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At least 433 records · Page 24Linked to original sources

USGS2015

Multi-decadal trends in spring arrival of avian migrants to the central Arctic coast of Alaska: Effects of environmental and ecological factors

Warming in the Arctic has caused the transition from winter to summer to occur weeks earlier over the last half century, yet little is known about whether avian migrants have altered their timing of arrival on breeding areas to match this earlier seasonal transition. Over a 50-yr period, we examined trends in the timing of the first arrival for 16 avian migrant species at the terminus of their northward migration along the central Arctic coast of Alaska and compared these trends to factors potentially influencing migration phenology. Date of first arrival occurred an average of 0.12 d yr −1 or 6 d (range = 3–10 d) earlier across all species and did not differ significantly among species between 1964 and 2013. Local climatic variables, particularly temperature, had a greater effect on a species first arrival date than did large-scale climatic predictors. First arrival date was 1.03 d earlier for every 1°C annual change in temperature, but there was nearly a 2-fold difference in the range of responses across species (0.69–1.33 d °C −1 ), implying that some species did better than others at timing their arrival with changing temperature. There was weak support for an influence of foraging strategy, migration distance, and flight path on timing of first arrival. Our findings, like others from temperate latitudes, indicate that avian migrants are responsive to changing environmental conditions, though some species appear to be more adaptive than others.

Alaska↗

USGS1968

European Cretaceous flints on the coast of North America

Flint pebbles and nodules from the Upper Cretaceous chalks of Europe occur offshore and at many seaports along the Atlantic coast of North America, where they were brought as ship's ballast. Isolated pieces imported from Europe as gunflints also are present.

Science↗

USGS1970

Metamorphic waters from the Pacific tectonic belt of the west coast of the United States

Waters unusually rich in ammonia, boron, carbon dioxide, hydrogen sulfide, and hydrocarbons are found in more than 100 localities along the Pacific coast of the United States. The waters are believed to be products of low-grade metamorphism of marine sediments. The marine sedimentary rocks would have to be tectonically emplaced below crystalline rocks in many places. Mercury are deposits are probably also products of the low-grade metamorphism.

Pacific coast↗

USGS2012

Prevalence, environmental loading, and molecular characterization of Cryptosporidium and Giardia</i isolates from domestic and wild animals along the Central California Coast

The risk of disease transmission from waterborne protozoa is often dependent on the origin (e.g., domestic animals versus wildlife), overall parasite load in contaminated waterways, and parasite genotype, with infections being linked to runoff or direct deposition of domestic animal and wildlife feces. Fecal samples collected from domestic animals and wildlife along the central California coast were screened to (i) compare the prevalence and associated risk factors for fecal shedding of Cryptosporidium and Giardia species parasites, (ii) evaluate the relative importance of animal host groups that contribute to pathogen loading in coastal ecosystems, and (iii) characterize zoonotic and host-specific genotypes. Overall, 6% of fecal samples tested during 2007 to 2010 were positive for Cryptosporidium oocysts and 15% were positive for Giardia cysts. Animal host group and age class were significantly associated with detection of Cryptosporidium and Giardia parasites in animal feces. Fecal loading analysis revealed that infected beef cattle potentially contribute the greatest parasite load relative to other host groups, followed by wild canids. Beef cattle, however, shed host-specific, minimally zoonotic Cryptosporidium and Giardia duodenalis genotypes, whereas wild canids shed potentially zoonotic genotypes, including G. duodenalis assemblages A and B. Given that the parasite genotypes detected in cattle were not zoonotic, the public health risk posed by protozoan parasite shedding in cattle feces may be lower than that posed by other animals, such as wild canids, that routinely shed zoonotic genotypes.

California↗

USGS1967

Age, composition, and tectonic setting of the granite island, Hon Trung Lon, off the coast of South Vietnam

Hon Trung Lon , a granite island off the coast of South Vietnam , is composed solely of a unique, extremely differentiated, high-silica alkali granite of Cretaceous age . An adjacent island , Hon Trung Nho, is composed solely of rhyolitic rock of similar composition . The Hon Trung Nho rhyolite may be a fine-grained equivalent of the granite . Whole-rock potassium-argon analysis suggests that the age of the Hon Trung Lon granite is greater than 70 m.y. and less than 100 m.y. This age implies a previously unrecognized period of intrusion for the zone of granitic rocks outcropping along the northeast side of the Gulf of Thailand. Extensive investigation of the Mesozoic and Tertiary igneous rocks of Southeast Asia, particularly Indochina, including reliable geochronological work, is needed to trace the geologic events that produced the complicated structural features and orogenic history of this region. Existing data suggest that Southeast Asia has been the site of active orogeny since the Paleozoic and that the Hon Trung Lon granite was emplaced through a sialic crust which has been evolving in this area for at least the last 400 m.y.

south Vietnam Islands↗

USGS1970

Faulting in the Burro Mountain area, California Coast Ranges, and its relation to the Nacimiento fault

The northwest-striking Nacimiento fault, in the southern Coast Ranges of California, has generally been regarded as the boundary between two major structural blocks: the Nacimiento block to the southwest, in which the basement rocks belong to the Franciscan Formation (Upper Jurassic to Upper Cretaceous), and the Salinian block to the northeast, in which the basement rocks are granitic and high-grade metamorphic. It has been found, however, that in the Burro Mountain area of the southern Santa Lucia Range, the “Nacimiento” fault of Jennings (1959) is nearly vertical and is within the Nacimiento block. In this area, the Franciscan Formation crops out northeast of the “Nacimiento” fault through windows in an older, low-angle thrust fault that brings the Asuncion Group of Taliaferro (1943) (Upper Cretaceous) over the Franciscan Formation. The fault boundary between the Nacimiento and the Salinian blocks must therefore lie farther to the northeast, where it may be buried beneath the Asuncion Group and younger strata. This conclusion is supported by Hanna's recent aeromagnetic work (1969).

California↗

USGS1970

Quartz gabbro and anorthositic gabbro: Markers of offset along the San Andreas fault in the California Coast Ranges

Large-scale lateral movement on the San Andreas fault zone is suggested by the distribution of gabbroic rocks that may be slivered remnants of oceanic crust. Distinctive and unusual hornblende quartz gabbro and anorthositic gabbro that are virtually identical both petrographically and chemically are exposed at Logan and Gold Hill in the Coast Ranges along the San Andreas fault. The hornblende quartz gabbro is made up of labradorite to bytownite plagioclase, hornblende, and quartz, with very minor biotite and pyroxene, and accessory metallic opaques and apatite. The coarse-grained anorthositic gabbro with anorthositic layers and associated gneiss is made up mainly of labradorite to bytownite plagioclase, hornblende, lesser clinopyroxene, and, locally, orthopyroxene. The present 100 mi of separation between these two gabbro bodies is probably due to displacement along the San Andreas fault of what was originally one gabbro mass. Somewhat similar quartz gabbro and anorthositic gabbro associated with ultramafic rocks near Eagle Rest Peak in the San Emigdio Mountains may represent a source for the Logan and Gold Hill slivers. This suggests a minimum right-lateral movement of about 200 mi on the San Andreas fault zone. Anorthositic gabbro clasts from Cretaceous conglomerate in the Gualala area have strong resemblance to gabbroic rocks at Logan, Gold Hill, and Eagle Rest Peak and speculatively suggest 350 mi of right-lateral movement on the fault zone. It is tentatively suggested that the gabbro clasts of Gualala may have been shed from a large area of exposed gabbroic oceanic crust, pieces of which occur as fault slivers at Gold Hill and Logan. It is further suggested that the Eagle Rest Peak locality may be a relatively in-place exposure of this gabbroic oceanic crust that lies near a continental-oceanic interface. This interface, thought to represent a fossil subduction zone between Franciscan and Sierran basements, appears to be overlain depositionally by Eocene sedimentary rocks. If these Eocene deposits do “seal over” the possible subduction zone, it suggests that movement on such a zone ceased before the Eocene deposition, and that the new and different pattern of right-lateral movement on the San Andreas fault zone probably began sometime later.

California↗

USGS1971

Age of the Mesozoic oceanic crust in the California Coast Ranges

K-Ar ages of approximately 155 m.y. were measured on minerals from ophiolites at two localities in the California Coast Ranges. Upper Jurassic rocks of the Great Valley sequence are in depositional contact with underlying ophiolites, which are interpreted as Mesozoic oceanic crust that formed during differentiation of mantle material at a spreading ridge some 15 m.y. before deposition of the Great Valley sequence began.

California↗

USGS1983

Storm-controlled oblique dunes of the Oregon coast

The large (mean height 25 m, spacing 300 m), relatively straight-crested dunes of the central Oregon coast migrate an average of 3.8 m/yr toward an azimuth of 26°. The dunes are transverse to the strong, south-southwesterly winter storm winds that are responsible for their basic form, orientation, and migration. The dry, moderate, north-northwesterly summer winds modify the dune form but not the dune trend. Comparison of the sand transport calculated from wind data and the transport measured from dune migration indicates that the actual transport by the wet southerly winds is only one-third of the amount calculated assuming dry conditions. The resultant (vector-mean) transport rate, as recalculated by comparison of the measured and initially calculated rates, is 34 m 3 /m·yr toward an azimuth of 45°. The dunes are thus oblique by our definition of an oblique dune (angle between dune trend and resultant transport direction between 15° and 75°). The internal structures of the dunes confirm northward migration during wet conditions. Evidence for deposition during wet conditions includes slipface deposits deformed mostly by sliding and various structures formed by the adhesion of sand grains to wet surfaces. Most summer deposits are not preserved, but those on the basal apron (the gentle north slope at the base of the winter slipface) have a high preservation potential. A depositional model based on dune climbing predicts that the preserved record of oblique dunes formed by an obtuse-bimodal wind regime would consist of tabular sets of crossbeds in which the dip angles increase upward from the base of each set.

Oregon↗

USGS1973

Nodal tidal cycle of 18.6 yr.: Its importance in sea-level curves of the east coast of the United States and its value in explaining long-term sea-level changes

The 18.6-yr cycle of the Moon's nodes dominates the annual means of high water, low water, and range at Boston and at other East Coast harbors. The maxima and minima of the high-water and range curves agree closely with the 180° and 0° long. yr, respectively, of the Moon's ascending node, and are fairly well accounted for by tide-prediction equations. The curve of annual mean sea level also reflects the cycle, but more weakly. Recognition of the cyclical nature of tidal data both simplifies and clarifies assessments of longer term sea-level trends and points to the need to include only multiples of entire cycles in the computations of these trends. When the curves of mean high water and range are used, it is possible to recognize long-term sea-level trends rapidly and to determine whether these are attributable to tidal or nontidal causes. The data suggest that the secular sea-level rise during the 20th century is tidal in origin and may be caused by vertical movement of the oceanic floor. This has the effect of reducing the volume of ocean basins, and, by changing basin geometry, alters the characteristics of terrestrial tidal constituents (standing waves).

Atlantic Ocean↗

USGS2005

Radioisotopic and biostratigraphic age relations in the Coast Range Ophiolite, northern California: Implications for the tectonic evolution of the Western Cordillera

The Coast Range ophiolite (CRO) in northern California includes two distinct remnants. The Elder Creek ophiolite is a classic suprasubduction zone ophiolite with three sequential plutonic suites (layered gabbro, wehrlit-pyroxenite, quartz diorite), a mafic to felsic dike complex, and mafic-felsic volcanic rocks; the entire suite is cut by late mid-oceanic-ridge basalt (MORB) dikes and overlain by ophiolitic breccia. The Stonyford volcanic complex (SFVC) comprises three volcanic series with intercalated chert horizons that form a submarine volcano enclosed in sheared serpentinite. Structurally below this seamount are mélange blocks of CRO similar to Elder Creek. U/Pb zircon ages from plagiogranite and quartz diorites at Elder Creek range in age from 165 Ma to 172 Ma. U/Pb zircon ages obtained from CRO mélange blocks below the SFVC are similar (166–172 Ma). 40 Ar- 39 Ar ages of alkali basalt glass in the upper SFVC are all younger at ≈164 Ma. Radiolarians extracted from chert lenses intercalated with basalt in the SFVC indicate that the sedimentary strata range in age from Bathonian (Unitary Association Zone 6–6 of Baumgartner et al., 1995a ) near the base of the complex to late Callovian to early Kimmeridgian (Unitary Association Zones 8–10) in the upper part. The SFVC sedimentary record preserves evidence of a major faunal change wherein relatively small sized, polytaxic radiolarian faunas were replaced by very robust, oligo-taxic, nassellarian-dominated faunas that included Praeparvicingula spp. We suggest that CRO formation began after the early Middle Jurassic (172–180 Ma) collision of an exotic or fringing arc with North America and initiation of a new or reconfigured east-dipping subduction zone. The data show that the CRO formed prior to the Late Jurassic Nevadan orogeny, probably by rapid forearc extension above a nascent subduction zone. We infer that CRO spreading ended with the collision of an oceanic spreading center ca. 164 Ma, coincident with the oldest high-grade blocks in the structurally underlying Franciscan assemblage. We further suggest that the “classic” Nevadan orogeny represents a response to spreading center collision, with shallow subduction of young lithosphere causing the initial compressional deformation and with a subsequent change in North American plate motion to rapid northward drift (J2 cusp) causing sinistral transpression and transtension in the Sierra foothills. These data are not consistent with models for Late Jurassic arc collision in the Sierra foothills or a backarc origin for the CRO.

California↗

USGS2007

Quantitative remote sensing study indicates doubling of coastal erosion rate in past 50 yr along a segment of the Arctic coast of Alaska

A new quantitative coastal land gained-and-lost method uses image analysis of topographic maps and Landsat thematic mapper short-wave infrared data to document accelerated coastal land loss and thermokarst lake expansion and drainage. The data span 1955-2005 along the Beaufort Sea coast north of Teshekpuk Lake in the National Petroleum Reserve in Alaska. Some areas have undergone as much as 0.9 km of coastal erosion in the past 50 yr. Land loss attributed to coastal erosion more than doubled, from 0.48 km2 yr-1 during 1955-1985 to 1.08 km2 yr-1 during 1985-2005. Coastal erosion has breached thermokarst lakes, causing initial draining of the lakes followed by marine floodng. Although inland thermokarst lakes show some uniform expansion, lakes breached by coastal erosion display lake expansion several orders of magnitude greater than inland lakes. ?? 2007 The Geological Society of America.

Geology↗

USGS2014

Geologic history of Siletzia, a large igneous province in the Oregon and Washington Coast Range: Correlation to the geomagnetic polarity time scale and implications for a long-lived Yellowstone hotspot

Siletzia is a basaltic Paleocene and Eocene large igneous province in coastal Oregon, Washington, and southern Vancouver Island that was accreted to North America in the early Eocene. New U-Pb magmatic, detrital zircon, and 40 Ar/ 39 Ar ages constrained by detailed field mapping, global nannoplankton zones, and magnetic polarities allow correlation of the volcanics with the 2012 geologic time scale. The data show that Siletzia was rapidly erupted 56–49 Ma, during the Chron 25–22 plate reorganization in the northeast Pacific basin. Accretion was completed between 51 and 49 Ma in Oregon, based on CP11 (CP—Coccolith Paleogene zone) coccoliths in strata overlying onlapping continental sediments. Magmatism continued in the northern Oregon Coast Range until ca. 46 Ma with the emplacement of a regional sill complex during or shortly after accretion. Isotopic signatures similar to early Columbia River basalts, the great crustal thickness of Siletzia in Oregon, rapid eruption, and timing of accretion are consistent with offshore formation as an oceanic plateau. Approximately 8 m.y. after accretion, margin parallel extension of the forearc, emplacement of regional dike swarms, and renewed magmatism of the Tillamook episode peaked at 41.6 Ma (CP zone 14a; Chron 19r). We examine the origin of Siletzia and consider the possible role of a long-lived Yellowstone hotspot using the reconstruction in GPlates, an open source plate model. In most hotspot reference frames, the Yellowstone hotspot (YHS) is on or near an inferred northeast-striking Kula-Farallon and/or Resurrection-Farallon ridge between 60 and 50 Ma. In this configuration, the YHS could have provided a 56–49 Ma source on the Farallon plate for Siletzia, which accreted to North America by 50 Ma. A sister plateau, the Eocene basalt basement of the Yakutat terrane, now in Alaska, formed contemporaneously on the adjacent Kula (or Resurrection) plate and accreted to coastal British Columbia at about the same time. Following accretion of Siletzia, the leading edge of North America overrode the YHS ca. 42 Ma. The voluminous high-Ti basaltic to alkalic magmatism of the 42–35 Ma Tillamook episode and extension in the forearc may be related to the encounter with an active YHS. Clockwise rotation of western Oregon about a pole in the backarc has since moved the Tillamook center and underlying Siletzia northward ∼250 km from the probable hotspot track on North America. In the reference frames we examined, the YHS arrives in the backarc ∼5 m.y. too early to match the 17 Ma magmatic flare-up commonly attributed to the YHS. We suggest that interaction with the subducting slab may have delayed arrival of the plume beneath the backarc.

Oregon, Vancouver, Washington↗

USGS2012

Fault geometry and cumulative offsets in the central Coast Ranges, California: Evidence for northward increasing slip along the San Gregorio-San Simeon-Hosgri fault

Estimates of the dip, depth extent, and amount of cumulative displacement along the major faults in the central California Coast Ranges are controversial. We use detailed aeromagnetic data to estimate these parameters for the San Gregorio–San Simeon–Hosgri and other faults. The recently acquired aeromagnetic data provide an areally consistent data set that crosses the onshore-offshore transition without disruption, which is particularly important for the mostly offshore San Gregorio–San Simeon–Hosgri fault. Our modeling, constrained by exposed geology and in some cases, drill-hole and seismic-reflection data, indicates that the San Gregorio–San Simeon–Hosgri and Reliz-Rinconada faults dip steeply throughout the seismogenic crust. Deviations from steep dips may result from local fault interactions, transfer of slip between faults, or overprinting by transpression since the late Miocene. Given that such faults are consistent with predominantly strike-slip displacement, we correlate geophysical anomalies offset by these faults to estimate cumulative displacements. We find a northward increase in right-lateral displacement along the San Gregorio–San Simeon–Hosgri fault that is mimicked by Quaternary slip rates. Although overall slip rates have decreased over the lifetime of the fault, the pattern of slip has not changed. Northward increase in right-lateral displacement is balanced in part by slip added by faults, such as the Reliz-Rinconada, Oceanic–West Huasna, and (speculatively) Santa Ynez River faults to the east.

Lithosphere↗

USGS1957

Chapter 22: Environments and facies of existing bays on the central Texas coast

The estuaries and neritic waters along the central Texas coast are characterized by broad ranges of environmental factors, providing conditions favorable to temperate organisms in winter and tropical organisms in summer. Dredging in the coastal waters revealed a number of distinct faunal facies, the distribution of which appears to be controlled primarily by salinity. Characteristic assemblages are found in the following areas: closed bays, polyhaline bays, a highly saline lagoon, passes, beaches on the open Gulf, and shallow waters of the open gulf. In the closed bays three subfacies are recognized-one in the bay heads, one on the reefs, and one in the interreef areas; in the open gulf the assemblages living close to shore are differentiated from those found 2-4 miles off shore. In most stations each facies is characterized by an abundance of certain living forms. Dead shells and other skeletal parts are much more widely distributed, but many such strays may be recognized as transported elements by their rarity or by their eroded surfaces. Each group of organisms has one or more centers of maximum development in numbers of species. The Foraminifera, for example, attain their greatest development in the polyhaline bays and near the heads of passes, the ostracodes near the bay heads, mollusks in the polyhaline bays and in the Gulf, and diatoms under normal marine conditions in the Gulf. The reef assemblage of the closed bays is poor in numbers of species, but the individuals are so numerous that they form extensive deposits.

Texas↗

USGS2001

The variability of root cohesion as an influence on shallow landslide susceptibility in the Oregon Coast Range

Decades of quantitative measurement indicate that roots can mechanically reinforce shallow soils in forested landscapes. Forests, however, have variations in vegetation species and age which can dominate the local stability of landslide-initiation sites. To assess the influence of this variability on root cohesion we examined scarps of landslides triggered during large storms in February and November of 1996 in the Oregon Coast Range and hand-dug soil pits on stable ground. At 41 sites we estimated the cohesive reinforcement to soil due to roots by determining the tensile strength, species, depth, orientation, relative health, and the density of roots 1 mm in diameter within a measured soil area. We found that median lateral root cohesion ranges from 6.8–23.2 kPa in industrial forests with significant understory and deciduous vegetation to 25.6–94.3 kPa in natural forests dominated by coniferous vegetation. Lateral root cohesion in clearcuts is uniformly 10 kPa. Some 100-year-old industrial forests have species compositions, lateral root cohesion, and root diameters that more closely resemble 10-year-old clearcuts than natural forests. As such, the influence of root cohesion variability on landslide susceptibility cannot be determined solely from broad age classifications or extrapolated from the presence of one species of vegetation. Furthermore, the anthropogenic disturbance legacy modifies root cohesion for at least a century and should be considered when comparing contemporary landslide rates from industrial forests with geologic background rates.

Oregon↗

USGS1991

U–Pb geochronology of Late Cretaceous and early Tertiary plutons in the northern Coast Mountains batholith

U–Pb geochronologic studies demonstrate that steeply dipping, sheetlike tonalitic plutons along the western margin of the northern Coast Mountains batholith were emplaced between ~83 and ~57 (perhaps ~55) Ma. Less elongate tonalitic–granodioritic bodies in central portions of the batholith yield ages of 59–58 Ma, coeval with younger phases of the tonalitic sheets. Large granite–granodiorite bodies in central and eastern portions of the batholith were emplaced at 51–48 Ma. Trends in ages suggest that the tonalitic bodies generally become younger southeastward and that, at the latitude of Juneau, plutonism migrated northeastward across the batholith at ~0.9 km/Ma. Variations in the age, shape, location, and degree of fabric development among the various plutons indicate that Late Cretaceous – Paleocene tonalitic bodies were emplaced into a steeply dipping, dip-slip shear zone that was active along the western margin of the batholith. Postkinematic Eocene plutons were emplaced at shallow crustal levels. Inherited zircon components in these plutons range in age from mid-Paleozoic to Early Proterozoic and are coeval with detrital zircons in adjacent metasedimentary rocks. These old zircons, combined with evolved Nd isotopic signatures for most plutons, record assimilation of continental crustal or supracrustal rocks during the generation and (or) ascent of the plutons.

Alaska↗

USGS1989

Genetic variation in steelhead ( Salmo gairdneri ) from the north coast of Washington

Steelhead ( Salmo gairdneri ) collected from various sites in nine drainages in northwestern Washington were genetically characterized at 65 protein-coding loci by starch-gel electrophoresis. Genetic differentiation within and among drainages was not significant, and genetic variation among drainages was much less than that reported in British Columbia; these results may be the consequence of gene flow from hatchery stocks that have been released in Washington since the 1940's. Allele frequencies varied significantly among year-classes (hence, genetic characterization studies must include data from several year-classes), and also between hatchery fish (including a stock developed with local wild fish) and wild fish, indicating that few wild fish have been successfully and routinely included in hatchery brood stocks. Conservation of genetic diversity along the north coast of Washington should be facilitated by reducing the numbers of hatchery fish that spawn in streams and by including wild fish in hatchery brood stocks.

Washington↗