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BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 19, pp. 339-346, PL. 20 NOVEMBER 2, 1908 



GIANT SPRINGS AT GREAT FALLS, MONTANA^ 



BY CASSIUS A. FISHER^ 



{Presented hy title before the Society December SI, 1907) 



CONTENTS 



Page 

 Introduction 339 



Geologic relations 34O 



Amount of flow 342 



Utilization 343 



Composition 343 



Source of the springs 344 



Introduction 



In the vicinity of Great Falls, Montana, there are some ver}' large 

 springs which present unique geologic features and an interesting ques- 

 tion as to the source of the water. These springs, which are locally 

 known as the Giant springs, are located on the south bank of Missouri 

 river, about 3 miles below Great Falls. They have a very large flow of 

 relatively pure water, winch appears at the surface through large joint 

 planes in a medium to coarse grained sandstone belonging to the Kootenai 

 (Lower Cretaceous) period. For a short distance on either side of the 

 main spring there are smaller springs flowing from the joint planes, and 

 directly opposite it, in the l)ed of Missouri river, there is another large 

 spring, which is only apparent during low water seasons. 



Previous workers in treating the geology of this region have made only 

 brief mention of the occurrence of these springs. They were first dis- 

 covered in 1804 by Captain Lewis, of the Lewis and Clark expedition,* 

 and in the diary of that early explorer they are described as "the largest 

 fountain in the United States." More recent observers in the field are 



1 Published by pei-mission of the Director of the U. S. Geological Survey. 



Manuscript received by the Secretary of the Society May l.S. 1008. 

 ' Introduced by C. W. Hayes. 

 » Lewis and Clarli expedition, 1804-1806. Coues, 4 vols., 189.3. 



XXXi'lI— Bull. Geol. Soc. A.m., Vol. 19, 1907 (339) 



