28 Stone — Granitic Breccias of the Cripple Greek Region. 



between Cripple Creek and Spring Creek, a small stream that 

 flows southwestward from the south end of Grouse Mountain. 

 It is about half a mile east of Four Mile Creek. 



The country rock is granite. The dike both laterally and on 

 the top is covered with a deep body or layer of breccia or con- 

 glomerate ; a bowlder bed would be a better term for it. The 

 fragmental materials consist chiefly of granitic pebbles, cob- 

 bles, bowlderets and bowlders up to four feet in diameter. 

 Most of them are as round as any bowlders to be found any- 

 where. The spaces between the larger stones are filled with 

 -crushed rhyolite and granite mixed. The bowlder bed form- 

 ing the top of the dike rises quite steeply 100 feet above the 

 surrounding granite. It is now cemented into quite a firm 

 rock, yet large blocks have fallen away from the precipitous 

 cliffs and are now found far down the southern slopes toward 

 Spring Creek. One mass 80 feet in diameter may or may not 

 have come from above in this way. On some of the steeper 

 cliffs, where the outer layer above described has broken away, 

 we find a semi-breccia composed of well-rounded granite 

 stones and bowlders embedded in the rhyolitic lava itself. 

 None of the massive rhyolite is exposed. 



The surface portions consist wholly of fragmental materials. 

 Structurally they are as well entitled to be termed lake beds as 

 the bowlder bed at the Cripple Creek reservoir, or any other of 

 the bodies of rounded granitic stones in this district, At the 

 reservoir the granitic gravel was pushed up in a loose condi- 

 tion and w T as not cemented till after it had reached the surface 

 and had time to spread over the granite at the sides of the dike. 

 But at this dike near Marigold the granitic stones were 

 cemented fast to the top of the dike before it rose above the 

 granite, a very convenient thing for the investigator. The 

 dike and the material it pushed before it as it rose are there 

 now in position to testify to what sort of work the dikes did 

 as they were pushed upward. This dike is about 600X200 

 feet in area. 



8. Phonolite dike on Straub Mountain. Elevation of the 

 grits 9300 feet and from thence rising along rather steep 

 slopes up to 9800 feet. 



This very large dike is bordered and in part overlain by a 

 broad mass of grit consisting of subangular granitic sand and 

 gravel and now and then a few fragments of phonolite. Some 

 of the stones are quite smooth and pebble-like. These grits 

 are mapped by Mr. Cross as High Park Lake beds. They, as 

 well as dikes here numbered 9 and 13, have been well 

 described by Cross, and hence need only brief reference here. 

 They overlie uneven slopes of pre-volcanic erosion. Neither 

 in materials nor in shapes of the fragments do they differ from 



