Compiled by Raymond E. Lowrie, U.S. Bureau of Mines (1966), and revised by Roger B. Colton, U.S. Geological Survey, assisted by Harold R. Fitch, 1972.
In the revision of this map, many mine maps and two unpublished general small-scale maps of the area by F. H. Canis (deceased) and Samuel Tescher (deceased) were used. Much information was obtained orally from Louis A. Gaz, Consulting Engineer, Lafayette, Colorado. Faults shown are from published and unpublished geologic maps of the Erie, Frederick, Lafayette, and Louisville quadrangles by Frank D. Spencer (1961), U.S. Geological Survey; from field work by Colton, and from many large-scale unpublished mine maps loaned by Louis Gaz.
Users of this map should consult copies of the large-scale mine maps in the Office of the Colorado State Coal Mine Inspection Group for exact outlines of mined-out areas. Areas affected by collapse over mined-out areas may be larger than limits of mine workings. Depth to mined coal increases generally from west to east and ranges from zero at the outcrop to as much as 500 feet. Boundaries of workings should be verified by drilling. Shafts and drifts are only approximately located, and some may not be shown.
