Soil Survey of Sweet Grass County Area, Montana - Soil Data Mart

10 Soil Survey
Creek, approximately 3 miles (5 km) south of the soil
survey area boundary. Prospecting for gold, silver,
and copper has occurred in this district since the
1900s; however, the majority of the mining was in the
1920s. Exploration for copper is ongoing in this area.
In the 1940s, optical-quality calcite was mined
from the upper Deer Creek drainage, 3 miles (5 km)
north of Iron Mountain, for use in bomb sights
manufactured by Norden for bomber aircraft. It was
also mined locally for chicken grits. Most of the
material was mined from veins cutting sedimentary
rocks of the Livingston Group, but these veins also
occur in the Livingston agglomerate unit. The calcite
was deposited into open fractures by rising, lowtemperature
hydrothermal solutions associated with
volcanic activity. The veins occupy faults and can be
up to 20-feet (6-m) thick and traceable for several
thousand feet.
The Big Timber District is several miles west of
Half Moon Campground and encompasses the
headwaters of Big Timber Creek in the Crazy
Mountains. It is a relatively small district and contains
gold, silver, lead, and copper. Exploration has
continued in this district sporadically from the 1920s
to the present.
Oil, Gas, and Coal
There are no producing oil- or gasfields in Sweet
Grass County at this time. There has been some
exploration over the years in the Crazy Mountains
Basin, and a total of 79 exploration holes were drilled
in the county between 1923 and 1992 (Montana
Board of Oil and Gas Conservation, 1995). Fortyeight
of these holes were dry; the rest had
noncommercial shows of oil and gas. The deepest
hole was drilled near Porcupine Butte in Section 6,
T. 5 N., R. 13 E., to a total depth of 11,800 feet
(3,597 m).
The Crazy Mountains Basin is composed of a very
thick accumulation of sedimentary rocks, estimated to
be nearly 30,000-feet (9,145-m) thick in the center of
the basin. These sediments contain a significant
amount of relatively porous sandstone. The basin is
considered to have moderate potential for oil and gas
development as there are mature petroleum source
strata present at depth; there is permeable rock
above the source strata that would allow petroleum
migration; and structures are present that are
normally associated with petroleum traps.
Unfortunately, the basin is structurally complex,
and gentle folding of the Tertiary rocks at the surface
obscures more complicated folding in the underlying,
older rocks. There are members of the oil and gas
industry who remain optimistic about this area;
however there is little ongoing exploration at this time.
There is a significant amount of federal land south
and northwest of Big Timber that has been leased to
private industry for energy exploration.
Small amounts of coal were mined from the Eagle
Formation, west of the Boulder River Road at Coal
Mine Rim, 3 miles (5 km) south of McLeod. There is
little published information about this mining; however
it is assumed that this mining took place in the late
1800s and early 1900s, at the same time as the
active coal mining in Cokedale, 25 miles (40 km) to
the west.
Geothermal Resources
The McLeod Basin in the southern end of the soil
survey area is approximately 45 miles (72 km)
northeast of Gardiner, Montana, and the entrance
to Yellowstone National Park. The park contains
the largest geothermal system in North America,
the Yellowstone caldera. There are no Known
Geothermal Resource Areas (KGRAs) designated
by the United States Department of the Interior in
Sweet Grass County, although there are several
thermal springs and wells.
These springs and wells include Hunter’s Hot
Springs, Anderson’s Spring near McLeod, and the
McLeod well. Hunter’s Hot Springs is an old resort
area that was closed in the late 1960s. It is currently
used to heat greenhouses. It has a reported flow
of 1,135 gpm (4,290 L/min) and a temperature of
138 degrees F (59 degrees C). Anderson’s Spring
at McLeod is currently undeveloped. It has a reported
flow of 75 gpm (280 L/min) and a temperature of
77 degrees F (25 degrees C). The geothermal well
at McLeod has a total depth of 2,250 feet (686 m). It
is reported to flow at 1,135 gpm (4,290 L/min), with
a temperature of 104 degrees F (40 degrees C).
Ground-Water Resources
The most productive water wells in Sweet Grass
County are developed from alluvial gravels along the
Yellowstone and Boulder River flood plains. North of
the Yellowstone River, quantities of water suitable for
stock and domestic use can be developed from
sandstone beds within the Fort Union Formation, the
Livingston Group, and the Hell Creek and Lennep
Formations. In the relatively flat-lying beds in the
Crazy Mountains Basin, well depth is partially
dependent on the topography and, particularly, on the