Some important geologic features may influence the results of this study. With 

 the use of a detailed geologic map (Bell 1952), a comparison of fault lines with stream 

 locations and strike and dip information with contour lines explains the occurrence of 

 the contact zone in the Halfway Creek drainage. Prevailing winds move considerable 

 snow out of the Halfway Creek drainage. Springs, fed by the large accumulation of 

 snow in the cirque basin immediately to the east and from seepage along the fault zone, 

 return some of this moisture to the Halfway Creek drainage. 



Soils are generally coarse textured, immature, rocky, and shallow. Parent mate- 

 rial was disintegrated in place by frost action and the resulting surface material in 

 the trenched area is approximately 7 feet thick. 



Vegetation 



Halfway Creek drainage may be divided into five major vegetation zones (fig. 4). 

 Aspen {Populus tremuloides ) occupies the wetter sites along stable stream courses just 

 below the contact zone. Adjacent to the aspen, on slightly drier sites, are the 

 ceanothus {Ceanothus velutinus ) and mixed browse (Amelanohier utahensis , Prunus virgin- 

 ■uzruXj Symphoriaarpos sp., Alnus tenuifolia) zones. The ceanothus and mixed browse 

 zones form dense thickets of brush with little understory. The two are separated 

 because ceanothus completely dominates sites on which it occurs and forms a much 

 shorter type of cover. Along the upper ridges and drier midslopes, two species of 

 sagebrush (Artemisia tvidentata^ and Artemisia soopulorum) predominate. A variety of 

 grasses and forbs form the ground cover. 



Figure 4. — Halfway Creek 



drainage showing five 

 ' major vegetation zones. 



5 



