STUDY AREA 



The study area consists of BLM-administered lands in Carter County, in the southeastern comer of 

 Montana. BLM holdings comprise the largest portion of federal lands in the county, and are 

 surpassed in total acreage by private lands. BLM lands are concentrated in the southwestern 2/3 of 

 the county in relatively remote rangelands. The more accessible and productive bottomlands are in 

 private ownership. Other public lands include three Custer National Forest units (Chalk Buttes. 

 Ekalaka Hills, and Long Pines of the Sioux District), that represent most of the forested uplands and 

 the largest escarpments in the county. Montana State lands, including most sections 16 and 36, are 

 scattered across the county (Figure 1 ). 



Carter County has some of the most extensive range landscapes in the state. It had 89% rangeland in 

 the 1970's; one of the twelve Montana counties with over 80% rangeland in the most detailed of 

 recent land use surveys (USDA NRCS/SCS 1976). Most BLM lands in the county are within 

 grazing allotments and are actively grazed. The primary ranching economy includes both cattle and 

 sheep grazing. The history of grazing in the county dates to the early 1880's. More localized 

 industries include bentonite mining on public and private lands in the southeast, logging in the 

 Custer National Forest imits in the north, and farming on private lands. 



Geology and Landforms 



The Carter County landscape is characterized by low relief rolling sedimentary plains dissected by 

 numerous drainages and dotted by weather-resistant sandstone or scoria-capped upland buttes and 

 tablelands. The County lies within the Missouri River watershed. Most rivers flow in a northeasterly 

 direction, including the Little Missouri River and its tributary Box Elder Creek. A limited area on the 

 western edge of the county drains west to the Powder River. Tributary streams and the dominant 

 ridge systems have a general northwest/southeast trend resulting in a predominance of southwest and 

 northeast aspect slopes (Figure 2). 



The open plains are made up of nearly level, horizontal Cretaceous formations, mostly shales and 

 claystones. The most extensive are the Pierre Shale members and the most restricted is the Mowry 

 Shale on the state line west of Alzada (Ross et al. 1955). Within some shale areas that are vast 

 expanses of thin-soil, low productivity calcareous shales and clay stone, are major outcrops of 

 bentonite, a shrink-swell clay product of weathered volcanic ash. The forested escarpments and 

 buttes are remnants of Tertiary sandstone formations. Scattered areas of badlands and river/stream 

 breaks occur along Box Elder Creek and the Little Missouri River. The alluvial deposits are best 

 developed along the Little Missouri River and certain tributaries including Willow and Thompson 

 Creeks, as well as along the Boxelder Creek. 



Soils 



Dominant soils in the southwestern 2/3 of Carter County, where BLM lands are concentrated, are 

 described as predominantly clayey entisols and aridisols (USDA Soil Conservation Service 1978). 



