BCTCKEYE PEAK. 193 



Buckeye Peak. On the west of East Arkansas Valley, between it and 

 Eagle River, is a broad-topped mountain mass, whose highest point is Buck- 

 eye Peak, at the head of the gulch of the same name. To this peak, on the 

 Hayden map, no name is given, but a minor point of the ridge to the north 

 is called Mount Arkansas a name which -has been given by the miners, 

 with more propriety, to the prominent peak west of the Arkansas amphi- 

 theater; this transfer of the latter name has therefore been adopted on the 

 present map. On the south face of Buckeye Peak, forming the wall of its 

 amphitheater in a height of nearly 1,000 feet, is exposed a great mass of 

 Eagle River Porphyry, whose prominent vertical cleavage planes and joints 

 give the appearance of columnar structure observed on the summit of Mount 

 Lincoln. On the debris-covered slopes and grassy ridges its outlines could 

 not be traced with perfect accuracy, but it seems probable that it is a lacco- 

 lite body, from which the other irregular bodies of the same rock in the 

 vicinity may be offshoots. It is somewhat lighter colored than the porphyry 

 observed in the Arkansas Valley, and under the microscope shows no glass 

 inclusions, but otherwise is identical with that rock. A dike-like offshoot 

 from the body extends to the west along the ridge at the head of Tennessee 

 gulch. To the south the beds of the Weber Grits formation seem to dip 

 away from it for a short distance and then resume their southeasterly dip. 

 Above it, on the summit of the peak, these beds lie nearly horizontal. On the 

 eastern base of the peak, at the head of the spur which runs down between 

 Buckeye gulch and the Arkansas, is a small outcrop of decomposed por- 

 phyry, so white that it might be taken for Nevadite or White Porphyry. 

 Microscopical examination, however, shows that it is probably a portion of 

 the Eagle River Porphyry body. Across' the northern ridge of Buckeye 

 Peak runs a dike-like mass of porphyry about 200 feet in thickness, which 

 can be traced almost continuously down the bed of Deluionico gulch in a 

 steep wall, through which the present stream has cut a steep, narrow bed. 

 Its outcrops are obscured by moraine material. This gulch, as well as the 

 other main gulches which radiate out from Buckeye Peak, bears evidence 

 of having been once filled by a minor glacier, both in the fact that relics of 

 moraines can be found along its sides and in that its slope is not such a 



MON XII 13 



