Measurement, Correlation, and Mapping of Glacial Lake Algonquin Shorelines in Northern Michigan

Abstract

Glacial Lake Algonquin, the most widespread proglacial lake in the Great Lakes basin, attained a high (Main) stage at about 11,000 b.p. , at which time it developed a conspicuous shoreline. Several lower, less obvious Algonquin shorelines also exist. Previous research on this lake has involved three drawbacks: (1) imprecise methods of establishing the location and elevation of shoreline features, (2) misidentification of some offshore coastal landforms as beach ridges, and (3) tenuous and difficult correlation of named shorelines across wide distances. We believe that more than one name is used for some lake phases, making correlation difficult. Our study focused on these problems by surveying and mapping 160 Algonquin wave-cut bluffs throughout northern Michigan. We utilized global positioning system (GPS) technology to precisely record the three-dimensional positions of the bases of these bluffs and statistically fit trend surfaces to these positions. Classification of bluff data indicates that four strong Algonquin shorelines exist in the region, for which we recommend these names: Main, Ardtrea, Wyebridge, and Payette. Weak evidence for a possible fifth, lower shoreline was observed at five locations. Maps of the landscape during each lake phase were created, revealing islands not previously recognized. Rebound curves and maps of the lake during each phase, using the positional data set, indicate that isostatic rebound in the study area appears to be greatest in the northeast sector.

The influence of contemporary and historic landscape features on the genetic structure of the sand dune endemic, Cirsium pitcheri (Asteraceae)

“…(Schaetzl et al, 2002) and the second was a rapid decline 7000 yBP associated with a period of warmer and drier climate (Colman et al, 1994a, b). The second decline was the lowest level the lake reached, estimated to be a drop of 100 m below current levels (Colman et al, 1994b).…”

Paleotopographic reconstructions of the eastern outlets of glacial Lake Agassiz

“…Isobases (contours of equal isostatic rebound) can be drawn from the elevations of raised beaches and can be used to define the regional rebound (or rebound surface) since the beaches formed. Databases of paleotopography generated by subtracting rebound data from modern elevations can be used for the quantitative characterization of past terrain morphology and surface processes (Lambeck 1996;Mann et al 1999;Leverington et al 2000Leverington et al , 2002aTeller et al 2002;Schaetzl et al 2002).…”

Glacial Isostatic Adjustment of the Laurentian Great Lakes Basin: Using the Empirical Record of Strandline Deformation for Reconstruction of Early Holocene Paleo-Lakes and Discovery of a Hydrologically Closed Phase*

“…In the continental interior, isobases of glacio-isostatic rebound are usually defined by the elevations of a differentially uplifted shoreline of a former lake (Goldthwait, 1907(Goldthwait, , 1910Leverett and Taylor, 1915;Hough, 1958;Walcott, 1972;Lewis and Anderson, 1989;Schaetzl et al, 2002). Sets of isobases selected for this study for basins within the Great Lakes watershed are illustrated in Figure 2A and 2B in which the lowest and highest elevations, trends of isobases, the name and uncalibrated radiocarbon age are shown for each lake.…”

“…The accuracy for estimating lake levels from empirical indicators is generally considered here to be at best about ±1 m based on survey error and variations in elevations of strandline bluffs, beaches, bars and spits (Schaetzl et al, 2002). The computed initial elevations for lake-level indicators are considered accurate within about 2 m in areas of good isobase control, and somewhat >2 m in areas where constraining isobases have been extrapolated.…”