CHAOTIC BRECCIA. 223 



River and Miller Creek and the central portion of Crandall Basin. To one 

 who has spent much time among- the well-bedded breccias of Two Ocean 

 Plateau and of the greater portion of the Absaroka Range, nothing could 

 be more noticeable than the difference of structure exhibited by the breccias 

 in the locality just mentioned. It is to be remarked, however, that while 

 this difference is so noticeable in extreme cases, there is no sharp line to be 

 drawn between the different areas in the field, and from the nature of their 

 origin they often merge into one another. 



The most typical exposure of chaotic breccia has become well known 

 for the grotesqueness of the shapes assumed by the rock when cut by 

 erosion into pinnacles and buttresses. The heterogeneous agglomeration of 

 scoria and tuffs with angular masses of various sizes has been carved into 

 turrets of the most irregular and remarkable shapes, whose dark color and 

 forbidding aspect suggest to a fanciful imagination goblins and demons, 

 popularly termed "hoodoos." 



The Hoodoo Basin, at the southern base of the mountain of the same 

 name, is the best example of this form of erosion. Other occurrences of 

 this character are found in various localities in the district. Some of the 

 grotesque pinnacles are shown in PI. XXX, from a photograph taken by 

 Mr. Weed. The rocks, though dark chocolate-brown as a whole, often 

 appear on closer examination to be brilliantly colored and varieg-ated, 

 ranging from brick red to purple and pink, and being in places bluish and 

 greenish, and also yellow and brown. These colors are characteristic ol 

 the chaotic breccias in a number of localities; as, for example, on the 

 eastern slope of Parker Peak, on the divide between Miller and Papoose 

 creeks, and on that east of the head of Lamar River. There is a noticeable 

 increase in the number of large masses of rock occurring as fragments in 

 the breccia, which often exceed a diameter of 8 feet, some being 20 or 

 more feet thick. The petrographical character of the rocks forming large 

 areas of this breccia is more uniform than in the outlying region of well- 

 bedded deposits, where fragments with quite different habits may be found 

 intermingled. The whole accumulation is, besides, more scoriaceous and 

 slag-like. 



