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At least 793 records · Page 44Linked to original sources
USGS1985

Tectonic implications of the Indian Run Formation— A newly recognized sedimentary mélange in the northern Virginia Piedmont

Sedimentary melange in the northeastern part of Fairfax County, Virginia, contains both mesoscopic and mappable fragments of Accotink Schist, Lake Barcroft Metasandstone, metagabbro, and ultramafic rocks as well as smaller fragments of other rock types. This melange was originally mapped as the Sykesville Formation, a major precursory sedimentary melange in northern Virginia and Maryland. The fragments of Accotink Schist and Lake Barcroft Metasandstone within the Sykesville were considered to be rip-ups of these units over which the Sykesville slid when finally emplaced. More recent study has shown that fragments of Accotink and Lake Barcroft are restricted to a certain area of sedimentary melange originally defined as Sykesville, and this part of the melange is now considered to be a separate mappable unit, here named the Indian Run Formation. The Indian Run underlies the sequence Accotink Schist and Lake Barcroft Metasandstone which is here formally named the Annandale Group. The Indian Run is intruded by the Occoquan Granite of Cambrian age, so it is of Cambrian or Late Proterozoic age. The Sykesville Formation (restricted) is a much more extensive unit than the Indian Run Formation and is characterized by its contained olistoliths of the Peters Creek Schist, the unit that tectonically overlies it. The Sykesville and Peters Creek constitute a precursory melange-allochthon pair which is here termed a 'tectonic motif.' The Indian Run-Annandale pair then forms a tectonically lower motif, and the overlying pair, the Yorkshire Formation-Piney Branch Complex, forms a tectonically higher motif. The Chopawamsic Formation and underlying sedimentary melange in the area south of Fairfax County may form a tectonic motif beneath the Indian Run-Annandale tectonic motif. Thus, three and perhaps four repetitions of precursory melange-allochthon pairs occur in northern Virginia. Other percursory melanges and motifs may occur in the Maryland Piedmont to the north. The tectonic setting of the motif formation and assemblage is uncertain at this time. A model involving the obduction of several separate sheets onto the ancestral North American continental margin is appealing in that it involves the closing and destruction of a marginal basin, a relatively simple concept. This model fails, however, to supply a source for the sediment necessary to form the precursory melanges. A trench-slope origin would supply the vast amount of needed sediment by accretion. The precursory melangeallochthon motifs would then be stacked near the base of the trench slope. This model is appealing and requires a rather complicated assemblage of continental, arc, and oceanic fragments, such as those that occur on many modern continental margins.

Virginia↗
USGS1986

Ground-water hydrology and subsurface migration of radionuclides at a commercial radioactive-waste burial site, West Valley, Cattaraugus County, New York

Low-level radioactive wastes were buried from 1963-75 in trenches excavated in a clay-rich till about 28 meters thick. Beneath the till is a lacustrine sequence that is unsaturated in its upper part and acts as a drain to the till. The till is nearly isotropic; hydraulic conductivity ranges between 2 times 10 to the minus 8th power and 6 times 10 to the minus 8th power centimeters/sec. Fractures with oxidized walls extend as much as 5 meters below the original land surface. The fractured till is 5 to 10 times more permeable than the deeper unfractured till, as determined from computer simulations. The direction of groundwater flow in the till is predominantly downward, with an average linear pore velocity of 1 to 8 centimeters/year. Tritium migrated less than 3 meters from three trenches in the 7 to 11 years after they were completed. Carbon-14 migrated less than 1 meter, and migration of other radionuclides is apparently even less. The migration of tritium and carbon-14 occurs chiefly by diffusion. Radionuclides are far less likely to reach the surface environment by subsurface flow through the till than by seepage of trench water through the trench covers, which can occur whenever trenches become filled with water from recharge entering through cracks that form in the cover. (USGS)

Professional Paper↗
USGS1925

Notes on the geology of Green River Valley between Green River, Wyoming, and Green River, Utah

During July, August, and part of September, 1922, I had the privilege of accompanying a party sent out jointly by the Utah Power & Light Co. and the United States Geological Survey to gather such data as were still needed to complete a study of the power resources of Green River between Green River, Wyo., and Green River, Utah. The chief deficiency to be supplied was a continuous topographic map of the valley in sufficient detail to permit calculation of the storage capacity of any reservoir site that might be used, the stream gradient, and similar features. Maps on a satisfactory scale of a number of isolated stretches of the river had already been made by public or private agencies, and it was necessary to verify them and connect them on a uniform datum. Inasmuch as it was deemed unlikely that a dam higher than 300 feet would be constructed anywhere on the part of the river to be examined, a plane 300 feet above the water surface was made the upper limit of mapping. Over such parts of the valley as had been mapped already the progress of the party was naturally very rapid, and even where no mapping had previously been done, the 300-foot limit set upon the work and the usual narrowness of the valley combined to reduce the extent of the area to be mapped, so that the speed maintained was relatively high. Under this condition of rapid movement it was seldom possible to make more than the most cursory examination of the rocks, though occasionally circumstances permitted more or less detailed observation. The notes here recorded are therefore mostly of a rather generalized character, but as they pertain in part to localities that are difficult of access and not often visited by geologists, and that are at the same time classic in the history of American geology, I venture to to record them for whatever value they may have to other geologists.

Utah;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↗
USGS1925

An early Eocene florule from central Texas

In 1916 I described a florule collected by Alexander Deussen and L. W. Stephenson at the town of Earle, in Bexar County, Tex. This florule was tentatively considered of Midway age by these geologists, and examination of the fossil plants tended to confirm this assignment, particularly because of their lack of harmony with the extensive Wilcox flora described in the volume cited above and because of their resemblance to the described floras from the Raton and Denver formations of Colorado and New Mexico.

Texas↗
USGS1925

The resuscitation of the term Bryn Mawr gravel

In the course of geologic and physiographic work in eastern Pennsylvania, it has seemed to the writer that the time was ripe for the restriction of the term Brandywine formation, now including presumably both Pliocene and Pleistocene gravels, and the reinstatement of the old term Bryn Mawr gravel for a portion of the divided Brandywine. A brief history of the nomenclature and usage involved will show the grounds for the choice of terms.

Pennsylvania↗
USGS1925

Origin of the boghead coals

The bituminous rocks of sedimentary origin may be classified roughly under two main heads - coals and bituminous shales. In a strict sense no definite line can be drawn between these two groups, because coals may be insensibly grade into bituminous shales. Chemically the boghead coals are preeminently bituminous.

Professional Paper↗
USGS1925

Aniakchak Crater, Alaska Peninsula

The discovery of a gigantic crater northwest of Aniakchak Bay (see fig. 11) closes what had been thought to be a wide gap in the extensive series of volcanoes occurring at irregular intervals for nearly 600 miles along the axial line of the Alaska Peninsula and the Aleutian Islands. In this belt there are more active and recently active volcanoes than in all the rest of North America. Exclusive of those on the west side of Cook Inlet, which, however, belong to the same group, this belt contains at least 42 active or well-preserved volcanoes and about half as many mountains suspected or reported to be volcanoes. The locations of some of these mountains and the hot springs on the Alaska Peninsula and the Aleutian Islands are shown on a map prepared by G. A. Waring. Attention has been called to these volcanoes for nearly two centuries, but a record of their activity since the discovery of Alaska is far from being complete, and an adequate description of them as a group has never been written. Owing to their recent activity or unusual scenic beauty, some of the best known of the group are Mounts Katmai, Bogoslof, and Shishaldin, but there are many other beautiful and interesting cones and craters.

Professional Paper↗
USGS1988

A seismic-stratigraphic investigation of the Madison and associated aquifers; application to ground-water exploration, Powder River basin, Montana-Wyoming

This seismic-stratigraphic investigation is part of a larger 5-year project the "Madison Project" undertaken by the Water Resources Division of the U.S. Geological Survey to study the hydrology of the Madison and associated aquifers. The objectives and methods of investigation of the Madison Project are described by the U.S. Geological Survey (1975).

Montana, Wyoming↗
USGS1985

Validity of Darcy's law under transient conditions

Darcy 's Law, which describes fluid flow through porous materials, was developed for steady flow conditions. The validity of applying this law to transient flows has been mathematically verified for most ground-water flow conditions. The verification was accomplished through application of Hankel transforms to linearized Navier-Stokes equations which described flow in a small diameter cylindrical tube. The tube was chosen to represent a single pore in a porous medium. (USGS)

Professional Paper↗
USGS1987

Floods in central Texas, August 1-4, 1978

Catastrophic floods caused by record rainfall occurred in central Texas during August 1-4, 1978. Torrential rain initiated by the remnants of tropical storm Amelia fell over south-central Texas during August 1-3, and very intense rain due to the interaction between the cold front and maritime air mass fell over north-central Texas on August 3-4. Rainfall of more than 48 inches near Medina in south-central Texas established a new United States record of extreme point rainfall for a 72-hour period. Major flooding occurred on the Medina and Guadalupe Rivers. Severe to minor flooding occurred on the Brazos, Llano, Pedernales, and Nueces Rivers. Floods with recurrence intervals in excess of 100 years and recordsetting peak discharges were observed at several streamflow stations. Thirty three lives were lost and total damages reportedly exceeded $110 million.

Texas↗
USGS1985

An approach for appraising the accuracy of suspended-sediment data

Procedures are presented for appraising the accuracy of suspended-sediment data. Types of errors involved are sampling error, spatial error, temporal error, and sediment-discharge error. The standard error of estimate is used to represent errors. Suspended-sediment data for 17 U.S. Geological Survey gaging stations in Arizona, California, Nebraska, New Mexico, Pennsylvania, and Washington are used in applications of the procedures. For the study sites, the magnitudes of the different types of error apparently vary directly with percentage of sediment-water mixture that is sand; when the percentage sand is relatively high, magnitudes of the different types of error have a relatively wide range. For seven sites of the Sacramento River , Calif., and its tributaries, the standard sampling error apparently can range from 2.5 percent when percentage sand is relatively low to 20 percent when percentage sand is relatively high. For 16 sites in Arizona, California, Nebraska, New Mexico, and Pennsylvania, the coefficient of variation for concentrations of suspended sediment across streams apparently can range from 2.5 percent (low percentage sand) to 70 percent (high percentage sand). (USGS)

Professional Paper↗