50 bulletin: museum of comparative zoology. 



the Devonian sandstone cuesta in the Serra das Furnas and by the 

 Serra da Paranapiacaba. 



That this gentle broad warping of the Post-Devonian strata is of 

 Post-Permian date is shown by the sinuous trend of the outcrops 

 of the Permian terrane. That it is Post-Triassic is also indicated 

 by the down bending of the trappean sheets in the syncline on the 

 south. Precise evidence of a local nature is apparently lacking to 

 demonstrate how long after the completion of the local Triassic 

 section the deformation was produced. The dislocation of the Triassic 

 Newark beds of eastern North America in presumably early Jurassic 

 time would lead us to admit that the deformation of south Brazil 

 may have taken place at this time. For topographical reasons set 

 forth in the account of the physiography' of this region (p. 99) it 

 seems that this type of deformation took place in Pre-Cretaceous times. 

 A Jurassic date for the deformation thus appears the most probable one. 



Summary of Geological History of the south Brazilian Plateau.— 

 From this brief account of the geology of the south Brazilian plateau 

 it appears that, long prior to the Devonian period, the region passed 

 through a series of changes registered in the occurrence of igneous 

 and metamorphosed sedimentary rocks as yet little understood. At 

 least one series of sediments now slates and limestones involved in the 

 complex may be the equivalents of the Ordovician or Cambrian strata 

 but fossils are wanting to prove the age of these beds. The basal 

 Devonian sandstones resting on the eroded edges of these meta- 

 morphosed and intrusive rocks can only be interpreted as evidence 

 of land conditions in the epoch preceding the Devonian and hence 

 in the Silurian (Upper Silurian of Murchison). The Devonian sea 

 transgressed the area and continued depositing sediments through the 

 middle of that period. Whether deposition took place in the Upper 

 Devonian is not now clear. The Carboniferous period was so far as 

 the records go one of land denudation in which most of the Devonian 

 was swept away. The extent of this denudation is such as to render 

 it probable that higher Devonian beds originally overlay the Middle 

 Devonian shales of Parana. 



True Carboniferous deposits appear to be wanting in the area, such 

 strata as may have been referred to this epoch belong rather to the 

 basal Permian. 



The Permian is characterised by a series of mainly non-marine 

 formations laid down at or near sea-level with locally well-developed 

 beds of tillite indicative of a glacial period. Elements of the Gloss- 

 opteris flora have been found in Santa Catharina in shales which carry 



