woodworth: geological expedition to brazil and chile. 



93 



consequence of erosion. In the section which can be constructed 

 from the exposures along the road from Rio Negro to Lages at the 

 pass through Collectoria it is possible that a fault can be traced 

 cutting off the Espigao from the main mass of trap on the south 

 at the right of the section in Fig. 24. But this interpretation of the 



Fig. 24. — Section acro.ss the Serra do Espigao at tlie Collectoria on the road 

 from Rio Xegro to Laeres. 



tilted beds at the bottom of the valley and the apparently lower 

 level at which the trap lies south of the stream crossing demands 

 a throw of the normal fault on the south side in a manner nowise 

 supporting the hypothesis that the escarpment is due to a fault. 

 This northerl}- steep dip has by some been regarded as cross-bedding 

 and is stated to occur elsewhere along the trap escarpment in the 

 underlying sandstones. 



Number of the trap sheets. — It is stated that there are four trap 

 sheets or sets of sheets in the trap mass of the Serra Esperan^a on the 



tAGfi 



roftr r.fiA^os 



Fig. 25. — Cross-section of the Trap plateau from the Rio Negro to Lages. 

 1 (dotted). Sao Bento beds. Triassic. 2 (right lined). The Collectoria 

 trap sheet. 3 (cross lined). The Corisco trap sheet. 4. The Third 

 (and Fourth?) trap sheets. 



north of the valley of the Rio Iguassu. In Dr. Derby's section the 

 trap is diagrammatically represented as if composed of surface flo\\s. 

 The number of flows or sheets entering into the plateau between the 

 Serra do Espigjio and the sandstone area about Lages was not de- 

 finitely determined by observation upon the ground but the plotting 

 of the profile of the route and the outcrops of sandstones encountered 

 in the trappean tract leads to the conviction that along this route 

 there are at least three great sheets of trap separated by sandstone 

 beds. The sul)joined figure section (Fig. 25) gives the approximate 

 profile and geological section along a line paralleling the road from 



