Piedmont and Blue Ridge Provinces
The Piedmont and Blue Ridge provinces, which are underlain almost entirely by metamorphic and igneous rocks, contain a few carbonate rocks, mainly marble, that crop out in elongate belts and lenses trending northeastward. The marble is described in the section on "Dimension Stone" (p. 191). The Murphy marble belt is best known and has been the source of the famed Georgia marble which has been used so extensively for more than 100 years in buildings and monuments throughout the United States. Others which have either been quarried for dimension stone or crushed stone are the Sylacauga Marble Member of the Talladega Slate of Alabama, the marble along the Brevard fault zone in northeast Georgia, westernmost South Carolina, and southwestern North Carolina, the Gaffney Marble in Cherokee County, S.C., and lenses and discontinuous layers of marble in McDowell County, N.C., and in Bibb, Shelby, and Calhoun Counties, Ala. The marble makes excellent crushed stone for construction, and many units that are white and free of silica make excellent terrazzo and whiting. Most marble in Appalachia is dolomitic and variable in composition, so it has little use as chemical or metallurgical stone, although it was used extensively in the past to make lime for agriculture and construction. Chemical analyses of typical marble units in the Piedmont are shown in table 89.
Table 89. Chemical analyses of Precambrian marbles
Unmetamorphosed limestone and dolomite layers are found within the Ocoee Series of Precambrian age. The most important of these are in the Walden Creek Group in Madison County, N.C., and Cocke, Sevier, Blount, Monroe and Polk Counties, Tenn. They are usually impure but have been quarried locally for roadstone and agricultural lime.
Other carbonate rocks, generally unmetamorphosed, are exposed in the Grandfather Mountain window and the Hot Springs window in North Carolina and in smaller windows in the Great Smoky Mountains of Tennessee. These rocks are correlated with Cambrian and Ordovician carbonate rocks (Shady and Honaker Dolomites, and Knox Group) in the Valley and Ridge province, discussed in the following pages.
Cambrian Limestone and Dolomites
Cambrian limestones and dolomites (pl. 3) comprise three major sequences as follows: (1) Shady Dolomite in southern Appalachia and Tomstown Dolomite in northern Appalachia; (2) Conasauga Formation or Group (including the Brierfield, Ketona, and Bibb Dolomites in Alabama) in the south, more or less equivalent to the Honaker Dolomite of northeastern Tennessee and southwestern Virginia, the Elbrook Formation of western Virginia to Maryland, and the Pleasant Hill and Warrior Limestones of central Pennsylvania; and (3) Conococheague Limestone of Western Virginia and Maryland, equivalent to the Gatesburg and Mines Formations of central Pennsylvania and the lower part of the Knox Group in southern Appalachia. The Knox Group, which is Upper Cambrian and Lower Ordovician in age, is the most widespread sequence of carbonate rocks in southern Appalachia and is described separately.
All these formations have been mined for crushed stone. The Tomstown and Ketona Dolomites are the only sources of high-purity dolomite in Appalachia. The Conasauga Formation is mined extensively for limestone used to manufacture cement and lime in Alabama. The Conococheage is mined for cement limestone at Security, Md. Chemical Analyses of these rocks are shown in tables 90 and 91.
The Shady Dolomite to the south and the Tomstown Dolomite, its stratigraphic equivalent, to the north of Roanoke, Va., crop out discontinuously along the boundary between the Valley and Ridge province and Blue Ridge province from Alabama to Pennsylvania. They are rather poorly exposed, being covered by older rocks of the Blue Ridge that have been thrust westward, by slope debris from the Blue Ridge, and by residual weathering products.
The Shady and Tomstown Dolomites are about 1,000 feet thick at most places and consist of gray to light-gray medium- to thick-bedded crystalline dolomite of variable composition, locally containing limestone and shale. Butts (1933, p. 3-4) gives a maximum thickness of 1,800 feet for the Lower Cambrian calcareous sequence of southwestern Virginia (Wythe County). These strata are now included in the Shady Dolomite and the overlying Ivanhoe Limestone Member of the Rome Formation. Edmundson (1958, p. 84) reported the Shady in Betotourt County, Va., to be 731 feet thick and to consist of high-purity dolomite. Hershey and Maher (1963, p. 38-40 and 52) described the Shady of eastern Tennessee as being about 1,200 feet thick and consisting of relatively pure dolomite, locally having layers of limestone in the upper and lower part of the sequence and sandy layers near the base. These authors stated that the Shady Dolomite of Tennessee generally contains 94 percent or more total carbonate and that it averages 52 percent CaCO3 and 42 percent MgCO3.
The Tomstown Dolomite in the Eastern Panhandle of West Virginia consists of high-purity dolomite (table 90) that is mined extensively for use as flux in the steel industry, for the manufacture of dead-burned dolomite, and for other purposes. McCue, Lucke, and Woodward (1939, p. 7-8) described the Tomstown of this region as follows:
The Tomstown Dolomite, approximately 1,000 feet thick, is mainly a light blue-gray to white tough fine-grained splintery dolomite that is medium-bedded and weathers to a dark-brown color; some true limestone members and some shaly zones also occur in the formation * * *. Exposed only in Jefferson County, it contains an important belt of low-silica dolomite, the composition of which approaches the correct proportions of calcium and magnesium in a theoretically pure dolomite. This rock is well suited for certain types of furnace lining, and has been worked from several large quarries.
The Tomstown Dolomite of Maryland and Pennsylvania is generally more impure than it is to the south. Mathews and Grasty (1910, p. 400) described the Tomstown Dolomite in Washington County, Md., as a massive drab-to-white magnesian limestone of which some upper beds contain chert. Analyses of the formation here (table 90) show it to be variable in composition. The Tomstown in Pennsylvania contains considerable amounts of shale and shaly limestone (O'Neill, 1964, p. 3).
Table 90. Chemical analyses of Lower and Middle Cambrian limestones and dolomites
The Conasauga Formation (Middle and Upper Cambrian) in southern Appalachia and equivalent formations in the north are the next younger sequence of rocks containing abundant expoitable (sic) carbonates. These rocks are separated from the Shady and Tomstown Dolomites by a dominantly shaly sequence, the Rome Formation in southern Appalachia, and the Waynesboro Formation in the north (pl. 3). In eastern Tennessee, the Conasauga Formation or shale changes from a sequence of shale and calcareous shale beds near the eastern border of the Cumberland Plateau to one consisting principally of carbonate rocks in the northeasternmost part of the State (Hershey and Maher, 1963, p. 40). Here, the Conasauga is represented by the Honaker Dolomite and an overlying sequence equivalent to the Nolichucky Shale and Maynardville Limestone. To the northeast in Virginia, carbonate rocks of equivalent age have been named the Elbrook Formation or Limestone which in turn extends northeastward through Washington County, Md., into Pennsylvania. In central Pennsylvania the Elbrook is separated into the Pleasant Hill and Warrior Limestones.
The Concasauga Formation or Group in northern Alabama, northeastern Georgia, and southeastern Tennessee consists of a sequence of interbedded shale and limestone 1,000 to 2,000 feet thick (pl. 3). In the Birmingham area, Jefferson County, Ala., it is extensively mined for cement limestone (table 53). The Ketona Dolomite, equivalent to part of the Conasauga, is mined for fluxing stone near Birmingham. Elsewhere, the Conasauga Formation has been exploited only to a limited extent. Near Birmingham the Conasauga is about 1,900 feet thick and consists of thin-bedded, dark-gray, relatively pure limestone with interbedded shale layers (Butts, 1927, p. 3).
The Honaker Dolomite in northeastern Tennessee is about 2,000 feet thick (pl. 3), and consists of thinbedded to massive dolomite and magnesian limestone and some interbedded limestone and shale. The lower part of the formation contains abundant chert (Rogers, 1953, p. 52). Magnesian limestone beds of variable composition are most abundant; they generally contain 90 percent carbonate, of which the MgCO3 content ranges from 7 to 38 percent and averages slightly more than 10 percent (Hershey and Maher, 1953, p. 43).
The Elbrook Dolomite or Formation in southwestern Virginia ranges from thick-bedded medium- to coarse-grained, rather pure dolomite to thinly laminated finely crystalline shaly dolomite (Butts, 1933, p. 6). Limestone beds are present in the upper part of the formation. In Wythe County, Va., the Elbrook Dolomite is 1,800 feet thick; to the north, in Botetourt County, Va., it consists largely of dolomite as much as 2,200 feet thick (Edmundson, 1958, p. 18-19). In the Eastern Panhandle of West Virginia, the Elbrook is at least 1,250 feet thick and consists of siliceous limestone and calcareous shale (McCue, Lucke, and Woodward, 1939 p. 8-9).
In central Pennsylvania, the Elbrook Limestone grades laterally into the Pleasant Hill Limestone, consisting of about 600 feet of dark-gray thick-bedded limestone and thin-bedded shaly limestone, and the overlying Warrior Limestone, about 250 feet of medium-gray fine-grained dolomite with shale partings (O'Neill, 1954, p. 3). The Pleasant Hill Limestone in the southeast corner of Blair County, Pa., is reported to be a potential source of cement limestone; further, all three formations in Pennsylvania are reported to be potential sources of aggregate stone.
In the Valley and Ridge provinces of northern Appalachia, the Upper Cambrian is represented by the Conococheague Limestone which extends into the Gatesburg Formation and the overlying Mines Dolomite in central Pennsylvania (O'Neill, 1954, p. 3-4). In southern Appalachia the Upper Cambrian is represented by the Copper Ridge Dolomite of the Knox Group. The Conococheague consists mainly of dolomite and lesser amounts of interbedded limestone which is generally somewhat siliceous.
Thompson (1961, p. 18) suggested that some dolomite beds in the Gatesburg Formation at Birmingham, Pa., might be a source of metallurgical flux stone or of lime if a high magnesium content is desired. In general, however, Upper Cambrian rocks in central Pennsylvania are too impure or too variable in composition to be used for chemical or metallurgical stone and are mainly utilized for construction stone.
Edmundson (1958, p. 19) described the Conococheague Limestone of western Virginia (including Botetourt County) as follows:
The Conococheague limestone is exposed on the flanks of the Natural Bridge syncline; west of the Pulaski-Staunton fault north of Lexington; and, in the central and western parts of Fincastle Valley. Three different facies were noted in the James River district: impure limestone with minor amounts of dolomite east of the Pulaski-Staunton fault north of Buchanan; interbedded limestone and dolomite in the northwestern belts; and largely dolomite with minor quantities of limestone in the area between Compton and Eagle Rock. The formation is marked by two distinctive features: thin laminae, containing siliceous material, which stand out as crinkly ribs on weathered surfaces of limestone, and beds of coarse-grained friable sandstone. The siliceous banded limestones are generally more abundant near the top of the formation. Sampled units of the limestone contain from 71 to 89 percent calcium carbonate; those of dolomite from 33 to 38 percent magnesium carbonate. Silica varies from about 7 to 17 percent. The thickness of the Conococheague southeast of Natural Bridge is approximately 2,100 feet.
Mathews and Grasty (1910, p. 403-404) described the Conococheague of Maryland as consisting of about 1,500 feet of siliceous and argillaceous limestone which in part is suitable for the manufacture of cement. These authors further stated that the Conococheague had been quarried at several places and that the largest quarry furnished limestone for a cement plant near Hagerstown.
O'Neill (1964, p. 3-4) described the Gatesburg and Mines Formations in central Pennsylvania, as follows:
The Gatesburg Formation is equivalent to the lower portion of the Conococheague Group and consists of thick-bedded, steel-blue, coarsely crystalline dolomite interbedded with many quartzites, some of which are up to 10 feet thick. The total amount of quartzite, however, makes up a relatively small proportion of the entire thickness of the formation which measures 800 feet in Centre County and 1,750 feet in Blair and Huntingdon Counties.
Locally at least, up to 100 feet of highly fossiliferous, thin-bedded limestone occurs in the middle of the Gatesburg Formation.
The Mines Formation is equivalent to the upper part of the Conococheague Group and consists of about 150 to 250 feet of medium-gray crystalline dolomite with an abundance of scoriaceous chert, much of which is oolitic. Unlike the underlying Gatesburg Formation, it does not include any quartzite beds.
These formations would probably make a good quality general-purpose crushed stone but are not suitable for chemical or metallurgical use.
Knox Group (Upper Cambrian and Lower Ordovician)
The Knox Group (pl. 2), is the most widespread carbonate rock sequence in southern Appalachia. Subdivisions of the Knox Group in common usage are shown in plate 3. The sequences consist mainly of dolomite, and nearly all dolomite shown in figure 68 from Tennessee southward belongs to the Knox. Limestone beds are present locally. The Knox contains hard durable stone that makes excellent roadstone and concrete aggregate. Table 91 shows chemical analyses of parts of the Knox Group in Tennessee and Georgia.
Table 91. Chemical analyses of Upper Cambrian and Lower Ordovician limestones and dolomites
Hershey and Maher (1953, p. 43-45) described the Knox Group of Tennessee as follows:
The Knox can be divided into two phases on the basis of rock type or lithology. One of these phases includes all of the Knox east of a line passing roughly through Kingsport and Sevierville. Here the Knox is composed of many successive beds of bluish-gray limestone with subordinate dolomite layers interspersed. The beds range in thickness from a few inches to several feet. In places shaly seams, generally less than an inch thick, are present. Elsewhere, sandy beds and lenses occur, but these commonly are less than a few feet thick. On the whole limestone and dolomite strata are slightly impure, containing variable amounts of silica, clay, and sandy materials, and to this type of rock the names Conococheague and Jonesboro apply.
Elsewhere in East Tennessee the Knox is largely dolomite with subordinate limestone layers, and the formation names applied to the rock are followed by the term dolomite. The dolomite beds are as much as several feet in thickness, are usually some shade of gray or brown, and as a rule are impure. In addition to being largely dolomite this phase of the Knox is characterized by high silica content, as evidenced by the abundance of chert found in Knox soils and in bedrock exposures. The silica content increases markedly toward the west.
In most areas the Knox is distinguished readily from other formations by the presence of chert in outcrops and in the overlying soils. The chert is fragmental and irregular in shape, whereas that of other formations generally is less abundant and is blocky to rounded in outline.
The Knox is notably nonuniform from bed to bed and from quarry to quarry. Individual beds approach high-calcium limestone or high-purity dolomite but generally are too thin to be quarried profitably. Analyses from 22 quarries show that calcium carbonate ranges from 51.5 to 85.7 percent; magnesium carbonate ranges from 5.7 to 42.5 percent; and silica from 2.1 to 13.4 percent. The average of 22 quarries is calcium carbonate 70.0 percent; magnesium carbonate 21.3 percent, and silica 8.1 percent.
The Knox Group is the most important rock unit in East Tennessee as far as economic products are concerned. It is an excellent source of hard durable dolomite and limestone for road metal, railroad ballast, riprap, filler and base course. The road upper one-third of the Mascot Formation, which locally contains faintly mottled green and red beds, has been prospected for building stone. Locally, it is used for agricultural limestone, stucco dash, concrete-block facings, and refractories. Residual cherts from the Knox have been used as road metal and for some building purposes.
The Knox Group crops out extensively in northwestern Georgia and northeastern Alabama. Limestones and dolomites are quarried in Alabama, particularly in Shelby County for both chemical and metallurgical stone. In northwestern Georgia the lower part of the Knox is poorly exposed and has been quarried at only one or two places. The uppermost part of the Knox, the Newala Limestone (pl. 3), crops out in Polk and Bartow Counties of northwest Georgia as a thick-bedded relatively pure limestone and has been quarried for the manufacture of portland cement near Rockmart, Polk County (Butts and Gildersleeve, 1948, p. 22).
Ordovician limestones and dolomites
Ordovician carbonate rocks above the Knox Group are widespread in Appalachia. They are of Middle Ordovician age in southern Appalachia and of Early and Middle Ordovician age in northern Appalachia. The Upper Ordovician strata are predominantly shale and sandstone within the Appalachian Region.
Lower Ordovician limestones and dolomites of northern Appalachia
Lower Ordovician limestones and dolomites of northern Appalachia comprise the Beekmantown Formation, Dolomite, Limestone, or Group and equivalent formations cropping out in the Valley and Ridge province from western Virginia to Pennsylvania (pl. 3). The rocks are mainly impure dolomite suitable for general-purpose crushed stone but have little or no value as chemical or metallurgical stone. Analyses of samples of these limestone and dolomite units are shown in table 91.
Edmundson (1958, p. 19-20) described the Lower Ordovician Chepultepec Limestone and overlying Beekmantown Dolomite of the central western part of Virginia as follows:
The Chepultepec Limestone is one of the best horizons for mapping purposes throughout most of the Valley of Virginia. In this region, it is composed largely of bluish-gray, slightly laminated, fine-grained limestone and minor amounts of thin intercalations of dolomite and magnesian limestone. The maximum thickness of the formation is estimated at 500 feet. Sampled units commonly contain from about 85 to 90 percent calcium carbonate, around 6 percent magnesium carbonate, and from 4 to 6 percent silica. The Chepultepec, for the most part, crops out in narrow valleys bordered by low hills underlain by the more resistant impure rocks of the Conococheague and Beekmantown Formations.
The Beekmantown formation, with an estimated thickness of about 1,500 feet, is composed largely of gray, fine- to medium-grained dolomite. In the eastern belts, limestone perhaps comprises from 10 to 15 percent of the total thickness, whereas only an occasional thin limestone layer was noted in the western portion of the valley. The layers of dolomite are commonly characterized by distinct intersecting furrows on weathered surfaces. Sampled units of dolomite contain from 34 to 39 percent magnesium carbonate and from 5 to 10 percent silica. Chert, although generally not abundant, occurs locally as scattered irregular masses and as distinct beds at several horizons in the formation. The Beekmantown is admirably suited for construction purposes, but does not meet the specifications for high-magnesium dolomite as defined in this bulletin.
The Beekmantown Limestone of western Maryland and the Eastern Panhandle of West Virginia is equivalent to the Chepultepec and Beekmantown of western Virginia (pl. 3). It is about 1,200 feet thick in this area and consists mainly of siliceous dolomite with relatively pure limestone near its base (Mathews and Grasty, 1910, p. 405; McCue, Lucke, and Woodward, 1939, p. 11).
In central Pennsylvania the Beekmantown Group is divided into Several formations made up of a sequence of dolomite and lesser amounts of limestone, about 3,000 feet thick (pl. 3). O'Neill (1964, p. 5) described these formations as containing relatively impure limestone and dolomite suitable only for aggregate stone and roadstone. He pointed out that some of the stone (Larke Dolomite) is suitable for agricultural dolomite and that locally some beds of the Axeman Limestone are suitable for cement manufacture; other beds contained high magnesium limestone.
Middle Orodovician Limestones
Middle Ordovician rocks are predominantly limestone in the Valley and Ridge province (pl. 3, columns 4, 8, 11, 13, 15) but grade into clastic rocks in eastern Tennessee and northwest Georgia (pl. 3, columns 14, 16, 18). They range in thickness from a few hundred to 2,000 feet in most of the region but exceed 5,000 feet where clastic rocks predominate. The sequence comprises many formations, which have been given local names, only some of which are shown on plate 3. The sequence includes some of the most important high-calcium and cement limestones of eastern United States such as: (1) Valentine Member (of Field, 1919) of the Curtin Formation (of Kay, 1943) in central Pennsylvania; (2) Annville and Jacksonburg Limestones in southeastern Pennsylvania (outside Appalachia); (3) New Market Limestone and Mosheim Member of the Lenoir Limestone of western Virginia and the Eastern Panhandle of West Virginia; and (4) Holston Limestone or Formation of eastern Tennessee. Analyses of Middle Ordovician limestones in Appalachia are given in table 92.
Table 92. Chemical Analyses of Middle Ordovician limestones.
Because deposition of Middle Ordovician rocks of the Valley and Ridge province of eastern Tennessee was affected by mountain building to the east, and thick sequence of clastic beds (Athens Shale, Ottosee Shale, and Bays Formation) in the eastern interfingers with limestone beds (Chickamauga Limestone) in the west. Although facies changes are present in the stratified rocks in many other systems and areas in the Valley and Ridge province, the Middle Ordovician rocks are affected to a much greater degree by lateral variations. Rodgers (1953, p. 64) made the following statement about problems of Middle Ordovician stratigraphy:
Probably more controversy has raged over the stratigraphy of the Chickamauga Limestone and equivalent rocks in the southern Appalachians than over that of any other major unit here discussed, except the Ocoee series, and this despite the generally good outcrops, the ready accessibility of the outcrop areas, the well-characterized and differentiated lithologic units, the several usable key beds, and the abundant fossils. The controversy has concerned both subdivision and correlation.
The Holson Formation of eastern Tennessee (equivalent to part of Chickamauga) is the source of the famous Tennessee Marble and is a high-calcium limestone suitable for chemical and metallurgical use. Hershey and Maher (1963, p. 47-48) described the Holston as follows:
The Holston Formation, as represented on the geologic map of East Tennessee (Rodgers, 1953), consists of two units: a lower crystalline limestone (marble) and an upper limy quartz sandstone (Tellico or Chapman Ridge Sandstone).
The marble type is characteristically a pink to cedar-red, crystalline limestone of high purity (more than 97 percent CaCO3). The marble weathers deeply and produces a dark-red clay soil, which locally contains fragments of red iron ore or black manganese ores. Beneath the soil mantle a highly irregular bedrock surface is developed. The interface between soil and bedrock is a complex maze of pinnacles and valleys with 15 to 20 feet of relief, resembling "badlands" topography.
The upper limy sandstone unit is a slabby, dark-gray quartz sandstone, with occasional beds of sandy shale. This unit forms knobby ridges generally covered by pines. Weathering of the sandstone produces a sandy, dark-red clay containing shale chips, spongy sandstone fragments, and locally fragments of red iron ore.
The Holston Formation is about 400 feet thick near Knoxville and thins to about 200 feet near Cleveland, Bradley County. The portion of Holston Formation generally quarried is a crystalline limestone. The lighter colored stone has a higher carbonate content than the darker colored units. Quarryable thicknesses of the Holston may contain 97.5 percent or more CaCO3, and the MgCo3 ranges from 0.0 to slightly more than 2 percent. The Holson contains substantial reserves of high-calcium limestone.
Only one analysis of the Chapman Ridge phase is available. This analysis, as would be expected, shows a high content of silica. 49.4 percent; carbonates comprise approximately 46.5 percent, and the remainder is iron and alumina.
The limestone phase of the Holston meets commercial requirements for marble and is extensively quarried for this purpose. In addition, the high purity, relatively uniform chemical composition of the Holston marble results in the use of this stone for making cement and agricultural limestone. It also is crushed for aggregate, road metal, and similar uses. Generally, sites for such operations are selected on the basis of proximity to markets and in areas where shattering renders the stone unsuitable for dimension purposes.
Limestones in other Middle Ordovician formations (Chickamauga Limestone, Lenoir Limestone including the basal Mosheim Member, Athens Shale, Bays Formation, and Moccasin Formation) have been exploited at a few places in eastern Tennessee (Hershey and Maher, 1953, p. 45-50). They do not make a good quality crushed stone and are too impure or too variable in composition to be used as chemical and metallurgical stone or as cement limestone. The purest stone is found in the Mosheim Member of the Lenoir Limestone, which Hershey and Maher (1963, p. 47) described together with the Lenoir of eastern Tennessee as follows:
The Lenoir Limestone is a shaly, nodular-weathering limestone which locally contains a more pure, dense, fine-grained basal member, the Mosheim Limestone. In some places the uppermost Lenoir contains sparse rough, spongy, yellowish cherts; locally the lower beds contain fragments of chert and dolomite reworked from the underlying Knox dolomite.
The Lenoir is as thick as 500 feet but thins to less than 200 feet in some areas.
The Lenoir weathers to a fairly rich yellow clay soils which is rapidly eroded so that the outcrop belt is marked by ledges of bedrock. The formation normally underlies valleys.
Only one quarry examined in this investigation was developed entirely in the Lenoir Limestone. The analysis showed 62.7 percent CaCo3 and 8.1 percent MgCO3; SiO2 was 25.3 percent. Four analyses by TVA (B. C. Moneymaker, personal communication) average 83.8 percent CaCo3, 7.7 percent MgCO3, and 6.9 SiO2. These tests were made on the nodular gray Lenoir phase.
Although the Mosheim member commonly is described as "High-calcium" limestone, available analyses show this description is incorrect: the CaCO3 content ranges from 91.2 to 96.7 percent, MgCO3 from 3.2 to 6.3 percent, and noncarbonates from 1.4 to 3.1 percent in selected samples (B. C. Moneymaker, personal communication).
The Lenoir Limestone is of minor economic importance. It crumbles rapidly when exposed to weathering and is not chemically uniform enough for a cement stone, although it is of the proper type (i.e., a shaly limestone). The Mosheim member is not of quarryable thickness in many places, and it contains too many shale partings and too much silt generally incorporated in the limestone.
In the Valley and Ridge province of northeastern Alabama (east of Birmingham, Jefferson County), the Middle Ordovician limestone units, from oldest to youngest, are: Mosheim Member, Lenoir Limestone, and Little Oak Limestone (Adams, Butts, Stepehenson, and Cooke, 1926, p. 101-114). The Mosheim is thickbedded fine-grained limestone, having a thickness of not more than 50 feet. The Lenoir proper is a dark finely crystalline medium thick-bedded limestone about 500 feet thick. The Little Oak is a dark thick-bedded coarsely crystalline limestone that locally contains considerable chert. It has a maximum thickness of about 500 feet. The Little Oak Limestone is used for cement manufacture in Alabama (table 53).
In western Virginia (in the vicinity of Botetourt and Alleghany counties), Middle Ordovician limestones have been divided into the New Market Limestone (overlying the Beekmantown Formation), Whistle Creek Limestone,[1] Lincolnshire Limestone,[2] Edinburg Formation,[3] and Collierstown Limestone[4] (Edmundson, 1958, p. 20-23). The Whistle Creek, Edinburg, and Collierstown Limestones consist of relatively impure limestone and shale and have little economic value. The New Market and Lincolnshire Limestones have important resources of high-calcium limestone. They were described by Edmundson (1958, p. 21-22) as follows:
The name New Market limestone (Cooper and Cooper, 1946, p. 71-74) was proposed for the succession of predominantly dense, fine-grained limestone above the Beekmantown and below the dark-gray, medium-grained, commonly cherty Lincolnshire limestone, or locally as in the Lexington area the Whistle Creek limestone. The New Market limestone is essentially the same as the formation identified by Butts as Mosheim in northern Virginia. At other localities, mainly along the belts northwest of Lexington and Newport, it includes also Butts' Murfreesboro, which is composed of impure limestone and angular fragments of chert and locally intervenes between the Beekmantown and Mosheim. The New Market limestone is composed largely of thick-bedded, compact to a glassy, bluish-gray to dove-gray limestone. Among distinguishing characteristics are specks of transparent calcite scattered through many of the layers and thin films of chalk-like material on weathered surfaces. The thickness ranges from a few feet in the belts northwest of Lexington to a possible maximum of more than 200 feet in the Highbridge Church-Indian Rock belt. However, the occurrence of chert and other impurities in the lower part of the abnormally thick sections indicates that the full thickness does not meet the specifications of high-calcium limestone. Field studies indicate that this formation, the chief "quarry rock" of the Appalachian Valley, contains at least 100 feet of high-grade limestone at several localities in Warm Springs valley. Sampled units, except where containing chert nodules, generally average about 97 percent calcium carbonate.
The Lincolnshire limestone (Cooper and Cooper, 1946, p. 75-78) includes those beds above the New Market (Mosheim of Butts) limestone or locally the Whistle Creek and below either the brownish-weathering beds of the Botetourt (Whitesburg of Butts) limestone or below younger beds of the Edinburrg limestone with minor intercalations of light-gray, coarsely granular limestone to thick units composed chiefly of the coarse-grained, high-calcium limestone. It is essentially the same as Butts' Lenoir Limestone in northern Virginia and the Lenoir and overlying Holston limestones recognized by him in the Lexington area. The Holston limestone has subsequently been described as representing not a time-stratigraphic unit, but only a characteristic facies of clastic reefy high-calcium limestone within the Lincolnshire formation.
The Maximum thickness of the Lincolnshire or its equivalent Lenoir and Holston limestones is about 200 feet in the vicinity of Murat southwest of Lexington. Sampled units of this coarsely granular limestone, or Murat limestone facies of the Lincolnshire, along the belt between Lexington and Murat contain from 97 to 98 percent calcium carbonate and represent some of the largest limestone reserves in the James River district.
The Middle Ordovician Mosheim Member of the Lenoir Limestone in the Eastern Panhandle of West Virginia, is one of the most extensively mined high-calcium limestones in Appalachia. McCue, Lucke, and Woodward (1939, p. 13) described the Mosheim and Lenoir of this area as follows (These rocks were assigned to the Stones River Group of central Tennessee on the basis of stratigraphic studies by Stose (1906). Later studies have shown this correlation to be incorrect, and Neuman (1951) proposed the name St. Paul group to substitute for Stones River Group in Virginia, West Virginia, and Maryland.):
Stones River Limestones form an important stratigraphic and economic section of the Ordovician in Berkeley and Jefferson Counties of northeastern West Virginia, where they crop out in the main Appalachian Valley west of the Blue Ridge. Both middle (Mosheim Limestone) and upper (Lenoir Limestone) Stones River can be readily recognized. The former is the most valuable limestone formation of the State, and is a dove-gray to light-blue fine-grained extremely pure limestone of the type known as vaughanite. Its thickness varies from less than 100 feet to about 200 feet, and it has been opened in a large number of active quarries in the vicinity of Martinsburg. * * * There is a complete absence of cherty, magnesian, or siliceous beds of any kind in the Mosheim, so that from some localities it has been possible continuously to ship rock in which the silica content is less than 1.5 percent. The overlying Lenoir, of Upper Stones River age, is 20 to 40 feet thick and consists of dark impure shelly limestones of little or no economic importance.
The Middle Ordovician limestones of central Pennsylvania comprise six formations named by Kay (1943) of which his Loysburg, Benner, Curtin and Nealmont Formations have rock suitable for crushed stone, in part high-calcium limestone. O'Neill described these formations (1964, p. 6-7) as follows:
The Middle Ordovician of central Pennsylvania includes sections of high-calcium limestone in several formations. The most important of these is the Valentine Member of the Curtin Formation which has a sufficient thickness in places for large-scale mining. The Clover Limestone in the Loysburg Formation and the Snyder Limestone in the Benner Formation also contain high-calcium stone in more limited quantities.
The Loysburg Formation lies above the Beekmantown Group in central Pennsylvania. It consists of interbedded limestone and laminated dolomites with an occasional intraformational conglomerate in the lower portion. The upper portion, the Clover Member, varies from about 40 to 80 feet in thickness and is composed of relatively pure, dense, sublitholographic limestone. The maximum total thickness reported for the Loysburg is 480 feet.
Kay (1943, p. 188-189) reported the Clover Member of the Loysburg as a potential source of chemical lime and has been used in the past for blast-furnace flux. The possibility of stone from the Loysburg Formation being acceptable for aggregate and roadstone also appears to be good.
The Benner Formation, which overlies the Hatter Formation, is composed of two members-the Snyder and Stover Limestones. The Snyder is the basal member, consisting of light-colored, thin-bedded, detrital limestone with characteristic limestone-pebble conglomerates and dense, relatively pure, sublithographic limestone. The upper member, the Stover, consists of dark, dense, thick-bedded limestone, commonly separated by silty partings. The Benner Formation reaches a maximum thickness of about 140 feet in the northwest and thins by the loss of the upper or Stover beds to the southeast.
The Curtin Formation is stratigraphically above the Benner Formation and has been separated into two members. The lowermost member, the Valley View, consists of light- to dark-gray, generally fine- to medium-textured, relatively thick-bedded, impure limestones with argillaceous partings and some thin metabentonite beds. At its type section, the Valley View is 52 feet thick. The upper member, the Valentine, is an exceptionally pure limestone, especially above the basal 15 to 25 feet of its 90-foot thickness. The Valentine is made up of very light-gray, dense, thin- to thick-bedded limestone.
The Curtin Formation is exposed only in portions of Centre, Clinton and Lycoming Counties. It is thickest along the northwest side of the Nittany Valley where it measures about 150 feet but thins to extinction to the southeast.
The Valentine Member of the Curtin Formation is an important economic horizon which is presently being extracted at 5 locations in Centre County * * * to supply stone for flux, cement, limes, agricultural purposes, the manufacture of glass, filler, whiting, aggregate, and roadstone materials.
Kay (1943, p. 200-203) reported that the Valentine reaches a maximum thickness of 75 to 90 feet on the northwest side of the Nittany Valley in a belt extending from about 4 miles west of Bellefonte to the vicinity of Jacksonville, a distance of about 15 miles. Farther northeast and southeast of this belt, the Valentine thins to extinction. Kay (1943, p. 200-203) believes this regional thinning was caused by an unconformity which followed deposition, whereas Rones (1955, p. 177) believes it is best explained by a facies change.
Figures reported by Kay (1943, p. 200) show the Valentine to be 80 feet thick at Jacksonville, 10 feet thick at Salona, 52 feet thick at Pleasant Gap, 40 feet thick at Tylersville in Sugar Valley, and 80 feet thick at Spring Bank in Brushy Valley. It is absent at the following places: Antes Gap in the Nippenose Valley, south of Lemont in Brushy Valley, east of Loganton in Sugar Valley, and in Millheim in East Penn's Valley.
The Valley View Member of the Curtin Formation is not as pure as the Valentine Limestone but has been used for blast-furnace flux in the past. Kay (1943, p. 197) reports that it is remarkably constant in character and thickness in the Nippenose Valley and the western end of the Bellefonte district. The Valley View Member is found within all areas of the mapped Curtin Formation. Near its limits of distribution it is beveled by an unconformity which followed deposition.
The Nealmont Formation is the lateral equivalent of the Curtin Formation and lies disconformably above the Stover Limestone. The Nealmont Formation is separated into three members-Oak Hall, Centre Hall, and Rodman, listed in order from the oldest to youngest. The Oak Hall Member consists of about 60 feet of medium-dark-gray, medium- to coarse-grained, thick-bedded limestone with some layers containing dolomite streaks. It contains a thin metabentonite bed about 18 feet below its top. The Centre Hall consists of thin-bedded, fossiliferous, shaly limestone which reaches a maximum of about 44 feet in thickness. It is separated from the underlying Oak Hall Member by a thin metabentonite bed. The Rodman is composed of dark, medium- to coarse-grained, highly fossiliferous impure limestone with some interbeds of thin, dense limestone. Black chert nodules occur in places in the lower part. Its thickness is of the order of 30 feet.
The Nealmont Formation reaches a maximum thickness of 125 to 150 feet in a northeast-southwest trending belt which averages about 8 to 10 miles in width and passes through the center of Blair County, continuing northeastward into Centre and Clinton Counties to the southwest corner of Lycoming County. It thins both to the northwest and southeast from this belt.
The Oak Hill and Centre Hall Members of the Nealmont Formation have been quarried for flux stone whereas the Rodman Member has not. The available chemical analyses for those three members substantiate their general level of acceptance as flux-stone material. * * *
A potential as use for cement limestone and agricultural limestone is also indicated by all of the chemical analyses for the Nealmont Formation. * * *
Silurian and Devonian Limestones
The rocks of Silurian and Devonian age are mainly shales and sandstones in the Valley and Ridge province; limestone units are restricted in extent and thickness, being found in Appalachia only from Tennessee northward. The limestone is generally rather impure, so it is not satisfactory for chemical or metallurgical use and tends to be too variable in composition to be used as cement limestone. Table 93 shows analyses of Silurian and Devonian limestones from Appalachia. The following limestone units are recognized: Hancock Limestone (Silurian and Devonian) of northeastern Tennessee and southwesternmost Virginia; Tonoloway Limestone (Upper Silurian) extending from southeastern West Virginia northward into Pennsylvania; the Keyser Limestone (Silurian and Devonian); and the Helderberg Group of Early Devonian age, comprising the Coeymans, New Scotland, and Becraft Limestones, also extending from southeastern West Virginia northward into Pennsylvania. (See pl. 3, columns 4, 5, 7, 11, 13.)
Table 93. Chemical Analyses of Silurian and Devonian limestones and dolomites
The Hancock Limestone of northeastern Tennessee (Hershey and Maher, 1963, p. 50) is a sequence of thick-bedded limestone and dolomite containing some cherty layers. It has a maximum thickness of 300 feet. In Lee and Scott Counties, Va., the Hancock is only 105 feet thick and consists of medium-dark-gray limestone and shaly limestone containing some interbedded finely crystalline dolomite (Harris and Miller, 1963).
The Tonoloway Limestone of eastern West Virginia and southwestern Virginia is stratigraphically equivalent to the Hancock. It consists of thin-bedded argillaceous limestone and calcareous shale having a total thickness of 350-600 feet (McCue, Lucke, and Woodward, 1939, p. 18-19). In addition to its use as an aggregate, the Tonoloway is used for agricultural limestone in Grant, Pendleton, and hardy Counties, W. Va.
The Keyser Limestone and Helderberg Group of eastern West Virginia were described by McCue, Lucke, and Woodward (1939, p. 22-25) as follows. The Keyser Limestone is best exposed in Mineral County in the northeastern part of the State. It ranges from 150 to 350 feet in thickness and is typically a blue- to dark-gray limestone that is massive and nodular in the lower part and somewhat more thin-bedded and shaly in the upper part. The overlying Coeymans Limestone, cropping out in Pendleton County and northward, is a hard crystalline limestone having an average thickness of about 20 feet. The New Scotland Limestone, the next youngest, is a shaly cherty limestone and calcareous shale generally 18-40 feet thick. The Becraft Limestone, the youngest formation of the group here, crops out only locally in Berkeley, Pocahontas, and Greenbrier Counties, W. Va. It is an arenaceous to cherty limestone as much as 120 feet thick. Limestone of the Keyser and Helderberg is used extensively for aggregate and roadstone in eastern West Virginia.
The limestones of silurian and Devonian age in Pennsylvania were described by O'Neill (1964, p. 7) as follows:
The more important limestones of Silurian and Devonian Age belong to the Tonoloway, Keyser, and Helderberg Formations which have supplied raw materials for use as agricultural lime, building lime, flux, road metal and concrete. In some place, high-grade limestones from the Keyser have been quarried for chemical lime.
These limestones occur in the Appalachian Mountain section of the Valley and Ridge physiographic province in Pennsylvania and are in part responsible for the floors of some narrow, steep-sided valleys that are prominent features in the central part of the State.
The Tonoloway Formation of Silurian age is dominantly gray and platy. In most places it consists of finely laminated, fine-grained limestone, argillaceous limestone, and calcareous shale. The maximum observed thickness of the Tonoloway in Pennsylvania is 325 feet. It is correlated with the Bossardville Limestone and Poxono Island beds in the eastern part of the State.
The Keyser Formation generally has been accepted as the highest formation in the silurian System although new data indicate that the Silurian-Devonian boundary falls within the unit. Stratigraphically it lies above the Tonoloway Formation and typically consists of light- to dark-gray, thin- to thick-bedded, highly fossiliferous limestone. The lower portion of the formation is usually characterized by many nodular limestone beds. The upper portion has been described as relatively argillaceous in places and some chert has been noted in the section. The thickness of the Keyser as measured varies between 88 and 202 feet.
Stone from the Keyser and Tonoloway Formations or their correlatives have been found to be satisfactory for a variety of uses. At the present time, stone from these formations is being produced for aggregate and roadstone materials, agricultural limestone, lime, asphalt filler and, in one case, for cement limestone. In addition, a section of pure massive limestone which occurs near the base of the Keyser Formation in Blair County has furnished a supply of stone for chemical lime and flux stone.
The Helderberg Formation is Lower Devonian in age and is composed of three members. The basal member, the Coeymans, consists of coarse, thick-bedded, crinoidal limestone, locally shaly in its lower portion. In the eastern part of the State, the Coeymans becomes sandy. Chert is usually present. Its maximum thickness is about 10 feet.
The middle member of the Helderberg Formation is the New Scotland. It consists of dark-gray, thin-bedded crystalline limestone varying from 6 to 13 feet thick at the base, above which lies shales, interbedded with impure limestones and chert. the maximum total thickness of the New Scotland Member is about 44 feet.
The upper member of the Helderberg Formation is the Mandata, equivalent to the Port Ewen Shale and Becraft Limestone in the eastern part of the State. The Mandata is in general a dark-gray, calcareous, thin-bedded shale. * * *
The economic potential for the Helderberg Formation cannot be rated good because of the abundance of shale and the relatively thin units of interbedded limestone.
[1] Ibid., page 240, footnote 1: Of Cooper and Cooper (1946).
[2] Ibid., page 240, footnote 2: Of Cooper and Cooper (1946).
[3] Ibid., page 240, footnote 3: Of Cooper and Cooper (1946).
[4] Ibid., page 240, footnote 4: Of Cooper and Cooper (1946).
Commercial use of material within this site is strictly prohibited. It is not to be captured, reworked, and placed inside another web site ©. All rights reserved. Peggy B. and George (Pat) Perazzo.