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Articles 16711 - 16740 of 17789
Full-Text Articles in Entire DC Network
15N/14N Variations In Cretaceous Atlantic Sedimentary Sequences: Implication For Past Changes In Marine Nitrogen Biogeochemistry, Greg H. Rau, Michael A. Arthur, Walter E. Dean
15N/14N Variations In Cretaceous Atlantic Sedimentary Sequences: Implication For Past Changes In Marine Nitrogen Biogeochemistry, Greg H. Rau, Michael A. Arthur, Walter E. Dean
United States Geological Survey: Staff Publications
At two locations in the Atlantic Ocean (DSDP Sites 367 and 530) early to middle Cretaceous organic-carbon-rich beds ("black shales") were found to have significantly lower δ15N values (lower 15N/14N ratios) than adjacent organic-carbon-poor beds (white limestones or green claystones). While these lithologies are of marine origin, the black strata in particular have δ15N values that are significantly lower than those previously found in the marine sediment record and most contemporary marine nitrogen pools. In contrast, black, organic-carbon-rich beds at a third site (DSDP Site 603) contain predominantly terrestrial organic matter and have …
History Of Cultural Eutrophication At Lake Manitou, Indiana And Prospects For Its Management, Thomas Crisman
History Of Cultural Eutrophication At Lake Manitou, Indiana And Prospects For Its Management, Thomas Crisman
School of Geosciences Faculty and Staff Publications
No abstract provided.
The Role Of Gradualism And Punctuation In Cave Adaptation, David C. Culver
The Role Of Gradualism And Punctuation In Cave Adaptation, David C. Culver
International Journal of Speleology
The theory of punctuated equilibrium, offers a potential explanation for the profound morphological changes that accompany isolation in caves. I consider three aspects of punctuation theory: the association of morphological change with speciation; periods of stasis; and the number of genes controlling a trait. If the evolution of cave organisms is associated with speciation, then speciose groups and cave species derived from other cave-limited species should show increased adaptation. Analysis of Kane and Barr’s data on the subspecies of Neaphaenops tellkampfi and Holsinger’s data on crangonyctid amphipods fails to provide any support for the hypothesis. If the evolution is characterized …
The Evolution Of Non-Relictual Tropical Troglobites, Francis G. Howarth
The Evolution Of Non-Relictual Tropical Troglobites, Francis G. Howarth
International Journal of Speleology
The discovery of terrestrial troglobites living in caves on young oceanic islands with close epigean relatives living in nearby surface habitats offers unique opportunities to develop and test hypotheses concerning their evolution. Studies comparing the physiological ecology of troglobites with their epigean relatives suggest that troglobites are highly specialized to exploit resources within the system of interconnected medium-sized voids (mesocaverns) and only colonize cave passages (macrocaverns) with a stable, water vapor-saturated atmosphere. Few other animals can live in the mesocaverns. Rather than being relicts isolated in caves by the extinction of their epigean ancestral population, troglobites appear to evolve by …
Genetic Analysis Of Evolutionary Processes, Horst Wilkens
Genetic Analysis Of Evolutionary Processes, Horst Wilkens
International Journal of Speleology
Epigean and cave populations of A. fasciatus (Characidae, Pisces) differ in a series of morphological physiological, and ethological features. The interfertility of these populations made possible a genetic analysis of organs characteristic of interspecific divergence. The study of the regressive organs “eye” and “melanophore system” on the one hand and that of the constructively improved “gustatory equipment" and "feeding behaviour” on the other yielded identical principles of genetic manifestation: (1) All features have a polygenic basis with an at least di- to hexahybrid inheritance. (2) All polygenes have the same amount of expressivity. (3) After recombination of a minimum number …
Paleoenvironmental Data For N. W. Georgia, U.S.A., From Fossils In Cave Speleothems, George A. Brook, Eugene P. Keferl, Rudy J. Nickmann
Paleoenvironmental Data For N. W. Georgia, U.S.A., From Fossils In Cave Speleothems, George A. Brook, Eugene P. Keferl, Rudy J. Nickmann
International Journal of Speleology
Pollen grains and gastropod shells in two speleothems from Red Spider Cave, Georgia indicate that ca. 10,000 yr B.P. the vegetation near the cave was Mixed Mesophytic Forest. Conditions were cooler and moister than today and a shallow pond existed in the doline above the cave. As these findings support palynologic evidence from nearby pond sites it is clear that cave speleothems are a potential source of paleoecological data to ca. 350,000 yr. B.P.
Carbonate Surface Solution In The Classical Karst, Franco Cucchi, Fabio Forti, Furio Finocchiaro
Carbonate Surface Solution In The Classical Karst, Franco Cucchi, Fabio Forti, Furio Finocchiaro
International Journal of Speleology
The current research on the dissolution of carbonate rocks in the Karst of Trieste indicates that the average degradation of surfaces exposed to atmospheric agents is 0.028 mm/year with an average rainfall of 1350 mm. The maximum levels (0.031 mm/year) correspond to micro-crystalline limestones, the minimum values (0.014 mm/year) to dolomites.
Depositional And Diagenetic History Of The Middle Ordovician Carbonates Of The Shenandoah Valley, Northern Virginia, Lynn Ellen Weyenberg
Depositional And Diagenetic History Of The Middle Ordovician Carbonates Of The Shenandoah Valley, Northern Virginia, Lynn Ellen Weyenberg
OES Theses and Dissertations
An examination of the Middle Ordovician carbonates in northwest Virginia has revealed a particularly sensitive record of deposition and subsidence. Two-hundred acetate peels from six measured stratigraphic sections in Shenandoah County, Virginia were examined to interpret the depositional and diagenetic history. Two major lithofacies have been recognized within the New Market Limestone and three have been recognized in the Lincolnshire Formation. These five lithofacies represent an overall transgressive sequence. This transgression was not uniform but paused several times to allow carbonate deposition to reach sea-level. These shoaling events suggest a slowly subsiding basin in this region. The carbonate rocks within …
A Hydrogeologic Investigation Of The Balkema Wetland, Daniel V. Fronczek
A Hydrogeologic Investigation Of The Balkema Wetland, Daniel V. Fronczek
Masters Theses
The Balkema wetland, located In southwestern Kalamazoo County, Michigan, represents complex biological and hydrologic Interaction between surface water and a two-aquifer hydrologic system. Situated on the southeastern flank of the Kalamazoo moraine, the glacial geology of the area plays a key role in the understanding of the hydrogeologic function of the wetland. A two-aquifer system, an upper unconfined, and a lower confined, Interact In the vicin ity of the wetland where the c la y /till aqulclude dividing the two systems 1s absent. Various parameters, both hydrologic and geochemical, were measured In the study area, Including specific conductance values of …
Late Pleistocene Sciurids From Kokoweef Cave, H. Thomas Goodwin
Late Pleistocene Sciurids From Kokoweef Cave, H. Thomas Goodwin
Loma Linda University Electronic Theses, Dissertations & Projects
Three local (Tamias panamintinus, Ammospermophilus leucurus and Spermophilus variegatus) and five extralocal (Tamias minimus, Tamias palmeri, Marmota flaviventris, Spermophilus townsendii, and Spermophilus lateralis) sciurid species (Sciuridae) were identified from the late Pleistocene-early Holocene Kokoweef Cave paleofauna. This fauna was the first documentation of T. minimus, T. palmeri and S. townsendii from the Pleistocene of the Mohave Desert. The 30-ft sedimentary sequence apparently recorded the mid-to late-Wisconsian introduction of S. lateralis into the Kokweef fauna but otherwise documented general taxonomic stability. The ecological diversity of the fauna was consistent with--but did not require--the hypothesis of more equable late Pleistocene climates, and …
Pinuxylon Woolardii Sp. Nov., A New Petrified Taxon Of Pinaceae From The Miocene Basalts Of Eastern Oregon, William D. Tidwell, Lee R. Parker, Vaughn K. Folkman
Pinuxylon Woolardii Sp. Nov., A New Petrified Taxon Of Pinaceae From The Miocene Basalts Of Eastern Oregon, William D. Tidwell, Lee R. Parker, Vaughn K. Folkman
Faculty Publications
Specimens of the new species Pinuxylon wollardii have been collected from Miocene strata near Kurkee, OR. These petrified specimens are unique in that, due to weathering, individual tracheids and ray cells can be separated for detailed SEM studies. This species is characterized by its high number of ray cells; numerous rays; large resin ducts which are commonly paired; primarily uniseriate pitting, two to five (usually three) small, oval or cirular pinoid pits per crossfield; and smooth walls on its transverse (ray) tracheids. The latter character relates this species to taxa in the subgenus Haploxylon of Pinus. Pinuxylon woolardii is most …
International Law And External Threats To National Parks, Daniel Barstow Magraw
International Law And External Threats To National Parks, Daniel Barstow Magraw
External Development Affecting the National Parks: Preserving "The Best Idea We Ever Had" (September 14-16)
41 pages.
Contains references.
Pollution In Parks: A Publication Of The National Park Service, Richard H. Briceland
Pollution In Parks: A Publication Of The National Park Service, Richard H. Briceland
External Development Affecting the National Parks: Preserving "The Best Idea We Ever Had" (September 14-16)
28 pages (includes illustrations).
Contains references.
The National Park Idea: Historical Misconceptions And Ecological Realities, Alfred Runte
The National Park Idea: Historical Misconceptions And Ecological Realities, Alfred Runte
External Development Affecting the National Parks: Preserving "The Best Idea We Ever Had" (September 14-16)
17 pages.
Contains references.
Restoring The Biological Integrity Of Everglades National Park, Estus D. Whitfield
Restoring The Biological Integrity Of Everglades National Park, Estus D. Whitfield
External Development Affecting the National Parks: Preserving "The Best Idea We Ever Had" (September 14-16)
29 pages.
Contains references.
Protecting National Park Resources: Wildlife, George Cameron Coggins
Protecting National Park Resources: Wildlife, George Cameron Coggins
External Development Affecting the National Parks: Preserving "The Best Idea We Ever Had" (September 14-16)
28 pages.
Contains references.
Agenda: External Development Affecting The National Parks: Preserving "The Best Idea We Ever Had", University Of Colorado Boulder. Natural Resources Law Center
Agenda: External Development Affecting The National Parks: Preserving "The Best Idea We Ever Had", University Of Colorado Boulder. Natural Resources Law Center
External Development Affecting the National Parks: Preserving "The Best Idea We Ever Had" (September 14-16)
Conference organizers and/or faculty included University of Colorado School of Law professors Lawrence J. MacDonnell and Daniel Magraw.
The conference will be held at the Aspen Lodge, adjacent to Rocky Mountain National Park near Estes Park, Colorado.
It was Wallace Stegner who called the national parks "the best idea we ever had." The continuing increases in usage attest to their popularity. National parks are created to preserve areas of special scenic and cultural value for enjoyment and use. Managing the parks in a manner that protects the important values and purposes for which they were created presents important and difficult …
Moving Under, Around, And Through The Miocene Reconstruction Of Southern California, John Barron
Moving Under, Around, And Through The Miocene Reconstruction Of Southern California, John Barron
United States Geological Survey: Staff Publications
Modern southern California is fragmented by faults that juxtapose blocks with contrasting topographies and differing geologic histories. Many of the tectonic events that have shaped southern California were initiated during the Miocene, as subduction along the ancient trench margin off southern California was replaced by transform (strikeslip) faulting, such as that along the San Andreas fault.
Late Pleistocene And Holocene Paleolimnology Of Two Mountain Lakes In Western Tasmania, J. Platt Bradbury
Late Pleistocene And Holocene Paleolimnology Of Two Mountain Lakes In Western Tasmania, J. Platt Bradbury
United States Geological Survey: Staff Publications
The analysis of diatoms from two lake-sediment cores from southwestern Tasmania that span the Pleistocene-Holocene boundary provides insight about paleolimnological and paleoclimatic change in this region. Both Lake Vera (550 m elevation), in west-central Tasmania, and Eagle Tarn (1,033 m elevation), in south-central Tasmania, have lacustrine records that begin about 12,000 years ago. Despite significant differences in location, elevation, and geologic terrane, both lakes have, had similar, as well as synchronous, limnological histories. Each appears to have been larger and more alkaline 12,000 years ago than at present, and both became shallower through time. Fossil diatom assemblages about 11,500 years …
Stratigraphic And Sedimentologic Analysis Of The Middle Devonian Filer Sandstone, John Charles Rodwan
Stratigraphic And Sedimentologic Analysis Of The Middle Devonian Filer Sandstone, John Charles Rodwan
Masters Theses
The Filer Sandstone, a multistory assemblage o£ lenticular sand bodies, is a member of the Middle Devonian Amherstburg Formation of the Detroit River Group in the subsurface of the western and central portion of the Michigan Basin. It is distinguished from the reworked eolian and nearshore marine sand facies of the underlying Sylvania Sandstone by recognition of its barrier island facies relationships and stratigraphic position within enclosing carbonates unique to the Amherstburg Formation. Lithologically, the Filer ranges from a fine-grained, carbonate-cemented, supermature quartzarenite at its upper shoreface facies, to a texturally-inverted sandy carbonate at its lagoonal facies. Facies distribution was …
Paleoclimates In Southwestern Tasmania During The Last 13,000 Years, Vera Markgraf, J. Platt Bradbury, J.R. Busby
Paleoclimates In Southwestern Tasmania During The Last 13,000 Years, Vera Markgraf, J. Platt Bradbury, J.R. Busby
United States Geological Survey: Staff Publications
Plant-sociological and climatic classification of the Australian Nothofagus cunninghamii rain forest provides the basis for a new, semiquantitative approach to interpretations of late-Quaternary paleoclimates from four pollen sequences in southwestern Tasmania. Varying proportions of rain-forest pollen types in the records were related to different modern rain-forest alliances and their specifc climatic regimes, such as Eastern Rain Forest, Leatherwood Rain Forest, and sclerophyllous, Subalpine Rain Forest. According to this interpretation, early Holocene climates were characterized by 1,600 mm annual precipitation and 10°C annual temperature, conditions substantially warmer and drier than previously thought. Maximum precipitation levels of 2,500 mm annually were not …
Abatement Of Nitrate Pollution In Groundwater And Surface Runoff From Cropland Using Legume Cover Crops With No-Till Corn, M. Scott Smith, Jac J. Varco
Abatement Of Nitrate Pollution In Groundwater And Surface Runoff From Cropland Using Legume Cover Crops With No-Till Corn, M. Scott Smith, Jac J. Varco
KWRRI Research Reports
Agricultural practices can have a significant impact on water quality. The effects of leguminous winter cover crops on leaching of NO-3; from soil have been investigated in this project. Legume cover crops, by fixation of atmospheric N, can reduce the amount of fertilizer N required to produce summer grain crops. The methods initially used to evaluate cover crop effects on No; transport included suction probe lysimeters and measurement of NO-3; in soil samples collected to a depth of 90 cm. These measurements demonstrated extreme spatial variability in NO-3; distribution and water …
Benthic Foraminifera And Paleoenvironments Of The Arcola Limestone Member Mooreville Formation (Campanian) In Eastern Mississippi And Western Alabama, Julia K. Palmer
Benthic Foraminifera And Paleoenvironments Of The Arcola Limestone Member Mooreville Formation (Campanian) In Eastern Mississippi And Western Alabama, Julia K. Palmer
OES Theses and Dissertations
Eighty-one species of benthic foraminifera have been recovered from chalky marls of the upper Mooreville Formation including the Arcola Limestone Member, and the basal Demopolis Formation located in five sections in east-central Mississippi and west-central Alabama. These species have been described and seventy-nine illustrated. Analysis of the environmental or depth preferences of abundant species together with planktonic percentages and benthic species diversity, indicates that the chalky marls were deposited in a broad shallow shelf sea (subtidal conditions less than 100m) greatly influenced by open ocean conditions. The benthic assemblage is composed of a mixture of typically neritic and bathyal species …
Long-Term Effects Of Tillage On The Retention And Transport Of Soil Water, H. D. Scott, L. S. Wood, W. M. Miley
Long-Term Effects Of Tillage On The Retention And Transport Of Soil Water, H. D. Scott, L. S. Wood, W. M. Miley
Arkansas Water Resources Center Technical Reports
Quantitative measurements were made of the physical and chemical properties of two virgin prairie soils, Crowley and Jay, that remain in their native Arkansas environments and of similar soils that had been tilled extensively. Comparisons were made of soil properties at several depths. When compared with the tilled soils the virgin soils had higher organic matter contents, saturated hydraulic conductivities and water retained at several applied pressures. Bulk densities and hydraulic resistances were lower in the virgin soils. For the Crowley silt loam, values of pH and elemental contents of the virgin soil were higher than those of the tilled …
Algal Growth Potentials And Heavy Metal Concentrations Of The Primary Streams To Upper Beaver Lake, Richard L. Meyer, W. Reed Green, Kenneth F. Steele, Diana Wickliff
Algal Growth Potentials And Heavy Metal Concentrations Of The Primary Streams To Upper Beaver Lake, Richard L. Meyer, W. Reed Green, Kenneth F. Steele, Diana Wickliff
Arkansas Water Resources Center Technical Reports
Meyer and Green (1984) demonstrated the probable inhibition of algal growth potential by heavy metals in upper Beaver Lake. Upper Beaver Lake receives water from three tributaries. One contains a small reservoir and the combined streams receive sewage input. Collections were made approximately monthly at eight sites for the Algal Assay Bottle Test (AABT) and heavy metal analysis. In general, AABT results indicated that the collections above the sewage lnput were phosphorus limited while those below were nitrogen or combined nitrogen and phosphorus limited. Growth inhibition occurred during summer and early fall at various sites with greater inhibition at the …
The Population Biology Of Oak Middle Creek Structure 58-B After An Experimental Stocking With Adult Fish: A Three Year Evaluation, Donn A. Rodekohr
The Population Biology Of Oak Middle Creek Structure 58-B After An Experimental Stocking With Adult Fish: A Three Year Evaluation, Donn A. Rodekohr
School of Natural Resources: Dissertations, Theses, and Student Research
No abstract provided.
Factors Affecting Epithecal Growth Lines In Four Coral Species, With Paleontological Implications, Jean-Luc Liénard
Factors Affecting Epithecal Growth Lines In Four Coral Species, With Paleontological Implications, Jean-Luc Liénard
Loma Linda University Electronic Theses, Dissertations & Projects
The number of epithecal (external) growth lines was surveyed over 124 days for Montastrea annularis growing at different depths (3.5 m to 61 m). There was a significant (P< .01) decrease in the number of lines with depth. Although the linear regression is significant, there is evidence for a logarithmic or quadratic relationship, and more data from greater depths are needed to determine which of these gives a better fit.
The number of growth lines formed during light-dark cycles of 16, 24 and 32 hours were compared for M. annularis, M. cavernosa, Porites astreoides and Tubastrea aurea. The variability among colonies from the same species was in many cases more significant than that among light treatments. This is a serious problem for anyone counting lines in corals, especially from a few specimens; therefore conclusions based on such counts seem hazardous on …
Dynamic Deformation Of Volcanic Ejecta From The Toba Caldera: Possible Relevance To Cretaceous/Tertiary Boundary Phenomena, Neville L. Carter, Charles B. Officer, Craig A. Chesner, William I. Rose
Dynamic Deformation Of Volcanic Ejecta From The Toba Caldera: Possible Relevance To Cretaceous/Tertiary Boundary Phenomena, Neville L. Carter, Charles B. Officer, Craig A. Chesner, William I. Rose
Department of Geological and Mining Engineering and Sciences Publications
Plagioclase and biotite phenocrysts in ignimbrites erupted from the Toba caldera, Sumatra, show microstructures and textures indicative of shock stress levels higher than 10 GPa. Strong dynamic deformation has resulted in intense kinking in biotite and, with increasing shock intensity, the development in plagioclase of planar features, shock mosaicism, incipient recrystallization, and possible partial melting. Microstructures in quartz indicative of strong shock deformation are rare, however, and many shock lamellae, if formed, may have healed during post-shock residence in the hot ignimbrite; they might be preserved in ash falls. Peak shock stresses from explosive silicic volcanism and other endogenous processes …
Diagenesis And Water Chemistry Of The Woodbine Group In The East Texas Basin, Helmuth Victor Wuerch
Diagenesis And Water Chemistry Of The Woodbine Group In The East Texas Basin, Helmuth Victor Wuerch
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
Petrographic and SEM study of flu vial-deltaic sections of the Woodbine Group in the East Texas Basin indicates that authigenic mineral suites are controlled, in part, by the presence of organic-rich matrix.
During early, precompaction diagenesis, organic matter supplied the metabolic fuel required by sulfate-reducing bacteria to reduce sulfate in depositional waters ultimately to pyrite. With burial the sulfate supply was ultimately exhausted, and bicarbonate activity thereafter controlled the precipitation of siderite and Fe-calcite.
Matrix material supplied the components and reaction sites for the most import ant porosity-occluding reaction: kaolinite --> Fe,M g chlorite. Matrix physically inhibited the growth of …
The Ecology Of Skeleton Weed In Western Australia, Afghan Thistle Ecology, Biology Of Gorteria Personata., J. Dodd
Experimental Summaries - Plant Research
The ecology of skeleton weed in Western Australia, 84BA17. Afghan thistle ecology, 84N050. Regenerative ability of stem and root segments, 85PE51. Biology of Gorteria personata, 86M03, 86N08. Life cycle, 86M03, 86N08. Germination requirements, 86PE7.