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Research about Canada, United States

Source-linked reports with geographic coverage including Canada, United States.

At least 1,279 records · Page 71Linked to original sources
USGS1975

K-Ar age of the Similkameen Batholith and Kruger Alkalic Complex, Washington and British Columbia

Twelve K-Ar age determinations from the Similkameen batholith and the contiguous Kruger Alkalic Complex, including seven newly reported here, range from 69.9 m.y. to 177.2 m.y. Ages of coexisting hornblende and biotite show discordancies ranging from about 72 m.y. to 106 m.y., with hornblende consistently showing the greater analytical age. The hornblendes, with one exception, show increasing analytical age with increasing potassium content and approximately fit a 191.0-m.y. 40 Ar (radiogenic )/K isochron. The isochron shows a negative intersection with the 40 Ar (radiogenic) axis, indicating partial argon loss. The large negative deviation from the isochron of one low-potassium sample suggests that the isochron is biased to older ages. If so, the Similkameen and Kruger rocks probably crystallized between roughly 177 m.y. and 191 m.y. ago. The discordancies between hornblende and coexisting biotite are attributed to argon loss during one or possibly more episodes of thermal metamorphism, the most recent of which was probably between about 50 and 70 m.y. ago. This bracket is based on the age of apparently unmetamorphosed sedimentary deposits containing detritus from the Similkameen and Kruger bodies and the analytical age of the youngest biotite.

British Columbia, Washington↗
USGS1974

Thin and layered subcontinental crust of the Great Basin western North America inherited from Paleozoic marginal ocean basins?

The seismic profile of the crust of the northern part of the Basin and Range province by its thinness and layering is intermediate between typical continental and oceanic crust and resembles that of marginal ocean basins, especially those with thick sedimentary fill. The geologic history of the Great Basin indicates that it was the site of a succession of marginal ocean basins opening and closing behind volcanic arcs during much of Paleozoic time. A long process of sedimentation and deformation followed throughout the Mesozoic modifying, but possibly not completely transforming the originally oceanic crust to continental crust. In the Cenozoic, after at least 40 m.y. of quiescence and stable conditions, substantial crustal and upper-mantle changes are recorded by elevation of the entire region in isostatic equilibrium, crustal extension resulting in Basin and Range faulting, extensive volcanism, high heat flow and a low-velocity mantle. These phenomena, apparently the result of plate tectonics, are superimposed on the inherited subcontinental crust that developed from an oceanic origin in Paleozoic time and possibly retained some of its thin and layered characteristics. The present anomalous crust in the Great Basin represents an accretion of oceanic geosynclinal material to a Precambrian continental nucleus apparently as an intermediate step in the process of conversion of oceanic crust into a stable continental landmass or craton.

western North America↗
USGS1974

Prehnite- and pumpellyite-bearing mineral assemblages, west side of the Appalachian metamorphic belt, Pennsylvania to Newfoundland

Prehnite- and/or pumpellyite-bearing meta-igneous rocks are found on the west side of the Appalachian metamorphic belt (1) near Jonestown, south-eastern Pennsylvania; (2) on Rensselaer Plateau, eastern New York; (3) near Quebec City, Quebec; and (4) at Little Port, Humber Arm, western Newfoundland. The assemblages critical to determining the conditions of metamorphism are (1) chlorite-epidote-hematite-pumpellyite-prehnite; actinolite-chlorite-hematite-pumpellyite-stilpnomelane; (2) actinolite-chlorite-epidote-stilpnomelane; chlorite-epidote-pumpellyite-stilpnomelane; chlorite-epidote-hematite-pumpellyite; (3) chlorite-epidote-hematite-pumpellyite-stilpnomelane; chlorite-epidote-pumpellyite-prehnite; and (4) chlorite-epidote-prehnite; chlorite-prehnite-stilpnomelane; chlorite-epidote-pumpellyite-prehnite. One pumpellyite-bearing rock from western Newfoundland shows a later vein of analcime-calcite. All the assemblages also include quartz, sphene, calcite, K-mica, and albite. Analysis of the mineral assemblages by the Schreinemakers method for the phases actinolite-chlorite-epidote-hematite-prehnite-pumpellyite-stilpnomelane shows that the different localities can be assigned different metamorphic grades. Though the detailed results of the Schreinemakers analysis depend on the assumed source of ferric iron in epidote, the major conclusions are not affected. The thermodynamic role of calcite is more problematic, but it appears that CO 2 did not behave as a boundary-value component during metamorphism. If calcite is treated as an excess phase, the Schreinemakers bundle decomposes to a net in a multisystem. Plotted on such a net, the various localities again occupy different parts signifying different metamorphic grades. The occurrence of pumpellyite-bearing assemblages on the west flank of the northern Appalachian metamorphic belt might suggest that these assemblages, contrary to the ideas of Miyashiro and of others, do not indicate high-pressure and low-temperature type of metamorphism. These assemblages, however, are compatible with an alternative interpretation as remnants of a high-pressure, low-temperature Taconic metamorphic regime, whose imprint within most of the Appalachian metamorphic belt has been obliterated by later events. Such a reconstruction is compatible with the suggestion that this zone, lying near the margin of the early Paleozoic craton, was an active subduction zone during the Taconic orogeny.

Appalachian metamorphic belt↗
USGS1974

Some helminth parasites of the American bald eagle

Bald eagles ( Haliaeetus leucocephalus ) found dead or moribund in the United States and Canada and submitted to Patuxent Wildlife Research Center were examined for helminth parasites. Nine genera of helminths were reported which include new host records for Clinostomum complanatum , Neogogatea pandionis , Centrorhynchus sp., Serratospiculum amaculata , Capillaria contorta , and Habronema americanum .

Journal of Wildlife Diseases↗
USGS1974

Classification and new genera of noncystimorph colonial rugose corals from the Onesquethaw stage in New York and adjacent areas

A. proposed classification is outlined for 39 species of colonial rugose corals in 10 genera belonging to the families Stauriidae, Craspcdophyllidae (including Cylindrophyllinae new subfamily and Craspedophyllinac), Disphyllidae?, and Zaphrentidae, from the Onesquethaw and lower Cazenovia Stages in New York and adjacent areas. These corals are described or redescribed in another report now in press. Three new genera, Asterobillingsa , Grewgiphyllum , and Cyathocylindrium , are described in this report.

New York, Ontario↗
USGS1972

Eastward migration of blue-winged teal

Of 3,789 recoveries of blue-winged teal ( Anas discors ) banded prior to the hunting season in the prairie pothole region, 183 (4.8 percent) were recovered, due east in New England, Ontario, Quebec, and the Maritime Provinces during the subsequent hunting season. Of 19 recoveries looked at in detail, all were banded as either hatching-year (flying young) or local (flightless young) birds. A blue-winged teal banded in Minnesota in September was retrapped in October in South Carolina, before being shot later that month in Colombia, South America.

North Dakota, Minnesota↗
USGS1971

Small plate tectonics in the northeastern Pacific

Lithospheric plate motions in the northeastern Pacific were complicated at about 2.5 m.y. B.P. by the movement along a major northeast-trending fault cutting Cascadia Basin. An estimate of the slip rate along this fault gives critical information on the relative motions of four geometrically interdependent blocks. The fault is presently inactive. Seventy km of slip along this fault during 2 m.y. or less gives an average slip rate of about 3-5 cm/yr or greater, and resulting plate motions suggest a significantly greater rate of net subduction along the continental margin off Oregon than off Washington and Vancouver Island. Subduction rate off Oregon is less sensitive to slip rate along this fault than is subduction off Washington.

British Columbia, Oregon, Washington↗
USGS1971

Classification of natural ponds and lakes in the glaciated prairie region

The wetland classification system for the United States adopted by the Bureau of Sport Fisheries and Wildlife in 1953 is described by Martin et al (1953) and by Shaw and Fredine (1956). That classification has been followed by many biologists in recent years and is especially useful in categorizing in a general manner the wetlands throughout the country over a span of years. It has become apparent, however, that for research and intensive management a dynamic classification system that more precisely reflects seasonal, regional, and local variations in the environment is needed. To establish a detailed wetland classification system for all of North America will require intensive ecological investigation of wetlands in each of the major biogeographical regions.

Alberta, Iowa, Manitoba, Minnesoata, Montana, Nort↗
USGS1970

Concentrations of trace elements in Great Lakes fishes

The concentration of 15 trace elements was determined by activation analysis of samples of whole fish and fish livers from three of the Great Lakes: Michigan, Superior, and Erie. The average concentrations of 7 elements in 19 whole fish from 3 species were as follows: uranium, 3ppb (parts per billion); thorium, 6ppb; cobalt, 28ppb; cadmium, 94ppb; arsenic, 16ppb; chromium, 1ppm; and copper, 1.3ppm. The average concentrations of 8 elements in 40 liver samples from 10 species of fish were as follows: uranium, 2ppb; thorium, 2ppb; cobalt, 40ppb; copper, 9ppm; zinc, 30ppm; bromine, 0.4ppm; arsenic, 30ppb; and cadmium, 0.4ppm. Other elements observed in most of the samples were: antimony, 5100ppb; gold, 25ppb; lanthanum, 120ppb; rhenium, 0.55ppb; rubidium, 0.064ppm; and selenium, 0.12ppb.Trace element concentrations varied with species and lake. Uranium and thorium varied with species, but not for the same species from different lakes. The levels of copper, cobalt, zinc, and bromine varied little between species and lakes. The concentration of cadmium, arsenic, and chromium varied between species and with species between lakes.

Great Lakes↗
USGS1969

Lower Llandovery of the northern Appalachians and adjacent regions

Rocks of clearly dated early Llandovery age, as well as rocks that can logically be classed as early Llandovery from their regional relationships, appear to be more widespread than recognized, heretofore, in the northern Appalachians and adjacent regions. Their areal distribution and lithology permit a generalized reconstruction of the paleogeography, which consisted, in general, of three source areas alternating from east to west with three belts of clastic sedimentation. The westernmost clastic belt grades laterally westward into the carbonate rocks of the North American platform. The Central Clastic Belt encloses a belt containing impure carbonates with clastic detritus and clastic interbeds, and, locally, relatively clean carbonate deposits. Llandovery age rocks of the platform include the Manitoulin Dolomite and the Ellis Bay Formation. In the deposits to the east, coeval rocks occur, in part or in whole, within the limy and clastic deposits of the Carys Mills Formation and the Matapedia Group, as well as in the following clastic rock formations: Grimsby, Shawangunk, Tuscarora, Massanutten, Clinch, Smyrna Mills, Perham, Cabano, Weir, Beechhill Cove, Ross Brook, and White Rock.

Maine, New Brunswick, Quebec↗