^PHELIXE-EOCKS in bkazil. 



461 



metres, the highest of the denudation-ridges in the part here con- 

 sidered rising to a little over 700 metres. The geological age of 

 this plateau has only in part been determined. The lower beds are 

 soft shales and sandstone with flagg}^ siliceous limestones, which 

 last are remarkably persistent, having been found across nearly the 

 whole width of the Provinces of Sao Paulo and Parana, a distance 

 of about 300 miles. The limestone has afforded fossil reptiles, wood, 

 and a few unsatisfactory shells, all of which indicate Upper Palaeozoic 

 (Carboniferous or Permian) age. The most satisfactory fossils are 

 the silicified woods, which include Lepidodendroids, conifers of the 

 Dadoxylon-tyve (conifers with a single row of pores also occur), and 

 ferns of the type of Pscironius. Above the limestone come heavy 

 beds of sandstone with intercalations of a melaphyre-like rock, often 

 porphyritic and amygdaloidal, which has not afforded fossils, but is 

 presumably Permian or Triassic. The railway for some distance 

 out from Campinas is at times on the sedimentary series, at times 

 among gneiss, hills of the mountainous zone ; but after crossing the 

 river ^logyguassu the latter disappear and the main line to Casa 

 Branca follows a flat-topped sedimentary ridge between that river 

 and the Rio Pardo, leaving the Caldas group of mountains, which 

 lies between the head-waters of these two rivers, to the eastward. 

 The Caldas branch runs over the sedimentary series to within about 

 10 miles of the foot of the mountain, where it disappears, giving 

 way to the gneiss foot-hills. Sedimentary rocks, however, appear 

 in a narrow belt along the foot of the mountain, and it is probable 

 that the interruption above noted is due to the fact that the railway 

 follows the bottom of a valley, and that on the heights on either 

 side the sedimentary strata extend continuously to the mountain. 

 At all events there are no reasons for supposing that the beds at the 

 foot of the mountain belong to a different series from those further 

 away, whose geological age is fixed by the occurrence near Casa 

 Branca of limestones with characteristic fossils. 



The railway ascends the mountain on one side of the valley of the 

 Corrego (brook) do Quartei, rising in a distance of 18 kilometres 

 from 820 metres at the Prata station to 1270 metres at the summit. 

 The eruptive series begins to appear about 2 kilometres from the foot 

 of the serra in a cutting near the Prata bridge, where a greenish 

 spotted phonolite appears associated with gneiss. Then follow a 

 few low cuttings of sandstone of no special interest. "The ascent 

 proper commences with the passage of a narrow gap between 

 magnificent cliffs of sandstone rising about 50 metres above the 

 road-bed. This gap is cut through a narrow ridge set like a wall 

 across the end of the rather broad valley of the Quartei. The 

 sandstone is a very hard fine-grained white rock, broken by joints 

 into small angular fragments, and is very similar in appearance to 

 some of the beds of quartzite (itacolumite) of the metamorphic series, 

 and quite unlike the ordinary sandstones of the sedimentary group 

 above described. That its relations are with this group rather than 

 with the older one is, however, proved by thin beds of soft clay- 

 shales intercalated in it near the base along with a thin layer of 



Q.J.G.S. No. 171. 2 1 



