Paleomagnetic evidence for late Cenozoic glaciations in the Mackenzie Mountains of the Northwest Territories, Canada

1996 ◽  
Vol 33 (6) ◽  
pp. 896-903 ◽  
Author(s):  
R. W. Barendregt ◽  
R. J. Enkin ◽  
J. Baker ◽  
A. Duk-Rodkin
Keyword(s):  
Large Scale ◽  
Magnetic Measurements ◽  
Laurentide Ice Sheet ◽  
Paleoenvironmental Reconstruction ◽  
Pleistocene Glaciations ◽  
Late Cenozoic ◽  
Last Glaciation ◽  
Stratigraphic Record ◽  
Bear River ◽  
Mackenzie Mountains

The Mackenzie Mountains were affected by montane valley glaciers during the Pleistocene and peripherally by the Laurentide Ice Sheet during the last glaciation. In this paper we report on magnetostratigraphic dating and correlation of three sections recording Late Pliocene to Late Pleistocene glaciations: Katherine Creek, Little Bear River, and Inlin Brook (located around 65°N, 127°W). Each section consists of a colluvial unit overlying a Pliocene pediment surface cut into Proterozoic or Paleozoic bedrock, or Tertiary gravel, which is in turn overlain by a stack of five, and in places six, montane tills, usually with soils developed at their surfaces, and capped by a Laurentide till. Normal and reversed magnetizations were recognized with single-domain magnetite as a dominant remanence carrier. The Katherine Creek section has a normally magnetized colluvium at its base, which is overlain by two reversed tills, succeeded by three normal tills. We interpret the top two tills to be of Brunhes age (< 780 ka) but argue that the lowermost normal till is of probable Olduvai age (ca. 1.8 Ma). The two underlying tills are of Matuyama age (2.6 Ma to 780 ka), and the colluvial base is assigned to the Gauss (3.5–2.6 Ma). The Little Bear River section exposes a stratigraphic record similar to that found at Katherine Creek. Only four units could be assigned a paleomagnetic polarity, the others yielding incoherent results. Paleosols on the first and second till units were reversed and normal, respectively, and the top till was normal. Thus there is clear evidence of an older (reversed) Pleistocene glaciation and a magnetostratigraphic record compatible with that found at Katherine Creek. Magnetic measurements from Inlin Brook gave largely incoherent results, with the exception of the surface (Laurentide) till, which is normal. The glacial history recorded in the Mackenzie Mountains correlates well with other studies carried out in the Cordillera. The large-scale changes in climate revealed in these terrestrial records provide baseline data for paleoenvironmental reconstruction.

scholarly journals Age Relationships of Laurentide and Montane Glaciations, Mackenzie Mountains, Northwest Territories

2007 ◽  
Vol 45 (1) ◽  
pp. 79-90 ◽  
Author(s):  
Alejandra Duk-Rodkin ◽  
Owen L. Hughes
Keyword(s):  
Northwest Territories ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Mountain Front ◽  
Bear River ◽  
Mackenzie Mountains ◽  
Late Wisconsinan

ABSTRACT The Mackenzie Mountains were glaciated repeatedly by large valley glaciers that emanated from the Backbone Ranges, and by much smaller valley glaciers that emanated from peaks in the Canyon Ranges. During the Late Wisconsinan the Laurentide Ice Sheet reached its all-time maximum position. The ice sheet pressed against the Canyon Ranges and moved up major valleys causing the diversion of mountain waters and organizing a complex meltwater system that drained across mountain interfluve areas towards the northwest. Two ages of moraines deposited by montane glaciers occur widely in the Mackenzie Mountains. Near the mountain front certain of the older moraines have been truncated by the Laurentide Ice Sheet, and others have been incised by meltwater streams emanating from the Laurentide ice margin, indicating that these older moraines predate the maximum Laurentide advance. Locally, certain of the younger montane moraines breach moraines and other ice marginal features of the Laurentide maximum, indicating that the younger montane glaciation post-dated the Laurentide maximum. Some large montane glaciers extended out from the mountains to merge with the retreating Laurentide Ice Sheet. There are several localities that display the age relationships between montane and Laurentide glaciations such as Dark Rock Creek, Durkan-Lukas Valley, Little Bear River and Katherine Creek. The older of the local montane glaciations is correlated tentatively with Reid Glaciation (lllinoian?) of central Yukon, and the younger with the Late Wisconsinan McConnell Glaciation. The Laurentide Glaciation is correlated with Hungry Creek Glaciation of Bonnet Plume Depression, which probably culminated about 30,000 years ago or somewhat later.

Pleistocene stratigraphy, paleopedology, and paleoecology of a multiple till sequence exposed on the Little Bear River, Western District of Mackenzie, N.W.T., Canada

1993 ◽  
Vol 30 (4) ◽  
pp. 851-866 ◽  
Author(s):  
O. L. Hughes ◽  
C. Tarnocai ◽  
C. E. Schweger
Keyword(s):  
Transition Zone ◽  
Ice Sheet ◽  
Climatic Conditions ◽  
Canadian Shield ◽  
Laurentide Ice Sheet ◽  
Spruce Forest ◽  
River Section ◽  
Valley Glacier ◽  
Bear River ◽  
Late Wisconsinan

The Little Bear River section lies in a transition zone between Mackenzie Lowland and Canyon Ranges of Mackenzie Mountains. Within the transition zone, the maximum extent of the Laurentide ice sheet overlaps the former extent of montane glaciers that emanated from the higher parts of Canyon Ranges or from the still higher Backbone Ranges to the southwest. Five montane tills, each with a paleosol developed in its upper part, indicate five separate glaciations during each of which a valley glacier emanating from the headwaters of Little Bear River extended eastward into the transition zone. The uppermost of the montane tills is overlain by boulder gravel containing rocks of Canadian Shield origin deposited by the Laurentide ice sheet.Solum and B horizon depths, red colours, and lack of leaching and cryoturbation indicate that although each successive interglacial interval was cooler than the preceding one, even the last of the intervals was warmer than the Holocene. Climatic conditions during one of the intervals inferred from the paleobotanic data, particularly spruce forest development, are consistent with conditions inferred from the associated paleosol.The uppermost of the montane tills is thought to correlate with till of Reid (Illinoian) age in central Yukon. The paleosol developed on that till is, accordingly, thought to correlate with the Diversion Creek paleosol developed on drift of Reid age. The Laurentide boulder gravel is assigned to a stade of Hungry Creek Glaciation of Late Wisconsinan age. The Laurentide ice sheet reached its apparent all-time western limit during the Hungry Creek Glaciation maximum.

Dating Early and Middle (Reid) Pleistocene Glaciations in Central Yukon by Tephrochronology

2001 ◽  
Vol 56 (3) ◽  
pp. 335-348 ◽  
Author(s):  
John A. Westgate ◽  
Shari J. Preece ◽  
Duane G. Froese ◽  
Robert C. Walter ◽  
Amanjit S. Sandhu ◽  
...  
Keyword(s):  
Gulf Of Alaska ◽  
Supporting Evidence ◽  
Pleistocene Glaciations ◽  
Late Cenozoic ◽  
Aeolian Sand ◽  
Oxygen Isotope Stage ◽  
Aleutian Arc ◽  
Dawson City ◽  
Cordilleran Ice Sheet ◽  
Tephra Beds

AbstractThe late Cenozoic deposits of central Yukon contain numerous distal tephra beds, derived from vents in the Wrangell Mountains and Aleutian arc–Alaska Peninsula region. We use a few of these tephra beds to gain a better understanding on the timing of extensive Pleistocene glaciations that affected this area. Exposures at Fort Selkirk show that the Cordilleran Ice Sheet advanced close to the outer limit of glaciation about 1.5 myr ago. At the Midnight Dome Terrace, near Dawson City, exposed outwash gravel, aeolian sand, and loess, related to valley glaciers in the adjacent Ogilvie Mountains, are of the same age. Reid glacial deposits at Ash Bend on the Stewart River are older than oxygen isotope stage (OIS) 6 and likely of OIS 8 age, that is, about 250,000 yr B.P. Supporting evidence for this chronology comes from major peaks in the rates of terrigeneous sediment input into the Gulf of Alaska at 1.5 and 0.25 myr B.P.

Estimating the regional climate signal in a late Pleistocene and early Holocene lake-sediment δ18O record from Vermont, USA.

2016 ◽  
Vol 86 (1) ◽  
pp. 67-78 ◽  
Author(s):  
Maximilian Benedict Mandl ◽  
Bryan Nolan Shuman ◽  
Jeremiah Marsicek ◽  
Laurie Grigg
Keyword(s):  
Oxygen Isotope ◽  
Large Scale ◽  
Regional Climate ◽  
Principal Component ◽  
Early Holocene ◽  
Laurentide Ice Sheet ◽  
Oceanic Circulation ◽  
Climate Signal ◽  
Local Character ◽  
Climate Reconstructions

AbstractWe present a new oxygen isotope (δ18O) record from carbonate-rich lake sediments from central Vermont. The record from Twin Ponds spans from 13.5 cal ka BP (1950 AD) to present, but contains a 6 ka long hiatus starting shortly after 7.5 cal ka BP. We compare the record for ca. 13.5–7.5 cal ka BP with published δ18O data from the region after using a Bayesian approach to produce many possible chronologies for each site. Principal component analysis then identified chronologically-robust, multi-site oxygen isotope signals, including negative values during the Younger Dryas, but no significant deviations from the early Holocene mean of the regional records. However, differences among sites indicate significant trends that likely relate to interacting changes in the regional gradients of seasonal temperatures and precipitation as well as moisture sources, moisture pathways, and aridity that were controlled by large-scale climatic controls such as insolation, the progressive decline of the Laurentide Ice Sheet, and changes in oceanic circulation. Centennial shifts punctuate these trends at ca. 9.3 and 8.2 cal ka BP, and reveal that the local character of these short-lived features requires a detailed understanding of lake hydrology and regional isotopic gradients to yield reliable information for regional climate reconstructions.

Late Tertiary to late Quaternary record in the Mackenzie Mountains, Northwest Territories, Canada: stratigraphy, paleosols, paleomagnetism, and chlorine - 36

1996 ◽  
Vol 33 (6) ◽  
pp. 875-895 ◽  
Author(s):  
A. Duk-Rodkin ◽  
R. W. Barendregt ◽  
C. Tarnocai ◽  
F. M. Phillips
Keyword(s):  
Late Quaternary ◽  
Ice Sheet ◽  
Climatic Conditions ◽  
Unconsolidated Sediments ◽  
Laurentide Ice Sheet ◽  
Stratigraphic Sequence ◽  
Late Tertiary ◽  
Mackenzie Mountains ◽  
Late Wisconsinan ◽  
Stratigraphic Succession

A stratigraphic sequence of unconsolidated sediments ranging in age from Late Pliocene to Late Pleistocene is recorded in the Canyon Ranges of the Mackenzie Mountains. Three of the sections (Katherine Creek, Little Bear River, and Inlin Brook) expose bedrock and Tertiary gravel overlain by colluvium and a multiple till sequence of montane origin, separated by paleosols and capped by a till of Laurentide origin. The sections are correlated on the basis of lithology, paleosol development, paleomagnetism, and chlorine dating of surface boulder erratics. A formal stratigraphic nomenclature is proposed for the deposits of this region. The sequence of glacial tills separated by paleosols reflects a long record of glacial–interglacial cycles. Soil properties from the oldest paleosol to modern soil show a general decrease in the degree of soil development, suggesting a progressive deterioration of interglacial climatic conditions. A normal–reverse–normal sequence of remanent magnetization was determined within the stratigraphic succession and assigned to the Gauss–Matuyama–Brunhes chrons, respectively. A Gauss age was assigned to the basal colluvium, an early Matuyama age (including Olduvai) to the first two tills, and a Brunhes age to the last three tills. Laurentide deposits are of Late Wisconsinan age and are restricted to the uppermost part of the stratigraphic succession. Chlorine dates for surface boulders place the all-time limit of the Laurentide Ice Sheet at about 30 ka. The Late Wisconsinan Laurentide Ice Sheet was the only continental ice to reach the Mackenzie and Richardson mountains of the northern Cordillera.

scholarly journals Evolution of the large-scale atmospheric circulation in response to changing ice sheets over the last glacial cycle

2014 ◽  
Vol 10 (4) ◽  
pp. 1453-1471 ◽  
Author(s):  
M. Löfverström ◽  
R. Caballero ◽  
J. Nilsson ◽  
J. Kleman
Keyword(s):  
Atmospheric Circulation ◽  
Large Scale ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Glacial Cycle ◽  
Mean Flow ◽  
Geological Evidence ◽  
Last Glacial ◽  
The Last Glacial

Abstract. We present modelling results of the atmospheric circulation at the cold periods of marine isotope stage 5b (MIS 5b), MIS 4 and the Last Glacial Maximum (LGM), as well as the interglacial. The palaeosimulations are forced by ice-sheet reconstructions consistent with geological evidence and by appropriate insolation and greenhouse gas concentrations. The results suggest that the large-scale atmospheric winter circulation remained largely similar to the interglacial for a significant part of the glacial cycle. The proposed explanation is that the ice sheets were located in areas where their interaction with the mean flow is limited. However, the LGM Laurentide Ice Sheet induces a much larger planetary wave that leads to a zonalisation of the Atlantic jet. In summer, the ice-sheet topography dynamically induces warm temperatures in Alaska and central Asia that inhibits the expansion of the ice sheets into these regions. The warm temperatures may also serve as an explanation for westward propagation of the Eurasian Ice Sheet from MIS 4 to the LGM.

Neotectonics and large-scale geomorphology of Canada

1993 ◽  
Vol 17 (2) ◽  
pp. 248-264 ◽  
Author(s):  
John Adams ◽  
John J. Clague
Keyword(s):  
Large Scale ◽  
Late Quaternary ◽  
Strike Slip ◽  
Laurentide Ice Sheet ◽  
Continental Margins ◽  
Plate Boundaries ◽  
The West ◽  
Late Mesozoic ◽  
Tectonic Events ◽  
Mountain Systems

Canada includes active convergent and strike-slip plate boundaries, several major mountain systems, two passive continental margins, and a stable craton. Neotectonic activity, as indicated by earthquake occurrence, is highest along the west coast and lowest in the interior of the country. Correlations between tectonics and physiography are strongest in the west. Here, the landscape bears a strong imprint of convergent and strike-slip plate regimes. Late Mesozoic and early Cenozoic tectonic events established the setting in which the present physiography of western Canada developed, but the landscape acquired its present form much more recently, in Pliocene and Quaternary time. In contrast, the neotectonic imprint in eastern and northern Canada is enigmatic, and although major concentrations of earthquakes in many areas are associated with reactivated, early Phanerozoic structures, there has been only limited late Quaternary faulting. The vast Canadian craton, despite its very low seismicity, is deforming isostatically at a moderate rate due to melting of the Laurentide Ice Sheet thousands of years ago.

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