WILLIS] GENERAL GEOLOGIC NOTES 41 



rise to wind eddies, nor all of the loess drifts that accumulated in 

 them, can be assigned to a single epoch. He believes that the deposi- 

 tion of various local deposits of the Upper Pampean type has been 

 distributed over a considerable interval of time and is still going on. 

 If so, fossil remains found in them may be similarly distributed. 



7. Although the pampas may be described as elevated plains, they 

 have suffered but very little erosion. The development of valleys 

 is in an incipient stage. There are extensive areas which are not 

 drained by streams, and the characteristic topographic form is a 

 shallow wind-scooped hollow. The flatness of the surface and the 

 meagerness of the rainfall undoubtedly retard the growth of erosion 

 channels, but the Pampean loess is easily eroded and can not long 

 have been exposed at the elevation and with the slopes which it now 

 exhibits, without dissection. Hence it is inferred that the elevation 

 is a result of recent warping. Some of the Upper Pampean deposits 

 occur in the incipient valleys tributary to the Parana. The valleys 

 are consequent on the slope due to elevation, and are therefore 

 younger, and the Upper Pampean drifted into the valleys is 3'^ounger 

 still. 



8. The coast of Argentina presents a line of sea cliffs and beaches 

 which are being vigorously attacked and are in process of constant 

 changes. The sea is constantly eroding the land, and the coast line is 

 geologically a very transient feature. It must shift from century to 

 century to a perceptible degree and can not have occupied its present 

 position at most more than a few thousand years. Upon this shifting 

 shore the winds and waves have built certain equally temporary 

 formations, among which the dunes are the most conspicuous and the 

 coquina is the most interesting, at least in the study of man's supposed 

 antiquity. The physical evidence of the relation of the dunes and 

 the coquina to the recent coast line is definite and positive. Those 

 formations are as recent as the coast line is, and any organic remains 

 found in them, whether human or otherwise, or any artifacts which 

 they contain as contemporaneous deposits, must also be recent. The 

 only exception to this conclusion is found in the possibility that 

 fossils weathered out of older formations may become incorporated 

 in the younger. 



Report on Shells Collected by Bailey Willis and A. Hrdlicka 



IN Argentina 



By Wm. H. Ball 

 Geologist and Paleontologist, U. S. Geological Survey 



The following is my report on the shells brought [by Dr. Hrdlicka 

 and Mr. Willis] from Argentina and submitted to me for de- 

 termination. The age of the various beds from which the speci- 



