Search Results

The direct measurement of the ratio of cosmogenic 10Be (T12= 1.5 Ma">T12= 1.5 Ma) to stable terrigenously sourced 9Be in deep seawater or marine deposits can be used to trace water mass movements and to quantify the incorporation of trace metals into the deep sea. In...

The pore structure of Salem limestone is investigated, and conclusions regarding the effect of the pore geometry on modeling moisture and contaminant transport are discussed based on thin section petrography, scanning electron microscopy, mercury intrusion porosimetry, and nitrogen adsorption analyses. These investigations are compared to and shown to compliment permeability...

Several impure dolomitic limestone beds in an outcrop of the latest Archean Wittenoom Dolomite (Hamersley Group, Western Australia) are polygonally cracked. The cracks appear to be sub-aerial desiccation features, suggesting that the known area of shallow water and locally emergent conditions extended from the far eastern part of the basin...

Evidence of cryptic alteration and correlations among K, Ba, and LREE concentrations indicate that a post-cumulus, low-density aqueous fluid phase significantly modified the trace-element contents of samples from Anorthosite zones I and II of the Stillwater Complex, Montana. Concentrations of Ba, Ca, Co, Cr, Cu, Fe, Hf, K, Li, Mg,...

Small constructional volcanic landforms and very fresh-looking lava flows are present along one of the inferred active strike-slip faults that connect two small spreading centers (A and B) in the western portion of the Siqueiros transform domain. The most primitive lavas (picritic and olivine-phyric basalts), exclusively recovered from the young-looking...

A suite of salt-marsh peat samples from four sites along the coast of Maine (Wells, Phippsburg, Gouldsboro, and Machiasport) has been analyzed using high-precision techniques to determine local relative sea-level trends and to evaluate proposed along-coast warping. A spatially variable set of relative sea-level records in Maine would have important...

Improvements in the field sampling, preservation, and determination of trace metals in natural waters have made many analyses more reliable and less affected by contamination. The speciation of trace metals, however, remains controversial. Chemical model speciation calculations do not necessarily agree with voltammetric, ion exchange, potentiometric, or other analytical speciation...

Nonlinear regression is useful in ground-water flow parameter estimation, but problems of parameter insensitivity and correlation often exist given commonly available hydraulic-head and head-dependent flow (for example, stream and lake gain or loss) observations. To address this problem, advective-transport observations are added to the ground-water flow, parameter-estimation model MODFLOWP using...

Stream flow for 67 years was simulated for Coon Creek at Coon Valley, Wisconsin, for three conditions in the drainage basin: (1) conditions in the 1930s; (2) conditions in the 1970s, excluding flood-detention reservoirs; and (3) conditions in the 1970s, including flood-detention reservoirs. These simulations showed that the changes in...

The Colorado Plateau is a large crustal block in the southwestern United States that has been raised intact nearly 2 km above sea level since Cretaceous marine sediments were deposited on its surface. Controversy exists concerning the thickness of the plateau crust and the source of its buoyancy. Interpretations of...

I used replicated 37.8 1 aquaria in a factorial design (four densities of zebra mussel, Dreissena polymorpha; two hydrologic regimes) to determine if the survival or growth of juvenile fathead minnows (Pimephales promelas) was affected by the density of zebra mussel or by the retention time of...

Four box cores and one piston core show that Holocene sedimentation on the southern Canada Abyssal Plain for the last 8010 ± 120 yr has consisted of a continuing rain of pelagic organic and ice-rafted clastic sediment with a net accumulation rate during...

We developed and evaluated a surgical procedure for implanting intra-abdominal radiotransmitters with external whip antennas in captive mallards (Anas platyrhynchos). Transmitters were implanted in the abdominal cavity and the antennas exited through the caudal abdominal wall and skin. Birds with implanted transmitters developed mild to moderate localized air sac reactions....

We find that foreshocks provide clear evidence for an extended nucleation process before some earthquakes. In this study, we examine in detail the evolution of six California foreshock sequences, the 1986 Mount Lewis (ML = 5.5), the 1986 Chalfant (ML = 6.4), the 1986 Stone Canyon (ML = 4.7), the 1990 Upland (ML =...

Differential motion across the central Cascadia subduction boundary in Washington results in a complex pattern of folds and faults within the shelf and onshore parts of the accretionary margin. Faults and folds above a coastal, north-northwest–trending thrust system provide evidence of ongoing subduction-related...

Pre-recorded vocalizations of great horned owls (Bubo virginianus) broadcast into predominantly wooded habitat along roadside survey routes resulted in as many detections of resident red-shouldered hawks (Buteo lineatus) and Cooper's hawks (Accipiter cooperii) as broadcasts of each conspecific calls. Survey results for 3 species, expressed as average number of contacts/route,...

The Pelona, Orocopia, and Rand schists of southern California and southwestern Arizona are thought to have formed in either the same east-dipping subduction zone as the Franciscan complex or in a southwest-dipping subduction zone related to collision of an outboard continental fragment with...

A two-step nonlinear and linear inversion is carried out to map the lateral heterogeneity beneath North America using surface wave data. The lateral resolution for most areas of the model is of the order of several hundred kilometers. The most obvious feature in the tomographic images is the rapid transition...

Intermediate-depth seismic reflection profile across Crater Flat and Yucca Mountain is obtained. The aim of the seismic profiling are discrimination the subsurface geometry of faults and imaging of the boundary between the pre-Tertiary sedimentary strata and the Miocene volcanic rocks of Yucca Mountain. Of major interest is the existence and...

Linear alkylbenzenes (LABs) are sensitive source-specific tracers of sewage inputs to the marine environment. Because they are highly particle reactive and nonspecifically sorbed to organic matter, LABs are potential tracers of the transport of both sludge-derived organic matter and other low solubility hydrophobic contaminants (e.g., PCBs and PAHs); sediment trap...

Recent trails formed by soldier fly larvae (Díptera: Stratiomyidae) were examined in a shallow pond in the floodplain of a braided river in Jujuy Province, northwestern Argentina. Collected specimens were identified as Stratiomys convexa van der Wulp. Simple, irregularly meandering trails were produced across the surface of a muddy‐silty substrate. Since soldier...

Water recirculating systems for fish culture are potentially desirable for conserving water and reducing heating requirements, maximizing production of fish under water and space limitations, minimizing effluent problems, and maintaining better control over environmental factors. A semiclosed recirculating‐water system for intensive culture of rainbow trout Oncorhynchus mykiss is described. The system used...

Dolostones interbedded with Upper Permian evaporites at the base of the Northern Calcareous Alps contain abundant authigenic K-feldspar. Two petrographically, structurally, and isotopically distinct generations of K-feldspar can be distinguished: crystals composed of an inclusion. rich core and a clear rim, and optically...

Cryptocrystalline tourmalinites that occur discontinuously for ???30 km along basement-cover de??collements of the Orohic Alps (Italy) formed by the metasomatism of aluminous cataclasites derived from Permian conglomerates and/or feldspathic sandstones. Using Al as an immobile element monitor, calculations show that the majority of tourmalinites in the region formed through the...

Volcaniclastic units cored at depths of about 87, 164, 178, 226, and 246 m below sea level and carbonate units located between depths of 27 and 53 m below sea level in the Hilo drill core were found to be deposited at or near sea level. Four of these units...