woodworth: geological expedition to brazil and chile. 113 



Parana it forms crusts in the surficial decomposed portion of the bed 

 rock. In a railway cut on the banks of the Iguassii near Serrinha 

 Station in Parana the outer portion of the Carboniferous rocks is 

 crusted with canga and this vein-Hke material there occurred in 

 joints. The segregation of canga by percolating water seems mainly 

 to be ancient; it may be older Pleistocene or still older, and probably 

 is not peculiar to any one episode of the modern geological history of 

 the region. 



The canga in some localities appears to have been broken up and 

 transported, now occurring as rubble in the red surface deposits as 

 between SjIo Pedro de Itarare and Fabio Rego. In this case the canga 

 must have been segregated prior to the transported red earth, and 

 if the red deposit be assigned a Pleistocene date the canga may be 

 referred to the Tertiary. 



The decomposed state of the rocks in Brazil was early recognized 

 and -correctly described by Jose Bonifacio de Andrada e Silva and 

 Martim Francisco Reibeiro de Andrada in an account of a mineralogi- 

 cal journey from Santos to the tableland made in 1820. This article 

 is reprinted in Ferreira's Diccinario geografico das Minas do Brazil. 

 Rio de Janeiro, 1885, p. 341, 342. 



Weather-blocks. — The weathering of the granites along the coastal 

 slope of the Serra do Mar has led to the production of thousands of 

 rounded weather-blocks which are particularly evident at the present 

 sea-level and just above within the zone of wave action, tnose above 

 the present sea-level having had the fine material between them 

 removed in part at' a time when the land stood a few feet lower than 

 it now does. Al)undant examples are to be seen about the shores of 

 Rio Harbor. The illustration, Plate 2, is from a photograph of a 

 group of blocks on the shore of Sao Francisco Harbor in Santa Catha- 

 rina. In ^Nladureira, a suburb of Rio de Janeiro, near Cascadura 

 Station there is fine large block said to be movable (pedra movedi9a) 

 poised high up on a weathered tower of granite. The famous Furnas 

 de Agassiz at Tijuco in the Serra near Rio de Janeiro is another group 

 of weather-blocks, the most imposing to be seen anywhere in south 

 Brazil. 



It remains to note certain rock benches and the uplifted fringing 

 coastal plain to be seen along the shores from Rio de Janeiro to near 

 Laguna on the south. 



From observations made about Sao Francisco Bay in latitude 26° S. 

 I suspect that there exists along this coast an old bench of marine 

 erosion 150 or more feet above the present sea-level. Numerous rock 



