Publications

Entomologists who enter national parks often are surprised by the diversity of life and geography found in these remarkable natural areas. There are ichneumon wasps, carabid beetles, leps…and, of course, there are trees and mountains. In contrast, an average person entering the same parks will see the magnificent mountains and rivers, the endless forests and meadows, and the abundant...

We investigated habitat specificity of the amber darter (Percina antesella Williams & Etnier 1977), an imperiled fish from restricted portions of 2 rivers in the southeastern United States. Foraging amber darters occupied a narrow range of riffle habitat, consistently avoiding areas 20 cm deep and with velocity 10 cm. s−1 near the substrate, occupying areas with cobble or gravel...

40Ar/39Ar plateau age spectra of seven sanidine samples from the Fire Clay tonstein (Middle Pennsylvanian), collected along a 300-km traverse in the Appalachian basin, range from 310.3 to 311.4 Ma. All plateau ages agree, within the limits of analytical precision, with their respective total gas ages. This agreement, together with the reproducibility between samples, suggests the...

Field studies and 40Ar/39Ar dating reveal that silicic volcanism in the Davis Mountains part of the Trans-Pecos Texas volcanic field occurred in six episodes at 0.3 m.y. intervals between 36.8 and 35.3 Ma. Additionally, two groups of silicic intrusions were emplaced at 34.6 and 32.8 Ma. This episodicity is similar to that determined for volcanic fields dominated by ash-flow tuffs, yet...

40Ar/39Ar ages of volcanic rocks are used to provide numerical constraints on the age of middle and upper Miocene sedimentary strata collected along the Porcupine River. Intercalated sedimentary rocks north of latitude 67°10′N in the Porcupine terrane of east-central Alaska contain a rich record of plant fossils. The fossils are valuable indicators of this interior region's paleoclimate...

The Middle Pennsylvanian Fire Clay tonstein, mostly kaolinite and minor accessory minerals, is an altered and lithified volcanic ash preserved as a thin, isochronous layer associated with the Fire Clay coal bed. Seven samples of the tonstein, taken along a 300-km traverse of the central Appalachian basin, contain cogenetic phenocrysts and trapped silicate-melt inclusions of a rhyolitic...

Two mechanistic models—which are unlike the traditional plate-tectonic landfill models used for most proposed Pangea reconstructions of the Yucatán block—relate the Mesozoic opening of the Gulf of Mexico directly to the movement of the North and South American plates: (1) a previous piggyback model in which Yucatán moves with South America out of the western gulf and (2) a new edge...

Hatchery-reared salmonids often contain proportionally greater amounts of body lipid (storage fat) and proportionally lesser amounts of body protein (muscle) and ash (bone) than do their wild counterparts of equal size. The effect of body composition on postrelease survival and subsequent return of mature adults is presently unknown. High lipid deposits may benefit the fish by providing...

The U.S. Geological Survey (USGS) is assessing the ground.water resources of the carbonate bedrock aquifers in Indiana and Ohio as part of their Regional Aquifer Systems Analysis program. Part of this assessment includes the determination of unknown aspects of the hydraulic characteristics, boundaries, and flow paths of the carbonate aquifer. To accomplish this, the USGS drilled three...

No abstract available.

Hydrologic controls on sulfate mobility were investigated in a forested catchment in the Georgia Piedmont using a watershed mass balance approach. Variations in annual sulfate export were governed primarily by differences in runoff rather than by differences in sulfate deposition or in total annual precipitation. However, 2 years with similar total runoff had substantially different...

No abstract available.