Abstract The National Coal Resource Assessment (NCRA) team of the U.S. Geological Survey (USGS) has assessed the quantity and quality of coal beds and zones that could be mined during the next 20 years or more. Geologic, geochemical, and resource information was collected and compiled for the five major coal-producing regions of the United States: the Appalachian Basin, Illinois Basin, Northern Rocky Mountains and Great Plains, Colorado Plateau, and the Gulf of Mexico Coastal Plain, (Gulf Coast) (Figure 1). In particular, the NCRA assessed coal-quality information and characterized environmentally significant trace elements, such as arsenic and mercury, that are defined in and administered by 1990 Clean Air Act Amendments (U.S. Environmental Protection Agency, 1990). The results of various USGS coal assessment efforts may be found at: http://energy.cr.usgs.gov/coal/coal_assessments/index.html , and a summary of the results from all assessment areas can be found in Ruppert et al. (2002) and Dennen (2009). A more detailed assessment for the Gulf Coast region includes reviews of the coal geology, resource potential, and quality of coals in four areas (Figure 2A and other chapters of this volume). These areas selected for study (Figure 2A) are described in this report as: (1) the Sabine uplift in Louisiana

Abstract The Wilcox Group (Paleocene to Eocene) of the Sabine uplift, a structural arch in northeastern Texas and northwestern Louisiana (Figure 1), has lignite zones that approach subbituminous rank (see Chapter 4, this publication). These coals are among the highest quality resources known within the Gulf Coastal Plain because of their low ash yield and sulfur content. The surface expression of the Sabine uplift is defined by the contact between coal-bearing rocks of the Wilcox Group and overlying fluvial rocks of the Carrizo Sand, which is the basal unit of the Claiborne Group (Figures 2, 3). The Sabine uplift study area includes parts of Harrison, Marion, Nacogdoches, Panola, Rusk, Sabine, San Augustine, and Shelby Counties in Texas and Bossier, Caddo, De Soto, Natchitoches, Red River, and Sabine Parishes in Louisiana (Figure 1). Adjacent counties and parishes that include the subsurface Wilcox Group extend the regional Sabine uplift area. The Wilcox in the subsurface is underlain by the Midway Group (Figure 3), a mudstone-dominated marine sequence of Paleocene age. Quaternary alluvium and terrace deposits overlying the Wilcox Group at the surface are limited to areas of modern drainage. The total thickness of the Wilcox Group within the Sabine uplift area ranges from approximately 400 ft on outcrop to 2500 ft in subsurface (Kaiser, 1990). In a few places, the contact between the overlying Carrizo Sand and Wilcox Group is erosional, but in other places, the contact is gradational.

Abstract The surface exposure of the Paleocene Wilcox Group in northeast Texas varies in width from 9 to 27 mi along an arcuate outcrop that extends southwest approximately 156 mi from the Texas-Arkansas State line to 32° latitude. Parts of Bowie, Camp, Cass, Franklin, Henderson, Hopkins, Morris, Navarro, Rains, Titus, Van Zandt, and Wood Counties are included in this outcrop belt (Figure 1). This area forms the northwestern flank of the East Texas Basin (Figure 2), the axis of which separates northeast Texas from the Sabine uplift structural area. The Wilcox Group dips south and southeast at 2° or less toward the axis of the East Texas Basin, with the exception of local salt-dome structures and a transcurrent structural high that extends from Monticello to Martin Lake (Figure 1). The Wilcox Group conformably overlies the mudstone-dominated Midway Group, a marine unit of lower Paleocene age (Figure 3). In most of northeast Texas, the Wilcox is overlain and locally scoured by the Carrizo Sand of the Claiborne Group. Where the Car-rizo Sand is absent in extreme northeast Texas (Morris and Cass Counties, Figure 1), marine sandstone and mudstone deposits of the Reklaw Formation overlie the Wilcox Group (Figure 3). Holocene deposits overlie the Wilcox Group in areas of modern-day drainages. The thickness of the Wilcox Group in northeast Texas increases downdip from about 500 ft near the outcrop to approximately 2000 ft near the axis of the East Texas Basin

Abstract Coal deposits in the Wilcox Group of central Texas have been regarded as the richest coal resources in the Gulf Coastal Plain. Although minable coal beds appear to be less numerous and generally higher in sulfur content (1 percent average, as-received basis; table 1 ) than Wilcox coal deposits in the Northeast Texas and Louisiana Sabine assessment areas (0.5 and 0.6 percent sulfur, respectively; table 1 ), net coal thickness in coal zones in central Texas is up to 32 ft thick and more persistent along strike (up to 15 mi) at or near the surface than coals of any other Gulf Coast assessment area. The rank of the coal beds in central Texas is generally lignite (table 1 ), but some coal ranks as great as subbituminousC have been reported (Mukhopadhyay, 1989). The outcrop of the Wilcox Group in central Texas strikesnortheast, extends for approximately 140 mi between the Trinity and Colorado Rivers, and covers parts of Bastrop, Falls, Freestone, Lee, Leon, Limestone, Milam, Navarro, Robertson, andWilliamson Counties (Figure 1 ). Three formations, in ascending order, the Hooper, Simsboro, and Calvert Bluff, are recognized in central Texas (Figure 2 ). The Wilcox Group is underlain conformably by the Midway Group, a mudstone-dominated marine sequence, and is overlain and scoured locally by the Carrizo Sand, a fluvial unit at the base of the Claiborne Group.

Abstract Coal deposits of the undivided Wilcox Group and its southern equivalent Indio Formation (Paleogene) of south Texas are among the coal resources that are not evaluated quantitatively in the current Gulf Coastal Plain coal re-source assessment. South Texas Wilcox and Indio coals have not been extensively mined, nor have they been mined commercially for at least the past 60 years. These coals constitute only about 1 percent of the demonstrated coal resources within the Texas Gulf Coastal Province. In contrast to the Wilcox coal resources of the assessed areas of the Sabine uplift of Texas and Louisiana, and of northeast Texas and central Texas (see Warwick et al., 2011a, b, c), Wilcox and Indio coal beds of south Texas are few in number, each generally less than 5 ft thick, and highly discontinuous. Furthermore, analytical data indicate that the sulfur content and ash yields of south Texas Wilcox and Indio coals generally exceed those of other Texas coals. Although these and other factors preclude the likely development of Wilcox or Indio coal resources in the near future, the comparatively elevated rank of these deposits has attracted recent interests related to coalbed methane production (SanFilipo, 1999; Warwick et al., 2002a, 2007b). The south Texas coal area is defined by the Colorado River to the northeast and the Rio Grande to the southwest and occurs within the Rio Grande Embayment (Figure 1). The youngest Tertiary coal-bearing rocks of this region occur sporadically

Abstract Near the Barents Sea coast in northern Timan, turbidites of probable Neoproterozoic age are intruded by pre-tectonic dolerites and a major suite of gabbros, granites and syenites (some nepheline bearing). Zircon ion microprobe dating of three plutons has yielded well-defined ages of 613–617 Ma. This alkaline igneous activity apparently represents a final phase of Vendian extensional magmatism prior to Timanian Orogeny. Previous work on late to post-orogenic calc-alkaline granites in the basement beneath the Pechora Basin, three hundred kilometres towards the SE, has yielded c. 550–560 Ma single zircon Pb-evaporation ages. These compositionally different intrusive suites are inferred to constrain the main phase of Timanian Orogeny to c. 610–560 Ma.

Abstract Near the Barents Sea coast in northern Timan, turbidites of probable Neoproterozoic age are intruded by pre-tectonic dolerites and a major suite of gabbros, granites and syenites (some nepheline bearing). Zircon ion microprobe dating of three plutons has yielded well-defined ages of 613–617 Ma. This alkaline igneous activity apparently represents a final phase of Vendian extensional magmatism prior to Timanian Orogeny. Previous work on late to post-orogenic calc-alkaline granites in the basement beneath the Pechora Basin, three hundred kilometres towards the SE, has yielded c. 550–560 Ma single zircon Pb-evaporation ages. These compositionally different intrusive suites are inferred to constrain the main phase of Timanian Orogeny to c. 610–560 Ma.

Abstract 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.

Abstract This review of the lignite deposits of western Tennessee and the Jackson Purchase area in western Kentucky (Figure 1) is an updated report on part of the U.S. Geological Survey's National Coal Resource Assessment of the Gulf Coastal Plain Coal Province (see Ruppert et al., 2002 ; Hackley et al., 2006 ; Dennen, 2009 ; and other chapters of this publication). Lignite deposits of western Kentucky and Tennessee are an extension of the Gulf Coastal Plain Coal Province ( Cushing et al., 1964 ), and currently are not economic to mine. These deposits have not been extensively investigated or developed as an energy resource. This review includes a description of the geology of the lignite-bearing units, a discussion of the available coal quality data, and information on organic petrology. Palynological data for lignite samples collected in Kentucky and Tennessee as part of this work are presented in Table 1. Lignite trace element data originally presented in Hackley et al. (2006) are not included in this report due to potential laboratory quality control issues during the time the samples were analyzed ( U.S. Geological Survey Energy Resources Program, 2010 ).