BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 10, pp. 245-252 APRIL 17, 1899 



LOESS DEPOSITS OF MONTANA 



Tby n. s. shaler 



{Presented before the Society December SO, 1898) 



CONTENTS 



Page 



Fields of observation 245 



Conditions determining formation of loess . . 246 



Effects of loess on streams 246 



Stratigraphic relationships and age of the loess 247 



Influences affecting formation of loess 249 



Vegetation 249 



Fires ' 249 



Irrigation 249 



Remedies for injurious effects of loess-forming 250 



Summary of conclusions 250 



Fields of Observation 



In examining certain deposits containing alluvial gold which lie on the 

 upper waters of the Missouri, in the state of Montana, my attention has 

 been called to the occurrence of accumulations of loess now in process 

 of formation. So far as their extent or depth is concerned, these layers 

 of wind-blown material are hardly worthy of remark ; but they have a 

 peculiar value as indices of certain alterations of climate which have oc- 

 curred in relatively recent times, and they are, moreover, agents of change 

 in the regimen of the streams of that district. The facts which are here pre- 

 sented were gathered mainly in the district bordering on the Ruby river, 

 commonly designated on the maps as the Stinking Water, a branch of the 

 Jefferson, on the upper reaches of the Missouri, near Helena, and in the 

 Butte district. Incidentally, notes were made in other parts of Montana 

 and in Utah. The greater portion of the information was obtained in 

 the old placer washings of Alder gulch, a tributary of the Ruby, and 



XXXVI— Bull. Geol. Soc. Am.; Vol. 10, 1898 (245) 



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