CONTKNTS. ix 



Chapter V. — tgneouB formations, by Whitman Cross — < lonl inued. 

 Section 1. — Geological occurrence — Continued. 



Aiigite-syenite 29G 



Quartz-porphyry 297 



Sen ion [I.— Petrographical description 297 



Introductory remarks 297 



Iiasalt 297 



Basalt of the Valmont dike 298 



BasftH of the Ralston dike and the adjacent masses 302 



Table Mountain Iiasalt ; capping sheets 304 



Table Mountain Iiasalt : earliest lavas! 307 



Augite-mica-syenite 308 



Rocks of the Denver formation :il I 



Volcanic tuff ;:i 1 



The typical t uff :;12 



Tuffaceous beds in general 314 



Andesitic pebbles of conglomerates 315 



Chapter VI. — Economic geology, by George H. Eldridge.. :;17 



Section I. — Coal :!17 



Development of the basin :;i7 



List of mines 320 



Geological occurrence of the coal 323 



Coal areas 325 



Introduction 325 



Foothill area 326 



Extent ;iu6 



Productive localities 327 



Strikes and dips 328 



Sedalia district 329 



Sedalia district to Mount ( larbon 329 



Mount Carbon district 329 



Mount Carbon to Golden 331 



( tolden district 333 



Ralston Creek district 337 



Ralston Creek to Marshall 33g 



Boulder coal Held ;i;j<) 



] >avidson syncline ,",.;i> 



The Marshall district 345 



The Allen-Bond district 350 



The Davidson district :;;,! 



Kggleston syncline 352 



Coal Creek syncline 353 



Structure 353 



Stratigraphy and correlation 359 



Available coal area ;;tc r ; 



The Superior district 364 



The Louisville district 364 



The Lafayette district 365 



