Southeastern Naturalist D.L. Matchen 2015 Vol. 14, Special Issue 7 7 Canaan Valley & Environs 2015 Southeastern Naturalist 14(Special Issue 7):7–17 The Geology of Canaan Valley David L. Matchen* Abstract - Canaan Valley (hereafter, the Valley) is located in the Folded Plateau Physiographic Province of the Appalachian Mountains. The Province features broad, gentle folds and low, structural dips. The Valley lies over the Blackwater Anticline, one of three structures that characterize the high plateau in which the Valley is set. The Anticline plunges northward, creating a broad amphitheater at the Valley’s northern end. Southward, the Anticline truncates against a zone of discordance. The cause of the discordance is unknown. South of this zone, the Plateau is more deeply dissected, and the Anticline cannot be traced. In its place, there are three structures that terminate northward against the zone. Local stratigraphy controls the Valley’s landscape. Six stratigraphic units—the Pennsylvanian Kanawha Formation, New River Formation, Mississippian Mauch Chunk Formation, Greenbrier Limestone Formation, Price Formation, and Devonian Hampshire Formation—outcrop in the Valley. The ridges in the Valley are supported by the coarse-grained to conglomeratic sandstones of the Kanawha Formation. Conglomerates of the Rockwell Member of the Price Formation underlie the low ridge in the Valley’s center. Red mudstones of the Mauch Chunk form the Valley’s walls, and the Greenbrier Limestone underlies the floor of the Valley. Two major unconformities are present in the Valley’s stratigraphic section. First, the contact between the Price and the Greenbrier is a major Mississippian unconformity. Second, the Mississippian-Pennsylvanian boundary, represented by the Mauch Chunk-New River contact, is a large regional unconformity represented in southern West Virginia by the Pocahontas and Lower New River formations. On the latest geological map of the Valley, the New River and Kanawha formations are lumped into a single mapping unit because the contact between them is difficult to differentiate due to lack of exposure. Coal and natural gas have been extracted in the Valley area. Coal has been mined from the Upper Freeport coal of the Allegheny Formation and the Bakerstown coal of the Glenshaw Formation (Conemaugh Group). Surface mines associated with these coals form a horseshoe pattern that follows the outcrops of the coals, stretching from the Pendleton Creek area west of Davis to the area south of the Mount Storm Power Plant. Natural gas is produced from the Oriskany Sandstone along the crest of the Blackwater Anticline in the Valley and from the Jordan Run Gas Field just east of the Allegheny Front. Introduction Beyond basic geologic mapping, there have been few geological studies of the area that includes Canaan Valley (hereafter, the Valley). Although publications of the West Virginia Geological and Economic Survey (WVGES) (Cardwell et al. 1968, Kulander and Dean 1978, Ludlum and Arkle 1971) provide some insight into the region’s geology, little has been written specifically about the Valley’s *West Virginia Geological and Economic Survey, 1 Mont Chateau Road, Morgantown, WV 26508. Current address - Department of Geology and Physical Sciences, Concord University, Athens WV 24712; dmatchen@concord.edu. Southeastern Naturalist D.L. Matchen 2015 Vol. 14, Special Issue 7 8 geology. This report provides basic descriptions of the rocks and structures that form the Valley and the information herein may guide further scientific st udies. Geologic Setting The Valley region can be subdivided into distinctive areas (known as Physiographic Provinces) based on similarities in topography, geological structures, and rock types (Fig. 1). The Valley and Ridge province lies east of the Valley and is characterized by intensely folded layers of sedimentary rock, the ridges of which are supported by resistant sedimentary rock; the valleys are underlain by less resistant limestone and shale. The Valley lies on the eastern edge of the Appalachian Plateau, an area characterized by relatively flat-lying sedimentary rock that has been deeply eroded into canyons by recently developed rivers and streams. Sandstone, shale, and coal support the plateau and these features comprise the bulk of the mineable Appalachian coal fields. The Valley lies in a transition zone between the intensely deformed strata of the Appalachian Valley and Ridge and the mildly deformed strata of the Appalachian Plateau (Fig. 1). The transition zone is called the Folded Plateau (Kulander and Dean 1986). In the Valley region, the Folded Plateau is approximately 25–30 mi (40–48 km) wide and is characterized by broad, open folds. The Folded Plateau differs from the Valley and Ridge in both the age of the folded rock and the character of the folds. Figure 1. Location of Canaan Valley within West Virginia. The map of the state includes the boundaries of the major Physiographic Provinces of West Virginia. The detailed map illustrates the primary folds that contribute to the topography of the Valley region. Southeastern Naturalist D.L. Matchen 2015 Vol. 14, Special Issue 7 9 Explaining the difference between these two geological provinces of the Appalachians requires some deeper background. The sedimentary rock of the range is 300–450 million years old and was shed from a series of three successive, now eroded, mountain ranges. The erosion of these mountains produced an enormous quantity of sediment that was deposited on the flanks of the ranges, buried, converted into sedimentary rock, and subsequently deformed during the collision that produced the last of the three mountain ranges. This event produced the ancient supercontinent of Pangaea. An enormous mountain range developed along this collision, the roots of which can be traced from west Texas, through Arkansas, up the eastern seaboard, into the Canadian Maritime provinces, across the Atlantic Ocean, which did not exist at the time, into Ireland and Scotland, and finally up the mountainous spine of Norway. As Pangaea separated, the Atlantic Ocean formed and the great mountain range was broken down and eroded. It is the deep roots of this mountain range that we observe in the geological structures of the Appalachians. The Valley and Ridge province was closer to the collision so it displays more intense deformation than the Appalachian Plateau, which was farther from the collision and displays milder deformation. We can measure the intensity of the deformation in the geological structures. The simplest geological structures are folds. If we assume that sediment is deposited in a horizontal bed—and we have discovered no evidence that sedimentary strata are deposited in anything but horizontal layers—then any deviation from horizontal represents some degree of structural deformation. As rock is compressed during a continental collision, the strata buckle to accommodate the reduced space available. Rock layers that buckle upward are termed anticlines, and rock structures that buckle downward are synclines. Synclines and anticlines occur adjacent to one another. The traces of the major folds are identified in the expanded view of the Valley in Figure 1. We measure and map folds by measuring the orientation of the sedimentary layers relative to horizontal. The angle of a sedimentary bed relative to horizontal is called dip. A fold is defined by two limbs that dip in opposing directions and an axis that bisects the fold where the dips change directions. The Valley has been eroded along the axis of the Blackwater Anticline, which can be traced down the center of the valley from northeast to southwest. The folds around the Valley differ from the more easterly folds of the Valley and Ridge in several important ways: 1) they have a much greater wavelength, i.e., distance from one anticline axis to the next anticline axis; 2) they have a much lower amplitude, i.e., the elevation difference between crest and trough; and 3) the rock around the Valley is Mississippian and Pennsylvanian,~300–350 million years old, while the rock of the Valley and Ridge is 350–450 million years old. Erosion of these structures has produced today’s surface topography. Throughout the region, resistant sandstones preserved in the broad synclines support the highest ridges and plateaus (e.g., Dolly Sods). Anticlines are commonly eroded—often referred to as breached—and form broad, open valleys separated by the high plateaus. The Valley is one of the most prominent of these Southeastern Naturalist D.L. Matchen 2015 Vol. 14, Special Issue 7 10 valleys in the Folded Plateau province. Throughout the region, the presence of ridges and valleys is directly related to the overall resistance of the underlying rock to erosion. Sandstones are composed primarily of the mineral quartz, are durable and resistant to erosion, and form ridgelines and cliffs. Limestones and shales are composed of the minerals calcite and clay, respectively, which are much less resistant and erode to produce slopes and valleys. Stratigraphy Stratigraphy is the study of layered material, or strata. Knowledge of a region’s stratigraphy is necessary to understand its geology. While the basic principles of stratigraphy seem rather obvious, the definition of these principles represented a substantial breakthrough in geological understanding in the 17th, 18th, and 19th centuries. The simple principles of sedimentation, superposition, and original horizontality are crucial to our understanding of stratigraphy. Originally proposed by Nicholas Steno in the 17th century, the idea that most of the rock around Florence, Italy was formed by the deposition of sediments from moving water was novel, and Steno concluded that any stack of rock with sedimentary characteristics represented an historical record. He hypothesized that the strata at the bottom of the stack must be older than the strata at the top. Because each stratum was formed from sediment deposited by moving water, it must have been deposited parallel to the surface of the Earth. Further, he posited that if strata are no longer parallel to Earth’s surface, then those strata must have been moved from their original position and are what geologists now consider to be deformed. Steno never published a full explanation of his hypotheses, and they disappeared for a century until they were reconsidered during the Scottish Enlightenment, when his ideas were consolidated into the origins of modern geology by James Hutton. Today we use these basic ideas when we represent and describe the bedrock of any region. A rock description is presented as a stratigraphic column (Fig. 2), with the oldest rock on the bottom of the column and the youngest at the top. The column is then subdivided into a series of rock units generally composed of similar material formed during a relatively short period of time. Each of these rock units represents a section that was identified, defined, and reported in the geological literature. The stratigraphic names presented in any geological column were defined at a particular location, i.e., its type section. For example, the Greenbrier Limestone was initially named in Greenbrier County, WV. Information from stratigraphic columns is then mapped and traced to other locations in the region. Each defined unit has a distinctive set of characteristics that allows somebody new to the region to recognize the stratum. A general characteristic that field geologists use to identify a formation is the facility with which it can be mapped. If the unit can be easily followed and its boundaries mapped, that unit is more likely to be called a formation. The definition is broad and subject to some interpretation but it works as well as any other system that geologists have been able to devise. Southeastern Naturalist D.L. Matchen 2015 Vol. 14, Special Issue 7 11 Figure 2. Stratigraphic column for Canaan Valley and the surrounding area. Names correspond to a mappable group of strata that are distinctive and recognizable. More detailed descriptions of the strata can be found in the text. Values represent thickness of the strata. Wavy lines between strata represent boundaries where significant erosion is recognized between stratigraphic layers. Southeastern Naturalist D.L. Matchen 2015 Vol. 14, Special Issue 7 12 One of the most interesting aspects of sedimentary rocks is that they reflect the environments in which they were deposited. Therefore, the study of sedimentary rock is the study of ancient environments. Sedimentary units are complex and heterolithic, i.e., they are composed of more than one rock type. The Valley’s general column (Fig. 2) and the descriptions that follow represent a generalized version of the stratigraphy. More detailed versions are available in Fedorko (1994). After geologists established a convention for defining sedimentary units, they created a system for defining periods of geological time. The rules used to define parts of geologic time were the same as those used to define sedimentary units. Geologists then defined periods of the stratigraphic column in the British Isles based on the rock found in the region. Thus, the Cambrian, Ordovician, Silurian, Devonian, and Carboniferous periods were named and defined after regions with a particular suite of rocks and fossils. This system is still in use today, but the boundaries blur between time periods when the rocks are geographically distant from the region in which they were defined. For instance, in the Appalachians, although Silurian, Devonian, and Carboniferous rocks are distinctive from one another, the boundaries between these time periods can be rather fuzzy and difficult to identify, often requiring some modification of the system to suit the characteristics of a particular region. Devonian Of the Devonian formations present in the the Valley area, only the uppermost Hampshire Formation is exposed within the Valley. It is the red rock found along the banks of the Blackwater River as it cuts through the low ridge in the center of the Valley. Older Devonian rock, consisting of the Foreknobs and Brallier formations, is exposed along the east-facing slopes of the Allegheny Front, below Dolly Sods. All of these formations are composed of quartz sand and silt, and a large quantity of clay. Good exposures of the Devonian section can be seen on WV Route 42 at Scherr (Avary 1986) and on US Route 33 east of Elkins (Mc- Colloch and Schwietering 1986). These strata are at least 3000 ft (915 m) thick, and vary considerably from thinly bedded, fine-grained, tan-colored sediments at the base, to red sandstones and mudstones at the top. This sequence of rock represents a transition from deepwater environments at the base to coastal plain and terrestrial environments at the top. It is infrequent in the Valley. Mississippian The Mississippian is represented by three stratigraphic units, the Price Formation, Greenbrier Limestone Formation, and the Mauch Chunk Formation. These formations underlie the floor and walls of the Valley. The concept of unconformity is crucial to understanding the Mississippian sections of the the Valley region. An unconformity is a surface that separates stratigraphic units. These surfaces mark periods of erosion in the sedimentary record. One unconformity separates the Greenbrier Formation from the Price Formation, and a second unconformity occurs at the top of the Mauch Chunk Group. Geologists have determined that Southeastern Naturalist D.L. Matchen 2015 Vol. 14, Special Issue 7 13 each of these surfaces is associated with a significant amount of erosion. The Price-Greenbrier unconformity erodes ~400 ft (~122 m) through the entire Price Formation to the southwest of the Valley. Although the unconformity at the top of the Mauch Chunk Formation is less dramatic in the Valley region, it is marked by deep valleys in southern and western West Virginia. The Mauch Chunk Formation can be observed below Canaan Heights on WV Route 32 and in Red Creek at the entrance to Dolly Sods. Scattered exposures of the Greenbrier Limestone can be seen throughout the southern Valley along WV Route 32; good exposures are available along WV Route 32 in a quarry at the south end of the Valley. The Price Formation is best seen in exposures on WV Route 32 near Harman and at Scherr (Avary 1986). The tops of some sandstone beds belonging to the Price Formation can be seen in the central Valley along the low ridge. The Price Formation consists of interbedded siltstones, sandstones, and shales. This formation is recognized by tan-colored, coarse-grained sandstone best distinguished by abundant trough cross-bedding and coarse conglomerate beds. Cross-bedding is a geological structure that forms sedimentary beds at an angle to horizontal, and usually indicates deposition from rivers. Pebbles of quartz up to 20 cm (8 in) in diameter have been observed at some locations within the Price Formation. Regardless of the rock type, whether sand, silt, or shale, the dominant colors are brown and tan. The Greenbrier Limestone Formation, approximately 400 ft (122 m) thick in the Valley region, represents a distinctive change from the Price and Mauch Chunk formations. Unlike sandstone and shale, which are composed of quartz and clay, limestone is composed of the mineral calcite, the same material that composes clam and snail shells. Calcite forms during periods of geological calm (i.e., little mountain construction) and high sea levels under conditions common in tropical marine environments. The Greenbrier Limestone Formation can be identified across West Virginia, and equivalents can be found in Pennsylvania, Kentucky, and Tennessee, reflecting the vast extent of an ancient ocean. The limestones that are found in the Greenbrier Limestone Formation are often the limestone equivalents of sandstone, composed of tiny broken bits of shells that accumulated along shorelines, or very-fine grained, featureless rock similar to shale. The most interesting rock-type found in the Greenbrier Limestone Formation are oolites, small spherical grains of calcite that accumulate as ocean waves move grains back and forth across the sea floor . The Mauch Chunk Formation, about 1000 ft (305 m) thick in the area, is variable in content and consists of sandstones, shales, mudstones, siltstones, and limestones. Most of those units are very thin and difficult to identify, but the most obvious component of the formation is the red-colored mudstone, which can be seen on all of the Valley’s walls. The red is caused by oxidized iron, commonly recognized as rust, formed with the ancient soils that make up much of the Mauch Chunk Formation. These soils indicate that the ocean under which the Greenbrier Limestone formed was replaced by a coastal plain. Southeastern Naturalist D.L. Matchen 2015 Vol. 14, Special Issue 7 14 Pennsylvanian Pennsylvanian rocks composed of sandstones, shales, siltstones, mudstones, and coal cap the ridges that define the Valley. Pennsylvanian rocks in the region include the New River and Kanawha formations, but these formations are difficult to differentiate from one another in the Valley and are mapped as a single unit, the Pottsville Group, which is an older name derived from outcrops in Pennsylvania. The New River Formation is the lowest Pennsylvanian formation in the region and is composed of shale and coal. Thin, lens-shaped sandstones of the New River Formation can be found on the upper slopes of Cabin and Canaan mountains (Fig. 3). The thick sandstones that cap the ridges and form Blackwater Falls are part of the Kanawha Formation. The old names for these sandstones are Homewood and Connequenessing. Historical signs describing them are posted at Blackwater Falls State Park. They are distinctive, coarse-grained, quartz-rich, and extensively cross-bedded. The high, sandy barrens that characterize Bear Rocks and Cabin Mountain are formed from these sandstones. Younger Pennsylvanian rock is found north and west of the Valley, including the Allegheny Formation, the Conemaugh Group, and remnants of the Monongahela Group on isolated hilltops. Limited exposures make identification and differentiation of these strata difficult. Mined and mineable coal beds are most commonly found in the Allegheny Formation, which is composed primarily of interbedded sandstone, shale, mudstone, and coal (Fedorko et al. 1994). Several of the sandstones are quartz conglomerates and can be easily mistaken for the Figure 3. Detailed cross-section of Cabin Mountain, illustrating the relationship between the stratigraphic units. The Valley is on the left side of the figure, and Dolly Sods is on the right. White indicates shale and mudstone, light gray represents sandstone, and dark gray is limestone. Southeastern Naturalist D.L. Matchen 2015 Vol. 14, Special Issue 7 15 underlying sandstones of the Kanawha Formation. On topographic maps, the approximate trace of the base of the Allegheny Formation is marked by a series of disturbed contours that indicate past surface mining of the Upper Freeport coal, the most actively mined coal bed in the region. The Conemaugh Group is subdivided into the Glenshaw and Casselman formations (Fedorko et al. 1994). These formations are difficult to differentiate without extensive drilling data (Matchen et al. 1998). The most distinctive characteristic of these formations is the red color of many of the mudstones that comprise them. There are some thin shales with marine fossils associated with the red mudstones. The Ames and the Brush Creek shales are two common marine shales associated with these formations. Mined coal beds in these formations include the Brush Creek, Bakerstown, Harlem, and Elk Lick. Strata of the Monongahela Group no longer exist in the area. During the surface mining of Pittsburgh Coal, these rocks were removed from the few high knobs around Fairfax Stone in the North Potomac Syncline. Structure Sediment accumulates in basins after being washed off highlands or mountain ranges. These sediments are compressed, compacted, and converted to sedimentary rock that is often incorporated into new mountain ranges. During these processes, the rock is deformed and shattered, producing folds and faults. The Valley is the result of folds exposed at the surface, but the folds were likely produced by faulting deeper in the Earth. The folding of sedimentary rock is analogous to a rug being pushed against a wall. In some cases, the rock warps upward, forming an anticline, and the rock adjacent to the anticline warps downward to form a syncline. The Valley is a broad, gently-folded, anticline (Fig. 4). Horizontal beds are at 0º; vertical beds, such as those that form Seneca Rocks, have a dip of 90º. Because the rock along Cabin Mountain dips to the east and the rock around Canaan Heights dips to the west, we define the geologic structure that forms the Valley as an anticline. The trend of the Valley follows the axis of the Blackwater Anticline (Fig. 1). The rock on either side of the axis generally dips less than 10º and the rock along Figure 4. Structural cross-section of Canaan Valley. Southeastern Naturalist D.L. Matchen 2015 Vol. 14, Special Issue 7 16 the axis of the fold is effectively horizontal. The Valley has eroded into a form described as a breached anticline, meaning that the axis of the fold has been eroded, producing a valley that follows the trend of the fold axis. The breached topography is the result of the resistant sandstones of the Kanawha Formation being stretched and extended across the radius of the fold. The sandstones are resistant to erosion, but they are brittle, weaken, and fracture when they are stretched, making them more susceptible to erosion. The softer underlying rock then erodes faster, producing the topographic basin that forms the Valley. Folds commonly form over the tops of faults that occur deeper in the crust. Deep faulting likely caused the upwarp that produced the Valley. Oil and gas exploration and development exploited these faults in a sandstone located ~4000 ft (1220 m) below the surface of the Valley. There are very little data available, but we can speculate that the sandstone was bent upward until it fractured, producing a fault that pushed the overlying rock upward into the structure that we now know as the Blackwater Anticline. Exploitable Resources The mineral resources of the Valley area include coal, natural gas, and aggregates. Coal has been mined from Pennsylvanian exposures to the north, east, and west of the Valley, mainly in the Allegheny Formation and Conemaugh Group. Much of the mining has ended, and reclamation has been initiated. Natural gas production is primarily from Oriskany Sandstone along the Allegheny Front and Blackwater Anticline. The productive wells are generally drilled to a depth of 6000–8000 ft (1830–2440 m) into faulted Oriskany Sandstone. Stone aggregate is produced along the summit of Backbone Mountain and in a quarry near Scherr. The latest resource to be exploited in the region is the wind, accessed via wind farms along the Allegheny Front and Backbone Mountain. Literature Cited Avary, K.L. 1986. Greenland Gap, Grant County, West Virginia Pp. 69–72, In T.L. Neathery (Ed.). Centennial Field Guide, Vol. 6. Southeastern Section of the Geological Society of America. Geological Society of America, Denver, CO. Cardwell, D.H., R.B. Erwin, and H.P. Woodward. 1968. Geologic map of West Virginia. 1:250,000 scale. West Virginia Geological and Economic Survey, Morgantown, WV Fedorko, N., J.S. Kite, D. Cenderelli, G.S. Springer, and R.E. Behling. 1994. Bedrock and surficial geology maps of the Blackwater Falls quadrangle, Tucker County, WV. OF9408, 1:24,000. West Virginia Geological and Economic Survey, Morgantown, WV. Kulander, B.R., and S.L. Dean. 1978. Gravity, magnetics, and structure: Allegheny Plateau/Western Valley and Ridge in West Virginia and Adjacent States Report of Investigation RI-27. West Virginia Geological and Economic Survey, Morgantown, WV. 91 pp. Kulander, B.R., and S.L. Dean. 1986. Structure and tectonics of Central and Southern Appalachian Valley and Ridge and Plateau provinces, West Virginia and Virginia. American Association of Petroleum Geologists Bulletin 70:1674–1684. Southeastern Naturalist D.L. Matchen 2015 Vol. 14, Special Issue 7 17 Ludlum, J.C., and T. Arkle, Jr. 1971. Blackwater Falls State Park and Canaan Valley State Park: Resources, geology, and recreation. West Virginia Geological and Economic Survey, State Park Series Bulletin 6. 60 pp. Matchen, D.L., N. Fedorko, and B.M. Blake, Jr. 1999. Geology of Canaan Valley. OF9902, 1:24,000 scale. West Virginia Geological and Economic Survey, Morgantown, WV. McColloch, J.S., and J.F. Schwietering. 1986. Devonian to Mississippian section, Elkins, West Virginia. Pp. 79–83, In T.L. Neathery (Ed.). Centennial Field Guide. Vol. 6. Southeastern Section of the Geological Society of America, Geological Society of America, Denver, CO.