192 WANLESS— LITHOLOGY OF WHITE RIVER SEDIMENTS. 



courses of old stream channels can often be traced clearly, sometimes 

 by the crest of a high divide, sometimes by a marked ridge of sand- 

 stones across a modern creek valley. 



(2) Fresh-water limestone deposits. These occur at various 

 horizons through the Titanotherium and Oreodon beds and represent 

 small pond or damp meadow deposits. 



(3) Sheet-flood deposits. These constitute the bulk of the sedi- 

 ments of the Badlands and are normally clays not thoroughly consoli- 

 dated, except where they have been old land surfaces for considerable 

 periods, and have given rise to nodular or " caliche " beds by the 

 drawing up of ground water to the surface where it evaporates, leav- 

 ing its mineral content as a cement for the clays. 



(4) Volcanic ash beds. The term " Leptauchenia Clays " is in- 

 appropriate, as the Leptauchenia beds consist essentially of pumice 

 and volcanic glass fragments, connected with the eruptive action of 

 the Cordilleran district during its Tertiary orogenesis. That this ash 

 is probably wind-carried and water-laid, or, at least, reworked by 

 water into essentially horizontal beds of sheet-flood deposition, is the 

 conclusion reached from the strongly marked horizontal bedding of 

 these beds, and the absence of cross-bedding. 



(5) Eolian deposits. There are few traces of wind-blown sands 

 in the White River in the area investigated, but one bed has been 

 found in the lower part of the Leptauchenia series in the Sheep 

 Mountain section which seems to be mainly a dune sand, and the 

 sands of the Rattlesnake Butte sand calcite locality are apparently of 

 dune origin, as described by the writer in another paper.^ 



These various types of deposition may now be discussed in some- 

 what greater detail. 



The Channel Sandstones. 



Numerous typical sandstones from Titanotherium, Metamynodon, 

 and Protoceras channels were examined. The amount of calcareous 

 cement varied from 14 to 39 per cent., averaging about 25 per cent. 

 In one sample of coarse Titanotherium sandstone, in addition to 26 

 per cent, of calcareous cement, the grains were found to be embedded 

 in a matrix of chalcedony which may have constituted 10 or 15 per 



8 American Mineralogist, Vol. 7, No. 5. May, 1922. 



