CONTENTS. 



Chaptbb I. Introduction 5 



Contents 5 



Arrangement of material 6 



Geologic divisions mapped 7 



Acknowledgments 20 



Color scheme 21 



Principles 21 



Usages 23 



Principles for coloring geologic maps 27 



Contributors 30 



Chapter II. Pre-Cambrian 62 



Chaptee III. Cambrian and lower Ordovician , 72 



Chapter IV. Middle and upper Ordovician 156 



Chapter V. Silurian 225 



Chapter VI. Devonian 269 



Chapter VII. Paleozoic undivided 342 



Chapter VIII. Carboniferous undivided 355 



Chapter IX. Mississippian 401 



Chapter X. Pennsylvanian 425 



Chapter XI. Permian 474 



Chapter XII. Triassic ; . . 500 



Chapter XIII. Jurassic 549 



Chapter XIV. Lower Cretaceous 579 



Chapter XV. Upper Cretaceous 637 



Chapter XVI. Earlier Tertiary (Eocene and Oligocene) 706 



Chapter XVII. Later Tertiary (Miocene and Pliocene) 794 



Chapter XVIII. Bibliography 840 



Index 867 



ILLUSTRATIONS. 



Page. 



Plate I. Geologic map of North America In box 



Figure 1 . Sketch map showing the distribution of post-Cambrian intrusive rocks represented on the geologic map 



of North America . , . 18 



2. Sketch map showing the distribution of Tertiary and later effusive rocks represented on the geologic 



map of North America 19 



3. Sketch map showing the distribution of pre-Cambrian rocks represented on the geologic map of 



North America and the key to references in the text 63 



4. Classification of the pre-Cambrian adopted by the International Committee 67 



5. Sketch map showing the distribution of Cambrian and lower Ordo-vician rocks represented on the 



geologic map of North America and the key to references in the text 73 



6. Sketch map showing the distribution of middle and upper Ordovician rocks represented on the 



geologic map of North America and the key to references in the text 157 



7. Sketch map showing the distribution of Silurian rocks represented on the geologic map of North 



America and the key to references in the text 226 



8. Sketch map showing the distribution of Devonian rocks represented on the geologic map of North 



America and the key to references in the text 270 



9. Sketch map showing the distribution of Paleozoic rocks that are undivided on the geologic map of 



North America and the key to the references in the text 343 



3 



