OF THE SEKGIPE-ALAaoAS BASIN OF BRAZIL. 379 



These and the other loealities mentioned below are the only ones examined that 

 are judged to be of sufficient importance, or at which sufticiently valual)le observa- 

 tions were made, to be worthy of mention here. Hundreds of places were visited in 

 this region at whieli poor exposures of cretaceous rocks were found, but tliey could 

 thiuw IK) additional light upon the geologic structure of the region witliout the use 

 of more trustworthy methods of work than it was possible to employ at the time. 



Inasmuch as the tertiary geology of this region is the subject of the second pan 

 of the pi"esent paper, the beds of this series are not discussed in this place. 



In view of its general impoitanee and the light it throws upon the structure of 

 the entire region the details of the Itabaiana exposures will be taken up first. 



Itahaidna. — The best section seen of the rocks underlying the meso/oic beds ai'c 

 exposed where the Rio Sergipe cuts through the range of mountains of which Itabai- 

 ana forms a part. Here the crystalline rocks are exposed on the inland side of the 

 range, and in the gap cut by the I'iver, the unconformable contact between these and 

 the sedimentary l)eds, which are presumed to be paleozoic, is plainly seen. The 

 conglomerates, false bedded sandstones, and shales which make up the great body 

 of the section, have been so metamorphosed that the [)rospect for finding fossils in 

 them is not very encouraging. 



The sandstones are alyiost all changed to exceedingly liaid, glassy quartzites, which 

 by much jointing have broken into smooth-sided rhomboidal blocks. Following 

 down the stream one ascends geologically, and finds these quartzites and conglomer- 

 ates the principal rocks exposed, while those of shale, in which one most hopefully 

 looks for fossils, are but poorly exposed or entirely covered with talus from the over- 

 hanging ledges. Th»!se beds have a j)retty uniform dip of 15-20° to the south-cast. 

 Along the escarpment of the north face of the mountain range the uptiu'ned edges 

 of the up|)ermost beds are partly exposed, while all the lower ones arc covered with 

 talus which stands at as high an angle as possible. In this talus large fragments of 

 shale, such as was not seen in situ were examined for fossils, but without success. 



The brief time spent in examining the rocks of this .section lor paleontologic 

 evidence of their age was very insufficient, and it is altogether probable that careful 

 detailed examination of these beds will yet furnish the desired evidence. 



From the top of Itabaiana the struct me of this range of mountains and its geolo- 

 gic relations to the regions on either side of it are quite evident. The Itabaiana peak 

 is at the base of a curve in the ranjre which contimies to the right, as one faces the 

 ocean, towards the west and south-west, while lo the left it extends to the north and 

 north-west. About fifteen miles to the north the range turns castwaril and is next 



