Feb., 1911.] Literature on Geology of South America. 275 



On the Pacific slope of the Andes from Patagonia northward 

 the old fonnations show a siinilar three-fold division and arc said 

 to have essentially the same characteristics. It is probable, 

 however, that these formations are of much later age. 



PALEOZOIC. 



The Lower Paleozoic Rocks. The lower Paleozoic formations 

 of South America are not always recognizable and are perhaps 

 wanting in some regions where later fonnations occur, but it is 

 probable that a portion of the crystalline schists, quartzites and 

 slates which have been referred to the pre-Cambrian are in reality 

 early Paleozoic formations. In the Amazon region Derb}' says 

 that the Silurian rests unconfomiably "on an extensive series of 

 quartzites superior to"^ the gneiss, but the age of this assemblage 

 of rocks is not suggested. In this same region Katzer inaps the 

 Silurian as unconformable on a series of metatnorphic rocks', which 

 appear to be of pre-Cambrian age. 



In Bolivia and northwestern Argentine occur outcrops of 

 sandstones and quartzites in which a fauna of Upper Cambrian 

 age (Agnostus, Olenus, Conocoryphe and Ptychoparia) has been 

 collected.^ The base of this series of rocks is not exposed and its 

 thickness is tmknown. In this same general region (Bolivia and 

 Argentine) the Ordovician is represented by yellow argillaceous or 

 qtiartzitic sandstones and black shales which are thought to rep- 

 resent the same horizon as the Orthoceras limestone (base of 

 Ordovician) of the Baltic.^ Among the fossils collected from 

 this horizon are Illacnus, Orthoceras and Eudoceras from the 

 sandstone, and four genera of graptolites from the black pyritic 

 shales exposed along Rio Corauhuata at Culi, Bolivia.^'' DeLap- 

 parent says this same fauna also occurs near Lima, Peru; and 

 again along the coast of Venezuela between Caracas and Puerto 

 Cabello, the finding of Ordovician fossils, among which is Calyni- 

 mene senaria,^^ indicates the presence of this system. 



Silurian rocks are reported to occur along the coast of Chili 

 but they are highly metatnorphosed^- and have not been well 

 described. In southwestern Brazil, southern Peru and north- 

 western x\rgentine the Silurian rocks outcrop almost continuously 



6. Derby, O. A., Amer. Jour. Sci., 3d ser., Vol. XIX, ISSO, p. 324. 



7. Katzer. Friederich, Grundztige der Geologie des unteren Amazonas- 

 gebietes. 1903. (Leipzig), p. 21G. 



8. Kayser, E., Beitrage zur Kenntniss einiger palaeozoisher Faunen 

 vSiidamerikas (Reviewed by Freeh). Neues Jahrbuch fiir Mineralogie, 

 Geologie und Palaeontologie. Band II, 1898, p. 472. 



9. DeLapparent, A., Treate de Geologie, Tome III, p. 808. 



10. Evans, J. \V., Quart, jour. Geol. Soc. London, Vol. LXII, 190G, 

 p. 431. 



11. Drevermann, Xeues Jahrbuch, Band I, 1904, p. 91. 



12. Forbes, David, Quart. Jour. Geol. Soc. London, Vol. XVII, 1860, 

 p. Gl. 



