Includes coal resource information, an isopach map of the Watkins Lignite Seam, and a map showing the extent of alluvial valley floors and overburden thickness above the Watkins Lignite Seam in Adams and Arapahoe Counties. 2 plates (1:50,000). Digital PDF download. OF-78-06D
Kirkham, Robert M. “OF-78-06 Isopach Map of the Watkins Lignite Seam and Map Showing Extent of Alluvial Valley Floors and Overburden Thickness Above the Watkins Lignite Seam, Adams and Arapahoe Counties, Colorado.” Coal Resources. Open File Reports. Denver, CO: Colorado Geological Survey, Department of Natural Resources, 1978. https://coloradogeologicalsurvey.org/publications/watkins-lignite-seam-overburden-isopach-map-adams-arapahoe-colorado.