Earth Sciences Commons^™

A Diatom-Based Reconstruction Of Drought Intensity, Duration, And Frequency From Moon Lake, North Dakota: A Sub-Decadal Record Of The Last 2,300 Years, Kathleen R. Laird, Sherilyn C. Fritz, Brian F. Cumming

Department of Earth and Atmospheric Sciences: Faculty Publications

Diatom assemblages preserved in sediment cores from closed-basin lakes can provide high-resolution records of past hydrologic and climatic conditions, including long-term patterns in the intensity, duration, and frequency of droughts. At Moon Lake, a closed-basin lake in eastern North Dakota, a comparison of diatom-inferred salinity and the precipitation-based Bhalme-Mooley Drought Index (BMDI) over the last 100 years was highly significant, suggesting that the diatom record contains a sensitive archive of past climatic conditions. A sub-decadal record of inferred salinity for the past 2300 years indicates that extreme droughts of greater intensity than those during the 1930s “Dust Bowl” were more …

Calcareous Nannofossil Paleogene Biostratigraphy Côte D'Ivoire-Ghana Marginal Ridge, Eastern Equatorial Atlantic, Samir Shafik, David K. Watkins, Im Chul Shin

Department of Earth and Atmospheric Sciences: Faculty Publications

Paleogene sections on the Côte d’Ivoire-Ghana Marginal Ridge in the eastern Atlantic Ocean, sampled at three sites during Ocean Drilling Program Leg 159, are shown to have calcareous nannofossil assemblages in distinct packages of (sub)zones separated by hiatuses or barren sediments. The packages are different at each of the sites; all fall within the interval from late Paleocene Zone CP6 to latest Oligocene Subzone CN1a inclusive. Three packages (CP9b–CP11, CP13, and CP19) on the crest of the Marginal Ridge at Site 960, four (CP7–CP9b, CP11, CP13–?CP15, and CP17–CN1a) at nearby Site 959 on the shoulder of the Marginal Ridge, and …

7. Thermal Diagenesis Of Cretaceous Sediment Recovered At The Cote D’Ivoire – Ghana Transform Margin, Mary Anne Holmes

Department of Earth and Atmospheric Sciences: Faculty Publications

The early opening of the South Atlantic ocean along the eastern Romanche Fracture Zone, including an initial phase of transform faulting and pull-apart basin formation, followed by the generation of a seafloor spreading center, was investigated during Ocean Drilling Program Leg 159 to the Côte d’Ivoire-Ghana continental margin. Clay minerals in the <0.5-μm fraction of tectonically disturbed sediment recovered during this leg were analyzed by X-ray diffraction to determine the extent of thermal diagenesis caused by the passing of the South Atlantic spreading center along this transform margin, and to date the passing. Results from Sites 959-961 reveal mild thermal alteration of clays, to paleotemperatures of 120°–170°C, in older, mostly undated sediment, in response to an elevated paleogeothermal gradient, as indicated by the absence of randomly interstratified illite/smectite group clays (R = 0 I/S clay), and the presence of dominant regularly interstratified (R = 1) I/S clay. Thermally altered sediment at these sites underlie unaltered sediment with likely erosional contacts. Based on a date of nannofossil biozone CC9b for the oldest unaltered sediment at Site 959, the thermal event there must have been pre-CC9b.
At Site 962, drilled on a minor marginal ridge to the west of Sites 959–961, heat has altered clay in basal sediment to R = 1 I/S, and the transition uphole to thermally unaltered sediment, bearing R = 0 I/S clay, was recovered over a 175-m-thick interval, indicating …

Mesozoic Biostratigraphic, Paleoenvironmental, And Paleobiogeographic Synthesis, Equatorial Atlantic, M. Moullade, David K. Watkins, F. E. Oboh-Ikuenobe, J.-P. Bellier, E. Masure, A. E.L. Holbourn, J. Erbacher, W. Kuhnt, T. Pletsch, M. A. Kaminski, R. Rauscher, S. Shafik, O. Yepes, J. Dejax, J. M. Gregg, Im Chul Shin, M. Schuler

Department of Earth and Atmospheric Sciences: Faculty Publications

Cretaceous sediments from Ocean Drilling Program Leg 159 on the Côte d’Ivoire-Ghana Marginal Ridge (CIGMR), eastern equatorial Atlantic, are characterized by distinct stratigraphic changes in sedimentary facies associated with changes in the composition of the clayey and organic fractions, as well as of the calcareous nannofossil, radiolarian, foraminiferal, and palynomorph assemblages. In the absence of reliable magnetostratigraphic information, an integrated biostratigraphy provides the only means used to calibrate the geologic history of the Leg 159 area.

The existence of marine depositional environments as early as the late Aptian to early Albian close to the Leg 159 drill sites puts constraints …

Evolution Of The Aeluroid Carnivora: Diversity Of The Earliest Aeluroids From Eurasia (Quercy, Hsanda-Gol) And The Origin Of Felids, Robert M. Hunt Jr.

Department of Earth and Atmospheric Sciences: Faculty Publications

The oldest known fossil aeluroids are from Lower Oligocene sediments in France (Quercy) and Upper Eocene-Lower Oligocene sediments in Mongolia. These small (< 5 kg) carnivorans are primarily represented by mandibles, with hypercarnivorous dentitions in almost all lineages. The six aeluroid genera from France and those from Mongolia share a common dental pattern despite their geographic separation near the extremes of the Eurasian landmass. This similarity is not surprising, however, because faunal exchange across Eurasia at this time is documented not only by populations of small aeluroids but also by small arctoid carnivorans. Basicrania of Oligocene aeluroids are preserved only in the Quercy deposits. The auditory regions of two genera from Quercy (Palaeoprionodon, Stenoplesictis), and of two additional aeluroid genera (Stenogale, Proailurus) known only from mandibles at Quercy (but matched with congeneric mandibles with associated basicrania from early Miocene sediments at St.-Gerand), reveal a common basicranial morphotype. The living African palm civet Nandinia binotata retains a basicranial and auditory anatomy closely approaching the ancestral aeluroid morphotype. European paleontologists working with the Quercy faunas have regarded several of these aeluroids as early members of the Viverridae and …

Cadmium Malonate Complexation In Aqueous Sodium Trifluoromethanesulfonate Media To 75°C; Including Dissociation Quotients Of Malonic Acid, Moira K. Ridley, Donald A. Palmer, David J. Wesolowski, Richard Kettler

Department of Earth and Atmospheric Sciences: Faculty Publications

The molal formation quotients for cadmium-malonate complexes were measured potentiometrically from 5 to 75°C, at ionic strengths of 0.1, 0.3, 0.6 and 1.0 molal in aqueous sodium trifluoromethanesulfonate (NaTf) media. In addition, the stepwise dissociation quotients for malomc acid were measured in the same medium from 5 to 100°C, at ionic strengths of 0.1, 0.3, 0.6, and 1.0 molal by the same method. The dissociation quotients for malonic acid were modeled as a function of temperature and ionic strength with empirical equations formulated such that the equilibrium constants at infinite dilution were consistent, within the error estimates, with the malonic …

Dissociation Constants Of Oxalic Acid In Aqueous Sodium Chloride And Sodium Trifluoromethanesulfonate Media To 175 °C, Richard Kettler, David J. Wesolowski, Donald A. Palmer

Department of Earth and Atmospheric Sciences: Faculty Publications

The first and second molal dissociation constants of oxalic acid were measured potentiometrically in a concentration cell fitted with hydrogen electrodes. Measurements were made at six temperatures ranging from 5 °C to 125 °C at four ionic strengths ranging from 0.1 mol•kg^-1 to 1.0 mol•kg^-1 (NaCl and NaCF₃-SO₃). The second molal dissociation constant was measured in NaCF₃SO₃ media only. The data obtained in this study were combined with the corresponding literature values, including a number of recalculated Harned cell and concentration cell measurements and previous results from this laboratory. Data for …

Upper Cenozoic Calcareous Nannofossil Biostratigraphy Côte D'Ivoire-Ghana Margin, Eastern Equatorial Atlantic, Samir Shafik, David K. Watkins, Im Chul Shin

Department of Earth and Atmospheric Sciences: Faculty Publications

The distribution of calcareous nannofossils in the upper Cenozoic sections sampled at four sites in the eastern equatorial Atlantic Ocean during Ocean Drilling Program (ODP) Leg 159 is documented here. A virtually complete upper Cenozoic sequence of nannofossil (sub)zones is identified at Site 959 on the shoulder of the Côte d’Ivoire-Ghana marginal ridge, with proxies for the rare marker species being employed. Hiatuses within the middle and upper Miocene are detected at two other sites on the same ridge, being more clearly defined at Site 960 on the crest of the ridge. Two of these hiatuses are of regional significance. …

Calcareous Nannofossils From The Cretaceous Of The Deep Ivorian Basin, David K. Watkins, Samir Shafik, Im Chul Shin

Department of Earth and Atmospheric Sciences: Faculty Publications

Micropaleontological investigation of four sites drilled by Ocean Drilling Program Leg 159 on the Côte d’Ivoire-Ghana Margin indicates that the initial invasion of oceanic surface waters into the Deep Ivorian Basin, as indicated by the presence of calcareous nannofossils, occurred during the late Albian. The nature of these assemblages suggests that these first Cretaceous oceanic surface waters were warm and relatively high in nutrients. These upper Albian sediments were deposited prior to significant tectonism at some of the sites, as indicated by their structurally deformed nature. The likely age of this tectonism is Cenomanian. The Upper Cretaceous consists of condensed …

High-Resolution Pliocene–Pleistocene Biostratigraphy Of Site 959, Eastern Equatorial Atlantic Ocean, Im Chul Shin, Samir Shafik, David K. Watkins

Department of Earth and Atmospheric Sciences: Faculty Publications

High-resolution calcareous nannofossil biostratigraphy was examined from Cores 159-959C-1H through 8H in 20-cm intervals for the Ocean Drilling Program in the eastern equatorial Atlantic Ocean. Well-preserved marker species occur continuously and are relatively abundant in Hole 959C. Six zones (CN10 through CN15) are identified. All calcareous nannofossils are well preserved. Late Neogene (Pliocene–Pleistocene) sediment is dominated by Florisphaera profunda, Gephyrocapsa caribbeanica, G. oceanica, Gephyrocapsa spp., Reticulofenestra pseudoumbilica, R. minutula, and small Reticulofenestra. The sedimentation rate varies from 0.4 cm/k.y. to 13.5 cm/k.y. This strong variations are related to disconformities. The lowest sedimentation rate occurs in the early late …

Oligocene To Early Miocene Silicoflagellates From The Ivorian Basin, Eastern Equatorial Atlantic, Site 959, Maija E. Schellpeper, David K. Watkins

Department of Earth and Atmospheric Sciences: Faculty Publications

Silicoflagellate biostratigraphy and relative abundance were determined for Site 959 in the eastern equatorial Atlantic. Five silicoflagellate zones, Corbisema apiculata, Naviculopsis biapiculata, Naviculopsis lata, Naviculopsis ponticula, and Corbisema triacantha Zones, were used with the Distephanus speculum hemisphaericus Subzone occurring in the N. biapiculata Zone. The Naviculopsis quadrata Zone is missing between the N. ponticula and N. lata Zones, indicating a hiatus in the lower Miocene cores that corresponds to hiatus NH1. Silicoflagellate relative abundance was graphed as a measure of paleoproductivity for Hole 959A. One large pulse of productivity occurred in the latest early Miocene, right before silica deposition …

4. Grain-Size Distribution And Significance Of Clay And Clay-Sized Minerals In Eocene To Holocene Sediments From Sites 918 And 919 In The Irminger Basin, Kraig Heiden, Mary Anne Holmes

Department of Earth and Atmospheric Sciences: Faculty Publications

Published by the Ocean Drilling Program, Texas A & M University, in cooperation with the National Science Foundation and Joint Oceanographic Institutions, Inc."

9. Alteration Of Uppermost Lavas And Volcaniclastics Recovered During Leg 152 To The East Greenland Margin, Mary Anne Holmes

Department of Earth and Atmospheric Sciences: Faculty Publications

During the last stages of the eruption of syn-rift basalts along the East Greenland Margin, debris flows and/or pyroclastic deposits were emplaced at Ocean Drilling Program Sites 915 and 916. The deposits and the tops of the lava flows at Site 918 were altered by subaerial weathering processes as indicated by downhole changes in mineral and chemical composition, and by the mineral paragenesis. Kaolinite and goethite, which form in acidic waters, are abundant at the tops of the weathering profiles and decrease in abundance downward. They are replaced by a smectite-hematite-opal assemblage at the bases of the weathered profiles. Gibbsite …

Average Steady Nonuniform Flow In Stratified Formations, Peter Indelman, Vitaly A. Zlotnik

Department of Earth and Atmospheric Sciences: Faculty Publications

A mathematical model of average nonuniform flow in heterogeneous stratified media is developed. The averaged Darcy's law is obtained by deriving the analytical expression of the effective conductivity tensor for media with small heterogeneities. The fundamental solution of the average flow equation (mean Green function) corresponding to the flow toward a single point source of deterministic discharge is derived. The mean head distribution is calculated for a fully penetrating well, for a finite length well in an infinite domain, and for a dipole well. The concept of equivalent conductivity is defined for use in identifying the formation conductivity properties. The …

Surface Textural Analysis Of Quartz Sand Grains From Odp Site 918 Off The Southeast Coast Of Greenland Suggests Glaciation Of Southern Greenland At 11 Ma, P. E. Helland, Mary Anne Holmes

Department of Earth and Atmospheric Sciences: Faculty Publications

Shipboard analysis of the 1,183-m sedimentary section recovered at Site 918 in the Irminger Basin during Ocean Drilling Program Leg 152 revealed material of glacial origin (diamictons, ice-rafted debris (IRD) and dropstones) as deep as 543 m below sea floor (bsf). The sediment containing the deepest dropstone was biostratigraphically dated shipboard as approximately 7 Ma, pushing back the date for the onset of glaciation on southern Greenland by 5 Ma. Thin layers of fine sand were found as much as 60 m deeper in the core, raising the possibility of an even earlier date for glaciation. To determine the sedimentary …

Effect Of Sulfate On The Release Rate Of Al3+ From Gibbsite In Low-Temperature Acidic Waters, Moira K. Ridley, David J. Wesolowski, Donald A. Palmer, Pascale Bénézeth, Richard Kettler

Department of Earth and Atmospheric Sciences: Faculty Publications

Solubility experiments were performed at 5 °C by reacting 1 g of powdered gibbsite with 45 g of aqueous H₂SO₄-NaCl and HCl-NaCl (0.01 m H+) solutions at 0.1 m ionic strength. The kinetics of dissolution were monitored under extremely undersaturated conditions and appeared to favor a zero-order rate-determining process. The dissolution rate of gibbsite in the sulfate solution was approximately 10 times faster than in the HCl solution, which is consistent with trends reported in the literature for studies performed at higher temperatures. The enhanced dissolution kinetics of gibbsite (and by analogy, other aluminum-containing minerals) in …

Ground Water, Robert F. Diffendal Jr.

Department of Earth and Atmospheric Sciences: Faculty Publications

A geologic overview of the groundwater supply underlying Cheyenne County, Nebraska (1997).

Geology, Robert F. Diffendal Jr.

Department of Earth and Atmospheric Sciences: Faculty Publications

An overview of the geology of Cheyenne County, Nebraska.

Relations Between Directional Spectral Vegetation Indices And Leaf Area And Absorbed Radiation In Alfalfa, Elizabeth Walter-Shea, Jeffrey L. Privette, D. Cornell, Mark A. Mesarch, C. Hays

Department of Earth and Atmospheric Sciences: Faculty Publications

s ensors on satellite platforms with extreme view angles have been increasingly used to analyze regional and global vegetation cover and productivity because of frequent observations. This study, using experimental and theoretical methods, analyzed variations in vegetation indices with sun-view geometry as a means of understanding the sensitivity of relations beween vegetation indices and the biophysical properties, the leaf area index (LAI), and the instantaneous fraction of absorbed photosynthetically active radiation (fAPAR). Canopy bidirectional reflectance factors (BRFs) of an alfalfa crop were measured and simulated at a variety of solar and view zenith angles. Also, fAPAR, LAI, and leaf optical …

Application Of Permutations To Lossless Compression Of Multispectral Thematic Mapper Images, Ziya Arnavut, Sunil Narumalani

Department of Earth and Atmospheric Sciences: Faculty Publications

The goal of data compression is to find shorter representa- tions for any given data. In a data storage application, this is done in order to save storage space on an auxiliary device or, in the case of a communication scenario, to increase channel throughput. Because re- motely sensed data require tremendous amounts of transmission and storage space, it is essential to find good algorithms that utilize the spa- tial and spectral characteristics of these data to compress them. A new technique is presented that uses a spectral and spatial correlation to create orderly data for the compression of multispectral …

Boundary Conditions For Convergent Radial Tracer Tests And Effect Of Well Bore Mixing Volume, Vitaly A. Zlotnik, John David Logan

Department of Earth and Atmospheric Sciences: Faculty Publications

Convergent radial flow tracer tests have a complex spatial nonaxial transport structure caused by the flow in the vicinity of the injection well and its finite mixing volume. The formulation of the boundary value problem, and especially the treatment of the boundary conditions at the injection well, is nontrivial. Hodgkinson and Lever [1983], Moench [1989, 1991], and Welty and Gelhar [1994] have developed different models and methods for the analysis of breakthrough curves in the extraction well. To extend interpretation techniques to breakthrough curves in the zone between injection and extraction wells, an analysis of conventional transport models is given, …

Theory Of Dipole Flow In Uniform Anisotropic Aquifers, Vitaly A. Zlotnik, Glenn Ledder

Department of Earth and Atmospheric Sciences: Faculty Publications

A theory of dipole flow is developed to model flow induced by a vertical circulation well consisting of injection and extraction chambers in a single borehole. Included in the theory are an analytical description of the kinematic flow structure around a vertical circulation well and the drawdown in the well chambers. Using Stokes’ stream function, simple criteria are derived to determine the region of intensive recirculation. This region extends (from the dipole center) approximately five distances between chamber centers in the radial direction and two distances between chamber centers in both vertical directions. The vertical scale does not depend on …

Paleolimnological Records Of Climatic Change In North America, Sherilyn C. Fritz

Department of Earth and Atmospheric Sciences: Faculty Publications

Lacustrine fossil records provide long time series of data on limnological and climatic conditions; these data are useful for establishing natural patterns of climate variability and for generating testable hypotheses about atmospheric circulation and climate-ecosystem linkages. Shoreline features can indicate past lake-level fluctuations that may reflect changes in moisture balance, but often these records are discontinuous and are evidence of only extreme conditions. The organisms, geochemistry, and sedimentology of lake sediments may provide a more continuous sequence of direct and indirect lake-climate interactions in the past. The most clearly interpretable paleolimnnological records of climatic change are those that use several …

Century-Scale Paleoclimatic Reconstruction From Moon Lake, A Closed-Basin Lake In The Northern Great Plains, Kathleen R. Laird, Sherilyn C. Fritz, Eric C. Grimm, Pietra G. Mueller

Department of Earth and Atmospheric Sciences: Faculty Publications

Estimates of past lake-water salinity from fossil diatom assemblages were used to infer past climatic conditions at Moon Lake, a climatically sensitive site in the northern Great Plains. A good correspondence between diatom-inferred salinity and historical records of mean annual precipitation minus evapotranspiration (P - ET) strongly suggests that the sedimentary record from Moon Lake can be used to reconstruct past climatic conditions. Century-scale analysis of the Holocene diatom record indicates four major hydrological periods: an early Holocene transition from an open freshwater system to a closed saline system by 7300 B.P., which corresponds with a transition from spruce forest …

Linking Planktonic Diatoms And Climate Change In The Large Lakes Of The Yellowstone Ecosystem Using Resource Theory, Susan S. Kilham, Edward C. Theriot, Sherilyn C. Fritz

Department of Earth and Atmospheric Sciences: Faculty Publications

Resource-based physiology of the eight important planktonic diatom species in the large lakes of the Yellowstone region can be used to explain their relative abundances and seasonal changes. The diatoms are ranked along resource ratio gradients according to their relative abilities to grow under limitation by Si, N, P, and light. Hypotheses based on resource physiology can be integrated with observations on seasonal changes in diatom assemblages to explain the present distributions of diatoms and to test the causal factors proposed to explain diatom distributions over the Holocene. Knowledge of the limnology of these lakes and process-oriented physiology provide the …

Geology Beneath The Primary Management Systems Evaluation Area (Msea) Site Southwest Of Shelton, Buffalo County, Nebraska, Robert F. Diffendal Jr., Frank A. Smith

Department of Earth and Atmospheric Sciences: Faculty Publications

In 1990, as part of a national presidential initiative on water quality, researchers from the University of Nebraska-Lincoln (UNL) Institute of Agriculture and Natural Resources (IANR) received a multi-year grant from the United States Department of Agriculture, Cooperative State Research Service, to study management of irrigated com and soybeans to minimize groundwater contamination. D.G. Watts, R.F. Spalding, and J.S. Schepers, of the IANR led a study at one of the Management Systems Evaluation Areas (MSEA). This area was made up of two sites, a primary site on a terrace of the Platte River near Shelton and a secondary site nearer …

Upper Cretaceous Calcareous Nannofossil Biostratigraphy And Paleoceanography Of The Southern Ocean, David K. Watkins, Sherwood W. Wise Jr., James J. Popsichal, Jason Crux

Department of Earth and Atmospheric Sciences: Faculty Publications

Nannofossil data from the Naturaliste Plateau (DSDP Legs 26 & 28), Falkland Plateau (DSDP Legs 36 & 71), Maud Rise (ODP Leg 113), Northeast Georgia Rise (ODP Leg 114), and Kerguelen Plateau (ODP Leg 120) yield a set of consistent, reliable biohorizons that form the basis of a revised calcareous nannofossil zonation for the Southern Ocean Upper Cretaceous. Analysis of this zonation indicates significant changes in the circum-Antarctic climatic regime during the Campanian and Maastrichtian that foreshadow the more dramatic climatic shifts of the Palaeogene. Calcareous nannofossils from the Turonian through the Lower Campanian of the studied sections are characterized …

Estimation And Abundances In Two-Component Mineral Mixtures Using Mid-Infrared Laser Reflectance Ratios, Ram M. Narayanan, Kristin K. Warner, Robert F. Diffendal Jr.

Department of Earth and Atmospheric Sciences: Faculty Publications

The mid-infrared spectral region (8-14 μm wavelength) is emerging as a viable geologic remote sensing tool due to the presence of reststrahlen bands for minerals such as silicates and carbonates. An experimental study was carried out to characterize the mid-infrared laser reflectance of mineral mixtures, and to explore the potential of laser remote sensing systems to estimate mineral abundances in two-component mixtures. An empirical model was developed to establish a relationship between laser reflectance ratios at judiciously selected wavelengths and percentage of one of the minerals in the mixture. It was found that the abundances can be estimated to within …

Book Review: Quaternary Geology And Geomorphology Of South America By C. Clapperton, William J. Wayne

Department of Earth and Atmospheric Sciences: Faculty Publications

Dr. Clapperton is to be commended for having taken on the monumental task of a review of the present state of knowledge of the Quaternary of the entire continent of South America. Quaternary Geology and Geomorphology of South America is a massive, interestingly written, but expensive volume that covers exactly what its title suggests. In spite of the paucity of information on many aspects of the Quaternary geology of this continent, which extends from north of the equator nearly to the Antarctic, the author has succeeded in reviewing and synthesizing most of the material that does exist. To do so …

Patterns Of Early Lake Ontogeny In Glacier Bay As Inferred From Diatom Assemblages, Sherilyn C. Fritz, Daniel R. Engstrom

Department of Earth and Atmospheric Sciences: Faculty Publications

We studied a series of recently formed lakes along a deglaciation chronosequence in Glacier Bay National Park to examine changes in water chemistry, primary production, and biotic composition that accompany the early ontogeny of north-temperate lakes. Successional trends in these freshwater ecosystems have been explored with a two-tiered approach that includes (1) the comparison of limnological conditions among lakes of known age and in different stages of primary catchment succession, and (2) the inference of water-chemistry trends in individual sites based on fossil diatom stratigraphy. This paper emphasizes the reconstruction of limnological trends from fossil diatom assemblages. The modem distribution …