Bibliographic source: Geolndex lat-long search 



Author: Lemke, R.W. 



Title: Geologic map of the Great Falls Quadrangle, Montana. 



Series: USGS Geologic Quadrangle Map GQ-1414 



Date: 1977 



Map at scale of 1:62500 shows most of Benton Lake underlain by 

 glaciolacustrine sediments of glacial Lake Great Falls. These are 

 described as being as much as 100 feet in thickness in Benton Lake 

 area, and in Benton Lake area consist predominantly of a plastic 

 clay facies. Northern end of the lake is underlain by 

 undifferentiated alluvium and colluvium. 



The NW trending axis of the Sweetgrass Arch passes southwest of 

 Benton Lake, elevating a large area of the Bootlegger member of the 

 Blackleaf Formation in the southern part of the lake catchment. 

 Interbedded sandstone, siltstone and shale with several bentonite 

 beds. 



North of the lake, mapping shows till cover (described as up to 70 

 feet thick) overlying the Marias River Shale. Three of the four 

 members of the shale are described as calcareous at least 

 occasionally, minor siltstone and sandstone interbeds within the 

 Ferdig and Floweree members. 



No hydrologic information. Uppermost predictable aquifer is 

 probably the Kootenai Formation, underlying Blackleaf Fmn. 



Bibliographic source: U.S. Geological Survey office inquiry 



Author: Knapton, J.R. , W.E. Jones and J.W. Sutphin 



Title: Reconnaissance investigation of water quality, bottom 



sediment and biota associated with irrigation drainage in 

 the Sun River area, west-central Montana 



Series: U.S. Geological Survey Water-Resource Investigations report 

 87-4244 



Date: 1987 



This study included limited ground-water sampling in the 

 Greenfields Bench gravels, and water quality, bottom sediment and 

 biotic sampling of all of the Benton Lake pools. Ground water 

 quality analyses include a high-selenium seep near Benton Lake. 



