364 Chamberlin and Salisbury — Relationship of 



Mississippi river, as at Memphis, Term , where there is some evi- 

 dence of the division here suggested. The evidence consists in 

 the presence of a thin layer of humus-stained (apparently) loam, 

 between beds of loess, suggesting an old soil. At Forrest City, 

 Ark., there is a similar layer of dark loam, in similar relation- 

 ships, while at numerous points farthei north on Crowley's 

 Ridge, both in Arkansas and Missouri, there is a thin zone of 

 oxidized (red) loam, occupying a corresponding position. The 

 great majority of sections, however, present the aspect of con- 

 secutive deposition ; at least no positive signs of separate 

 stages of deposition have been observed.* 



The Gravels and Sands subjacent to the Loess. (" Orange 

 Sands."). — Beneath the loess, in the southernmost counties of 

 Illinois, in northern and northwestern Kentucky, in western 

 Tennessee, in northeastern Arkansas, and southeastern Mis- 

 souri, there is a remarkable series of gravels and sands. Jn 

 portions, at least, of this area, the gravels and sands have been 

 known in geologic literature under the name of Orange Sand. 

 Unfortunately for clearness of understanding, this term has 

 been differently used by different geologists. The Orange 

 Sand or Lagrange formation of Tennessee (Safford), is re- 

 garded by Professor Safford as the partial equivalent of Pro- 

 fessor Hilgard's Northern Lignitic, and is referred by both 

 geologists to the Tertiary, Safford regarding it as Miocene, 

 though expressing doubt whether it be not older, and Hilgard 

 regarding it as Eocene f The Bluff Gravels of Safford appear 

 to be the Orange 'Sand of Hilgard, and are classed by both 

 geologists as Quaternary. Within the area under considera- 

 tion, both the Lagrange or Orange Sands of Safford, and the 

 Bluff Gravels (Safford), or Orange Sands of Hilgard, occur, 

 and both are covered by loess. With the classification of these 

 formations, and with the question of the relations between the 

 Lagrange Sands and the Bluff Gravels, this article does not 

 deal. It has only to do with their pre-pleistocene age, and 

 with the relation of the loess to them. The Bluff Gravels 

 (Safford) occupy the surface (below the loess) of the river 

 bluffs at various points in Tennessee, while the Lagrange Sands 

 occupy the surface farther east. Farther north, however, 

 sands and gravels which appear to be the equivalent of the Bluff 

 Gravels of Tennessee, have a much greater thickness than 

 in the latter state, and it is not altogether clear that they 

 do not include beds below the Bluff Gravels of Safford. Be 

 that as it may, the gravels have a much greater vertical range 

 in Southern Illinois than has been observed by the writers 

 further to the south. The Bluff Gravel formation ''consists 



* See further the foot note at the close of the article, p. 377. 

 \ This Journal, vol. xli. page 370, 1864. 



