Sacagewea Ridge site, yielded only a limiting minimum age of >232 ka. The oldest moraines in the type Bull Lake complex also could be constrained only to >130 ka. The main sequence of type Bull Lake moraines yielded age distributions indicating deposition within the intervals 130 to 100 ka and 120 to 100 ka; the best estimates are closer to the upper limits of these ranges, and associated uncertainties are in the range of 10% to 15%. These uncertainties could permit deposition in either marine isotope stage 6 or stage 5d. We found no evidence of glacial deposits dating to marine isotope stage 4. Both Bull Lake-age moraines from Fremont Lake. on the opposite side of the Wind River Range, and boulders on a fluvial terrace above the Wind River, gave age distributions very similar to that of the second oldest Bull Lake advance (ca. 130 to 100 ka). The distribution of boulder ages for Pinedale moraines at Bull Lake indicated deposition between 23 and 16 ka, nearly identical to the distribution of 10Be ages previously reported for the type Pinedale moraines at Fremont Lake.

Oversteepened valley walls in western Norway have high recurrences of Holocene rock-slope failure activity causing significant risk to communities and infrastructure. Deposits from six to nine catastrophic rock-slope failure (CRSF) events are preserved at the base of the Mannen rock-slope instability in the Romsdal Valley, western Norway. The timing of these CRSF events was determined by terrestrial cosmogenic nuclide dating and relative chronology due to mapping Quaternary deposits. The stratigraphical chronology indicates that three of the CRSF events occurred between 12 and 10 ka, during regional deglaciation. Congruent with previous investigations, these events are attributed to the debuttressing effect experienced by steep slopes following deglaciation, during a period of paraglacial relaxation. The remaining three to six CRSF events cluster at 4.9 ± 0.6 ka (based on 10 cosmogenic 10Be samples from boulders). CRSF events during this later period are ascribed to climatic changes at the end of the Holocene thermal optimum, including increased precipitation rates, high air temperatures and the associated degradation of permafrost in rock-slope faces. Geomorphological mapping and sedimentological analyses further permit the contextualisation of these deposits within the overall sequence of post-glacial fjord-valley infilling. In the light of contemporary climate change, the relationship between CRSF frequency, precipitation, air temperature and permafrost degradation may be of interest to others working or operating in comparable settings. [ABSTRACT FROM AUTHOR]

Understanding topographic relief evolution and its changes over hundreds of thousands to million-year timescales remains challenging. Recent approaches usually combine numerical modelling of terrestrial cosmogenic nuclide (TCN) exposure ages on strath terraces, exhumation histories based on thermochronology, drainage basin evolution, and basin stratigraphy. However, even when combined, these methods are unable to measure the rate changes with precisions needed to differentiate climate from tectonic drivers over multiple glacial cycles and longer timescales. Muon-paleotopometry is a new approach that may address the methodological gap of determining relief generation. Muon-paleotopometry utilizes the dependence of cosmic ray muon flux on crustal shielding depth. The spatial pattern of concentrations of multiple muon-induced TCN measured along a near-horizontal transect under valleys and peaks relates directly to the history of changes (positive or negative) in crustal thickness. It enables paleotopometry above the sample datum over an isotope-specific monitoring duration. By sampling at depths of hectametres, long-lived TCNs are not sensitive to minor short-term (<105 yr) changes owing to cut and fill terraces or transgressions for instance, but short-lived isotopes may provide constraints on this. The method uses concentrations differences among samples, so is not significantly impacted by limitations in knowledge of muon flux and interactions at those depths. Early proof of concept investigations at Dalhousie by student thesis work in 2017 provided encouraging results to allow for the current large-scale relief investigation of the European Alps. [ABSTRACT FROM AUTHOR]