VII [ CONTEXTS. 



Page. 



Chapter X. — The late Wisconsin drift sheets 317 



liasis for separation from the early Wisconsin 317 



Outline of the late Wisconsin border 318 



Section I. The Minooka till ridge 319 



Distribution -- 319 



Probable line of continuation 319 



Relief 320 



ThickneBsof drift 320 



Structure of drift 321 



Character of the outwash 321 



Inner-border till plain 324 



Section II. Bowlder belts 325 



Section III. Lake Kankakee 328 



Extent of the sand . 329 



Range in altitude of the border of the sand _ 331 



Surface contours 332 



Thickness of the sand 333 



Variations in coarseness 333 



Interpretations - 334 



Section IV. The Valparaiso moiainic system 339 



Distribution - 339 



Border between the Lake Michigan and Saginaw Bay lobes 340 



Range in altitude 343 



Surface contours 345 



Detailed description of the Michigan portion 348 



Thickness of the drift - 353 



Structure of the drift 356 



Character of the outwash 375 



Section V. The lake-border morainic system 380 



Till ridges of Lake and Cook counties, Illinois 380 



The outer or west ridge 380 



The middle ridge - 381 



The east ridge .« 381 



Probable continuations 382 



Relief - - -- 384 



Thickness of drift 384 



Structure of drift 385 



Till ridges on the southeast border of Lake Michigan 386 



The outer ridge 386 



Covert Ridge - 388 



Zeeland Ridge 390 



Relief 391 



Range in altitude 391 



Thickness of drift - 392 



Structure of drift - - 393 



Character of the outwash 403 



Associated till plains 404 



Altitude and slopes 404 



Thickness of drift 406 



Structure of drift 407 



Section VI. Stria' within limits of Shelbyville moraine 412 



Chapter XI. — The Chicago Outlet and beaches of Lake Chicago 418 



Previous writers 418 



The Chicago Outlet 420 



The glacial Lake Chicago 427 



Upper, or Glen wood, beach 428 



