U.S. Geological Survey resource assessment of selected Tertiary coal zones in Wyoming, Montana and North Dakota

In 1999, 1 Gt (1.1 billion st) of coal was produced in the United States. Of this total, 37% was produced in Wyoming, Montana and North Dakota. Coals of Tertiary age from these states typically have low ash contents. Most of these coals have sulfur contents that are in compliance with Clean Air Act standards and most have low concentrations of the trace elements that are of environmental concern. The U.S. Geological Survey (USGS) National Coal Resource Assessment for these states includes geologic, stratigraphic, palynologic and geochemical studies and resource calculations for major Tertiary coal zones in the Powder River, Williston, Greater Green River, Hanna and Carbon Basins. Calculated resources are 595 Gt (655 billion st). Results of the study are available in a USGS Professional Paper and a USGS Open-File Report, both in CD-ROM format.