Caves and Karst of the Greenbrier Valley in West Virginia

The segment of the Appalachian karst known as the Greenbrier karst is located in the lower valley of the Greenbrier River in southeastern West Virginia. The karst is developed in the Mississippian Greenbrier Limestone which thickens from 100 to 365 m northeast to southwest. The region can be subdivided into drainage basins which drain by subterranean routes to big springs. The Greenbrier karst contains more than 2000 caves of which 24 have surveyed lengths exceeding 5 km. The accumulated length of those 24 caves is 503.7 km.

The Greenbrier Karst is located in the Appalachian Highlands in the boundary region between the strongly folded rocks of the valley and ridge province and the gently folded rocks of the Appalachian Plateau. The outcrop of the karstic Greenbrier Limestone occupies portions of Pocahontas, Greenbrier, and Monroe Counties in southeast West Virginia. The Greenbrier Formation is subdivided into the Alderson Limestone, the Greenville Shale, the Union Limestone, the Pickaway Limestone, the Taggard Formation, the Patton Limestone, the Sinks Grove Limestone, and the Hillsdale Limestone. Intermediate shale beds exert an important controlling influence on cave development. Below the limestone is the Maccrady Shale which acts as an aquiclude. A sequence of relatively gentle north–south folds controls the limestone outcrop area at the land surface. Fractures provide further controls over the drainage pathways.

Studies of the karst drainage systems of the Greenbrier limestone in southeastern West Virginia began in the early 1960s and were the first to make extensive use of water-tracing techniques and cave mapping in the USA. The carbonate aquifer is about 400 ft (120 m) thick in the Swago Creek area west of Marlinton (Pocahontas County) increasing to 1000 ft (300 m) in southern Monroe County. The basic hydrogeologic setting for the region consists of relatively flat-lying limestones exposed in valleys or plateaus and surrounded by higher elevation clastic units. Recharge to the conduit aquifer system is by capture of surface streams originating on the clastic rocks (allogenic recharge) and water infiltrating through the extensive areas of dolines (autogenic recharge). Only a few surface streams cross the carbonate outcrop, and even, these tend to loose water into the karst drainage systems. Much of the flow through the aquifer is through conduits under open channel conditions much like a surface stream with a roof. Discharge is concentrated at large springs that typically display rapid response to storm events, and the ratio of maximum to minimum discharge exceeds 100:1 for most of the springs. The karst caves and conduits are generally decoupled from surface topographic features, and the patterns of mapped cave passages are influenced by structural and stratigraphic characteristics. Insoluble beds within the Greenbrier Group may perch underground streams well above the apparent base level, and the underlying Maccrady Shale acts as an aquitard with several large caves developed along the contact of the shale and the overlying limestone. Much of this area can be considered a “contact karst” with the clastic rocks delivering concentrated recharge water onto the soluble limestones and the underling shales eventually forcing the return of conduit flow to the surface. The available data on water wells in the limestone suggest that most are actually producing from shaley units with the limestones acting as confining beds. The Greenbrier River and its tributaries represent base level for most of the area, and the relief of several hundred feet provides the hydraulic gradient. The area is underdrained by a well-integrated network of caves.

The Greenbrier Karst is formed on a roughly triangular exposure of Mississippian-age Greenbrier Limestone that extends 90 km NNE to SSW in Pocahontas, Greenbrier, and Monroe Counties, West Virginia. The geologic setting is conducive to the development of long caves but not deep caves. Within the Greenbrier Karst are 24 caves with surveyed lengths greater than 5 km of which nine have lengths greater than 20 km for a total of 500 km of cave passage plus many smaller caves. Caves are fragments of conduit system with a fractal length distribution skewed toward long caves. The surface karst consists primarily of dolines and blind valleys. The area is surrounded by clastic rock mountains which provide many surface streams that sink at the limestone contact. The result is a patchwork of large underground drainage systems each discharging through a large spring. Analysis of the profiles of active surface streams and abandoned stream beds gives some insight into the developmental history of the karst.

The earliest accounts of caves in the Greenbrier Valley document mining for saltpeter, which occurred in 23 caves at various periods from the late 1700s, through the War of 1812, and the American Civil War. Technical descriptions of the caves began in the late 1940s with the work of William E. Davies. Exploration by cavers began in the 1950s and expanded rapidly thereafter. Exploration and survey were greatly enhanced by the organization of the National Speleological Society (NSS), West Virginia Association for Cave Studies (WVACS) and the West Virginia Speleological Survey (WVASS). This chapter summarizes the overall exploration history and provides exploration details of 14 selected individual caves.

The Swago Creek Basin is the northernmost drainage in the defined area of the Greenbrier Karst. It is a fluviokarst basin with extensive underground drainage but relatively little expression of surface karst. Swago Creek heads in two large cave-entrance springs: Overholt Blowing Cave and Cave Creek Cave. The Overholt Blowing Cave stream can be explored nearly to the head of the Dry Creek Valley but the upstream segment of the valley is pirated eastward to springs on the opposite side of the mountain. Little of the Cave Creek drainage is accessible to direct exploration but some fragments are represented by Barnes Pit, Tub Cave, and the Carpenters-Swago System. The Carpenter-Swago System has 3.1 miles of surveyed passage, and it is strongly controlled by a N60°E fracture system. Extensive stream tracing in the basin reveals details of drainage pattern which is strongly controlled by the shaly Taggard Formation.

The Little Levels are a segment of the Greenbrier karst that may also be a segment of the Harrisburg erosion surface. The karst surface truncates the westward dipping Greenbrier Limestone. The underlying Maccrady Shale, an effective aquiclude is exposed at the land surface along the southeastern edge, forming a groundwater dam between the karst and the deeply incised Greenbrier River. All drainage in the central portion of the Little Levels is subsurface either east to Stamping Creek springs or southwest to Locust Spring. However, few parts of the underground are accessible to observation. The caves of the Little Levels are of intermediate size, one to two miles, and many carry active streams which allow some interpretation of the eastern and western edges, but not the central portion.

The Friars Hole Cave System in Greenbrier and Pocahontas Counties, West Virginia, at 73.4 km, is the longest cave in the Appalachian Highlands of eastern USA. The cave System, composed of three internal drainage complexes extending over a linear distance of almost 7 km, has had a long and complex evolution with most of it being over 730,000 years old and one dated speleothem having an age of over 1.67 million years. Although nearly the entire cave System is developed in the upper Greenbrier Group limestones (the Union and Pickaway limestones), two of the cave’s three active drainages breach the Taggard formation, a major aquitard below the Pickaway and extending the cave’s stratigraphic extent. The cave represents an evolutionary sequence of drainage Systems discharging to two springs 20-km distant from each other with high flows discharge to one and low flows to the other. Drainage patterns have shifted over time as the surface drainage is captured. An estimated age for the entire System is 4.1 million years.

The Buckeye Creek watershed is a 14 km² enclosed basin of which 12 km² drains through Buckeye Creek Cave to lower Spring Creek. The 1.6-km long stream passage is generally 6+ meters wide and 3+ meters high with the primary restrictions being the Gray Canyon near the entrance and partially flooded sewer passages near cave’s downstream terminus. The passages below Turner Avenue are large trunks that are connected to the present stream passage by collapse features and solutional passages that may be remnant phreatic loops. Buckeye Creek grades to Spring Creek and the modern cave stream generally follows strike. The highest passages in Buckeye Creek Cave are at least 788,000 years old based on magnetic reversals found in cave sediments. Buckeye Creek Cave is being enlarged by corrosion, but abrasion and quarrying also play important roles. The abrasion is accomplished by sediment transported during floods. Three stalagmites were used to study local climates over the past 7,000 years. The most detailed time series record multiple dry periods lasting centuries. The “droughts” coincided with Bond Events, which were episodic periods of enhanced ice-rafting in the North Atlantic Ocean believed to have been triggered by protracted cooling.

Culverson Creek Cave is an active stream cave with a large surface catchment of 42 mi² (109 km²). The cave is in the Union Limestone and discharges to springs along Spring Creek. Because of the large surface catchment and some partial blockages along the passages, the cave is subject to flooding. There are ten entrances, large passages, and numerous streams, with a total surveyed length of 20.1 miles (32.4 km).

Six major cave systems are developed along the eastern border of the basal Hillsdale Limestone (Greenbrier Group) and the underlying Maccrady Shale between the town of Lewisburg and Spring Creek in central Greenbrier County. The total combined surveyed passage is just over 128 km (80 miles). The Hole is the northernmost of the contact caves and drains north to Spring Creek. Ludington, McClung, Maxwelton Sink, Benedict, and Wades caves drain southwest to Davis Spring. These caves are developed in the lower section of the Hillsdale Limestone with many passages entrenched by vadose erosion by up to 12 m (40 ft) into the shale. Recharge is mostly from small surface streams that flow westward on the Maccrady Shale and sink at the contact with the limestone. The pattern of passages is typically dendritic with an overall trend sub-parallel to the regional strike. Folding and faulting influence passage orientation in some of the passages, but the perching effect of the underlying shale forces the conduits downward along the local dip.

Muddy Creek represents the resurgence of Sinking and Hughart Creeks with a catchment of about 40 mi² (104 km²) in central Greenbrier County, West Virginia. The combined flow of Sinking and Hughart Creeks appears in a large karst window just south of I-64. This karst window floods to depths of 80 ft (24 m) or more during high water and is locally known as “Interstate Lake.” This water reappears at Piercys Mill Cave (the head of Muddy Creek) under low-flow conditions. Water level loggers were established at the two sinking streams, the stream in the karst window, and the two cave resurgences to monitor the response of the karst drainage system to storm events. With rising water levels, a threshold is reached in Piercys Mill Cave at a discharge of about 60 cfs (2.55 cms) and excess water is shunted to Piercys Cave about 2400 ft (750 m) downstream. The flow from Piercys Mill Cave does not exceed a maximum value of about 200 cfs (5.66 cms). The straight-line distance from Sinking Creek to Piercys Mill Cave is about 2.5 miles (4 km) and tracer tests showed a range of travel times between 15 h under average flow conditions to 85 h at very low flow.

Organ Cave with a length greater than 38 miles (62 km) is the second longest cave in the Greenbrier Karst. It is located beneath a fragment of the Big Levels karst surface bounded by the Greenbrier River to the north, Second Creek to the south and west, and shales and sandstones to the east. Organ Cave is a contact cave with the active drainage cut into the underlying Maccrady shale. It displays a dendritic drainage system with multiple streams merging to a common resurgence on Second Creek. The geologic setting of the cave, both stratigraphic and structural, is presented in considerable detail. The main trend of the cave is along the Caldwell Syncline. Chert horizons in the Hillsdale Limestone and steep folding and minor faulting have all served to guide passage development. The cave has a long exploration history extending back to the mid-twentieth century.

Dickson Spring drains about 26 mi² to Second Creek and is the largest catchment in Monroe County. Water emerges at the base of a cliff in the lower Patton Limestone. Eight significant caves are reported within this basin, and all of the passages are developed in the Patton, Sinks Grove, and Hillsdale units. Several of the entrances receive small streams and are at the contact of the Hillsdale Limestone and the Maccrady Shale. The caves, with the exception of Haynes Cave, are all in the headwaters (southern) part of the drainage basin and are complex from a geologic and hydrologic viewpoint. Most of these caves have received little attention in the last forty years because of access limitations.

Windy Mouth Cave is a mostly abandoned paleospring conduit that drained water from the Big Levels surface northward to the Greenbrier River. The formation of the cave was controlled by a combination of structural and hydrologic factors. Geologic structure provided a pre-solutional network of faults, joints, and bedding planes in the bedrock that was later exploited by groundwater flux. The cave is situated on the western limb of the Sinks Grove Anticline. Beds dip gently to the northwest and strike generally N40–50°E in the cave. Conduits are primarily oriented along strike, while a smaller component is oriented sub-parallel to dip. In plan view, Windy Mouth Cave appears as a branchwork system with a minor anastomotic morphological element overprinted on the dominant dendritic pattern. There are three levels in the cave. Upper levels are phreatic tubes that are connected to small vadose canyons at their origin, and contain some active water. The middle level comprises mainly large phreatic passages, but with substantial clastic fills. The lower levels are well-developed canyon passages that run down dip and crosscut and incise below the main level of the cave. Conduit cross-section morphology is complicated by interbedded chert and shale layers in the Hillsdale Limestone host rock. The impermeable layers form resistant ledges that split individual conduits into multiple levels. Fluvial sediment deposits that are suitable for paleomagnetic analyses were not found in the upper levels, although the position and hydrologic genesis of the system suggest that the upper levels were formed first and are thus the oldest portion of the cave. A magnetically reversed sample was found near the base of one section that was presumably deposited during the reversal of the geomagnetic field which ended at 788 ka. This sets the minimum age of the cave. The modern-day hydrology is markedly different from the past. The drainage basin area is much smaller (~2 km²), and the resident streams have considerably less discharge. Much of the drainage has been pirated to the Scott Hollow drainage basin located south and west of Windy Mouth Cave.

The Scott Hollow Drainage basin is a mature karst system that serves as a northward flowing subterranean tributary to the Greenbrier River. A well-developed conduit system transports waters through this upland basin via a series of branchwork passages. The main underground stream, the Mystic River, flows 10.4 km (6.5 miles) and has both eastern and western tributaries, fed by a combination of concentrated and diffuse recharge. Upper-level passages are mostly disconnected from the active lower ones and seem related to an earlier phase of speleogenesis. The complex flow system is impacted by surface land use in this rural basin, and well drilling has resulted in intersection with the cave in at least two places. Aquifer development within this basin follows structurally controlled initial porosity and “perching” on an underlying shale unit. The northward flowing Mystic River is controlled by regional flexures resulting from Alleghenian compressive stress and an unmapped thrust fault. Tributaries joining the Mystic River from the east generally trend down dip along bedding planes, while western tributaries follow steeper, more complex paths, at least partially controlled by a thrust fault. This has resulted in chemical differences between the waters constituting these tributaries, although all are fed by sinking streams from the upland surface. Sediments within the cave include chert gravels in the active streams (many of which are manganese oxide coated), along with relict diamicts that are currently undergoing excavation.

The Laurel Creek Basin is located in an isolated outcrop of Greenbrier Limestone to the southwest of the main Greenbrier Karst. It is drained by Laurel Creek, a tributary of Indian Creek and thus of the New River. The underground route of Laurel Creek passes through Laurel Creek Cave, Rimstone-Crossroads Cave, and Greenville Saltpeter Cave. The caves are in nearly flat bedding near the crest of the Abbs Valley Anticline.

The West Virginia cave fauna includes species that leave caves periodically to forage (cave crickets and bats) as well as permanent inhabitants (both species that are limited to caves [troglobionts] and ones that occur elsewhere [troglophiles]). Troglobionts are the best studied, but troglophiles predominate in many caves. Major sources of food for the terrestrial cave communities are transitory organic matter brought in by bats and cave crickets, and riparian deposits along streams. A total of 40 troglobionts are known, 19 of which are endemic to the Greenbrier karst. The highest species richness is in the contact caves and Buckeye Creek drainage in Greenbrier County. Greenbrier County is a hotspot of troglobionts in the USA.

The Greenbrier Karst harbors 16 species of stygobionts known from 92 caves, and six of these caves are type localities of ten of the species. The fauna is dominated by crustaceans and especially amphipods of the genus Stygobromus, and they primarily occupy vadose streams and the epikarst, but are notably absent from phreatic waters. Stygobromus spinaus is the most widely distributed, found in 59 caves. The segmented worm Trichodrilus culeri and the salamander Gyrinophilus subterraneus are both endemic to single site. The amphipod Gammarus minus is the most intensely studied species, but the basic biology of the other species is little known. The Organ Cave system holds the record in species richness (8) and in terms of type locality (3 species) and deserves a coordinated effort for protection.

Every cave has the potential to be a repository of Pleistocene and older bones and past life. The Greenbrier Valley Karst in particular has a rich repository of late Pleistocene faunal remains. Cave entrances lend themselves to be nesting places for birds of prey who deposit the bones of their meals onto cave floors. The very nature of sinkholes and surface pits creates natural traps for animals. Streams are a source for depositing animals in caves where they die and are buried in cave sediments. Caves are also used as dens for a variety of extinct and living animals that died or left the remains of their prey. The unique environment of caves contributes to the entrapment and preservation of Ice Age bones.