Optically stimulated luminescence ages from the Lake Agassiz basin in Manitoba

2018 ◽  
Vol 89 (2) ◽  
pp. 478-493 ◽  
Author(s):  
James T. Teller ◽  
Roderick A. McGinn ◽  
Haresh M. Rajapara ◽  
Anil D. Shukla ◽  
Ashok K. Singhvi
Keyword(s):  
Ice Sheet ◽  
Early History ◽  
Optically Stimulated Luminescence ◽  
Water Phase ◽  
Laurentide Ice Sheet ◽  
Fluvial Sediments ◽  
Lake Agassiz ◽  
The North ◽  
Insight Into

AbstractGeomorphic analysis and optically stimulated luminescence (OSL) ages from undated Lake Agassiz beaches and adjacent fluvial sediments on Riding Mountain in Manitoba provide insight into their early history. New OSL ages of 14.5±2.4 and 13.4±0.7 ka on the oldest (Herman to Norcross) beaches of Lake Agassiz near the Canada-U.S. border indicate that the Laurentide Ice Sheet (LIS) retreated from that part of the Agassiz basin by ~14.5 ka. To the north along Riding Mountain, the Herman strandlines are absent, and OSL ages on the oldest beach there average 12.9 ka, which links it to the younger Norcross-Tintah strandlines. In adjacent Riding Mountain, OSL ages and geomorphological relationships of a large abandoned glacial spillway >200 m above the oldest beaches of Lake Agassiz indicate that this channel predates retreat of the LIS and formation of beaches in this part of the Agassiz basin, with ice remaining in this area until after 14.5 ka. OSL ages on the Gimli beach 170 km to the east are >3000 yr older than conventional assignments, suggesting that it formed during the Moorhead low-water phase 12.8–10.6 ka. Luminescence ages support the conclusion that the Campbell beach formed ~10.9 ka near the end of the Moorhead low-water phase.

Importance of the Rossendale Site in Establishing a Deglacial Chronology Along the Southwestern Margin of the Laurentide Ice Sheet

1989 ◽  
Vol 32 (1) ◽  
pp. 12-23 ◽  
Author(s):  
James T. Teller
Keyword(s):  
Organic Matter ◽  
North America ◽  
Radiocarbon Dating ◽  
Ice Sheet ◽  
Water Phase ◽  
Laurentide Ice Sheet ◽  
Lake Agassiz ◽  
Southwestern Margin

AbstractThe timing of deglaciation in the Lake Agassiz basin is critical in establishing the routing of meltwater and precipitation runoff from a 2,000,000-km2 region of central North America and in evaluating the influence this water had on rivers and oceans into which it drained. Dates of 12,400 ± 420 and 12,100 ± 160 yr B.P. for moss at the Rossendale site in Manitoba have long been a key for those advocating an “early” deglacial chronology in this region. However, new dates for wood from this site and paleoecological interpretations of ostracods, molluscs, and the dated moss all support a “young” deglacial scenario. Of particular significance is the fact that the dated moss, Scorpidium scorpioides, is a subaquatic type subject to contamination by old carbon dissolved from bedrock. In fact, most subaquatic moss may be unreliable for radiocarbon dating. For these reasons, the 12,400 and 12,100 yr B.P. dates are rejected. New dates of 9600 ± 70 and 9510 ± 90 yr B.P. for wood from the same organic-rich unit containing the dated moss, ostracods, and molluscs fit well with the “young” deglacial chronology of the southwestern Laurentide ice margin advocated by many. In short, the ice margin appears to have retreated into the southern Lake Agassiz basin after 12,000 yr B.P. and north of the Rossendale site by 11,000 yr B.P. About 10,000 yr B.P., following the Moorhead low-water phase, Lake Agassiz rose to the Campbell level. The dated organic matter at Rossendale was deposited in a lagoon behind the Campbell beach.

scholarly journals Simulating the Early Holocene demise of the Laurentide Ice Sheet with BISICLES (public trunk revision 3298)

2020 ◽  
Vol 13 (9) ◽  
pp. 4555-4577
Author(s):  
Ilkka S. O. Matero ◽  
Lauren J. Gregoire ◽  
Ruza F. Ivanovic
Keyword(s):  
Mass Balance ◽  
General Circulation ◽  
Ice Sheet ◽  
Circulation Model ◽  
Early Holocene ◽  
Laurentide Ice Sheet ◽  
Hudson Bay ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
The North

Abstract. Simulating the demise of the Laurentide Ice Sheet covering Hudson Bay in the Early Holocene (10–7 ka) is important for understanding the role of accelerated changes in ice sheet topography and melt in the 8.2 ka event, a century long cooling of the Northern Hemisphere by several degrees. Freshwater released from the ice sheet through a surface mass balance instability (known as the saddle collapse) has been suggested as a major forcing for the 8.2 ka event, but the temporal evolution of this pulse has not been constrained. Dynamical ice loss and marine interactions could have significantly accelerated the ice sheet demise, but simulating such processes requires computationally expensive models that are difficult to configure and are often impractical for simulating past ice sheets. Here, we developed an ice sheet model setup for studying the Laurentide Ice Sheet's Hudson Bay saddle collapse and the associated meltwater pulse in unprecedented detail using the BISICLES ice sheet model, an efficient marine ice sheet model of the latest generation which is capable of refinement to kilometre-scale resolutions and higher-order ice flow physics. The setup draws on previous efforts to model the deglaciation of the North American Ice Sheet for initialising the ice sheet temperature, recent ice sheet reconstructions for developing the topography of the region and ice sheet, and output from a general circulation model for a representation of the climatic forcing. The modelled deglaciation is in agreement with the reconstructed extent of the ice sheet, and the associated meltwater pulse has realistic timing. Furthermore, the peak magnitude of the modelled meltwater equivalent (0.07–0.13 Sv) is compatible with geological estimates of freshwater discharge through the Hudson Strait. The results demonstrate that while improved representations of the glacial dynamics and marine interactions are key for correctly simulating the pattern of Early Holocene ice sheet retreat, surface mass balance introduces by far the most uncertainty. The new model configuration presented here provides future opportunities to quantify the range of plausible amplitudes and durations of a Hudson Bay ice saddle collapse meltwater pulse and its role in forcing the 8.2 ka event.

scholarly journals The implications of the Pineo Ridge readvance in Maine

2011 ◽  
Vol 31 (3-4) ◽  
pp. 203-206 ◽  
Author(s):  
Harold W. Borns ◽  
Terence J. Hughes
Keyword(s):  
Sea Level ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Bay Of Fundy ◽  
Great Lakes Region ◽  
Ice Streams ◽  
Ice Caps ◽  
Major Consequence ◽  
Ice Cap ◽  
The North

Much of the Laurentide ice sheet in Maine, Atlantic Provinces, and southern Quebec was a "marine ice sheet," that is it was grounded below the prevailing sea level. When proper conditions prevailed, calving bays progressed into the ice sheet along ice streams partitioning it, leaving those portions grounded above sea level as residual ice caps. At least by 12,800 yrs. BP a calving bay had progressed up the St. Lawrence Lowland at least to Ottawa while a similar, but less extensive calving bay developed in Central Maine at approximately the same time. Concurrently, ice draining north into the St. Lawrence and south into the Central Maine calving bays rapidly lowered the surface of the intervening ice sheet until it eventually divided over the NE-SW trending Boundary and Longfellow Mountains and probably over other highland areas as well. A major consequence of these nearly simultaneous processes was the separation of an initial large ice cap over part of Maine, New Brunswick, and Québec which was bounded on the west by the calving bay in Central Maine, to the north by the calving bay in the St. Lawrence Lowland, to the south by the Bay of Fundy, and to the east by the Gulf of St. Lawrence. In coastal Maine, east of the calving bay, the margin of the ice cap receded above the marine limit at least 40 km and subsequently read-vanced terminating at Pineo Ridge moraine approximately 12,700 yrs. BP. These events are the stratigraphie and chronologic equivalent of the Cary-Pt. Huron recession/Pt. Huron readvance of the Great Lakes region.

scholarly journals The Glacial Geomorphology of the North-West sector of the Laurentide Ice Sheet

2011 ◽  
Vol 7 (1) ◽  
pp. 409-428 ◽  
Author(s):  
Victoria H. Brown ◽  
Chris R. Stokes ◽  
Colm O'Cofaigh
Keyword(s):  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Glacial Geomorphology ◽  
North West ◽  
The North

scholarly journals Laurentide Ice-Flow Patterns: A Historical Review, and Implications of the Dispersal of Belcher Islands Erratics

2007 ◽  
Vol 44 (2) ◽  
pp. 113-136 ◽  
Author(s):  
Victor K. Prest
Keyword(s):  
Ice Sheet ◽  
Historical Review ◽  
Flow Patterns ◽  
The Arctic ◽  
Laurentide Ice Sheet ◽  
Complex Nature ◽  
Hudson Bay ◽  
Ice Flow ◽  
Flow Models ◽  
The North

ABSTRACTThis paper deals with the evolution of ideas concerning the configuration of flow patterns of the great inland ice sheets east of the Cordillera. The interpretations of overall extent of Laurentide ice have changed little in a century (except in the Arctic) but the manner of growth, centres of outflow, and ice-flow patterns, remain somewhat controversial. Present geological data however, clearly favour the notion of multiple centres of ice flow. The first map of the extent of the North American ice cover was published in 1881. A multi-domed concept of the ice sheet was illustrated in an 1894 sketch-map of radial flow from dispersal areas east and west of Hudson Bay. The first large format glacial map of North America was published in 1913. The binary concept of the ice sheet was in vogue until 1943 when a single centre in Hudson Bay was proposed, based on the westward growth of ice from Labrador/Québec. This Hudson dome concept persisted but was not illustrated until 1977. By this time it was evident from dispersal studies that the single dome concept was not viable. Dispersal studies clearly indicate long-continued westward ice flow from Québec into and across southern Hudson Bay, as well as eastward flow from Keewatin into the northern part of the bay. Computer-type modelling of the Laurentide ice sheet(s) further indicates their complex nature. The distribution of two indicator erratics from the Proterozoicage Belcher Island Fold Belt Group help constrain ice flow models. These erratics have been dispersed widely to the west, southwest and south by the Labrador Sector of more than one Laurentide ice sheet. They are abundant across the Paleozoic terrain of the Hudson-James Bay lowland, but decrease in abundance across the adjoining Archean upland. Similar erratics are common in northern Manitoba in the zone of confluence between Labrador and Keewatin Sector ice. Scattered occurences across the Prairies occur within the realm of south-flowing Keewatin ice. As these erratics are not known, and presumably not present, in Keewatin, they indicate redirection and deposition by Keewatin ice following one or more older advances of Labrador ice. The distribution of indicator erratics thus test our concepts of ice sheet growth.

A post-Lake Minong transgressive event on the north shore of Lake Superior, Ontario: possible evidence of Lake Agassiz inflow

1994 ◽  
Vol 31 (11) ◽  
pp. 1638-1641 ◽  
Author(s):  
Brian A. M. Phillips ◽  
Philip W. Fralick
Keyword(s):  
Water Level ◽  
Lake Superior ◽  
Lower Portion ◽  
Fluvial Sediments ◽  
Lake Agassiz ◽  
North Shore ◽  
The North ◽  
Level Oscillation ◽  
Water Level Oscillation ◽  
Lake Minong

Modification of an ice-contact delta built on the margin of Lake Minong (9500 BP) is ascribed to a transgressive event. Reworking of fluvial sediments by wave action and the infilling of the lower end of a distributary valley demonstrate a post-Minong transgression and reoccupation of the lower portion of the delta. Estimated to be in the order of 18 m, this water-level oscillation may represent evidence of one of several catastrophic discharges of Lake Agassiz into the Superior basin, proposed to have occurred between 9.5 and 8.0 ka BP.

Oceanic Evidence for the Mechanism of Rapid Northern Hemisphere Glaciation

1980 ◽  
Vol 13 (1) ◽  
pp. 33-64 ◽  
Author(s):  
W. F. Ruddiman ◽  
A. McIntyre ◽  
V. Niebler-Hunt ◽  
J. T. Durazzi
Keyword(s):  
Northern Hemisphere ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Local Source ◽  
The North ◽  
Land Mass ◽  
Oxygen Isotopic ◽  
The North Atlantic

AbstractThe oxygen isotopic stage 5/4 boundary in deep-sea sediments marks a prominent interval of northern hemisphere ice-sheet growth that lasted about 10,000 yr. During much of this rapid ice growth, the North Atlantic Ocean from at least 40°N to 60°N maintained warm sea-surface temperatures, within 1° to 2°C of today's subpolar ocean. This oceanic warmth provided a local source of moisture for ice-sheet accretion on the adjacent continents. The unusually strong thermal gradient off the east coast of North America (an “interglacial” ocean alongside a “glacial” land mass) also should have directed low-pressure storms from warm southern latitudes north-ward toward the Laurentide Ice Sheet. In addition, minimal calving of ice into the North Atlantic occurred during most of the stage 5/4 transition, indicative of ice retention within the continents. Diminished summer and autumn insolation, a warm subpolar ocean, and minimal calving of ice are conducive to rapid and extensive episodes of northern hemisphere ice-sheet growth.

scholarly journals The Atmosphere’s Response to the Ice Sheets of the Last Glacial Maximum

1990 ◽  
Vol 14 ◽  
pp. 32-38 ◽  
Author(s):  
Kerry H. Cook
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Ice Age ◽  
Laurentide Ice Sheet ◽  
Stationary Waves ◽  
The North ◽  
The Last Glacial

This paper discusses some modeling results that indicate how the atmospheric response to the topography of the continental ice of the Last Glacial Maximum (LGM) may be related to the cold North Atlantic Ocean of that time. Broccoli and Manabe (1987) used a three-dimensional general circulation model (GCM) of the atmosphere coupled with a fixed-depth, static ocean mixed-layer model with ice-age boundary conditions to investigate the individual influences of the CLIMAP ice sheets, snow-free land albedos, and reduced atmospheric CO2 concentrations. They found that the ice sheets are the most influential of the ice-age boundary conditions in modifying the northern hemisphere climate, and that the presence of continental ice sheets alone leads to cooling over the North Atlantic Ocean. One approach for extending these GCM results is to consider the stationary waves generated by the ice sheets. Cook and Held (1988) showed that a linearized, steady-state, primitive equation model can give a reasonable simulation of the GCM’s stationary waves forced by the Laurentide ice sheet. The linear model analysis suggests that the mechanical effect of the changed slope of the surface, and not changes in the diabatic heating (e.g. the high surface albedos) or time-dependent transports that necessarily accompany the ice sheet in the GCM, is largely responsible for the ice sheet’s influence. To obtain the ice-age stationary-wave simulation, the linear model must be linearized about the zonal mean fields from the GCM’s ice-age climate. This is the case because the proximity of the cold polar air to the region of adiabatic heating on the downslope of the Laurentide ice sheet is an important factor in determining the stationary waves. During the ice age, cold air can be transported southward to balance this downslope heating by small perturbations in the meridional wind, consistent with linear theory. Since the meridional temperature gradient is more closely related to the surface albedo (ice extent) than to the ice volume, this suggests a mechanism by which changes in the stationary waves and, therefore, their cooling influence at low levels over the North Atlantic Ocean, can occur on time scales faster than those associated with large changes in continental ice volume.

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