298 J. C. BRANNER OUTLINES OF THE GEOLOGY OF BRAZIL 



shales having a thickness varying from 100 meters or less in the valleys 

 to more than 500 meters in the high mountains. Mr. Small gives the 

 following order and thickness of the Permian rocks of Piauhy:^° 



Thickness in 

 meters 



1. Upper yellow sandstone, sometimes false-bedded 250 



2. Middle sandstones and sandy shales 200 



3. Sandstones and lower shales 70 



The determination of the Permian age of this series rests on the pres- 

 ence of Psaronius, which has been found by Dr. Lisboa at many places 

 in this state and in Maranhao, and on a Sigillaria found by ]\Ir. Small 

 30 kilometers east of Valenga, near the east base of the Serra Baptista. 



In the southeast corner of the state Cretaceous beds overlie the Upper 

 Permian beds at a few places. The western end of the Serra do Araripe, 

 where it projects into Piauhy, is known as the Serra Vermelha. The 

 upper portion of that mountain is made of the same kinds of horizontal 

 Cretaceous sedimentary beds as those of the Serra do Araripe. A little 

 farther south, on the divide between the States of Piauhy and Pernam- 

 buco, is the Serra de Dois Irmaos, which, together with a small outlier 

 to the west of it, is likewise Cretaceous. All of these Cretaceous areas of 

 Ceara, Piauhy, and Pernambuco are merely the remnants of the original 

 wide-spread beds of Cretaceous age. A fuller description of the Creta- 

 ceous geology of this' region is given under the notes on the geology of 

 Ceara. At several places eruptive rocks appear at the surface, notably at 

 A^alenca, on the headwaters of Eio Berlenga, and at fazenda Grauta north- 

 west of Picos. 



Economic geology. — Piauhy is an agricultural and pastoral rather than 

 a mineral-producing state. The geology in its relations to underground 

 water is of special interest and has been reported on by H. L. Small. 

 (See bibliography.) Iron of excellent quality has been reported, but 

 nothing is now known of the quality or of the quantity available. 



Geologic Maps of Piauhy 



Lisboa, Ma}^, 1914. — Dr. M. A. E. Lisboa's paper on the Permian geol- 

 ogy of northern Brazil, published in the American Journal of Science 

 for May, 1914, pages 425-443, is accompanied by a small-scale sketch- 

 map showing the geology of a large part of the State of Piauhy. The 

 scale is 1 to 11,428,570 and four geologic subdivisions are shown, namely: 

 crystalline rocks, Permian, Triassic, and Cretaceous. 



soRelatorio, pp. 64-65. 



