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At least 955 records · Page 53Linked to original sources
USGS1975

Norman Creek, a source of recharge to Maramec Spring, Phelps County, Missouri

Rhodamine WT dye was used to trace the subsurface movement of water from Norman Creek, a losing Ozark stream, to Maramec Spring, a straight-line distance of 8.7 mi (14.0 km). Grab samples and activated charcoal packets were used to check possible emergent points of the dye. The leading edge of the dye reached Maramec Spring 68-75 days after the dye injection, and the peak concentration reached the spring 82-93 d after injection. Small quantities of dye were still being recovered at the spring 114 d after injection and 39-46 d after the dye first arrived at the spring. Computed average velocities, assuming straight-line travel, are 0.47-0.42 ft(0.14-0.13 m)/min for the leading edge and 0.39- 0.34 ft(0.12-0.10 m)/min for the peak. This apparent rate of travel compares favorably with other recent subsurface tracing studies in southern Missouri which generally range from 0.4 to 25 ft(0.12 to 7.6 m)/min.

Missouri↗
USGS1976

Marine diatom and silicoflagellate biostratigraphy of the type Delmontian Stage and the type Bolivina obliqua Zone, California

Investigation of the marine diatom and silicoflagellate biostratigraphy of the type Delmontian Stage and and type Bolivina obliqua Zone in California shows that the type Delmontian Stage is equivalent to part of the supposedly older Mohnian Stage and is early late Miocene. The type Bolivina obliqua Zone, which conformably overlies the type Mohnian Stage, appears to be early Pliocene.

California↗
USGS1975

Combining estimates of low-flow characteristics of streams in Massachusetts and Rhode Island

The number of base-flow measurements needed to meet specified accuracy goals for estimating low-flow characteristics at ungaged sites can be reduced by combining an estimate based on a regression of base-flow measurements on discharges from a nearby continuous long-term gaging station with an estimate based on a regional relationship developed from regressing the low-flow characteristics on basin characteristics. The estimates should be combined by weighting each inversely with its variance from the true value. Empirically estimated values of variance of the estimated 7- day, 10-year low flow from its true value indicate that more than six or eight base-flow measurements add" little to the confidence with which such an estimate is made.

Massachusetts, Rhode Island↗
USGS1975

Adjustment of logarithmic flood-frequency statistics for gaged California streams to minimize the time sampling error

Methods for adjusting logarithmic flood-frequency statistics for gaged streams to minimize the time sampling error that is inherent in short records are discussed. Statistical procedures for adjusting the mean and standard deviation of a short-term array of annual peak discharges are already well established; two standard sets of equations for utilizing the additional information contained in longer records of peak discharge observed at nearby gaging stations are given. A standard method for adjusting the coefficient of skew does not exist, and consequently a special technique for estimating the long-term value of that statistic was developed for this study. Regional equations were developed that relate the logarithmic skew coefficient to logarithmic transformations of mean annual basinwide precipitation and mean annual peak discharge per square mile. The technique appears to be satisfactory for use in the greater part of California, where over large areas the peak discharge in any year is usually associated with a single widespread general storm or with a series of such storms where snowmelt runoff is involved rather than with localized precipitation events.

Journal of Research of the U.S. Geological Survey↗
USGS1975

Generation of potassium-poor magmas in the northern Sierra Nevada and the Svecofennian of Finland

Comparison of the evolution of magmas in the Precambrian of southwestern Finland with that in the Paleozoic and Mesozoic of the northern Sierra Nevada brings out features that may clarify the origin of potassium-poor silicic magmas. In the northern Sierra Nevada, Paleozoic sodarhyolitic effusive rocks and associated trondhjemite represent silicic differentiates of andesitic magmas formed near a Benioff zone. These potassium-poor magmas were formed early, before thickening of the crust, and were followed by basaltic and rhyolitic magmas with normal potassium content. In southwestern Finland, where 70 percent of the area is covered by silicic and intermediate plutonic rocks, the early synkinematic intrusive masses are trondhjemitic and the later ones are granitic with eutectic ratios of quartz, plagioclase, and potassium feldspar. The latest granites are exceptionally rich in potassium feldspar. The oldest rocks, cordierite-garnet-sillimanite gneisses and interbedded metavolcanic rocks, are folded on gently plunging axes that steepen diapirically around large late-kinematic plutonic masses. Trondhjemite occurs as thin sheetlike masses parallel to the folded bedding and could not have traveled far without losing its initial heat. Therefore it seems that the trondhjemitic magma was formed at shallow depths. By analogy with the shallow depth of early magma generation in the northern Sierra Nevada, it is suggested that the trondhjemitic magmas in Finland formed at mantle depths near a Benioff zone or at the base of the early thin crust at pressures where phlogopite or biotite was stable. Later, after thickening of the crust above, potassium from the biotite was released, making the late kinematic magmas rich in potassium. A plate-tectonic model of an island-arc environment explains the coeval age of the Svecofennian and "Karelian" foldbelts and the increase of potassium with decreasing age in the extrusive and intrusive magmas.

northern Sierra Nevada, Svecofennian block↗
USGS1976

Sediment-filled pots in upland gravels of Maryland and Virginia

Pot-shaped depressions filled with sandy clayey silt are found in "Upland" gravels (previously termed Brandywine) of probable Miocene age, in northeastern Maryland and in Virginia near Washington, D.C. The pots are about 7 ft (2m) deep and commonly are about as wide. In plan, many are strongly elliptical. Sides are steep or even bulbous, and the filling in some pots shows faint stratification paralleling the sides. Strata in the enclosing gravel commonly bend downward and are thinner beside and below the pots. The gravel deposits are remnants of alluvial deposits of the ancestral Susquehanna and Potomac Rivers. All the pots are at the present gravel surface. We suggest that the pots originated when seasonal frost in an overlying layer of sandy clayey silt provided a confining upper layer. The freezing plane in the silt moved downward, reaching the gravel at some points before others. Water in the gravel moved toward the freezing plane by capillarity or by cryostatic head, forming ice lenses in the silt. Each winter, ice growth forced unfrozen clayey silt a short distance downward and outward into the gravel, increasing the irregularity of the silt-gravel contact and promoting more rapid movement. The pots probably reflect some centuries of growth, probably during the Illinoian Glaciation.

Maryland, Virginia↗
USGS1976

Ocher as a prospecting medium in the Montezuma district of central Colorado

Ocher occurs widely In the Montezuma district as small sinters and as bedded deposits of bog iron and ocher-cemented conglomerates. The iron of the ochers is derived from pyrite-rich veins and from pyritic hydrothermally altered rocks. Trace amounts of ore metals in the ocher and its admixed detritus are partly from the pyritic source rocks but also include contributions from other rocks and ores in the watershed, both during and after formation of the ocher deposit. Ocher is evidence for the presence and character of the generally ill exposed pyritic rocks, which are important, in evaluating the porphyry-metal system of ore deposits. The trace-element composition of the ocher is at best a qualitative guide to the ore metals present in the provenance of the ocher deposit but not to their abundance or necessarily to their mode of occurrence.

Colorado↗
USGS1975

Progressive metamorphism of schists recovered from a deep drill hole near Fairbanks, Alaska

In 1965, a deep test hole drilled near Eielson Air Force Base, Fairbanks district, Alaska, penetrated 9,774 ft (2,979.1 m) into schists of the metamorphic complex of the Yukon-Tanana Upland. Cores recovered from the test hole show that the section is dominated by calc-magnesian rocks with subordinate pelitic schists. Pelitic mineral assemblages define a progressive increase in metamorphic grade with depth, from the garnet to the kyanite isograd. Diopside first appears in the calc-magnesian schists that were cored at a depth of 9,766 ft (2,976.5 m), indicating the onset of the reaction: Tremolite + 3 calcite -f- 2 quartz→5 diopside + 3CO 2 +H 2 O. Ubiquitous staurolite and rare andalusite occur in the kyanite-bearing pelitic schists. Andalusite appears to have crystallized under postkinematic conditions, and the staurolite is apparently of both synkinematic and postkinematic origin. Hornblende and biotite from calc-magnesian schists sampled at depths of 7,142½ ft (2,176.9 m) and 9,766 ft (2,976.5 m) gave 40 K/ 40 Ar ages of 140±8 and 57.3±1.9 m.y., respectively. The hornblende age is believed to represent the age of the latest synkinematic metamorphism, and the biotite age appears to be an anomalously young one related to the outgassing of argon from biotite at greater depth in the section. Recent experimental data on andalusite-kyanite-sillimanite and staurolite equilibria and the stability field of calcite+quartz+tremolite versus diopside in calc-magnesian rocks suggest that the rocks recovered from the 8,218- to 9,770-ft (2,504.7- to 2,977.7-m) interval were synkinematieally recrystallized at crustal depths of 17 to 19 km and at temperatures of 515° to 580°C; the present thermal gradient (31.5°C/km) is similar to that which accompanied metamorphism in Jurassic time.

Alaska↗
USGS1976

A reconnaissance study of the uranium and thorium contents of plutonic rocks of the southeastern Seward Peninsula, Alaska

Large granitic Cretaceous plutons are exposed along and adjacent to an arcuate belt of igneous and high-grade raetamorphic rocks in the southeastern Seward Peninsula of Alaska. Reconnaissance studies of these plutons have shown that the Darby pluton has well above average amounts of uranium and thorium (11.2 ppm and 58.7 ppm, respectively), the Kachauik pluton contains average to above average uranium and thorium (5.7 ppm and 22.5 ppm, respectively), and the Bendeleben pluton contains average amounts of uranium and thorium (3.4 ppm and 16.7 ppm, respectively). The three plutons show compositional and textural differences indicative of different source materials that may have controlled the distribution of uranium and thorium. The high uranium and thorium contents of the Darby pluton, similar to those of the Conway Granite of New Hampshire which has been mentioned as a possible low-grade thorium resource, suggest that this pluton may be a favorable area for economic concentrations of uranium and thorium.

Alaska↗
USGS1976

Thin-skinned tectonics and potential hydrocarbon traps: Illustrated by a seismic profile in the Valley and Ridge province of Tennessee

Seismic data, although limited to a small part of the western half of the Valley and Ridge province in Tennessee, confirm that the structural style is thin-skinned and that there is a fundamental change from west to east in both the total section preserved and the structural complexities that exist in the subsurface. Cambrian to Upper Ordovician rocks in the Valley and Ridge province have been thrust westward over a 4-mile (6.4-km) projection of Cambrian through Mississippian rocks of the Appalachian Plateau. Structure within the plateau projection is characterized by splay anticlines, whereas structure in the Valley and Ridge is dominated by a series of imbricate thrust sheets containing isolated fault-bound masses of Cambrian sandstone and shale. Both splay anticlines and large fault-bound masses of rocks preserved in the subsurface in east Tennessee may be favorable fracture-porosity traps for the accumulation of hydrocarbons.

Tennessee↗
USGS1975

Phosphate fertilizer materials in Colombia; imports, uses, and domestic supplies

The distribution of potentially economic phosphate deposits and the locations of major users of phosphate products in Colombia are some of the economic factors that indicate the capability of the deposits to supply domestic demands. Much research is required to determine the types of processing plants needed and to outline changes from standard procedures, but there is little doubt that with proper planning a phosphate chemical industry could be developed that would supply domestic demands for the forseeable future.

Journal of Research of the U.S. Geological Survey↗
USGS1975

Description of the geoelectric section, Rattlesnake Hills unit 1 well, Washington

A complex 64-in. normal log from the 3,249-m-deep Rattlesnake Hills well was digitized and reduced to a form resembling a simple resistance log. The simplified form of the log made it possible to recognize three major geoelectric intervals in the well that were not apparent on the original log. The apparent resistivity values from each geoelectric interval are grouped into a frequency-distribution table, where midpoints of the class interval are corrected for the effects of hole diameter and mud resistivity. Using corrected class-interval midpoint resistivities, first-approximation values are calculated for five geoelectric parameters: total transverse resistance, total longitudinal conductance, average longitudinal resistivity, average transverse resistivity, and the coefficient of anisotropy. Comparison of anisotropies, resistivity variations, and resistivity-frequency polygon shapes indicates quantitative differences among the three geoelectric intervals.

Washington↗
USGS1976

High-level plateaus of the southeastern Beartooth Mountains, Montana and Wyoming: remnants of an exhumed sub-Cambrian marine plain

The Beartooth Mountains of south-central Montana and northwestern Wyoming are a northwesterly trending high rugged range made up mainly of Precambrian metamorphic rocks. The southeastern part of the range is characterized by extensive high-altitude flat or gently rolling plateaus separated by deep glaciated canyons. The plateaus along the crest of the range are at altitudes of more than 3,350 metres (11,000 ft), whereas those on the flanks of the range are much lower. They are almost entirely on Precambrian rocks, and only small patches of Cambrian sedimentary rocks still remain at a few places in the high mountains. Topographic profiles across the southeastern Beartooth Mountains show that: (1) plateaus bearing the sedimentary remnants lie very close to the position of the sub-Cambrian depositional surface as projected from known occurrences of that surface along the south side of the mountains; (2) other plateaus on the crest and southwest flank also lie near this projected position; and (3) high plateaus and other summits on the northeast slope in areas distant from known or projected positions of the sub-Cambrian surface are markedly accordant. We believe the plateaus along the crest and southwest flank of the range to be remnants of an exhumed marine plain of Early Cambrian or Precambrian age, and those on the northeast flank may possibly have a similar origin. The sub-Cambrian depositional surface was protected until early Tertiary time by a cover of Paleozoic sedimentary rocks, and parts of it probably were covered until Pliocene time by Eocene volcanic rocks. The surface subsequently has been profoundly modified by fluvial and glacial erosion and by mass wasting.

Montana, Wyoming↗
USGS1975

Structure and Paleozoic stratigraphy of a complex of thrust plates in the Fish Creek Reservoir area, south-central Idaho

Permian, Pennsylvanian, Mississippian, Devonian, and Silurian marine rocks of diverse facies are brought together in a complex of six thrust sheets in the Fish Creek Reservoir area on the north edge of the Snake River Plain, Idaho. The lowest structural element, the parautochthon, is made of more than 450 m (1,500 ft) of folded and faulted Devonian miogeosynclinal carbonate rocks present in a 6.5-km 2 (2.5-mi 2 ) window. Along the east margin of the window, a sliver of continental margin transitional carbonate rocks of Early Devonian and Late Silurian age assigned to the Roberts Mountains Formation is thrust over the miogeosynclinal rocks. The window of middle Paleozoic rocks is overridden along the Fish Creek thrust fault by the flysch facies of the Copper Basin Formation, a turbidite-submarine-fan sequence more than 1,000 m (3,300 ft) thick, of Mississippian age. About 4.8 km (3 mi) southwest of the window, about 100 m (300 ft) of deepwater siliceous oceanic facies clastic rocks are exposed, which are assigned with question to the Milligen(?) Formation of Devonian age. These clastic rocks are interpreted to be thrust over the Copper Basin Formation. The highest structural elements are sequences more than 610 m (2,000 ft) thick of interbedded sandy and conglomeratic limestones, quartzites, and conglomerates and interbedded siltstones and argillites of the Wood River Formation of Middle Pennsylvanian to Early Permian age. The Wood River Formation is in thrust contact with the Milligen(?) Formation in the southwest part of the mapped area and with Copper Basin Formation along the west side of Fish Creek Reservoir. All the thrust sheets have moved eastward. The minimum distance moved is estimated from sedimentation models and facies reconstructions to range from perhaps several kilometres for the allochthon of the Roberts Mountains Formation to 48 km (30 mi) for the Milligen(?) Formation allochthon. The principal period of thrusting was post-Early Permian (post-Wood River Formation) and preEocene (pre-Challis Volcanics) and is of probable Sevier age. Middle Paleozoic rocks of the Milligen and Roberts Mountains Formations, however, also may have been involved in an earlier period of thrusting of latest Devonian to earliest Mississippian age related to the Antler orogeny. The thrust sheets were deformed into a northwest-trending dome in late Mesozoic time and were broken by basin-range faults during the Tertiary.

Idaho↗
USGS1975

Silurian and Devonian miogeosynclinal and transitional rocks of the Fish Creek Reservoir window, central Idaho

Documentation of Devonian continental-shelf shallow-water carbonate rocks in the core of the Fish Creek Reservoir window shifts the known westernmost limit of the Devonian miogeosyncline 50 km (30 mi) southwest across the structural grain from the well-known miogeosynclinal sequence in the Lost River Range. The miogeosynclinal carbonate sequence in the window has a minimum thickness of 450 m (1,500 ft). It comprises the upper Lower Devonian (Emsian) and lower Middle Devonian (Eifelian) Carey Dolomite (new), the upper Middle Devonian (Givetian) and Upper Devonian Jefferson Formation, and the Upper Devonian Picabo Formation (new). Conodont faunas precisely date the Carey. The Picabo Formation, composed of interbedded sandy dolomite-pebble conglomerate and dolomitic quartzose sandstone, is unlike any previously described formation of Late Devonian or Early Mississippian age in central Idaho. It resembles parts of the Stansbury, Beirdneau, Leatham, and Victoria Formations, which reflect areas of local Late Devonian uplift and erosion of older shelf rocks in northern Utah and southeastern Idaho. Transitional (continental-slope) rocks of the Roberts Mountains Formation representing reef and offreef facies are thrust over the Devonian shelf sequence within the Fish Creek Reservoir window. The Roberts Mountains Formation here is precisely dated as latest Silurian (Pridolian, eosteinhornensis Zone) through earliest Devonian (Lochkovian) by a sequence of conodont faunas. The easternmost known exposures of possible Devonian siliceous facies rocks assigned to the Milligen(?) Formation are present less than 4.8 km (3 mi) southwest of the shelf sequence. Structural relations and paleotectonic reconstructions suggest that they have a minimum eastward translation of 32 km (20 mi). The Devonian continent-ocean basin interface, along which the Antler orogenic belt developed at this latitude, probably was located near the east edge of the present Idaho batholith.

Idaho↗
USGS1975

Stratigraphy, conodont dating, and paleotectonic interpretation of the type Milligen Formation (Devonian), Wood River area, Idaho

The Milligen Formation at and near its type locality in the Wood River area is considerably older than and unrelated to rocks of Early Mississippian age called Milligen Formation in the Lost River Range and other ranges of east-central Idaho. Conodont faunas were found in limestones of a thin upper member of the sparsely fossiliferous marine Milligen Formation in its principal reference section at Milligen Gulch, at Fisher Canyon, and near Bellevue, Idaho. The faunas include indigenous conodonts here assigned to the early Late Devonian (early Frasnian) Lower and Middle Polygnathus asymmetricus Zones, and reworked conodonts derived from several Middle and Early Devonian conodont zones. An underlying much thicker argillite member of the Milligen contains fewer limestones, but a thin encrinite interbed near the middle of the member yielded early Middle Devonian (Eifelian) conodonts. This lower member probably represents most of Middle and Early Devonian time. Although its base is nowhere exposed in the Wood River area, the Milligen is inferred to have been deposited on the Silurian Trail Creek Formation, which crops out just to the east in the Pioneer Mountains. The age of the Milligen is therefore wholly Devonian and the highest fossiliferous beds are no younger than early Late Devonian. Reworked Middle and Early Devonian conodonts in limestone turbidites of the upper member of the Milligen Formation are identical to conodonts found in shelf (miogeosynclinal) carbonate rocks farther east. A postulated eastern source for the turbidites is supported by new data on the distribution, thickness, and tectonic facies of Devonian rocks that suggest the presence of a Late Devonian ridge on the continental shelf east of the Milligen depositional area. The Milligen Formation was intensely folded and was emergent during most of the Mississippian time when it formed part of the Antler Highlands, which shed flysch sediments eastward into the Copper basin. The Wood River Formation of Pennsylvanian and Permian age was then deposited over a subdued topography on the Milligen Formation. The Hailey Conglomerate Member at the base of the Wood River filled many irregularities in the surface. This depositional contact later was largely destroyed and the contact between the Milligen and Wood River is now a regional thrust fault at most places.

Idaho↗
USGS1975

A late Holocene pollen record from Pearson's Pond, Weeks Creek landslide, San Francisco Peninsula, California

A 210-cm core from Pearson's Pond yielded a pollen record for the past 3 millenia. Prior to A.D. 1000 the pond biota was particularly sensitive to climatic fluctuations. Two wet intervals occur in the pollen record, between 350 B.C. and A.I). 0 and between A.D. 650 and 900. The pollen record suggests that the Weeks Creek landslide may have moved at least twice prior to 3,000 years ago and that the middle part of the glide has been stable since that time. Seasonal changes produce large annual fluctuations in the water table, and climatic changes during the past 3,000 years have produced significant changes in the timing and magnitude of the annual changes. Climatic records such as the one presented here will help us to understand and separate the effects of climate and earthquakes on the landslide history of the Holocene deposits of the San Francisco Bay area.

California↗