Eocene Yegua Formation (Claiborne Group) and Jackson Group Lignite Deposits of Texas
Robert W. Hook, Peter D. Warwick, Sharon M. Swanson, Paul C. Hackley, 2011. "Eocene Yegua Formation (Claiborne Group) and Jackson Group Lignite Deposits of Texas", Geologic Assessment of Coal in the Gulf of Mexico Coastal Plain, Peter D. Warwick, Alexander K. Karlsen, Matthew Merrill, Brett J. Valentine
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The lignite deposits within the upper Eocene Yegua Formation (Claiborne Group) and the overlying Jackson Group are among the coal resources that were not quantitatively assessed as part of the U.S. Geological Survey's (USGS) National Coal Resource Assessment (NCRA) program in the Gulf Coastal Plain coal province. In the past, these lignite-bearing stratigraphic units often have been evaluated together because of their geographic and stratigraphic proximity (Fisher, 1963; Kaiser, 1974; Kaiser et al., 1980; Jackson and Garner, 1982; Kaiser, 1996) (Figures 1, 2). The term “Yegua-Jackson trend“ is used informally herein for the lignite-bearing outcrops of these Late Eocene deposits in Texas. Lignite beds in the Yegua-Jackson trend generally are higher both in ash yield and sulfur content than those of the underlying Wilcox Group (Figure 2). Recent studies (Senkayi et al., 1987; Ruppert et al., 1994; Warwick et al., 1996, 1997) have shown that some lignite beds within the Yegua-Jackson trend contain partings of volcanic ash and host elevated levels of trace elements that have been identified as potentially hazardous air pollutants (HAPs) in the United States Clean Air Amendments of 1990. Lignite beds within the Yegua Formation are thin (less than or equal to 6 ft) and laterally discontinuous in comparison with most Wilcox Group deposits (Ayers, 1989a); in contrast, the Jackson Group lignite beds range up to 12 ft in total thickness and are relatively continuous laterally, extending nearly 32 mi along strike.
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Geologic Assessment of Coal in the Gulf of Mexico Coastal Plain
This publication is the fifth in a searies of reports by the U.S. Geological Survey on the assessment of the quantity and quality of the nation's coal deposits that potentially can be mined during the next few decades. For eight years (1995-2003), geologic, geochemical, and resource information was collected and compiled for the five major coal-producing regions of the United States. This volume contains the assessment results for the Gulf of Mexico Coastal Plain region. The contents of this volume were compiled mainly during the 8-year period mentioned above. However, every effort has been made to update the references and text to incorporate new work that has been completed since the original compilation period.