CLASSIFICATION OF ARKOSE DEPOSITS 443 



numerous higher horizons. It is. composed of subangular grains 

 of quartz and subangular grains and pebbles of feldspar in a fine- 

 grained matrix of argillaceous material. The color of the whole 

 formation is deep red, due to a heavy stain of ferric iron. Fossils are 

 rare in the formation. 



The following deposits are apparently of this type : 



Arkose of the Amnicon formation, pre-Cambrian, Wisconsin 

 Sugarloaf arkose (Triassic), Connecticut River area, Massachusetts and 

 Connecticut 



Stockton arkose (Triassic) , New York, New Jersey, Pennsylvania 

 Arkose of the Upper Carboniferous, Ottweiler, Rhine Province, Germany 

 Arkose of the Lower Rotliegendes, Rhine Province, Germany 

 Arkose of the Rotliegendes, Mainz Basin, Vosges Mountains and Black 



Forest, Germany 

 Arkose of the Old Red Sandstone, England 

 Arkose of the Cutler formation, Permian, Colorado(P) 1 

 Arkose of the Fountain and Lower Wyoming formations (Permian), 

 Colorado (P) 1 



(b) Deposits laid down under moist, chiefly temperate, condi- 

 tions of climate: Arkose grayish, composed of subangular grains 

 of quartz and of considerably decomposed feldspar in a matrix 

 of fine-grained quartz and argillaceous material, in most cases 

 carbonaceous, and in some cases carrying plant fossils; the arkose 

 commonly associated with coal deposits. 



The causes of a general erosion of the regolith in a region of 

 moist temperate climate are not completely evident. The sug- 

 gestion of the introduction of subglacial conditions as a possible 

 cause seems not well founded, since the several glacial epochs of the 

 Pleistocene do not seem to have caused a general erosion of the 

 regolith of the Piedmont belt to the south of the glaciated area. 

 It would seem reasonable to expect, furthermore, that the effect 

 of the change on the mantle of vegetation would be a replacement 

 of the temperate by arctic flora. The suggestion that a marked 

 increase in the amount of the rainfall might be a sufficient cause 

 would likewise seem not well founded, as an increase in the rainfall 

 characteristically results in more luxuriant vegetation, with a con- 

 sequent increase in the protective power of the mantle of vegetation. 



1 Commonly considered marine, but apparently very like the Newark beds of the 

 Connecticut River and the New York-New Jersey Triassi L,> reas. 



