(lots of Bearpaw, Judith River and Eagle Formations) and regional 

 structure. These are the only usefulness of this map. 



Bibliographic source: Montana Bureau of Mines and Geology 

 Publications Index 



Author: Feltis, R.D. 



Title: Hydrogeologic map of the Billings 1 degree X 2 degree 

 quadrangle and vicinity, Montana 



Series: MBMG Hydrogeologic Map 9 A-F 



Date: 1988 



Regional compilation at 1:250,000 scale emphasizes outcrop 

 distribution and structural contouring, with Stiff diagrams of 

 water chemistry for different aquifers found within the quadrangle. 

 The Big Lake topographic basin is shown to be along the eastern 

 limb of the Lake Basin anticline, a hydrocarbon trap penetrated by 

 numerous oil and/or gas wells. The Lake Basin anticline is shown 

 intersecting the Lake Basin Fault Zone in the vicinity of Halfbreed 

 Lake. 



Mapping shows the Big Lake area to underlain by rocks above the 

 base of the Eagle Sandstone (Map 9E) and below the base of the 

 Lennep Sandstone (Map 9F). Surface of Bearpaw Shale is implied, 

 but not shown as outcrop. (Bearpaw Formation is shown by Ross, 

 Andrews and Witkind (1955) at 1:500,000 scale.) 



Stiff diagrams (Map 9E) indicate nearby analyses of the Virgelle 

 sandstone (of the Eagle Formation), the uppermost consolidated 

 aquifer in the area, exceed 2000 mg/1 TDS and are sodium chloride 

 or sodium bicarbonate/chloride in composition. (The analyses 

 displayed probably reflect mainly oilfield waters.) 



Big Sandy DOT Mitigation Wetland 



Bibliographic Source: Geoindex lat-long search 



Author: Lindvall, R.M. 



Title: Geology of the Big Sandy Quadrangle, Montana 



Series: USGS Miscellaneous Geologic Investigations Map 1-130 



Date: 1956 



