The Lower Ordovician series (Beekmantown group) is at least 3500 feet thick near Chambersburg, Pennsylvania, approximately 1200 feet thicker than was earlier estimated. Reverse faulting in the upper part of the section may have obscured the youngest Early Ordovician and oldest Middle Ordovician beds in the area, so that the total thickness of the Lower Ordovician series may be comparable to the thickness measured in Maryland. The Beekmantown group is represented by the Stonehenge limestone and the Rockdale Run formation. Moving the base of the Stonehenge downward to include about 200 feet of strata previously referred to the underlying Conococheague formation facilitates regional correlation without impairing mappability. Newly discovered fossils from the Rockdale Run formation add notably to the faunas of the upper part of that formation. Comparison of a trilobite-brachiopod faunule near the top of the Diparelasma zone (Cotter-Powell equivalent) with similar fossils in Zone J of the Utah-Nevada sequence suggests that Zone J may be no younger than the Powell dolomite of the Ozark region. Difficulty in recognizing correlatives of the Smithville and Black Rock formations suggests the need for restudy of these units in the Ozark region. Evidence from the Chambersburg section neither proves nor contradicts the hypothesis of continuous deposition from Early Ordovician to Middle Ordovician time in the central Appalachian area.

Pennsylvania↗

USGS1958

Geology of the northern half of the Minersville quadrangle and a part of the northern half of the Tremont quadrangle, Schuylkill County, Pennsylvania

No abstract available.

Pennsylvania↗

USGS1958

Hydraulic and hydrologic aspects of flood-plain planning

The valid incentives compelling occupation of the flood plain, up to and even into the stream channel, undoubtedly have contributed greatly to the development of the country. But the result has been a heritage of flood disaster, suffering, and enormous costs. Flood destruction awakened a consciousness toward reduction and elimination of flood hazards, originally manifested in the protection of existing developments. More recently, increased information and realization of the problem have shown the impracticability of permitting developments that require costly flood protection. The idea of flood zoning, or flood-plain planning, has received greater impetus as a result of such realization. This study shows how hydraulic and hydrologic data concerning the flood regimen of a stream can be used in appraising its flood potential and the risk inherent in occupation of its flood plain. The approach involves the study of flood magnitudes as recorded or computed; flood frequencies based on the experience shown by many years of gaging-station record; use of existing or computed stage-discharge relations and flood profiles; and, where required, the preparation of flood-zone maps to show the areas inundated by floods of several magnitudes and frequencies. Methods are outlined that will enable the planner to delineate areas subject to inundation by floods of specific recurrence intervals for three conditions; (1) for the immediate vicinity of a gaging station, (2) for a gaged stream at a considerable distance from a gaging station, and (3) for an ungaged stream. Curves have been developed from which the average depth for a flood of specific frequency can be estimated on the basis of the average depth for bankfull flow; this simplified approach should be very useful in the initial stages of flood-plain planning. Brief discussions are included on various types of flood hazards, the effects of urbanization on flood runoff, and zoning considerations.

Pennsylvania↗

USGS1957

Progress report of hydrology and sedimentation in Bixler Run, Corey Creek, and Elk Run watersheds, Pennsylvania

This report describes the results of an investigation in progress and presents some tentative findings from a study of hydrology and sedimentation of three small watersheds where soil conservation practices are being applied. The study was begun in April 1954, to determine precipitation, runoff, probable sources and yields of sediment, and channel changes in two small watersheds in Pennsylvania. This report covers the period April 1954, to September 30, 1955 with the exception of the aggradation-degradation range data which covers the period October 1954 to November 1956. The internal or time control method of calibration is being used for the Bixler Run watershed study, and an external control is being used in the Corey Creek study. Precipitation on Bixler Run watershed was 47.33 inches for the 1955 water year. Total runoff was 14.08 inches and the suspended sediment yield was 1,143.3 tons or 76 tons per square mile of drainage area. Precipitation on Corey Creek watershed for the same period totaled 35.81 inches. The total runoff was 8.37 inches and the suspended-sediment yield was 713.0 tons or 58.2 tons per square mile of drainage area. The precipitation on Elk Run, external control watershed for the Corey Creek study was 34.54 inches. The runoff was 10.10 inches and the suspended sediment yield was 709.9 tons or 69.5 tons per square mile. Results from the study of channel changes by means of sediment aggradation-degradation ranges showed fill in all three watersheds. Bixler Run showed an average channel fill of 1.3 square feet per stream cross section. Corey Creek and Elk Run watersheds showed average fills of 2.9 and 4.1 square feet per cross section respectively. Most of the sediments comprising this fill were in the particle size range of gravel and coarser material. The water in all three watersheds was low in dissolved solids during the period of investigation, varying from 72 to 127 ppm in Bixler Run, from 58 to 130 ppm in Corey Creek, and from 58 to 117 ppm in Elk Run. These waters are essentially of the secondary alkaline type with calcium and magnesium bicarbonate being the main dissolved constituents.

Pennsylvania↗

USGS1956

Surficial geology and geomorphology of Potter County, Pennsylvania

Potter County is located in the Appalachian Plateaus of north-central Pennsylvania and contains the headwaters of the Genesee River, the Allegheny River, and the Susquehanna River. Drift of Wisconsin age covers the northeastern part of the county. This study includes a detailed survev of the surficial deposits of the Genesee quadrangle in north-central Potter County and a reconnaissance of the remainder of the county; a soil survey and a botanical survey were carried on concurrently. The region is a deeply dissected plateau having extensive areas of steeply sloping land separated by narrow ridges and valleys; there is very little level land. Near the junction of the three watersheds the uplands rise to altitudes of more than 2,500 feet. The maximum relief in the Susquehanna drainage is more than 1,500 feet; in the Genesee and Allegheny drainage it. is about 800 feet. Valley walls are steep (15° to 30°), and the uplands have gentle slopes (0.5° to 10°). The drainage pattern is trellised. The climate is continental. Temperatures range from about -30° F. to more than 100° F. The average annual precipitation ranges approximately from 34 to 42 inches. Floods may occur at any season of the year. The large volumes of water from rain or melting snow carried by small streams come from springs. There is little precise data on frost in the ground, but it is probable that the ground seldom freezes in forested areas. The soils of Potter County have relatively immature profiles with poorly developed horizons that commonly have many characteristics inherited from their parent materials. At the great soil group level, the zonal soils are divided into Podzol soils and Brown Podzolic soils. Many soils have a high silt content in the upper part of the profile, apparently derived (at least partly) from a mantle of eolian silt. Mos~ of Potter County is covered by second-growth forests consisting of 40- to 60-year-old hardwood stands. The present forests growing on slopes and summits are composed approximately of 25 species of trees. The northern hardwood region includes most of the county, with an oak-forest region near the borders, principally along its southern margin. Potter County is underlain by sandstone, siltstone, shale, conglomerate, and minor amounts of coal and calcareous rock that range in age from Late Devonian to Pennsylvanian. These rocks form broad open folds that strike northeast. South of the border of the Wisconsin drift, and possibly at two localities inside the drift border, are scattered remnants of ancient soils (here called paleosol), that were formed in preWisconsin time-probably during the Sangamon interglacial stage. This paleosol ranges in texture from clay loam to silt loam, ranges in color from yellowish red to red, includes a few percent to more than 25 percent of rock fragments, and apparently contains a small percentage of gibbsite and varying amounts of kaolinite. Known thicknesses range from 1 to 33 feet. Paleosol was developed on diverse kinds of parent material, such as till, stratified drift, colluvium, and residuum, at altitudes ranging from a few hundred to 2,400 feet. The climatic conditions under which the paleosol formed are uncertain; however, these ancient soils may record an episode of subtropical climatic conditions during which lateritic soils were formed. Perhaps these soils are analogous to the Red-Yellow Podzolic soils of southeastern United States. Except for one possible remnant, no pre-Wisconsin drift has been recognized in Potter County. The Wisconsin glacial deposits of Potter County belong to either the Iowan or Tazewell substages and are dominantly till with minor amounts of glaciofluvial deposits. Erratics of igneous or metamorphic rock comprise less than 0.1 percent of the total number of rock fragments. The till is slightly weathered to depths ranging from 3 to about 12 feet. The drift border is indefinite and has been drawn at the southern limit of erratics or well-rounded or striated pebbles and is only locally marked by a terminal moraine or by a distinct change in the surficial deposits. The drift border is relatively straight and crosses the Genesee quadrangle in a northwesterly direction with little regard for the major topographic features, thus suggesting that the Wisconsin ice sheet had a relatively straight and steep front. Over most of the unglaciated part of Potter County, the bedrock is concealed beneath rubble that probably was formed during the Iowan or Tazewell substage, almost contemporaneously with the adjacent drift. In general, the rubble is thickest and most extensive within about 10 miles of the drift border, becoming thinner and less continuous farther away. The apparent parallelism between a belt of thick periglacial deposits and the drift border suggests that the deposits result from climatic factors in operation while the Wisconsin ice sheet was nearby. Ancient soil structures or patterned ground occur at, or near, the surface of both the periglacial deposits and the adjacent drift. These ancient soil structures are so similar to modern forms in arctic or alpine environments that they are considered to be the result of vigorous frost action. Many of the structures are believed to be a result of down-slope movement of debris by solifluction, facilitated by a frozen subsoil as much as 10 feet deep. Perennially frozen ground may have been present, but this is not a prerequisite. The periglacial deposits underlie long smooth slopes that extend from ridge crest to valley bottom. Flood plains are absent near the headwaters of many streams, the valley walls forming a V-shaped profile. While frost action was in progress, forests probably were restricted to flood plains, lower slopes, and scattered upland areas. Large parts of the upland were bare or partly covered by tundra vegetation; elsewhere, there were scattered trees but no dense forest. 1 2 SURFICIAL GEOLOGY AND GEOMORPHOLOGY OF POTTER COUNTY, PENNSYLVANIA Recent alluvium and alluvial fans include sand and sandy loams, 1 to 3 feet thick, that overlie gravel. The alluvium contains organic matter and lenses of finer materials. Thickness ranges from a few to more than 100 feet. Along the principal streams the alluvium probably overlies Pleistocene deposits. Most of the alluvial fans are composed of unstratified rubbly, pebbly, cobbly. or bouldery sandy loams to silty clay loams with local lenses of stratified sand and gravel. The alluvial fans mapped in the Genesee quadrangle probably include both Wisconsin stage and Recent deposits. The summits of the A.ppalachian Plateaus in north-central Pennsylvania have long been recognized as the remnants or traces of one or more peneplains. To test this hypothesis, a restored contour map was prepared to show the configuration of a supposed peneplain on the assumption that the plateau tops are remnants of such an old erosion surface. The restored contours delineate a surface that corresponds roughly to rock structure. In general, the uplands slope parallel to the dip of the bedrock. The major streams, such as the West Branch Susquehanna River, cross the ridges and valleys of the restored surface in such a way that it is difficult to suppose that the restored surface was ever graded to these streams. On the contrary, it is probable that the restored surface never existed and that the plateau tops are structurally controlled surfaces held up by sandstone and conglomerate beds in the Pottsville and Pocono formations. The plateau tops may have been lowered by erosion as much as 200 feet during the Pleistocene-in other words, after the major streams were incised. If this portion of the Appalachian Plateaus was ever reduced to a peneplain, such a hypothetical surface must have lain many hundreds of feet above the uplands of the present day. The only alternative that might involve peneplanation is the improbable hypothesis that the plateau tops are remnants of a slightly deformed peneplain and that the peneplain was folded along the axes of the Appalachian orogeny. This remote possibility is not supported by any known evidence. The geomorphic analysis yields no new data on the origin of the cross-axial drainage. Regardless of whether the plateaus are peneplain remnants or are structurally controlled surfaces, the beginning of the major southeastward-flowing streams long antedates the existing landscape. The geomorphic history of Potter County begins with an assumed long interval of erosion during the Mesozoic and early Cenozoic eras, for which no record remains in this area. The southeast master drainage was established by the latter part of the Tertiary period (perhaps at a much earlier date), probably as the result of the northwestward migration of the Atlanticinterior divide. In late Pliocene(?) time, areas adjacent to parts of the West Branch Susquehanna River-and probably elsewhere-had a moderate relief ranging from 300 to 700 feet. Some segments of the West Branch meandered across a broad valley that lay about 900 feet above the present streams. The landscape probably was covered by deep residual soils, perhaps by saprolite. The early Pleistocene history of Potter County is essentially unknown. No deposits of the Kansan stage are known except for a possible trace of pre-Illinoian drift on the uplands in central Potter County (Ayers Hill quadrangle). Some deposits in central and eastern Pennsylvania may be of Kansan age. It is probable that the assumed Aftonian regolith was removed by mass movements and other processes during the Kansan stage, thus resulting in a lowering of the plateau tops by as much as 10 feet. By the close of the Yarmouth(?) interglacial stage the major streams were incised to essentially their present depths. The climates of the Yarmouth interglacial stage probably produced deep residual soils over the landscape, parts of which may still be preserved in the paleosol remnants of the present day. No Illinoian drift is known in Potter County, but drift assigned to this stage occurs in areas to the northwest and to the southeast. Some valleys, such as Kettle Creek valley, were filled with sand and gravel alluvium to depths of as much as 150 feet above their present flood plains. It is assumed that the Yarmouth residual soils were removed by mass movements and other processes induced by a periglacial climate, thus lowering the plateau tops by as much as 10 feet. During the Sangamon interglacial stage, deep (10-to-20 foot) residual soils or paleosol were developed in Potter County and probably throughout much of Pennsylvania, perhaps as a result of lateritic weathering in a subtropical climate. It is possible that the paleosol was largely removed by mass movements and by running water during late Sangamon time. During either the Iowan or Tazewell substages of the Wisconsin (perhaps the Iowan), the ice sheet advanced into the northeastern part of Potter County. The drift is similar to the Olean drift (local usage). The paleosol was almost completely removed by mass movements and other processes induced· by a periglacial climate, prior to drift deposition. This removal probably resulted in a lowering of the plateau tops by as much as 10 feet since Sangamon time. Nearly contemporaneously with drift deposition, the periglacial deposits were formed by frost heaving, solifluction, and fluvial transport in areas outside the drift border. Soil structures or patterned ground were developed on both the drift and the periglacial deposits. It is probable that the forests in the periglacial area were greatly restricted and that large areas on the uplands were essentially treeless. Little is known about the history of Potter County in postOlean time. Presumably, forests completely covered the county by the onset of the next substage, during which the Binghamton drift of MacClintock and Apfel was deposited. This drift also is found in southern New York State. The formation of the alluvium and alluvial fans probably began in the Tazewell substage and continued during the Recent epoch. Since these deposits were formed there has been very little dissection. There is little, if any, difference between soils developed on periglacial deposits and soils developed on drift. The roots of fallen trees have disturbed the soil horizons, and it is unlikely that the existing soil profiles are more than 500 years old. The forested landscape of Potter County has a distinctive microrelief ranging from a few inches to a few feet of mounds and pits produced by the roots of fallen trees. Most mounds and pits range from 10 to 20 feet in length and from 6 to 15 feet in width. On level land, many mounds are oriented with their long axes trending northward, and in some areas the orientation is random. On slopes, the mounds are oriented with their long axes at right angles to the maximum slope as a result of trees falling downslope. The toppling of trees increases the permeability of surficial deposits and mixes and destroys the soil horizons. The microrelief is a factor in forest development. The toppling of trees on slopes is a significant agent of slope erosion. The process loosens, breaks up, or overturns the upper 2 to 3 feet of the forest soil, and it tends to make the surficial layer more stony and to produce features resembling soil structures.

Pennsylvania↗

USGS1955

The natural channel of Brandywine Creek, Pennsylvania

This study of the channel of Brandy wine Creek, Pennsylvania, consists of three parts. The first is an analysis of the changes which take place in the width, depth, velocity, slope of the water surface, suspended load, and roughness factor with changing discharge below the bankfull stage at each of several widely separated cross sections of the channel. Expressed as functions of the discharge, it is found that the variables behave systematically. In every section studied, as the discharge increases, the velocity increases to about the 0.6 power, depth to the 0.4, and load to the 2.0 power of the discharge. The roughness decreases to the 0.2 power of the discharge. The relative magnitudes and the direction of these variations are similar to those which have been observed in other rivers in the United States, primarily in the West. Some modifications of the hypotheses applicable to the western rivers are probably required because on Brandywine Creek the difference between the materials on the bed and in the banks is considerably greater than it is on most of the western rivers studied. In the second part of the paper the progressive changes of the same variables in the downstream direction with increasing discharge at a given frequency are described. Despite the disorderly appearance of the stream, it is found that the variables display a progressive, orderly change in the downstream direction when traced from the headwater tributaries through the trunk stream of Brandywine Creek. At a given frequency of flow, width increases with discharge to about the 0.5 power. Depth increases downstream somewhat less rapidly, while the slope and roughness both decrease in the downstream direction. Despite a decrease in the size of the material on the bed, both the mean velocity and the mean bed velocity increase downstream. The rates of change of these variables are in close accord with the changes observed on rivers flowing in alluvium and in stable irrigation canals. These relationships hold for all flows up to the bankfull stage. Analysis of the streamflow records indicates that the annual maximum discharge equals or exceeds the bankfull stage roughly once every 2 years. The regularity in the behavior of the variables with changing discharges both at-a-station and in the downstream direction and the similar rates of change of the variables on Brandywine Creek and in stable irrigation canals suggest the existence of a quasi-equilibrium in the channel of the creek. Part three of this study is concerned with this concept of equilibrium in streams. By analogy with canals and with several rivers in diverse regions of the United States it may be concluded that this quasi-equilibrium is closely related to the discharge, and to the concentration of the suspended load. The shape and longitudinal profile of the channel are determined by these two independent factors which operate within the limits set by the local geology. The latter determines the initial size, shape, and resistance of the material provided to the channel. The existence of a quasi-equilibrium among the variables studied suggests that most reaches on Brandywine Creek are at grade. This is true if the term "grade," when applied to natural rivers, is synonymous with quasi-equilibrium. The adjustability of the variables in the channel rather than the stability of any particular shape or longitudinal profile of the channel is emphasized when t

Pennsylvania↗

USGS1954

Geology of anthracite in the eastern part of the Ashland quadrangle, Pennsylvania

No abstract available.

Pennsylvania↗