Natural Resources Geology and Mineral Resources
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NATURAL RESOURCES GEOLOGY AND MINERAL RESOURCES GEOLOGY the County in chronological order beginning with the youngest unit: Centre County is located within two major physiographic Allegheny Group provinces: the Appalachian Plateaus Province and the The Allegheny Group of the Pennsylvanian Ridge and Valley Province. System crops out in small areas in the northern The Appalachian Plateaus portion of the County and ranges in thickness Province is found in the west from 220 to 350 feet. The Group consists of and northwest portions of the variable layers of sandstone, shale, limestone, County and is characterized by clay and coal. (Bituminous coal has been nearly horizontal rock strata which have not extensively mined from this Group. Flint clay been deformed to any great extent by major has also been extracted from an area north of earth disturbances (tectonic forces)1. The Ridge Snow Shoe). Water is usually available in small and Valley Province is found in the south and quantities. southeast sections of the County. The angle of bedrock bedding, or dip, varies widely through Pottsville this area as result of folding. The fracturing of the rocks at the uppermost parts of the folds has The Pottsville Group of the Pennsylvanian accelerated the erosion of limestone strata. The System is comprised primarily of hard sandstone less easily eroded sandstone strata form the and forms extensive flat summits in the ridges which currently exist in the area. northwestern portion of the County. The Group includes three subdivisions, namely, Homewood Limestones and dolomites of the Cambrian and sandstone, Mercer shale and Connoquenessing Ordovician Systems are the most productive sandstone. The Homewood sandstone water-bearers in the County and supply several generally consists of large white or light gray large springs. The largest of these springs is coarse-grained sandstone. Mercer shale located at Bellefonte, the Big Spring. In areas underlies the Homewood sandstone and of the County where shale occurs, wells and consists of shale and clay. The springs do not yield as much water as might be Connoquenessing Sandstone is the lowest expected in limestone areas. The shale is, for Member of the Formation and is generally gray, the most part, highly fractured and does not hard, coarse, thick-bedded sandstone although confine water. Consequently, such areas are of in some areas it is white and fine-grained. Large little value as sources of underground water. quantities of water are likely to be found, Formations of the Mississippian and however, usually of poor quality with high Pennsylvanian Systems yield more water than mineral content. those which are comprised entirely of shale, although they are not usually as productive as Mauch Chunk Formation the limestone valleys. Soils formed from shale typically are not the best for agricultural uses. The Mauch Chunk Formation of the These soils usually are not drained, which poses Mississippian System is comprised of red shale challenges for development. Large scale with brown to greenish-gray sandstone. It is development on shale may face constraints from characteristic of this Formation that water is the tendency of this formation to slip when available in depths up to 100 feet. The water saturated. generally is of poor quality with a high iron content. Following is a map entitled Geologic Units (Figure 1) showing the major bedrock units of Pocono Group The Pocono Group of the Mississippian System consists primarily of hard, resistant sandstone 1 A good place to observe this is the Route 322 cut and includes two subdivisions: (1) Burgoon between Port Matilda and Philipsburg. As you drive sandstone comprises the upper portion of the north towards Philipsburg the angle of the rock gets Group and consists of thick-bedded, coarse, closer to horizontal. 2 Geologic Map of Centre County 3 yellowish-green to bluish-gray sandstone which chert. The New Scotland limestone consists of is locally conglomeratic. It ranges in thickness shale and impure limestone which contains from 300 to 525 feet. (2) The lower subdivision white chert with a thin basal limestone, and is unnamed and consists of gray, sandy shale, ranges in thickness from 10 to 60 feet. gray and red sandstone, red shale and locally, Generally, a good water-bearing Formation, beds of clay and conglomerate. Thin beds of although the water is hard, highly mineralized, coal may also be encountered locally. Water is and generally unsuitable for most uses without often present, particularly when the Group is extensive treatment. covered by the Mauch Chunk Formation. Water quality is usually good and soft. Keyser, Tonoloway, Wills Creek, Bloomsburg and McKenzie Formations Susquehanna Group These five Formations are of the Upper and The Susquehanna Group of the Upper Devonian Middle Silurian Series and outcrop in a narrow Series consists of three subdivisions: (1) band along the entire length of the north side of Oswayo Formation, primarily brownish and Bald Eagle Mountain in Centre County. They greenish, fine and medium grained sandstone are predominately thin bedded limestones with with some shales in the upper portion of the some sandstone in the middle Formations and Group; (2) Catskill Formation, chiefly red to some shale in the base layers. brownish shales and sandstone in the middle portion; and (3) Marine beds of gray to olive Port Matilda Borough’s and Howard Borough’s brown shales, graywackes and sandstones in public water supply wells draw from the Keyser- the bottom portion of the Group. Tonoloway Formations, and Mount Eagle’s public water supply is from the Wills Creek Hamilton Group Formation. The Hamilton Group of the Middle Devonian Clinton Group and Tuscarora Formation Series generally consists of brown, yellow, olive- green and black shales with some interbedded The Clinton Group and Tuscarora Formation are sandstones. These sandstones are thick and Members of the Lower Silurian Series which predominate in some areas. Water in moderate extend in a narrow band along the ridge of Bald quantity is found and often iron and hydrogen Eagle Mountain. The Clinton Group is sulphide are encountered. predominately made up of the Rose Hill Formation, a fossiliferous shale with some ‘iron Oriskany and Helderberg Formations sandstones’ and limestone. Quartzitic sandstone interbedded with shale lies above the These two Formations are of the Lower Rose Hill Formation. The ‘lower’ Tuscarora Devonian Series with the Oriskany Formation consists of a white to gray quartzitic stratigraphically lying above the Heiderberg. sandstone. The former consists of white to brown, partly calcareous, fossiliferous sandstone at the top Juniata, Bald Eagle and Reedsville Formations and below. The Helderberg Formation is comprised of Keyser limestone at the base, These three Formations of the Upper Ordovician Coeymans limestone in the middle and New Series outcrop extensively in the southern Scotland limestone at the top. The limestone portion of the County and in a narrow band forms a major portion of the Helderberg and along the southern side of Bald Eagle Mountain. consists of a lower series of limestones, usually with modular layers, and an upper series of The younger Juniata Formation crops out in relatively shaley limestones. It usually ranges high, narrow valleys between crests of from 90 to 200 feet in thickness. The Coeymans Tuscarora quartizite in the southeastern portion limestone varies in thickness from 3 to 10 feet of the County. The Formation is comprised and ranges in character from a coarse Crinoidal almost entirely of red or black shale and limestone which is sandy in the lower part to a sandstone. The sandstones are usually fine- calcareous sandstone which usually contains grained, micaceous and often cross-bedded. 4 Water is scarce, although sometimes found as The Nittany dolomite ranges in thickness from hillside springs. 1,000 to 1,250 feet and consists almost entirely of light gray or blue-gray, fine-grained dolomite The middle Bald Eagle Formation occurs in a which occurs in layers as thick as 2 feet. The very narrow band of gray to greenish gray Axemann limestone is a relatively pure, thin- sandstone. bedded, dark blue-gray limestone which contains only a few thin layers of dolomite and The older Reedsville Formation consists ranges in thickness from 50 to 500 feet. The primarily of brown, greenish and black clayey to Bellefonte dolomite consists primarily of dark, sandy shale, usually contains black shale in the fine-grained dolomite. It may be either thin, or lower portion, thin limestone beds at intervals, thick-bedded and includes a few light gray beds, and gray sandstone at the top. A reliable a little dove-colored limestone and some chert. source of water for domestic use sometimes It also contains a sandstone bed which reaches with high iron content. 15 feet in thickness in some areas but is absent in others. The dolomite is approximately 2,200 Coburn, Salona, Nealmont, Linden Hall, Benner, feet in thickness near Bellefonte. It is assumed Hatter, and Loysburg Formations that the white kaolinite clay deposit being mined near Stormstown is in the Beekmantown Group. These Formations of the Middle Ordovician Moderately hard water is found in good supply Series lie above the Beekmantown Group and, and oftentimes surface springs of ample flow are generally, are found stratigraphically in the order encountered. of listing with the Coburn Formation the uppermost. All of the Formations are basically Gatesburg Formation limestones with some shales found in the upper formations and some laminated dolomites in the The Gatesburg Formation of the Middle and bottom Loysburg Formation. The Linden Hall Upper Cambrian Series is characterized by a Formation, measuring up to 150 feet in thick soil and overburden mantle of residual thickness in the Nittany Valley, is the most sand and sandstone boulders and is comprised economically important to Centre County as its principally of thick-bedded, coarse, crystalline, upper Member, the Valentine is of an blue dolomite with some thin-bedded, fine- exceptionally pure limestone.