-uvrt-n.- . - “pen" unnuu‘ s or o r . ‘ . ‘ .... ‘ . ‘. , V l . . ._ ., 11‘63 0?) 93“ ”HMHHPHWPMWWWMPVWIW 31293 00577 6608 F LIBRARY Michigan State University This is to certify that the thesis entitled The Glacio—Isostasy of the Southern Lake Michigan Basin presented by Thomas John Timmermans has been accepted towards fulfillment of the requirements for Masters Geology degree in I)ate 5;74/;5/g>59 / / 0—7639 MSU is an Affirmative Action/Equal Opportunity Institution MSU LIBRARIES .2— RETURNING MATERIALS: Place in book drop to remove this checkout from your record. FINES will be charged if book is returned after the date stamped below. ‘wgfihiflw '43 1w 1'} Hi}? [i pp infliifi’ ’)_ '~ ._. “ ‘ "ii-“13.1,. . 7*)“ C) n 10 AUG 2 ’7 "201. THE GLACIO-ISOSTASY OF THE SOUTHERN LAKEIMICHIGAN BASIN BY Thomas John Timmermans A THESIS Submitted to Michigan State University in partial fulfillment of the requirements . for the degree of MASTER OF SCIENCE Department of Geological Scienoes 1989 \qw <3 OI'\ \3 ABSTRACT THE GLACIO-ISOSTASY OF THE SOUTHERN LAKE MICHIGAN BASIN BY Thomas John Timmermans Glacial geologists have deduced from field data of relict shorelines that the Southern Lake Michigan basin has remained stable for the last 12,000 years even though it was, according to glaciologists, under a substantial thickness of ice during the late Wisconsin ice age. This is not consistant with normal isostatic processes as described by geophysicists. This study uses a numerical model of a spherical, visco-elastic, self-gravitating earth to model isostastic processes and produces new field data to analyze the disagreement between the empirical and the theoretical interpretations. This study also reevaluates the existing empirical data for internal consistency and compares them with the numerical calculations. The results of this study indicate the traditional interpretations of isostatic stability are inconsistent with both the theoretical calculations and the empirical data. The new empirical data indicates as much as 0.15 meters per kilometer of differential rebound in the southern Lake Michigan basin since the formation of the Calumet Shoreline approximately 11,500 years ago. dedicated to Jesus 611. I31) who £101an 731 ndma Col. 1:16a and Diane an unlimited source of encouragement iii ACKNOWLEDGEMENTS Without inspiration and discipline from my major professors, Dr. Jim Clark and Dr. Grahame Larson, this project could not have been completed. I thank these instructors, and Dr. Mike Velbel, for helping me with this project and many things beyond. I also express sincere appreciation to the many students at Michigan State University and Calvin College who helped with this project: Bill Monaghan, Mark Hendriks, Tom Hooyer, J.J. Groen, Calvin Struck, Ken Guetter, Jonathan Icenhower, Harold Prager, John Primus, and Jeff Walsh. I also acknowledge the National Science Foundation (EAR 840 7660, EAR 860 7330, EAR 880 4201), EDI Engineering & Science, and Chevron Oil for financial support throughout this project. My thanks also to my fellow workers at EDI (especially Jim Tolbert) who encouraged me to complete this thesis. iv TABLE OF CONTENTS LIST OF FIGURES viii LIST OF TABLES xvii CHAPTER 1: INTRODUCTION 1 1.1 Definition of the Problem 1.2 Glacial and.Post-Glacia1 History of the Lake Michigan Basin 4 CHAPTER 2: THE EMPIRICAL AND NUMERICAL MODELS 18 2.1 The Traditional Model 18 2.1.1 The Historical Development 18 2.1.2 Traditional Model and Conflicting Empirical Data 24 2.1.2.1 The Response of the Earth to A Surface Load 28 2.1.2.2 Lake Gauge Data 2.1.2.3 Observed Deformation of Water Planes in Southern Michigan 36 2.1.2.4 The Nipissing Shoreline 41 2.2 The Numerical Model 42 2.2.1 The Model's Calculations and Assumptions 45 2.2.2 The Model Input 51 2.3 The Numerica 2.3.1 2.3.2 2.3.3 2.3.4 1 Model Results Modeled Outlet Chronologies Modeled Lake Gauge Deleveling Data Modeled Algonquin Shoreline Data Summary of Modeling CHAPTER 3: EVALUATION OF SHORELINE DATA FROM SOUTHWESTERN MICHIGAN 3.1 Introduction 3.2 The Shoreline Data 3.2.1 3.2.2 3.2.3 3.2.3.1 3.2.3.2 3.2.4 3.2.4.1 3.2.4.2 3.2.4.3 3.2.4.4 3.2.4.5 3.3 Comparison t Methods of Investigation Regional Analysis of the Data Local Embayments Allegan County Embayment Muskegon/Ottawa County Embayment Some Important Field Sites The Hagar Site The Bass Creek Site The Slocum Ridge The Claybanks Section The White River Delta 0 the Models vi 51 51 55 58 60 64 64 68 68 69 77 78 80 84 86 92 93 97 99 102 CHAPTER 4: CONCLUSIONS APPENDICES A. The Ice Sheets Used in the Numerical Calculations ' 1. Thick Ice Sheet (after Denton and Hughes 1981) 2. Thin Ice Sheet (after Boulten et a1. B. The Deformations Associated With Each Numerical Calculations C. The Field Sites BIBLIOGRAPHY vii 1985) 107 111 111 112 130 147 169 199 Figure Figure Figure Figure Figure Figure Figure Figure Figure LIST OF FIGURES The location of the Algonquin "hinge line" and the Late Wisconsinan maximum ice front in the Great Lakes Region. Location of field study area in relationship to the Algonquin Hinge line and maximum ice front. Outlets of importance in the upper Great Lakes area. Chicago, Port Huron, Kirkfield, and North Bay were the fourt major outlets controlling the lake level in the Lake Michigan basin throughout the past 15,000 years. Dispersion of shoreline features to the north. As the basin tilts through time the outlet area is reoccuppied while shoreline features to the north are dispersed. Late Wisconsinan and Holocene lake phases in the Lake Michigan basin from Hansel et al. (1985b). Larsen's interpretation of the Main Algonquin level in the upper Great Lakes from Larsen (1987). Note the low water level in the southern Lake Michigan basin. Chronology of lake levels and glacial events in the Lake Michigan basin from Hansel et al. (1985b). Shaded area indicates times inlets and outlets were used. Chippewa and Stanley low levels in the Lake Michigan and Huron basins from Larsen (1987). Extent of the late Nipissing and Algoma Great Lakes from Larsen (1987). viii 11 14 16 17 17 Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure 2.1 2.4 2.9 2.10 The Algonquin, sub-Algonquin, Nipissing, and Algoma strandlines interpreted by Leverett and Taylor (1915) using data from Goldthwait. Note convergence of these beaches just north of the Port Huron outlet isobase (from Hough 1958). Goldthwait's ice attraction hypthesis. Goldthwait's outlet control hypothesis. Goldthwait's hinge line hypothesis was accepted as the mechanism for causing shorelines to converge. Evenson's isobases of the Glenwood shoreline (after Evenson 1973). Evenson's shoreline profile for the southern Lake Michigan basin. Evenson interprets the Glenwood stage of Lake Chicago as being differentially tilted 6 m (20 ft) and the Calumet stage as being undeformed (after Evenson 1973). Summary of the traditional shoreline model as interpreted by Goldthwait and Evenson. Present rate of vertical movement in the Lake Michigan and Huron basins from lake level gauge data relative to Goderich, Ontario. ‘ Mean summer lake levels at Calumet Harbor minus those at Harbor Beach through time. Mean summer lake levels at Milwaukee Harbor minus those at Sturgeon Bay Canal through time. Mean summer lake levels at Calumet Harbor minus those at Milwaukee Harbor through time. Probale attitude of late-glacial red glaciolacustine clays of the Lake Michigan basin from Larsen (1987). Larsen's interpretation of the late Chippewa water plane at about 8,000 yr B.P. for the Lake Michigan basin (from Larsen 1987). ix 19 21 21 21 25 26 27 3O 32 33 34 37 37 Figure Figure Figure Figure Figure Figure Figure Figure Larsen's interpretation of the Algonquin shoreline data for the Lake Michigan and Huron basins. Note the deformation of the Algonquin shoreline beneath the present level of Lake Michigan south of the Algonquin hinge line (from Larsen 1987). Kaszycki's interpretation of the Algonquib water plane in the Lake Huron basin. Note the deformation of the Algonquin shoreline south of the Algonquin hinge line (from Kaszycki 1985). Larsen's interpretation of the Nipissing and Algoma water planes in the Great Lakes showing continued deformation of these recent shorelines south of the Algonquin hinge line (from Larsen 1985a). Comparison of ice sheets after a) Hughes et al. (1981) and b) Boulten et al. (1985). Thicknesses shown are for the late Wisconsinan glacial maximum (in kilometers). Comparison of ice sheets after a) Hughes et al. (1981) and b) Boulten et al. (1985). Thicknesses shown are in profile along transects shown in Figure 2.15. Grid for ice sheet representation in the numberical model. In the Great Lakes region the normal 5 X 5 degree latitude/longitude grid is reduced to a 2 x 2 degree grid to increase resolution there. Generalized Lake Michigan outlet chronology from empirical data. Note , that the Port Huron and Chicago outlets are stable through time except for erosional incision. Predicted evevation of outlets through time. Note that the Chicago, Port Huron, and North Bay outlets are all near the same elevation at 5,000 yr B.P. in the minimum deformation model (thick lithosphere - thin ice sheet). 39 40 4O 47 48 49 52 54 Figure Figure Figure Figure Figure Figure Figure Figure Figure Comparison of predicted present differential movement using the maximum deformation model (i.e. thin lithosphere - thick ice sheet) to lake gauge data for the upper Great Lakes relative to Goderich, Ontario. Comparison of predicted present differential movement using the minimum deformation model (i.e. thick lithosphere - thin ice sheet) to lake gauge data for the upper Great Lakes relative to Goderich, Ontario. The interpretation of the lake gauge data has been altered to include the station at Ludington, Michigan. Isobases of the Algonquin shoreline by Goldthwait (1908, 1910). Predicted isobases of the Algonquin shoreline (using the Kirkfield outlet at 10,500 B.P.). The maximum and minimum models are compared. The dashed line is the isobase at the present level of Lake Michigan. The Algonquin shoreline is predicted to be submerged south of this isobase. Comparison of predicted Algonquin shoreline deformation to Goldthwait's observed Algonquin shoreline in the northern Lake Michigan basin. The predictions were calculated for a lake using the Rirkfield outlet 10,500 B.P.. Evenson's isobases of the Glenwood shoreline (Evenson 1972, 1973). Profile of near-shore features plotted along a north-south transect using an ear-west isobase trend. Profile of near-shore features plotted along a north-south transect using a N25W isobase trend. Location of the lacustrine plains investigated in this study shown here on a surficial map of Michigan by Farrand and Bell (1982). xi 56 57 59 61 62 70 74 75 79 Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Allegan County embayment shoreline data found above 201 m (660 ft) elevation plotted in profile using an east-west isobase trend. Profile of the Muskegon/Ottawa lacustrine embayment data along a north-south transect using east-west trending isobases. ‘ Comparison of shoreline correlation across Lake Michigan using N25W and east- west trending isobases. With the N25W isobases a shoreline in Michigan at 220 m correlates with a shoreline at 198 m directly to the east in Wisconsin. Map showing the distribution of selected sites. Cross-section of the Hagar site interpreted to be a transgression. Topographic map of the Slocum sand ridge area. Bridgeton Quadrangle, Michigan, 7.5 minute series (topographic) provisional edition 19854 Schematic profile of the Slocum sand ridge and topographic setting. Cross-section of the Claybanks site. Topographic map of the White River delta area. Hesperia Quadrangle, Michigan 7.5 minute series (topographic) provisional edition 1985. Profile of near-shore features plotted along a north-south transect using an east-west isobase trend. Line indicates a possible interpretation of transgression. Profile of near-shore features plotted along a north-south transect using a N45W isobase trend. Line indicates a possible interpretation of a transgression. Comparison of numerical calculations to the observed near-shore features along a north-south transect. xii 81 83 85 87 88 94 96 98 101 103 104 106 Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure A.16 A.17 A.18 Ice Sheet Thickness 30,000 B.P. Ice Sheet Thickness 25,000 B.P. Ice Sheet Thickness 21,000 B.P. Ice Sheet Thickness 18,000 B.P. Ice Sheet Thickness 17,000 B.P. Ice Sheet Thickness 16,000 B.P. Ice Sheet Thickness 15,000 B.P. Ice Sheet Thickness 14,000 B.P. Ice Sheet Thickness 13,000 B.P. Ice Sheet Thickness 12,000 B.P. Ice Sheet Thickness 11,000 B.P. Ice Sheet Thickness 10,000 B.P. Ice Sheet Thickness 9,000 B.P. Ice Sheet Thickness 8,000 B.P. Ice Sheet Thickness 7,000 B.P. Ice Sheet Thickness 6,000 3.1:. Ice Sheet Thickness 5,000 B.P. Ice Sheet Thickness 2,000 B.P. xiii (m) (m) (m) (m) (m) (m) (m) (m) (m) (m) (m) (m) (m) (m) (m) (m) (m) (m) Thick Thick Thick Thick Thick Thick Thick Thick Thick Thick Thick Thick Thick Thick Thick Thick Thick Thick Ice Ice Ice Ice Ice Ice Ice Ice Ice Ice Ice Ice Ice Ice Ice Ice Ice Ice Sheet Sheet Sheet Sheet Sheet Sheet Sheet Sheet Sheet Sheet Sheet Sheet Sheet Sheet Sheet Sheet Sheet Sheet 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure A.21 A.22 A.23 A.24 A.26 A.27 A.28 A.29 A.3O A.31 A.32 A.33 A.34 A.35 Ice Sheet Thickness 30,000 B.P. Ice Sheet Thickness 25,000 B.P. Ice Sheet Thickness 21,000 B.P. Ice Sheet Thickness 18,000 B.P. Ice Sheet Thickness 17,000 B.P. Ice Sheet Thickness 16,000 B.P Ice Sheet Thickness 15,000 B.P Ice Sheet Thickness 14,000 B.P. Ice Sheet Thickness 13,000 B.P. Ice Sheet Thickness 12,000 B.P. Ice Sheet Thickness 10,000 B.P. Ice Sheet Thickness 9,000 B.P. Ice Sheet Thickness 8,000 B.P. Ice Sheet Thickness 7,000 B.P. Ice Sheet Thickness 6,000 B.P. Ice Sheet Thickness 5,000 B.P. Ice Sheet Thickness 2,000 B.P. xiv (m) (m) (m) (m) (m) (m) (m) (m) (m) (m) (m) (m) (m) (m) (m) (m) (m) Thin Thin Thin Thin Thin Thin Thin Thin Thin Thin Thin Thin Thin Thin Thin Thin Thin Ice Ice Ice Ice Ice Ice Ice Ice Ice Ice Ice Ice Ice Ice Ice Ice ICE Sheet Sheet Sheet Sheet Sheet Sheet Sheet Sheet Sheet Sheet Sheet Sheet Sheet Sheet Sheet Sheet Sheet 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure 3.12 Differential Deformation (in meters) Thick Ice Sheet - Thin Lithosphere 25,000 B.P. Differential Deformation (in meters) Thick Ice Sheet - Thin Lithosphere 18,000 B.P. Differential Deformation (in meters) Thick Ice Sheet - Thin Lithosphere 15,000 B.P. Differential Deformation (in meters) Thick Ice Sheet - Thin Lithosphere 10,000 B.P. Differential Deformation (in meters) Thick Ice Sheet - Thin Lithosphere 5,000 B.P. Differential Deformation (in meters) Thick Ice Sheet - Thin Lithosphere 1,000 B.P. Differential Deformation (in meters) Thick Ice Sheet - Thick Lithosphere 25,000 B.P. Differential Deformation (in meters) Thick Ice Sheet - Thick Lithosphere 18,000 B.P. Differential Deformation (in meters) Thick Ice Sheet - Thick Lithosphere 15,000 B.P. Differential Deformation (in meters) Thick Ice Sheet - Thick Lithosphere 10,000 B.P. Differential Deformation (in meters) Thick Ice Sheet - Thick Lithosphere 5,000 B.P. Differential Deformation (in meters) Thick Ice Sheet - Thick Lithosphere 1,000 B.P. Differential Deformation (in meters) Thin Ice Sheet - Thick Lithosphere 25,000 B.P. 149 150 151 152 153 154 155 156 157 158 159 160 161 Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure 8.14 8.17 8.18 8.19 3.20 8.21 8.22 8.23 8.24 Differential Deformation (in meters) Thin Ice Sheet - Thick Lithosphere 18,000 B.P. Differential Deformation (in meters) Thin Ice Sheet - Thick Lithosphere 15,000 B.P. Differential Deformation (in meters) Thin Ice Sheet - Thick Lithosphere 10,000 B.P. Differential Deformation (in meters) Thin Ice Sheet - Thick Lithosphere 5,000 B.P. Differential Deformation (in meters) Thin Ice Sheet - Thick Lithosphere 1,000 B.P. Differential Deformation (in meters) Thin Ice Sheet - Thin Lithosphere 25,000 3.9. Differential Deformation (in meters) Thin Ice Sheet - Thin Lithosphere 18,000 B.P. Differential Deformation (in meters) Thin Ice Sheet - Thin Lithosphere 15,000 B.P. Differential Deformation (in meters) Thin Ice Sheet - Thin Lithosphere 10,000 B.P. Differential Deformation (in meters) Thin Ice Sheet - Thin Lithosphere 5,000 B.P. Differential Deformation (in meters) Thin Ice Sheet - Thin Lithosphere 1,000 B.P. xvi 162 163 164 165 166 167 167 168 168 169 169 Table 3.1 LIST OF TABLES Comparison of median grain sizes. xvii 91 CHAPTER 1 -INTRODUCTION 1.1 Definition of the Problem What is believed by glaciologists and geophysicists about the Laurentide ice sheet, the structure of the earth, and its response to a surface load (Walcott 1970, Paterson 1972, Andrews 1974, Clark et al. 1978, Wu and Peltier, 1983, Mayewski et al., 1981) is contradicted by nearly a century of field work in the southern Lake Michigan basin by glacial geologists (e.g. Goldthwait 1906, 1907, 1908, Leverett and Taylor 1915, Hough 1958, and Evenson 1972, 1973). These glacial geologist among others have deduced from field data of relict shorelines that the region south of the Algonquin ”hinge line", depicted in Figure 1.1, has remained'stable for the last 12,000 years even though it was, according to glaciologists, under a substantial thickness of ice during the late Wisconsin ice age (Hughes et al., 1981, Boulten, et al., 1985). The claim that little or no isostatic rebound has-occurred in this area over that time period directly contradicts the expected results of normal isostatic processes as described by geophysicists '(Clark et al. submitted; Hendriks et a1. 1988).‘ This study uses a deductive approach and new field data (Timmermans 1988) to analyze the disagreement between the empirical interpretations and theoretical calculations. A numerical model of isostatic processes is used to predict deformations, which can be tested by comparison to field .cowmom 03:3 anon". on» a.“ acouu no.“ 5|...ch cocwucoouwz upon as» one goes” emcee. nauseouae on» no compound are .H.a ounces /Q\_ , _ S... 8...: ._.n=._n5 b M 3 observations in the Lake Michigan basin. The deformation of shorelines is a complex system. and it is necessary ‘to consider several variables (e.g. ice thickness and history, earth rheology, geoid perturbations, changes in outlets, etc.). It is well beyond the scope of this study to evaluate each area where discrepancies could occur. However, recent studies have shown that nearly all the shoreline data around the Great Lakes region can be explained adequately without relying on the existence of hinge lines (Clark et al. 1978, Larsen 1987, Timmermans et al. 1986) . The exception is the southern Lake Michigan basin.‘ Here a range of likely ice sheet histories or earth rheologies would not produce the observed shoreline deformation (Hendriks et al. 1988, Timmermans 1988). This study considers only two ice sheet histories and two earth rheologies, and concentrates on the interpretation of field data within the southern Lake Michigan basin as a possible source for the contradiction between theoretical calculations and empirical data. Specifically, this study examines the interpretations of data south of the Algonquin hinge line from both an empirical and theoretical perspective. The interpretations of the ancient shorelines in the southern Lake Michigan basin are compared to other data such as lake gauge deleveling data and recent interpretations of younger shorelines. The shoreline data are also examined for regional differential tilting, local tilting, and 4 correlation to glacial lake stage Chronologies. The field area 'where new' data were collected for this study ‘was limited to the region shown in Figure 1.2. An overview of the glacial and post-glacial history of the Lake Michigan basin is presented in Section 1.2. An examination of the traditional‘ shoreline model and the theoretical model for the region is presented in Chapter 2. Chapter 3 focuses on the new shoreline-data produced by this study and its significance to the mode of glacio-isostatic rebound in that region. The traditional shoreline model along with the new field data for the southern Lake Michigan basin are used to test the validity of the numerical model for the area. The numerical model, which simulates normal isostatic processes, has been successful in predicting shoreline emergence and submergence for the past 18,000 years worldwide in sea level studies (Clark et al. 1978, Wu and Peltier 1983) and in the upper Great Lakes (Clark et al submitted, Timmermans et al. 1986, Hendriks et al. 1988). 1.2 Glacial and Post-Glacial History of the Lake Michigan Basin The interpretation of the history of the glacial and post-glacial Great Lakes is a classical problem in geology. The problem integrates many areas of geology (e.g. glacial geology, sedimentology, geophysics, etc.). The summary of .ucouu 00H asawxca one coda coca: casucocad 0:» cu mwcucoaunaou ca noun acouu macaw no coflucooq .~.H ounces _ Sol .8. 585. ._.n=.._n_D b 6 the Lake Michigan basin history which follows demonstrates its multidisciplinary nature. Throughout the last 15,000 years the Great Lakes basins have been occupied by several different proglacial and post- glacial lake stages. These different stages were caused by changes in the location and elevation of the controlling outlet(s). During the late Pleistocene and Holocene times these outlets changed due to ice blockage, erosional incision, and glacio-isostatic rebound. Figure 1.3 indicates the locations of the major outlets important to the lake stratigraphy of the three Upper Great Lakes. The different lake stages associated with the changing outlets have formed beaches both above and below the present levels of these lakes. These beaches were deformed relative to the present geoid due to gravitational mass attraction and by isostatic uplift and subsidence. The following summary for the Lake Michigan Basin may not be agreed upon by all researchers working in the Great Lakes area, however, an attempt was made to keep the overView consistent with recent summaries (e.g. Eschman and Karrow 1985, Larsen 1987, and Hansel et a1. 1985). The rise (or fall) from one lake stage to another has left evidence of near-shore conditions over a broad range of elevations around this Great Lake. However, the controlling mechanisms of lake level change have caused certain lake levels to be occupied for longer (or several) periods of idly}! H M Sault St. Marie [eSt. Griz A- . 0 North Bay .~~w’ O Kirkfield fl ' ort Huron J L 2 \Chicago Pi 1.3. Outlets of importance in the upper Greet Lakes area. Ch cago, Port Huron, Kirkfield, and North Bay were the four major outlets controlling the lake level in the Lake Michigan basin throughout the past 15, 000 years. time. Therefore, certain lake stages found at particular elevations can be more easily identified in the Lake Michigan basin. The lake level change, caused by a change in outlet location or eleVation, can be initiated by ice blockage (or removal), outlet erosional incision (Hough 1958), or a change in discharge into (or out of) the lake basin (Hansel and Mickelson 1988). It is important to realize that if the basin is deforming, shorelines near the controlling outlet(s) will likely be occupied longer and more. often. For example, if a basin has two outlets at opposite ends of the basin (as in the Lake Michigan basin) and one of the outlets is lower but repeatedly covered and uncovered by ice, the higher outlet will be repeatedly reoccupied. Each time the lower outlet is blocked the higher outlet will control the level of the lake. Figure 1.4 demonstrates the relative position of each water plane as the higher outlet is reoccupied during differential tilting of the basin. It is clear that no matter how much uplift has taken place at the outlet itself each time it is reoccupied, the lake level near the outlet will return to the same level relative to the last lake stage, whereas away from. the outlet the shorelines formed. during' previous lake stages are never reoccupied, unless the land is depressed again by ice advances. Several lake stages in the Lake Michigan basin have Figure 1.4. Dispersion of shoreline features to the north. As the basin tilts through tine the outlet area is reoccuppied while Ihoreline features to the north are dispersed. 10 used the Chicago outlet when more northerly lower outlets were covered. by ice. Three distinct levels have been recognized in the vicinity of the Chicago outlet. Traditionally, these three levels are collectively referred to as Lake Chicago. The levels are the Glenwood level (195 m, 640 feet), the Calumet level (189 m, 620 feet), and the Toleston level (184 m, 605 feet). The lake stages associated with the lower more northern outlets are not recognized in the subaerial lake stratigraphy record or are sub-horizontal south of the Algonquin hinge line. Figure 1.5 is a summary of the lake stages in the Lake Michigan basin from Hansel et al. (1985). The figure depicts the approximate extent relative to the modern Lake Michigan basin and times when these stages existed. Near-shore features associated with the Glenwood stage are found around the Chicago outlet at an elevation of 195 m (640 feet). Evenson (1972) believes this shoreline rises to the north due to isostatic rebound to a maximum elevation up to 201 m (660 feet) to the north due to isostatic rebound. Earlier workers, Goldthwait (1907, 1908) and Alden (1918), believed this shoreline was undeformed and remained at the 195 m (640 feet) level everywhere (see Section 3.1 for a complete discussion of these data).- The Two Creeks retreat followed the Port Huron advance and the high Glenwood stage of Lake Chicago ended. During this retreat it is likely that the ice retreated north of 11 “m" H. . 1‘ 6! O I “III “V une may“! . M: 0mm GI. . ammo—- mum-Ime-ens-e-nsum m. “humane-em"! smear-woodlan- Isms-mood!” .QCOO.--‘ + ) b_,,-,-. \ I _..-o~:-"‘€ “Verb-ea ”a?” m mums—mutant ammo-u 0-0 ..~'.. I .. O ...-o O" mm -:.:~ : “9:.”- V. fl." Q .m-‘I’M “mu-lune kWh-shale tumult-O Figure 1.5. Late Wisconsinan and Holocene lake phases in the Lake Michigan basin from Hansel et al. (19851:). 12 theStraits of Mackinac (Hansel et al. 1985) causing the level in the Lake Michigan basin to drop below the present water plane. The Two Creeks retreat ended with the Two Rivers advance, the last major advance of ice into the Lake Michigan basin. The Two Rivers advance closed the northern outlets causing a rise in lake level to the level of the Chicago outlet. This stage has been identified in the Chicago area at an elevation of 189 m (620 feet) and is referred to as the Calumet Stage. Historically the Calumet stage was thought to be the second of three stages of proglacial Lake Chicago. The third level was referred to as the Toleston stage and was found at an elevation of 184 m (620 feet). However, recent radiocarbon dating of near-shore features in the Chicago area found at the Toleston level (184 m, 620 feet) suggest the level was more likely occupied by the post-glacial Lake Nipissing stage (Hansel et al. 1985). A Lake Chicago age stage at the Toleston level is not substantiated by radiocarbon dating. Following the Two Rivers advance, the ice front retreated from the Southern Peninsula. The opening of the Straits of Mackinac allowed the lake level to drop substantially in the Southern Lake Michigan basin. At this time both the Lake Michigan and Lake Huron basins were occupied by Lake Algonquin. Historically this lake was believed to be controlled by the Kirkfield, Port Huron, and 13 Chicago outlets (Goldthwait 1908) . The Port Huron and Chicago outlets are both located south of the Algonquin hinge line and were considered stable and at the same elevation. The rebounding Kirkfield outlet was thought to have risen isostatically bringing the lake level to the elevation of the stable outlets. At this time Lake Algonquin was believed controlled“ by three outlets simultaneously. The Kirkfield outlet continued to rise and was abandoned leaving Port Huron and Chicago as the controlling outlets. Recently this concept of Lake Algonquin has been challenged. Some workers in the Great Lakes now believe Lake Algonquin was controlled primarily by the Kirkfield or more northerly outlets (Hansel et (al. 1985, Larsen 1987, Kaszycki 1985). These workers believe the level of this lake was ~below the present water plane in the southern Lake Michigan basin. Figure 1.6 illustrates the extent of this lake stage according to these recent reports. Following the deglaciation of the Straits of Mackinac for the final time (approximately 11,000 yr B.P.) the Lake Huron and Lake Michigan basins had very similar histories. When the Straits were inundated, the basins were controlled by the same outlets. Northward retreat of the ice front resulted in the opening of even lower isostatically depressed outlets. Approximately 10,000 years B.P. the North Bay outlet became ice free. This low outlet allowed 14 y) {\"T" e I - W21. , .\ / \ Figure 1.6. Larson's interpretation of the Main Algonquin level in the upper Great Lakes from Larsen (1987). Note the low water level in the southern Lake Michigan basin. 15 the levels in the Lake Michigan to drop dramatically to the Chippewa stage. The Lake Michigan basin was possibly divided into two separate basins (Larsen 1987). Isostatic rebound of the North Bay region resulted in a steady rise in lake level for several thousands of years. During the low level stages, controlled by the North Bay outlet, Lake Chippewa in the Lake Michigan basin drained into Lake Stanley in the Lake Huron basin by a channel incised into the Straits of Mackinac.- Figures 1.7 and 1.8, from Larsen (1987), demonstrate the extent of the low lake stages and the Nipissing Lake stage respectively in the Lake Michigan and Lake Huron basins. North Bay remained the controlling outlet until isostatic rebound raised it above the elevation of the Port Huron and Chicago outlets. As drainage switched to these southern outlets the level in the Lake Michigan basin reached the Toleston level (184 m 620 feet). The North Bay outlet was abandoned and the level of Lake Nipissing began to fall due to erosional incision. This decline in lake level continued. to the ‘modern levels of ‘Lake ‘Michigan. Figure 1.9, from Hansel et al. (1985), summarizes the glacial phases, lake stages, outlets, and lake level elevations for the Lake Michigan basin. The change in lake level due to isostatic rebound and ice blockage of outlets is discussed further and compared to model predictions in Section 3.2. 16 eeuouncca oeue cocoon oxen ecu Cu 1! -II “(I ”’0! “I! A 4 A A A m ”0| men I L .‘l ‘8 A L ..nneoac .cees sues eueuuso cue nuance seen» .He so «once: souu canon secured: euce>e «edueuc are unseen axed no >uo~ocounu .5." shaman warn.» - . u [1 El 8} _ _ _ _ _ _ _ _ _ _ _ _ _ . . II p. .- .. . .. . . .. . . . . . .. Q I . .-.e .. . . . _ _ _ {r :0! 5532.3 i . 088:: is... I. tee to .1: 1 w .3... as .5 £9.38: U loll . nflfifi S :3... a 7 . el ig‘E . rbgw Y T V .1 -0 -0 “It .10 .84 V V f T T -00 -‘I V '4 ‘SIVIA mm .1. s m. 2m 304:6 50).; 03a “318; mg.— uulta . “a... .398 at! 9:80:43th deem 17 - J Figure 1.8. Chippewa and Stanley low levels in the Lake Michigan and Huron basins from Larsen (1987). - " €375 lush-h "Summon-amenanum" '4 e I} ‘ ‘ - V . ' 1 "f . ‘v ' .9' .-:. .1, .' &. ' 0 I . 11,1 .0 1.9;; ' f‘! g: ‘ ‘MMWQWMy . :r' ~.' fl" ,9".,. \ I ' ~ ~,- .-.-,.3 ..:..‘ , ~- ""‘z a I“: Auntiv ’ "’3 1., \u Q . = e... I 0 ' t ‘ ’. B I“ . r ; ‘1'. i ‘ I. ‘1 - ’1 CWMW manna Figure 1.9. Extent of the late Nipissing and Algoma Great Lakes from Larsen (1987). ‘ CHAPTER 2 - THE EMPIRICAL AND NUMERICAL MODELS 2.1 The Traditional Shoreline Model for the Southern Lake Michigan Basin The presence of glacio-isostatic hinge linesin the Great Lakes area was first proposed by Goldthwait (1908). The belief in the Algonquin hinge line and subsequent Lake Michigan basin lake level interpretations based upon this belief is here referred to as the traditional model. Goldthwait and the workers who followed his ideas used empirical data from around the Lake Michigan basin to support the hinge line model. 2.1.1 The Historical Development . Goldthwait developed the traditional shoreline model when, after years of mapping deformed shoreline features around Lake Michigan, it was apparent that several ancient shorelines converged southward to a common isobase (Figure 2.1). This led Goldthwait to consider three different processes for developing this type of record. Goldthwait reasoned that either 1) the beaches were deformed that way at the time of formation due to gravitational attraction from the ice sheet mass, 2) the point of convergence was located on a line of equal uplift which passed through the controlling outlet, or 3) the point iof convergence was a "hinge" such that north of the hinge line the surface was affected by glacio-isostasy while the land to the south 18 19 MM .1 CHILI! Figure 2.1. The Algonquin, sub-Algonquin, Nipissing, and Algoma strandlines interpreted by Leverett and Taylor (1915) using data from Goldthwait. Note convergence of these beaches just north of the Port Huron outlet isobase (from Hough 1958). 20 remained stable. Figures 2.2a through 2.2c illustrate Goldthwait’s three working hypotheses. Goldthwait ruled out the first hypothesis of ice attraction based on the nature of the curve. He reasoned that as the ice sheet retreated so would the perturbation in the gravitational equipotential surface controlling the lake surface, causing the curve to retain approximately the same amount of deformation as it migrated northward with the ice sheet. This ice attraction process as envisioned by Goldthwait would only be valid if the earth were perfectly rigid. However this hypothesis can be rejected as the primary mechanism even for a non-rigid earth because most of the mass present in the ice sheet has since been replaced by rock due to isostatic adjustment causing the present gravitational equipotential surface to be nearly parallel to the one controlling the ancient lake surface (Wolf 1986). 'In this study, the numerical model of isostatic adjustment includes geoid perturbation resulting from mass transfer of both ice and mantle material. The second hypothesis considered by Goldthwait (see Figure 2.2b) had the point of shoreline convergence located on the same isobase as the controlling outlet allowing for continued deformation to the south in the form of submerged beaches. This theory' of’ continued isostatic adjustment throughout the entire Lake Michigan basin was proposed by Goldthwait's predecessor Spencer (1891). Spencer proposed 21 2.2a. Goldthwait’s ice Figure 2.21:. Goldthwait’s” outlet attraction hyptheds. control hypothesis. South North 8" 8 sum: a 0mm . . 3 9g ‘ I S 1 9"” $0..” on e W Modern Lake Michigan J Figure 2.2c. Goldthwait's hinge line hypothesis was accepted as the mechanism for causing shorelines to converge. 22 this model of isostatic uplift based on his data from the Lake Huron basin. Spencer stated: .At this time [Algonquin] a considerable area of the southern end of Lake Michigan was laid dry, as the beach bounding the Algonquin water should now be submerged to 2.90 feet below the waters of that modern lake. But the northern part of the Michigan and Huron basins was filled to an elevation far above their present surface, . . . This hypothesis which Goldthwait considered indicated that the point of convergence was only an apparent hinge line where the Algonquin shorelines crossed younger less deformed shorelines such as the Nipissing or Algoma, and continued downward beneath the present lake level as shown in Figure 2.2b. This apparent hinge line hypothesis proposed by Spencer (1891), was tested by Goldthwait by the construction of isobases from the available data. Goldthwait showed that when isobases were drawn across Lake Michigan and extrapolated across the State of Michigan the isobase which passed through the Port Huron outlet fell well south of the point of convergence, while the isobase through the Kirkfield outlet projected too far north. According to Goldthwait, this ruled out the second hypothesis. With the absence of any conflicting data the process of elimination led Goldthwait to conclude that the southern 23 part of the Michigan Basin had remained stable and that the third hypothesis of the hinge line was the correct interpretation. Since this initial work (Goldthwait 1908) no one has questioned his reasoning. iHowever, it is important to realize that his interpretation was based on the paucity of conflicting data. Section 2.1.2.2 points out several areas of research which post-date Goldthwait's work that are in conflict with his interpretation. Possibly even more damaging to Goldthwait’ s interpretation is an evaluation of the rigid earth bias which prompted his ideas. Larsen (1987) points out in his summary on the evolution of the hinge line model, that Goldthwait's interpretation could have been influenced by T.C. Chamberlin who did not believe in glacio-isostasy. Chamberlin. preferred the ideas of a rigid earth. Goldthwait's belief in a rigid earth is also evident in his analysis of the shoreline tilting due to gravitational attraction of the ice sheet. Goldthwait's hinge line concept was adopted and used as the working hypothesis in the Great Lakes Iarea (e.g. Leverett and Taylor 1915, Hough 1958, Bretz 1964, Evenson 1973). As research continued more hinge lines were suggested from field data in the Lake Michigan basin as well as in Lake Superior, Lake Huron and Lake Erie basins (Hough 1953 p. 136) . Of the many workers who followed Goldthwait 24 only Evenson (1972, 1973) worked extensively on the older shoreline features in the Lake Michigan basin. Evenson's study concentrated. on shorelines south. of the .Algonquin hinge line in the Lake Michigan basin and showed a deformation history for the southern part of the basin which was slightly different from. the complete stability interpreted by the other workers. Evenson’s curve showed a region of slight tilting affecting the Glenwood stage of Lake Chicago (c.a. 13,000 BP) as indicated in Figures 2.3 and 2.4. That Evenson believed no tilting took place in the region after 12,000 BP is seen in his interpretation of the Calumet shoreline (see Figure 2.4). Evenson's :model for' the shorelines of Lake Chicago (13,300 - 11,400 BP) along with Goldthwait’s model for Lake Algonquin, Nipissing, and Algoma (11,400 - present) is cited here as the traditional model for the subaerial record of the shorelines in the southern Lake Michigan basin. Figure 2.5 summarizes the traditional shoreline model. 2.1.2 Traditional Model and Conflicting Empirical Data. Since Goldthwait's monumental work (Goldthwait 1908) on the . abandoned shorelines around the Lake Michigan basin, several researchers have presented interpretations of new data which are in conflict with Goldthwait's interpretation of the Algonquin hinge line. These recent interpretations are more consistent with Goldthwait's predecessor Spencer (1891) . A summary of the interpretations and supporting 25 Milwaukee e Figure 2.3. Evenson's isobases of the Glenwood shoreline (after Evenson 1973). 26 .33.. seeder” heady 608.3835 .52— : emcee nouns—co 25 can 3 c8 3 0 nova 53.6.33 ~53 ac 02.030 03.3 no one»- coobdedc 05 each 5 dog diox— dcuHoi cg ocean—ca 05 Lou cacao 250."er Foo-Boon in sun-HE § *6 5 3 § 1 01.. 1 ova-rm! amp!!! 0m M18 0mm!" men Intros «was put—m 27 (w) uonemala .nouco>m one uwcszucaoo an couounuouca uc Honda onaaouocu Hccoauaccuu on» we hucaaom .m.~ ousmwh as: ooesma omm our o r l .90.. oxen Emacs. room one - _o>o.._ mEouZ - 80 £33 :_:ccom_< w oc_mm_c_z o9 - _o>o._ 6E2m0 cum I\| cum com ,r 66.. 3025.0 7 no . a... a. so .. t.» Bu kw. we % w. 9 - oo oo o/ «w. to. m. % stoz _ooos_ Escape; .6 meEsm (u) uouenela 28 data which are inconsistent with a "hinge line" mode of glacio-isostasy in the Lake Michigan basin is presented in sections 2.1.2.1 through 2.1.2.4. 2.1 2.1 The Response of the Earth to a Surface Load. The effect upon vertical deformation of the earth from loading by ice sheets (on land) or water (in the ocean basins) has been extensively researched (e.g. Cathles 1975, Clark. et al. 1978, Peltier 1980, Walcott 1970). These studies do not suggest sharp lateral discontinuities in isostatic adjustments exist and theoretical calculations have not purposely included such discontinuities. Although this global data set does not include the Lake Michigan data south of the Algonquin hinge line specifically, the paucity of isostatic hinge lines elsewhere in the world is significant. 2.1.2.2 Lake Gauge Data - The interpretation of differential tilting from lake gauge data around the Great Lakes also questions the validity of the hinge line hypothesis. Many lake level gauges have operated continually for more than 80 years in the Great Lakes region. Following ideas first advocated by G.K. Gilbert (1898), these records can be used to determine present rates of differential tilting within any of the Great Lake basins. 29 Several workers have analyzed differential uplift trends around the Great Lakes from lake gauge data (e.g. Moore 1922, MacLean 1961, Clark and Persoage 1970, and Coordinating Committee on Basic Hydraulic and Hydrologic Data in 1977). The recent studies of the Coordinating Committee and Clark and Persoage both interpret the lake gauge data as indicating vertical differential movement south of the Algonquin hinge line continuing at present. The Coordinating Committee also includes a complete discussion on technique and presents graphs of relative vertical movements between each lake gauge station. Figure 2.6 shows an interpretation of present rate of uplift across Lake Michigan and Lake Huron based on their data (Clark et al. submitted). The rate of differential uplift between any two lake gauge stations can be found by plotting the differences in lake level measurements between the stations through time. The magnitude of the uplift and the number of years of record are important to the reliability of the interpretation. The location of the lake gauge stations with long records are shown in relationship to the Algonquin hinge line in Figure 2.6. Differential tilting between the Calumet, Milwaukee, and Sturgeon Bay harbors is of particular interest to this study. The data recorded since the Coordinating Committee's study have been incorporated and are included in Figures 30 2.6. Present rate of vertical movement in the Lake Michigan and uronbaslnsn-otnlakelevelgeugedetarelativetocoderlch.0nterlo. 31 2.7, 2.8, and 2.9. These figures show the differences in lake levels recorded between these stations through time. The mean summer lake level at each station was used as the lake level for that year. Figure 2.7 shows the relationship between Calumet and Harbor Beach stations. The record is shown from the turn of the century to 1986. The graph shows that through time the water level is going down at Harbor' Beach relative ‘to Calumet Harbor at a rate of 1.19 mm/year. This indicates the rate of differential uplift between the stations with Harbor Beach being uplifted relative to Calumet. The proximity of the Harbor Beach station to the Algonquin hinge line strongly suggest that differential tilting is taking place in the area thought to be stable in the traditional model. Figure 2.8 is a graph of the difference between the Milwaukee and Sturgeon Bay stations through time. The trend of the curve would indicate that there is 1.20 rum/year differential uplift to the north between these stations. Again the location of the proposed Algonquin hinge line in relationship to the Sturgeon Bay station suggests differential tilting throughout the region considered to be stable in the traditional model. The traditional model (see figure 2.5) has the Calumet shoreline mapped as horizontal as far north as Manistee, Michigan (Evenson 1972). However, given the present rate of differential vertical movement 32 653 A963 Seem hobs-fl as e65 358 «0838 as e—eeeu ex! wean—s- 56: Ga ensur- Hebe-loo . It}: 1.;1 ———- _ . >1 . it e < .l 06 I. «.0 [N6 33 .033 £36.34 155 men goons—5m ac oeofl e558 Lennon ecu—35:: no e72: oi hogs doe: .o.m ennui he» ommr 009. 03.. cum? comp corn I. . . _ . . . _ . no.0- , 1 3. cm. I amazes mm; . . "soc so: some... 1 mm o. 8. I . f . L we. ...- , i - .. w r e. 1 S. m. m ON. I . ‘ I; . r M. L moo m. o r Br ,. I a L e 9 i .c‘ on I c .1 . r moo ‘ .. IL Foo 8 ll m Pd 34 .25.. A9285 connota— ac 035 358 «0838 as e72: 8:: huge ace: in eunuc— Us»; Rena 3.9.. “3oz can: «88$ 35 suggested by the lake gauge data throughout this area, this 11,800 year old shoreline should have undergone measurable deformation. These data suggest the Calumet shoreline in this region should have undergone at least 14 m (46 feet) of diffential tilting. This is more than double the deformation reported by Evenson for the older Glenwood shoreline. Figure 2.9 shows the relationship between observed lake levels at Calumet and Milwaukee harbors. Like the previous curves the difference in lake levels through time shows differential movement between the two stations. The present rate of movement here, however, is observed to be up in the south as opposed to the north in previous examples. Observations of empirical data and theoretical modeling of’ glacio-isostatic ;processes suggest the jpresence of’ a fore-bulge in front of the ice sheets- Upon retreat of the ice sheets, the fore-bulge migrates following the ice sheets. The presence of a fere-bulge indicates that areas of active isostatic deformation will experience downward differential tilting as the fore-bulge ‘migrates past. Therefore, the observation that Milwaukee is subsiding relative to Calumet and Sturgeon Bay can be explained by means of normal isostatic processes. These relative movements between stations are impossible to reconcile with the_empirical model. 36 2.1.2.3 Observed Deformation of Water Planes in Southern Michigan Basin. Spencer (1891) believed that the Algonquin shoreline continued beneath the present lake level in the area which was later proposed to be stable by Goldthwait (1908). As described earlier, Goldthwait ruled out this hypothesis based on his interpretation of isobases in the Lake Michigan Basin. Since Goldthwait's work there has been little attempt to trace the Algonquin' shoreline to the south beneath the present lake level. Recently Larsen (1987) has used the altitude of lacustrine red clays within the Lake Michigan basin to test for continued isostatic deformation south of the Algonquin hinge line. His interpretations show that the deposition of red lacustrine clay is generally contemporaneous with the Algonquin shorelines, and that the transition from red clay to gray clay occurred about 9,800 to 9,900 yr B.P. Larsen suggests that the upper limit of red clay deposition rises to the north. Figure 2.10 show Larsen's interpretation of the progressively higher limit of red clay to the north. Larsen (1987) has also used the available data recording the Chippewa Unconformity formed during the Chippewa and Stanley low lake levels, and controlling outlet elevations to suggest it is also tilted south of the Algonquin hinge line. He points out, and shows in Figure 2.11, that the few available data points do form an 37 1 ~ Figure 2.10. Probale attitude of late-glacial red glaciolacustine clays of the Lake Michigan basin from Larsen (1987). a: "“"""‘ a: El ll--—--~ :‘::: a..-....:-;-««-nn “'9'” i: 1:: "'2 ii": 331 51 [I Figure 2.11. Larsen's interpretation of the late Chippewa water plane at about 8,000 yr B.P. for the Lake Michigan basin (from Larsen 1987L. 38 exponential curve which is consistent with normal isostatic processes (Andrews 1970). Larsen (1987) also presents a hypothesis for the convergence of shorelines to a common isobase which was not considered by Goldthwait. Figure 2.12 summarizes his interpretations of shoreline deformation in the Lake Michigan and Lake Huron basins. Larsen shows that it is possible to have converging shorelines caused by successively lower outlets to the north. Therefore,-the process of elimination, used by Goldthwait to propose the hinge line theory, is shown to not be conclusive. The presence of alternative theories which were not considered by Goldthwait and the presence of conflicting data mandates reeValuation of the hinge line and traditional shore models. Recent work in the Lake Huron basin (Kaszycki 1985) suggests that the Algonquin shoreline is tilted south of its hinge line. Kaszycki has used shoreline data to interpret differential tilting in Ontario. Her interpretations also conform to the ideas of normal isostatic processes. Figure 2.13 shows the interpretation of the Algonquin‘shoreline within this region along with the location of the proposed Algonquin hinge line. Recently several glacial geologists working in both the Lake Michigan and Lake Huron basins have challenged the subaerial presence of the Algonquin shoreline south of the hinge line. Karrrow (1985), working in the southern Lake I ——uene say can. 8 $ Ieeeeee tees! ” — lees“ lead ”290 i new 3 w ' . 2 , Ritual Late “0‘ 5 3 i' ' um use an .1 rec 880-4 E : i / SOC-I F g 3 \ him , e .l ‘ Anette do use are sec- 9 f f . o. EGO-l : O l i I / i U «04 3 i 4‘ .. see no. 8 2 I | I- 100 . tea-- 31‘“ ‘ ..: peas '5 i too- ;if'." L z '3' i 600 s «0- '1'3; . - I. ! Machines ale 3 i "°" .3:- e" a )- 0» 5 8 fl, . 'a' 5; ‘- laurel Escarpment 5 too- .-:,. // «is v , .. I’m "1 / * a" I '9‘ I“: . if z; i j I- :00 ee- “ ""‘g. _ A mm are. so. ' 3‘2: ”'34.. _‘.i- e um Meeaeule u Mares r ‘00 2' a lower ate-nul- v “i 0 one. " ' -33.. .5; ; ..... ‘40-! z: s . -..d -. ’.‘_t i i 3 bum " 3;: )3 s s i . ... . o' «in do sire «lo sic ciao Jo sire flsteaee la (Monsters Figure 2.12. Larsen's interpretation of the Algonquin shoreline data for the Lake Michigan and Huron basins. Note the deformation of the Algonquin shoreline beneath the present level of Lake Michigan south of the Algonquin hinge line (from Larsen 1987) . 40 e- uranium-“momma! Figure 2.13. Kaszycki's interpretation of the Algonquin water plane in the Lake Huron basin. Note the deformation of the Algonquin shoreline south of the Algonquin hinge line (for: Kaszycki (1985). I..- . cats-Is!“ tenses Moses L868" (1985) 8 ’ . D C. A-d Isl-sass “sens I tenses : .3.- ..—. “I... I'mese 1 I by” ‘ .—. ass-s tenses i Q ’ . P,“ + + m In 13.03133. 1 I.’ m ---- m 3123:. a /' _... 0 I C _ 5 [JP : M 5 . z p . I" /- u... g ‘ see- ; I _/' ' , 3 3 2 -’ + C o“' s . I ' I ! a z I. /' I.“ i ' | I."/ ’7’ o .1 ' . .“III I ’ ’_’ "'o'r .. Q P... I 0'” ’a” -" o' O ‘ I I e . 9’ ... k.’ ' " .” O/O’ Nose ' sJ/ Ieed —e--—'"‘""" III ‘7‘.“ less use Lees. I!" .3 = 4 - --- D... m ~0- .-- - em hen ..- . I z .3 4. .b J. :3 32 .. “alwommmsesueiseeswcmssswml Figure 2.14. Larsen's interpretation of the Nipissing and Algoma water planes in the Great Lakes showing continued detoraation of these §;:;n§ shorelines south of the Algonquin hinge line (from Larsen a . 41 Huron basin, have interpreted that the near-shore features previously thought to be Algonquin as Nipissing. Dating of shoreline features in the southern area of the Lake Michigan basin by Hansel et a1. (1985) also suggests the absence of a subaerial Algonquin shoreline. Also in the southern Lake Michigan basin Thompson (1985) showed Nipissing Lake deposits directly above Lake Chicago sediments. The absence of Algonquin sediments in the southern Lake Michigan and Lake Huron basins would be difficult to explain with the traditional model. On the other hand, this result would be expected if the area south of the hinge line is dynamic. 2.1.2.4 The Nipissing Shoreline Larsen (1985a), in a study of the Holocene Lake levels throughout the Lake Michigan and Lake Huron basins, suggests that the Nipissing shoreline is found at a lower elevation in the Chicago area than at Port Huron. Both of these areas are south of the Algonquin hinge line. Deformation of these relatively recent shorelines within ‘this region is inconsistent with the traditional model proposed by Goldthwait and adopted by later workers (e.g. Leveret and Taylor 1915, Hough 1958, and Evenson 1972). Figure 2.14 shows the interpretations of these recent shorelines made by Larsen (1985a). 42 2.2 The Numerical Model A. numerical model has been used in this study to facilitate the development of working hypotheses on the mode of glacio-isostasy in the southern Lake Michigan basin. The inconsistencies found in the long-accepted hinge line hypothesis has led to this deductive approach for developing hypotheses consistent with the current knowledge of isostasy. The numerical procedure is similar to the one described by Farrell and Clark (1976) who were intereSted in changes of sea level resulting from retreat of the ice sheets of the most recent ice age. The procedure for using the model to predict differential tilting of glacial lake planes is described by Clark (1980). The discussion included in this section is qualitative, and the reader is referred to the above references for the mathematical methods. 2.2.1 The Model Calculations and Assumptions In the model the earth is assumed to be spherically symmetric and viscoelastic. The elastic parameters and density structure of a Gutenberg-Bullen earthaare used. Viscosity and lithosphere thickness are assumed to be known for each model simulation. During the study various lithosphere 'thicknesses reflecting' the range. of interpretations in this field 'were used. These are discussed and compared to empirical data in sections 2.3 and 3.3. 43 The earth model is self-gravitating. Woodward (1888) recognized that the addition of mass on the earth's surface in the form of ice would cause perturbations in the earth’s gravitational equipotential surfaces. Static water levels, such as in the Great Lake basins, lie on gravitational equipotential surfaces. Therefore, perturbations in the gravitational potential surfaces must be addressed. Goldthwait (1908) used Woodward's concepts of gravitational perturbations to develop a hypothesis for the shoreline stratigraphy in the Lake Michigan basin (see section 2.1.1). Both Goldthwait and Woodward considered the earth to be rigid in their analysis. Subsequent work has shown this to be false. However, the change in equipotential surfaces during loading and unloading of ice sheets is still important in the analysis of deformation of ancient shorelines. Because the earth responds at a slower rate than the change in ice loads the system, at any given time, is likely to be out of isostatic equilibrium. A change in mass near a body of static water affects the shape of the equipotential surface upon which it rests and therefore affects the shape of any shoreline preserved during that period. a Self-gravitation within the model assures that the consideration of geoid perturbation due to mass attraction both by surface loading and mass transfer within the earth is accounted for at all times. In addition to its 44 gravitational equipotential effects, self-gravitation affects the rate and style of viscous flow of mantle material as it moves to accommodate changing surface loads (Cathles 1975) because the gravitational driving fbrce for relaxation is itself a function of the mass distribution. The effects of redistribution of mass within the earth, redistribution. of’ mass on the earth’s surface, and. the physical movement of the earth's surface through the ambient gravitational potential field are mathematically described by a Green function (Peltier 1974). If the history of loading and earth structure are assumed the potential perturbation is calculated by a convolution of the surface loads and the Green function. ' For simplification of the calculation the ice sheet is restrained to retreat (or advance) in 1000-year intervals. The ice sheet loads are approximated by discrete disc loads. Each disc may be thinned (or thickened) independently. The model calculation begins 30,000 years ago with the ice sheet covering only the Hudson Bay region. In the models the ice sheets are advanced to the glacial maximum 18,000 years ago. The advance is assumed a near mirror image of the retreat which followed the maximum (Clark per. comm.). Starting the model at the glacial maximum (18,000 B.P.) would assume the earth reached isostatic equilibrium during the last glacial maximum. 45 Wu and Peltier (1982) have shown that gravitational relaxation during late glacial and post-glacial times is not not highly sensitive to the ice history prior to the last glacial maximum. The earth model used in this study predicts the amount of deformation which has occurred in any gravitational equipotential surface relative to the earth's solid surface throughout the past 30,000 years. Therefore, not only the last deglaciation, but also the glacial advance, is included. 2.2.2 The Model Input Ice sheet history and earth rheology are used as input into the model. The ice sheet history input must include both the areal distribution of the ice front through time and the thickness. The ice sheet chronology in the Great Lakes area is well constrained relative to thickness (Mayewski et al. 1981, Prest 1969, Mickelson et a1. 1983). The thickness, however, is widely disputed. Because the earth model is linear, errors in the assumed thickness of the ice sheet will be linearly proportional to errors in the predictions. For example, if the ice sheet was in reality 10 percent thinner everywhere than assumed in the model the predictions would be 10 percent too large. The range in ice thickness estimation for the Great Lakes area is found in Hughes et al. (1981) and Boulton et al. (1985). Hughes et al. (1981) estimates the North American ice sheets to be in excess of 1500 m thick over the 46 Great Lakes region and 3500 m thick over the Hudson Bay region. Boulton et a1. (1985), on the other hand have estimated, based the basal shear properties of the sedimentary deposits of the Michigan Basin, that the ice sheets only maintained a thickness of less than 750 m in the Great Lakes area. Boulton’s ice sheet is estimated to thicken greatly north of the Michigan Basin (on the Canadian Shield) to over 2000 m over the Hudson Bay area. Figure 2.15 contrasts the thicknesses of Hughes' and Boulton's ice models. Hughes et al. 1981 considered the ice sheet to have a single dome over the Hudson Bay region. Boulton et al. (1985) believe the Laurentide ice sheet was double domed (see Figure 2.15). The thinner ice sheet would also be considered much more dynamic in the Great Lakes area. For this study a 5 degree latitude by 5 degree longitude grid was used to define the North America ice sheets outside of the Great Lakes area. For greater resolution of ice histories and thickness in the Great Lakes area a 2 degree latitude by 2 degree longitude grid was used (see Figure 2.17). The histories are similar to the isochrons of the Laurentide ice sheet given by Mayewski et a1. (1981) in this region. ' Ice sheet thicknesses similar to these ice models are used as input to the numerical model. Figure 2.16 contrasts the modeled ice sheets in profile from Hudson Bay to the 47 Single-domed 7 Thick Ice Sheet ,f" "‘ 1 .2?‘ 2 ‘57 330% \ '09 3:5] 3. 2:5 2 \\ R 1. 0. Ice Sheet Thickness(km) Double-domed ' Thin Ice Sheet 04 . .75- 2. ILZS' 3- ' -2.25 2:5 Figure 2.15. Casparison of ice sheets after a) Hughes et al. (1981) and b) Boulten et al. (1985). Thicknesses shown are for the late Wisconsinan glacial maxi-us (in kilo-eters). 48 Distance (kn) ’ 4 o 1000 2000 3000 ‘ D‘ouble' D'orfiea fhir‘u I‘ce‘sfieét ' f; 3 - — 30,000 SF - g _ --- 18,000 BP - g 2:. -------- ~\ "- 12.ooo BP .. a. _. \ ............ 7,000 SF . 8. . . .- a 3 .. o d - E :2 . 8 H lid Hudon Bgy Straits of lakinac Southern Indiania Grand Rapids s Figure 2.16. Colparison of ice sheets after a) Hughes et al. (1981) and b) Boulten at al. (1985). Thickness shown are in profile along , transects shown in Figure 2.15. 49 Figure 2. 17 . Grid for ice sheet representation in the numerical model. In the Great Lakes region the normal 5 x 5 degree latitude/longitude grid is reduced to a 2 x 2 degree grid to increase resolution there. 50 edge of the glacial maximum extent in the Great Lakes region at ‘various times. Interpretations of" deformation of’ the earth’s surface within the Great Lakes area is crucial in our understanding of both the ice thickness and earth rheology. Ice sheet thickness maps for selected times for both of the ice sheet models are located in Appendix A. Work with a variety of earth structures has been presented by Hendriks et al. (1988). Hendriks considered three different earth models in combination with these two different ice sheet histories. Hendriks et al. included the response ‘with respect to Iboth. lithosphere thickness and mantle viscosity. The evaluation of the six models indicated that no reasonable ice histories and earth rheologies could be used with the model to predict glacio- isostatic hinge lines in the Great Lakes. However, no discontinuities or lateral changes in earth structure were included in the models. Because of time limitations, this study has been limited to two earth models and two ice sheet histories with respect to the southern Lake Michigan basin shoreline data. Only changes in lithosphere thickness is considered in the two different earth models. The 112 km and 212 km thick lithospheres represent the range in assumed lithOSphere thicknesses proposed by Peltier (1984). The mantle is at a viscosity of 1022? for both models. 51 2.3 Numerical Model Results The numerical models described in Section 2.2 have been widely applied to isostatic deformation studies within the Great Lakes (e.g., Clark et al. 1985, Timmermans et al. 1986, Hendriks et al. 1987). The results of the numerical models used in this investigation are compared to empirical data from the Lake Michigan basin and summarized in Sections 2.3.1 through 2.3.3. The modelled results are also compared to the field data produced by this study in Section 3.3. Predicted deformations at selected times before present for each model are presented in Appendix B. It is important to realize that none of the models indicate stability south of the Algonquin hinge line for the past 12,000 years. 2.3.1 Modeled Outlet Chronologies . Outlet Chronologies play a very significant role in our understanding of the Great Lakes glacial and post-glacial history. The delineation of outlet elevation and history of outlet occupation through time derived from empirical data is used to test the results of the numerical models. The Lake Michigan basin has been controlled by several different outlets during' its late-glacial. history. The isostatic depression and subsequent rebound of the northerly outlets (e.g., Kirkfield and North Bay) above the level of the southerly outlets (Port Huron and Chicago) has greatly influenced the water levels within the basin. Figure 2.18 52 . M {:4 Sault St. Marie eSt. Groix , s North Bay eKirkfield ort Huron L hxcago , 1400 0.4- 700 A ' '21 1' ' 2‘ 5 150- '500 ‘; a " o a a“ -30. g .. 1 ’ 5 5° 9’ -100 a _ ‘3’ _ 5W — Outlet Elevation F—lOO T l l l l T l I I l l 13 ii 8 '7 6 3 1 Time (1000 years B.P.) Figure 2.18. Generalized lake lli an outlet chronology from empirical data. Note that the art Huron and Chicago outlets are stable through time except for erosion] incision. 53 illustrates the relative lake level and controlling outlet(s) for the Lake Michigan basin through time derived from empirical data. The stability of the Port Huron and Chicago outlets is required by the traditional model of isostatic rebound. Figure 2.18 illustrates that initially the Lake Michigan basin was controlled by the Chicago outlet. The Chicago outlet was later abandoned for lower isostatically depressed outlets in the north as they became ice-free. In the traditional model, the only change in elevation of the Chicago and Port Huron outlets is due to erosional incision. The outlet chronology for the Lake . Michigan basin is used to test the numerical models. Isostatic rebound of each outlet is predicted by the models. Figure 2.19 demonstrates the range in predicted results for the four outlets: Chicago, Port Huron, Kirkfield, and North Bay. The results indicate that the observed outlet chronology (see Figure 2.18) can be produced by the numerical models which do not constrain the Port Huron and Chicago outlets to be isostatically stable (see Figure 2.19). A significant difference does exist between the two predictions presented in Figure 2.19 with respect to the use of the Chicago outlet. Recent radiocarbon dating in the Chicago outlet area (Hansel et al. 1985a) indicates that the Chicago outlet was occupied during the mid-Holocene by Lake Nipissing. As shown in Figure 2.19, the numerical model 54 aoo :. ‘ 7 ‘ ‘ fl ‘ .. .' fry-«:22... 400 C. \\ ms... i... I I 4750 0 L \\ °‘°- am“! {’4' l . I: \ ‘ " , 10200 -400 :- \ “K-.. ’E’ . A ' ‘ o h: Thin Lith. » \ I 40'; ‘800: ‘1‘ , .1 Ice: Thick . . . J I 4 . . J _ £2 30 20 10 O V 800: - . . . . 1 . . FMM-“W 400 I:\ ~ s \ - c- I, ~ _ ~ \ ~ ’ ’4 I— Kirkfield(860 ft) 9600 "' NOV“) B°Y(7°° it) Eortl': Thiq Lith. Elevation CD I. E?»- Chicago(640 ft) , . «ZPgrthuroMQOS. ft) 4 '° ° Th'" :50 20 10 5 o I 1000 years BP I I on 4. o o o o Figure 2.19. Predicted elevation of outlets through time. Note that the Chicago, Port Huron, and North Bay outlets are all near the same elevation at 5000 yr B.P. in the minimum deformation model (thick lithosphere-thin ice sheet). 55 using a thin ice sheet predicts the Chicago outlet to be at nearly. the same elevation as Port Huron and. North. Bay outlets during the mid-Holocene (5000 yr BP). This is consistent with the recent empirical data. The model with the thick ice sheet, however, predicts too much deformation at the Chicago outlet to allow it as an outlet for Lake Nipissing. These data suggest a thinner ice sheet is more compatible with the empirical data of outlet Chronologies. 2.3.2 Modeled Lake Gauge Deleveling Data Analysis of lake Igauge deleveling' around 'the Great Lakes has been used to evaluate differential uplift trends within the region. These data are in conflict with the traditional model proposed by Goldthwait (1908) and Evenson (1973) for shoreline deformation within the southern Lake Michigan basin (see Section 2.1.2.2). The lake gauge data indicate significant differential tilting within the region south of the Algonquin hinge line (see Figure 2.6). Figures 2.20 and 2.21 compare two interpretations of lake gauge deleveling data with numerical predictions which indicate the range in predictions for the four models considered in this study. The lake level gauge data presented in Figure 2.20 is that of the Coordinating Committee of Basic Hydraulic Data (1977). The interpretation in Figure 2.21 is from the same data; however, the Ludington, Michigan station is added. The Ludington station has been gauged regularly only since 1951 56 Lake Level Gauge Data x. 2.03 . \m _ ‘ \ 1 -0A“.‘.'V “"!a>> ‘lth;;\‘--.~—- “V‘. / mm/yr L - -1.04 ‘ , (relative to Goderich, Ontario) Predicted Present Uplift Relative to Goderich, Ontario ‘ Ail \ (mm/year) ‘* Earth: Thin Lithosphere Ice: Thick Fi 2.20. Comparison of predicted present differential movement us mg the maximum deformation model (i.e. thin lithosphere - thick ice sheet) to lake gauge data for the upper Great Lakes relative to Goderich, Ontario. 57 Lake Level Gauge Data \ 7 mm/yr (relativeto Goderich, Ontario) Predicted Present Uplift Relative to Goderich, Ontario #:— mm ear 6 NY ) . J’ I [-6 \ I’ .6 \ so 0 \ ‘5 ‘0 Earth: Thick Lithosphere Ice: Thin Fi 2.21. Comparison of predicted present differential movement us ng the minimum deformation model (i.e. thick lithoshpere - thin ice sheet) to lake gauge data for the upper Great Lakes relative to Goderich, Ontario. The interpretation of the lake gauge data has been altered to include the station at Ludington, Michigan. 58 and is therefore not as reliable of an indicator of isostatic rebound as the other stations which have been gauged regularly for at least 80 years. Analysis of the interpretations and predictions indicate that the maximum uplift model (i.e., a thick ice- sheet with a thin lithosphere) predicts too much uplift across. the Huron and Michigan basins, but adequately represents the tilting observed in the Superior basin. The minimum uplift model, on the other hand, predicts too little differential uplift. It is significant that the numerical models do predict uplift magnitudes and trends more similar to the observed data than the traditional model which maintains stability in the south and nearby east-west trending isobases in the north (see Figure 2.22). 2.3.3 Modeled Algonquin Shoreline Data The Algonquin shoreline is very likely the most mapped ancient shoreline within the Upper Great Lakes. Although Spencer’ (1891) was the first to name and. recognize 'the .Algonquin shoreline, the most thorough. mapping' was accomplished by Goldthwait (1908, 1910). Figure 2.22 demonstrates the deformation of the Algonquin water plane based on Goldthwait's work. The numerical models were used to determine the predicted deformation of this water plane. The Kirkfield outlet was chosen as the controlling outlet at 10,500 years 59 .moma. unuaaueaoo an oaaaouoau agaveomae or» no uoaoaoau .Aoama .-.« unseen 98: 60 BP for the prediction. Figure 2.23 illustrates the results of two different model predictions. The data indicate that the maximum uplift model (thick ice and thin lithosphere) predicts too much deformation, while the minimum uplift model (thin ice and thick lithosphere) predicts slightly less uplift than observed. This is consistent with the lake gauge deleveling data and outlet Chronologies. Figure 2.24 illustrates the predicted values relative to the observed data in a shoreline profile for the northern Lake Michigan basin. The model results predict the Algonquin shoreline to be submerged south of the Algonquin hinge line. Comparison of Figures 2.22 and 2.23 indicate that the Algonquin hinge line, as interpreted by Goldthwait, is the point of submergence beneath the present lake level in the numerical modeling. The numerical model results are consistent with Spencer's (1891) original work and that of recent researchers (Larsen, 1987, Kaszycki, 1985, and Karrow, 1985). 2.3.4 Summary of Modeling In summary, the numerical model is consistent with the empirical data throughout the Lake Michigan basin. In the southern Lake Michigan basin the numerical model is consistent with recent shoreline interpretations (e.g. Larsen 1987) with the exception of the Lake Chicago shorelines south of the Algonquin hinge line. The empirical Lake Algonquin Isobases(KIrkerld Ou\tlet 10. 500 years. BP) sw‘. I! {ll Earth: Thick Lithosphere IcezThin Earth: Thin. Lithosphere IcezThick Figure 2.23. Predicted isobases of the Algonquin shoreline (using the Kirkfield outlet at 10, 500 B.P.). The maximum and minimum models are compared. The dashed line is the isobase at the present level of Lake Michigan. The Algonquin shoreline is predicted to be submerged south of this isobase. 62 eaaaxzmwwm paragon. 3 8:583 3:83. «fiance: 3388a .6 contusion and can m h 68.3 cos—8 e755 2: .53 on: a 8a 3:333 82. 2:. .58.. 552a 83 Eunice 2: 5 8:83. 558»: e25 o aauc_oammaa com com c3 can on and 80.6" 903—5 Sega 30302 . 63 data can be explained with normal isostatic processes, without relying on glacio-isostatic hinge lines. The empirical data suggest a thin ice sheet within the Lake Michigan basin. Given the range in numerical predictions, due to different ice sheet thicknesses and earth rhelogies, the I numerical model is shown to be a valuable tool in evaluating the isostatic rebound within the Lake Michigan basin. Comparison of model predictions to the new shoreline data produced by this study is addressed in Section 3;3. CHAPTER 3 - EVALUATION OF SHORELINE DATA FROM SOUTHWESTERN MICHIGAN 3.1 Introduction Chapters 1 and 2 have introduced the historical background, and conflicting 'theories concerning isostatic rebound in the Lake Michigan basin area. Sections 2.1 and 2.3 of Chapter 2 have demonstrated the incompatibility between the traditional model of isostatic rebound, based on field data, and theoretical studies of isostasy. In this study, the existing shoreline data have been evaluated and higher shoreline data have been mapped. The purpose of this field investigation is to evaluate the possibility that the conflict between the traditional model and theoretical results is caused by a paucity of field data and incorrect shoreline interpretations in the southern Lake Michigan basin. Shoreline data around the southern shores of Lake Michigan have been collected by several earlier workers. Of these, Goldthwait (1907, 1908), Leverett and Taylor (1915), Alden (1918), and Evenson (1972) reported most of the data. These data. have been compiled. and. cataloged. by’ Evenson (1972) and are shown plotted in Figure 2.4. Lacustrine features at elevations higher than these were also observed and reported in the early work; however, they were interpreted to result from ponding of water in front of the ice sheets associated. with the Lake Border or earlier 64 65 advances, and therefore not related to a major glacial lake stage. Several surficial maps at both regional (Leverett and Taylor 1915, Flint 1959, Martin 1955, and Farrand and Bell 1982) and local scale (Gephart and Larson 1982, Terwilliger 1954, and Tague 1942) delineate the presence of higher lacustrine sediments within southwestern Michigan within the study area (see Figure 1.2). The size of the area to be studied ruled out the possibility of detailed field mapping throughout the entire area. Therefore, reconnaissance level mapping was performed over the entire study area using available reference material such as surficial maps, soil maps, and topographic maps. These data collected during the reconnaissance mapping are cataloged in Appendix C. More detailed work was then limited to specific sites within the study area. In order to ensure consistency with previous research in. classifying lacustrine and.:near-shore features. within southwest Michigan, this study used Evenson’s catalog of field sites as a guide. These sites are recorded in Evenson (1972 pp. 56-88) and are included in Appendix C. Prior to classifying any higher lacustrine features these sites were located on topographic maps and most were visited in the field. This provided the author experience in recognizing sites as well as criteria for identifying new lacustrine and near-shore features. It should be noted that it is beyond 66 the scope of this project to defend each type of feature described by Evenson and included in this study as evidence of near-shore conditions. Therefore, this study is restricted to the identification of features similar to those reported by Evenson which are found at elevations higher than the traditional Glenwood level. A few field sites, discussed in Section 3.2.4, were considered in greater detail. Several kinds of features and sediment types are mapped as near-shore or lacustrine indicators by Evenson. These include: 1) linear sand ridges; 2) gravel ridges; 3) topographic breaks from flat to hilly topography; 4) river terraces; 5) flat lying' silts and. clays; 6) flat lying bedded sands; 7) topographic scarps; 8) sand ' and gravel deposits; and 9) transition from sand or pebbly sand to till. Examples of each of these can be found in Evenson (1972). Evenson mapped these features not only in the study area. but also further north and in. Wisconsin. It is important to note that many of these features could be fluvial in origin. Additional data at selectedsites were collected to confirm the lacustrine origins of those specific sites (see Section 3.2.4). Since the completion of Evenson's work, which used 15 minute topographic maps, 7.5 minute topographic maps became available and were used in this study. This improvement provided greater detail and showed new areas of excavation. 67 Improvements in surficial maps were also helpful (e.g. Farrand 1982, Gephard. and. Larson 1982) in locating' the extent of lacustrine deposits. The importance of new topographic maps is significant in that both Evenson (1972) and this study rely heavily on topographic features. According to Evenson (1972 p. 19) the "Glenwood and Calumet shorelines are mapped on reconnaissance level between the Indiana [-Michigan] state line and the Whitehall, Michigan, area." He also states (p. 17) "the step like nature of the Glenwood data in the south end of the basin [(see figure 2.4)] is the result of the contour interval imposed by topographic maps used in the rapid reconnaissance of this area." This area between the state line and Whitehall is of primary interest to this study. Reevaluation of the shoreline features north of this area has been reported by Taylor (1985). Evenson (1972) produces data in nearly complete agreement ‘with ‘that. of' earlier 'workers (e.g. Goldthwait 1907, 1908, Leverett and Taylor 1915, Alden 1918). However, Everson believes the Glenwood shoreline is differentially uplifted. According to Evenson (1972 pp. 35-36) the Glenwood shoreline shows differential tilting north of a line connecting New Buffalo, Michigan, and Oostburg, Wisconsin. Differential uplift within this area contradicts interpretations of Goldthwait (1907, 1908) and Alden (1918) who believed the Glenwood shoreline remained horizontal at 68 195 m (640 feet). Evenson, however, mapping "with newer and more accurate topographic maps" was able to "demonstrate this conclusion to be in error" (Evenson 1972 p. 36). 3.2 Shoreline Data Within Southwestern Michigan The shoreline data within southwestern Michigan, collected by this study, is used to evaluate the validity of the traditional shoreline model proposed by Goldthwait and Evenson (see Section 2.1). The data are analyzed for evidence of differential isostatic rebound, or lack thereof, in the southern Lake Michigan basin. 3.2.1 The Method of Analysis These higher lacustrine features are analyzed at three scales of investigation. Frist, a regional examination of the data for continuity and overall uplift trends is considered. Interpretations of shoreline tilting on a regional scale are sensitive to isobase trends and particular attention will be given to isobases here. Second, the data are analyzed separately in two regions which could be local ponds or embayments. This information 'can be used to test for differential tilting regardless of the ponded or unponded nature of the deposits. Third, some specific sites are, analyzed in greater detail because of their importance to the interpretations. 69 3.2.2 Regional Analysis of the Field Data Shorelines associated with ancient lake plains in the Great Lakes area are highly sensitive to the choice of isobase trends. To correlate shoreline data isobase trends must be established. Evenson (1972) provides data from both sides of Lake Michigan along with isobases drawn from that data. These shorelines on each side of the basin remain undated with radiocarbon dates. Higher lacustrine features have long been recognized within the Lake Michigan basin indicating these Ishorelines cannot be correlated. by their similar stratigraphic position (i.e. both the highest shoreline) (Leverett and Taylor 1915, Martin 1955, Flint et al. 1959, Farrand and Bell 1982, Gephart and Larson 1982, Timmermans 1988). It is also clear that correlation based on their similar elevations in the southern portion of the study area requires the implicit assumption ‘that ‘the isobases were known and that they trend exactly east-west, or that there was no differential tilting. - Therefore, Evenson's isobases shown in Figure 3.1 cannot be accepted without further evidence to support them. Furthermore, these isobases converge toward the northwest (Evenson 1972 p. 16), an unlikely result if normal isostatic processes are operating. From Figure 3.1 we see that all three isobases would come together just west of the city of Green Bay indicating at least 6.1 m (20 feet) differential 70 Figuro 3.1. Evenson's isobases of the Glenwood shoreline (Evenson 1972, 1973). 71 movement at that location. This along with the flattening of the ancient water plane at 201 m (640 feet) strongly argues against the adoption of these isobases. This is not to say that Evenson's interpretation is incorrect, rather that it is extremely difficult to explain and that to adopt it ,as a starting point for analysis of newly mapped lacustrine features would be unwarranted. Evenson (1972 p. 36) points out that to explain the mode of isostatic rebound throughout this area (based on his interpretation of the field data) would require ”basement faulting or exotic models of ice distribution and retreat." Differing ice distributions and Chronologies might change the rates and overall magnitudes of differential tilting from area to area; however, no reasonable scenario would result in convergence of isobases (Hendriks et al. 1988). This leaves basement faulting which cannot be tested at this time due to the paucity of' evidence recording' basement faulting during the late Quaternary in this region. Basement faulting is unlikely given the striking lack of seismicity throughout the southern peninsula. This. option is not considered any further in this study. Changes in isobase trends can greatly influence interpretation of shoreline data. As pointed out earlier in Section 2.1.1 the idea of a hinge line and stability in the southern Lake Michigan basin is the result of Goldthwait's interpretation? of isobases (Goldthwait 1908). The 72 importance of isobase trends in his interpretation cannot be overstated. Evenson's data further illustrate 'the importance of understanding the isobase trends. Considering his data only from Michigan (to avoid making the correlation across Lake Michigan), altering 'the isobase trends provides an explanation of the lack of differential uplift without requiring an exotic isostasy model. The shape of the curve is _unchanged by subtracting out the Wisconsin data. Allowing a change in isobases rather than basement faulting the'curve itself gives a clue to a possible solution. If the isobases trend.:northwest-southeast, the shoreline is tilted where it runs at an angle with the isobases and is horizontal where it runs parallel to the isobases. Therefore, if Evenson's isobases are at a slightly greater north-south orientation than shown in Figure 3.1, his shoreline curve is easily explained. It is important to note that this is not included as an attempt to discredit Evenson’s interpretation or to reconcile his field data to a more simplistic uplift. model, it is simply exemplifying again the importance of isobase trends in the interpretation of shoreline data in the southern Lake Michigan basin. The data pertaining to the higher lacustrine features, included in this section, will be presented with various isobase trends differing from Evenson’s. There is no attempt to physically correlate these features across the 73 lake or even outside of the study area. To do so would require the assumption that isobase trends are known. Only when these and other data can be more accurately dated will positive correlations exist around the lake. The data will be iconsidered with east-west trending isobases and northwest-southeast isobases, with an orientation of N25W. These two trends were chosen to represent the end members of the ranged in trends encountered in this study 'within the - numerical modeling and empirical data (e.g., lake gauge data). Figures 3.2 and 3.3 show the distribution of the shoreline features (Appendix C) found in southwestern Michigan along a north-south transect. Figure 3.2 is constructed assuming east-west trending isobases. If we consider just the highest data, the curve mimics Evenson’s curve, but is displaced higher. The average differential tilting along the transect is about 0.15 meters per kilometer. Figure 3.3 is constructed assuming northwest- southeast trending isobases with an orientation of N25W. In this projection the curve no longer flattens out in the center' like the previous curve. The average differential tilting along the north-south transect is slightly reduced to 0.12 meters per kilometer. This equals 0.28 meters per kilometer differential tilting perpendicular to the N25W isobases. 74 (13) annual: .6805 03303 €27.33 5. ~53 non-no.3 fine-I550: a uno? v3.33 couscous gangland no 039..— .N.» 0.52..— A35 5.32 03—359 8m .00.— 2: on O . _ _ _ _ . _ can 4 8.— + + + + I I +I++++¥ + + + + $1.. + + .I. I 9+ ##I 6+ Rf." H a. I Icon 650 l1 .7 I I I I I I I I II I I I II I. .e. ._ I a o cub .l I I I I I II I .II 62...! 4 M I don—32663 O o I. dog + m 2:1 I I 8.8888: I .4 m lava _ (In) normal: 75 (w) sonnets .485 833 5% a 483 .8455 assigned a 9.31 60.303 3.43:“ 93.31.30: .0 088m d.» 098E A85 fizz 8.3.5 can can so" a . _ _ _ _ _ _ So 4 4 + ++ + I can] I +I. . I t +2.:- +++T +L + ++ .4 +++.+ + + + .2. II + O A? + + a I 981 I I I I I I II II II I I l I II- II 0 24.1 I I u... I .- . I coal I “388363 . guru + 303.59 I on." Team (as) dogma 76 . Higher lacustrine features than those shown in Figures 3.2 and 3.3 were observed sporadically in the field. However, elevations higher than those recorded here were not considered in detail and therefore are not included as part of this study. The possibility that these higher features are part of a continuous lake stage cannot be ruled out, however, the analysis is beyond the scope of this study. This study focused on widespread lacustrine plains in order to improve correlations between data points within the study area. In is unclear if high features in the nOrthern part of the transect (plotted between 238 m and 240 m) are correlated with the lower lacustrine plain. It is possible they do not belong on the same surface. Three field sites shown in Figures 3.2 and 3.3 have been dated by radiocarbon techniques. These are shown as a separate symbol on the transects. These sites are described in greater detail in section 3.2.4 and are presented here only as they relate to regional analysis. Two of these sites are near the upper limit of the data. The third is at 201 m (660 feet) and is part of Evenson’s curve (Evenson 1972). This site was recorded by Evenson as part of the Glenwood lake stage. Wood from peat below the sands and gravels at this site was dated at 6120 +/- 100 years B.P.. Evenson described this site as part of the Allendale delta. However, the recent date suggests that the fluvial sands and gravels observed. by' Evenson are part of' a more (recent aggradation of the stream which formed the exposure. 77 The two sites near the top of the plotted data are from nearly opposite ends of the transect. These sites are also of similar age. The southern site (#31 in Appendix C) is found at an elevation of 212 m (695 feet) and the date on wood from a soil deposit underlying the sands is 11,650 +/- 130 years B.P. The northernmost site (#86 in Appendix C) is found at an elevation near 220 m (720 feet) and the date on wood from peat there is 11,440 +/- 170 years B.P.. Both of these features, if lacustrine, represent minimum elevations and maximum dates for a transgression. The northern site is slightly lower in elevation than the sites immediately adjacent to it. Assuming the sites are lacustrine, this along ‘with the younger date could suggest that the northern area was flooded earlier during the transgression than the southern site, and therefore is not as close to the maximum elevation of the transgression. However, the counting error about these dates allows overlap and the age difference is only speculative. It should also be :noted 'that the northern, site is a sand. ridge in a lacustrine plain and could have had aeolian influence not related to a lake transgression. These possibilities are discussed more thoroughly in section 3.2.4. 3.2.3 Analysis of Local Embayments (ponds) The spatial distribution of the data within the study area suggests that the sites can be easily divided into two groups. Analysis of surficial maps (e.g. Martin 1957, 78 Farrand 1982) shows that there are two broad areas covered by lacustrine sediments within the study area. 'Figure 3.4 shows the location of these areas. The southern area is found mainly within Allegan County and will be referred to as the Allegan embayment within this report. Detailed mapping of this area was done by Gephart and Larson (1982) and shows the extent of the lacustrine deposits within this county. The northern area is a lacustrine and outwash plain found mainly in Muskegon and Ottawa Counties and will be ‘ referred to as the Ottawa-Muskegon embayment. The sites within an individual embayment are-easily correlated and at times can be mapped as continuous for several kilometers. Therefore, these data can be used to test for differential tilting even if they are from water ponded in front of the ice sheet. If these sediments are from ponded water the differential tilting observed could be from a time prior to the Glenwood stage. 3.2.3.1 The Allegan Embayment This embayment is characterized by an extensive flat lacustrine plain. All researchers who have mapped this area have considered these deposits lacustrine in origin (e.g. Leverett and Taylor 1915, Evenson 1972, Farrand 1982, Gephart and Larson 1982). The plain is predominantly sand and has been partly reworked by wind. The lacustrine unit is located east of the Lake Border moraine, and ranges in . 4, - v , . . I‘ V. ‘ I 4 K 1 a . 8m? :. 3.. ... . . { \u um Muskegon/Ottawa 3“ 3"" . ‘ 4‘ F- _Lacustrines - x W . mm - 1 ex. _ . Nngéfif ‘ \\=a§z- W‘ma' —' \m4 C ' ‘ 5‘ '36 cu . 1 c) 2’ '1‘ ' . 1 . i ‘Cfl '9 wan-am '3 .b . -' ,1 4‘ s 1 K E “fixer". 7.." I _l f? ‘3' , »‘- '~ ’ . - LII-Shove"? ’ _ .. ‘ Allegan Lacustrines , .1)“ - WWI-92244:». 31’. Figure 3.4. Location of the lacustrine plains investigated in this study shown here on a surficial map of Michigan by Farrand and Bell (1982). 80 elevation from approximately 195 m (640 feet) to 213 m (700 feet). Figure 3.5 is a northrsouth trending transect showing the distribution of field sites with respect to elevation. The data are plotted assuming east-west trending isobases. As in the regional plot with east-west trending isobases, the x axis is kilometers north of the Michigan-Indiana border. The area is not large and caution should be taken when evaluating tilt trends. If it is assumed the upper points are from a particular transgression; differential uplift of 0.14 meters per kilometer is observed. At site #33 there is a topographic break which ranges in elevation from 207 m (680 feet) to 213 m (700 feet). Out in front of the topographic break there is a sand ridge which is typically at 210 m (690 feet) and appears to be, at least partially, a wind-blown feature. Therefore, the site is plotted at the average elevation of the topographic break. The amount of differential tilting (0.14 m/km) is consistent with the southern part of the regional plots. These same data were plotted assuming isobases which trended northwest- southeast (25 degrees from north-south) and they also closely matched the uplift observed in the regional plot with similar isobase trends. 3.2.3.2 The Ottawa-Muskegon County Embayment Most of' Ottawa. and. Muskegon counties and. parts of Newaygo and Oceana counties are covered by a blanket of flat 81 (In) uonmm 885 82.8. 82788 8. .83 5498 8 4383 8:253 A: 88 8 8m 25%. use 366 2593—1 anon—Rana .5550 Inca 6.0 0.53.- 33 5.82 883.3 as" as" co on as so . _ _ _ _ _ , _ Sn .4 4 c8 0 o I 2... can I a...“ .2.» wk“? 8:45» 8 2:48: I So 3.4:an“ 630233.433 an 4 38 J. m o8 I I 8.. m m I 2:. 3a I I2... 82 lying sands. These features have been recognized as lacustrine up to and beyond the traditional Glenwood elevation of 201 m (660 feet) (Farrand and Bell 1982, Martin 1955). In many places there are wind-blown features breaking up the otherwise flat plain. No consistent change in soil type is reported at the traditional limit of the Glenwood transgression (USDA Soil Conservation Service 1968, 1972).. At approximately 210 m (690 feet) the plain is kettled in Muskegon County. However, the sediment and soil types leading up to the kettles appear unchanged. Two kettles holes were cored, and sands of similar grain size and texture were found within the kettles beneath the peats. Analysis of the pollen at the base of these kettles is being conducted (Clark per. comm.). Figure 3.6 shows the distribution of near-shore data with elevation as a function of distance to the north. The data are projected. onto the 'transect assuming' east-west trending isobases. This curve is simply the northern half of the regional plot shown in Figure 3.2. Likewise a plot assuming isobases trending northwest-southeast would be the same as the northern half of Figure 3.3. The importance of the assumed isobase trends can be further demonstrated by considering a point directly to the west of this curve in Wisconsin. For example, if this curve were projected to the correlative shoreline in Wisconsin assuming' east—west isobases the expected. shoreline ‘would 83 (In) uonmm .3392; Eng glance IS!— «0033.! fiscalfiuod a ado? 38 588938. 3383 4838\84333 2: 8 cacti .3 can sac 4.52 885: . 8w o3 o_3 o1 o3. gal I. _ I...) + “I ONO . 4 I I + I + + + +4 1.. 14+ ++uf II 9 [one + II I OHNII I I I I h I Ilse. I I I I I f I , I I I I . [Sb 0&1 n m Incas. I III :8an + m 3.33... .. . w (1:) WWW 84 obviously be at the same elevation. However, Figure 3.7 shows that if the isobases really trend northwest-southeast as shown in Figure 3.3, the shoreline directly to the west in Wisconsin, correlating to the 220 m (720 feet) section of this curve would be found at an elevation of 198 m (650 feet). Likewise, a shoreline found at the traditional Glenwood level in the southwestern corner of Michigan would correlate to a shoreline found at the same elevation near Two Rivers, Wisconsin. 3.2.4 Evaluation of Selected Lacustrine Features There are several sites considered in this study which are of special interest to the analysis of high lacustrine features. These include sites which have been dated by radiocarbon techniques and sites which are particularly strong evidence for major transgressions. These sites are analyzed individually with regards to their sedimentology and other field evidences used to substantiate the interpretations. The methods described in Section 3.2.1 on the criteria for recording a site as evidence of a transgression are not very rigid. They were chosen to facilitate field work over the large study area and to be consistent with earlier workers (e.g. Evenson 1972). Therefore, sites where the evidence is very strong or radiocarbon dated, receive special attention. 85 Approx. E-W 220 m Isobase 4’ “‘o ‘32. 0' ¢ ‘32. Approx. E-W 198 m Isobase \2\ Figure 3.7. Comparison of shoreline correlation across Lake Michigan using NZSW and east-west trending isobases. With the N25W isobases a shoreline in Michigan at 220 I correlates with a shoreline at 198 I directly to the east in Wisconsin. 86 This section will summarize five locations within the study area. Three of these sites are included because they were dated by radiocarbon techniques. Two of the dated sites are high lacustrine features. Two other sites are included as lacustrine features with distinct sedimentological features and/or unique stratigraphic positions. Each site is given a name for convenience of discussion and is recorded in Appendix C. They are described here in order from south to north as in the appendix. Figure 3.8 shows the location and identification of each of these sites. 3.2.4.1 The Hagar Site ~ The Hagar site is located in Section 15 of' Hagar Township of Berrien County in an area mapped as glacial till by Farrand & Bell (1982) (#31 in Appendix C). The topography of the site is flat at an elevation of 211 m (695 feet). It consists of horizontally bedded, flat lying sands and silts over a gray glacial till with an organic rich soil and peat layer developed on top of the till. The soil and the peat are generally thin (less than 10 cm) but contain abundant amounts of wood. More than 10 cores were taken with a bucket auger over an area greater than 1500 square meters and in each core a similar stratigraphy was observed. Figure 3.9 is a description of the typical core. The sediment above the organics fines upward with medium to coarse sand at the base grading to very fine sand and silts 87 4. Claybanks Section 5. White River I Delta I 3. Slocum Ridge I 2. Bass Creek 1 . Hagar Site Figure 3.8. Map showing the distribution of selected sites. 88 Depth Uthology ("1) (ft) 00— 0.0 __ ____... . ' ' '7 Fine to Very Fine -__.'_."_:_ Sands with Medium _' - 0 '_ Sand, Silts 8 Clays 1.0 - '. " ' 7'7“? e 0 p . .I :e '. 2.0 _ : ..:‘. e .O '. . o .' — O 3'0 . t.. 0 Medium Sand with 10 —— 3 3.. Coarse and Very . 0 Coarse Sand, Silts . 0 and Clays { . . ‘ Soil on Gray Tull with Wood and \ / //’/- Cones, Age ofWood is 11,650 +I-130 B.P. Figure 3.9. Cross-section of the Hagar site interpreted to he a transgression. . _ = 89 at the surface. Samples from five depths were collected for further analysis. A wood sample taken from a depth of 1.37 m (4.5 feet) was dated with radiocarbon techniques by Beta Analytic Inc. and found to be 11,650 +/— 130 years B.P. (Beta Analytic # 22292). At 1.22 m (4.0 feet) depth the sediments were found to be medium sand with coarse sand, fine and very fine sand, silt, and clay. There was more silt and clay at this depth than in the sediments above this level, even though the median grain size is larger. The median grain size was measured to be 1.75 0 (0.30 mm). At 1.07 m (3.5 feet) depth the sediment is very similar to the sand at 1.22 m. At this level the median grain size is coarser than below (1.68 0, 0.31 mm). However, the small increase in median grain size is induced by the presence of a minor amount of very coarse sand. Fine and very fine sands, silts, and clays were also present. The samples collected at these depths are considerably less sorted than the finer grained sediments above these. The median grain size of 1.68 to 1.75 O is larger than reported median grain sizes for dunes in the southern Lake Michigan basin (i.e., 1.92 ¢ to 2.16 0) and is consistent with beach data from that same area (Gutschick and Gonsiewski 1976). Samples were also collected at 0.46 m (1.5 feet) and 0.76 m (2.5 feet) depth. The median grain size in the upper sample was found to be 2.35 8 while the lower sample was 90 2.30 ¢. Each sample was characterized by fine to very fine sand with medium sand and some silts and clays. The sample at 0.76 m had less silt and clay than the upper sample suggesting that much of the minor amounts of clay were formed by weathering processes. The grain size within the upper part of this section, demonstrated by these two samples, is considerable smaller than those found by Gutschick and Gonsiewski (1976) in dunes in southwestern Michigan. Seams of sediment with different grain sizes were observed as well as minor heavy mineral lag deposits within the section. Comparison of median grain sizes for selected sites and Gutschick and Gonsiewski is given in Table 3.1. In summary, the Hagar site is characterized by horizontally' bedded. sands and. silts in an .area of flat topography. Cores over a linear distance of 100 m and an area of 1500 m2 were shown to have similar stratigraphy. The characteristic bedding consists of fine to very fine sand. over medium sand" An aeolian origin is unlikely because the upper section is finer grained than other dunes observed in southwest Michigan while the lower section is coarser grained than those same dunes. The flat topography is also inconsistent with aeolian deposits. The maximum date of 11,650 +/- 130 B.P. along with the position of the deposit on the moraine rules out glacial outwash and recent stream deposits. The origin is, therefore, not believed to be fluvial. Apart from the bedding there were no sedimentary structures observed within the pits that were TABLE 3.1 COMPARISON 01' mm GRAIN SIZES Mm Gun 81:: W _WI 8 Hagar Site - 0.46 m (1.5 feet) depth 2.35 Hagar Site - 0.76 m (2.5 feet) depth 2.41 Hagar Site - 1.07 m (3.5 feet) depth 1.68 Hagar Site - 1.22 m (4.0 feet) depth 1.75 Slocum Sand Ridge Site 1.90 Gutschick and Gonsiewski (1976) Beach Strand 1.34 Beach 1.70' Dune* 2.04 Slipface of Dune* ' 2.00 * These are averages of the values determined by Gutschick and Gonsiewski (1976). In their report, the dune sand ranged from 1.92 to 2.16 and the slipface 1.96 to 2.03. 91 92 dug. The most viable interpretation at this time is that the deposit is lacustrine sands made by a transgression of unknown extent. 3.2.4.2 The Bass Creek Site The second site (see Figure 3.7) is theiBass Creek site. This site is located just south of the Allendale delta in the town of Bauer. At the intersection of Bass Creek and 48th Avenue there is an exposure in the bank of the creek. This site was located while visiting the sites listed by Evenson (1972). Evenson (1972 p. 65 #10) recorded this site as "2 feet highly weathered sand with gravel over gray till. Sand is part of the Allendale delta." During the interim between Evenson's field work and this study the stream had cut further into the bank exposing a larger section. It was observed to have sand, gravel, and silt over lying gray till. At the contact there was a layer of peat and wood, with logs as large as 15 cm (6 inches) in diameter. This sequence could be observed for length of about 50 m in the stream bank just west of 48th Avenue. The wood was dated by Beta Analytic Inc. and found to be 6120 +/- 100 years B.P. (Beta #18471). The elevation of this site is the traditional Glenwood level (201 m (660 feet); however, the young date suggests a fluvial origin. There were no conclusive sedimentary features observed within the section. ‘The sands and gravels were not crossbedded and only a few ripples could be found 93 in the silts and fine sands. The likelihood that these sediments are part of the Allendale delta, even though they appear at the same elevation, is small. Aggradation of a creek, incised earlier into the delta, is more likely. The cause of the aggradation could be the Nipissing transgression, however, the deposit is located near the head of this small stream approximately 15-20 km from the traditional Nipissing limit. 3.2.4.3 The Slocum Ridge The third site is the Slocum sand ridge. The Slocum ridge is one of several sandy ridges sitting in front of a sharp topographic break. Figure 3.10 is a copy of the Bridgeton 7.5 minute topographic :map showing the area around the sand ridge. Most of the ridges in the area, including ‘the Slocum. ridge, appear to be dunes on the topographic map. The Slocum ridge was cored and found to overlie a peat deposit. The peat reaches a thickness of 15 cm (6 in) in some places and has abundant wood. The wood was dated using radiocarbon techniques by Beta Analytic Inc. and found to be 11,440 +/- 170 years old (Beta Analytic #19998). A sample of sand from the ridge just above the peat was found to have a median grain size of 1.90 ¢ (0.27 mm). This is coarser than the dune deposits and less coarse than the beach deposits analyzed by Gutschick and Gonsiewski (1976) (see Table 3.1). Cores taken in the ridge revealed the 2,60- We 4.3 J . O \‘J 3 Figure 3.10. Topographic map of the Slocum sand ridge arcs. Bridgeton Quadrangle. lichigan. 7. 5 minute series (topographic). provisional edition 1985. 95 preSence of some stringers of coarse sand. and clay at approximately 1.5 m (5 feet) below the crest of the ridge. There was as small percentage of very coarse sand (-1 to 0 0) found during the sieve analysis which was not present in the dunes observed by Gutschick and Gonsiewski. The very coarse sand grains were, in general, angular to rounded with medium sphericity. The coarse sand grains (0 to 1 0) found were in general medium roundness and sphericity. Neither the medium, coarse, nor very coarse sand was observed to be frosted. Because of the paucity of sedimentary features at the Slocum. Ridge, a. definitive interpretation. of its origin cannot be given. Possible interpretations of this landform would include inland dune, off-shore bar, or fore dune and beach deposit. The idea that these are inland dune deposits could rule out the necessity for a high lake stage in this area after the deposition of the peat 11,440 years BP. The interpretation of near-shore deposits would require the Calumet stage of Lake Chicago to be nearly 30 m (100 feet) higher in this area than previously thought. The features along this topographic break, including the Slocum ridge, are relatively large topographic features with relief up to three or more meters. The strongest evidence in favor of the near-shore environment interpretation is its setting. Figure 3.11 is a schematic profile of the features observed in the slocum sand ridge 96 $3.50- ofimsuuomoa use 038 v3 8:005 05 no each.— oflsfieflom A I.» 0.535 8a a can aerate; 13:8» 3» II can A§o8c 88m /\i one dancer—om . » AGE 48.» 2:. can goo—m at. 3» 2.88 .86 “alga...“ 83.8 8 to. 8 spaces—H fin 33m dog-83 _ «2: can a 485m .3 Assure—83 as vex—Asa .-' Alliance: :8 a 455.4 E _ 8318438388 _ 97 area. The ridge is located on a extensive sand plain just west of a sharp topographic break. The plain is reported to be lacustrine by Martin (1955), Flint (1959), and Farrand and Bell (1982). Immediately above the topographic break there are clean sands and gravels with obvious (dunes above the clean sands and gravels. It is difficult to evaluate the possibility that the ridge itself is a beach deposit. The paucity of sedimentary features and the general setting would make that interpretation, even if correct, difficult to support, even though sandy berms are commonly observed forming at the Lake Michigan shoreline today. Other scenarios such as a dune-capped beach berm have not been thoroughly evaluated because of the paucity of sedimentary features. In summary, the surface morphology of the slocum sand ridge appears to have been produced or altered by aeolian processes. Core samples from the ridge indicates coarse sand and clay are present at approximately 1.5 m (5 feet) below the crest of the ridge. The setting suggests a potential near-shore setting. The feature could represent a near-shore bar or beach deposit with a wind-blown cap or other aeolian alterations, or less likely, an inland dune. 3.2.4.4 The Claybanks Section The Claybanks section is exposed along the Lake Michigan shoreline in Claybanks Township, Oceana County. The features exposed at this site are not dated; however, 97a the site is considered in some detail because of the quality of exposure and possible significance of the stratigraphy. Erosion along the Lake Michigan shoreline has exposed an extensive bluff in this area. The exact location of the site is given in Appendix C site number 102. At the Claybanks section nearly 50 m (165 feet) of vertical stratigraphy can be observed. An idealized section of the location is shown in Figure 3.12. In general the site consists of two tills separated by a thick fining upward sequence. Above these units are flatly bedded sands and cross bedded sands. Starting at present lake level the basal unit is observed. to be an over- consolidated red till. The till is extremely stiff with abundant silt, sand, cobbles, and boulders. The upper boundary of this unit is flat and in most places a boulder and cobble lag is present suggesting a hiatus between this unit and the next. The fining upward sequence above the red till is approximately 15 m (50 feet) thick. The sequence above the lag deposits on the red till consists of horizontally bedded sands at the base grading to finely laminated gray silts and clays. Above the fining upward sequence there is a gray till. The transition between the two is not sharp and in places the laminated silts and clays grade into~the gray glacial till. Along with the color difference this till is also much less compacted and more clay rich than the lower till. 98 Claybanks Section Interpretation 225m Description . .\\¥ I..- i;- (738“) pk :KK- Cross Bedded Dune _ / Sands l “t '- 4/2/ kn ./-'_' 215m .:4__1.;;a (8888 . .- - ' " ' - Horizontally mm” _'__._._.' '- Bedded Sands 1.._s..a_:_a I I a 205m . / / / I / (6728) Gray Clay with Glacual \ ’ / \ \ Pebbles to Ti" \ / \/ \ Boulders \ \ \ \ \ 197m (646“) . Finlng Upward j Seq. Cobbles Lacustrine n': '. :..I " t0 Laminated TranS' a. . I :'. |=s: Clays, gression . , t1. ' . .- Overcompacted E3“ 01:: 182m \ / \ / 4 (597“) Red Silty Clay Glacial \ \ \ \ \ Overcompacted nu / / ’ ’ / with Pebbles 2’ / \2 177m andBoulders Figure 3.12. Cross-section of the Claybanks site. 99 The top of the gray till is measured to be at an elevation of approximately 205 m (670 feet). Overlying this till is about 10 m (33 feet) of horizontally bedded sands. These are interpreted to be lacustrine in origin. Above the flat lying sand there is a variable amount of crossbedded sands which are interpreted to be dune deposits. The presence of a flat surface and boulder lag at the top of the red till suggests that when the ice retreated from this area, after depositing the red till, the lake level in the Lake Michigan basin dropped to at least the elevation of the top of the red till (182 m 600 feet). This suggests a substantial retreat from the area, possibly north of the Straits of Mackinac or at least the Indian River lowland. As the ice readvanced the level in the basin rose depositing the thick fining upward sequence. Lacustrine deposition continued until the ice reached this location and deposited the gray till. The flat lying sands above this till are interpreted as lacustrine. This deposit could have been deposited during the ice front retreat from the Clay Banks section or indicate another advance into the basin which stopped short of the Claybanks site.‘ The lacustrine sands are observed well above the traditional Glenwood level. 3.2.4.5 The White River Delta The White River delta is the most northerly site considered in detail by this study. The site is on the 100 flank of the Port Huron Moraine in' Oceana County, just southwest of the town of Hesperia. Figure 3.13 shows the location of this feature with respect to the surrounding topography. The White River dissects the southern edge of the flat topped, delta shaped feature. The flat surface of the site contains many shallow gravel pits dominated by sands and gravels. All of the pits were overgrown with vegetation at the time of this study and no bedding features could be observed. The surface elevation of this feature is 225'm (740 feet). The location of an exposure along the White River in the southern part of the site is given in Appendix C, site number 108. At this location nearly 6 m (20 feet) of sediments are clearly exposed. A ridge of stiff reddish till causes a riffle in the stream at the site. Directly above the red till is approximately 5 m (16 feet) of gray laminated clays. The clays are very clean, with only minor amounts of silt, and no drop stones were observed in this section. The clays were not highly compacted. Above the laminated clays there is approximately 1 m (3 feet) of sand and gravel. The sand and gravel at this location fine upward. Because of the paucity of sedimentary features, the possibility that the sands and gravels are fluvial in origin cannot be eliminated. Farrand and Bell (1982) mapped this area as glacio-fluvial. However, the spatial location, topography, and laminated clays (interpreted to be bottom 101 Figure 3.13. Topographic map of the Ihite River delta area. Hesperia Quadrangle. Michigan 7.5 minute series (topographic) provisional edition 1985. 102 set beds) has led to the interpretation of this site as a delta. 3.3. Comparison to the Models Throughout Chapters 1 and 2 two models of isostatic deformation in the Lake Michigan basin have been developed. The traditional model, based on the work of Goldthwait (1908, 1910) and Evenson (1972, 1973), maintains the southern Lake Michigan basin has not undergone differential tilting during the past 12,000 years. The other model, based on Spencer (1891), the numerical modeling, and other researchers (e.g., Black, 1974, Clark and Persoage, 1970, Clark et al. 1985, Larsen, 1985b, and Kaszecki, 1985) maintains the southern Lake Michigan basin should. have undergone differential tilting. The shoreline data produced within this study are compared to these conflicting models. Assuming the lacustrine features mapped in this investigation are the result of a single high lake stage within the southern Lake Michigan basin, an interpretation of a maximum limit of transgression can be drawn. Figures 3.14 and 3.15 illustrate a range in interpretations of a possible transgression into southwestern Michigan based on these data. In Figure 3.14 the data are plotted assuming an east-west isobase trend (N90W). In Figure 3.15 the data are plotted assuming an isobase trend of N45W. These isobase trends were chosen to reflect the range in trends observed in the numerical modeling. dog-no.3 o no "33339435 01:33 a 36085 054 680.3 coupon. unable-ac do 95-: 500 assigned a Inc? 60.33.“ monsoon coca—loses no camera .3 d A85 5.32 88.83 103 (1;) cannon 8N and 8.— OD . O . b can I? _ _ _ 4. 3" o + + + + + 81 I I+ I I +I++7++++ + + flu + +1.. 1". + + .I. I + II 98 + 4+ #II dd 33.0 I" 4. I 84 I. + I II I . I can. I .%m 804“ ION“ 62.1 m .3305 + m our] II g I 4 W lava . m (W) 1!me 104 (w) UORBABIB «anamoa n mmuuo«ucfl ocqq taupe: m ucoaa nouuon nu 32v 532 8535 ovw 8N o2 our on ow o 1 . nu . . d .L. . . d J .T 2.: .. +. m + - I . . . I + .1. +1... :1 +n_m+om_.o .fi +.:+.. + + +¢+Irl com .._. ++ + + oPN ONN 89828: o .8285 + acmEmEEc. _- .cowumouwm:uuu I no newunumumuoucw .ocuuu mannoua 3m¢z I mafia: nommcmuu canon Manama ouozmluom: no manuoum .ma.n «known omo (u) uonenela 105 In the four numerical models used in this investigation, the isobase trends, for a calumet-age water plane in southwestern Michigan, ranges from N52W to N62W. The two numerical models with the thick ice sheet produced isobase trends of NSZW and N57W. The numerical models with the thin ice sheet produced isobase trends with a larger east-west component (N62W and N65W). The interpretations of the transgression are compared to the results of the numerical modeling in Figure 3.16. The model predictions using a thick ice sheet modeled after Denton and Hughes (1981), is shown by the upper shaded region representing predictions with a lithosphere thickness ranging from 112 to 212 km. The lower shaded region illustrates the model predictions using the same range in lithosphere thicknesses with a thin ice sheet modeled after Boulten et a1. (1985). The model predictions were calculated by considering a lake plane controlled by the Chicago outlet at an elevation of 189 m (620 feet) 11,500 years B.P. (the age of the two dated sites produced by this investigation). The numerical calculations using the thick ice sheet models predicts too much differential tilting in the northern portion of the curve. The model calculations using the thin ice sheet models predicts approximately the same amount of differential tilting, except that the predicted curve is shifted downward by approximately 10 m (30 feet). This 106 (In) comma Joan—no.5 fiuglfluou a ado? Ion—5G3 choir—con 605.50 05 3 3336.323 13.353. «0 dogma—o0 .3 .n 9:53 gas 582 8.3.5 . cow 8w can 00." on O 2: ._< _ _ _ _ ‘ ”II can \\ 00% a? M II“ 200% \I one coal 211-‘— =. my \ \)'\\ an? a .\ 2%.... I‘IN‘M IL 3m \ \‘I..oo¢ I cop 1“ .3... "a. cum L :33. $39? | x i ’35 | 83%: as... n can I ago‘fib " .9 39.9.0.» '9 p x A...» 3m 1 \\ \\o. (13) normal: 107 shift could be caused by an invalid assumption in outlet elevation within the numerical prediction. The higher shoreline data collected in this study are observed to be differentially tilted throughout the southern Lake Michigan basin. Therefore, these data are not consistent with the traditional uplift model of isostacy in the southern Lake Michigan basin proposed by Goldthwait and Evenson. These data suggest differential tilting south of the Algonquin Hinge line. CHAPTER 4 - CONCLUSIONS Understanding the response of the earth’s surface, evidenced by the tilting of ancient lake shorelines, to isostatic processes in the southern Lake Michigan basin is in itself significant, however, the problem attains a higher level ‘of significance among glacial geologist in that several glacial and post-glacial deposits and events in the Great Lakes region are correlated. by the use of' these strandlines. Interpretations of features such as river terraces graded to these ancient lake levels (Eschman and Farrand 1970), tills correlated from Wisconsin to Michigan based on beach cross cutting relationships (Evenson 1972, 1973), and time correlation between shorelines in Michigan, Wisconsin, and around the Lake Huron basin (Goldthwait 1908, Bretz 1964, Hough 1966) all depend on the mode of glacial isostatic deformation occurring in the Lake Michigan basin. These problems are not included in this study; however, they demonstrate that if the evidence calls for re- interpretation of the shoreline data, significant revisions in southern Michigan glacial history could be needed. On the other hand, support of the traditional shoreline interpretation (i.e. stability south of the Algonquin hinge line) could lead to major revisions in our understanding of the structure of the earth in this cratonic area or the ice sheet history. 1078 108 The contradiction in ideas between geophysicists and glacial geologists concerning the mode of glacial isostatic rebound in the southern Lake Michigan basin has been addressed ix: this investigation. .An empirical and theoretical approach has been utilized. The validity of the traditional interpretation of shoreline deformation and numerical modeling has been tested by comparison to published and new empirical data produced by this investigation. Recently published interpretations (e.g. Coordinating Committee of Basic Hydraulic and. Hydrologic Data 1977, Larsen 1985a, 1985b and Karrow and Calkins 1985) challenge the accepted traditional hinge line model of glacio-isostasy in the Lake Michigan basin. Analysis of lake gauge deleveling data and abandoned shorelines (Algonquin age and younger) suggest the southern Lake Michigan basin has been actively deforming during the past 12,000 years. Numerical modeling of glacio-isostatic processes also suggests active isostatic adjustment south of the Algonquin hinge line in the Lake Michigan basin over the past 12,000 years. In this investigation various earth and ice sheet models are modeled and compared to shoreline uplift, outlet Chronologies, and lake gauge deleveling data. The observed outlet Chronologies are completely compatible with numerical predictions of outlet elevations through time. In ‘the numerical model neither the Port Huron. nor the Chicago 109 outlets are isostatically stable as in the traditional model. The traditional model of stability within the southern Lake Michigan basin is not supported by lake gauge data. The lake gauge deleveling data suggests active isostatic adjustment similar to the numerical model predictions. The shoreline data north of the Algonquin hinge line is also adequately reproduced by the numerical modeling. South of the .Algonquin hinge line the traditional interpretations of the shoreline data cannot be reconciled with our current understanding of isostatic rebound. This investigation has addressed the possible existence of previously unrecognized, higher isostatically deformed shorelines in southwestern Michigan. The results of this investigation indicate that a significant amount of higher shoreline features, similar to the previously identified shoreline features, do exist above the traditional Lake Chicago shorelines. Furthermore, these shoreline features do trend up in elevation to the north. Selected field sites have been considered in some detail to evaluate their significance on regional and local interpretations. Two sites have been given maximum age dates by radiocarbon dating of wood within underlying deposits. Both features had maximum dates of approximately 11,500 years B.P. However, more dating will be necessary to 110 definitively place these shoreline features in a regional interpretation of major proglacial lake stages. An interpretation of a lacustrine transgression based upon the field data has been used to test the validity of the numerical model south of the Algonquin hinge line. The results of the numerical calculations are compatible with the new shoreline data. 0 In conclusion, this investigation finds the traditional interpretation of shoreline stratigraphy and "hinge line" glacio-isostasy for the southern Lake Michigan basin inconsistent with both theoretical and empirical' data. Furthermore, the analysis of higher lacustrine data, using similar criteria as previous workers in the same region, suggest a much higher, isostatically deformed transgression than previously thought. 110a ._....=._n5 APPENDICES APPENDIX A THE ICE SHEETS USED IN THE NUMERICAL CALCULATIONS Appendix A contains maps of ice sheet thicknesses (in meters) used in the two ice sheet models considered in this investigation. The two ice sheets are referred to throughout the text as the "thick and "thin" ice sheet models. The thick ice sheet model is modeled after the ice sheet reconstruction of Denton and Hughes (1981). The thin ice sheet model is modeled after the ice sheet reconstruction of Boulten et al. (1985). For this study, a 5 degree latitude by 5 degree longitude grid was used to define the North America ice sheets outside of the Great Lakes area. For greater resolution of ice histories and thickness in the Great Lakes area, a 2 .degree latitude by 2 degree longitude grid was used. The histories are similar to the isochrons of the Laurentide ice sheet given by Mayewski et al. (1981) in this region. In this appendix, ice sheet thicknesses for selected times before present are shown for each grid cell. The thicknesses for each selected time are shown on two separate maps because of the change in grid size. 111 112 \ W A k 1.] Figure A.l Ice Sheet Thickness (a) - Thick Ice Sheet 30,000 B.P. 113 \A\ \J 3‘ l as i use as: :22. as am am an zen-\q/ an an an an on nu man me me me am an; an an an m «I: J “a; x >5 ‘s—S I” 0. an m .2. I I“. I." III. II“ II” II“ I," III. i D A AS ‘1»; lee/mi Figure A.2 Ice Sheet Thickness (I) - Thick Ice Sheet 25,000 B.P. 114 M\\ \ \\\ I .. ...................\ ........... an Figure A.3 Ice Sheet Thickness (I) - Thick Ice Sheet 21,000 B.P. 115 MN \ \ \\\ .. e. .... .. .,.. use)... ..., .. amimumWasmasmma-uamammm acme-0mm: IIDHIMMIMMMHmRI' i \r 1:; m Figure A.4 Ice Sheet Thickness (I) - Thick Ice Sheet 18,000 B.P. 116 ”.mmmmm,,mchmm .. .. ,. my... .... .... .. ....euw-7r£ a...) i gigc/ffifi’ Figure A.5 Ice Sheet Thickness (I) - Thick Ice Sheet 17,000 B.P. 117 \A“ \ W l m I me nu nu me an use use ”\q/ as an an an msI ifi‘m use u. use an m m an all a. a. I 4 i B I Ill 3} .3)qu he I I I _T"'—‘: I I I ‘ . . . JM/ 1 (like. A K IV 4*] Figure A.6 Ice Sheet Thickness (I) - Thick Ice Sheet 16,000 B.P. 118 2“». \_ II .J’ Figure A.7 Ice Sheet Thickness (I) - Thick Ice Sheet 15.000 B.P. 119 V\\\ \ \V I MI I" I‘lmlul'mmm ”I." ..............,$.......................................... alumni-mu III. I’mm~~~fl” i We" ’ Figure A.8 Ice Sheet Thickness (I) - Thick Ice Sheet 14,000 B.P. 12C) I“ I. -~{ II I“ I" III '0 us II III III can III iII nII III III as the au- III III III III III i I “ II II II T i . [Ii - I M i (LI I 47' l Figure A.9 Ice Sheet Thickness (I) - Thick Ice Sheet 13,000 B.P. 121 . mmmmmets.;,_ a I L» Figure A.10 Ice Sheet Thickness (I) - Thick Ice Sheet 12,000 B.P. | 122 {I I!“ IIII II. “II “II II. I- . /" «(if I I “L, I i in \M y: \L- [‘9] I Figure A.11 Ice Sheet Thickness (n) - Thick Ice Sheet 11,000 B.P. 1J23 ”\H... ._., A“? . ‘3 I'LL“ Figure A.12 Ice Sheet Thickness (I) - Thick Ice Sheet 10,000 B.P. 124 _T' ' Zg;“‘”“” " ....B I 7 v i In Figure A.13 Ice Sheet Thickness (I) - Thick Ice Sheet 9,000 B.P. 125 ? _ B m / .7 I 79% 9L Ti in \L. ”NI Figure A.14 Ice Sheet Thi K ckness (m) - Thick Ice Sheet 8,000 B.P. 126 23...... IN H ll .zfi. /_ ——"”;._'"¢‘/' «If ' "r" Tiff'?* IDAW’ Figure A.15 Ice Sheet Thickness (n) - Thick Ice Sheet 7,000 B.P. J”? 127 I Figure A.16 Ice Sheet Thickness (I) - Thick Ice Sheet 6,000 B.P. 128 WK \ $1 1 I I I I I I I I x“ I I I L—— I I I {1% I I I I I I I I I I I | "i I I I I I I I ‘I I I I I I I b 1 . ,/m/ K K 7 JAI¥ Figure A.17 Ice Sheet Thickness (I) - Thick Ice Sheet 5,000 B.P. 129 i.‘ hf \L'JA; ’ Figure A.18 Ice Sheet Thickness (I) - Thick Ice Sheet 2,000 B.P. 130 \API\ IX ‘3‘“ l i I I III III III III III III I;>\<$~/Iflfl III III I I I 1E“). II II II II II III III III III 1 “> 1“. It I I./' Figure A.19 Ice Sheet Thickness (I) - Thin Ice Sheet 30,000 B.P. 131 Ix 3 A I J _II— III IIIJ firs III III III III III III "II III III III .H..m.m gimmmmm ”'9' ‘5‘?" . .. “3,1. ”I -§F *4; --I T 3 1' Figure A.20 Ice Sheet Thickness (ll) - Thin Ice Sheet 25,000 B.P. 132 \AW\3 w, l I --;mm-£f§F ‘ 3‘ , “Iv—- "”h 1’1 \g i LAC/731$; Figure A.21 Ice Sheet Thickness (I) - Thin Ice Sheet 21,000 B.P. N" .. .. .. C III I“ m m ~ I. III I. I- IIII I,“ u I,“ N I 1133 l‘\_ ““113 mmwmm~w~~ C A ---m , _¢_ mwc+x- -. ...u ,, — h j I 4\ a] A “\M l, 1 .1L_ Figure A.22 Ice Sheet Thickness (n) - Thin Ice Sheet 18,000 B.P. 134 -‘._mmemmm$gmmm mmmfiunmnmnmnmnmnmmmmm l _ [\‘f'YT" a Maw/mi Figure A.23 Ice Sheet Thickness (u) - Thin Ice Sheet 17,000 B.P. * 135 c _mmmmmm$wgmm “0mm afifimnmnmnmufluflnmaflmmm AS \' Ua/‘mfi’ Figure A.24 Ice Sheet Thickness (n) - Thin Ice Sheet 16,000 B.P. 1J36 ' mi. '3!‘ I __\ ’1 :3 I? it. R f. - I} .11, Figure A.25 Ice Sheet Thickness (n) - Thin Ice Sheet 15,000 B.P. 137 p D V EV —-.£ an up an an an an “$2: un- :21.- au no ace—+1:- 4'3, but: i AKA K J' W’ ' Figure A.26 Ice Sheet Thickness (n) - Thin Ice Sheet 14,000 B.P. 2138 ."7.........}...._ ' “Hi: '3} 44""33 L1 i. . It 'T—C . on} KI ‘\4%. f' JMI. . ; iizlg’ Figure A.27 Ice Sheet Thickness (n) - Thin Ice Sheet 13,000 B.P. 139‘ nfikmnmummnmsmnmmnmnflm fi‘fi C I sue fluent-cementum r Sir J >. L- L 1.] Figure A.28 Ice Sheet Thickness (n) - Thin Ice Sheet 12,000 B.P. 140 { “bx. 3 \IJI- ’ Figure A.29 Ice Sheet Thickness (n) - Thin Ice Sheet 10,000 B.P. 141 . ................IN\,/......... ooefleeeeemmmmum. ”'“vf'm'fl; ‘\ \L ILNW’ Figure A.30 Ice Sheet Thickness (n) - Thin Ice Sheet 9,000 B.P. "Ljé (33‘ 142 Vx\\\ \\x I . ............\M....... I I I fig. I I I I I I I I I I flag I I I I I I I INIQ;I_ ;Ifi- :EKTI—I .{jj' 413. H fl I I TI I I I.) _- ‘1 E; Lie/7%; Figure A.3I Ice Sheet Thickness (n) - Thin Ice Sheet 8,000 B.P. 143 “i \I- MW’ Figure A.32 Ice Sheet Thickness (I) - Thin Ice Sheet 7,000 B.P. 144 \A\\ \ - W l . p. AN ‘5 hie/m? Figure A.33 Ice Sheet Thickness (I) - Thin Ice Sheet 6,000 B.P. 145 ‘i Hem/7T6 Figure A.34 Ice Sheet Thickness (I) - Thin Ice Sheet 5,000 B.P. 146 “14) If - WW° “WK . . . 23%”; é 3) \i' LIME? Figure A.35 Ice Sheet Thickness (II) - Thin Ice Sheet 2,000 B.P. J M Jr“ - l 4:]; APPENDIX B THE DEFORMATIONS ASSOCIATED WITH EACH NUMERICAL CALCULATION Appendix B contains contour maps of earth deformation (in meters) for the numerical calculations considered in this investigation» The different calculations were developed by considering two earth models and two ice sheet models. The earth models had different lithosphere thicknesses (112 and 212 km). The combination of the thick and thin ice sheets (see Appendix A) and the thick and thin lithosphere resulted in four numerical models: 1) thick ice sheet - thick lithosphere; 2) thick ice sheet - thin lithosphere; 3) thin ice sheet - thick lithosphere; and 4) thin ice sheet - thin lithosphere. ’ The range in numerical predictions is demonstrated by considering the deformation from two of the numerical calculations. The maximum amount of deformation is observed when modeling a thick ice sheet on a thin lithosphere. The minimum amount of deformation is observed when modeling the thin ice sheet on the thick lithosphere. Results from the models are presented in this appendix. The results are presented as differential deformation (i.e., amount of deformation relative to the present earth surface) with respect to the center 'of the earth for In? 148 selected times before present. Two maps are presented for each selected time to demonstrate the deformation within the Great Lakes region and the North American Continent. Figure 3.1 Differential Defamation (in Ieters) Thick Ice Sheet - Thin Lithosphere 25,000 B.P. 150 Figure 0.2 Differential Deformation (in meters) Thick Ice Sheet - Thin Lithosphere 18,000 B.P. 2L52 ..— Figure 0.4 Differential Defbruation (in Ieters) Thick Ice Sheet - Thin Lithosphere 10,000 B.P. Figure 0.5 Differential Deforlation (in Ieters) Thick Ice Sheet - Thin Lithosphere 5,000 B.P. 1155 Figure 0.7 Differential Deformation (in meters) Thick Ice Sheet - Thick Lithosphere 25,000 B.P. e 0. D fferential Deformation (in Ieters) ee - k Lithosphere 10,000 B.P. Figure 0.11 Differential Deformation (in meters) Thick Ice Sheet - Thick Lithosphere 5,000 B.P. Figure 0.13 Differential Deformation (in meters) Thin Ice Sheet - Thick Lithosphere 25,000 B.P. 163 (in meters) Thin Ice Sheet - Thick Lithosphere 15,000 B.P. Figure 0.15 Differential Deformation 1164 meters) Thin Ice Sheet - Thick Lithosphere 10,000 B.P. Figure 0.16 Differential Deformation (in 1165 i.» V/Jieg- ‘ “I|I... '*: «£58 Figure 0.17 Differential Deformation (in meters) Thin Ice Sheet - Thick Lithosphere 5,000 B.P. s \ a»; RX erential Deformation (in meters) ck Lithosphere 1,000 B.P. I‘ h TTT .f. .4! Of. A e 9 8h 15 89 C 9.1 r U" 9.1 .1." ~$ FT Figure 0.19 Differential Deformation (in meters) Thin Ice Sheet - Thin Lithosphere 25,000 B.P. Figure 0.20 Differential Deformation (in meters) Thin Ice Sheet - Thin Lithosphere 10,000 B.P. 2168 Figure 0.21 Differential Deformation (in meters) Thin Ice Sheet - Thin Lithosphere 15,000 B.P. ' 1% 1% '0. \‘. ..—/ Figure 0.22 Differential Deformation (in meters) Thin Ice Sheet - Thin Lithosphere 10,000 B.P. 169 APPENDIX C This appendix is a site by site description of localities mapped as near-shore features or lacustrine sediments for the entire field area. They are listed in order from south to north. The criteria used in interpretation along with explanation of study area is found in Chapter 3. Each entry contains information describing the location of the site. This is done by indication the county, 7.5 minute topographic quadrangle, township, and sections in which the feature occurs. The author has also included the Universal Transverse Mercator coordinates which is shown as a grid system on all new 7.5 minute topographic sheets. The landform (e.g. ridge, scarp, etc.) or deposit (e.g. lacustrine units) along with the evidence for that feature is given. In this appendix evidence is not a description or argument for the interpretation of that feature it simply states what sort of criteria was involved to establish that location as a near-shore or lacustrine indication. For example, a transition from lacustrine sediments to a moraine is located based on topography so the evidence would be stated as "topographic”. Whereas if the site is interpreted as lacustrine clays the evidence is likely to be sedimentology. The author has also compiled sites mapped by other workers along with the sites produced by this study. These 1693 170 sites are indicated by stating the originator’s name as the evidence for that site. The sites for several earlier workers are recorded in Evenson (1972) and are. referenced only with respect to the latter. The descriptions for these sites are taken from the original work, and any further comments by this author will be shown enclosed by brackets (e.g. [my comments]). Many sites included it this appendix are from Evenson (9172). Along with "Evenson" a number appears as evidence. This number refers to the series number within each county given by Evenson (1972). The mapping of these features both by Evenson (1972 p.19) and this study was largely on a reconnaissance level. Therefore, most of the evidence is topographic or large scale sedimentologic features which are easily identified and mapped. Sites where greater detail was warranted are mentioned both in chapter 3 and the descriptions herein. The. descriptions given in this appendix are a brief statement of field conditions which are used to support the interpretations. There were three sites (31, 76, and 86) in ‘which maximum ages were determined by radiocarbon. All, three 'where wood samples from high organic soils or peats. These sites are described in detail in , section 3.2.4. The possibility that these sites are near-shore features and therefore provide maximum dates for transgressions is also considered it that section. 171 SITE #: 1 COUNTY: Berrien ELEVATION: 198m (650ft) 7.5 MIN. TOPO. QUADRANGLE(S): New Buffalo, West TOWNSHIP & SECTIONS: New Buffalo 16, 20, and 21 UTM COORDINATES: 4623.5N 519E LANDFORM/DEPOSIT: Topographic break EVIDENCE: Topographic DESCRIPTION: Transition from flat to hilly topography. SITE #: 2 COUNTY: Berrien ELEVATION: 188m (620ft) 7.5 MIN. TOPO. QUADRANGLE(S): New Buffalo, West TOWNSHIP & SECTIONS: New Buffalo 17 and 19 UTM COORDINATES: 4624N 518E LANDFORM/DEPOSIT: Beach ridge (?) EVIDENCE: Evenson 1 DESCRIPTION: Linear sand ridge, possibly a beach ridge. SITE #: 3 COUNTY: Berrien ELEVATION: 195m (640ft) 7.5 MIN. TOPO. QUADRANGLE(S): New Buffalo, East TOWNSHIP & SECTIONS: New Buffalo 9 and 10 UTM COORDINATES: 4626.3N 521E LANDFORM/DEPOSIT: Beach ridge of sand w/ pebbles EVIDENCE: Evenson 2 DESCRIPTION: Beach ridge of sand with pebbles. SITE #: 4 COUNTY: Berrien ELEVATION: 195m (640ft) 7.5 MIN. TOPO. QUADRANGLE(S): New Buffalo, East TOWNSHIP & SECTIONS: New Buffalo 10 UTM COORDINATES: 4626.5N 521.4E LANDFORM/DEPOSIT: Wave cut terrace EVIDENCE: Evenson 3 DESCRIPTION: Wave cut terrace (Leverett reports a gravel beach at this location. Evenson reports this but did not locate this feature.) SITE 5: 5 COUNTY: Berrien ELEVATION: 195m (640ft) 7.5 MIN. TOPO. QUADRANGLE(S): New Buffalo, East TOWNSHIP & SECTIONS: New Buffalo 10 UTM COORDINATES: 4626.5N 521.7E LANDFORM/DEPOSIT: Ridge composed of pebbly sand EVIDENCE: Evenson 4 DESCRIPTION: Ridge composed of pebbly sand. 172 SITE #: 6 COUNTY: Berrien ELEVATION: 195m (640ft) 7.5 MIN. TOPO. QUADRANGLE(S): New Buffalo, East TOWNSHIP a SECTIONS: New Buffalo 19 (center) UTM COORDINATES: 4632.7N 527.0E LANDFORM/DEPOSIT: Beach EVIDENCE: Evenson 5 DESCRIPTION: Elongated ridge of beach form (Leverett reports its lithology as gravel.) SITE #: 7 COUNTY: Berrien ELEVATION: 195m (640ft) 7.5 MIN. TOPO. QUADRANGLE(S): New Buffalo, East TOWNSHIP & SECTIONS: Chikaming 20 UTM COORDINATES: 4633.0N 528.4E LANDPORM/DEPOSIT: Wave cut terrace (?) EVIDENCE: Evenson 6 DESCRIPTION: Topographic break from flat to rolling surface (wave cut terrace) SITE #: 8 COUNTY: Berrien ELEVATION: 195m (640ft) 7.5 MIN. TOPO. QUADRANGLE(S): New Buffalo, East TOWNSHIP & SECTIONS: Chikaming 16 UTM COORDINATES: 4635.0N 530.3E LANDFORM/DEPOSIT: Ridge EVIDENCE: Evenson 7, topographic DESCRIPTION: Ridge of pebble free sand. SITE #: 9 COUNTY: Berrien ELEVATION: 195m (640ft) 7.5 MIN. TOPO. QUADRANGLE(S): Bridgman and New Buffalo, East TOWNSHIP & SECTIONS: Chikaming 2 and 10 UTM COORDINATES: 4637.0N 532.5E LANDFORM/DEPOSIT: Ridge EVIDENCE: Evenson 8 DESCRIPTION: Distinct topographic ridge 1-1/2 miles long composed of clean sand with occasional pebbles. 173 SITE #: 10 COUNTY: Berrien ELEVATION: 198m (650ft) 7.5 MIN. TOPO. QUADRANGLE(S): Bridgman and Baroda TOWNSHIP & SECTIONS: Baroda 14, 15, 22, 23, 25, 26, 27, 35 UTM COORDINATES: 4638.0N 543.0E north to 4645.0N 543.0E LANDFORM/DEPOSIT: Lacustrine plain and topographic break EVIDENCE: Topographic DESCRIPTION: Extensive flat lacustrine plain. Also mapped as lacustrine by Farrand (1982). SITE #: 11 COUNTY: Berrien ELEVATION: 195m (64lft) 7.5 MIN. TOPO. QUADRANGLE(S): Bridgman TOWNSHIP & SECTIONS: Lake 30 UTM COORDINATES: 4641.6N 536.0E LANDFORM/DEPOSIT: Ridge EVIDENCE: Evenson 10 DESCRIPTION: Ridge of sand with occasional pebbles (Also mapped as Glenwood beach by Tague.) SITE #: 12 COUNTY: Berrien ELEVATION: 195m (640ft) 7.5 MIN. TOPO. QUADRANGLE(S): Bridgman TOWNSHIP & SECTIONS: Lake 18 and 19 (?) UTM COORDINATES: 4643.3N 536.5E LANDFORM/DEPOSIT: Ridge EVIDENCE: Evenson 11 DESCRIPTION: Sandy ridge. SITE #: 13 COUNTY: Berrien ELEVATION: 198m (650ft) 7.5 MIN. TOPO. QUADRANGLE(S): Baroda TOWNSHIP & SECTIONS: Baroda 3, 4, 9, and 10 UTM COORDINATES: 4646.5N 540.5E LANDFORM/DEPOSIT: Topographic break and lacustrines EVIDENCE: Topographic DESCRIPTION: Sharp topographic break from flat (also lack of gradient) to rolling topography. This site is continuous with sites 14 and 16. 174 SITE #: l4 COUNTY: Berrien ELEVATION: 201m (660ft) 7.5 MIN. TOPO. QUADRANGLE(S): Baroda TOWNSHIP & SECTIONS: Oronko 4, 5, and 6 ‘ UTM COORDINATES: 4646.7N 546.0E north to 4648.0N 549.0E LANDFORM/DEPOSIT: Lacustrine plain and topographic break EVIDENCE: Topographic DESCRIPTION: Sharp topographic break from flat to . hilly topography. Also continuous with sites 13 and 16. SITE #: 15 COUNTY: Berrien ELEVATION: 195m (640ft) 7.5 MIN. TOPO. QUADRANGLE(S): Bridgman TOWNSHIP & SECTIONS: Lake 4 UTM COORDINATES: 4648.1N 538.6E LANDFORM/DEPOSIT: EVIDENCE: Evenson 12 DESCRIPTION: 2' clean brown sand with pebbles up to 3" (also mapped by Tague) SITE #: 16 COUNTY: Berrien ELEVATION: 201m (660ft) 7.5 MIN. TOPO. QUADRANGLE(S): Baroda and Benton Harbor TOWNSHIP & SECTIONS: Royalton 30, 21, 32, and 33 UTM COORDINATES: 4649.0N 546.0E northeast to 4649.5N 548.0E LANDFORM/DEPOSIT: Lacustrine plain and topographic break EVIDENCE: Topographic DESCRIPTION: Sharp topographic break and lacustrine plain. Also see sites 13 and 14. SITE #: 17 COUNTY: Berrien ELEVATION: 197m (647ft) 7.5 MIN. TOPO. QUADRANGLE(S): Benton Harbor TOWNSHIP & SECTIONS: Sodus 15 and 22 UTM COORDINATES: 4653.0N 550.0E LANDFORM/DEPOSIT: Terrace EVIDENCE: Evenson 14 DESCRIPTION: Terrace on St. Joseph River. SITE #: 18 COUNTY: Berrien ELEVATION: 198m (650ft) 7.5 MIN. TOPO. QUADRANGLE(S): Benton Harbor TOWNSHIP & SECTIONS: Sodus 17 UTM COORDINATES: 4653.5n 547.8E LANDFORM/DEPOSIT: Topographic break EVIDENCE: Topographic DESCRIPTION: Transition from flat to hilly . topography. 175 SITE #: 19 COUNTY: Berrien ELEVATION: 198m (650ft) 7.5 MIN. TOPO. QUADRANGLE(S): Benton Harbor TOWNSHIP & SECTIONS: Lincoln 13 UTM COORDINATES: 4653.5N 544.0E LANDFORM/DEPOSIT: Topographic break EVIDENCE: Topographic DESCRIPTION: Transition from flat to hilly topography. SITE #: 20 COUNTY: Berrien ELEVATION: 197m (647ft) 7.5 MIN. TOPO. QUADRANGLE(S): Benton Harbor TOWNSHIP & SECTIONS: Sodus 6 UTM COORDINATES: 4657.0N 546.0E LANDFORM/DEPOSIT: Terrace EVIDENCE: Evenson 13, topographic DESCRIPTION: Terrace on St. Joseph River. SITE #: 21 COUNTY: Berrien ELEVATION: 210m (690ft) 7.5 MIN. TOPO. QUADRANGLE(S): Sodus and Benton Harbor TOWNSHIP & SECTIONS: Benton 14, 23, 26, and 35 UTM COORDINATES: 4662.0N 551.2E to 4660.0N 552.0E to 4658.0N 552.0E LANDFORM/DEPOSIT: Wave Cut (?) EVIDENCE: Topographic DESCRIPTION: Relatively steep bluff. Could be a wave cut bluff, however, no evidence outside of the topographic relief was observed in the field. SITE #: 22 COUNTY: Berrien ELEVATION: 199m (655ft) 7.5 MIN. TOPO. QUADRANGLE(S): Benton Harbor TOWNSHIP & SECTIONS: Benton 27 UTM COORDINATES: 4660.8N 550.8E LANDFORM/DEPOSIT: Lacustrine plain EVIDENCE: Evenson 15, topographic DESCRIPTION: Lacustrine silts and clay forming an extensive flat. 176 SITE #: 23 COUNTY: Berrien ELEVATION: 198m (650ft) 7.5 MIN. TOPO. QUADRANGLE(S): Benton Harbor TOWNSHIP & SECTIONS: Benton 22 and 27 UTM COORDINATES: 4662.0N 550.6E LANDFORM/DEPOSIT: Topographic break and possible wave cut EVIDENCE: Topographic DESCRIPTION: Topographic transition. Break is unusually steep suggesting possible wave cut bluff. SITE #: 24 COUNTY: Berrien ELEVATION: 207m (680ft) 7.5 MIN. TOPO. QUADRANGLE(S): Coloma TOWNSHIP & SECTIONS: Bainbridge 6 and 7 UTM COORDINATES: 4665.5N 555.5E LANDFORM/DEPOSIT: Wave cut bluff (?) EVIDENCE: Topographic DESCRIPTION: Steep bluff evident from topographic map. No additional field evidence to substantiate this interpretation. SITE #: 25 COUNTY: Berrien ELEVATION: 210m (690ft) 7.5 MIN. TOPO. QUADRANGLE(S): Coloma TOWNSHIP & SECTIONS: Coloma 29, 33, and 34 UTM COORDINATES: 4667.0N 560.0E LANDFORM/DEPOSIT: Bluff and topographic break EVIDENCE: Topographic DESCRIPTION: Transition from flat to hilly topography. SITE #: 26 COUNTY: Berrien ELEVATION: 207m (680ft) 7.5 MIN. TOPO. QUADRANGLE(S): Coloma TOWNSHIP & SECTIONS: Hagar 35 UTM COORDINATES: 4668.0N 552.5E LANDFORM/DEPOSIT: Wave cut bluff EVIDENCE: Topographic DESCRIPTION: Steep bluff with base at 207m (680ft). SITE #: 27 COUNTY: Berrien ELEVATION: 198m (650ft) 7.5 MIN. TOPO. QUADRANGLE(S): Benton Heights TOWNSHIP & SECTIONS: Hagar 32, 33, and 35 UTM COORDINATES: 4668.0N 548.0E northeast to 4668.7N 553.0E LANDFORM/DEPOSIT: Lacustrine plain EVIDENCE: Evenson 16, 17, 18, and topographic DESCRIPTION: [Flat sandy plain dissected by Paw Paw River with terraces.] 177 SITE #: 28 COUNTY: Berrien ELEVATION: 198m (650ft) 7.5 MIN. TOPO. QUADRANGLE(S): Coloma TOWNSHIP & SECTIONS: Hagar 25 . UTM COORDINATES: 4669.5N 554.0E LANDFORM/DEPOSIT: Topographic break EVIDENCE: Topographic and Evenson 19 DESCRIPTION: Distinct terrace bounded by scarp on east; terrace flat is composed of pebbly sand. SITE #: 29 COUNTY: Berrien ELEVATION: 198m (650ft) 7.5 MIN. TOPO. QUADRANGLE(S): Coloma TOWNSHIP & SECTIONS: Watervliet 26 UTM COORDINATES: 4670.2N 561.0E LANDFORM/DEPOSIT: Terrace EVIDENCE: Evenson 20 DESCRIPTION: Terrace of Paw Paw River bonded on south by scarp. SITE #: 30 COUNTY: Berrien ELEVATION: 204m (670ft) 7.5 MIN. TOPO. QUADRANGLE(S): Benton Heights TOWNSHIP & SECTIONS: Hagar 14 and 15 UTM COORDINATES: 4672.5N 550.8E LANDFORM/DEPOSIT: Wave cut bluff EVIDENCE: Topographic DESCRIPTION: Sharp topographic break indicating possible wave cut bluff. SITE #: 31 COUNTY: Berrien ELEVATION: 211m (695ft) 7.5 MIN. TOPO. QUADRANGLE(S): Benton Heights TOWNSHIP & SECTIONS: Hagar 15 UTM COORDINATES: 4672.6N 550.3E LANDFORM/DEPOSIT: Lacustrine plain EVIDENCE: Topographic, field, and sedimentology DESCRIPTION: Lacustrine sediments on top of the Lake Border moraine. Several cores indicated horizontally bedded sands and silts over 1500 hundred square meters. The deposit is a fining upward sequence approximately 1.5m (4-5ft) thick and is underlain by gray glacial till. There is a soil developed on the till which contains wood. The wood has been dated by Beta Analytic Inc. at 11,650 +/- 130 B.P. This site is described in detail in section 4.2.4.1. 178 SITE #: 32 COUNTY: VanBuren ELEVATION: 204m (670ft) 7.5 MIN. TOPO. QUADRANGLE(S): McDonald TOWNSHIP & SECTIONS: Bangor 27, 28, and 33 UTM COORDINATES: 4679.0N 568.2E LANDFORM/DEPOSIT: Bluff EVIDENCE: Topographic DESCRIPTION: Bluff on the east side of VanAuken Lake with a base at 204m. SITE #: 33 COUNTY: VanBuren ELEVATION: 213m (700ft) 7.5 MIN. TOPO. QUADRANGLE(S): McDonald, Bangor, and Pullman TOWNSHIP & SECTIONS: several UTM COORDINATES: 4681.6N 574.3E to 4689.0N 577.0E to ' 4699.0N 581.0E to 4705.0 LANDFORM/DEPOSIT: Ridge, wave cut, and dune (?) EVIDENCE: Topographic and field DESCRIPTION: A ridge which consistently located adjacent to a transition from flat to hilly 'topography. The *topographic break ranges from 680 to 700 ft. while the ridge in consistently at 700 ft. SITE #: 34 COUNTY: VanBuren ELEVATION: 204m (670ft) 7.5 MIN. TOPO. QUADRANGLE(S): McDonald TOWNSHIP & SECTIONS: Bangor 17 UTM COORDINATES: 4682.5N 566.3E LANDFORM/DEPOSIT: Topographic break EVIDENCE: Topographic DESCRIPTION: Transition from flat to hilly topography at an elevation of 665 to 670 ft. SITE #: 35 COUNTY: VanBuren ELEVATION: 198m (652ft) 7.5 MIN. TOPO. QUADRANGLE(S): Covert TOWNSHIP & SECTIONS: South Haven 27 UTM COORDINATES: 4689.8N 560.0E LANDFORM/DEPOSIT: Beach EVIDENCE: Evenson 2, 3, and 4 DESCRIPTION: 2) Beach ridge composed of pebbly sand. 3) 2 feet of pebbly beach sand over blue to gray till. 4) Well- developed graves forming low ridge. 179 SITE #: 36 COUNTY: VanBuren ELEVATION: 189m (621ft) 7.5 MIN. TOPO. QUADRANGLE(S): Lacota TOWNSHIP & SECTIONS: Geneva 7 UTM COORDINATES: 4694.0N 565.0E LANDFORM/DEPOSIT: Terrace EVIDENCE: DESCRIPTION: Large flat sand terrace of Black River. Large sand pit shows good cross-bedding. SITE #: 37 COUNTY: Allegan ELEVATION: 198m (652ft) 7.5 MIN. TOPO. QUADRANGLE(S): Lacota TOWNSHIP & SECTIONS: Casco 18 UTM COORDINATES: Bluff LANDFORM/DEPOSIT: Bluff EVIDENCE: Evenson 1 DESCRIPTION: Sand with pebbles (beach) over gray till. SITE #: 38 COUNTY: Allegan ELEVATION: 211m (695ft) 7.5 MIN. TOPO. QUADRANGLE(S): Allegan ‘ TOWNSHIP & SECTIONS: Trowbridge 4; Allegan 32 and 33 UTM COORDINATES: 4706.3N 594.4E LANDFORM/DEPOSIT: River Terrace EVIDENCE: Topographic DESCRIPTION: Terraces along the Kalamazoo River. SITE #: 39 COUNTY: Allegan ELEVATION: 199m (655ft) 7.5 MIN. TOPO. QUADRANGLE(S): Glenn TOWNSHIP & SECTIONS: Ganges 30 UTM COORDINATES: 4708.3N 562.5E LANDFORM/DEPOSIT: Linear sand ridge EVIDENCE: Evenson 2 DESCRIPTION: Linear ridge of sand may be beach on dune. . SITE #: 40 COUNTY: Allegan ELEVATION: 198m (650ft) 7.5 MIN. TOPO. QUADRANGLE(S): Glenn. TOWNSHIP & SECTIONS: Ganges 22 and 27 UTM COORDINATES: 4709.2N 567.3E LANDFORM/DEPOSIT: Topographic break EVIDENCE: Evenson 3 and topographic DESCRIPTION: Strong topographic break from flat - sands to rolling till. 180 SITE #: 41 COUNTY: Allegan ELEVATION: 198m (650ft) 7.5 MIN. TOPO. QUADRANGLE(S): Glenn TOWNSHIP & SECTIONS: Ganges 22 UTM COORDINATES: LANDFORM/DEPOSIT: Topographic break EVIDENCE: Evenson 4 and topographic DESCRIPTION: Topographic break [on the inside of the Lake Border Moraine.] SITE #: 42 COUNTY: Allegan ELEVATION: 198m (650ft) 7.5 MIN. TOPO. QUADRANGLE(S): Fennville TOWNSHIP & SECTIONS: Clyde 20 UTM COORDINATES: 4710.0N 574.0E LANDFORM/DEPOSIT: Topographic break EVIDENCE: Evenson 5 DESCRIPTION: Topographic break between flat plain and rolling hills [on the inside of the Lake Border Moraine.] SITE #: 43 COUNTY: Allegan ELEVATION: 198m (650ft) 7.5 MIN. TOPO. QUADRANGLE(S): Glenn TOWNSHIP & SECTIONS: Saugatuck 32 UTM COORDINATES: 4716.5N 564.3E LANDFORM/DEPOSIT: Topographic break with possible beach EVIDENCE: Evenson 6 DESCRIPTION: Topographic break, pebbly sand to 650', dune sand above 650’ [Topographic break above this at 700’ with a possible spit at 690']. SITE #: 44 COUNTY: Allegan ELEVATION: 210m (690ft) 7.5 MIN. TOPO. QUADRANGLE(S): Millgrove TOWNSHIP & SECTIONS: Heath 26 and 35 UTM COORDINATES: 4717.0N 587.0E LANDFORM/DEPOSIT: Topographic break EVIDENCE: Topographic DESCRIPTION: Extensive flat plain up to 210m (690ft). SITE #: 45 COUNTY: Allegan ELEVATION: 210m (690ft) 7.5 MIN. TOPO. QUADRANGLE(S): Glenn TOWNSHIP & SECTIONS: Saugatuck 28, 29 and 33 UTM COORDINATES: 4717.5N 565.0E LANDFORM/DEPOSIT: Split EVIDENCE: Topographic DESCRIPTION: Recurved spit just below a topographic break. ' 181 SITE #: 46 COUNTY: Allegan ELEVATION: 198m (650ft) 7.5 MIN. TOPO. QUADRANGLE(S): Hamilton West, Saugatuck, Glenn, and Fennville TOWNSHIP & SECTIONS: Manlus 17, 20, 21, 28, 29, 30, and 33 UTM COORDINATES: 4720.0N 573.4E LANDFORM/DEPOSIT: Beach EVIDENCE: Evenson 10 and 11 DESCRIPTION: 10) Patches of pebbly beach sand over gray till; 11) Clean beach sand in a cut into gray till. [Presently there are some pits and stream cuts in this beach and topographic break]. SITE #: 47 COUNTY: Allegan ELEVATION: 198m (650ft) 7.5 MIN. TOPO. QUADRANGLE(S): Saugatuck TOWNSHIP & SECTIONS: Saugatuck 20 UTM COORDINATES: 4720.5N 563.5E LANDPORM/DEPOSIT: Lacustrine plain EVIDENCE: Evenson 9 DESCRIPTION: Topographic contrast, sandy flat joins spit described in entry 49 and 48. SITE #: 48 COUNTY: Allegan ELEVATION: 198m (650ft) 7.5 MIN. TOPO. QUADRANGLE(S): Saugatuck TOWNSHIP & SECTIONS: Saugatuck 16 UTM COORDINATES: 4721.2N 565.0E LANDFORM/DEPOSIT: Spit EVIDENCE: Evenson 7 DESCRIPTION: South are of recurved spit-like pebbly sand. ridge built into embayment of Kalamazoo River. SITE #: 49 COUNTY: Allegan ELEVATION: 198m (650ft) 7.5 MIN. TOPO. QUADRANGLE(S): Saugatuck TOWNSHIP & SECTIONS: Saugatuck 16 UTM COORDINATES: 4721.2N 565.0E LANDFORM/DEPOSIT: Spit EVIDENCE: Evenson 8 DESCRIPTION: North arm of spit described in previous entry. 182 SITE #: 50 COUNTY: Allegan ELEVATION: 210m (690ft) 7.5 MIN. TOPO. QUADRANGLE(S): Hamilton, East TOWNSHIP & SECTIONS: Heath 13 and 14 UTM COORDINATES: 4722.4N 588.0E LANDFORM/DEPOSIT: Topographic break EVIDENCE: Topographic DESCRIPTION: Base of dune complex at 210m (690ft) on a flat plain. SITE #: 51 COUNTY: Allegan ELEVATION: 195m (640ft) 7.5 MIN. TOPO. QUADRANGLE(S): Saugatuck TOWNSHIP & SECTIONS: Saugatuck 12 UTM COORDINATES: 4723.5N 570.0E LANDFORM/DEPOSIT: Scarp EVIDENCE: Topographic DESCRIPTION: River cut in scarp. SITE #: 52 COUNTY: Allegan ELEVATION: 216m (710ft) 7.5 MIN. TOPO. QUADRANGLE(S): Burnips TOWNSHIP & SECTIONS: Monterey 2 and 3 UTM COORDINATES: 4724.4N 596.0E LANDFORM/DEPOSIT: Topographic break EVIDENCE: Topographic DESCRIPTION: - Transition from flat plain to hilly topography. SITE #: 53 COUNTY: Allegan ELEVATION: 207m (680ft) 7.5 MIN. TOPO. QUADRANGLE(S): Hamilton, East TOWNSHIP & SECTIONS: Overisel 28, 29, and 21 UTM COORDINATES: 4728.0N 582.6E LANDFORM/DEPOSIT: Topographic break EVIDENCE: Topographic DESCRIPTION: Topographic break. Outwash/till transition according to Farrand (1982). Evenson says fluvial sand over till, however there is no direct evidence to rule out lacustrine. 183 SITE #: 54 COUNTY: Allegan ELEVATION: 200m (658ft) 7.5 MIN. TOPO. QUADRANGLE(S): Hamilton, East TOWNSHIP & SECTIONS: Overisel 28 UTM COORDINATES: 4728.00N 584.5E LANDFORM/DEPOSIT: Sand/till contact EVIDENCE: Evenson 13 DESCRIPTION: Contact between fine clean fluvial sands and till. SITE #: 55 COUNTY: Allegan ELEVATION: 201m (660ft) 7.5 MIN. TOPO. QUADRANGLE(S): Hamilton, East TOWNSHIP & SECTIONS: Overisel 26 UTM COORDINATES: 4728.0N 588.0E LANDFORM/DEPOSIT: Kame EVIDENCE: Evenson 15 DESCRIPTION: Large Kame (?) 1 mile square surrounded by sand to and elevation of approximately 660'. SITE #: 56 COUNTY: Allegan ELEVATION: 213m (700ft) 7.5 MIN. TOPO. QUADRANGLE(S): Saugatuck TOWNSHIP & SECTIONS: Laketown 22 and 27 UTM COORDINATES: 4728.0N 567.5E LANDFORM/DEPOSIT: Wave cut terrace EVIDENCE: Topographic DESCRIPTION: Ridge cut into hillside at 213m (700ft). SITE #: 57 COUNTY: Allegan ELEVATION: 213m (700ft) 7.5 MIN. TOPO. QUADRANGLE(S): Burnips TOWNSHIP & SECTIONS: Dorr 3O UTM COORDINATES: 4728.0N 600.7E LANDFORM/DEPOSIT: Topographic break EVIDENCE: Topographic DESCRIPTION: Transition from flat plain to hilly topography. SITE #: 58 COUNTY: Allegan ELEVATION: 198m (650ft) 7.5 MIN. TOPO. QUADRANGLE(S): Hamilton, East TOWNSHIP & SECTIONS: Overisel 22, 23, 26, and 27 UTM COORDINATES: 4729.0N 586.0E LANDFORM/DEPOSIT: lacustrine sands on till EVIDENCE: Evenson 14 DESCRIPTION: Extensive flat composed of bedded sands over gray till. 184 SITE 5: 59 COUNTY: Allegan ELEVATION: 216m (710ft) 7.5 MIN. TOPO. QUADRANGLE(S): Hamilton, East TOWNSHIP & SECTIONS: Overisel 19 UTM COORDINATES: 4729.3N 581.0E LANDFORM/DEPOSIT: Topographic break EVIDENCE: Topographic DESCRIPTION: Transition from flat plain to hilly topography. SITE #: 60 COUNTY: Allegan ELEVATION: 210m (690ft) 7.5 MIN. TOPO. QUADRANGLE(S): Hamilton, East TOWNSHIP & SECTIONS: Fillmore 20 and 21 UTM COORDINATES: 4729.8N 573.5E LANDFORM/DEPOSIT: Topographic break EVIDENCE: Topographic p DESCRIPTION: Strong topographic break from flat plain to hilly topography. SITE #: 61 COUNTY: Allegan ELEVATION: 210m (690ft) 7.5 MIN. TOPO. QUADRANGLE(S): Hamilton, West TOWNSHIP & SECTIONS: Fillmore 23 ' UTM COORDINATES: 4730.0N 578.0E LANDFORM/DEPOSIT: Topographic break EVIDENCE: Topographic DESCRIPTION: Transition from flat to hilly topography. SITE #: 62 COUNTY: Allegan ELEVATION: 213m (700ft) 7.5 MIN. TOPO. QUADRANGLE(S): Saugatuck TOWNSHIP & SECTIONS: Laketown 12 UTM COORDINATES: 4732.2N 570.0E LANDFORM/DEPOSIT: Topographic break EVIDENCE: Topographic DESCRIPTION: Transition from flat to hilly topography. 185 SITE #: 63 COUNTY: Allegan ELEVATION: 210m (690ft) 7.5 MIN. TOPO. QUADRANGLE(S): Burnips and Hudsonville, East TOWNSHIP & SECTIONS: Salem 11 UTM COORDINATES: 4733.5N 597.0E LANDFORM/DEPOSIT: Topographic break EVIDENCE: Topographic DESCRIPTION: Transition from flat to hilly topography. SITE #: 64 COUNTY: Allegan ELEVATION: 199m (655ft) 7.5 MIN. TOPO. QUADRANGLE(S): Saugatuck and Holland West TOWNSHIP & SECTIONS: Laketon 1 and 2 UTM COORDINATES: 4734.0N 569.0E LANDFORM/DEPOSIT: Topographic break EVIDENCE: Evenson 16 and 17 DESCRIPTION: Beach gravels over gray clay till. SITE #: 65 COUNTY: Ottawa/Allegan ELEVATION: 199m (655ft) 7.5 MIN. TOPO. QUADRANGLE(S): Holland East TOWNSHIP & SECTIONS: Fillmore 6 UTM COORDINATES: 4734.7N 571.6E LANDFORM/DEPOSIT: Topographic and Evenson EVIDENCE: Evenson and Topographic DESCRIPTION: Beach gravels grading into gray till as one process south. SITE #: 66 COUNTY: Ottawa ELEVATION: 198m (652ft) 7.5 MIN. TOPO. QUADRANGLE(S): Holland East TOWNSHIP & SECTIONS: Holland 27 UTM COORDINATES: 4737.3N 576.0E LANDFORM/DEPOSIT: Beach gravels over till EVIDENCE: Evenson 2 DESCRIPTION: Beach gravels over till [on topographic break from the Macatawa River terrace (terrace 650’). 186 SITE #: 67 COUNTY: Ottawa ELEVATION: 198m (650ft) 7.5 MIN. TOPO. QUADRANGLE(S): Holland East TOWNSHIP & SECTIONS: Zeeland 30 UTM COORDINATES: 4737.3N 576.0E LANDFORM/DEPOSIT: Delta EVIDENCE: Evenson 5 DESCRIPTION: Pebbly terrace or delta sand. SITE #: 68 COUNTY: Ottawa ELEVATION: 189m (623ft) 7.5 MIN. TOPO. QUADRANGLE(S): Holland East TOWNSHIP & SECTIONS: Zeeland 19, 24, 25, and 30 UTM COORDINATES: 4738.0N 581.0E LANDFORM/DEPOSIT: Scarp EVIDENCE: Evenson 4 and topographic DESCRIPTION: Scarp SITE #: 69 COUNTY: Ottawa ELEVATION: 216m (710ft) 7.5 MIN. TOPO. QUADRANGLE(S): Hudsonville, West TOWNSHIP & SECTIONS: Zeeland 23, 25, and 36 UTM COORDINATES: 4738.0N 588.0E LANDFORM/DEPOSIT: Topographic break EVIDENCE: Topographic DESCRIPTION: Transition from gently climbing plain to hilly topography. SITE 9: 70 COUNTY: Ottawa ELEVATION: 199m (655ft) 7.5 MIN. TOPO. QUADRANGLE(S): Hudsonville West TOWNSHIP & SECTIONS: Zeeland 20 UTM COORDINATES: 4739.0N 582.0E LANDFORM/DEPOSIT: Delta EVIDENCE: Evenson 6. DESCRIPTION: Gravel pit in flat delta surface. SITE #: 71 COUNTY: Ottawa ELEVATION: 213m (700ft) 7.5 MIN. TOPO. QUADRANGLE(S): Hudsonville, West TOWNSHIP & SECTIONS: Zeeland 3 and 4 UTM COORDINATES: 4745.0N 585.5E LANDFORM/DEPOSIT: Weak topographic break EVIDENCE: Topographic DESCRIPTION: A weak topographic break at 700’ with sand on top of till to at least 705'. 187 SITE #: 72 COUNTY: Kent ELEVATION: 216m (710ft) 7.5 MIN. TOPO. QUADRANGLE(S): Hudsonville, East TOWNSHIP & SECTIONS: UTM COORDINATES: Wyoming 29, 30 and 31 4746.0N 601.0E LANDFORM/DEPOSIT: Topographic break EVIDENCE: Topographic DESCRIPTION: Several topographic transition in this area from flat to hilly. Plain is traced to the Dorr channel. SITE #: 73 COUNTY: Ottawa ELEVATION: 204m (670ft) 7.5 MIN. TOPO. QUADRANGLE(S): Allendale TOWNSHIP & SECTIONS: UTM COORDINATES: Georgetown 30 4747.8N 590.2e LANDFORM/DEPOSIT: Topographic break EVIDENCE: Topographic DESCRIPTION: Strong transitional feature from flat plain to hilly topography. SITE #: 74 COUNTY: Ottawa ELEVATION: 199m (655ft) 7.5 MIN. TOPO. QUADRANGLE(S): Borculo TOWNSHIP & SECTIONS: UTM COORDINATES: Blendon 21, 22, 23, and 28 4748.0N 574.5E LANDFORM/DEPOSIT: Beaches (?) EVIDENCE: Evenson 9 and topographic DESCRIPTION: Clean sand with pebbles set into gray till. SITE #: 75 COUNTY: Ottawa ELEVATION: 204m (670ft) 7.5 MIN. TOPO. QUADRANGLE(S): Allendale TOWNSHIP & SECTIONS: UTM COORDINATES: LANDFORM/DEPOSIT: EVIDENCE: DESCRIPTION: T6N R13W 18 4751.0N 590.5E Linear sand ridge, beach, bar, or dune Field and topographic Long linear sand ridge at 670' with "back beach" deposit. This feature is in the same setting as the dated site (entry 86). The sand is clean and well sorted with no - observed sedimentary features. 188 SITE #: 76 COUNTY: Ottawa ELEVATION: 201m (660ft) 7.5 MIN. TOPO. QUADRANGLE(S): Allendale TOWNSHIP & SECTIONS: T6N R14W 12, UTM COORDINATES: 4752.3N 589.7E . LANDFORM/DEPOSIT: Fluvial sediments (?) over 'till (Evenson reports delta sediments associated with the Allendale delta. EVIDENCE : Evens on 7 and l O , fie 1d, sedimentology, and radiocarbon. DESCRIPTION: Sand, gravel, clays, silts, intermixed over gray till. Peat with stumps up to 15cm in diameter. No sedimentary features to distinguish between fluvial and lacustrine. However, wood from the peat was dated at 6120+/-100 B.P.. This strongly suggests a fluvial origin. SITE #: 77 COUNTY: Ottawa ELEVATION: 208m (685ft) 7.5 MIN. TOPO. QUADRANGLE(S): Allendale TOWNSHIP & SECTIONS: Tallmadge 30 and 31 UTM COORDINATES: 4757.0N 590.3E LANDFORM/DEPOSIT: Lacustrine/till transition EVIDENCE: Evenson 11 and soil change DESCRIPTION: [Topographic break at 660-670’ Evenson reports sands 1/4 mile east of 48th ave. at 658-660'. The elevation at this location is 680-690']. SITE #: 78 COUNTY: Ottawa ELEVATION: 216m (710ft) 7.5 MIN. TOPO. QUADRANGLE(S): Grandville TOWNSHIP & SECTIONS: Tallmadge 14, 22, and 23 UTM COORDINATES: 4759.0N 596.5E LANDFORM/DEPOSIT: Delta EVIDENCE: Topographic DESCRIPTION: Extensive plain associated with sand . creek. Possibly and ice-contact delta. 189 SITE #: 79 COUNTY: Ottawa ELEVATION: 188m (620ft) 7.5 MIN. TOPO. QUADRANGLE(S): Allendale TOWNSHIP & SECTIONS: Allendale 22 UTM COORDINATES: 4759.0N 584.0E LANDFORM/DEPOSIT: Cannel floor EVIDENCE: Evenson 12 DESCRIPTION: Channel with its floor at 620'. This is one of a number of a number of channels in this area floored at approx. 620'. SITE 4: 80 COUNTY: Ottawa ELEVATION: 198m (652ft) 7.5 MIN. TOPO. QUADRANGLE(S): Coopersville TOWNSHIP & SECTIONS: Polkton 33 UTM COORDINATES: 4765.0N 584.0E LANDFORM/DEPOSIT: Pebbly sand EVIDENCE: Evenson 14 DESCRIPTION: 1.5 pebbly sand over gray clay till immediately east, till forms surface. SITE #: 81 COUNTY: Muskegon ELEVATION: 204m (670ft) 7.5 MIN. TOPO. QUADRANGLE(S): Sullivan TOWNSHIP & SECTIONS: Ravenna l and 2; Sullivan 6 UTM COORDINATES: 4783.7N 577.0E east to 4783.7N 580.0E LANDFORM/DEPOSIT: Topographic break and dunes EVIDENCE: Evenson 1 and topographic DESCRIPTION: Topographic break and apparent dunes. SITE #: 82 COUNTY: Muskegon ELEVATION: 210m (690ft) 7.5 MIN. TOPO. QUADRANGLE(S): Sullivan TOWNSHIP & SECTIONS: Egelstron 35 and 36; Morland 31 and 32 UTM COORDINATES: 4784.5N 577.0E east to 4784.5N 580.0E LANDFORM/DEPOSIT: Topographic break with several near- shore features EVIDENCE: Topographic DESCRIPTION: In these sections along a till ridge there is a smattering of things which could be nearshore features. 190 SITE #: 83 COUNTY: Ottawa ELEVATION: 222m (730ft) 7.5 MIN. TOPO. QUADRANGLE(S): Ravenna TOWNSHIP & SECTIONS: Casnovia 30, 31, and 32 UTM COORDINATES: 4786.0N 589.7E LANDFORM/DEPOSIT: Ridge on till EVIDENCE: Topographic, field, and sedimentology DESCRIPTION: Prominent ridge formed on side of till. Gravel pits exhibit lacustrines over fluvial gravels. Evidence includes: forset beds, lag deposits, and oscillation ripples. SITE #: 84 COUNTY: MUskegon ELEVATION: 216m (710ft) 7.5 MIN. TOPO. QUADRANGLE(S): Ravenna TOWNSHIP & SECTIONS: Moorland 22, 23, 27, 32, and 33 UTM COORDINATES: 4788.0N 585.0E - LANDFORM/DEPOSIT: Topographic break EVIDENCE: Topographic DESCRIPTION: Strong transitional topography. Extensive sandy plain up to at least 700'. SITE #: 85 COUNTY: Muskegon ELEVATION: 219m (720ft) 7.5 MIN. TOPO. QUADRANGLE(S): Bridgeton TOWNSHIP & SECTIONS: Casnovia 17 and 18 UTM COORDINATES: 4790.0N 590.0E LANDFORM/DEPOSIT: Delta EVIDENCE: Topographic DESCRIPTION: Dissected flat plain fOrmed along Crockery Creek at a strong topographic break between hilly and flat terrain. 191 SITE #: 86 COUNTY: Musk./New. ELEV: 222m (730ft) 7.5'MIN. TOPO. QUADRANGLE(S): Bridgeton TOWNSHIP & SECTIONS: TlON R14W 1 and TllN R14W 36 UTM COORDINATES: 4792.0N 587.0E north to 4798.0N 587.0E LANDFORM/DEPOSIT: Linear sand ridges, topographic break, and radiocarbon. EVIDENCE: Topographic, field, sedimentologyr and radiocarbon. DESCRIPTION: Linear sand ridges along moraine for 2 miles, sharp topographic break. Sand in section 36 is clean sands and gravels. Longest ridge (2500 ft x 200 ft) was cored as clean sand with occasional silt and clay. This site is explained in greater detail in Section 4.2.4.3. The feature sits on top of peat over till. Wood from the peat has been dated at 11,440 +/- 170 B.P. SITE #: 87 COUNTY: Muskegon ELEVATION: 201m (660ft) 7.5 MIN. TOPO. QUADRANGLE(S): Dalton and Montague, TOWNSHIP & SECTIONS: Several UTM COORDINATES: Topographic break LANDFORM/DEPOSIT: Evenson 1 through 9, topographic EVIDENCE: Evenson 1 through 9, topographic DESCRIPTION: [Topographic contrast between flat plain and moraine]. SITE 9: 88 COUNTY: Muskegon ELEVATION: 201m (660ft) 7.5 MIN. TOPO. QUADRANGLE(S): Flower creek, Montague, and . Dalton TOWNSHIP & SECTIONS: T11n R17W 13 UTM COORDINATES: 4795.5N 557.5E LANDFORM/DEPOSIT: Topographic break and dunes EVIDENCE: Topographic DESCRIPTION: Topographic break along lakeward side of the Whitehall moraine. 192 SITE #: 89 COUNTY: Muskegon ELEVATION: 225m (740ft) 7.5 MIN. TOPO. QUADRANGLE(S): Holton TOWNSHIP & SECTIONS: Holton 26, 35, and 36 UTM COORDINATES: 4804.0N 576.0E LANDFORM/DEPOSIT: Topographic break, beach (?), and dune (?) EVIDENCE: Topographic and field DESCRIPTION: Topographic break with evidences of a ridge and. possibly other near-shore features covered with medium to very coarse sand. SITE 4: 90 COUNTY: MUskegon ELEVATION: 188m (620ft) 7.5 MIN. TOPO. QUADRANGLE(S): Montague TOWNSHIP & SECTIONS: Montague 20 UTM COORDINATES: 4807.0N 552.0E LANDFORM/DEPOSIT: Terrace EVIDENCE: Evenson 10 DESCRIPTION: Terrace with toe at 620’. SITE #: 91 COUNTY: MUskegon ELEVATION: 201m (660ft) 7.5 MIN. TOPO. QUADRANGLE(S): Flower Creek TOWNSHIP & SECTIONS: White River 2, 14, 19, 23, 24, 26, and 35 - UTM COORDINATES: 4807.0N 546.0E north to 4812.0N 546.8E LANDFORM/DEPOSIT: Topographic break EVIDENCE: Evenson 15-19 DESCRIPTION: [Topographic contrast between moraine and lake plain.] SITE 4: 92 COUNTY: MUskegon ELEVATION: 201m (660ft) 7.5 MIN. TOPO. QUADRANGLE(S): Montague TOWNSHIP & SECTIONS: Montague 20 UTM COORDINATES: 4807.3N 552.0E LANDFORM/DEPOSIT: Scarp EVIDENCE: Evenson 13 DESCRIPTION: Scarp SITE 4: 93 COUNTY: MUskegon ELEVATION: 200m (657ft) 7.5 MIN. TOPO. QUADRANGLE(S): Montague TOWNSHIP & SECTIONS: Montague 20 UTM COORDINATES: 4807.5N 552.0E LANDFORM/DEPOSIT: Beaches EVIDENCE: Evenson 11 DESCRIPTION: Beaches at 632, 634, 656, and 658. 193 SITE #: 94 COUNTY: Newaygo ELEVATION: 239m (785ft) 7.5 MIN. TOPO. QUADRANGLE(S): Hesperia, Holton, and Fremont TOWNSHIP & SECTIONS: Sheridan 2,3,4,5,11,12; Dayton 2,3,4,5; Garfield 7,8,17,20,2 UTM COORDINATES: 4809.0N 590.0E to 4811.0N 587.0E to 4815.0N 579.3E to 4818.0 577.7 . LANDFORM/DEPOSIT: Topographic break EVIDENCE: Topographic DESCRIPTION: Rough topographic break somewhat dissected. SITE #: 95 COUNTY: Muskegon ELEVATION: 2 02m (664ft) 7.5 MIN. TOPO. QUADRANGLE(S): Montague TOWNSHIP 8 SECTIONS: White River 13 UTM COORDINATES: 4810.0N 540.0E LANDFORM/DEPOSIT: Topographic break EVIDENCE: Evenson 14 DESCRIPTION: Topographic contrast between flat lake plain and rolling moraine. SITE #: 96 COUNTY: Newaygo ELEVATION: 231m (760ft) 7.5 MIN. TOPO. QUADRANGLE(S): Holton TOWNSHIP & SECTIONS: Holton 1, 11, and 12; Sheridan 5 and 6 UTM COORDINATES: 4811.0N 577.0E LANDFORM/DEPOSIT: Topographic break EVIDENCE: Topographic DESCRIPTION: Topographic break along till with evidence of a ridge. l SITE #: 97 COUNTY: MUskegon ELEVATION: 195m (642ft) 7.5 MIN. TOPO. QUADRANGLE(S): Montague TOWNSHIP & SECTIONS: Blue Lake 7 UTM COORDINATES:. 4812.0N 559.0E , ' LANDFORM/DEPOSIT: Terraces J EVIDENCE: Evenson 12 DESCRIPTION: Terraces on the White River. 194 SITE #: 98 COUNTY: MUskegon ELEVATION: 210m (690ft) 7.5 MIN. TOPO. QUADRANGLE(S): Flower Creek and Montague TOWNSHIP & SECTIONS: Montague 5 UTM COORDINATES: 4812.0N 551.0E _ LANDFORM/DEPOSIT: Topographic break EVIDENCE: Topographic DESCRIPTION: Strong topographic transition between flat and hilly terrain. SITE #: 99 COUNTY: Oceana ELEVATION: 211m (695ft) 7.5 MIN. TOPO. QUADRANGLE(S): Flower Creek and Town Corners TOWNSHIP & SECTIONS: Claybanks 13, 14, and 25; Grant 30 and 31 UTM COORDINATES: 4815.0N 549.7E northwest to 4820.0N 547.0E LANDFORM/DEPOSIT: Topographic break and beach EVIDENCE: Topographic and field DESCRIPTION: Strong topographic break along side of - moraine. MOraine has boulders and cobbles on surface up to at least 240m. SITE #: 100 COUNTY: Oceana ELEVATION: 213m (700ft) 7.5 MIN. TOPO. QUADRANGLE(S): Fowler Creek TOWNSHIP & SECTIONS: Claybanks 28 UTM-COORDINATES: 4816.0N 543.7E LANDFORM/DEPOSIT: Terrace EVIDENCE: Topographic and field DESCRIPTION: Terrace formed on side of moraine. Covered with sand and gravel. SITE #: 101 COUNTY: Oceana ELEVATION: 207m (680ft) 7.5 MIN. TOPO. QUADRANGLE(S): Ferry TOWNSHIP & SECTIONS: 21 and 22 UTM COORDINATES: 4817.0N 563.5E LANDFORM/DEPOSIT: Spit (?) EVIDENCE: Topographic DESCRIPTION: Large spit shaped topographic feature. 195 SITE 4: 102 COUNTY: Oceana ELEVATIONZlOm (690ft) 7.5 MIN. TOPO. QUADRANGLE(S): Town Corners TOWNSHIP & SECTIONS: UTM COORDINATES: LANDFORM/DEPOSIT: EVIDENCE: DESCRIPTION: Claybanks 21 4817.7N 542.2E Lacustrine sediments exposed in bluff along Lake Michigan Field and sedimentology Second exposed along Lake Michigan shore shows lacustrines (flatly bedded sands) up to an elevation of at least 210m. An idealized cross section would show two tills separated by a thick fining upward sequence (from washed cobbles to laminated siltsand clays). The bottom till is red and like the fining upward. sequence is over compacted. The upper till is gray and not as coarse as the lower till. Above the gray till are lacustrine sands overlain by dune sands. The entire section is approximately 150m thick, and the lacustrines are found at approximately 205 to 215m in elevation. SITE #: 103 COUNTY: Oceana ELEVATION: 222m (730ft) 7.5 MIN. TOPO. QUADRANGLE(S): Town Corners TOWNSHIP & SECTIONS: UTM COORDINATES: Claybanks 14, 15, 22, and 23 .4818.0N 545.5E LANDFORM/DEPOSIT: Topographic break EVIDENCE: Topographic and field DESCRIPTION: At turn in Wilke Road there is sand with pebbles and a visible topographic break. SITE #: 104 COUNTY: Oceana ELEVATION: 220m (725ft) 7.5 MIN. TOPO. QUADRANGLE(S): Shelby and Ferry TOWNSHIP & SECTIONS: UTM COORDINATES: LANDFORM/DEPOSIT: EVIDENCE: DESCRIPTION: Grant 13, 14, and 15; Otto 16 and 17 4019.0N 555.0E Topographic break Topographic and field Strong topographic break with sand, pebbles, and cobbles. 196 SITE #: 105 COUNTY: Oceana ELEVATION: 220m (725ft) 7.5 MIN. TOPO. QUADRANGLE(S): Town Corners and Shelby TOWNSHIP & SECTIONS: Grant 8, 9, 10, 15, 16, and 17 UTM COORDINATES: 4819.5N 552.2E LANDFORM/DEPOSIT: Topographic break and terraces EVIDENCE: Topographic and field DESCRIPTION: Along Cleveland road a sand and gravel , ridge on side of_a kame (?). SITE #: 106 COUNTY: Oceana ELEVATION: 192m (630ft) 7.5 MIN. TOPO. QUADRANGLE(S): Town Corners TOWNSHIP & SECTIONS: Claybanks 8 and 17 UTM COORDINATES: 4820.0N 541.5E LANDFORM/DEPOSIT: Beach and dune EVIDENCE: Evenson 1 DESCRIPTION: 5' dune sand over 2' coarse beach gravel over red clay till. SITE 4: 107 COUNTY: Oceana ELEVATION: 201m (660ft) 7.5 MIN. TOPO. QUADRANGLE(S): Town Corners TOWNSHIP & SECTIONS: Claybanks 4 and 9 UTM COORDINATES: 4821.0N 543.0E LANDFORM/DEPOSIT: Cut Cliff EVIDENCE: Evenson 2 DESCRIPTION: Cut cliff 1 mile in length trending NE-SW. SITE #: 108 COUNTY: Oceana ELEVATION: 225m (740ft) 7.5 MIN. TOPO. QUADRANGLE(S): Hesperia TOWNSHIP & SECTIONS: Greenwood 3, 4, 5, 8, 9, and 10; Newfield 32, 33, and 34 UTM COORDINATES: 4822.0N 573.0E LANDFORM/DEPOSIT: Delta EVIDENCE: Topographic, spatial location, field, and sedimentology. DESCRIPTION: Flat area at the mouth of an outwash plain bordered by topographic breaks. Littered with shallow gravel pits dominated by sands and gravels. NW/4 of section 10 (Greenwood Twsp) White River exhibits lacustrine clays up to 670' elevation. Clays are clean (very little silt with no observed drop stones) and not highly compacted. These are interpreted as bottom set beds in a deltaic sequence. 197 SITE #: 109 COUNTY: Oceana ELEVATION: 217m (715ft) 7.5 MIN. TOPO. QUADRANGLE(S): Ferry TOWNSHIP & SECTIONS: Otto 1; Ferry 35 and 36 UTM COORDINATES: 4822.2N 567.0E LANDFORM/DEPOSIT: Topographic break and terraces EVIDENCE: Topographic DESCRIPTION: Well defined topographic break. SITE #: 110 COUNTY: Oceana ELEVATION: 225m (740ft) 7.5 MIN. TOPO. QUADRANGLE(S): Ferry and Hesperia TOWNSHIP & SECTIONS: Newfield 32, 33, 34, and 35 UTM COORDINATES: 4824.0N 572.0E LANDFORM/DEPOSIT: Ridge and scarp EVIDENCE: Topographic DESCRIPTION: Two terraces formed one at 225m and one at 240m. SITE 4: 111 COUNTY: Oceana ELEVATION: 201m (660ft) 7.5 MIN. TOPO. QUADRANGLE(S): Town Corners TOWNSHIP & SECTIONS: Benona 32 UTM COORDINATES: 4824.4N 540.4E LANDFORM/DEPOSIT: Wave Cut Terrace EVIDENCE: Evenson 5 DESCRIPTION: Wave cut terrace Ibounded. by cliff. Base of cliff is armored with large boulders, terrace has thin veneer of sand and gravel. SITE #: 112 COUNTY: Oceana ELEVATION: 198m (650ft) 7.5 MIN. TOPO. QUADRANGLE(S): Town Corners TOWNSHIP & SECTIONS: Benona UTM COORDINATES: 4824.5N 547.0E LANDFORM/DEPOSIT: Delta EVIDENCE: Evenson 3 DESCRIPTION: River cut displays 30 to 40 feet cross bedded deltaic gravels over red till. SITE #: 113 COUNTY: Oceana ELEVATION: 202m (663ft) 7.5 MIN. TOPO. QUADRANGLE(S): Town Corners TOWNSHIP & SECTIONS: Benona 26 UTM COORDINATES: 4825.0N 546.3E LANDFORM/DEPOSIT: Delta EVIDENCE: Evenson 4 and 6 DESCRIPTION: Large cut on Stony Creek exposes fluvial and deltaic sands and gravels over red till. Red till comes to surface 1/4 mile to the north. 198 SITE #: 114 COUNTY: Oceana ELEVATION: 240m (790ft) 7.5 MIN. TOPO. QUADRANGLE(S): Hesperia TOWNSHIP & SECTIONS: 21, 26, 27, and 28 UTM COORDINATES: 4826.0N 573.0E LANDFORM/DEPOSIT: Topographic break EVIDENCE: Topographic DESCRIPTION: Second terrace described in previous entry. SITE #: 115 COUNTY: Oceana ELEVATION: 201m (660ft) 7.5 MIN. TOPO. QUADRANGLE(S): Mears and Little Point Sable TOWNSHIP & SECTIONS: Golden 31 UTM COORDINATES: 4833.0N 539.5E east to 4833.5N 542.0E LANDFORM/DEPOSIT: Beach (?) EVIDENCE: Evenson 7, 8, and 9 DESCRIPTION: Washed sand and gravel over red till . at break in slope; beach (?). SITE #: 116 COUNTY: Oceana ELEVATION: 188m (620ft) 7.5 MIN. TOPO. QUADRANGLE(S): Little Point Sable, and Mears TOWNSHIP & SECTIONS: Golden 31 UTM COORDINATES: 4833.7N 539.5E LANDFORM/DEPOSIT: Scarp EVIDENCE: Evenson 10 DESCRIPTION: Wave washed flat at 620' bounded by small scarp. LIST 05' REFERENCES LIST 0? REFERENCES Andrews, J. T. (1974), ‘glagial__lsgataay, Hutchinson and Ross, Inc. Dowden, Stroudsburg, PA. Andrews, J.T., 1970, Present and postglacial rates of uplift for glaciated northern and eastern North America derived from post glacial uplift curves: Qanafiiaa 12urnal.9fi.§arth_§cisnges_xil. Berger, G. W. (1985). Thermoluminescence dating applied to a thin winter varve of the late glacial South Thompson silt, south-central British Columbia. Canadial_ggurna1 Qf_Eé£Lh_§£l§££§§_!_ZZL_D_ll3 1736-1739. Black,. R. F. (1974). Late pleistocene shorelines and stratigraphic relatins in the Lake Michigan basin: Discussion. 9s2logical_Socistx_2£_America_Bullstin_§§: 659-660. Black R. F. (1980) 'Valders--Two Creeks, ‘Wisconsin, revisited: The Valders Till is most likely post- Twocreeken. 9:919gica1_Socistx_2£_Amsrica_aulletini_21. 713-723. Boulten, G.S., G.D. Smith, A.S. Jones, and J. Newsome (1985) Glacial geology and glaciology of the last mid-latitude ice sheets, J2urnal__2i__ths__fisologisal__§9§istx__gfi Londoni_152, 447-474- Bretz, J. H. (1964). Correlations of glacial lake stages in the Huron-Erie and Michigan basins. figurnal_gfi_§aglggy 75; 618-627. Cathles. LM. 1975 Tbs—1W. Princeton: Princeton University Press. Clark, R. H. and N. P. Persoage (1970). Some implications of crustal movement in engineering planning. Canadian 1Qurnal_ofi_nartb_§§ien§es_l: 628:633. Clark, J.A. (1976). Greenland’s rapid postglacial emergence: a result of ice water gravitational ‘ attraction. fiaglggy_5a 310-312. 100 200 Clark, J. A., W. E. Farrell, and W. R. Peltier (1978). ‘ Global changes in postglacial sea level: A numerical Calculation. Quaternar1_3esearch_2i 265-287. Clark, J.A. and A. L. Bloom (1979) . Hydro-isostasy and Holocene emergence of South America. 1228 9 ‘ 9-. 00-. 1 00 m 0 _v-, 'n __l 1‘ Quatsrnarxi_§ag_£aulgi_Brasili 41-60. Clark, J. A. and C. S. Lingle (1979). Predicted relative sea-level changes (18,000 years B.P. to present) caused by late-glacial retreat of the Antarctic ice sheet. Quaternarx_3sssarch_lli 279-298. Clark, J. A. (1980). The reconstruction of the Laurentide ice sheet of North America from sea level data: Method and preliminary results. gnurnal__gf__§e22hxsical Bessarch.fl§i 4307-4323- Clark, J. A., H. S. Pranger, J. A. Primus, and J. K. Walsh (1985). A model of proglacial lake strandline delevelling during the past 18, 000 years: Stratigraphic Implications. w v 17. n 5: 283. Clark, J. A. (1985). Forward and inverse models in sea- level studies, in Models__in__§s2mor2hglosx. J. M- Woldenberg editor, Allen and Unwin, Boston: 119-138. Clark, J. A., H. S. Parnger II, J. K. Walsh, an J. A. Primus (1986). A numerical model of Glacial Isostasy, in Ina Laka__Mighigan__Baain, GSA. publication ed. .Allan F. Schneider: (submitted) Clark, J. A. and J. A. Primus (1987). Sea level changes resulting from future retreat of ice sheets: an effect of CO warming of the climate. MW, edited, by Tooley, M. J. and Shenvan, I. Basil Blackwell, Publishers, Institute of British Geographers Special Publications, 356-370. Clark, J. A., (Per. Comm.) Analysis of basal peats in Kettles at and above 201m in Muskegon County. Calvin College, Grand Rapids, MI. ' Coordinating Committee of Basic Hydraulic and Hydrologic Data, (1977) . Apparent vertical movement over the Great Lakes. Detroit District, United States Army Corps of Engineers, Detroit, MI, 70 p. Denton, G. H. and T. J. Hughes, ed (1981). W W. John Wiley and Sons, New York: insert. 201 Dorr, J. A. and D. P. Eschman, (1970). fiaalggy_gf_Miahigaa. Ann Arbor: University of Michigan Press. England, J., (1976) Late Quaternary glaciation of the Eastern Queen Elizabeth Islands , N . W . T . Canada: Alternative models, Qaa;araary_Raaa, 185-202, 1976b. Eschman, D. F. and W. R. Farrand (1970). filagial_fliatgry_afi W. In the Guidebook for field trips, North-Central Section Geological Society of America Meeting: 131-157. Eschman, D.F., and P.E. Karrow, (1985) Huron Basin Glacial Lakes: A Review: in Karrow, P.E., and P.E. Calkin, eds. v : Geological Association of Canada special paper 30. Evenson: E- B. (1972). WW 0 -° - 0! 1 0‘ h . ‘ M _°-_! .9-‘ . ' University of Michigan, Ph. D. Dissertation. Evenson, E. B. (1973), Lake Pleistocene shorelines and stratigraphic relations in the Lake Michigan basin. Geological_Societ2_of_America_Bulletin_fiii 2281-2298. Evenson, E. B., W. R. Farrand, D. F. Eschman, D. M. . Mickelson, and L. J. Maher (1976). Greatlakean substage - a replacement for Valderan substage in the Lake Michigan Basin. Quaternarx_fissearch_xiii 411-424. Farrell W. E. and J. A. Clark (1976). On postglacial sea level. Geophst_QI_Bi_asrri_§oci_A§i 647-667. Farrand, W. R., and D. L. Bell (1982). Quaternary Geology of Southern Michigan (map of) . , Ann Arbor Michigan. Farrand, W.R., and C.W. Drexler, (1985). Late Wisconsin and Holocene History of the Lake Superior Basin: in Karrow, P F. and P E Calkin, eds. Quaternar2_fizolution_of_the m: Geological Association of Canada special paper 30. Flint,'R. F., R. B. Colton, R. P. Goldthwait, and H. B. Willman (1959). Glacial Map of the United States east of the Rocky Mountains, published by W Societx_of_America. Futyma, R. P. (1981). The Northern Limits of Glacial Lake Algonquin in Upper Michigan. Quaternar2_Besearch_zil§i 291-310. 202 Gephart, G. D. and G. J. Larson (1982). ‘ Surficial Geology of Allegan County. Michigan. W 53:13.3: Michigan Dept. of Natural Resources Geological Gilbert, G.K., 1898 Recent Movements in the Great Lakes region: W p. 601- 647. Goldthwait, J. W. (1906). Correlation of the raised beaches on the west side of Lake Michigan. W 14; 411- 424 Goldthwait, J.W. (1907). Abandoned shorlines of Eastern Wisconsin . W W. . Goldthwait, J.W. (1908). A reconstruction of water planes of the extinct glacial lakes in the Lake Michigan Basin. W1: 459-476. Goldthwait, J.W. (1910). Isobases of the Algonquin and Iroquis Beaches and their significance. W1: 227-248. Gutschick, R.C. and J. Gonsiewski (1976). Coastal Geology of the Mt. Baldy Area, Indiana Dunes National Lakeshore, South End of Lake Michigan: in W .1V0n ‘ ,v__° ‘010’3 1° 0 v. 1 “11‘ M hi'o! WM, Geological Society of Anerica, North Central Section. November 1, 1976, pp. 45- -90. Grant, D. R. (1977) Glacial style and ice limits, the . Quarternary stratigraphic record, and changes of land and ocean level in the Atlantic Provinces, Canada, W. 3.1. 247-260. Hansel, A. K. , C. E . Larsen, and A. F . Schneider (1985a) . High lake phases in the Lake Michigan basin . 0° _‘ 0., 1111‘, _ -. \0 1" ‘ 1 -. ‘, '1 m 292. Hansel, A.K., Mickelson, D.M., Schneider, A.F., Larsen C.E., (1985b). Late Wisconsinan and Early Holocene History of the Lake Michigan Basin: in Karrow, P.E., and Calkin P.E.. eds” WW: Geological Association of Canada Special Paper 30. Hansel, A.K., and D.M. Mickelson (1988). A re-evaluation of the timing and causes of high lake phases in the Lake Michigan basin. W, V. 29, p. 113- 128. 203 Hendriks, M., J.P. Icenhower, C.N. Struck, J-A. Clark, and J.Am Groen (1988). Effects of different ice-sheet histories and earth rheologies on glacio- -isostatic tilt of glacial lake shorelines in the Lake Michigan basin. 0 0° -. -0 ‘ 0_ 1- ._ 1.0 r._ 1 ° 0' v.11 L_2_0_n.._§ Hough. J. L. (1958). MW. Urbana: University of Illinois Press. Hough, J.L. (1966). Correlation of glacial lake stages in the Huron Erie and Michigan Basins. Qaaraal_gfi_§aglggy 11: 62-77 Hughes, T. J. Denton, G. H., Andersen, B.G., Schilling, D. H., Fastook, J. L., and Lingle, C.S. (1981) the last great ice sheets: a global view, in Ih§_L§§§_§;§§L_IQ§ m, ed. by Denton, G.H., and Hughes, T.J., John Wiley and Sons, New York, 263-317. Karrow, P. F., J. R. Clark, and J. Terasmae (1961). The age of Lake Iroquois and Lake Ontario. Jgarnal_gf_§aglggy ‘62; 659-667 Karrow, P. F., A. H. Clarke, and H. B. Herrington (1972). Pleistocene Molluscs from Lake Iroquois deposits in Ontario. W 589-595 Karrow, P. F. (1980). The Nipissing transgression around northern Lake Huron. 7Qanadian__lonrnal__of__fiarth W 1271-1274 Karrow, P. F. and P. E. Calkins, eds. (1985) W BMW: Geological Association of Canada Special Paper 30. Kaszycki, C.A. (1985) History of Glacial Lake Algonquin in the Haliburton Region, South Central, Ontario: in Karrow, P.E., and Calkin P.E., eds., Quarternary BMW: Geological Association of - Canada Special Paper 30. Larsen C. E. (1985a). Lake level, uplift and outlet incision, in the Nipissing and Algoma Great Lakes. In P. F. Karrow and P. E. Calkin eds., Quatarnary , Geological Association of Canada Special Paper. . Larsen, C.E. (1985b). Glacio-isostasy -- an alternative to the Ihinge-line model in the southern Lake .Michigan basin. WM 298. 204 Larsen, C.E., (1987) Geological History of Glacial Lake Algonquin and the Upper Great Lakes. W W Leverett, F. and F. B. Taylor, (1915). 111W 11,21- 11°. 9 1 °-1 v.10- ! 0 0- ‘ -‘-_ Lam. U . S . Geological Survey Monograph 53 , Washington. MacLean. w.F.. WWW Ann Arbor, MI. Martin, H. M. (1955). Map of Surface Formations of the Southern Peninsula of Michigan. n W Publication 49 . Mayewski, P. A., G. H. Denton, and T. J. Hughes (1981). Late Wisconsin Ice Sheets of North America, in Denton, 6- H. and '1‘. J. Hughes eds. W. John Wiley and Sons, New York: 67-178, insert. Michelson, D.M., Clayton, L., Fullerton, D.S., and Burns, H.W. (1983) The Late Wisconsin glacial record of the Laurentide ice sheet in the United States, in Laaa WWW. Volume I. W, ed. by Porter, S.C., University of Minnesota Press, Minneapolis, 3-37. Miller N. G. and W. S. Benninghoff (1969). Plant fossils from a Cary-Port Huron interstate deposit and their paleoecoological interpretation. WW ' W 225-248. Miller, N. G. (1973). Pollen analysis of deeply buried Quarternary sediments from southern Michigan. Ana]; W25. 217-223. Moore, 8., 1922 Tilt of the earth in the Great Lakes region: Military Engineer, u. 14. Paterson, W.S.B., Laurentide ice sheet: Estimated volumes during the Late Wisconsin. W. 10, 885-917, 1972. Paterson, W.S.B., Extent of the Late Wisconsin glaciation in Northwest Greenland and Northern Ellesmere Island: A review of the glaciological and geological evidence, ‘ WI 3.! 180-190- Peltier, W.R. (1974) The impulse response of a Maxwell Earth. MW. 12.. 649-705. 205 Peltier, W.R. and .Andrews, J.T. (1976) Glacio-Isostatic Adjustment - I. The Forward Problem, MILL—.1131 W! I). 605-646- Peltier, W.R. 1980. Ice Sheets, oceans and the earth's shape. In .Earth__BhsologxI__Isostasxi__and__flustasx. Norner, N.A. (ed.), 45-63 - New York: Wiley Peltier, W.R. (1984). The Thickness of the Continental , Lithosphere. Qournal__of..§eophxsical__§sarc_, 89. p. 11303-11316. Prest. V.K. (1969) Retreat of Wisconsin and recent ice in North America, Geological Survey of Canada Map 1257A. Spencer, J. W. (1891). Deformation of the Algonquin Beach, and Birth of Lake Huron. Seriss_31 12-21. Stanley, G. M. (1936). Lower Algonquin beaches of Penetanquishene Peninsula. Gaalggigal__§ggiaty__gf Amsrica.§ulletin_lli 1933-1960. Stanley, G.M. (1937). Lower Algonquin beaches of Cape Rich, Georgian Bay. 55; 1665-1686. Tague, G.C., (1942) The post-glacial geology of the Grand Marais Embayment, Berrien County, Michigan in D O O -‘ 09- .0: ‘ ‘0 o. 1" ‘0 oo o o. . State of Michigan Geological Survey Division Pub. 45, _ Geological Series 38. p. 1- -81. Taylor, L. D. (1985). Geomorphic and stratigraphic evidence for glacial lake levels in the northeastern Lake Michigan basin and their relationship to pulift curves. 0 0' 0 in - 10 -_ W 1 " 111_n_§i 329. Terwilliger, F. W. (1954). The glacial geology and groundwater resources of Van Beuren County, Michigan. Geoli_Snrxi_Di_I_DsptI_of_§onserxationi_£ubi_iflr 9- -95. Thompson, T. A. (1985). Late Pleistocene lacustrine sediments of the Cowles bog area, Indiana Dunes National Lakeshore. Ahstracts_zithizrograms_x_1li_n_fii.329. Timmermans, T. J., T. S. Hooyer, J. A. Groen, and J. A. Clark, (1986). A model of Shoreline Tilting in the Lake Huron, Northern Lake Michigan, and Lake Superior Basins. Programs_x_1§r_n_ii 328. 0° {11‘ 206 Timmermans, T. J., (1988) A. high Calumet shoreline in Southwestern Michigan as an indicator of Isostatic Rebound in that region. W v.20 n.5 USDA Soil Conservation Service (1968) §Qi1 Sarvay 9f Ottawa anntya__ui§higaa. US Government Printing Office, ’ Washington D.C. USDA Soil Conservation Service (1972) $911 Sarggy at W. US Government Printing Office, Washington D.C. Vitorello, I. and R. VAn Der V00 (1977). Magnetic stratigraphy of Lake Michigan sediments obtained from cores of lacustrine clay. Qaatarnary_3a§aargh_la 398- .412 Walcott, R. I. (1970). Isostatic response to loading of the crust in Canada. WWI; 716-727. Walcott, R. I. (1972). Late Quarternary vertical movements in Eastern North .America: Quantitative evidence of glacio-isostatic rebound. W W 849-884. Wolf, D (1985). On deglaciation-induced perturbations of the geoid. WWW. pp- 269-272. Woodward, R.S. (1888) On the form and position of mean sea level. W. 5.8. 87-170. Wu, P. and W.R. Peltier (1982). Viscous gratitational relaxation. Geophysical Journal a: tha Bgya]. WW. pp. 435-485. Wu, P. and Peltier, W.R. (1983) Glacial isostatic adjustment and the free air gravity anomaly as a constraint on deep mantle viscosity, Gagphys. J,R,QA§;;. 5329., LIA, 377-449.