Coal Resources & Reserves
Coal Production & Mining
Coal Maps & Projects
Powder River Basin
Powder River Basin Coal Field
In the Powder River Basin coal field – the most prolific in the world – coal is
mined from two major coal seams, the Anderson and Canyon coals. This coal occurs
in the Paleocene-age (65 to 55 million years ago) Tongue River Member of the
Fort Union Formation. The mineable subbituminous coal seams in the Fort Union
Formation are 60 to 80 feet thick, with a moisture content between 20 and 30
percent, and contain less than 6 percent ash and 0.5 percent sulfur. Powder
River Basin (PRB) coal also extends into the Eocene-age Wasatch Formation, and exploration
drilling has encountered coal seams greater than 200 feet thick.
Coal is mined in the PRB at a rate of 12 tons per second, filling between 50 to
70 coal trains per day. Nine of the nation’s 10 largest coal mines operate in
the Wyoming part of the PRB. The largest coal mine is the Peabody Energy North
Antelope Rochelle Complex, which produced more than 107.6 million tons in 2012.
The PRB also has over 1,500 square miles of clinker rock. This is a layer of
reddish rock formed by baking of sediments above burned coal deposits.
Historically coal deposits exposed at the surface were ignited by lightening
strikes or brush fires and burned naturally underground and near the surface for
a period of hundreds of years. Recent age-dating suggests that these beds are
between 1.1 Ma to 10 ka in age (Heffern and others, 2007). These clinker beds are up
to 180 feet thick.
Rapid growth in Wyoming's coal industry during the latter part of the 1970s
resulted from the development of large-scale open-pit surface mines in the
Powder River Basin (PRB). Development of the abundant coal resources in the PRB was driven by amendments to the Clean Air Act of 1974 and the
crisis. The continuous growth of coal production in
Wyoming resulted from a growing national demand for low-cost, low-sulfer
steam-coal; from technological advances in engineering and mining practice; from
large-scale development of mining and rail infrastructure; and from the great
abundance of thick, mineable coal resources in the PRB.
The Peabody North Antelope Rochelle Mine and Arch Coal’s Black Thunder Mine
(Campbell County) are the two largest coal mines in the United States. Each mine
produces about 100 million tons annually. Combined, these two surface mines
produced nearly 22 percent of the nation’s coal, more
coal than the State of Kentucky produces annually.
PRB Coal Correlations and Coal Zones
Geophysical well logs are displayed in these cross section diagrams indicating the locations, names and thicknesses of coal seams in the PRB. Coal Correlations and Coal Zones in the Powder River Basin, Wyoming, Cross sections A-A’ through F-F’ (WSGS-2007-OFR 2007-03), can be purchased through the WSGS online catalog or viewed at the links below.
Chris Carroll (307) 766-2286 Ext. 243