BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 3, pp. 183-186 March 31, 1892 



ON THE NORTHWARD AND EASTWARD EXTENSION OF THE 

 PRE-PLEISTOCENE GRAVELS OF THE MISSISSIPPI BASIN. 



BY R. D. SALISBURY. 



[Abstract.] 



(Presented before the Society August 25, 1891.) 



CONTENTS. 



Page 



Early < )pinion as to the Age of the " Orange Sand " 183 



I >iscovery of " Orange Sand " within the I >rift Limits 184 



Ancient Gravels replacing Drift 184 



Ancient ( travels underlying Drift 184 



Relations of the pre-Pleistocene Gravels 185 



Early Opinion as to the Age of the "Orange Sand." 



In a recent number of the American Journal of Science* President 

 Chamberlin and myself discussed at sonic length the relationship of cer- 

 tain gravels in the middle Mississippi basin to the loess and to such other 

 formations of that region as were demonstrably of Pleistocene age. In 

 thai article we expressed the conclusion that the gravels in question, 

 composed mainly of chert and of other silicious impurities from lime- 

 stone, were of pre-Pleistocene age. The evidence on which this conclusion 

 was based need not here he repeated. We then believed it adequate to 

 the conclusion reached, and nothing has subsequently been discovered 

 by us to weaken the force of the arguments then used or to alter the con- 

 clusions based upon them. 



Since the discussion referred to was published, some additional facts 

 have come to light which have an important hearing on the question at 

 issue. A brief note concerning these newer discoveries has already 

 appeared in the American Journal of Science.!' It Lsthe purpose of this 

 paper to set forth somewhat more fully the bearings of the data recently 



acquired. 



1 



*:•,(! series, vol. \li, L891, pp. 3 i9-377. 

 ; id series, vol. xlii, 1801, pp. 262-253. 



(18 



