Abstract Burnsville Cove in Bath and Highland Counties (Virginia, USA) is a karst region in the Valley and Ridge Province of the Appalachian Mountains. The region contains many caves in Silurian to Devonian limestone, and is well suited for examining geologic controls on cave location and cave passage morphology. In Burnsville Cove, many caves are located preferentially near the axes of synclines and anticlines. For example, Butler Cave is an elongate cave where the trunk channel follows the axis of Sinking Creek syncline and most of the side passages follow joints at right angles to the syncline axis. In contrast, the Water Sinks Subway Cave, Owl Cave, and Helictite Cave have abundant maze patterns, and are located near the axis of Chestnut Ridge anticline. The maze patterns may be related to fact that the anticline axis is the site of the greatest amount of flexure, leading to more joints and (or) greater enlargement of joints. Many of the larger caves of Burnsville Cove (e.g., Breathing Cave, Butler Cave-Sinking Creek Cave System, lower parts of the Water Sinks Cave System) are developed in the Silurian Tonoloway Limestone, the stratigraphic unit with the greatest surface exposure in the area. Other caves are developed in the Silurian to Devonian Keyser Limestone of the Helderberg Group (e.g., Owl Cave, upper parts of the Water Sinks Cave System) and in the Devonian Shriver Chert and (or) Licking Creek Limestone of the Helderberg Group (e.g., Helictite Cave). Within the Tonoloway Limestone, the larger caves are developed in the lower member of the Tonoloway Limestone immediately below a bed of silica-cemented sandstone. In contrast, the larger caves in the Keyser Limestone are located preferentially in limestone beds containing stromatoporoid reefs, and some of the larger caves in the Licking Creek Limestone are located in beds of cherty limestone below the Devonian Oris-kany Sandstone. Geologic controls on cave passage morphology include joints, bedding planes, and folds. The influence of joints results in tall and narrow cave passages, whereas the influence of bedding planes results in cave passages with flat ceilings and (or) floors. The influence of folds is less common, but a few cave passages follow fold axes and have distinctive arched ceilings.

Abstract This two-day trip highlights new findings from structural, stratigraphic, and petrologic research in the Valley and Ridge province of Highland, Bath, and Augusta Counties, Virginia, and Pendleton County, West Virginia. The structural emphasis on Days 1 and 2 will be at several scales, from the regional scale of folds and faults across the Valley and Ridge, to outcrop-and hand sample-scale structures. Stops will highlight deformation associated with previously unmapped faults and a second-order anticline in Silurian and Lower Devonian carbonate and siliciclastic strata, specifically the Silurian Tonoloway Limestone, the Silurian–Devonian Helderberg Group, and the Devonian Needmore Shale. The stops on Day 1 will also focus on facies changes in Silurian sandstones, the stratigraphy of the Keyser–Tonoloway formational contact, and new discoveries relevant to the depositional setting and regional facies of the McKenzie Formation in southern Highland County. The focus of the stops on Day 2 will be on the petrology and geochemistry of several exposures of the youngest known volcanic rocks (Eocene) in the eastern United States. Discussions will include the possible structural controls on emplacement of these igneous rocks, how these magmas and their xenoliths constrain the depth and temperature of the lower crust and mantle, and the tectonic environment that facilitated their emplacement.

Early flow paths can be traced along structural segments (single fractures, fracture intercepts, or zones of closely spaced fractures) through hundreds of kilometers of branchwork caves in structurally complex settings along the eastern Allegheny Plateau of West Virginia, USA. Identification of the early fracture conduits presupposes the following primary conditions: (1) prominent fracture traces are retained on bedrock perimeters; (2) fracturing associated with later cave enlargement is minimal and distinguishable from transmissive fractures; (3) conduit enlargement and modification are not so extensive or so directed as to have totally destroyed the fractures; and (4) there is minimal covering of relevant fracture traces by clastic or chemical sedimentation. Criteria used to infer structural segments include: (1) the presence of anastomoses or other dissolutional features along fractures; (2) the presence of tubes, half tubes, or segments of passage concordant to fractures; (3) the existence of anastomoses and other tubes that grow upward from initially transmissive fractures; (4) the presence of features of entrenchment that are lower than remnant tubes, half tubes, and most early parts of joint fissures; and (5) the continuity of flow along fractures, except at locations of dissolutional mining to create mined segments. If structural segments are identified and mapped with high-precision leveling surveys, a framework can be provided to decipher many details of flow-path integration and enlargement. It is then possible to reconstruct cave history using evidence provided by analysis of passage morphology, sediments, and the relationships of cave features to local and regional surface features.