Abstract Karst science is beginning to recognize and understand better the interaction between conduits and the fractures and/or pore spaces within the aquifer. The relationship has important significance in relation to the understanding of contaminant transport, resource management and dewatering practices. This study presents the results of a dye trace carried out to investigate the link between the aquifer and conduits near a large dewatered quarry in the Mendip Hills in Somerset, England. At the point of undertaking the study, there were no records of the quarry directly intercepting any conduits but water from the conduit(s) is known to be drawn into the quarry. During the study, water from the conduits was observed to be lost to and gained from the fractures in different places in the aquifer. This complexity highlights the dependence of conduit flow on water levels in the aquifer and the sensitivity of groundwater in karstified aquifers to contamination.

ABSTRACT The Mitchell Plateau of south-central Indiana is one of the iconic karst landscapes of the United States. The sinkhole-dimpled forests, fields, and farms; the extensive cave systems; and the deep windows into the groundwater system have fostered curiosity, exploration, and publication since the mid-1800s. This paper is designed to complement a field excursion to the classic features of this landscape. Included are literature reviews focused on three karst basins of the Mitchell Plateau: Mill Creek–Mosquito Creek, Bluespring Caverns, and Lost River. Geomorphic, hydrologic, and geochemical data are synthesized in the modern context of our understanding of epigenetic karst. Revealed are three styles of karst basin: (1) small, shallow karst aquifers strongly controlled by meteoric recharge and epikarst percolation; (2) intermediate-size karst aquifers with significant base flow and surface-water–groundwater interaction; and (3) regional aquifer systems with outcrop belt recharge, downdip transport into confinement with long water-rock interaction times, and artesian flow or entrainment of mineralized waters through fractures into springs or surface waters. Quaternary glaciation has greatly influenced the vertical position of base level through river incision and sediment aggradation; conduit development is controlled by proximity to the major rivers and the stratigraphic position of conduits.

ABSTRACT Limestone provides many lessons about Earth’s systems (geosphere, hydrosphere, atmosphere, cryosphere, and biosphere) through the geochemical, hydrologic, ­tectonic, and rock cycles. Limestone is ideal for teaching cross-disciplinary STEM (science, technology, engineering, and math) subjects of biology, chemistry, and physics, along with history and culture through its uses in society as a valuable economic resource. Carbon and calcium chemistry is part of the everyday environment, and limestone deposits around the world are important archives of biotic and abiotic Earth history. Limestones provide data for reconstructing global climate change and provide important “documents” for recreating Earth’s changing biodiversity throughout geologic time, including human history. Limestone precipitation is Earth’s antidote to global warming. Limestone is volumetrically one of our most valuable natural resources with a variety of uses, as well as frequently involved with natural and human-induced environmental hazards. Limestone is a common commodity readily available to all teachers and students, thus it is the ideal material for ­budget-strapped STEM educators to use to address Next Generation Science Standards. Some uses include: using fossils to develop concepts of paleoecology and evolution; using limestones to reconstruct ancient geography (including plate tectonics); and addressing the relevance of limestone to our society as a building stone, for its medical uses, and as a potential hazard associated with karst (caves and sinkholes). Five cross-disciplinary content concepts are addressed to aid teachers in preparing limestone-centric instruction: (1) enhancement of the understanding of chemical reactions and geochemical cycles, (2) biological evolution, (3) physics applications, (4) economic and environmental impacts, and (5) historical and fine arts’ use of limestone.

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.

ABSTRACT Hotspots represent the ephemeral introduction of nutrients into an environment, and occur in both the modern and geologic past. The annual deposition of deciduous leaves in temperate forests, tree falls, animal excrement, and vertebrate carcass deposition all result in the pulsed introduction of nutrients to an ecosystem. Hotspots are critical for providing limiting nutrients, including nitrogen and carbon, to be incorporated into soil microbial biomass and plant biomass. For vertebrate ­carcasses, following the release of labile compounds from soft tissues, bones are often left behind, and provide a more recalcitrant reservoir of organic carbon and nitrogen, phosphorus, calcium, and, in some environments, water, for micro- and macro-fauna. Taphonomy—the physical, chemical, and biological processes following plant or animal death—studied in modern systems can be used to interpret hotspot processes operating in the past. East Tennessee is a region where studies of modern and fossil vertebrate hotspots have provided new insights into taphonomy. This guide describes two hotspot localities in east Tennessee—the Miocene-aged Gray Fossil Site in Gray, Tennessee, and the Anthropology Research Facility (“the Body Farm”) at the University of Tennessee, Knoxville, a human decomposition experimental site. The goal of this interdisciplinary field guide is to provide a view of nutrient hotspots from their formation in the modern to their preservation over geologic time.

Abstract Sinkholes are the main hazard related to underground voids of both natural and anthropogenic origin. Instabilities developing underground may propagate upwards in a dramatic manner and reach the surface in the form of a sinkhole. The Apulia region in southern Italy is an interesting case study due to the outcropping of soluble rocks throughout the region. These rocks are affected by karst processes and have a high number of anthropogenic cavities. The latter were excavated by humans at different times for a variety of purposes. The worrying recent increase in the number of sinkhole events registered in Apulia led us to collect information on natural and anthropogenic sinkholes in Apulia. We focused on anthropogenic cavities, mostly excavated in Plio-Pleistocene calcarenites, and characterized the rock masses before using two- and three-dimensional parametric numerical analyses to model the instability processes, with the aim of exploring the failure mechanisms that lead to the occurrence of sinkholes. The parametric studies allowed us to carry out a preliminary evaluation of the stability conditions through simple charts designed for use in the field.