Preliminary description of cores, chemical analyses of lignite beds, and map showing locations of holes drilled in Grant, Hettinger, Morton, and Stark Counties, North Dakota

Nineteen exploratory holes were drilled in Grant, Hettinger, Morton, and Stark Counties, N. Dak. (fig. 1), for the U.S. Geological Survey from June 7 to September 15, 1966. This prospect drilling was undertaken to gather data on the thickness, quality, and extent of lignite beds and the lithologic characteristics of the rocks in the Sentinel Butte and Tongue River Members of the Fort Union Formation. This information is in support of geologic mapping and as part of a program of mineral land classification. A preliminary lithologic description of the cores, drill samples, and chemical analyses of the lignite beds sampled in each hole, drill samples, and chemical analyses of the lignite beds sampled in each hole are given.

Partial core and drill samples of the 19 holes drilled may be inspected at the North Dakota Geological Survey, Grand Forks, N. Dak.