8 THE DESEADO FORMATION OF PATAGONIA 



Turritellas, Brachiopoda, sharks' teeth, etc. It is separated 

 from the Deseado by a marked unconformity, one of 

 the finest examples of unconformity I have ever seen. 

 Evidently the upper surface of the Deseado was fairly new 

 at the time of the transgression, or k is much disturbed by 

 the transgression, the upper layers in places being broken up 

 into sort of blocks and the crevices filled with Patagonian 

 sands with the contained shells; just as I saw the beds 

 on the seashore being disturbed by the waves of today. 

 Then too in the basal foot of the Patagonian I found 

 material which without question came from the underly- 

 inp Deseado beds, various fragments of mammal bones 

 bored by seashells, and with the Patagonian barnacles 

 on them, but these were never more than a few inches up 

 in the Patagonian. The contact was not horizontal, but 

 in the middle of the hill dipped down so that it came there 

 onto the yellow beds of clays, and it was at this point only 

 where we found bones had been washed out by the Pata- 

 gonian sea. 



In the section the Deseado consists of layers 2 to 5, 

 the white sandy clay below belonging to the St. George 

 series and being Cretaceous. The contact below was 

 also an unconformity, clearly marked for the white sandy 

 clays were all horizontally bedded, while the Deseado is 

 crossbedded in every direction, and has a distinct color. 

 These white sandy clays of the St. George series are simi- 

 lar to the same beds as shown in sections A and B (figures 

 3 and 4), and extend in all directions for miles. Going 

 down toward the Chico River one passes into the green 

 shales that make up the upper part of the Salamanca and 

 had similar invertebrate fossils. About ten miles to the 

 north was another bed of fossil trees similar to the one to 

 be described on the Puerto Visser side of the pampa. 



The character of the material making up the Deseado 

 deposit, its variations in size and material, the presence 

 of worn pebbles and bits of bone, show these layers to be a 



