CONTENTS. Vll 



Chapter III.— Geologic formations underlying the pript — Continued. Page. 



Sources of the Cretaceous deposits 101 



Denudation of the Cretaceous area 102 



Erosion of the plains to a haselevel 102 



Later erosion of the trough of Lake Agassiz 104 



Chapter IV.— The Glacial period and it.s drift deposits 108 



Review of the Glacial period in North America 108 



The continental ice-sheet HO 



Boundaries HO 



Area and thickness 112 



Laurentide and Cordilleran centers of outflow 119 



Junction of the Laurentide and Cordilleran drift 120 



Comparison with the present ice-sheet of Greenland 123 



Recession of the ice-sheet 126 



Latest glaciation far north 128 



Glacial currents within the basin of Lake Agassiz 129 



Table of courses of glacial striie 129 



Converging lobes of the ice-sheet in Minnesota and Manitoba 129 



Transportation of bowlders 130 



Drift deposits on the lacustrine area and the adjoining region 132 



Derivation of the drift from preglacial residuary detritus and fioni glacial erosion. 132 



Thickness of the drift 133 



Till or bowlder-clay 134 



Bowlders and gravel from Archean and Paleozoic formations 13fi 



Northeastern limit of limestone drift 137 



Localities of very abundant and large bowlders 137 



Terminal moraines 139 



Earlier moraines formed before the beginning of Lake Agassiz 141 



Sixth or Waconia moraine 112 



Moraines contemporanovis with Lake Agassiz 146 



Seventh or Dovrc moraine 117 



Eighth or Fergus Falls moraine 158 



Ninth or Leaf Hills moraine 163 



Tenth or Itasca moraine 173 



Eleventh or Mesabi moraine 177 



Modified or assorted drift 179 



Belt of modified drift between St. Paul and Winnipeg 181 



Birds Hill and other eskers in Manitoba 183 



Proportion of modified dri ft supplied to the deltas of Lake Agassiz 189 



Influence of adjoining lakes or the sea on the deposition of the drift 190 



Chapter V. — History of Lake Agassiz 192 



Two classes of Pleistocene lakes 192 



Lakes Bonneville, Lahontan, and others in the Great Basin _192 



Lake Agassiz and other glacial lakes 194 



Evidences of glacial lakes ' 1™ 



Outlets 195 



Eroded clifl's 198 



