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Articles 15271 - 15300 of 17792
Full-Text Articles in Entire DC Network
A Multi-Tracer Study Of Saltwater Origin, Cross-Formational Flow, And The Geochemical Evolution Of Groundwater In The Southern High Plains Aquifer Along The Western Caprock Escarpment, East-Central New Mexico, Jeff Langman
Open Access Theses & Dissertations
Sustainable management of groundwater resources requires sufficient knowledge of the distribution of fresh and saline groundwater and the processes affecting saltwater intrusion that may influence the beneficial use of groundwater. A hydrogeologic investigation that coupled various chemical and isotopic tracers, including 3H/3He, 14C, δD, δ18O, 87Sr/86Sr, and δ11B, with the physical characteristics of the aquifer was conducted to determine source waters, the origin of saltwater and its influence through cross-formational flow, and water-rock interactions in the Southern High Plains aquifer along the Western Caprock Escarpment. Sub-aquifers or local flow systems are present along the Western Caprock Escarpment, and the study …
Using Elliptical Fourier Analysis To Compare Size Of Morphospace Occupation Between Modern Edentulous Freshwater Unionoid Mussels And The Fossils At L6516 (Slope County, North Dakota, Usa), With Remarks On Preservation, Mathew E. Burton-Kelly
Theses and Dissertations
The purpose of this project was to use outline morphometric techniques to determine the number of freshwater mussel taxa present at locality L6516 (“Das Goods”),which is located in Cretaceous strata in the basal Ludlow Member of the Fort Union Formation in Slope County, North Dakota, U.S.A. Secondary goals were to improve the outline morphometric procedures that have been previously used to characterize fossil and extant freshwater mussels, and to describe in more detail the preservation of the edentulous unionoid specimens from the Das Goods area.
Outlines of individual mussel valves were used for morphometric analyses due to lack of preserved …
Characterization Of The Lucinid Bivalve-Bacteria Symbiotic System: The Significance Of The Geochemical Habitat On Bacterial Symbiont Diversity And Phylogeny, Angela Marissa Green-Garcia
Characterization Of The Lucinid Bivalve-Bacteria Symbiotic System: The Significance Of The Geochemical Habitat On Bacterial Symbiont Diversity And Phylogeny, Angela Marissa Green-Garcia
LSU Master's Theses
Extensive characterization of a single lucinid bivalve habitat was conducted to characterize the relationship between host bivalve and thiotrophic bacterial endosymbionts. For lucinids, the ecological and evolutionary relationships between hosts and endosymbionts are poorly understood. Reconstructing the evolutionary history of lucinid endosymbiosis, and the geologic significance of the association, has been hampered by insufficient knowledge of endosymbiont ecology and taxonomic diversity. Host organisms (Lucinisca nassula and Phacoides pectinatus) were collected from Cedar Keys, Florida, within the top 15-20 cm of the sediment in sea grass beds. PCR amplification and sequencing of bacterial 16S rRNA genes from lucinid gills and sediment …
Using Biosolids To Enhance Phytoremediation Of Oil-Contaminated Soil, Heather N. Markway, Duane C. Wolf, Kaaron J. Davis, Edward E. Gbur
Using Biosolids To Enhance Phytoremediation Of Oil-Contaminated Soil, Heather N. Markway, Duane C. Wolf, Kaaron J. Davis, Edward E. Gbur
Discovery, The Student Journal of Dale Bumpers College of Agricultural, Food and Life Sciences
While the plant rhizosphere and associated microbial processes have been shown to amplify the degradation rate of chemical residues in soils, phytoremediation can be a slow process. The objective of this greenhouse study was to determine if the addition of biosolids as an organic soil amendment would enhance growth of plants in oil-contaminated soil and thus potentially increase effectiveness of phytoremediation. Pearl millet (Pennisetum glaucum (L.) R. Br.) or sudangrass (Sorghum sudanense (Piper) Stapf (Piper)) was grown in a Captina silt loam (finesilty, siliceous, mesic Typic Fragiudults) contaminated with 5% crude oil (v/w) and amended with 24 g biosolids/kg soil. …
The Balancing Act, David Weaver
The Balancing Act, David Weaver
Conference papers and presentations
Nutrient management is as much a global issue as a local one with a balance required between economics and environment, inherent biological limitations and expectations of nutrient use efficiency, and traditional fertiliser practices and actual enterprise nutrient requirements. The concept of nutrient balance depends on context and scale. Nutrient balance can be considered at a global scale, where issues of nutrient stocks, cycles, depletion and transfer of a particular element are important. For a single farm enterprise, nutrient balance might be considered in terms of phosphorus (P) inputs into and outputs from the enterprise. This is commonly known as a …
Reclamation Of Saline Soils Through Revegetation In Australia: Plants, Processes And People, Edward G. Barrett-Lennard
Reclamation Of Saline Soils Through Revegetation In Australia: Plants, Processes And People, Edward G. Barrett-Lennard
Conference papers and presentations
Secondary salinity (salinity induced by human activity) is a major world problem. Hydrological imbalances in landscapes cause watertables to rise, drawing salt from deeper in the soil profile to the soil surface, where the combined stresses of salinity and waterlogging threaten the growth of crops and pastures. The reversal of salinity by the broad‐scale reintroduction of perennial plants back into landscapes may not be economically feasible, but watertables may be at least partly directly drawn‐down by the grow th of salt tolerant plants (halophytes) on saltland . This review summarises data from Australia in which the water use by perennial …
Introduction To Special Section On Microcosms In Ice: The Biogeochemistry Of Cryoconite Holes, Andrew G. Fountain, Martyn Tranter
Introduction To Special Section On Microcosms In Ice: The Biogeochemistry Of Cryoconite Holes, Andrew G. Fountain, Martyn Tranter
Geology Faculty Publications and Presentations
Cryoconite holes are small, water filled, cylindrical melt-holes on glacial ice surface. Cryoconite, 'cold dust,' refers to the thin layer of sediment at the hole bottom. The holes form from surficial sediment patches that absorbs more solar radiation than the surrounding ice and which preferentially melt into the glacier forming a cylindrical water-filled hole. These holes form on the ice-covered, as opposed to snow covered, parts of glaciers world-wide, wherever there is sufficient energy for melting. Biogeochemically, cryoconite holes are interesting because the sediment is inncoculated with biologic material, a fraction of which thrives in the cryoconite environment of near-freezing …
Water Centrality For Water And Society, Ute Goeft
Water Centrality For Water And Society, Ute Goeft
Theses: Doctorates and Masters
The current approach to water management in Western societies, including Australia, is based on allocating water between different users. Appropriate for commercial uses, this commodity view of water has proved difficult for the inclusion of environmental and social concerns. Issues, such as which aspects have precedence, how much water should be allocated to each and how to make trade-offs in cases of insufficient water, pose problems that are yet to be worked out. In addition, there is a lack of knowledge regarding the identification of environmental as well as social water needs. The latter has prompted the writing of this …
Rapid Evolution In Introduced Species, ‘Invasive Traits’ And Recipient Communities: Challenges For Predicting Invasive Potential, Kenneth D. Whitney, Christopher A. Gabler
Rapid Evolution In Introduced Species, ‘Invasive Traits’ And Recipient Communities: Challenges For Predicting Invasive Potential, Kenneth D. Whitney, Christopher A. Gabler
School of Earth, Environmental, & Marine Sciences Faculty Publications
The damaging effects of invasive organisms have triggered the development of Invasive Species Predictive Schemes (ISPS). These schemes evaluate biological and historical characteristics of species and prioritize those that should be the focus of exclusion, quarantine, and/or control. However, it is not clear how commonly these schemes take microevolutionary considerations into account. We review the recent literature and find that rapid evolutionary changes are common during invasions. These evolutionary changes include rapid adaptation of invaders to new environments, effects of hybridization, and evolution in recipient communities. Strikingly, we document 38 species in which the specific traits commonly associated with invasive …
Iron Ooid Beds Of The Carolinefjellet Formation, Spitsbergen, Norway, Jeremy Mutrux, Harmon D. Maher Jr., Robert Duncan Shuster
Iron Ooid Beds Of The Carolinefjellet Formation, Spitsbergen, Norway, Jeremy Mutrux, Harmon D. Maher Jr., Robert Duncan Shuster
Geography and Geology Faculty Publications
Iron ooid beds are unusual deposits that have been linked to greenhouse conditions and the transgressive flooding of shallow shelves, and which were globally prevalent during certain periods. Within the marine, Aptian-Albian, Carolinefjellet Formation of Spitsbergen, chamosite ooids have been found within distinctive sandstone beds at six localities, and at a consistent stratigraphic position within the basal Dalkjegla Member. Distinctive characteristics include the iron ooids themselves, a coarser grain size, intercalation with silty siderites, grading, cross-beds indicating offshore or longshore transport, and a lack of burrowing. The enclosing sands display planar and hummocky crossstratification and abundant oscillation ripple marks, and …
Estimation Of Evapotranspiration Of Cottonwood Trees In The Cibola National Wildlife Refuge, Cibola, Arizona, Amity J. Jetton
Estimation Of Evapotranspiration Of Cottonwood Trees In The Cibola National Wildlife Refuge, Cibola, Arizona, Amity J. Jetton
Browse all Theses and Dissertations
This study used sap flow measurements and satellite imagery to estimatewater use by cottonwood (Populus fremontii S. Wats. ssp) trees in an irrigated restoration plot at Cibola National Wildlife Refuge on the Lower Colorado River. Several thousand hectares of irrigated plots of this type are planned to improve riparian habitat on the river, hence it is important to know how much water the trees require. In this study, the ET rates for 20 Freemont cottonwood trees, from an 8 ha plot, were monitored over a 30-day period. ET rates were estimated by measuring sap flow through branches of the trees. …
The Impact Of Nutrient Availability And Algal Community On Carbon Isotope Fractionaion In Crystal Lake, Clark County, Ohio, April R. Wisebaker
The Impact Of Nutrient Availability And Algal Community On Carbon Isotope Fractionaion In Crystal Lake, Clark County, Ohio, April R. Wisebaker
Browse all Theses and Dissertations
Crystal Lakes are a group of four interconnected lakes, located in southwestern Clark County, Ohio. Several studies have looked at separate geochemical and isotopic information at this location. However, no one has thoroughly studied the relationship between the algal community, geochemistry, and carbon isotope fractionation within Crystal Lake. The fractionation of carbon isotopes of dissolved inorganic carbonate is greatly affected by the process of photosynthesis; the amount of photosynthesis is affected by the amount of algae in the aquatic community; the amount of algae is affected by the available nutrients in system. Therefore, there should be a correlation between the …
Paleoenvironment And Lateral Extent Of An Exposed Carbonate Build-Up: Horry County, South Carolina, Lisa A. Raterink
Paleoenvironment And Lateral Extent Of An Exposed Carbonate Build-Up: Horry County, South Carolina, Lisa A. Raterink
Browse all Theses and Dissertations
A carbonate build-up exposed in the Intracoastal Waterway in Horry County, South Carolina is estimated to be Pleistocene to Pliocene in age. The carbonate build-up discontinuously spans approximately 12 kilometers of the waterway. Prominent formations in the area consist of the Waccamaw and the Canepatch Formation. A distinct sand layer is present laterally between the build-up and the excavated waterway bank, which consists primarily of well preserved fossil molluscs and echinoderms.
Field observations show that the carbonate build-up is bluish-gray in color and composed of shell fragments, predominantly mollusc, in a mud matrix. Thin sections analyzed, using a petrographic microscope, …
Availability And Toxicity Of Nickel To Lotic Periphyton And Macroinvertebrates, Stephanie Marie Bessom
Availability And Toxicity Of Nickel To Lotic Periphyton And Macroinvertebrates, Stephanie Marie Bessom
Browse all Theses and Dissertations
There is a lack of information regarding the bioaccumulation and toxicity of nickel (Ni) to lotic ecosystems. The objective of this study was to investigate the source, uptake, and toxicity of Ni by periphyton and macroinvertebrates (Hyalella azteca and Daphnia magna) in simulated stream ecosystems that included sediment and water. Periphyton were exposed to two types of sediment, a low-organic sandy mixture and a high organic silt, treated with varying levels of Ni. After 96 h, Ni levels in overlying water and periphyton were related to those in sediments, although differences existed between sediment types. Tests with 64Ni added to …
Investigating Nickel Flux And Toxicity In Clay Sediments With Batch And Stream Recirculating Flume Experiments, Christina Elizabeth Cloran
Investigating Nickel Flux And Toxicity In Clay Sediments With Batch And Stream Recirculating Flume Experiments, Christina Elizabeth Cloran
Browse all Theses and Dissertations
Using batch and stream recirculating flume experiments to compare and contrast one clayey sediment (Warden Ditch) and two analytical grade clay minerals (montmorillonite and kaolinite), the dynamic interactions between two aquatic stressors (suspended solids and nickel) were explored. Aldrich humic acid was incorporated to demonstrate the mitigating effects of dissolved organic carbon (DOC) on Ni toxicity. The flux of Ni between compartments (dissolved and sorbed) was quantified as a partition/distribution coefficient. The USEPA test organism Daphnia magna (neonates, < 24 h) was utilized to evaluate toxicity in dynamic non-renewal, short-term bioassays. Generally, toxicity showed a linear relationship with turbidity level. Conversely, sorption coefficients were experiment specific, making them difficult to predict and assess. Clay functioned as an adsorbent, scavenging Ni. Results support the hypotheses that solids and metals act as stressors in streams, DOC attenuates the toxicity of Ni, and Ni fluxes quickly between system compartments.
Cenozoic Antarctic Diatomware/Bugcam: An Aid For Research And Teaching, Sherwood W. Wise, M. Olney, J. M. Covington, V. M. Egerton, S. Jiang, D. K. Kulhanek, S. Ramdeen, H. Schrader, P. A. Sims, A. S. Wood, A. Davis, D. R. Davenport, N. Doepler, W. Falcon, C. Lopez, T. Pressley, O. L. Swedberg, David M. Harwood
Cenozoic Antarctic Diatomware/Bugcam: An Aid For Research And Teaching, Sherwood W. Wise, M. Olney, J. M. Covington, V. M. Egerton, S. Jiang, D. K. Kulhanek, S. Ramdeen, H. Schrader, P. A. Sims, A. S. Wood, A. Davis, D. R. Davenport, N. Doepler, W. Falcon, C. Lopez, T. Pressley, O. L. Swedberg, David M. Harwood
Department of Earth and Atmospheric Sciences: Faculty Publications
Cenozoic Antarctic DiatomWare/BugCam© is an interactive, icon-driven digital-image
database/software package that displays over 500 illustrated Cenozoic Antarctic diatom taxa along with original descriptions (including over 100 generic and 20 family-group descriptions). This digital catalog is designed primarily for use by micropaleontologists working in the field (at sea or on the Antarctic continent) where hard-copy literature resources are limited. This new package will also be useful for classroom/lab teaching as well as for any paleontologists making or refining taxonomic identifications at the microscope. The database (Cenozoic Antarctic DiatomWare) is displayed via a custom software program (BugCam) …
New Approaches And Progress In The Use Of Polar Marine Diatoms In Reconstructing Sea Ice Distribution, A. Leventer, L. Armand, David M. Harwood, R. Jordan, R. Ligowski
New Approaches And Progress In The Use Of Polar Marine Diatoms In Reconstructing Sea Ice Distribution, A. Leventer, L. Armand, David M. Harwood, R. Jordan, R. Ligowski
Department of Earth and Atmospheric Sciences: Faculty Publications
Reconstructing the paleo-latitudinal extent of sea ice in the Southern Ocean over time can be accomplished using modern diatom data. However, it is more difficult to extend the utility of diatom proxies farther back in time, to time periods characterized by species that are now extinct, since we are uncertain of the paleoenvironmental affiliation of those species we can’t observe in modern assemblages. We propose several research strategies to strengthen our ability to use diatom data to reconstruct sea ice history. These tactics include the evaluation of specific morphologic characteristics and distinct taxa, as well as the identification of specific …
Hydrogeochemistry And Water Quality Of Echo Hills, Joel M. Kimball
Hydrogeochemistry And Water Quality Of Echo Hills, Joel M. Kimball
Browse all Theses and Dissertations
Ground water of the Echo Hills area in Clark County, Ohio was investigated for common water contaminants such as nitrate and coliform bacteria. Thirty-four water samples were collected from locations including private wells, streams and a spring. Nine of those samples were selected for nitrogen isotope analysis. Three locations were chosen for a tracer test. Additionally, well log data, historical water quality data, and GIS data were obtained from the Clark County Health Department in Springfield, Ohio. Results show that local agriculture likely has the greatest impact on ground water quality in Echo Hills especially the north-eastern portion, with local …
On The Origin And Age Of The Arıburnu Beachrock, Gelibolu Peninsula, Turkey, Ahmet Evren Ergi̇nal, Nafi̇ye Kiyak Güneç, Mustafa Bozcu, Ahmet Ertek, Hakan Güngüneş, Ali̇ Sungur, Gülen Türker
On The Origin And Age Of The Arıburnu Beachrock, Gelibolu Peninsula, Turkey, Ahmet Evren Ergi̇nal, Nafi̇ye Kiyak Güneç, Mustafa Bozcu, Ahmet Ertek, Hakan Güngüneş, Ali̇ Sungur, Gülen Türker
Turkish Journal of Earth Sciences
The beachrock formation on the Arıburnu coast situated in the Gelibolu Peninsula has been studied by field observation, thin-section interpretation, physicochemical analyses including ICP-AES and SEM/EDS, and OSL dating. These analyses reveal the presence of different amounts of major (Si, Ca, Mg, K, Fe, Al and Na) and trace elements within the beachrock cement with Si (36.2%) and Ca (32.68%) dominating the overall composition. Beachrocks composed of highly-fractured and friable beds reach a total thickness of 80 cm extending from +60 cm at the uppermost level down to -1 m at their most seaward extent and grade from conglomerate to …
Trace Fossils Of The Upper Eocene-Lower Oligocene Transition Of The Manipur, Indo-Myanmar Ranges (Northeast India), Rajkumar Hemanta Singh, Francisco J. Rodriguez Tovar, Soibam Ibotombi
Trace Fossils Of The Upper Eocene-Lower Oligocene Transition Of The Manipur, Indo-Myanmar Ranges (Northeast India), Rajkumar Hemanta Singh, Francisco J. Rodriguez Tovar, Soibam Ibotombi
Turkish Journal of Earth Sciences
A detailed ichnological analysis, for the first time, has been preformed on Upper Eocene-Lower Oligocene Transition of Manipur, Indo-Myanmar Ranges (Northeast India). Previous trace fossil analyses in India are scarce and usually poorly detailed, especially with respect to Cenozoic materials. Sediments from the Disang and Barail groups contain a relatively abundant and moderately diverse trace fossil assemblage that has been characterized at the ichnogenus and ichnospecies level. ?Arenicolites Salter 1857, Helminthopsis tenuis Ksiazkiewicz 1968, Ophiomorpha nodosa Lundgren 1891, Phycodes palmatus (Hall 1852), Planolites montanus Richter 1937, Rhizocorallium jenense Zenker 1836, Thalassinoides paradoxicus (Woodward 1830) and Skolithos linearis (Haldeman 1840) have …
Life In A Temperate Polar Sea: A Unique Taphonomic Window On The Structure Of A Late Cretaceous Arctic Marine Ecosystem, Karen Chin, John Bloch, Arthur Sweet, Justin Tweet, Jaelyn Eberle, Stephen Cumbaa, Jakub Witowski, David M. Harwood
Life In A Temperate Polar Sea: A Unique Taphonomic Window On The Structure Of A Late Cretaceous Arctic Marine Ecosystem, Karen Chin, John Bloch, Arthur Sweet, Justin Tweet, Jaelyn Eberle, Stephen Cumbaa, Jakub Witowski, David M. Harwood
Department of Earth and Atmospheric Sciences: Faculty Publications
As the earth faces a warming climate, the rock record reminds us that comparable climatic scenarios have occurred before. In the Late Cretaceous, Arctic marine organisms were not subject to frigid temperatures but still contended with seasonal extremes in photoperiod. Here, we describe an unusual fossil assemblage from Devon Island, Arctic Canada, that offers a snapshot of a ca 75 MYR ago marine paleoecosystem adapted to such conditions. Thick siliceous biogenic sediments and glaucony sands reveal remarkably persistent high primary productivity along a high-latitude Late Cretaceous coastline. Abundant fossil feces demonstrate that this planktonic bounty supported benthic invertebrates and large, …
Elevated Primary Productivity Of Calcareous Nannoplankton Associated With Ocean Anxoic Event 1b During The Aptian/Albian Transition (Early Cretaceous), Emily L. Browning, David K. Watkins
Elevated Primary Productivity Of Calcareous Nannoplankton Associated With Ocean Anxoic Event 1b During The Aptian/Albian Transition (Early Cretaceous), Emily L. Browning, David K. Watkins
Department of Earth and Atmospheric Sciences: Faculty Publications
Previous isotopic investigations of Aptian/Albian oceanic anoxic event (OAE) 1b from the western North Atlantic (Blake Nose) posited that increased sea surface temperatures and decreased salinity led to stratification of the upper water column, resulting in lowered dissolved oxygen and enhanced organic matter preservation. We examined calcareous nannofossils from the same site in the western North Atlantic (Blake Nose) to evaluate changes in surface water conditions prior to, during, and after the Aptian/Albian OAE1b. The results of our analysis conflict somewhat with the previous interpretation that OAE1b at Blake Nose was linked to water column stratification. The signal from calcareous …
Plant-Feeding Hemiptera And Orthoptera Communities In Native And Restored Mesic Tallgrass Prairies, Kristine T. Nemec, Thomas B. Bragg
Plant-Feeding Hemiptera And Orthoptera Communities In Native And Restored Mesic Tallgrass Prairies, Kristine T. Nemec, Thomas B. Bragg
United States Army Corps of Engineers, Omaha District
Aboveground Hemiptera and Orthoptera communities were compared among three native and three restored mesic tallgrass prairies along the Platte River in central Nebraska to assess both the relative success of restored sites and the relationship between insect and plant communities. Hemiptera and Orthoptera were sampled using sweep nets in early June, mid-July, and mid-August 2000. Plant species composition was assessed in early June and mid-August. A total of 89 Auchenorrhyncha (71 Cicadellidae, 15 Fulgoroidea, and 3 Membracidae) and 23 orthopterans (15 Acrididae and 8 Tettigoniidae) were collected. Eighty-five plant species were observed in combined study sites. Shannon diversity was significantly …
Bioaccumulation Of Pharmaceuticals And Other Anthropogenic Waste Indicators In Earthworms From Agricultural Soil Amended With Biosolid Or Swine Manure, Chad Kinney, Edward Furlong, Dana Kolpin, Mark Burkhardt, Steven Zaugg, Stephen Werner, Joseph Bossio, Mark Benotti
Bioaccumulation Of Pharmaceuticals And Other Anthropogenic Waste Indicators In Earthworms From Agricultural Soil Amended With Biosolid Or Swine Manure, Chad Kinney, Edward Furlong, Dana Kolpin, Mark Burkhardt, Steven Zaugg, Stephen Werner, Joseph Bossio, Mark Benotti
United States Geological Survey: Staff Publications
Analysis of earthworms offers potential for assessing the transfer of organic anthropogenic waste indicators (AWIs) derived from land-applied biosolid or manure to biota. Earthworms and soil samples were collected from three Midwest agricultural fields to measure the presence and potential for transfer of 77 AWIs from land-applied biosolids and livestock manure to earthworms. The sites consisted of a soybean field with no amendments of human or livestock waste (Site 1), a soybean field amended with biosolids from a municipal wastewater treatment plant (Site 2), and a cornfield amended with swine manure (Site 3). The biosolid applied to Site 2 contained …
Geochemical Evidence For Airborne Dust Additions To Soils In Channel Islands National Park, California, Daniel R. Muhs, James R. Budahn, Donald L. Johnson, Marith Reheis, Jossh Beann, Gary Skipp, Eric Fischer, Julia A. Jones
Geochemical Evidence For Airborne Dust Additions To Soils In Channel Islands National Park, California, Daniel R. Muhs, James R. Budahn, Donald L. Johnson, Marith Reheis, Jossh Beann, Gary Skipp, Eric Fischer, Julia A. Jones
United States Geological Survey: Staff Publications
There is an increasing awareness that dust plays important roles in climate change, biogeochemical cycles, nutrient supply to ecosystems, and soil formation. In Channel Islands National Park, California, soils are clay-rich Vertisols or Alfi sols and Mollisols with vertic properties. The soils are overlain by silt-rich mantles that contrast sharply with the underlying clay-rich horizons. Silt mantles contain minerals that are rare or absent in the volcanic rocks that dominate these islands. Immobile trace elements (Sc-Th-La and Ta-Nd-Cr) and rare-earth elements show that the basalt and andesite on the islands have a composition intermediate between upper-continental crust and oceanic crust. …
Deciphering Climatic History From Lake Sediments, Sherilyn C. Fritz
Deciphering Climatic History From Lake Sediments, Sherilyn C. Fritz
Department of Earth and Atmospheric Sciences: Faculty Publications
Reconstructing climate from lake sediments can be challenging, because the response of lakes and various components of lake systems are mediated by non-climatic factors, such as geomorphic and hydrologic stetting. As a result, the magnitude of lake response to climatic forcing may be non-linear. In addition, changes in the lake system associated with the aging process or non-climatic influences may alter the response to a given climate perturbation. These non-linear and nonstationary characteristics can produce spatial heterogeneity in the pattern and timing of inferred change. One approach for generating regionally robust climatic interpretations from lakes is to increase coordinated efforts …
Holocene Multidecadal- To Millennial-Scale Hydrologic Variability On The South American Altiplano, Erick Ekdahl, Sherilyn C. Fritz, Paul A. Baker, Catherine Rigsby, Kirstin Coley
Holocene Multidecadal- To Millennial-Scale Hydrologic Variability On The South American Altiplano, Erick Ekdahl, Sherilyn C. Fritz, Paul A. Baker, Catherine Rigsby, Kirstin Coley
Department of Earth and Atmospheric Sciences: Faculty Publications
Precipitation on the South American Altiplano varies at a range of temporal scales. A long-term secular increase in moisture availability from the early/mid Holocene to the present, driven by increasing summer insolation resulting from precessional changes in the Earth’s orbit, has been documented in earlier studies. However, higher frequency Holocene variability is not yet understood. Here we present high-resolution diatom assemblage data from two small Altiplano lakes, Lago Lagunillas and Lago Umayo, indicating changes in effective moisture in the southern tropical Andes at decadal, centennial and millennial timescales throughout the mid to late Holocene. A strong millennial-scale component, similar in …
Reef Foraminifera As Bioindicators Of Coral Reef Health: Low Isles Reef, Northern Great Barrier Reef, Australia, Jonathan D. Schueth, Tracy D. Frank
Reef Foraminifera As Bioindicators Of Coral Reef Health: Low Isles Reef, Northern Great Barrier Reef, Australia, Jonathan D. Schueth, Tracy D. Frank
Department of Earth and Atmospheric Sciences: Faculty Publications
Declining water quality associated with changes in land use over the past century is considered a significant environmental threat to the health of coral platforms of the Great Barrier Reef, Australia, in particular for those situated in nearshore areas of the wet tropics. Of these reefs, perhaps the most well known is Low Isles Reef, which has been studied since 1928. Decline in scleractinian coral cover and increased abundances of soft-bodied corals and macroalgae since the 1950’s have led researchers to speculate that the reef is being affected by increased nutrient and sediment fluxes from nearby rivers. The Foraminifera in …
Stratigraphic Imprint Of The Late Paleozoic Ice Age In Eastern Australia: A Record Of Alternating Glacial And Nonglacial Climate Regime, Christopher R. Fielding, Tracy D. Frank, Lauren P. Birgenheier, Michael C. Rygel, Andrew T. Jones, John Roberts
Stratigraphic Imprint Of The Late Paleozoic Ice Age In Eastern Australia: A Record Of Alternating Glacial And Nonglacial Climate Regime, Christopher R. Fielding, Tracy D. Frank, Lauren P. Birgenheier, Michael C. Rygel, Andrew T. Jones, John Roberts
Department of Earth and Atmospheric Sciences: Faculty Publications
Stratigraphic and sedimentological data from New South Wales and Queensland, eastern Australia, indicate that the Late Paleozoic Ice Age comprised at least eight discrete glacial intervals (each 1–8 Ma in duration, here termed “glaciations”), separated by nonglacial intervals of comparable duration. These events spanned an interval from mid-Carboniferous (c. 327 Ma) to the early Late Permian (c. 260 Ma), and illustrate a pattern of increasing climatic austerity and increasingly widespread glacial ice from initial onset until an acme in the late Early Permian, followed by an opposite trend towards the final demise of glaciation in the Late Permian. The alternating …
Whole-Stream Response To Nitrate Loading In Three Streams Draining Agricultural Landscapes, John H. Duff, Anthony J. Tesoriero, William B. Richardson, Eric A. Strauss, Mark Munn
Whole-Stream Response To Nitrate Loading In Three Streams Draining Agricultural Landscapes, John H. Duff, Anthony J. Tesoriero, William B. Richardson, Eric A. Strauss, Mark Munn
United States Geological Survey: Staff Publications
Physical, chemical, hydrologic, and biologic factors affecting nitrate (NO3-) removal were evaluated in three agricultural streams draining orchard/dairy and row crop settings. Using 3-d “snapshots” during biotically active periods, we estimated reachlevel NO3- sources, NO3- mass balance, in-stream processing (nitrification, denitrification, and NO3- uptake), and NO3- retention potential associated with surface water transport and ground water discharge. Ground water contributed 5 to 11% to stream discharge along the study reaches and 8 to 42% of gross NO3- input. Streambed processes potentially reduced 45 to 75% of ground …