Series: USGS Miscellaneous Field Studies Map MF-1342-A 

 Date: 1982 



Very good 1:50,000 scale map of the geology of the Centennials, but 

 includes little mapping of the surficial deposits in the valley. 

 Only the fan deposits along the mountain front are shown. 

 Centennial scarp is mapped showing formations ranging from 

 undivided Precambrian basement rocks up to Jurassic undivided near 

 the divide. 



Upper Stillwater River Wetland 



Bibliographic source: Geoindex lat-long search 



Author: Elliot, J.E. 



Title: Geologic map of the southwest part of the Cooke City 

 Quadrangle, Montana and Wyoming. 



Series: U.S. Geological Survey Miscellaneous Investigations Series 

 Map 1-1084. 



Date: 1979 



Detailed bedrock geologic mapping at 1:24000 shows the Upper 

 Stillwater wetland underlain by Holocene-aged alluvium, which 

 overlies an extensive area of undifferentiated Pleistocene-aged 

 glacial deposits. No descriptions of the characteristics or 

 thickness of the surficial geologic units is provided. 



Glacial sediments upgradient from the sampling site cover 

 sedimentary rocks of Cambrian age (including the calcareous Meaghar 

 and Pilgrim Limestones) and silicic to intermediate volcanic rocks 

 (rhyodacite and latite) of early Tertiary (Eocene) age. Daisy 

 Creek, an eastern tributary to the upper Stillwater River receiving 

 acid mine drainage from the historic McLaren Mine, incises the 

 glacial cover and exposes the Cambrian formations along it's upper 

 channel . 



The western margin of the wetland (as indicated by the extent of 

 Holocene alluvium) and the upper Stillwater River above the 

 sampling site are shown closely following a normal fault 

 (downdropped to the east) which may exert some structural control 

 on the drainage. 



69 



