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At least 1,621 records · Page 90Linked to original sources
USGS1999

Computer Program for Point Location And Calculation of ERror (PLACER)

A program designed for point location and calculation of error (PLACER) was developed as part of the Quality Assurance Program of the Federal Highway Administration/U.S. Geological Survey (USGS) National Data and Methodology Synthesis (NDAMS) review process. The program provides a standard method to derive study-site locations from site maps in highwayrunoff, urban-runoff, and other research reports. This report provides a guide for using PLACER, documents methods used to estimate study-site locations, documents the NDAMS Study-Site Locator Form, and documents the FORTRAN code used to implement the method. PLACER is a simple program that calculates the latitude and longitude coordinates of one or more study sites plotted on a published map and estimates the uncertainty of these calculated coordinates. PLACER calculates the latitude and longitude of each study site by interpolating between the coordinates of known features and the locations of study sites using any consistent, linear, user-defined coordinate system. This program will read data entered from the computer keyboard and(or) from a formatted text file, and will write the results to the computer screen and to a text file. PLACER is readily transferable to different computers and operating systems with few (if any) modifications because it is written in standard FORTRAN. PLACER can be used to calculate study site locations in latitude and longitude, using known map coordinates or features that are identifiable in geographic information data bases such as USGS Geographic Names Information System, which is available on the World Wide Web.

Open-File Report↗
USGS1977

Proceedings of the first annual William Pecora Memorial Symposium, October 1975, Sioux Falls, South Dakota

The U.S. Geological Survey agreed to publish the proceeding of the first annual William T. Pecora Memorial Symposium in its Professional Paper series because the subject material is related to the mission of the Survey. The usual standards for this series have been modified to accommodate the variety of styles used by the participants in this symposium. All color illustrations are placed at the front of the book for economy in printing. They are identified by the names of the authors of the papers from which they are extracted.

Professional Paper↗
USGS1979

Subsurface stratigraphy and geochemistry of late Quaternary evaporites, Searles Lake, California, with a section on radiocarbon ages of stratigraphic units

Searles Lake is a dry salt pan, about 100 km 2 in area, that lies on the floor of Searles Valley, in the desert of southeast California. Several salt bodies of late Quaternary age lie beneath the surface, mostly composed of sodium and potassium carbonate, sulfate, chloride, and borate minerals. Mud layers separate the salt bodies, which contain interstitial brine that is the source of large quantities of industrial chemicals. The value of annual production from the deposit exceeds $30 million; total production to date exceeds $1 billion. The salts and muds were deposited during Pleistocene and Holocene times by a series of large lakes (200 m maximum depth, 1,000 km 2 maximum area) that fluctuated in size in response to climatic change. Salts were deposited during major dry (interpluvial) episodes, muds during wet (pluvial) episodes that correlate with glacial advances in other parts of North America and the world. Data based on cores from the deposit are used in this paper to establish the stratigraphy of the deposit, the chemical and mineral compositions of successive units, and the total quantities of components contained by them. These parameters are then used to determine the geochemical evolution of the sedimentary layers. The results provide a refined basis for reconstructing the limnology of Searles Lake and the regional climate during late Quaternary time. Six main stratigraphic units were distinguished and informally named earlier on the basis of their dominant composition: Unit Typical thickness 14C age, uncorrected (in meters) (years B.P.) Overburden Mud 7 0 to >3,500 Upper Salt 15 >3,500 to 10,500 Parting Mud 4 10,500 to 24,000 Lower Salt 12 24,000 to 32,500 Bottom Mud 30 32,500 to 130,000 Mixed Layer 200+ > 130,000 (The age of 130,000 years for the Mixed Layer is based on extrapolated sedimentation rates.) The Lower Salt is subdivided into seven salt units (S-l to S-7) and six mud units (M-2 to M-7), the Mixed Layer into six units (A to F). For each salt unit, the areal extent, volume, shape, mineralogy, and chemical composition of the solids and brines have been determined; for each mud unit (which originally extended over much of the basin), the shape and volume within a standard area, and the mineralogy, have been determined. The bulk compositions (brines plus salts) of the combined Lower Salt units S-l to S-5 and units S-6 and S-7, and the Upper Salt, were determined so that the total quantities and ratios of ions in the initial brines could be reconstructed. The 74 published HC dates on Searles Lake core samples from all but the oldest unit are supplemented by 14 new dates (determined by Minze Stuiver) on the Lower Salt. Most of the age control comes from dates based on disseminated organic carbon; two dates are on wood; dates on carbonate minerals are less reliable. Although the probable disequilibrium between the carbon in the lake and atmosphere (because of contamination, slow equilibrium rates, and other factors) causes disseminated carbon dates to be an estimated 500-2,500 years 'too old,' the ages of the major and minor units are relatively well established. The list above indicates rounded and uncorrected ages for the contacts of major units. The age of the only salt bed in the Lower Salt which indicates desiccation (S-5) is about 28,000 years. The average uncorrected sedimentation rate in the Parting Mud is 4

Professional Paper↗
USGS1979

Upper Cenozoic sediments of the lower Delaware Valley and the northern Delmarva Peninsula, New Jersey, Pennsylvania, Delaware, and Maryland

The 'yellow gravels' referred to by R. D. Salisbury in 1898 and the 'Trenton gravel,' as defined by H. C. Lewis in 1880, were investigated along the inner edge of the New Jersey Coastal Plain in southern New Jersey and in the northern Delmarva Peninsula. The highest level deposits, the Beacon Hill gravel, are found on only the highest hills in the New Jersey Coastal Plain. Their distribution suggests deposition from north to south across the plain. After deposition of the Beacon Hill, probably in middle or late Miocene time, a narrow valley was formed paralleling the inner edge of the New Jersey Coastal Plain between Raritan Bay and Camden. South of Camden, the valley broadened, covering much of southern New Jersey. The deposits in this valley are largely the Bridgeton Formation as we have redefined it. A second narrow valley was entrenched through the Bridgeton between Trenton and Salem, N.J. This valley broadens and covers much of the northern Delmarva Peninsula west of the Delaware River. The fill in the valley is largely the Pensauken Formation, as we have redefined it in our report. Collectively, the Beacon Hill, the Bridgeton, and the Pensauken were originally the 'yellow gravels' of Salisbury. These deposits are all fluviatile in origin and were largely formed as a series of step like downcutting channels. The Delaware Valley between Trenton and the lower Delaware Bay region is occupied by the 'Trenton gravel,' which is below the average level of the 'yellow gravels.' Two units recognized throughout the area and informally named the Spring Lake beds and the Van Sciver Lake beds are lithologically distinct from the 'yellow gravel' formations. The lithologies of the Spring Lake beds and the Van Sciver Lake beds are much more heterogeneous than those of the older formations. These two units, particularly, contain much greater amounts of silt and clay, often in thick beds. The depositional environments associated with the two units include fluviatile, estuarine, and marginal marine. Both these units are interpreted to be late Pleistocene (Sangamonian) in age.

Delaware, Maryland, New Jersey, Pennsylvania↗
USGS1918

Stratigraphy of the Hanna Basin, Wyoming

Carbon County, Wyo., has attracted the attention of geologists since the days of the territorial surveys under King, Hayden, and Powell. During this earlier work all the rocks (except the North Park formation) over-lying the uppermost beds of marine origin were grouped in a single formation, for which the name Laramie was proposed.

Wyoming↗
USGS1981

Chemical composition of sedimentary rocks in California and Hawaii

A compilation of published chemical analyses of sedimentary rocks of the United States was undertaken by the U.S. Geological Survey in 1952 to make available scattered data that are needed for a wide range of economic and scientific uses. About 20,000-25,000 chemical analyses of sedimentary rocks in the United States have been published. This report brings together 2,312 of these analyses from California and Hawaii. The samples are arranged by general lithologic characteristics and locality. Indexes of stratigraphy, rock name, commercial uses, and minor elements are provided. The sedimentary rocks are classified into groups and into categories according to the chemical analyses. The groups (A through F2) are defined by a system similar to that proposed by Brian Mason in 1952, in which the main parameters are the three major components of sedimentary rocks: (1) uncombined silica, (2) clay (R203 ? 3Si02 ? nH20), and (3) calcium-magnesium carbonate. The categories are based on the degree of admixture of these three major components with other components, such as sulfate, phos- phate, and iron oxide. Common-rock, mixed-rock, and special-rock categories apply to rocks consisting of 85 percent or more, 50-84 percent, and less than 49 percent, respectively, of the three major components combined. Maps show distribution of sample localities by States; triangular diagrams show the lithologic characteristics and classification groups. Cumulative-frequency curves of each constituent in each classification group of the common-rock and mixed-rock categories are also included. The numerous analyses may not adequately represent the geochemical nature of the rock types and formations of the region because of sampling bias. Maps showing distribution of sample localities indicate that many of the localities are in areas where, for economic or other reasons, special problems attracted interest. Most of the analyzed rocks tended to be fairly simple in composition - mainly mixtures of just two of the three major components or a mixture of these and a fourth component such as phosphate, gypsum, or iron oxide.

Professional Paper↗
USGS1980

The Boulder Creek Batholith, Front Range, Colorado

The Boulder Creek batholith is the best known of several large Precambrian batholiths of similar rock composition that crop out across central Colorado. The rocks in the batholith belong to the calc-alkaline series and range in composition from granodiorite through quartz diorite (tonalite) to gneissic aplite. Two rock types dominate': the Boulder Creek Granodiorite, the major rock unit, and a more leucocratic and slightly younger unit herein named Twin Spruce Quartz Monzonite. Besides mafic inclusions, which occur mainly in hornblende-bearing phases of the Boulder Creek Granodiorite, there are cogenetic older and younger lenses, dikes, and small plutons of hornblende diorite, hornblendite, gabbro, and pyroxenite. Pyroxenite is not found in the batholith. The Boulder Creek Granodiorite in the batholith represents essentially two contemporaneous magmas, a northern body occurring in the Gold Hill and Boulder quadrangles and a larger southern body exposed in the Blackhawk and the greater parts of the Tungsten and Eldorado Springs quadrangles. The two bodies are chemically and mineralogically distinct. The northern body is richer in CaO and poorer in K2O, is more mafic, and has a larger percentage of plagioclase than the southern body. A crude sequence of rock types occurs from west to east in the batholith accompanied by a change in plagioclase composition from calcic plagioclase on the west to sodic on the east. Ore minerals tend to decrease, and the ratio potassium feldspar:plagioclase increases inward from the western contact of the batholith, indicating that the Boulder Creek batholith is similar to granodiorite batholiths the world over. Emplacement of the Boulder Creek batholith was contemporaneous with plastic deformation and high-grade regional metamorphism that folded the country rock and the batholith contact along west-northwest and north-northwest axes. Also, smaller satellitic granodiorite bodies tend to conform to the trends of foliation and fold axes in the country rock, suggesting that emplacement was controlled by preexisting structures in the country rock. On a gross scale, chemical equilibrium in the Boulder Creek Granodiorite is expressed by a near 1:1 ratio, or straight-line relationship in the distribution of iron, magnesium, and manganese in biotite and hornblende. General mineralogical trends in the Boulder Creek Granodiorite indicate that modal biotite, hornblende, and plagioclase tend to increase and quartz and microcline tend to decrease as CaO increases. These trends were not found in the Twin Spruce Quartz Monzonite. Differentiation is believed to have played a major role and assimilation a minor role in the development of the Boulder Creek batholith. The Boulder Creek Granodiorite is of probable mantle or lower crust origin, and, based on the scant data available, the Twin Spruce Quartz Monzonite may be of crustal origin, but the magma was extensively altered by contaminants of ambiguous origin. Mafic inclusions, possibly derived from a dioritic magma which was an early differentiate associated temporally with the Boulder Creek Granodiorite and (or) the Twin Spruce Quartz Monzonite, were in jected into the Boulder Creek Granodiorite during the mush stage and before the batholith was completely crystallized. Biotite, hornblende, and potassium feldspar were studied extensively. Their chemistry and petrology indicate a homogeneity throughout the batholith not believed possible by a casual observance of the batholithic rocks in the field. The accessory minerals, where investigated, also tend to indicate this same pervasive homogeneity.

Professional Paper↗
USGS1980

Shorter contributions to stratigraphy and structural geology, 1979

PART A: A system of anticlines lies along the trend of the sinuous course of the Colorado River for a distance of 97 km in the central Grand Canyon. Similar anticlines occur in some perennially wet side canyons. The anticlines are most abundant and well developed along northeast-trending reaches of the main canyon where it is floored by the Cambrian Muav Limestone. Dips of the folded strata are as great as 60?, and the folding locally extends more than 250 m from the river. Low-angle thrust faults in the limbs of the anticlines parallel the river and have formed in response to folding of the comparatively brittle carbonate strata. High-angle reverse kink bands, along which rocks are displaced up toward the river, also parallel the anticlines and have develop2d in response to the upward bulging of the canyon floor. The river anticlines are an unloading phenomenon. They result from lateral squeezing toward the river of saturated shaly parts of the Muav Limestone and underlying Bright Angel Shale. The driving mechanism for the deformation is a stress gradient that results from a difference in lithostatic load between the heavily loaded rocks under the 650-m-high canyon walls and the unloaded canyon floor. Saturation appears to weaken the shaly rocks sufficiently to allow deformation to take place. River anticlines are not present in the eastern Grand Canyon, where the Cambrian rocks also occur at river level. Their absence is explained by a lack of shaly rocks that could flow when saturated. PART B: The current interest in contemporary tectonic processes in the Eastern United States is turning up abundant evidence of crustal movements in late geologic time. Topographic analysis of the highland areas from the southern Blue Ridge to the Adirondack Mountains indicates that most of the landforms owe their origin to erosion of rocks of different resistance rather than to tectonic processes. Most areas of high relief and high altitude have been formed on resistant rocks. The Cambrian and Ordovician belt, containing mostly shale and carbonate rock, on the other hand, forms an extensive lowland from Alabama to the Canadian border and girdles the Adirondack Mountains. Differences in altitude can be explained by the presence of resistant rocks outside the belt; these resistant rocks form local base levels on the streams that drain the belt. A few areas may have undergone local uplift at a higher rate than areas nearby--for example, the Piedmont region northwest of Chesapeake Bay. Most estimates of erosion rates, based on the load transported by streams and of uplift rates, based on removal during a known period of time, are of the same order of magnitude, averaging almost 4x 10^-2 millimeters per year. Rates of uplift, based on study of tilted Pleistocene beaches and repeated geodetic traverses, are at least an order of magnitude higher for comparable areas. Tectonic uplift of the highlands has been slow and involves mostly warping or tilting on a large scale. Erosion rates keep up with or exceed the rate of uplift and have been sufficient to mask evidence of faulting or other differential movements. The high rates of uplift that are inferred on tilted water planes in the glaciated regions or that are measured by differences in repeated geodetic traverses cannot have been sustained for long periods of time. PART C: The Hanson Creek Formation southwest of Eureka, Nev., in the Bellevue Peak Quadrangle is composed of three lithostratigraphic members: (1) a basal dark-gray dolomite, (2) a middle silty thin- to thick-bedded, locally nodular, dark-gray, light-yellow-mottled limestone topped by light-gray dolomite, and (3) an upper dark-gray dolomite, which is herein named the Combs Canyon Dolomite Member. Detailed geologic mapping and accompanying fossil collecting prove that the same lithostratigraphic and biostratigraphic sequence is present in the Mountain Boy Range and 11 km to the south near Wood Cone Peak. Minor differences in

Professional Paper↗
USGS1980

Revised nomenclature and stratigraphic relationships of the Fredericksburg Complex and Quantico Formation of the Virginia Piedmont

The Fredericksburg Complex, in part a migmatitic terrane in northeast Virginia, is subdivided on the basis of lithology, as well as aeromagnetic and aeroradiometric data, into two metamorphic suites. These suites are separated by the northeast-trending Spotsylvania lineament, a rectilinear geophysical feature that is probably the trace of an old fault zone. East of the lineament, the Po River Metamorphic Suite, of Proterozoic Z and (or) early Paleozoic age, consists dominantly of biotite gneiss, generally augen gneiss, and lesser amounts of hornblende gneiss and mica schist. West of the Spotsylvania lineament is the Ta River Metamorphic Suite, composed mostly of amphibolite and amphibole gneiss. However, to the southwest, along its strike belt, the Ta River contains abundant biotite gneiss and mica schist. Both the Ta River and Po River contain abundant foliated granitoid and pegmatoid bodies as concordant tabular masses and as crosscutting dikes; these rocks are considered part of the Ta River and Po River Metamorphic Suites. The amphibolitic Holly Corner Gneiss is interpreted to be a western allochthonous equivalent of the Ta River. Both the Ta River and Holly Corner are considered to be coeval, eastern, distal facies of the Lower Cambrian(?) Chopawamsic Formation. The Paleozoic Falls Run Granite Gneiss intrudes the Ta River Metamorphic Suite and the Holly Corner Gneiss; locally the Falls Run is interpreted to have been transported westward with the Holly Corner after intrusion. The Quantico Formation, in the core of the Quantico-Columbia synclinorium, rests with angular unconformity along its northwest and southeast limbs, respectively, on the Chopawamsic Formation and the Ta River Metamorphic Suite. The Quantico Formation is assigned the same Late Ordovician age and similar stratigraphic position as the Arvonia Slate of the Arvonia syncline. The youngest rocks of the area are the granitoid and pegmatoid bodies of the Falmouth Intrusive Suite. They consist of several generations of chiefly dikes and sills that are intrusive into the Fredericksburg Complex and into the Quantico Formation. Granitoid rocks also form small plutons. The Falmouth is isotopically dated as Carboniferous in age. Some of the metavolcanic rocks of the Evington Group and part of the amphibolite gneiss and amphibolite of the Hatcher Complex, named by W. B. Brown in 1969, are probably coeval with the Chopawamsic Formation and hence equivalents of the Ta River Metamorphic Suite and the Holly Corner Gneiss. The biotitic gneiss and granitoid rocks east of the Spotsylvania lineament in the Dillwyn area are considered to be coeval with the Po River Metamorphic Suite.

Virginia↗
USGS1983

Stratigraphy of the Silurian outcrop belt on the east side of the Cincinnati Arch in Kentucky, with revisions in the nomenclature

Silurian rocks form a narrow arcuate outcrop belt about 100 mi long on the east side of the Cincinnati Arch in Kentucky. They range from as much as 300 ft thick in the north to a pinchout edge in the south. The nomenclature of this sequence is revised to reflect mappability and lithologic uniformity on the basis of detailed mapping at a scale of 1:24,000 by the U.S. Geological Survey in cooperation with the Kentucky Geological Survey. The Silurian rocks are divided into two parts: the Crab Orchard Group, raised in rank from Crab Orchard Formation and redefined, in the lower part of the Silurian section, and Bisher Dolomite in the upper part of the section. The Crab Orchard Group is subdivided into the Drowning Creek Formation (new name) at the base of the Silurian, overlain by the Alger Shale (adopted herein) south of Fleming County and by the Estill Shale (elevated to formational rank) north of Bath County. The Brassfield Member (reduced in rank from Brassfield Dolomite or Formation) and the Plum Creek Shale and Oldham Members of the former Crab Orchard Formation are included as members of the Drowning Creek; the Lulbegrud Shale, Waco, and Estill Shale Members of the former Crab Orchard Formation are now included in the Alger. The Drowning Creek Formation, 20 to 50 ft thick, is composed mainly of gray fine to coarse-grained dolomite with shale interbeds. The dolomite beds average several inches thick, with bedding surfaces that are locally smooth but generally irregular and are fossiliferous in many places; fossils include brachiopods, crinoid columnals, horn corals, colonial corals, trilobites, pelecypods, and bryozoans. The shale interbeds average several inches thick, except for its Plum Creek Shale Member which is entirely shale and as much as 12 ft thick, and are most abundant in the upper half of the formation. The members of the Drowning Creek intergrade and are indistinguishable in the northern part of the area. The Alger Shale, as much as 170 feet thick, is predominantly grayish-green clay shale with a thin (0.5-3 ft) dolomite member (the Waco, or its northern equivalent, the Dayton Dolomite Member, reduced in rank from Dayton Limestone) near the base. North of Bath County, the Lulbegrud Shale and Dayton Dolomite Members are reassigned to the underlying Drowning Creek Formation, the Estill Shale Member is elevated to formational status, and the Alger is dropped. The Bisher Dolomite, which overlies the Estill Shale in the northernmost part of the Silurian belt, ranges from 0 to 300 ft in thickness and is composed of medium-to coarse-grained, gray, fossiliferous dolomite. The Silurian section overlies Upper Ordovician rocks in apparent conformity, although faunal studies suggest a minor hiatus, and is overlain by Middle to Upper Devonian rocks in a regional angular unconformity that truncates the entire Silurian section at the southwest end of the outcrop belt, where it is nearest the axis of the Cincinnati Arch. All of the units recognized in the Silurian appear to thicken eastward, away from the axis of the arch and towards the Appalachian basin. This, with the presence of isolated remnants of the Brassfield near the axis, suggest that formation of the arch was initiated in Early Silurian time by subsidence of its eastern flank.

Professional Paper↗
USGS1980

Makah Formation — A deep-marginal-basin sequence of late Eocene and Oligocene age in the northwestern Olympic Peninsula, Washington

The Makah Formation of the Twin River Group crops out in a northwest-trending linear belt in the northwesternmost part of the Olympic Peninsula, Wash. This marine sequence consists of 2800 meters of predominantly thin-bedded siltstone and sandstone that encloses six distinctive newly named members--four thick-bedded amalgamated turbidite sandstone members, an olistostromal shallow-water marine sandstone and conglomerate member, and a thin-bedded water-laid tuff member. A local unconformity of submarine origin occurs within the lower part of the Makah Formation except in the central part of the study area, where it forms the contact between the older Hoko River Formation and the Makah. Foraminiferal faunas indicate that the Makah Formation ranges in age from late Eocene (late Narizian) to late Oligocene (Zemorrian) and was deposited in a predominantly lower to middle bathyal environment. The Makah Formation is part of a deep-marginalbasin facies that crops out in the western part of the Olympic Peninsula, in southwesternmost Washington and coastal embayments in northwestern Oregon, and along the central part of the coast of western Vancouver Island. On the basis of limited subsurface data from exploratory wells, correlative deep-marginal-basin deposits underlie the inner continental shelf of Oregon and the continental shelf (Tofino basin) along the southwestern side of Vancouver Island. Directional structures in the Makah Formation indicate that the predominantly lithic arkosic sandstone that forms the turbidite packets was derived from the northwest. A possible source of the clastic material is the dioritic, granitic, and volcanic terranes in the vicinity of the Hesquiat Peninsula and Barkley Sound on the west coast of Vancouver Island. Vertical and lateral variations of turbidite facies suggest that the four packets of sandstone were formed as depositional lobes on an outer submarine fan. The thin-bedded strata between the turbidite packets have characteristics of basin-plain and outer-fan fringe deposits.

Washington↗
USGS1996

The geology and mechanics of formation of the Fort Rock Dome, Yavapai County, Arizona

The Fort Rock Dome, a craterlike structure in northern Arizona, is the erosional product of a circular domal uplift associated with a Precambrian shear zone exposed within the crater and with Tertiary volcanism. A section of Precambrian to Quaternary rocks is described, and two Tertiary units, the Crater Pasture Formation and the Fort Rock Creek Rhyodacite, are named. A mathematical model of the doming process is developed that is consistent with the history of the Fort Rock Dome.

Professional Paper↗
USGS1923

The fauna of the so-called Dakota formation of northern central Colorado and its equivalent in southeastern Wyoming

This paper describes a small fauna from beds in northern central Colorado that have long been designated the Dakota formation, often with doubt that all the beds so named were really equivalent to the typical Dakota sandstone of eastern Nebraska. The upper part of the equivalent beds in southeastern Wyoming was referred by some writers to the Benton Shale and the lower part of the Cloverly formation. This so-called Dakota formation of northern central Colorado and its equivalent in southeastern Wyoming consist of cherty conglomerate, brown quartzose sandstone, and dark shale. The conglomerate is usually at the base of the series and at many localities is overlain by a single shale unit and that in turn by a sandstone. At other localities, however, there are several alternations of sandstone and shale above the basal conglomeratic layer. The fossil described in this paper, except one specimen, were obtained from the shales of the middle part of the formation. The single specimen, an ammonite, came from the uppermost sandstone.

Colorado;Wyoming↗
USGS1925

The evolution and disintegration of matter

In any attempt to study the evolution of matter it is necessary to begin with its simplest known forms, the so-called chemical elements. During a great part of the nineteenth century many philosophical chemists held a vague belief that these elements were not distinct entities but manifestations of one primal substance-the protyle, as it is sometimes called. Other chemists, more conservative, looked askance at all such speculations and held fast to what they regarded as established facts. To them an element was something distinct from other kinds of matter, a substance which could neither be decomposed nor transmuted into anything else. This belief, however, was based entirely upon negative evidence-the inadequacy of our existing resources to produce such sweeping changes. Many important facts were ignored, and especially the fact that the elements are connected by very intimate relations, such as are best shown in the periodic law of Mendeleef, who, from gaps in his table of atomic weights, predicted the existence of three unknown metals, which have since been discovered. For these metals, scandium, gallium, and germanium, he foretold not only their atomic weights but also their most characteristic physical properties and the sort of compounds that each one would form. His prophecies have been verified in every essential particular. One obvious conclusion was soon drawn from Mendeleef's "law," although he was too cautious to admit it, namely, that the chemical elements must have had some community of origin. The philosophical speculations as to their nature were fully justified.

Professional Paper↗
USGS1985

Stratigraphy and characteristic mollusks of the Pamunkey Group (Lower Tertiary) and the Old Church Formation of the Chesapeake Group— Virginia coastal plain

Along the Pamunkey River and its tributaries can be found a very complete, well-preserved, Tertiary stratigraphic record that reflects the sea-level changes as well as the local tectonic history of the central Virginia Coastal Plain. Using this record, I have described the lower Tertiary units and proposed a sequential model for their occurrence. Sediments examined in this study range in age from early Paleocene to latest Oligocene or earliest Miocene. Upper Tertiary units are described where they occur in the same sections with the lower Tertiary beds. The Brightseat Formation (lower Paleocene), Aquia Formation (upper Paleocene), Marlboro Clay (upper Paleocene), Nanjemoy Formation (lower Eocene), Piney Point Formation (middle Eocene) and Old Church Formation (new unit, upper Oligocene and lower Miocene) were studied. The definitions of the Piscataway and Paspotansa Members of the Aquia are amended, and a lectostratotype (principal reference section) is designated for those units as well as the Aquia on the Potomac River just below the mouth of Aquia Creek. A lectostratotype section is also designated for the Nanjemoy and its two members, the Potapaco and the Woodstock. That section is on the Potomac above Popes Creek. Beds assigned to the Piney Point and Old Church Formations, previously known only in the subsurface, crop out extensively on the Pamunkey River. A hypostratotype (reference section) is selected for the Piney Point Formation on the Pamunkey River at Horseshoe. The Old Church Formation (named herein) is included in the Chesapeake Group. Areal extent of the stratigraphic units was determined by correlation of outcropping beds on the Pamunkey, Patuxent, Potomac, Rappahannock, Mattaponi, Chickahominy, and James Rivers supplemented by well data. Comparisons of the onlap histories of the Salisbury, Albemarle, and Charleston Embayments indicate a number of simultaneous transgressive events implying global sea-level rises. More restricted transgressions appear to be the result of local downwarping.

Virginia↗
USGS1988

Ground-water hydraulics, regional flow, and ground-water development of the Floridan aquifer system in Florida and in parts of Georgia, South Carolina, and Alabama

The Floridan aquifer system is one of the major sources of groundwater supplies in the United States. This productive aquifer system underlies all of Florida, southeast Georgia, and small parts of adjoining Alabama and South Carolina, for a total area of about 100,000 square miles. About 3 billion gallons of water per day were withdrawn from the aquifer system in 1980, and in many areas the Floridan is the sole source of freshwater. The Floridan aquifer system is a sequence of hydraulically connected carbonate rocks (principally limestone with some dolomite) ranging in age generally from late Paleocene to early Miocene. The rocks vary in thickness from a featheredge where they crop out to more than 3,500 feet where the aquifer is deeply buried. The aquifer system generally consists of an upper aquifer and a lower aquifer separated by a lesspermeable confining unit of highly variable properties. In parts of north Florida and southwest Georgia, where little permeability contrast exists among the units, the Floridan is effectively one continuous aquifer. The upper and lower aquifers, named the Upper Floridan aquifer and the Lower Floridan aquifer, are defined on the basis of permeability and their boundaries locally do not coincide with those for either time-stratigraphic or rock-stratigraphic units. Overlying much of the Floridan aquifer system are low-permeability clastic rocks. The lithology, thickness, and integrity of these rocks determine the degree of confinement and influence the distribution of natural recharge, discharge, and ground-water flow in the Floridan. The permeability of the Floridan aquifer system is derived from small openings including fossil hashes and solution-widened joints as well as large cavernous openings in karst areas. Diffuse flow predominates where the small openings occur, whereas conduit flow may occur where large cavernous openings are. Transmissivities are highest (greater than 1,000,000 feet squared per day) in the unconfined karst areas of central and northern Florida. Lowest transmissivities (less than 50,000 feet squared per day) occur in panhandle Florida and southernmost Florida where the Upper Floridan aquifer is confined by thick clay sections. The hydraulic properties of the Lower Floridan aquifer are not well known; however, intervals of high transmissivity occur that have been attributed to paleokarst development. Springs, nearly all of which occur in unconfined and semiconfined parts of the Upper Floridan aquifer in Florida are the dominant feature of the Floridan flow system. Before ground-water development, spring flow and point discharge to surface-water bodies were about 88 percent of the estimated 21,500 cubic feet per second total discharge, or about 19,000 cubic feet per second. Diffuse upward leakage, which occurs primarily in confined areas, accounted for the remaining 12 percent or about 2,500 cubic feet per second. Most of the recharge necessary to sustain springflow and aquifer discharge to streams and lakes occurs relatively close to springs and areas of point discharge to surface-water bodies. Recharge to the Upper Floridan is highest, averaging 10-20 inches per year, in unconfined or semiconfined spring areas. The proximity of high recharge to high discharge implies a vigorous and well-developed shallow flow system in the unconfined and semiconfined parts of the Upper Floridan aquifer. Ground-water flow is very sluggish in the parts of the aquifer system that are deeply buried and tightly confined, primarily southeast Georgia and northeast Florida, south Florida, and far-west panhandle Florida. Discharge to springs, streams, and lakes is practically nonexistent in the tightly confined areas and natural discharge occurs almost exclusively by diffuse upward leakage through thick overburden. The regional flow system has not been appreciably altered by groundwater development. However, increasing pumpage that reached 3 billion gallons per day by 1980 has resulted in long-term regional water level decline of more than 10 feet in three broad areas: coastal Georgia, adjacent South Carolina, and northeast Florida; west-central Florida; and panhandle Florida. Saltwater encroachment as a result of pumping has occurred locally in coastal areas. Pumpage from the Upper Floridan aquifer is supplied primarily by reduction of natural discharge and by increased recharge rather than by depletion of aquifer storage. About 20 percent is from reduced discharge to springs, streams, and lakes, about 20 percent is from reduced upward leakage, and about 60 percent is from increased recharge. Compared to predevelopment conditions, discharge to springs, streams, and lakes is reduced by less than 5 percent, upward leakage is reduced by about 30 percent, and recharge is increased by about 12 percent. Total recharge and, therefore, discharge increased from a predevelopment rate of 21,500 cubic feet per second to about 24,100 cubic feet per second by 1980. A considerable area remains of the Floridan aquifer system where large ground-water supplies may be developed. This area is largely inland from the coasts and characterized by high transmissivity and minimal development prior to the early 1980's. The major constraint on future development probably is degradation of water quality rather than water-quantity limitations.

Alabama, Florida, Georgia, South Carolina↗
USGS1992

Hydrogeology of the Cambrian-Ordovician aquifer system in the northern Midwest, United States with a section on ground-water quality

The Cambrian-Ordovician aquifer system contains the most extensive and continuous aquifers in the northern Midwest of the United States. It is the source of water for many municipalities, industries, and rural water users. Since the beginning of ground-water development from the aquifer system in the late 1800's, hydraulic heads have declined hundreds of feet in the heavily pumped Chicago-Milwaukee area and somewhat less in other metropolitan areas. The U.S. Geological Survey has completed a regional assessment of this aquifer system within a 161,000-square-mile area encompassing northern Illinois, northwestern Indiana, Iowa, southeastern Minnesota, northern Missouri, and Wisconsin. Consolidated sedimentary rocks in the northern Midwest range in age from Precambrian to Cretaceous and crop out in generally concentric, arcuate patterns, dipping away from structural highs (arches) on the Precambrian basement in northern Minnesota and Wisconsin toward structural lows (basins) to the south and east. The sedimentary bedrock is generally overlain by a veneer of glacial drift. Thickness of the sedimentary sequence increases to about 5,000 feet in the Forest City basin of southwestern Iowa and to about 14,000 and more than 15,000 feet in the Illinois and Michigan basins, respectively. Cambrian and Ordovician age rocks, mainly marine sandstone and carbonate rocks, compose much of the sedimentary sequence and form the Cambrian-Ordovician aquifer system. The aquifer system lies on the Precambrian basement, regarded as a regional confining unit. Six hydrogeologic units are defined; they are arranged as alternating pairs of an aquifer and an overlying confining. unit. The units are named using the predominant geologic nomenclature of the upper Mississippi Valley, which includes most of the study area. In the southern quarter of the area, the hydrogeologic units consist of equivalent formations of the Ozark area (mostly carbonate rocks). The uppermost part of the aquifer system is the Maquoketa confining unit, which consists of the Maquoketa Shale and the underlying dolomite and shale of the Galena Dolomite and the Decorah, Platteville, and Glenwood Formations. The underlying St. Peter-Prairie du Chien-Jordan aquifer is an important source of ground water in the western part of the area in Iowa and Minnesota, where the uniform Jordan Sandstone is hydraulically connected to overlying fractured dolomite of the Prairie du Chien Group. The unit is less important in the eastern part of Wisconsin and Illinois because the Jordan Sandstone is absent and the Prairie du Chien Group is thin or absent due to pre-St. Peter Sandstone erosion. Equivalent rocks in northern Missouri-the Roubidoux Formation and the Gasconade and Eminence Dolomites-are mainly carbonate rocks that are somewhat permeable and contain some sandstone. The St. Lawrence and Franconia Formations underlying the St. Peter-Prairie du Chien-Jordan aquifer consist generally of silty and shaly, fine-grained, poorly sorted, and dolomitic sandstones that restrict vertical movement of ground water and form a regional confining unit. In the southern and eastern parts of the area, the Potosi and Derby-Doerun Dolomites and the upper part of the Davis Formation are the equivalent rocks (mainly carbonate rocks). In the east-central part of the area in Illinois and Wisconsin, the Ironton-Galesville aquifer forms the most important aquifer of the Cambrian-Ordovician aquifer system, contributing about one-third of the yield from wells in the aquifer system in the Chicago area. The aquifer terminates to the west, south, and east, where the sandstones grade into less permeable carbonate rocks in central Iowa, central Illinois, and northwestern Indiana, respectively. The underlying Eau Claire Formation and its partial equivalent to the southwest, the Bonneterre Formation, form an important confining unit above the Mount Simon aquifer throughout much of the study area. Siltstone and shale are fairly common in the upper part of the Eau Claire Formation but less so in its northernmost extent in Wisconsin. Dolomite content increases southward and westward, where a middle dolomite facies grades laterally into the Bonneterre in Missouri, southwestern Minnesota, extreme south-central Wisconsin, and possibly in western Iowa. The basal unit in the Cambrian-Ordovician aquifer system, the Mount Simon aquifer, is present throughout the study area, except where it is absent over local highs of the Precambrian basement. It consists primarily of the Mount Simon Sandstone in the north and its equivalent in northern Missouri, the Lamotte Sandstone. The underlying Hinckley Sandstone of Precambrian age is included in Minnesota, as is the overlying Elmhurst Sandstone Member of the Eau Claire Formation in northern Illinois. The aquifer increases greatly in thickness and the water is progressively more saline away from the northern structural highs toward the basins. Much of the movement and discharge of ground water in the northern Midwest occurs in local, unconfined, shallow flow systems within a few miles of points of recharge. The rest of the water is semiconfined or confined in intermediate or regional flow systems within the bedrock, where flow is deeper, slower, and traverses much longer distances from recharge areas to discharge areas. The major areas of recharge to regional confined flow are in northwestern Iowa, southeastern Minnesota, western, southern, and eastern Wisconsin, and northern Illinois. Although the rate of flow is small, significant recharge to the Cambrian-Ordovician aquifer system also occurs as leakage through the Maquoketa confining unit, where the vertical hydraulic gradient is downward. Ground water in much of the confined aquifer system moves laterally from recharge areas toward the major river valleys and Lake Michigan or down dip toward the structural basins. The longest flow paths extend as much as 400 miles from northwestern Iowa southeast toward the Illinois basin or to the Mississippi River and Missouri River valleys near their confluence. Other major confined flow is from eastern Wisconsin toward the Michigan basin and southward flow from northeastern Illinois toward the Illinois basin. Regional ground-water discharge from the aquifer system is mainly diffuse upward leakage from confined aquifers along flow paths toward the structural basins. Very saline water around and brines within the basins restrict regional flow into the basins, forcing ground water to discharge upward. Water in intermediate flow systems discharges upward to the major river valleys. Original heads of more than 100 feet above land surface were recorded in the aquifer system near Lake Michigan in eastern Wisconsin and at Dubuque, Iowa, along the Mississippi River. The Cambrian-Ordovician aquifer system was developed rapidly in the late 1800's after the first deep well was drilled in Chicago in 1864. Many flowing wells were not controlled, which caused water levels in deep wells to decline, and many no longer flowed by the early 1900's. Heads in the aquifers have declined very little in most of the recharge or unconfined areas since ground-water withdrawal began, but major declines have occurred in confined areas. The largest declines in head are at Chicago, Illinois, Milwaukee and Green Bay, Wisconsin, and Mason City, Iowa, where the aquifer system is confined by the Maquoketa confining unit. The composite head in the aquifer system declined more than 900 feet in the deepest cones of depression in the Chicago area from 1864 to 1980 and about 375 feet in the cone at Milwaukee from 1880 to 1980. More than 200 feet of decline has occurred at Mason City. The head declined as much as 440 feet in Green Bay from 1886 to 1957, when the city discontinued use of its deep wells and began using water from Lake Michigan. The largest centers of pumping are in the Chicago and Twin Cities (Minneapolis-St. Paul, Minnesota) metropolitan areas about 180 million gallons per day each in 1980. Pumpage exceeded 10 million gallons per day in only a few other areas in 1980. Ground water in the Cambrian-Ordovician aquifer system in the northern Midwest is characterized by an extreme range of mineralization, but its quality in most of the area is good. The major cations are calcium, magnesium, and sodium, and the major anions are bicarbonate, sulfate, and chloride. Sodium, sulfate, and chloride distributions are closely related to the distribution pattern of dissolved solids but not in the same proportion. Dissolved-solids concentration is generally less than 1,000 milligrams per liter in the recharge areas of Wisconsin, southern Minnesota, northeastern Iowa, and north-central Illinois where the aquifer system crops out or subcrops beneath glacial drift. Ground water there is the Ca-Mg-HC03 type, derived from and identical to that in the overlying glacial drift. In northwestern Iowa and southwestern Minnesota, the water in both the glacial drift and the Cambrian-Ordovician aquifer system is a Ca-Na-S04HC03 type, derived from oxidation of pyrite in the overlying Cretaceous Dakota Formation. Transition to higher dissolved solids in the confined areas commonly is accompanied by increased sulfate concentration and· the occurrence of Ca-Na-S04-type water. Salinity of the ground water increases progressively toward the .basins, where dissolved solids exceed 200,000 milligrams per liter. Saline water is present in the Mount Simon aquifer near Lake Michigan in eastern Wisconsin and northeastern Illinois but occurs in successively younger rocks to the east and south as they dip toward the basins. Similarly, salinity increases down dip in Iowa to the southwest and south; however, regional ground-water flow in Iowa is from northwest to southeast. Much of the ground water in the confined aquifer system is isotopically depleted in 0180 and OD with respect to modern precipitation-an indication that the water originated as precipitation in a much colder climate than the present and probably was derived from recharge of glacial meltwater. On the basis of o34S values for sulfur in sulfate, it is believed that isostatic loading from glacial ice over the Michigan basin reversed the hydraulic gradient to trend westward, opposite from the present gradient, causing saline water in the Michigan basin to discharge westward through the present recharge areas. Natural water-quality problems in the Cambrian-Ordovician aquifer system are mainly the high dissolved-solids concentrations and associated high concentrations of sulfate and chloride, which limit the use of the water for municipal and domestic purposes in much of the confined aquifer system in central and southern Illinois, Indiana, southern and western Iowa, and northern Missouri. Another concern is that radium activity exceeds normal background concentrations of a few picocuries per liter in much of the confined aquifer system in eastern Wisconsin, northeastern Illinois, and central Iowa. Other common problems are high hardness and locally excessive concentrations of iron and hydrogen sulfide.

Iowa, Illinois, Indiana, Michigan, Minnesota, Miss↗
USGS1996

Hydrogeologic terranes and potential yield of water to wells in the Valley and Ridge Physiographic Province in the eastern and southeastern United States

The Valley and Ridge Physiographic Province is underlain by deformed sedimentary rock of Paleozoic age including dolomite, limestone, shale, and sandstone. Regolith (soil, sediment, and weathered rock) covers the Paleozoic rock throughout most of the province. Local differences in lithology, structure, and weathering can result in four orders of magnitude variation in the water-yielding properties of the geologic units that underlie the area. Selected rock types, however, can account for a substantial part of this variation because of the unique way in which these dense, consolidated sedimentary rock types deform and weather to produce secondary openings. On the basis of relations among rock type, water-yielding openings, and water-yielding properties (as indicated by specific capacity), the regolith and consolidated rock were classified and mapped as five hydrogeologic terranes alluvium, dolomite, limestone, argillaceous carbonate rock, and siliciclastic rock. The hydrogeologic terranes are named after the predominant outcrop lithology within them. The western toe of the Blue Ridge Mountains is classified as a subdivision of the dolomite hydrogeologic terrane that may produce yields of water in excess of 1,000 gallons per minute (gal/min) to public and industrial supply wells. Specific-capacity data for homogeneous data sets, which consist of all wells that have the same characteristics in regard to casing diameter, primary use of the water, and topographic setting, revealed significant differences in water-yielding properties among the five hydrogeologic terranes. According to results of Tukey statistical tests at a probability (alpha level) of 0.05, 8 out of 10 pairs of hydrogeologic terranes (for example, alluvium/limestone) had significantly different median specific-capacity values. The median value for public and industrial supply wells in the western toe is three times greater than the value for comparable wells in the dolomite hydrogeologic terrane elsewhere. Estimates of potential yields to public and industrial supply wells were calculated from specific-capacity data for most-productive wells, which have casing diameter of 7 in. or more, discharge water primarily for public or industrial supply, and are in a valley. Median constant drawdowns, calculated from reported drawdowns, were assumed to be between 10 and 90 ft for wells completed in each of the five hydrogeologic terranes, and well-entrance losses were assumed to be negligible. Estimated interquartile ranges in potential yields to 412 mostproductive wells in the five hydrogeologic terranes were 170 to 580 gal/min, alluvium; 210 to 1,400 gal/min, dolomite; 80 to 720 gal/min, limestone; 65 to 850 gal/min, argillaceous carbonate rock; and 70 to 280 gal/min, siliciclastic rock.

Alabama, Georgia, Maryland, New Jersey, Pennsylvan↗