GEXEEAL AND ECONOMIC GEOLOGY 259 



sideration.^" The rocks abont Cuyaba underlie the Devonian sandstones 

 of the Chapada and were called the Ciiyaba slates by Evans. I have per- 

 sonally examined this series at and about Cnyaba and in the region be- 

 tween Cuyaba and Diamantino. I was unable to find any fossils in them 

 in the short time I could give to the work, but inasmuch as the Chapada 

 Devonian beds rest unconformably on them, it is quite evident that they 

 are older than the Devonian and that they are clearly separated from it, 

 I have therefore referred them tentatively to the Silurian, including in 

 this division both the slates exposed at Cuyaba and the zone of folded 

 sediments described by Cicero de Campos as being near Sao Luiz de 

 Caceres, and by Evans between Livramento on Eio Cuyaba and Barra dos 

 Bugres on Eio Paraguay, and seen by me where it is crossed by the road 

 between Rosario and Diamantino.^* 



The area called older Paleozoic, about the headwaters of Eio Alto Ara- 

 guaya, in the eastern part of Matto Grosso, is known only from the few 

 notes of Castelnau and Pohl, and those are too brief to be of much service. 



That the higher portions of the region between Cuyaba and Eio Par- 

 anahyba is Cretaceous is inferred from the following : 



1. In Sao Paulo the Cretaceous overlies the Triassic and forms the 

 hilltops. 



2. Dr. Lisboa found outliers of Cretaceous along the railway route 

 between Itapura and Aquidauana.^^ 



3. Castelnau's description of the route between Goyaz and Cuyaba 

 shows the Matto Grosso plateau to be of horizontal red sediments, which 

 begin at Serra do Taquara on the east and end, abruptly at Serra da Agua 

 Branca on the west.'^^ 



4. The reference of these beds to the Cretaceous is in keeping with the 

 supposed Cretaceous age of the Parecis sediments. 



In a preliminary report by Dr. Lisboa on the manganese and iron 

 mines of Urucum, in the State of Matto Grosso. and dated March, 1918, 

 he gives the following table as the expression of his own views and those 

 of Euzebio de Oliveira in regard to the sequence of the rocks in that 

 state : 



^ Reconhecimento geologico do Noroeste de Matto Grosso, pp. 74-75. Rio de Janeiro, 

 1915. 



®s Both Silurian and Devonian are found at Sucre, Bolivia, west of CuyabS. See Hoek 

 and Steinmann. Pet. Mitt.. 1906. I. 



^^ Oeste de Sao Paulo e Sul de ?iIatto Grosso. mappa. 



'0 F. de Castelnau : Expedition dans . . . rAm^rique du Sud. Histoire du Voyage, 

 vol. ii, pp. 262-265. Paris, 1850. 



