Contents 



PAGE 



Introduction 3 



Location, Extent, and Name of the ''American Bottoms" 5 



Drainage and Topography 6 



The Geology of the ''American Bottoms" Region and the Topographic 



and Physiographic Influences of the Lithologic Units 7 



The Mississippian Strata 8 



The Mitchell Limestone 8 



The Sample Sandstone and Horizon 9 



The Beaver Bend Limestone 9 



The Brandy Run Sandstone Horizon. .• 10 



The Reelsville Limestone 10 



The El wren Sandstone and Shale 11 



The Beech Creek Limestone 11 



The Cypress Sandstone 16 



The Golconda Limestone and Shale 18 



The Pennsylvanian Strata 19 



The Mansfield Sandstone " 19 



The Pre-Glacial Physiographic History of the Region 21 



The Significance of Land Forms . 21 



The Kirksville Peneplain . 22 



The Partial Erosion Cycle Succeeding the Kirksville Peneplain 23 



Further Uplift and Stream Trenching 26 



Valley Filling 26 



Valley Filling Interpreted as a Result of Regional Depression. ... 27 

 Valley Filling Interpreted as a Result of the Seaward Extension 



of the Master Stream 29 



General View of the Topography and Relief Before the Advent of 



the Illinois Glacial Lobe 34 



Summary of the Pre-Glacial Physiographic Development 35 



The Physiographic Influence of the Illinois Glacial Lobe 36 



General Obstruction in Front of the Illinois Glacial Lobe 36 



Stream Damming in the "American Bottoms" Region 37 



Post-Glacial Physiographic Work and Readjustment 40 



Removal of the Pleistocene Deposits 40 



Development of the Post-Glacial Clifty Creek 43 



Development of the "American Bottoms" Drainage 45 



The "American Bottoms" Basin Specially Preserved ■ 57 



Summary 58 



(2) 



