336 J. B. Hatcher — Geology of Southern Patagonia. 



etc.,) the remains of which are everywhere so abundant in all 

 the known marine Cretaceous deposits of the world, but which 

 are singularly wanting in the Patagonian beds. Since there 

 has not been reported up to the present time a single species 

 characteristic of the Cretaceous period from the typical Pata- 

 gonian beds on the east coast of Patagonia, and since the entire 

 facies of the fauna is Tertiary, there is no good reason, from a 

 paleontological standpoint, for referring any part of this forma- 

 tion to the Cretaceous. 



The arguments advanced by Dr. Ameghino for assigning the 

 Lower Patagonian beds to the Upper Cretaceous on account of 

 certain remains of Mosasaurs, Plesiosaurs and fish of Cre- 

 taceous types found in the vicinity of Lake Viedma, are of 

 little value, since those beds have never been properly identi- 

 fied as the Patagonian beds. 



The stratigraphical evidences in favor of referring the whole 

 of the Patagonian beds to the Tertiary appear to be quite con- 

 clusive, assuming that the Guaranitic beds are Upper Cre- 

 taceous. That there was a considerable lapse of time between 

 the close of the deposition of the one, and the beginning of 

 that of the other, series of deposits is evidenced by the altered 

 nature of the materials, which show not only that they were 

 derived largely from different sources, but that they were 

 deposited in the one instance in fresh water and in the other 

 in salt water over identically the same geographical districts. 

 Again the appearance of the Guaranitic beds, on the coast at 

 San Julian, where there are no disturbances in the Patagonian 

 beds, can best be accounted for by assuming that they repre- 

 sent a prominence in those beds, due to erosion, which took 

 place after the close of the deposition of the Guaranitic beds 

 and prior to the deposition of the Patagonian beds. More- 

 over in vast areas, throughout the interior, the Guaranitic beds 

 are immediately overlaid by formations much more recent than 

 Patagonian, thus showing a decided unconformity by overlap 

 between the two series. No interstratification of the two 

 series has ever been observed, which would have been the 

 natural result had they been deposited simultaneously and had 

 marine and fresh-water conditions prevailed at the same time 

 in adjacent regions. 



Most of the confusion which has arisen regarding the age of 

 the Patagonian beds, has doubtless been due very largely to the 

 carelessness of collectors. For many years every fossil-bearing 

 horizon discovered anywhere in southern South America and 

 containing a large oyster, was referred without question to the 

 Patagonian beds, and collections were made indiscriminately at 

 many different localities and from many different horizons 

 from the Upper Cretaceous to the Pliocene, all referred to the 

 Patagonian beds and placed in the hands of specialists for 



