Odell-Skull Creek RNA 



Climatic setting. The net annual precipitation balance for the 

 WET56 site (from the MAPS database) is -4 inches, ranking Odell- 

 Skull Creek near the middle of the moisture range shown for Rocky 

 Mountain sampling sites. The available low-elevation climatic data 

 are not considered directly relevant to this subalpine setting, 

 where water supply is probably derived mainly from winter snowpack. 



Geologic setting. The wetland and it's catchment are underlain by 

 bouldery till deposited on a glaciated surface formed on formations 

 of the Missoula Group, a subset of the Proterozoic-aged Belt 

 series. Areas to the west of the immediate catchment expose large 

 areas of Cretaceous and early Tertiary-aged intrusive rocks with 

 granitic and granodioritic compositions. The wetland is immediately 

 to the east of an area of chemical soil anomalies identified as a 

 potential mineral exploration target. 



Hydrologic type. The WET56 site (lower Skull Creek Meadows on 

 published maps) is a headwater area lacking discrete surface water 

 inflow, and having a distinct (perennial?) surface water outlet. 



Basin characteristics. The catchment to wetland area ratio ranks 

 mid-range in comparison to other Rocky Mountain sampling sites. 

 WET56 is situated on the downgradient in a series of two wetlands; 

 water storage in the upper wetland may influence the timing and 

 duration of water received by the WET56 site. No information on 

 ground-water behavior in the area is available. The site is 

 vegetated throughout, and the maximum free water depth inferred to 

 be shallow throughout the year. 



Water chemistry. Water in Skull Creek Meadows, as represented by 

 the WET56 sample, is very dilute, moderately acidic and sodium- 

 bicarbonate in composition. Mineral equilibria indicate highly 

 undersaturated conditions with respect to carbonate phases. 

 Nitrate and ammonium concentrations were both below reporting 

 limits; phosphorous concentrations were high in comparison to most 

 other Rocky Mountain sites, and the total organic carbon 

 concentration ranked mid-range within the site class. 



WET56 was one of the few Rocky Mountain sampling sites with 

 reportable boron and zinc concentrations. The copper concentration 

 was near the upper end of the range shown for Rocky Mountain sites, 

 and was exceeded mainly by sites with known mining impacts. The 

 arsenic concentration ranked mid-range within the site class. 



Chemical history. No other water chemistry data are known from this 

 site. Stream sediment samples for mineral exploration may have 

 been collected nearby. 



Sediments. The WET56 sediment sample contained a diverse array of 

 extractable trace elements. The vanadium concentration was among 



