Palmer — Rotes on the Andes of N. W. Argentina. 325 



70 cm — fossiliferous, yellow to brown limestone, micaceous. 



25cm _ variegated shales and clay ; yellow, brown, and green. 

 110 cm — fossiliferous, gray-brown limestone. 



7^- meters — alternating gray clays, yellow shales, and gray-brown 

 limestones. 



The chemical and fossil character of this basal portion point 

 to the early conditions of deposition of this formation as being 

 marine while the later conditions, as indicated by the non- 

 fossiliferons, conglomeratic, and cross-bedded character of the 

 upper part of the formation, must have been those of terrestrial 

 deposition. 



The Marginal Faults. 



At Cienaga there was observed a perfectly clear example of 

 normal faulting. The fault is best shown on the southwest 



Fig. 7. 



Fig. 7. Sketch looking south at the Cienaga fault on the east side of the 

 Calchaqui grahen. Paleozoic quartzite and slate to the east and Jurassic 

 red sandstone to the west, separated by fault breccia. 



wall of the quebrada. To the west there is sandstone with a 

 westward dip of 58°. This was separated by a brecciated zone 

 about three meters wide from Paleozoic schists and quartzites. 

 Fortunately the metamorphics at this point included a few 

 bands of qnartzite by means of which a little of their structure 

 could be made out. A sketch of this fault as it appeared 

 in this outcrop is reproduced as fig. 7. This might be inter- 

 preted as an unconformity but for the presence of the fault- 

 gouge and breccia. 



The fault on the western side of the graben at Pircas was 

 not so diagrammatically clear as the eastern fault at Cienaga. 

 The Pircas fault appears most clearly on the north wall of the 

 quebrada, where of two adjacent and very steep spurs the 



