A Fault Plane of Unusual Aspect. 



295 



richi* considers the Rodadero an igneous intrusion molded by 

 glaciers before the molten rock had cooled. The popular ex- 

 planation of the smoothed, hummocky surface of the Rodadero 

 is in line with the views expressed above, and it must be admit- 

 ted that we are dealing with a remarkably exact imitation of a 

 " roches moutonnes " surface. The resemblance between the 

 Rodadero and glacially eroded surfaces, made familiar by field 

 experience, is in fact so close that my first impression was in 

 accord with the views of Duefias and Posnansky in spite of the 

 warning of my observant colleague, Professor Bowman. f The 

 theory that an ice sheet played a part in molding the Rodadero 



Fig. 6. 









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Fig. 6. Ledge of limestone adjoining the striated Eodadero. 

 with figures 4, 5, 7, and. 8. 



Compare 



was, however, abandoned in view of the following observa- 

 tions : 



(1) There is no evidence of glacial erosion in the Cuzco 

 region at so low an elevation. The Eodadero stands at 11,700 

 feet, while the lowest moraines on the Seneca, three miles dis- 

 tant, are intersected by the 12,500-foot contour. (2) The stria- 

 tions on the Eodadero are duplicated on another igneous knob 

 one-half mile to the eastward, but the projecting ledges of 

 resistant limestone immediately surrounding the igneous masses 

 show no signs of glacial action either on the surface or in 

 recent excavations. (Fig. 6.) The freshness and perfection of 



*Tesis Universidad del Cuzco, p. 18 ; Topografia Infantil Cuzco, 1911. 

 f This Journal, xxxiii, p. 317, 1912. 



