530 Reviews — Hartfs Geology of Brazil. 



series of red sandstones (apparently barren of fossil -remains), and 

 lithogically identical with the Connecticut Eiver and New Jersey 

 New Eed Sandstone, The author refers these to the Triassic epoch. 



During the Jurassic period, the Brazilian coasts would appear to 

 have been elevated lands, like Eastern North America, as no rocks of 

 Jurassic age have as yet been observed. 



The Cretaceous rocks of Brazil begin a few miles south of the Bay 

 of Bahia, and occur at intervals along the coast northward, occupying 

 several separate basins, some of which are fresh-water. Their 

 extent is uncertain, as they are largely covered by Tertiary beds. 

 Probably marine Cretaceous beds underlie the Tertiary deposits 

 throughout the whole valley of the Amazons ; they are only exposed, 

 however, on the Aquiry, an affluent of the Eio Purus, where they 

 were examined by M. Chandler. 



The fossil mollusks of the freshwater beds of Bahia have a very 

 strong Wealden aspect. An account of this deposit will be found in 

 the Quart. Journ. G-eol. Soc, Lond., vol. xvi. p. 263, given by Mr. 

 S. AUport, with notes on the fossils by Prof. Morris, Prof Owen, etc. 



Mr. Hartt proposes the following classification for the Cretaceous 

 rocks of the Brazils : " Amazonian group " (Aquiry), with Mosasau- 

 rus ; Ma3strichtien ?. " Cotinguiban group," with Inoceramus, Am- 

 monites, etc., Senonien?. " Sergipian group," with Ammonites and 

 Ceratites; Middle Cretaceous ?. "Bahian group," Crocodilus, Pisodus, 

 Melania, Cyprids, etc., Neocomian?. 



Two sets of Tertiary Clays and Sandstones are described, one 

 forming the coast -plains outside the Cordilheira, and overlying the 

 Cretaceous beds unconformably ; the other series occupying the 

 Jequitinhonha and Sao Francisco valley, and resembling the coast- 

 clays, save that they are thicker, stand at a very much higher level, 

 and in some cases form beds of pure sandstone and conglomerate, 

 with limestone and iron ore. These higher beds are also covered by 

 drift-clays. Another deposit known as Tapanoacanga, " consisting 

 of angular or rounded fragments of micaceous iron and other rocks, 

 cemented together by an ochreous paste, which sometimes exists 

 without the gravel." This deposit is said to wrap round the highest 

 mountains like a mantle. 



At Minas Novas and elsewhere gold is mined in a similar gravel 

 (called cascalho) composed of rounded quartz pebbles, etc., with a 

 ferruginous cement, and overlaid by a bed of clay. 



This same sheet of quartz pebbles and overlying clays covers all 

 the Province of Eio (except the flat alluvial plains bordering the 

 coast) to the tops of the highest hills. The deposit is said to be 

 everywhere unstratified. The same layers extend over the provinces 

 south of Eio. Near Eio and elsewhere, occur deposits of immense 

 boulders of trap, gneiss, etc., which Professors Agassiz and Hartt 

 consider to be evidently rriorainic, and the work of local glaciers ; 

 and Professor Agassiz has described similar moraines as existing in 

 the Province of Ceara. 



The agent invoked by the learned Professors for the formation of 

 this vast deposit of structureless clays, gravels, and boulder- deposits, 

 is Glacier Ice. 



