; 
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WOODWORTH: GEOLOGICAL EXPEDITION TO BRAZIL AND CHILE. 75 
northeastern Parand is highly suggestive of moraines laid down by 
land ice; but other sections in Sao Paulo and to the south and west 
in Parand are equally clear as to their deposition by floating ice at 
times at any rate in the sea as the presence of marine fossiliferous 
marine shales in Parana plainly show. 
More particular problems arising in the study of these glacial 
deposits are discussed under separate headings. 
The Striated Pebbles. — So far as present knowledge goes, striated 
surfaces have not been found on the large boulders and block erratics 
in south Brazil, but such ice-worn surfaces are frequently met with 
on pebbles and fragments of rock ranging.from the size of a hen’s egg 
to that of a man’s head. In almost every exposure of conglomerate 
whose pebbles fail to display the well-rounded contour of water- 
wear a few striated pebbles may be found after a few minutes search; 
yet of these sections I saw none in which all the pebbles and fragments 
were striated. On the whole the proportion of striated pebbles in the 
tillite beds is about as large as it is in the granitic till of the glacial 
deposits of New England, but glaciated stones are certainly not so 
abundant in any given mass as they are in the stony blue clays of 
many localities in the Pleistocene deposits of, for instance, portions 
of the Wisconsin moraines of the state of New York. 
The absence or apparent absence of striae from the larger blocks 
and boulders is quite in keeping with the distribution of striae in the 
Pleistocene of many districts and has little significance in the argu- 
ments for or against glacial action, though in the case of the Brazilian 
deposits striae were not earlier noted perhaps because attention was 
given more to the blocks of striking size than to an examination of the 
worn surfaces of small fragments of transported rock. 
Broken up striated Rock-floors— As the glaciation and consequent 
striation of the indurated terrane over which the ice moves proceeds, 
the rock-floor particularly at the upstream edges of small declivities 
in the rock-surface breaks away, so as to produce angular fragments 
with one flat well-striated surface — that of the original floor. Such 
pieces of rock may subsequently be striated over all their new fractured 
surfaces but will for short journeys tend to preserve their features. 
Thus the striated stone shown in Plate 27, the first striated fragment 
feund in Parana, presents all the ear-marks on its well worn and 
striated side of a piece of old rock-floor even to the chatter-marks in 
the broader and deeper groove; while on the reverse, where there are 
two intersecting warped surfaces one is slightly scratched, and the 
other is a much more recent fracture, still of a date anterior to the 
final embedding of the pebble. 
