Title: 



Series : None 

 Date: 



Bibliographic source: Geoindex lat-long search 



Author: Mudge, M.R. , R.L.Earhart, J.W.Whipple, and J.E. Harrison 



Title: Geologic and structure map of the Choteau 1 degree X 2 

 degree quadrangle, western Montana 



Series: U.S. Geological Survey Miscellaneous Investigations Series 

 Map 1-1300 



Date: 1982 



Regional compilation of bedrock geology at 1:250,000 scale shows 

 Monture Hill outcrops in the immediate vicinity of Lahrity Lake to 

 be the Snowslip Formation of Proterozoic Y (Belt) age. The 

 snowslip Formation is described as interbedded argillite and 

 siltite with minor fine-grained quartzite, pebble conglomerate and 

 oolitic limestone. 



Probable source areas for surficial glacial sediments in the 

 Monture Creek drainage are shown as underlain by Belt Series 

 sediments ranging from the Spokane Formation to the McNamara 

 Formation, including large areas of the dominantly carbonate Helena 

 Formation. 



Between Monture Hill and the mountain front to the north, mapping 

 shows several small patches of exposed valley-fill sediments ("lake 

 beds") of mid to late Tertiary (Oligocene to Miocene) age. 

 Elsewhere, Tertiary sediments are covered by glacial drift. 

 Tertiary sediments are described as variable but dominantly fine- 

 grained in character, locally calcareous and locally fossilif erous. 

 In the Upper Blackfoot (Lincoln) area, similar sediments are 

 described as pyritic. [See Indian Meadows entries.] 



Lahrity Lake Southwest 

 See Lahrity Lake entries. 



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