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At least 1,081 records · Page 60Linked to original sources
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↗
USGS1975

Modern pollen surface samples: An analysis of subsamples

Multiple subsamples of pollen samples obtained from the modern soil surface at two sites in southern Arizona were individually collected and analyzed to evaluate the practice of mixing subsamples when collecting modern surface samples. Results suggest that at least five subsamples must be mixed in order to avoid collecting a sample that is not representative of the local pollen rain.

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

Absolute age of disseminated uraninite in Wheeler Basin, Grand County, Colorado

Uranium and lead isotopic analyses of monazlte and uraninite from the disseminated uraninite occurrence at Wheeler Basin, Grand County, Colo., indicate that these minerals formed 1,446±20 m.y. ago. This time correlates well with intrusion of the Silver Plume Granite. The uraninite and monazite were also affected by a later disturbance at 880±130 m.y., but show essentially no effects of subsequent events. This secondary disturbance may have been due to intrusion of dikes related to the Pikes Peak batholith, dated at 1,041±13 m.y. ago.

Colorado↗
USGS1975

Ion-selective electrode determination of iodine in rocks and soils

Use of an iodide-ion-selective electrode permits rapid and fairly accurate determination of iodine (as iodide) in rocks and soils. When a 1-g sample is used, concentrations as small as 0.5 ppm can be determined with a precision of about 25-percent relative standard deviation. When bromine concentration is greater than 5 ppm, the same method can be used for bromine determination. The procedure merits further investigation as a possible tool in geochemical prospecting.

Journal of Research of the U.S. Geological Survey↗
USGS1976

Fission-track ages of sphene and apatite of granitic rocks of the Salinian block, Coast Ranges, California

Fission-track ages have been determined on apatite and sphene from granitic rocks of the Salinian block, California Coast Ranges. The 26 age determinations on sphene range between 68 and 93 m.y. The 24 age determinations on apatite have a greater variation, ranging from 3 to 74 m.y. None of the fission-track ages appear to reflect times of intrusion. The Pinnacles volcanic field of Miocene age apparently has thermally affected apatite ages in the central Gabilan and eastern Santa Lucia Ranges. Reduced apatite ages in the area between the Farallon Islands and the Monterey Peninsula may also be the result of Miocene volcanic activity, but the evidence is less conclusive. Fission-track ages on sphene correlate closely with previously determined potassium-argon ages on hornblende and biotite but show an unexplained "bimodal" age distribution, the ages in the Gabilan and Santa Lucia Ranges being slightly, but consistently, lower (avg 75 m.y.) than the ages for terrane to the north and south (avg 85 m.y.) The overall pattern of the sphene and apatite fission-track ages, distinctly different from that of the central Sierra Nevada, may be a "fingerprint" of correlative value in locating the parent terrane of the "ripped-off" Salinian block.

California↗
USGS1978

Infiltration from tributary streams in the Susquehanna River basin, New York

As tributary streams in the Susquehanna River basin leave narrow upland valleys and enter larger valleys floored with permeable stratified glacial drift, they lose water by infiltration through streambeds. The infiltration rate is generally slow near the point of entering a larger valley, but farther downstream it is much faster and is approximately constant per unit distance along a given stream. A conservative average value of infiltration rate in the downstream reach is 10 liters per second per 100 meters of channel. Infiltration from these streams is little influenced by stream width, depth, or temperature and seems to be controlled by permeability distribution beyond the streambed in the alluvium or underlying glacial drift rather than by permeability at the streambed. Hydraulic conductivity of earth materials near each of the streams studied was calculated by applying models that describe steady-state saturated flow into isotropic materials with various boundary conditions. Hydraulic conductivities of 4 to 41 meters per day were obtained; 13 meters per day is suggested as a conservative average value for silty gravel alluvium in the Susquehanna River basin.

New York↗
USGS1976

Revision of the Carboniferous genus Aulina Smith (Coelenterata, Anthozoa)

Morphologic and stratigraphic evidence bearing on the phylogenetic relationships of aulate Carboniferous corals suggests that species previously assigned to the genus Aulina Smith represent at least six different lineages that descended from three different ancestral genera. A classification designed to better reflect phylogenetic relationships includes the new genera Aulokoninckophyllum , Aulostylus , Solenodendron , and Vesiculotubus . The new North American taxa Aulostylus tubiferus tubiferus , A . tubiferus eotubiferus , and A . bamberi are described and illustrated. Two new Chinese species, Aulina ( Pseudoaulina ) loi and A . ( P .) sinensis , are also proposed.

Journal of Research of the U.S. Geological Survey↗
USGS1978

Relationship between hydrology and bottomland vegetation in the Ozark Mountains of Missouri

The identification of plants and plant assemblages that are common to stream reaches that gain water and those that do not is an important key in the study of limestone hydrology. In the Ozark Mountains of Missouri, a rapid change from a stream-channel growth of abundant willows ( Salix spp.), touch-me-nots ( Impatiens capensis ), and sedges such as Carex Frankii and Eleocharis spp. to an abundant growth of bluestars ( Amsonia illustris ) indicates a rapid increase in depth to water. Vegetative indicators of hydrologic conditions are most helpful when used in conjunction with other information, but they are independently useful in pinpointing areas of abrupt hydrologic changes.

Missouri↗
USGS1976

New molluscan assemblages from the upper member of the Twin River Formation, western Washington: Significance in Neogene chronostratigraphy

New molluscan assemblages of provincial early Miocene age from a previously unrecognized fossiliferous interval of 400 to 500 metres in the uppermost part of the Twin River Formation, western Washington, are referable to the upper part of the "Blakeley" [or Matlockian] Stage. The new biostratigraphic data provide, for the first time, definition of the uppermost part of the "Blakeley" Stage and the boundary between it and an unnamed stage of late early Miocene age represented by the Clallam Formation and its megafauna. In contradistinction to earlier studies, the upper boundary of the "Blakeley" Stage does not coincide with the upper boundary of the Zemorrian Stage of the foraminiferal chronology, the "Blakeley" boundary being at least 45 m higher and possibly much more. Nearly 60 species of mollusks from the upper few hundred metres of the Twin River Formation are recognized herein, and 40 of these are illustrated. Six species are previously undescribed.

Washington↗
USGS1978

Iron in water near wastewater lagoons in Yellowstone National Park, Wyoming

High dissolved-iron concentrations have been noted in water in wells used to monitor effluent that percolates from wastewater disposal lagoons near Old Faithful in Yellowstone National Park. The concentration of dissolved iron in water in a well increased from 80 μ g/L (micrograms per liter) before a nearby lagoon was .used for disposal of effluent to 17000 μ g/L after the lagoon was used. The effluent contained 180 μ g/L of dissolved iron, and nearby Iron Spring Creek contained 30 μ g/L or less of dissolved iron above and below the lagoons. Organic carbon, nitrogen, and sulfur in the effluent as methane, ammonia, and hydrogen sulfide are oxidized to carbon dioxide, nitrate, and sulfate, respectively, in the unsaturated zone and possibly in the saturated zone as ground water moves through sand and gravel toward Iron Spring Creek. This oxidation results in simultaneous reduction of iron in the sand and gravel from the insoluble ferric phase to the soluble ferrous phase. As ground water high in dissolved iron discharges at land surface near the stream, oxygen from the atmosphere oxidizes the iron back to the insoluble ferric phase, and ferric hydroxide precipitates. Ferric hydroxide also precipitates in some of the monitoring wells. Iron bacteria and other organisms are associated with the precipitates.

Wyoming↗
USGS1978

Studies of hydroxyaluminum complexes in aqueous solution

The coagulating ability of partly neutralized AlCl 3 solutions used in water treatment depends on their basicity, expressed here as the ratio NaOH/AlC 3 . This work presents an identification of the aluminum species active in the coagulation process. The results give rise to an interpretative model which is consistent with those models proposed for high ionic strength by other investigators.

Journal of Research of the U.S. Geological Survey↗
USGS1976

Revision of Mississippian stratigraphy, eastern Idaho and northeastern Utah

New paleontologic evidence requires a revision of previous interpretations of the stratigraphy of Mississippian sequences in the Cordilleran miogeosyncline of eastern Idaho and northeastern Utah. A postulated unconformity between rocks of early Osagean age and rocks of middle Meramecian age is no longer tenable in the light of new data. The new evidence supports continuous deposition from the Lodgepole Limestone (Kinderhookian and early Osagean age) into the Little Flat Formation (early Osagean to middle Meramecian age) and its equivalents, and the interpretation of a phosphatic siltstone and shale interval in the lower part of the Little Flat Formation as a starved-basin facies.

Idaho, Utah↗
USGS1976

Simulation of forest changes related to hydrologic variables in the Atchafalaya River basin, Louisiana

Results of forest-trend modeling from one data set in the Atchafalaya River basin show that predicted forest acreage totals for 16 forest types agree within 30 percent of actual values in two-thirds of the comparisons. A forest-trend simulation model based on statistical regression relations of forest and hydrologic variables and constrained by forest succession concepts was developed using observed data from twenty-four 8-square-mile (20.74-square-kilometre) quadrats. Forest and hydrologic data at each quadrat were sampled in time at three 4-mile (6.44-kilometre)-wide strips across the basin. The model predicts changes in forest-type acreages due to hydrologic change in time steps, or forest acreage transition, of 21 years. Further basin-wide quadrat simulations are planned using hydrologic input data from a flow-sediment model of the basin currently being developed. Other ecosystem models could be appended to the forest-trend simulation model.

Louisiana↗