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At least 1,027 records · Page 57Linked to original sources
USGS1984

Effects of the herbicide glyphosate on avian community structure in the Oregon coast range

A study was conducted on vegetative changes induced by the herbicide glyphosate, and the resultant habitat use of birds nesting on two clearcuts in western Oregon. About 23 percent of total plant cover was initially damaged by aerial application of glyphosate. Most measures of vegetation on the treated site decreased relative to the untreated site 1 year after glyphosate application. By 2 years post-spray, vegetation on the treated site had recovered to near pre-spray status. No difference in density of the bird community was evident between treated and untreated sites during all years of study although individual species densities were modified. Several bird species decreased their use of shrub cover, and increased their use of deciduous trees 1 year after treatment. By 2 years post-spray, many species had returned to pre-spray use of most measured habitat components. Results indicated that application of glyphosate can modify the density and habitat use of birds.

Forest Science↗
USGS1994

Winter movements and spring migration of American woodcock along the Atlantic coast

Radio transmitters were attached to American Woodcock (scolopax minor) at three Atlantic coastal sites to monitor winter movements and spring departure dates from Georgia (1982-1984, 1989-1991), South Carolina (1988-1989), and Virginia (1991-1992). There was no evidence of temperature, sex, or age-dependent migration dates. Migration was coincident with the full moon in February and the passage of weather fronts close to this time.

The Wilson Bulletin↗
USGS1994

Diurnal habitat use of American woodcock wintering along the Atlantic coast

The long-term decline of the American woodcock (Scolopax minor) population led us to investigate diurnal habitat use with radiotelemetry on the wintering grounds. Sites included the coastal plain of Georgia (1989-1991), South Carolina (1988-1989), and Virginia (1991-1992). Habitat use was not explained by age, sex, or date during the winter, but individuals used habitat differently (P < 0.05). Only shrubland was preferred at all sites in all years. Pine plantations of various ages were used according to availability, but usually less often than expected, while bottomland hardwoods and pine - hardwoods were used more often than expected.

Canadian Journal of Zoology↗
USGS2009

Movement triggers and remediation in a fracture-dominated translational landslide at the Oregon coast

The Johnson Creek landslide is a translational slide in seaward dipping Miocene siltstone and sandstone (Astoria Formation) and an overlying Quaternary marine terrace deposit. The slide terminates in a sea cliff and has a hummocky to nearly horizontal ground surface. The basal slide plane, however, slopes subparallel to the dip of the Miocene rocks, except beneath the back-tilted toe blocks where it curves upward. The siltstone and sandstone have low estimated permeability but cores and field mapping reveal an extensive fracture system within the slide mass. The slide mainly moves in response to groundwater pressure and coastal erosion of the toe. Limit-equilibrium stability analyses indicate that 3 m of erosion at the toe would destabilize the slide for most of the wet season, although no movement could be directly attributed to erosion in the 5 years of observation. Intense rainfall events raise pore-water pressure throughout the slide in the form of pulses of water pressure traveling from the headwall graben down the axis of the slide at rates of 1.4-2.5 m/hr in the upper part, and 3.5 m/hr to virtually instantaneous in the middle part. Infiltration of meteoric water was only ~50 mm/hr. Slope of the water table exceeds topographic slope from the head to the toe of the slide, so infiltration was too slow to directly raise head in 90 percent of the slide mass where the saturated zone is deeper than a few meters. Only at the headwall graben was the saturated zone shallow enough for rainfall events to trigger pulses of water pressure through the entire saturated zone. When a pressure pulse reached the threshold pressure for movement in the central part of the slide, the whole slide began slow, creeping movement. As head became larger and larger than the threshold for movement in more of the slide mass, movement accelerated and differential displacement between internal slide blocks became more pronounced. These findings suggest that dewatering the shallowest part of the saturated zone in this type of slide will stop these rapid pressure pulses, thereby stopping or greatly reducing seasonal movement. If slides are also subject to continual removal of material from the toe, especially where there are back-tilted toe blocks, then some type of buttress or tied-back shear pile wall may be the only effective long term remediation.

Oregon↗
USGS1987

Nature and distribution of potential heavy-mineral resources offshore of the Atlantic Coast of the United States.

The US is dependent on foreign imports of placer heavy minerals for a majority of its ilmenite and rutile, and virtually all of its monazite requirements. Although sand deposits in the SE US are important domestic sources of these heavy minerals (HM) and a number of other less well-known heavy-mineral species, global onshore reserves of placer minerals may fall short of demand in as few as 20 years. Insofar as they are important commodities for the future, offshore HM placers will become more important, but much research on them remains to be done. Results of recent offshore studies, based on surficial grab samples, indicate an average of about 2 weight percent HM in surficial Atlantic Continental Shelf (ACS) sediments, in strong contrast with previous estimates of an average of 0.16% HM. Although provocative, the information from these grab samples does not include the thickness of the HM deposits and thus their volume and tonnage cannot be estimated.-from Author

Marine Mining↗
USGS1991

Paleogeographic implications of an erosional remnant of Paleogene rocks southwest of the Sur-Nacimiento Fault Zone, southern Coast Ranges, California

A small tract of heretofore-unrecognized Paleogene rocks lies about 30 km northeast of Santa Maria and 1 km southwest of the Sur-Nacimiento fault zone near upper Pine Creek. This poorly exposed assemblage of rocks is less than 50 m thick, lies unconformably on regionally distributed Upper Cretaceous submarine-fan deposits, and consists of three units: fossiliferous lower Eocene mudstone, Oligocene(?) conglomerate, and basaltic andesite that has a radiometric age of 26.6 ?? 0.5 Ma. Both the sedimentary and igneous constituents in the Paleogene sequence are unlike those of known sequences on either side of the Sur-Nacimiento fault zone. The Paleogene sedimentary rocks near upper Pine Creek presumably are remnants of formerly widespread early Eocene bathyal deposits and locally distributed Oligocene(?) fluvial deposits southwest of the fault zone. The 26.6 Ma basaltic andesite, however, may not have extended much beyond its present outcrops. An episode of Oligocene(?) displacement is required by the contrast in thicknesses, depositional patterns, and paleobathymetry of the juxtaposed rock sequences. -from Authors

Geological Society of America Bulletin↗
USGS2006

Sedimentary deposits of the 26 December 2004 tsunami on the northwest coast of Aceh, Indonesia

The 2004 Sumatra-Andaman tsunami flooded coastal northern Sumatra to a depth of over 20 m, deposited a discontinuous sheet of sand up to 80 cm thick, and left mud up to 5 km inland. In most places the sand sheet is normally graded, and in some it contains complex internal stratigraphy. Structures within the sand sheet may record the passage of up to 3 individual waves. We studied the 2004 tsunami deposits in detail along a flow-parallel transect about 400 m long, 16 km southwest of Banda Aceh. Near the shore along this transect, the deposit is thin or absent. Between 50 and 400 m inland it ranges in thickness from 5 to 20 cm. The main trend in thickness is a tendency to thicken by filling low spots, most dramatically at pre-existing stream channels. Deposition generally attended inundation - along the transect, the tsunami deposited sand to within about 40 m of the inundation limit. Although the tsunami deposit contains primarily material indistinguishable from material found on the beach one month after the event, it also contains grain sizes and compositions unavailable on the current beach. Along the transect we studied, these grains become increasingly dominant both landward and upward in the deposit; possibly some landward source of sediment was exposed and exploited by the passage of the waves. The deposit also contains the unabraded shells of subtidal marine organisms, suggesting that at least part of the deposit came from offshore. Grain sizes within the deposit tend to fine upward and landward, although individual units within the deposit appear massive, or show reverse grading. Sorting becomes better landward, although the most landward sites generally become poorly sorted from the inclusion of soil clasts. These sites commonly show interlayering of sandy units and soil clast units. Deposits from the 2004 tsunami in Sumatra demonstrate the complex nature of the deposits of large tsunamis. Unlike the deposits of smaller tsunamis, internal stratigraphy is complex, and will require some effort to understand. The Sumatra deposits also show the contribution of multiple sediment sources, each of which has its own composition and grain size. Such complexity may allow more accurate modeling of flow depth and flow velocity for paleotsunamis, if an understanding of how tsunami hydraulics affect sedimentation can be established. Copyright ?? The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences; TERRAPUB.

Earth, Planets and Space↗
USGS2007

Temporal variability of submarine groundwater discharge: Assessments via radon and seep meters, the southern carmel coast, Israel

Seep meter data from Dor Bay, Israel, showed a steady decrease in submarine groundwater discharge (SGD) rates between March and July 2006 (averages of 34, 10.4 and 1.5 cm d-1 in March, May and July, respectively), while estimates based on radon time series showed remarkably uniform averages (8 cm d-1). The May seep meter data show a rough positive correlation with sea level, unlike the negative correlation shown by the Rn-calculated rates. Smaller-size meters, deployed in July adjacent to the regular-size ones, showed significantly higher rates (10 cm d-1), which negatively correlated with salinity. It is suggested that the decreased rates documented by the seep meters are the result of an increased shallow seawater recharge in the bay (due to decreasing hydraulic gradients). This is not captured by the radon, since recharging water is radon-poor. The positive correlation of discharge with sea level is due to increased seawater recycling in times of high sea stand. Copyright ?? 2007 IAHS Press.

Conference Paper↗
USGS2009

NOAA/West coast and Alaska Tsunami warning center Atlantic Ocean response criteria

West Coast/Alaska Tsunami Warning Center (WCATWC) response criteria for earthquakesoccurring in the Atlantic and Caribbean basins are presented. Initial warning center decisions are based on an earthquake's location, magnitude, depth, distance from coastal locations, and precomputed threat estimates based on tsunami models computed from similar events. The new criteria will help limit the geographical extent of warnings and advisories to threatened regions, and complement the new operational tsunami product suite. Criteria are set for tsunamis generated by earthquakes, which are by far the main cause of tsunami generation (either directly through sea floor displacement or indirectly by triggering of sub-sea landslides).The new criteria require development of a threat data base which sets warning or advisory zones based on location, magnitude, and pre-computed tsunami models. The models determine coastal tsunami amplitudes based on likely tsunami source parameters for a given event. Based on the computed amplitude, warning and advisory zones are pre-set.

Science of Tsunami Hazards↗
USGS2011

Zircon U-Pb age of the Pescadero felsite: A late Cretaceous igneous event in the forearc, west-central California Coast Ranges

Downstream grain-size fining in stratigraphy is driven primarily by selective deposition of sediment, and the long-term efficiency of this process is determined by: (1) the magnitude and characteristics of the input sediment supply; (2) the spatial distribution of subsidence rate, which creates accommodation for sediment preservation; and (3) the dynamics of sediment transport and deposition. A key challenge is to determine how these first two factors control the caliber and spatial distribution of deposits over time scales of 10 4 –10 6 yr without incorporating sediment transport details that are largely unknowable for time-averaged stratigraphy in the geological past. We address this using grain-size data collected from fluvial conglomerates in the Eocene Pobla Basin, Spanish Pyrenees, a synorogenic basin where the timing of sediment deposition is well-constrained; the sediment budget is closed; and good exposure enables time lines within stratigraphy to be picked out unambiguously. For successive stratigraphic horizons, downstream trends in grain size and composition are derived for basin-filling sediment-routing systems with length scales of 6 and 40 km, respectively. Our data show that the rate of grain-size fining varies over time and with system length and can be linked to changes in source area. These results are contrasted with grain-size data from the Antist Group, a 60-km-long Oligocene system that mantles the Southern Pyrenees, where very slow rates of grain-size fining on the wedge top of this fold-and-thrust belt are observed. We apply a self-similarity–based selective deposition model to quantify the competing controls of tectonic subsidence and sediment supply on derived grain-size trends, and model results are compared with independent constraints on the Eocene–Oligocene evolution of the Pyrenees. Our results suggest that it is now possible to invert time-averaged grain-size trends in stratigraphy to gain quantitative information on the geological boundary conditions governing the evolution of sedimentary basins.

Geological Society of America Bulletin↗