448 CROSS AND HOWE — RED BEDS OF SOUTHWESTERN COLORADO 



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The Zuni plateau, New Mexico 477 



Northeastern Arizona 480 



The Plateau section of southern Utah 482 



Sections of other investigators 482 



Divisions established by Powell 482 



Observations by C. D. Walcott 483 



Comment on Walcott's Kanab section 486 



Northeastern Utah and northwestern Colorado 487 



Correlations within the Rocky Mountain province 488 



Difficulties of the correlation 488 



Fossiliferous Trias on Red Dirt creek 488 



Triassic beds of central Wyoming. 489 



Permian Red beds of the Laramie basin 489 



" Permian " beds of the Grand and Eagle rivers, Colorado 490 



Foothill section of the Front range. 490 



Triassic beds of northern New Mexico 494 



Summary 495 



List of publications cited 496 



Part I. The Red Beds of Southwestern Colorado 



INTRODUCTION 



The strata of reddish color, in varying tints and shades, often referred 

 to as the " Red beds," constitute one of the most striking terranes in the 

 sedimentary section of the Rocky Mountain province. Consisting in the 

 main of sandstones and conglomerates, beds of other character, such as 

 shale, limestone, gypsum, etcetera, are more or less prominent in many 

 localities. While the complex in question is one of wide distribution 

 and has been examined and described by many geologists, it is still very 

 imperfectly known as to its age and the correlation of the sections of 

 different areas. The rarity or absence of fossils, the varying vertical 

 extent of the red color, and the common lack of stratigraphic evidence 

 suggesting division planes combine to make a satisfactory analysis of 

 the Red beds difficult. 



Where the complex in question has what may be called its normal 

 development it is 2,000 feet or more in thickness. It occurs in numer- 

 ous districts between known Carboniferous and Jurassic beds character- 

 ized by fossils. This general stratigraphic position and the lithologic 

 similarity to the Triassic beds of the Atlantic slope has led to the pre- 

 vailing reference of the Red beds to the Trias. This reference was early 

 shown to be correct in certain regions and for certain strata by the dis- 

 covery of Triassic fossils, while in other places Carboniferous fossils 

 have shown that the color distinction is not a safe guide, and that some 

 portions at least of the Rocky Mountain Red beds belong to Permian 



