J. B. Batcher — Geology of Southern Patagonia. 339 



gonian beds, which are here inclined at an angle of not less 

 than 15°, while not more than one-half mile below, on the right 

 bank of the same stream, may be seen an outcrop of sandstones 

 of the Santa Cruz beds, which appear nearly horizontal. In 

 fact, so far as I was able to determine, the inclination of the 

 Santa Cruz beds is nowhere appreciable, except at certain 

 points along the water courses, where it is possible to take in 

 at one view stretches of several miles of the strata, and then 

 there is apparent only a very gentle dip to the southeast. 



I nowhere found mammals in the marine beds, nor did I 

 anywhere find the two series interstratified. I observed the 

 contact between the two series at many different localities and 

 did occasionally find bones below the base of the Santa Cruz 

 beds, but they were such as had fallen down from above. On 

 one or two occasions I found bones in strata which were abso- 

 lutely lower than other strata in the same vicinity where 

 marine invertebrates were abundant, and I at first believed that 

 there had been an interstratification of the two series, but 

 upon careful examination, I found that the layer with the 

 invertebrates did not continue on so as to actually overlie that 

 with the bones, and I was brought to the conclusion that the 

 Santa Cruz beds had here been deposited upon the eroded sur- 

 face of the Supra-Patagonian beds. An example of this may 

 be seen in a small canon on the south side of the Rio Chico 

 about two miles below Sierra Oveja. In going up the val- 

 ley of Chico River it is impossible to be mistaken as to the 

 old crater {Sierra Oveja), since it rises directly from the bank 

 of the stream and compels one, if traveling with a vehicle, 

 either to cross the river or go around to the west of the moun- 

 tain, neither of which routes is particularly good. About two 

 miles below this crater there enters the river valley from the 

 west a narrow, deep canon. Ascending this canon some 200 

 yards, there appears on the south side of it a projecting sand- 

 stone ledge, about two feet thick, with an abundance of oyster 

 shells. Proceeding a little farther, the canon is seen to open 

 out into a small, deeply eroded, " bad land " basin. Continu- 

 ous all the while on your left is the oyster-bearing, sandstone 

 ledge, which, at a distance of about one-half mile from the 

 mouth of the carion, becomes covered by talus : this condition 

 continues for perhaps 100 yards, when the section is again 

 clear, and in the lowermost layers there are mammal remains, 

 while the sandstone layer with its oysters is nowhere to be 

 found. It is true that the bottom of the canon has been all 

 the time rising, but the elevation did not appear sufficient to 

 bring the shell-bearing layer below its surface ; I therefore 

 concluded that the sandstone layer with oysters had been 

 eroded away before the deposition of the mammalian beds. 



