76 II. E. Gregory — A Geologic Reconnaissance 



VIII-A. Section of the Bambanusa formation' 1 mile north 

 of Ccasa-Cancha. 



Strike N 30° W; dip S° NE. 



Feet. 



Sandstone, massive pink to white, even grained, consist- 

 ing of uniform fine grains of clear quartz loosely 

 cemented by calcite. Elaborately cross-bedded by 

 inconspicuous lines. Forms towers and hoodoos ... 20 



Sandstone, thin-bedded; banded pink, light red, and 

 gray ; in places merely overlapping flakes ; quartz 

 grains, calcareous cement. Includes layers of arena- 

 ceous limestone 60 



80 



VIII-B. Section of Bambanusa formation half a mile west 

 of Section VIII-A. 



Strike N 25°± W; dip 6° E. 



Feet. 



1. Sandstone, pink to gray in tone, massive, fine grained, 



cross-bedded; white and pink quartz; calcareous 

 cement 15 



2. Shale, argillaceous and arenaceous; in beds the thick- 



ness of paper 1 



3. Sandstone, pink ; well-rounded grains of quartz, micro- 



scopic size; calcareous cement; cross-bedded and 

 highly lenticular 6 



4. Sandstone, dark red ; quartz grains very fine ; calcare- 



ous cement. Arranged as irregular lumps and lenses ; 

 one lens consists of white quartz and chert pebbles 

 ranging in size from that of a pea to that of a small 

 hickory nut 4 



26 



The Bambanusa beds dip at a low angle and in a direction 

 opposite to those of the bordering Pachatucsa formation as 

 well as of the underlying Huayllabamba sandstones. This 

 unconformable relation is well shown at the head of the Chchi- 

 raura Canyon, where the eroded edges of brown sandstone 

 strata, tilted south at an angle of 40°, are covered by pink- 

 white beds with a northward inclination of about 35°. 



The strata on the Urubamba divide between Pachatucsa and 

 Atasccasa are for the present grouped with the Bambanusa 

 formation. The series consists of coarse sandstones and con- 

 glomerates in massive beds, 4 to 40 feet thick. On weathered 



