Lithologies from geophysical logs and cores of 11 holes; 7 coal samples analyzed in the Castle Rock area. 54 pages. 1 plate (1:200,000). Digital PDF download. OF-83-02D
This publication is a companion to OF-81-08 Geophysical Logs from the 1981 Water Well Logging Program, Castle Rock (1/2° x 1°) Quadrangle.
As part of a program to evaluate coal resources of the quadrangle, the CGS conducted an exploratory coal drilling program to fill in gaps of information on coal quality. The holes were located primarily in two different areas—just west of the Buick-Matheson area, an area in which Laramie Formation coals are about 500 to 1,000 feet in depth and the Ramah-Fondis area, where lignite of the Denver Formation is generally at shallow depths. Since a scarcity of information is available on Laramie Formation coals beyond shallow depths, one goal of the drilling project was to obtain coal quality data on deeper Laramie coals. Further evaluation of the quality of shallow Denver Formation lignites was desired in certain areas; these holes were rotary drilled down through the Laramie Formation to obtain additional needed information on deeper Laramie coals.
Eleven holes were drilled and geophysically logged at eight drill sites with a coal suite (natural gamma, density, resistivity, and caliper) logging tool. Lithologies were compiled from interpretations of the drill cuttings, cores, and geophysical logs. Two samples were taken of Laramie Formation coal from two sites, and five samples were collected for Denver Formation coals from three sites. Analyses for these samples are included in the report.