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).

ABSTRACT The geology of Great Smoky Mountains National Park (GRSM) in Tennessee and North Carolina is dominated by siliciclastics and metamorphic strata. However, in the western portion of GRSM, a series of carbonate fensters (windows) expose the Lower Ordovician–age section of the Knox Group, a series of dolomite and limestone units that are partially marbleized as a result of contact metamorphism from the Great Smoky fault. The fensters create opportunities for allogenic recharge to occur at points along the contact of the surrounding insoluble strata with the underlying soluble carbonates. The combination of chemically aggressive surface recharge and vertical relief has resulted in the formation of deep caves, many of which have active streams and water resources. Though the karst is limited in extent and the number of caves is fairly small, the significance of the resources is substantial, with several of the caves in the area over 150 m in depth and at least two being major bat hibernacula. In 2017, the U.S. Geological Survey (USGS) began a study to better understand the hydrologic behavior of these karst systems through hydrologic and geochemical monitoring, groundwater tracing using fluorescent dyes, and seepage runs. Stage and water-quality instrumentation was installed in two caves in GRSM, the main stream of Bull Cave, and in a sump pool in Whiteoak Blowhole, at 173 m and 70 m below land surface, respectively. Following setup of the cave sites, dye injections were conducted to determine discharge points for four of the deep cave systems on Rich Mountain and Turkeypen ridge. Results show water in these systems has an extremely rapid travel time, with tracers detected from caves to springs in less than 24 h for each of the systems. This field guide describes the complex geology, regional hydrogeology, and unique landscape characterized by high-gradient subterranean streams, carbonate fensters, and deep caves of the GRSM karst.