Allegheny Front Research Articles

Gravity surveys of central Pennsylvania

Gravity surveys in central Pennsylvania were made in an attempt to obtain information which could be related to subsurface structures near the Allegheny Front. Results show no distinct relationship between gravity anomalies and major structural folding; however, they do indicate an intrusion or upthrust of the basement east of the Allegheny Front. It is believed that this basement feature was responsible for the forces causing the northwestward structural salient in the Appalachian Mountain of central Pennsylvania.

Subsurface Upper Devonian Sections in Southwestern Pennsylvania

With the exception of small inlier areas along the axes of Chestnut Ridge and Laurel Ridge anticlines, the Upper Devonian rocks of western and southwestern Pennsylvania are concealed beneath a mantle of overlying Mississippian, Pennsylvanian, and Permian sediments. Thus, the study of this very important group of rocks becomes a problem for the subsurface stratigrapher in approximately half of the surface area of Pennsylvania. Drilling, in recent years, along Chestnut Ridge and Laurel Ridge anticlines and also in the broad plateau area between Laurel Ridge and the Allegheny Front has yielded many excellent sections based on detailed examinations of drill cuttings. Some of these sections, in a generalized graphic form, together with additional sections in the oil- and gas-p oducing area west of Chestnut Ridge, are assembled into cross sections which illustrate the facies variations in the Upper Devonian sediments of southwestern Pennsylvania. The Conewango (uppermost Upper Devonian) age of the Devonian rocks exposed in the inlier areas of Chestnut Ridge and Laurel Ridge anticlines is confirmed. With the exception of the Huntersville chert and Oriskany sandstone, which are Lower Devonian in age, the producing sands of southwestern Pennsylvania all appear to be younger than the highest sub-Catskill marine beds exposed along the Allegheny Front, which are generally considered as being late Chemung in age.

Developments in Pennsylvania in 1948

Exploratory drilling in the shallow-sand territory of western Pennsylvania (Upper Devonian or higher) during 1948 led to the discovery of 5 new gas pools and one oil pool. None of these, however, seems to be significant in size. The total number of shallow wells drilled, exclusive of those drilled in connection with underground gas storage and secondary-recovery oil operations, was 10 per cent less than in 1947. In the Pennsylvania part of the Bradford oil field, which continued to be the most active area, 2,070 new wells were completed, as compared with 1,840 in 1947. About half of these were water-intake wells. The Bradford field accounted for 80 per cent of the total oil production in Pennsylvania during 1948. The average daily oil production in the state in 1948 was 3 ,206 barrels, as compared with 35,242 barrels in 1947. Thirty new wells were completed to the deeper formations (Onondaga or deeper) as compared with 28 in 1947. Of these, two were drilled for gas storage purposes. Of the remainder, 9 were gas wells and 19 were dry holes. Two of the wells, located in Erie County, were completed as dry holes in the Corry Medina sand gas pool. They definitely established that this pool, discovered in 1948, is of only small extent. The greatest activity centered in the East Fork Oriskany sand gas pool of north-central Pennsylvania where 8 wells were completed, whose initial open-flow capacities ranged from 2 to 10 million cubic feet of gas per day. The limits of this pool have not been defined and this development, no doubt, will greatly stimulate further prospecting of the Oriskany underneath the Allegheny lateau in central Pennsylvania. The Cambro-Ordovician possibilities of the state received considerable attention during 1948. Several major companies conducted geological and geophysical surveys and one test on the Schellsburg dome east of the Allegheny Front in south-central Pennsylvania was underway at the end of the year.

Subsurface Upper Devonian Sections in Southwestern Pennsylvania: ABSTRACT

With the exception of small inlier areas along the axes of Chestnut Ridge and Laurel Ridge anticlines, the Upper Devonian rocks of southwestern Pennsylvania are concealed beneath a mantle of Mississippian, Pennsylvanian, and Permian sediments. Thus, the study of this very important group of rocks becomes a problem for the subsurface stratigrapher over a third of the surface area of Pennsylvania. Drilling, in recent years, along Chestnut Ridge and Laurel Ridge anticlines, and also in the broad plateau area between Laurel Ridge and the Allegheny Front, has yielded many excellent sections based on detailed examinations of drill cuttings. Some of these sections, in a generalized graphic form, together with additional ones located in the oil- and gas-producing area west of Che tnut Ridge, are assembled into cross sections which illustrate the facies variations in the Upper Devonian sediments of southwestern Pennsylvania. The Conewango (uppermost Upper Devonian) age of the Devonian rocks exposed in the inlier areas of Chestnut Ridge and Laurel Ridge anticlines is confirmed. With the exception of the Huntersville chert and Oriskany sandstone, which are Lower Devonian in age, the producing sands of southwestern Pennsylvania all appear to be younger than the highest sub-Catskill marine beds exposed along the Allegheny Front, which are generally considered as being late Chemung in age. End_of_Article - Last_Page 2161------------

Results of Studies of Ordovician Rocks East of Allegheny Front in Pennsylvania: ABSTRACT

The Ordovician rocks adjacent to the Allegheny Front consist of 6,500 feet of limestones, dolomites, and shales. The rocks become increasingly clastic upward, reflecting the growing movement that culminated in late Ordovician orogeny on the southeast. The Lower Ordovician consists of 2,775 feet of dolomite with two relatively thin limestone members. The homogenous lithology does not permit as detailed zoning as middle Ordovician limestones. However, a few lithic and faunal zones persist over fairly wide areas and are useful as mapping units. Some units may be helpful in subsurface geology in the adjacent Allegheny Plateau area. Middle Ordovician rocks, 1,375 feet thick, are divided into 15 major units which may be subdivided. Upper Ordovician clastics, 2,350 feet thick, c nsist largely of thick shales, claystones, siltstones, and sandstones which are not readily subdivided into characteristic zones. Favorable reservoir rock in the Ordovician is limited. However, coarse calcarenites of the Trenton and Black River may offer some promise. The foetid odor of hydrocarbons is noticeable throughout much of the Ordovician, especially in some of the clastic limestones. Coarse-grained limestones and dolomites are generally darker than the denser carbonates, the darkness of color roughly proportional to increasing grain size. The relationship of the hydrocarbon content to grain size in these rocks deserves further study. Beekmantown and Upper Cambrian dolomites show small carbonate-lined cavities having foetid odor, a few showing oil stains. The Upper Cambrian Gatesburg contains numerous coarse sandstone beds which probably offer better potential reservoir rock than Ordovician units. Several conclusions regarding the nature of the Ordovician rocks beneath the Allegheny Plateau may be based on outcrop data and paleogeographic probabilities. Gatesburg sandstones likely thicken and coarsen westward beneath the plateau. The Beekmantown dolomite probably thickens for a short distance beneath the plateau, with the limestone phases becoming more dolomitic. The Chazy probably thins and disappears in the central plateau area. Lower Black River units thin while upper Black River units thicken beneath the plateau for a short distance. Most Middle Ordovician units become more magnesian westward beneath the plateau. Upper Ordovician units become less clastic and thin westward. End_of_Article - Last_Page 2161------------

Middle Ordovician of Central Pennsylvania

Middle Ordovician formations outcrop in several anticlinal areas in central Pennsylvania between Path Valley and the Allegheny Front. There are about 1,500 feet of limestone and shale representing the Chazyan and Mohawkian series. A number of conclusions have been reached, and many problems remain to be solved. The area lies in the eastern part of the Allegheny stratigraphic belt, extending to the Adirondack axis, which passes along Path Valley; rocks in the Cumberland Valley on the southeast were formed in the Champlain miogeosynclinal belt. Of the Chazyan formations, the stratigraphy of the Loysburg formation is insufficiently known; the Hatter formation thins southeastward by overlap. The lower Mohawkian, Black River, Benner, and Curtin limestones thin southeastward to extinction beyond the Adirondack axis, principally through offlap and truncation. The higher Mohawkian, Trenton, formations are the Nealmont, Salona, and Coburn limestones and the Antes black shale. The Nealmont, lower Trenton, lies with pronounced regional unconformity on older rocks and thins by overlap from a maximum in a northeast-trending belt within the area of outcrop. The Salona, middle Trenton, is rather constant in lithology and thickness in most of the area, converging rapidly as it approaches the Adirondack axis. The distribution of the upper Trenton Co-burn and Antes formations is insufficiently known. The stratigraphy of the economically important Valentine "chemical" limestone, the upper member of the Curtin formation, has an important bearing on the understanding of the behavior and distribution of the unit. Metabentonites, present in the Benner, Curtin, Nealmont, and Salona limestones, permit more precise correlation of sections and interpretation of relationships than are normally possible.

Onondaga Group of Parts of West Virginia and Virginia: ABSTRACT

The Onondaga group discussed in this paper includes all rock units between the top of the Oriskany (Ridgeley) sandstone and the base of the Marcellus formation of the Hamilton group. It corresponds in part to the Corniferous of older reports and drillers' records. Within the area described it contains two separable lithologic members, an upper shale and a lower chert. In southeastern West Virginia the group is represented mainly by the Huntersville chert, which crops out in a belt about 120 miles long in Pocahontas, Greenbrier, Monroe, and Mercer counties. In Pocahontas and Greenbrier counties it is exposed on both flanks of the Browns Mountain anticline which lies west of the Allegheny Front. In Virginia and elsewhere in West Virginia it is confined to the Valley and Ridge physiographic province, where it has been traced as far south as Saltville, Virginia. The formation contains impure chert, highly silicified shale, silicified mudrock, and, commonly, one or more prominent glauconitic sandstones. In general the Huntersville has few fossils, but at some localities there occur numerous species which the author has identified and recorded. The Hunte sville chert occupies a stratigraphic position held in northeastern West Virginia and northwestern Virginia by a shale of Onondaga age which is believed to correspond with the Needmore shale of southern Pennsylvania. The chert appears to grade laterally into this shale, although where both units are represented, the shale invariably overlies the chert. Thus, the shale is partly younger than the chert. The upper Onondaga contact is apparently conformable, but an unconformity at the base reaches great magnitude at several localities in Virginia. End_Page 902------------------------------ Wells pentrating deep horizons in West Virginia, western Pennsylvania, and eastern Ohio encounter a limestone and chert unit at the general Onondaga level. This unit is the eastern subsurface extension of the Columbus limestone of Ohio and, probably, the analogue of the Onondaga limestone of New York. It is also the precise equivalent of the Huntersville chert. Commercial gas was discovered in it (1936) along the Chestnut Ridge anticline of southwestern Pennsylvania, and a recent Oriskany test well on the same structure encountered rock pressure of 3,275 pounds in the Huntersville. Most likely the chert is a reservoir only because of brecciation. The extreme brittleness of the Huntersville is attested on the outcrop by strong fragmentation wherever it is folded. This fact suggests its potential value as a gas and, possibly, an oil reservoir wherever deformation has caused brecciation at depth. End_of_Article - Last_Page 903------------

Hamilton group along the Allegheny Front, Pennsylvania

INTRODUCTION This paper is the concluding number of three articles on the Hamilton group of Pennsylvania, which the author has read at successive meetings of the Paleontological Society. In 1932 the first paper, prepared jointly with Arthur B. Cleaves,1 was given. It covered the eastern part of the State from the Delaware Valley to the Susquehanna Valley and also included observations on, and correlations of, the Hamilton of the Green Pond Mountain region, New Jersey. In 1933 the author read the second article of the series,2 which described the group in central Pennsylvania from the Susquehanna Valley west into Fulton and eastern Huntingdon counties. The present article covers the remaining portion of the State where rocks of Hamilton age are known at the surface. It will be necessary first to review previous observations before taking up the new region. The four formations of the Hamilton group of eastern Pennsylvania are . . .

Portage group in Pennsylvania

INTRODUCTION STRATIGRAPHIC LIMITS OF THE PORTAGE GROUP The Portage group in Pennsylvania is here defined as including all beds between the subjacent Hamilton and the overlying Chemung, recognized by the advent of Spirifer disjunctus . Where, in eastern portions, marine Chemung is absent, supplanted by the Catskill continental facies, the top of the Portage is indefinite.1 Nevertheless, occasionally this upper limit can be approximately fixed. The top of the Hamilton is often defined through the presence of a fossiliferous zone characterized by Vitulina pustulosa .2 A sharp lithologic change is recognized at the same point. Along the Allegheny Front the Portage group is introduced by the Tully limestone, which contrasts sharply with the Hamilton shales. Where the Tully is absent, the Burket (“Genesee”) black shale usually occurs and is faunally and lithologically distinct. Only in the most eastern sections is it difficult, because of lithologic and faunal convergence, to separate the Portage . . .

Chambersburg (Harrisburg) Peneplain in the Piedmont of Maryland and Pennsylvania

Research Article| June 30, 1933 Chambersburg (Harrisburg) Peneplain in the Piedmont of Maryland and Pennsylvania MARIUS R. CAMPBELL MARIUS R. CAMPBELL Search for other works by this author on: GSW Google Scholar GSA Bulletin (1933) 44 (3): 553–573. https://doi.org/10.1130/GSAB-44-553 Article history received: 21 Nov 1932 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation MARIUS R. CAMPBELL; Chambersburg (Harrisburg) Peneplain in the Piedmont of Maryland and Pennsylvania. GSA Bulletin 1933;; 44 (3): 553–573. doi: https://doi.org/10.1130/GSAB-44-553 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract IntroductionMany years ago, while engaged in field work in western Pennsylvania and eastern Ohio, the writer became interested in the geomorphic features there displayed and, after considerable study, became satisfied of the presence, some distance below the highest points in the landscape, of rather extensive remnants of a peneplain which, in all probability, was much younger than the Schooley (Kittatinny) peneplain that Davis and Wood2 had recognized farther east and described a few years previously, but he found no reliable data for a more accurate determination of its age. At that time little or no geomorphic work had been done in the western part of the State—Davis’s activities having been largely confined to the region east of the Allegheny Front and to the northern part of New Jersey—and no one had attempted to correlate the surface features east of the Allegheny Front with those in the coal . . . This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.