Since 1979, the U.S. Geological Survey (USGS) has funded cooperative programs with coal-bearing states in an effort to provide current U.S. coal resource estimates that are calculated by uniform, computerized methods. As part of this program, near-surface lignite resources in Texas were estimated using the National Coal Resources Data System (NCRDS) and three software programs: PACER, VLATLONG, and GARNET. Resources of the aggregate coal in each borehole were calculated using the total-coal method. Measured, indicated, and inferred near-surface resource estimates in USGS thickness categories were calculated for the Paleocene-Eocene Wilcox Group in the east-central, northeast, and Sabine Uplift geographic regions of Texas. Total NCRDS-estimated resources are 28,000 million tons (25,000 million t). East-central Texas, which contains 47 percent of the total measured and 38 percent of the total indicated Wilcox resources, is the most lignite-rich area in the state.
Kaiser and others (1980) estimated near-surface Wilcox resources using the same data base as that used by the NCRDS method. For Texas resource categories, the NCRDS inferred resource value is 61 percent of the total NCRDS Wilcox estimate; the inferred resource value calculated by Kaiser and others (1980) constitutes only 8 percent of their total resource estimate. These dissimilar values result from two different methods of resource calculation. The NCRDS method is objective and therefore can be applied to many coal-bearing regions by people with varying levels of geologic expertise. The method uses resource circles that have constant dimensions and allows improved comparison of estimates from different states. Kaiser and others' (1980) method is subjective and requires considerable geologic expertise to extrapolate resource limits beyond known deposits. Although Kaiser and others' method requires geologic mapping in each coal-bearing region, it provides a more flexible and accurate resource estimate.