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At least 289 records · Page 16Linked to original sources
USGS2014

Mercury exposure associated with altered plasma thyroid hormones in the declining western pond turtle (Emys marmorata) from California mountain streams

Mercury (Hg) is a global threat to wildlife health that can impair many physiological processes. Mercury has well-documented endocrine activity; however, little work on the effects of Hg on the thyroid hormones triiodothyronine (T3) and thyroxine (T4) in aquatic wildlife exists despite the fact that it is a sensitive endpoint of contaminant exposure. An emerging body of evidence points to the toxicological susceptibility of aquatic reptiles to Hg exposure. We examined the endocrine disrupting potential of Hg in the western pond turtle (Emys marmorata), a long-lived reptile that is in decline throughout California and the Pacific Northwest. We measured total Hg (THg) concentrations in red blood cells (RBCs) and plasma T3 and T4 of turtles from several locations in California that have been impacted by historic gold mining. Across all turtles from all sites, the geometric mean and standard error THg concentration was 0.805 ± 0.025 μg/g dry weight. Sampling region and mass were the strongest determinants of RBC THg. Relationships between RBC THg and T3 and T4 were consistent with Hg-induced disruption of T4 deiodination, a mechanism of toxicity that may cause excess T4 levels and depressed concentrations of biologically active T3.

California↗
USGS1994

Mammal extinctions, body size, and paleotemperature

There is a general inverse relationship between the natural logarithm of tooth area (a body size indicator) of some fossil mammals and paleotemperature during approximately 2.9 million years of the early Eocene in the Bighorn Basin of northwest Wyoming. When mean temperatures became warmer, tooth areas tended to become smaller. During colder times, larger species predominated; these generally became larger or remained the same size. Paleotemperature trends also markedly affected patterns of local (and, perhaps, regional) extinction and immigration. New species appeared as immigrants during or near the hottest (smaller forms) and coldest (larger forms) intervals. Paleotemperature trend reversals commonly resulted in the ultimate extinction of both small forms (during cooling intervals) and larger forms (during warming intervals). These immigrations and extinctions mark faunal turnovers that were also modulated by sharp increases in sediment accumulation rate.

Proceedings of the National Academy of Sciences of↗
USGS2010

The Meteoritical Bulletin, No. 96, September 2009

The Meteoritical Bulletin No. 96 contains a total of 1590 newly approved meteorite names with their relevant data. These include 12 from specific locations within Africa, 76 from northwest Africa, 9 from the Americas, 13 from Asia, 1 from Australia, 2 from Europe, 950 from Antarctica recovered by the Chinese Antarctic Research Expedition (CHINARE), and 527 from the American Antarctic program (ANSMET). Among these meteorites are 4 falls, Almahata Sitta (Sudan), Sulagiri (India), Ash Creek (United States), and Maribo (Denmark). Almahata Sitta is an anomalous ureilite and is debris from asteroid 2008 TC3 and Maribo is a CM2 chondrite. Other highlights include a lunar meteorite, a CM1 chondrite, and an anomalous IVA iron. ?? The Meteoritical Society, 2009.

Meteoritics and Planetary Science↗
USGS2026

Long-term monotonic trends in water budget components in the contiguous United States: Insights from two hydrologic models

Characterizing changes to water availability for domestic, industrial, agricultural, and other uses is essential to support water management. To better quantify these changes, the U.S. Geological Survey and National Science Foundation National Center for Atmospheric Research produced two hydrologic models simulating water budget components from 1980 to 2021 over the contiguous United States (CONUS). Both hydrologic models were driven by a common atmospheric forcing dataset and aggregated to common spatial and temporal scales, which enables a novel evaluation of congruency between the models. We present annual and seasonal trends in six water budget components (precipitation, evapotranspiration, streamflow, groundwater recharge, soil saturation, and snow water equivalent) based on the Mann–Kendall test for monotonic trend and Theil-Sen slope estimate for the water year 1983–2021 period for ~86,000 catchments in CONUS. Additional components and metrics from our analysis pipeline are available in an associated published dataset, which contains more than 46 million trend results. The water budget trends showed broad agreement with prior observational and modeling studies that indicate increasing trends in the northeast and decreasing trends in southwestern CONUS. We found the seasonal variability in water budget trends was greatest in the southern, central, and northwest CONUS. These findings support integrated trend assessments when coupled with trends in water quality and use.

Contiguous United States↗
USGS1966

Exposure of basement rock on the continental slope of the Bering Sea

Profiles of repetitive seismic reflections reveal that the Bering continental slope, outer shelf, and rise overlay an acoustically reflective "basement" which extends at least 750 kilometers parallel to the trend of the slope. This acoustic basement is usually covered by several hundred meters of stratified sediments at the top and bottom of the slope; however, it is exposed in submarine canyons and flanking spurs along the main part of the slope for a distance of at least 550 kilometers northwest of the Pribilof Islands. The lithologic composition and the age of the rocks of the acoustic basement are not known. However, its probable seismic velocity of 3.1 to 3.7 kilometers per second suggests that it is composed of volcanic rocks or lithified sedimentary rocks or both. The regional geology suggests that the acoustic basement is the upper surface of folded late Mesozoic rocks which were locally intruded by granite and serpentine. The structure of the Bering slope, as deduced from the acoustic profiles, suggests that the surface of the basement has been monoclinically flexed and faulted between the shelf edge and the deep Aleutian Basin.

Alaska↗
USGS2004

Tectonic framework and Late Cenozoic tectonic history of the northern part of Cyprus: Implications for earthquake hazards and regional tectonics

Located near the triple junction of the African, Arabia, and Eurasian Plate, Cyprus has had an active and complex neotectonic history, which includes devastating historical earthquakes. Investigations into the tectonic framework of the northern part of Cyprus provide important insights into regional tectonism of the Eastern Mediterranean and Middle East. The northern part of Cyprus is divided into two tectono-stratigraphic terranes, the boundary of which is the Ovgos fault zone. In the Middle Miocene, the Ovgos fault zone was a marine platform margin, which separated open-marine platform carbonates from deep-marine turbidites. Transpressive movement along easterly and northeasterly trending structures dominated the Late Miocene; deposition and preservation of Messinian evaporites occurred in grabens at intersections of these trends. N–S compression began in the Early Pliocene and produced contractional tectonism along east–west trends, including major thrusting of allochthonous rocks in the Kyrenia Range. Quaternary deformation has been dominated by strike-slip faults along northeast and northwest trends; movement during the Pleistocene occurred on several of these faults; Holocene movement is documented on one of these faults. A seismic hazard is implied for the Nicosia area because its proximity to the Quaternary faults. Since the Miocene, Cyprus has been continuously uplifted, but the tectonic setting is controversial, as some researchers invoke a subduction zone setting and others ascribe to a regime of strike-slip tectonics. Our neotectonic framework is consistent with a restraining bend model for Cyprus in a regional strike-slip regime.

Journal of Asian Earth Sciences↗
USGS1977

Further paleomagnetic results for the San Juan volcanic field of southern Colorado

Combining paleomagnetic data for 17 new sites from the northwest portion of the (Oligocene) San Juan volcanic field of southern Colorado with data for 29 sites previously published yields a paleomagnetic pole at 85°N, 114°E (with a 95% confidence circle of 7.5° radius). A further combination of the San Juan data with the results of other studies on rocks of Oligocene age from tectonically stable parts of North America gives a mid-Tertiary reference pole located at 81°N, 132.5°E, with a confidence circle of approximately 4°. Mid-Tertiary paleomagnetic poles for the western edge of the continent diverge markedly from this reference pole.

Colorado↗
USGS2006

North Kona slump: Submarine flank failure during the early(?) tholeiitic shield stage of Hualalai Volcano

The North Kona slump is an elliptical region, about 20 by 60 km (1000-km 2 area), of multiple, geometrically intricate benches and scarps, mostly at water depths of 2000–4500 m, on the west flank of Hualalai Volcano. Two dives up steep scarps in the slump area were made in September 2001, using the ROV Kaiko of the Japan Marine Science and Technology Center (JAMSTEC), as part of a collaborative Japan–USA project to improve understanding of the submarine flanks of Hawaiian volcanoes. Both dives, at water depths of 2700–4000 m, encountered pillow lavas draping the scarp-and-bench slopes. Intact to only slightly broken pillow lobes and cylinders that are downward elongate dominate on the steepest mid-sections of scarps, while more equant and spherical pillow shapes are common near the tops and bases of scarps and locally protrude through cover of muddy sediment on bench flats. Notably absent are subaerially erupted Hualalai lava flows, interbedded hyaloclastite pillow breccia, and/or coastal sandy sediment that might have accumulated downslope from an active coastline. The general structure of the North Kona flank is interpreted as an intricate assemblage of downdropped lenticular blocks, bounded by steeply dipping normal faults. The undisturbed pillow-lava drape indicates that slumping occurred during shield-stage tholeiitic volcanism. All analyzed samples of the pillow-lava drape are tholeiite, similar to published analyses from the submarine northwest rift zone of Hualālai. Relatively low sulfur (330–600 ppm) and water (0.18–0.47 wt.%) contents of glass rinds suggest that the eruptive sources were in shallow water, perhaps 500–1000-m depth. In contrast, saturation pressures calculated from carbon dioxide concentrations (100–190 ppm) indicate deeper equilibration, at or near sample sites at water depths of − 3900 to − 2800 m. Either vents close to the sample sites erupted mixtures of undegassed and degassed magmas, or volatiles were resorbed from vesicles during flowage downslope after eruption in shallow water. The glass volatile compositions suggest that the tholeiitic lavas that drape the slump blocks were erupted either (1) early during shield-stage tholeiitic volcanism prior to emergence of a large subaerial edifice, or alternatively (2) from submarine radial vents during subaerial shield-building. Because no radial vents have been documented on land or underwater for the unbuttressed flanks of any Hawaii volcano, alternative (1) is favored. In comparison to other well-documented Hawaiian slumps and landslides, North Kona structures suggest a more incipient slump event, with smaller down-slope motions and lateral displacements.

Hawaii↗
USGS2005

Elemental content of lichens of the Point Reyes Peninsula, northern California

The Point Reyes peninsula in northern California is about 45 km northwest of San Francisco and occasionally receives air masses from the city contributing to haze and lowered visibility. Although gaseous pollutants are not a problem, fine particulates containing carbon and other elements are measurable at the park. In this study, five lichen species were sampled along a 40-km linear transect from southeast to northwest from the town of Bolinas at the southern end of the peninsula. Elevated levels of Na and S and the Na/S ratio at localities nearer the ocean confirmed there is a definite marine aerosol influence on lichen elemental content. Elevated potassium and mercury concentrations were also found at high elevation sites that intercept fog. However, arsenic and lead were found to decrease with distance from Bolinas along the transect, suggesting these two elements originate in the fine particulate haze that enters the park from San Francisco. Concentrations of elements were not at enriched levels for other lichen species. A possible local influence of roads on element content needs further study.

California↗
USGS1978

Strain in southern California: Measured uniaxial north-south regional contraction

The plate tectonics model of the Pacific moving northwest relative to North America implies that the regional strain in California should be simple shear across a vertical plane striking N45°W or equivalently equal parts of north-south contraction and east-west extension. Measurements of the strain accumulation at seven separate sites in southern California in the interval 1972 through 1978 indicate a remarkably consistent uniaxial north-south contraction of about 0.3 part per million per year; the expected east-west extension is absent. It is not clear whether the period from 1972 through 1978 is anomalous or whether the secular strain in southern California is indeed a uniaxial north-south contraction.

California↗
USGS2020

Plate boundary localization, slip-rates and rupture segmentation of the Queen Charlotte Fault based on submarine tectonic geomorphology

Linking fault behavior over many earthquake cycles to individual earthquake behavior is a primary goal in tectonic geomorphology, particularly across an entire plate boundary. Here, we examine the 1150-km-long, right-lateral Queen Charlotte-Fairweather fault system using comprehensive multibeam bathymetry data acquired along the Queen Charlotte Fault (QCF) offshore southeastern Alaska and western British Columbia. Fine-scale analysis of tectonic geomorphology allowed us to identify and reconstruct 184 strike-slip piercing points over a 630 km stretch of the QCF. Age constraints from glacial recession and offshore sedimentation patterns yield a consistent slip-rate of ∼50–57 mm/yr since ∼17–12 ka, the fastest rate for a continent-ocean strike-slip fault on Earth. These slip-rates equal or exceed estimates of Pacific-North America (PA-NA) relative motion from global plate reconstructions, indicating that PA-NA motion is highly localized. The QCF cuts the seafloor along a narrow and unusually straight trace for its entire length and multiple fault traces are observed only at local step-overs. The geometry and behavior of the QCF over many earthquake cycles is simple and typical of mature faults with relatively homogeneous stress fields. Since the QCF is the primary PA-NA plate boundary, we used the trace of the QCF to define the small circle path for relative plate motion and computed the associated Euler pole. Predicted along-strike obliquity variations based on the new pole agree with observed tectonic geomorphology and suggest that previous global plate reconstructions overestimated the degree of oblique convergence along the QCF. We also find that subtle, long-wavelength (75–150 km) bends and discrete step-overs appear to define the endpoints of M>7 earthquakes, suggesting that obliquity and resultant fault geometry may control rupture segmentation and asperity development. Lastly, the agreement between predicted obliquity and tectonic geomorphology along the entire length of QCF compelled a reevaluation of regional tectonic models. In the north, the eastern Yakatat Terrane appears to be translating northwest with the Pacific plate, and slip transferred from the QCF to the Fairweather Fault results in ∼20 mm/yr of convergence along the southern St. Elias mountains. In the south, we predict a reduced rate of convergence along the QCF west of Haida Gwaii (∼5–6 mm/yr of shortening, on average) relative to previous studies. Our results support a model for transpression and strike-slip partitioning along the edge of a hot and weak Pacific Plate, leading to crustal thickening and growth of the Queen Charlotte Terrace to the west of Haida Gwaii.

Alaska, British Columbia↗
USGS2006

Survival estimates for Florida manatees from the photo-identification of individuals

We estimated adult survival probabilities for the endangered Florida manatee (Trichechus manatus latirostris) in four regional populations using photo-identification data and open-population capture-recapture statistical models. The mean annual adult survival probability over the most recent 10-yr period of available estimates was as follows: Northwest - 0.956 (SE 0.007), Upper St. Johns River - 0.960 (0.011), Atlantic Coast - 0.937 (0.008), and Southwest - 0.908 (0.019). Estimates of temporal variance independent of sampling error, calculated from the survival estimates, indicated constant survival in the Upper St. Johns River, true temporal variability in the Northwest and Atlantic Coast, and large sampling variability obscuring estimates for the Southwest. Calf and subadult survival probabilities were estimated for the Upper St. Johns River from the only available data for known-aged individuals: 0.810 (95% CI 0.727-0.873) for 1st year calves, 0.915 (0.827-0.960) for 2nd year calves, and 0.969 (0.946-0.982) for manatee 3 yr or older. These estimates of survival probabilities and temporal variance, in conjunction with estimates of reproduction probabilities from photoidentification data can be used to model manatee population dynamics, estimate population growth rates, and provide an integrated measure of regional status.

Marine Mammal Science↗
USGS2001

Geochemical evidence for mudstone as the possible major oil source rock in the Jurassic Turpan Basin, Northwest China

Geologists and geochemists have debated whether hydrocarbons from Jurassic coal measures are derived from the mudstones or the coals themselves. This paper identifies mudstones as the possible major source rock of hydrocarbons in the Jurassic basins in Northwest China. The Turpan Basin is used as a representative model. Mudstones in the Middle-Lower Jurassic are very well developed in the basin and have an average genetic potential from 2 to 4 mg/g. The vitrinite reflectance of the source rocks ranges from 0.6 to 1.3%, exhibiting sufficient thermal maturity to generate oil and gas. Biomarkers in crude oils from the basin are similar to those in mudstones from the coal-bearing strata, with a low tricyclic terpane (cheilanthane) content, a relatively high content of low carbon number (less than C22) tricyclic terpanes and a low content of high carbon number tricyclic terpanes, relatively high ratios of Ts/Tm, and C29 Ts/17?? (H)-C29 norhopane, and low ratios of Tm/17?? (H)-C30 hopane and 17?? (H)-C31 homohopane/17?? (H)-C30 hopane. These characteristics and the distribution of steranes and terpanes in the crude oil and mudstone differ significantly from those of the Jurassic coals and carbonaceous shales of the basin, indicating mudstone is possibly the major source rock of the oils in the Turpan Basin. ?? 2001 Elsevier Science Ltd. All rights reserved.

Organic Geochemistry↗
USGS2016

Reevaluating the age of the Walden Creek Group and the kinematic evolution of the western Blue Ridge, southern Appalachians

An integrated synthesis of existing datasets (detailed geologic mapping, geochronologic, paleontologic, geophysical) with new paleontologic and geochemical investigations of rocks previously interpreted as part of the Neoproterozoic Walden Creek Group in southeastern Tennessee suggest a necessary reevaluation of the kinematics and structural architecture of the Blue Ridge Foothills. The western Blue Ridge of Tennessee, North Carolina, and Georgia is composed of numerous northwest-directed early and late Paleozoic thrust sheets, which record pronounced variation in stratigraphic/structural architecture and timing of metamorphism. The detailed spatial, temporal, and kinematic relationships of these rocks have remained controversial. Two fault blocks that are structurally isolated between the Great Smoky and Miller Cove-Greenbrier thrust sheets, here designated the Maggies Mill and Citico thrust sheets, contain Late Ordovician-Devonian conodonts and stable isotope chemostratigraphic signatures consistent with a mid-Paleozoic age. Geochemical and paleontological analyses of Walden Creek Group rocks northwest and southeast of these two thrust sheets, however, are more consistent with a Late Neoproterozoic (550–545 Ma) depositional age. Consequently, the structural juxtaposition of mid-Paleozoic rocks within a demonstrably Neoproterozoic-Cambrian succession between the Great Smoky and Miller Cove-Greenbrier thrust sheets suggests that a simple foreland-propagating thrust sequence model is not applicable in the Blue Ridge Foothills. We propose that these younger rocks were deposited landward of the Ocoee Supergroup, and were subsequently plucked from the Great Smoky fault footwall as a horse, and breached through the Great Smoky thrust sheet during Alleghanian emplacement of that structure.

North Carolina, Tennessee↗
USGS1983

Holocene history of the estuarine area surrounding Portage, Alaska, as recorded in a 93 m core

A 93 m core obtained at Portage, Alaska records four prograding cycles of estuarine deposition for the past 8230 ± 100 years. Analyses of texture, mineralogy, paleontology, and sedimentary structures enable definition of eight lithologic units. Mineralogic studies show that past and present sedimentation at Portage has been largely mud and sand from the Susitna River on the northwest side of Cook Inlet. Six radiocarbon dates from concentrated organic debris in the core and on the surface enable determination of sedimentation rates for four intervals and show rates to be higher and to vary more at depth than rates nearer the surface. The glacier-carved Turnagain Arm fiord has been receiving sediment for at least the past 14 000 years, as estimated by extrapolation of calculated sedimentation rates to the thickness of unconsolidated sediment drilled at Portage, which totals approximately 300 m. Presently, deposition is accomplished "instantly" as the result of tectonic subsidence and compaction of sediment caused by periodic earthquakes, in combination with a turbid estuarine system.

Alaska↗
USGS2018

Effects of land use on summer thermal regimes in critical salmonid habitats of the Pacific Northwest

The effect of climate change on stream temperature regimes is of significant concern to natural resource managers focused on protecting cold-water-dependent species. Nevertheless, understanding of how human land-use activities may act to exacerbate the effects of climate change on stream temperature regimes is limited. Using extensive stream temperature data with high-resolution climate and habitat data, we quantified how land management activities are related to summer stream temperatures across the Pacific Northwest, USA. We then described the distribution of land management practices influencing summer thermal regimes relative to the distribution of salmonid fish species of conservation concern. After accounting for climatic and geophysical variation, we detected a strong relationship between livestock grazing and summer thermal regimes. Maximum, average, and diel variation in water temperature was greater where livestock grazing was present. Livestock grazing was widespread, occurring in 43%–100% of sites supporting salmonid species of conservation concern. Thus, current land management practices may be intensifying the effects of ongoing climate change in freshwater habitats, acting to further threaten cold-water fishes of conservation concern.

Washington, Oregon, Idaho, Montana↗
USGS2008

Murres, capelin and ocean climate: Inter-annual associations across a decadal shift

To ensure energy demands for reproduction are met, it is essential that marine birds breed during periods of peak food availability. We examined associations of the breeding chronology of common murres (Uria aalge) with the timing of the inshore arrival of their primary prey, capelin (Mallotus villosus) from 1980 to 2006 across a period of pervasive change in the Northwest Atlantic ecosystem. We also assessed the influence of ocean temperature and the North Atlantic Oscillation (NAO; an index of winter climate and oceanography) on these interactions. We found a lagged linear relationship between variations in murre breeding chronology and the timing of capelin arrival in the previous year. On a decadal level, we found a non-linear threshold relationship between ocean temperature and the timing of capelin arrival and murre breeding. Centennially anomalous cold water temperatures in 1991 generated a marked shift in the timing of capelin spawning inshore and murre breeding, delaying both by more than 2 weeks. By the mid-1990s, ocean temperatures returned to pre-perturbation levels, whereas the temporal breeding responses of capelin and murres were delayed for a decade or more. Oceanographic conditions (temperature, NAO) were poor predictors of the timing of capelin arrival inshore in the current year compared to the previous one. Our findings suggest that knowledge of the timing of capelin availability in the previous year provides a robust cue for the long-lived murres, allowing them to achieve temporal overlap between breeding and peak capelin availability. ?? Springer Science+Business Media B.V. 2008.

Environmental Monitoring and Assessment↗
USGS2014

The shallow stratigraphy and sand resources offshore from Cat Island, Mississippi

In collaboration with the U.S. Army Corps of Engineers, scientists from the U.S. Geological Survey (USGS) St. Petersburg Coastal and Marine Science Center collected over 487 line kilometers (> 300 miles) of high-resolution geophysical data around Cat Island, Mississippi, to improve understanding of the island's geologic evolution and identify potential sand resources for coastal restoration. In addition, 40 vibracores were collected on and around the island, generating more than 350 samples for grain-size analysis. The results indicate that the geologic evolution of Cat Island has been influenced by deltaic, lagoonal/estuarine, tidal, and oceanographic processes, resulting in a stratigraphic record that is quite complex. The region north of the island is dominated by lagoonal/estuarine deposition, whereas the region south of the island is dominated by deltaic and tidal deposition. In general, the veneer of modern sediment surrounding the island is composed of newly deposited sediment and highly reworked relict sediments. The region east of the island shows the interplay of antecedent barrier-island change with delta development despite a significant ravinement of sediments. The data show from little to no modern sediment east of the island, exposing relict sediments at the seafloor. Finally, the data reveal four subaqueous sand units around the island. Two of the units are northwest of the modern island and one is southwest. Given the dominant, westward, longshore transport along the Mississippi and Alabama barrier islands, the geographic location of these three units suggests that they do not contribute to the modern sediment budget of Cat Island. The last unit is directly east of the island and represents the antecedent island platform that has supplied sand over geologic time for creation of the spits that form the eastern shoreline. Because of its location east of the island, the antecedent island unit may still supply sediment to the island today.

Mississippi↗