scholarly journals Geomorphological Investigations in the Torngat Mountains of Northeastern Labrador-Ungava

ARCTIC ◽  
1957 ◽  
Vol 10 (4) ◽  
pp. 243
Author(s):  
J.D. Ives
Keyword(s):  
North America ◽  
Sea Level ◽  
Late Pleistocene ◽  
Final Stage ◽  
Central Area ◽  
Interglacial Period ◽  
Glacial Period ◽  
The West ◽  
Ice Cap ◽  
Considerable Intensity

... The central area of study lay athwart the Labrador-Quebec boundary on the watershed between Nakvak Brook, which drains into Saglek Fiord, and the Koroksoak (Korok) River, which flows westwards into Ungava Bay. ... Attention was concentrated on an extensive system of lateral moraines and kame terraces which slope eastwards from the watershed towards the head of Saglek Fiord. Similar systems were examined in the through-troughs to the south. The whole complex represents the late-Pleistocene limits of trunk glaciers flowing through the mountains towards the east and supplied by an ice cap of continental proportions west of the height of land. At this stage the higher summits stood as nunataks well above the level of the ice, and an extensive series of ice-dammed lakes was held against the western slopes of the highland finding outlets over ice-free cols into the Atlantic. Detailed studies in the watershed area provide a chronology of the final emergence of the area from the last ice sheet, and the draining of the ice-dammed lakes. A final stage was represented by a mass of ice in the lower valley of the Koroksoak which dammed a lake to the level of the col, at 1,050 feet, whence it drained into Nakvak Brook and ultimately into the Atlantic. Glacial erratics, found on summits up to 4,000 feet above sea level, corroborate the conclusions of the previous summer's work suggesting that at some stage the highest summits were inundated by ice flowing from the west. The data compiled from the two summers' work prompt the conclusion that during late-Pleistocene times the Torngat Mountains were influenced by two distinct glaciations, separated by an interglacial period of considerable intensity. The final glaciation, during which large areas remained ice-free, is tentatively correlated with the "classical" Wisconsin of central North America whereas the date of the preceding glacial period is uncertain. It may be the equivalent of the Illinoian Glaciation, or even be of post-Sangamon age, and in this case be comparable with a cold phase tentatively identified in central North America, which is older than the "classical" Wisconsin Glaciation, and is separated from the latter by a warmer period. Reconnaissance from the air during flights along the Labrador coast and some distance inland suggests that these general conclusions might well be applicable to the entire coastal zone of Labrador. ...

Climatic implications of latest Pleistocene and earliest Holocene mammalian sympatries in eastern Washington state, USA

2008 ◽  
Vol 70 (3) ◽  
pp. 426-432 ◽  
Author(s):  
R. Lee Lyman
Keyword(s):  
North America ◽  
Late Pleistocene ◽  
Rocky Mountains ◽  
Taxonomic Composition ◽  
Washington State ◽  
The West ◽  
Mammalian Faunas ◽  
Eastern Washington

AbstractFor more than fifty years it has been known that mammalian faunas of late-Pleistocene age are taxonomically unique and lack modern analogs. It has long been thought that nonanalog mammalian faunas are limited in North America to areas east of the Rocky Mountains and that late-Pleistocene mammalian faunas in the west were modern in taxonomic composition. A late-Pleistocene fauna from Marmes Rockshelter in southeastern Washington State has no modern analog and defines an area of maximum sympatry that indicates significantly cooler summers than are found in the area today. An earliest Holocene fauna from Marmes Rockshelter defines an area of maximum sympatry, including the site area, but contains a single tentatively identified taxon that may indicate slightly cooler than modern summers.

scholarly journals East Greenland ice core dust record reveals timing of Greenland ice sheet advance and retreat

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Marius Folden Simonsen ◽  
Giovanni Baccolo ◽  
Thomas Blunier ◽  
Alejandra Borunda ◽  
Barbara Delmonte ◽  
...  
Keyword(s):  
Sea Level ◽  
Ice Core ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Interglacial Period ◽  
Last Deglaciation ◽  
Glacial Cycle ◽  
East Greenland ◽  
Ice Cap ◽  
Climate Forcings

Abstract Accurate estimates of the past extent of the Greenland ice sheet provide critical constraints for ice sheet models used to determine Greenland’s response to climate forcing and contribution to global sea level. Here we use a continuous ice core dust record from the Renland ice cap on the east coast of Greenland to constrain the timing of changes to the ice sheet margin and relative sea level over the last glacial cycle. During the Holocene and the previous interglacial period (Eemian) the dust record was dominated by coarse particles consistent with rock samples from central East Greenland. From the coarse particle concentration record we infer the East Greenland ice sheet margin advanced from 113.4 ± 0.4 to 111.0 ± 0.4 ka BP during the glacial onset and retreated from 12.1 ± 0.1 to 9.0 ± 0.1 ka BP during the last deglaciation. These findings constrain the possible response of the Greenland ice sheet to climate forcings.

scholarly journals Evidence for the Timing and Duration of the Last Interglacial Period from High-Precision Uranium-Series Ages of Corals on Tectonically Stable Coastlines

2002 ◽  
Vol 58 (1) ◽  
pp. 36-40 ◽  
Author(s):  
Daniel R. Muhs
Keyword(s):  
Sea Level ◽  
High Precision ◽  
Interglacial Period ◽  
Glacial Period ◽  
Present Level ◽  
Last Interglacial ◽  
The Bahamas ◽  
Last Glacial Period ◽  
Last Interglacial Period ◽  
The Last Glacial

AbstractThe last interglacial period has a timing and duration that can be estimated from U-series dating of emergent, coral-bearing deposits on tectonically stable coastlines. High-precision dating from Bermuda, the Bahamas, Hawaii, and Australia suggests that the last interglacial period had a sea level at least as high as present from ∼128,000 to 116,000 yr B.P. Sea level reached a near-present level more quickly after the close of the penultimate glacial period than at the close of the last glacial period and the duration of high sea level is longer than that implied by the deep-sea record.

scholarly journals The formation of the West European Rift; a new model as exemplified by the Massif Central area

2001 ◽  
Vol 172 (2) ◽  
pp. 213-221 ◽  
Author(s):  
Olivier Merle ◽  
Laurent Michon
Keyword(s):  
Sea Level ◽  
Central Area ◽  
Rift System ◽  
The South ◽  
The West ◽  
Massif Central ◽  
New Model ◽  
The North ◽  
Crustal Thinning ◽  
West European

Abstract In this paper, we use mainly field data from the Massif Central area, which have been presented in a companion paper [Michon and Merle, 2001], to discuss the origin and the evolution of the West European Rift system. It is shown that the tectonic event in the Tertiary is two-stage. The overall geological evolution reveal a tectonic paradox as the first stage strongly suggests passive rifting, whereas the second stage displays the first stage of active rifting. In the north, crustal thinning, graben formation and sedimentation at sea level without volcanism during the Lower Oligocene, followed by scattered volcanism in a thinned area during Upper Oligocene and Lower Miocene, represent the classical evolution of a rift resulting from extensional stresses within the lithosphere (i.e. passive rifting). In the south, thinning of the lithospheric mantle associated with doming and volcanism in the Upper Miocene, together with the lack of crustal thinning, may be easily interpreted in terms of the first stage of active rifting due to the ascent of a mantle plume. This active rifting process would have been inhibited before stretching of the crust, as asthenospheric rise associated with uplift and volcanism are the only tectonic events observed. The diachronism of these two events is emphasized by two clearly distinct orientations of crustal thinning in the north and mantle lithospheric thinning in the south. To understand this tectonic paradox, a new model is discussed taking into account the Tertiary evolution of the Alpine chain. It is shown that the formation of a deep lithospheric root may have important mechanical consequences on the adjacent lithosphere. The downward gravitational force acting on the descending slab may induce coeval extension in the surrounding lithosphere. This could trigger graben formation and laguno-marine sedimentation at sea level followed by volcanism as expected for passive rifting. Concurrently, the descending lithospheric flow induces a flow pattern in the asthenosphere which can bring up hot mantle to the base of the adjacent lithosphere. Slow thermal erosion of the base of the lithosphere may lead to a late-stage volcanism and uplift as expected for active rifting.

scholarly journals Fossil and genomic evidence constrains the timing of bison arrival in North America

2017 ◽  
Vol 114 (13) ◽  
pp. 3457-3462 ◽  
Author(s):  
Duane Froese ◽  
Mathias Stiller ◽  
Peter D. Heintzman ◽  
Alberto V. Reyes ◽  
Grant D. Zazula ◽  
...  
Keyword(s):  
North America ◽  
Sea Level ◽  
Late Pleistocene ◽  
North American ◽  
Marine Isotope Stage ◽  
Mitochondrial Genomes ◽  
Subsequent Evolution ◽  
Large Mammal ◽  
Morphological Diversification ◽  
Steppe Bison

The arrival of bison in North America marks one of the most successful large-mammal dispersals from Asia within the last million years, yet the timing and nature of this event remain poorly determined. Here, we used a combined paleontological and paleogenomic approach to provide a robust timeline for the entry and subsequent evolution of bison within North America. We characterized two fossil-rich localities in Canada’s Yukon and identified the oldest well-constrained bison fossil in North America, a 130,000-y-old steppe bison, Bison cf. priscus. We extracted and sequenced mitochondrial genomes from both this bison and from the remains of a recently discovered, ∼120,000-y-old giant long-horned bison, Bison latifrons, from Snowmass, Colorado. We analyzed these and 44 other bison mitogenomes with ages that span the Late Pleistocene, and identified two waves of bison dispersal into North America from Asia, the earliest of which occurred ∼195–135 thousand y ago and preceded the morphological diversification of North American bison, and the second of which occurred during the Late Pleistocene, ∼45–21 thousand y ago. This chronological arc establishes that bison first entered North America during the sea level lowstand accompanying marine isotope stage 6, rejecting earlier records of bison in North America. After their invasion, bison rapidly colonized North America during the last interglaciation, spreading from Alaska through continental North America; they have been continuously resident since then.

scholarly journals Environmental Constraints on West Antarctic Ice-Sheet Formation

1987 ◽  
Vol 33 (115) ◽  
pp. 346-356 ◽  
Author(s):  
D.R. Lindstrom ◽  
D.R. MacAyeal
Keyword(s):  
Sea Level ◽  
Environmental Influence ◽  
Accumulation Rate ◽  
Ice Sheet ◽  
Interglacial Period ◽  
Last Interglacial ◽  
The West ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
West Antarctic

AbstractSmall perturbations in Antarctic environ-mental conditions can culminate in the demise of the Antarctic ice sheet’s western sector. This may have happened during the last interglacial period, and could recur within the next millennium due to atmospheric warming from trace gas and CO2increases. In this study, we investigate the importance of sea-level, accumulation rate, and ice influx from the East Antarctic ice sheet in the re-establishment of the West Antarctic ice sheet from a thin cover using a time-dependent numerical ice-shelf model. Our results show that a precursor to the West Antarctic ice sheet can form within 3000 years. Sea-level lowering caused by ice-sheet development in the Northern Hemisphere has the greatest environmental influence. Under favorable conditions, ice grounding occurs over all parts of the West Antarctic ice sheet except up-stream of Thwaites Glacier and in the Ross Sea region.

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