258 J. C. BEAXXEK OrTLIXES OF THE GEOLOGY OF BRAZIL 



The northeast corner of Matto Grosso. where it joins Para and Goyaz, 

 has not been explored geologically. Katzer represents the adjoining part 

 of the St-ate of Para as Cretaceous, but I do not find that any work has 

 been done in that area. Patil Fonntain. who traveled in the Xingii basin 

 and along Rio Fresco and in the mountains east of there, reports in those 

 mountains extensive caverns with abundant stalactites.^^ Of course, the 

 limestones might be of any age from Archean to Cretaceous, but. in the 

 absence of data to the contrary, it seems reasonable to suppose that they 

 are of the same age as the Permian limestones east of the Tocantins. 

 and I have therefore so represented them, subject to correction. 



The foothills east of the great marshes of the Paraguay, north of 

 Aquidauana. past Coxim, and northward nearly to 15 degrees south lati- 

 tude, Dr. Lisboa marked on his map as Mesozoic with a question.®^ Xo 

 fossils have been reported from these beds, but I have referred the rocks 

 of this area to the Triassic partly because such reference fits in with 

 what is known of the geology of Sao Paulo. The part of this zone be- 

 tween Cuyaba and Coxim was crossed by Dr. Yogel, who says the rocks 

 are mostly red sandstones. It is also evident from Castelnau's descrip- 

 tion that there is a marked change in the topography and the geology 

 where the road from Goyaz to Cuyaba descends from the Matto Grosso 

 plateau at Eio Agua Branca close to 54 degrees west longitude. 



The Devonian age of certain beds in the mountains east of Cuyaba has 

 long been known. Yogel was one of those who contributed to our knowl- 

 edge of that region. In his notes on the geology of the area southeast of 

 Cuyaba he says that certain rocks are similar to the fossil-bearing beds of 

 Taquarassii (Taquarasinhas?). and these last are Devonian beyond ques- 

 tion. I have therefore placed in the Devonian the area south of the 

 Chapada as far as Eio Sao Lourenco.®'^ The dip of the rocks in the 

 Chapada seems to carry the sandstones beneath the black shales called by 

 Evans the ^"Matto shales.'' and these black shale? underlie the sandstones 

 of the Serra dos Parcels. ' It seems possible, therefore, that the shales 

 belonof to and form the upper part of the Devonian, mucji as the Ponta 

 Grossa shales of Parana overlie the sandstones. I have therefore so 

 placed them provisionally imtil the question of their ao-e can be more 

 definitely determined. I do not overlook the views of Euzebio Paulo do 

 Oliveira that thev mav be Permian — views well worthv of serious con- 



^Paul Fountain: The River Amazon from its sources to the sea. New York. 1914. 

 pp. 212 and 249-251. 



^ M. A. R. Lisboa : Oeste de Sao Paulo. Sul de Matto Grosso. Geologia. etc. Rio de 

 .Janeiro. 1909. 



■"' P. Yogel : Reise in Matto Grosso. 1887-S. Zeit. der Gessell. f. Erdkunde zu Berlin. 

 vol. xxTiii. 1893, p. 274. 



