from The American Heritage® Dictionary of the English Language, 4th Edition
- n.pl. Geology A stratigraphic unit equivalent to the Pennsylvanian or Upper Carboniferous Periods.
- n.pl. Geology Strata of the Carboniferous Period usually containing coal deposits.
from the GNU version of the Collaborative International Dictionary of English
- n. A subdivision of the carboniferous formation, between the millstone grit below and the Permian formation above, and including nearly all the workable coal beds of the world.
from The Century Dictionary and Cyclopedia
- In geology, that portion of the Carboniferous series in which beds of coal are found.
- In America and Great Britain a special significance attaches to this term in geological classification. In Pennsylvania the coal-measures are those strata which carry the productive coal-beds of Carboniferous age and all deposits intercalated between them, and they are divided into lower productive, lower barren, and upper productive measures. The coal-measures, with the millstone-grit at their base, constitute the upper division of the Carboniferous system. In Great Britain and on the Continent their relations are similar.
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