| Title | Reconstruction of isostatically adjusted paleo-strandlines along the southern margin of the Laurentide Ice Sheet in the Great Lakes, Lake Agassiz and Champlain Sea basins |
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| Author | Lewis, C F M ;
Breckenridge, A J; Teller, J T |
| Source | Canadian Journal of Earth Sciences 2021 p. 1-21, https://doi.org/10.1139/cjes-2021-0005  Open Access |
| Image |  |
| Year | 2021 |
| Alt Series | Natural Resources Canada, Contribution Series 20200760 |
| Publisher | Canadian Science Publishing |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf; html |
| Province | Ontario; Manitoba; Quebec |
| Area | Great Lakes; Lake Agassiz; Champlain Sea; Lake Iroquois; Lake Whittlesey; Lake Warren; Lake Algonquin; Lake Duluth; Great Lake Nipissing; Canada |
| Lat/Long WENS | -106.0000 -71.5000 55.0000 41.0000 |
| Subjects | Science and Technology; Quebec-Labrador ice dome,; Laurentide Ice Sheet; Keewatin ice dome |
| Illustrations | location maps; cross-plots; diagrams; tables |
| Program | Climate Change Geoscience |
| Released | 2021 10 29 |
| Abstract | Strandlines document the former presence of lakes and a sea in east-central North America along the southern margin of the retreating Laurentide Ice Sheet (LIS). The strandlines of these formerly level
water bodies are uplifted to the north and provide evidence of glacial isostatic adjustment (GIA) of the Earth's crust to the former ice load. We compile published ages and measurements of the present elevation and location of shore features in the
strandlines of eight major paleo-water bodies from the St. Lawrence Valley to the northern Great Plains in digital format as an aid for the numerical modelling of GIA. Data for eastern water bodies were extracted and digitized from publications
during the past 120 years. Digital position coordinates were scaled from published maps of survey sites or were determined using Google Earth Pro software. Published data for paleo-lakes Duluth and Agassiz were mainly obtained from field measurements
and digital elevation models. Two-sigma or 95% probability values are provided for the strandline ages and for isobase (contour) positions representing the deformed water surfaces. Peak strandline gradients reported here were largest at about ca. 13
000 years ago. Lower strandline gradients for older shores may reveal areas closer to the peripheral bulge and areas of thinner ice (lighter crustal loads). Concave upward strandline profiles characterize most paleo-basins, whereas a linear uplift
profile characterizes the Champlain Sea strandline. Directions of strandline maximum uplift within the former water body basins point toward the thickest part of the LIS near the Quebec-Labrador ice dome. |
| Summary | (Plain Language Summary, not published)
Abandoned beaches document the former presence of lakes and a sea in east-central North America along the retreating southern margin of the Laurentide
Ice Sheet (LIS) of the last ice age after about 20,000 years ago. The shorelines of these formerly level water bodies are uplifted to the north and provide evidence of glacial isostatic adjustment (GIA) of the earth's crust to the former ice load,
that is, crustal depression and recovery. We compiled published ages and measurements of the present elevation and location of these shore features of 8 major paleo-waterbodies from the St. Lawrence Valley to the northern Great Plains as an aid for
the numerical modelling of GIA. Linear uplift characterized shoreline tilt in the eastern sector of the study region, namely that of the Champlain Sea and easternmost Lake Iroquois, whereas areas to the west are characterized by concave upward
uplift. The difference in form of uplift is poorly understood. Directions of maximum uplift within the former waterbody basins focussed mainly on the area of the thickest part of the LIS in its Quebec-Labrador ice dome adjacent to southeastern Hudson
Bay and on its radiating ice divides. |
| GEOSCAN ID | 328141 |
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