STK,UCTURAL DETAILS 311 



butte, and observed that the horizontal Cretaceous beds which, form the 

 terrace or encircling platform continue close up to the tower without any 

 signs of disturbance. From the northwest and west vertical columns 

 curving outward toward the base are seen, as well as some places which 

 suggest a cross-section view of more or less radially disposed columns. 

 White and yellow sandstone, apparently not greatly affected by heat and 

 quite horizontal, were found near the top of the terrace, within less than 

 a hundred yards of the base of the tower. 



We examined Cabezon around more than three-quarters of its circum- 

 ference (see plate 25 and figure 3), linding it very symmetrical, cylin- 

 drical in shape, with a number of exposures of the horizontal l)cds about 

 its base and abundant evidence of vertical columnar structure, although 

 the columns are nowhere so perfectly developed as in the Devils tower. 

 We observed no direct contact between the igneous rock and the sedi- 

 ments as we did in other cases, and found the base of the tower and the 

 surrounding sediments more obscured by talus and vegetation than was 

 usually true. 



In general the buttes of tlie Mount Taylor region do not rise above the 

 former level of the lava cap, as indicated by the adjacent remnants of 

 the lava-capped mesas. Cabezon is one of the two exceptions which we 

 noted. It is evident that both Cabezon and Great neck rise above the 

 level of Prieta mesa, although Cal)ezon is little, if any, higher than the 

 top of ]\Iount Taylor mesa to the west, while Great neck does not reach 

 that level. Both Ijuttes show features which are of special interest in 

 connection with the imusual heights to which they attain. Thus, while 

 the main portion of Cabezon is made up of dark, compact Ijasalt, the talus 

 slopes show much vesicular basalt, black, gray, and red in color, weath- 

 ered down from the summit. The surface of the lava cap on Prieta 

 mesa slopes upward toward the nortli, as if rising toward a large cojic 

 which formerly existed above the Cabezon butte, Ijut M'hich has Ijeeu 

 destro3'ed by erosion. Both buttes are of unusually large diameter, thus 

 having a better chance for the preservation of their upward continuations 

 in overlying lava flow or cones. The slopes at the base of Cabezon are 

 strewn with fragments of a peculiar agglomerate, to be descrilsed in con- 

 nection with butte numl)er 3. 



ISTumber 2, Twin Peak (plate 26, and figure 4). As seen from a 

 distance, this butte appears to be somewhat elongated in a north and 

 south direction. It is surrounded by Cretaceous sands and shales, which 

 were easily distinguished and which were apparently quite horizontal. 

 Erosion has left the northern and southern ends of the butte somewhat 

 higher than the middle portion; hence the name, "Twin Peak." This 



