scholarly journals Chronology of advance and recession dynamics of the southern Green Bay Lobe of the Laurentide Ice Sheet, south-central Wisconsin, USA

2020 ◽  
Vol 95 ◽  
pp. 142-153
Author(s):  
Eric C. Carson ◽  
John W. Attig ◽  
J. Elmo Rawling ◽  
Paul R. Hanson ◽  
Stefanie E. Dodge
Keyword(s):  
Ice Sheet ◽  
Marine Isotope Stage ◽  
Laurentide Ice Sheet ◽  
Time Interval ◽  
Green Bay ◽  
Ams Radiocarbon Dating ◽  
South Central ◽  
Southern Margin ◽  
Osl Age ◽  
Age Estimates

AbstractWe used a combination of accelerator mass spectrometry (AMS) radiocarbon dating, optically stimulated luminescence (OSL) age estimates, and stratigraphic data from cores collected along the southern margin of the Green Bay Lobe (GBL) of the Laurentide Ice Sheet to provide new information on the timing and dynamics of the end of advance of the GBL and the dynamics of the ice sheet while very near its maximum position. Coring at multiple sites along the margin of the GBL indicate that ice had reached a stable position near its maximum extent by 24.7 ka; that ice advanced several kilometers to the Marine Isotope Stage 2 maximum position sometime shortly after 21.2 ka; and that ice remained at or beyond that position through the time interval represented by an OSL age estimate of 19.2 ± 3.2 ka. The timeline developed from these chronological data is internally consistent with, and further refines, AMS radiocarbon ages and OSL age estimates previously published for the southern margin of the GBL. It also provides new chronological control on the expansion of the GBL from its late Marine Isotope Stage (MIS) 3 extent to its MIS 2 maximum.

Numeric control on the late-glacial chronology of the southern Laurentide Ice Sheet derived from ice-proximal lacustrine deposits

2012 ◽  
Vol 78 (3) ◽  
pp. 583-589 ◽  
Author(s):  
Eric C. Carson ◽  
Paul R. Hanson ◽  
John W. Attig ◽  
Aaron R. Young
Keyword(s):  
Ice Sheet ◽  
Late Glacial ◽  
Osl Dating ◽  
Marine Isotope Stage ◽  
Laurentide Ice Sheet ◽  
Upper Midwest ◽  
Green Bay ◽  
Lacustrine Deposits ◽  
South Central ◽  
Glacial Chronology

AbstractWe used a combination of radiocarbon and OSL dating in ice-proximal lacustrine silt and clay and outwash sand to estimate when ice of the Green Bay Lobe of the Laurentide Ice Sheet began retreating from its maximum position in south-central Wisconsin. The radiocarbon ages indicate that lakes had formed in the two tributary valleys by ~ 17.2 and 20.1 ka, respectively. The OSL ages indicate that the Green Bay Lobe was at its maximum position from about 26.4 ± 5.1 ka to 21.4 ± 3.3 ka. These data provide entirely new chronologic control on late Wisconsin (Marine Isotope Stage 2) glacial event in the upper Midwest, as well as the opportunity to directly compare radiocarbon and OSL ages in this setting.

scholarly journals Late Wisconsin Advance and Retreat Pattern in the Miami Sublobe, Laurentide Ice Sheet

1990 ◽  
Vol 14 ◽  
pp. 172-175 ◽  
Author(s):  
Thomas V. Lowell ◽  
Robert Stuckenrath
Keyword(s):  
Climatic Change ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Maximum Extent ◽  
Southern Margin ◽  
Radiometric Ages ◽  
A Site ◽  
Age Estimates

Ice-sheet advance and retreat chronologies reflect climatic change in a manner that is difficult to decipher. Especially difficult is the placement of records into a chronologic sequence. Multiple age estimates obtained from three stratigraphic positions at a site in Ohio show that organics within deposits of the Miami sublobe, along the southern margin of the Laurentide ice sheet, may be up to 3000 years older than the age of the maximum Late Wisconsin extension of that sublobe. In addition, recent studies on organic accumulations above glacial drift provide bracketing ages for ice recession. When the existing radiometric ages for the Miami sublobe are interpreted with these new radiometric constraints, several fluctuations suggested by prior workers are unsupported. A simpler chronology for the Miami sublobe suggests that in late Wisconsin time the southern margin of the Laurentide ice sheet advanced through Ohio about 22 ka to its maximum extent at 19.7 and remained near there until 15 ka. This is in agreement with newly-refined stratigraphic histories of other Laurentide lobes.

scholarly journals Late Wisconsin Advance and Retreat Pattern in the Miami Sublobe, Laurentide Ice Sheet

1990 ◽  
Vol 14 ◽  
pp. 172-175 ◽  
Author(s):  
Thomas V. Lowell ◽  
Robert Stuckenrath
Keyword(s):  
Climatic Change ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Maximum Extent ◽  
Southern Margin ◽  
Radiometric Ages ◽  
A Site ◽  
Age Estimates

Ice-sheet advance and retreat chronologies reflect climatic change in a manner that is difficult to decipher. Especially difficult is the placement of records into a chronologic sequence. Multiple age estimates obtained from three stratigraphic positions at a site in Ohio show that organics within deposits of the Miami sublobe, along the southern margin of the Laurentide ice sheet, may be up to 3000 years older than the age of the maximum Late Wisconsin extension of that sublobe. In addition, recent studies on organic accumulations above glacial drift provide bracketing ages for ice recession. When the existing radiometric ages for the Miami sublobe are interpreted with these new radiometric constraints, several fluctuations suggested by prior workers are unsupported. A simpler chronology for the Miami sublobe suggests that in late Wisconsin time the southern margin of the Laurentide ice sheet advanced through Ohio about 22 ka to its maximum extent at 19.7 and remained near there until 15 ka. This is in agreement with newly-refined stratigraphic histories of other Laurentide lobes.

scholarly journals LGM Summer Climate on the Southern Margin of the Laurentide Ice Sheet: Wet or Dry?*

2005 ◽  
Vol 18 (16) ◽  
pp. 3317-3338 ◽  
Author(s):  
David H. Bromwich ◽  
E. Richard Toracinta ◽  
Robert J. Oglesby ◽  
James L. Fastook ◽  
Terence J. Hughes
Keyword(s):  
Boundary Conditions ◽  
Great Plains ◽  
Land Surface ◽  
Thermal Gradient ◽  
Mesoscale Model ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Low Level ◽  
Summer Climate ◽  
Southern Margin

Abstract Regional climate simulations are conducted using the Polar fifth-generation Pennsylvania State University (PSU)–NCAR Mesoscale Model (MM5) with a 60-km horizontal resolution domain over North America to explore the summer climate of the Last Glacial Maximum (LGM: 21 000 calendar years ago), when much of the continent was covered by the Laurentide Ice Sheet (LIS). Output from a tailored NCAR Community Climate Model version 3 (CCM3) simulation of the LGM climate is used to provide the initial and lateral boundary conditions for Polar MM5. LGM boundary conditions include continental ice sheets, appropriate orbital forcing, reduced CO2 concentration, paleovegetation, modified sea surface temperatures, and lowered sea level. The simulated LGM summer climate is characterized by a pronounced low-level thermal gradient along the southern margin of the LIS resulting from the juxtaposition of the cold ice sheet and adjacent warm ice-free land surface. This sharp thermal gradient anchors the midtropospheric jet stream and facilitates the development of synoptic cyclones that track over the ice sheet, some of which produce copious liquid precipitation along and south of the LIS terminus. Precipitation on the southern margin is orographically enhanced as moist southerly low-level flow (resembling a contemporary Great Plains low-level jet configuration) in advance of the cyclone is drawn up the ice sheet slope. Composites of wet and dry periods on the LIS southern margin illustrate two distinctly different atmospheric flow regimes. Given the episodic nature of the summer rain events, it may be possible to reconcile the model depiction of wet conditions on the LIS southern margin during the LGM summer with the widely accepted interpretation of aridity across the Great Plains based on geological proxy evidence.

scholarly journals Was the Laurentide Ice Sheet significantly reduced during Marine Isotope Stage 3?

Geology ◽  
2019 ◽  
Vol 47 (2) ◽  
pp. 111-114 ◽  
Author(s):  
April S. Dalton ◽  
Sarah A. Finkelstein ◽  
Steven L. Forman ◽  
Peter J. Barnett ◽  
Tamara Pico ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Marine Isotope Stage ◽  
Laurentide Ice Sheet ◽  
Marine Isotope Stage 3

Late Wisconsin periglacial environments of the southern margin of the Laurentide Ice Sheet reconstructed from pollen analyses

2002 ◽  
Vol 17 (8) ◽  
pp. 773-780 ◽  
Author(s):  
Linda Heusser ◽  
Terryanne Maenza-Gmelch ◽  
Thomas Lowell ◽  
Rebecca Hinnefeld
Keyword(s):  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Southern Margin ◽  
Pollen Analyses

SEDIMENT TRANSPORT CYCLES OF THE LAURENTIDE ICE SHEET I: SOFT TO HARD BED TRANSITION DURING WISCONSIN MARINE ISOTOPE STAGE 5D-2

2020 ◽  
Author(s):  
Phillip Larson ◽  
◽  
Howard D. Mooers ◽  
Angela J. Berthold ◽  
Kristi M. Kotrapu
Keyword(s):  
Sediment Transport ◽  
Ice Sheet ◽  
Marine Isotope Stage ◽  
Laurentide Ice Sheet
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