Earth Sciences Commons^™

Quantification Of Salt Dust Pathways From A Groundwater-Fed Lake: Implications For Solute Budgets And Dust Emission Rates, Vitaly A. Zlotnik, John B. Ong, John D. Lenters, Jens Schmieder, Sherilyn C. Fritz

Department of Earth and Atmospheric Sciences: Faculty Publications

Emissions of salt dust from the shores of saline lakes significantly impact lake chemistry, air quality, transportation, human health, and climate. Quantitative methods for assessing these emissions, however, are still in the developmental stage. We investigate salt pathways from groundwater to dust using an approach that takes advantage of opportune conditions at a groundwater-fed, saline lake in the Nebraska Sand Hills region. The mass of salt in the lakeshore surface crust and soil was measured, as well as in the dust on the surrounding dune field. These data, together with information on the lake hydrology, show that dust emission is …

Trends In Record-Breaking Temperatures For The Conterminous United States, Clinton M. Rowe, Logan E. Derry

Department of Earth and Atmospheric Sciences: Faculty Publications

In an unchanging climate, record-breaking temperatures are expected to decrease in frequency over time, as established records become increasingly more difficult to surpass. This inherent trend in the number of record-breaking events confounds the interpretation of actual trends in the presence of any underlying climate change. Here, a simple technique to remove the inherent trend is introduced so that any remaining trend can be examined separately for evidence of a climate change. As this technique does not use the standard definition of a broken record, our records* are differentiated by an asterisk. Results for the period 1961– 2010 indicate that …

Rinded Iron-Oxide Concretions: Hallmarks Of Altered Siderite Masses Of Both Early And Late Diagenetic Origin, David Loope, Richard Kettler, Karrie A. Weber, Nathan L. Hinrichs, Derek T. Burgess

Department of Earth and Atmospheric Sciences: Faculty Publications

Iron-bearing concretions are valuable records of oxidation states of subsurface waters, but the first concretions to form can be altered drastically during later diagenetic events. Distinctive concretions composed of heavy rinds of iron oxide that surround iron-poor, mud-rich cores are common along bases of fluvial cross-bed sets of the Cretaceous Dakota Formation, Nebraska, USA. Concretion rinds thicken inward and cores contain 46 to 89% void space. Millimeter-scale spherosiderites are abundant in palaeosols that developed in floodplain facies. Evolution of rinded concretions began when intraformational clasts were eroded from sideritic soils, transported, abraded and deposited in river channels. Alteration of siderite …

Climate-Induced Changes In Lake Ecosystem Structure Inferred From Coupled Neo- And Paleoecological Approaches, Jasmine E. Saros, Jeffery R. Stone, Gregory T. Pederson, Krista E.H. Slemmons, Trisha Spanbauer, Anna Schliep, Douglas Cahl, Craig E. Williamson, Daniel R. Engstrom

Department of Earth and Atmospheric Sciences: Faculty Publications

Over the 20th century, surface water temperatures have increased in many lake ecosystems around the world, but long-term trends in the vertical thermal structure of lakes remain unclear, despite the strong control that thermal stratification exerts on the biological response of lakes to climate change. Here we used both neo- and paleoecological approaches to develop a fossil-based inference model for lake mixing depths and thereby refine understanding of lake thermal structure change. We focused on three common planktonic diatom taxa, the distributions of which previous research suggests might be affected by mixing depth. Comparative lake surveys and growth rate experiments …

Calcareous Nannofossil Assemblage Changes Across The Paleocene–Eocene Thermal Maximum: Evidence From A Shelf Setting, Jean M. Self-Trail, David S. Powars, David K. Watkins, Gregory A. Wandless

Department of Earth and Atmospheric Sciences: Faculty Publications

Biotic response of calcareous nannoplankton to abrupt warming across the Paleocene/Eocene boundary reflects a primary response to climatically induced parameters including increased continental runoff of freshwater, global acidification of seawater, high sedimentation rates, and calcareous nannoplankton assemblage turnover. We identify ecophenotypic nannofossil species adapted to low pH conditions (Discoaster anartios, D. araneus, Rhomboaster spp.), excursion taxa adapted to the extremely warm climatic conditions (Bomolithus supremus and Coccolithus bownii), three species of the genus Toweius (T. serotinus, T. callosus, T. occultatus) adapted to warm, rather than cool, water conditions, opportunists adapted to high productivity conditions (Coronocyclus bramlettei, …

Hydraulic Conductivity Of The High Plains Aquifer Re-Evaluated Using Surface Drainage Patterns, Wei Luo, Darryll T. Pederson

Department of Earth and Atmospheric Sciences: Faculty Publications

The High Plains Aquifer (HPA), underlying parts of 8 states from South Dakota to Texas, is one of the largest fresh water aquifers in the world and accounts for 30% of the groundwater used for irrigation in the US. Determining the distribution of HPA’s hydraulic conductivity (K) is critical for water management and addressing water quality issues. K is traditionally estimated from well pumping data coupled with computer modeling and is known to be highly variable, spanning several orders of magnitude for the same type of rock. Here we show that applying our innovative method of determining effective …

Progressive Abandonment And Planform Changes Of The Central Platte River In Nebraska, Central Usa, Over Historical Timeframes, John D. Horn, R. Matthew Joeckel, Christopher R. Fielding

Department of Earth and Atmospheric Sciences: Faculty Publications

This paper presents data compiled from aerial photography, General Land Office maps (GLOs), and discharge data from the central Platte River in Nebraska that quantify and provide a new understanding of channel evolution and abandonment in a braided stream. Analyses of aerial photographs and GLOs in ArcMap™ show that channel area decreased by an average of 46% from 1938 to 2006 and that channel widths in 1858 were an average of 539% greater than in 2006. Annual discharge during 1942–2006 does not show a clear long-term relationship with the decrease in channel width and area. Rather, stabilization through vegetation of …

Improving Student Attitudes About Learning Science And Student Scientific Reasoning Skills, Douglas K. Duncan, Leilani Arthurs

Department of Earth and Atmospheric Sciences: Faculty Publications

Student attitudes about learning science and student ideas about the nature of science were compared at the end of two astronomy courses taught in Fall 2007, a course with a traditional astronomy curriculum and a transformed course, whose traditional astronomy curriculum was supplemented by an embedded curriculum that explicitly addressed the nature of science and student metacognition (i.e., thinking about one’s own thinking.) The embedded curriculum in the transformed course gave students practice at evaluating examples of valid science and pseudoscience found on the internet; it also provided students opportunities to discuss what they think about learning science. Student attitudes …

Top-Down Estimate Of Dust Emissions Through Integration Of Modis And Misr Aerosol Retrievals With The Geos-Chem Adjoint Model, Jun Wang, Xiaoguang Xu, Daven K. Henze, Jing Zeng, Qiang Ji, Si-Chee Tsay, Jianping Huang

Department of Earth and Atmospheric Sciences: Faculty Publications

Predicting the influences of dust on atmospheric composition, climate, and human health requires accurate knowledge of dust emissions, but large uncertainties persist in quantifying mineral sources. This study presents a new method for combined use of satellite-measured radiances and inverse modeling to spatially constrain the amount and location of dust emissions. The technique is illustrated with a case study in May 2008; the dust emissions in Taklimakan and Gobi deserts are spatially optimized using the GEOSChem chemical transport model and its adjoint constrained by aerosol optical depth (AOD) that are derived over the downwind dark-surface region in China from MODIS …

Holocene Seasonal Variability Inferred From Multiple Proxy Records From Crevice Lake, Yellowstone National Park, Usa, Cathy Whitlock, Walter E. Dean, Sherilyn C. Fritz, Lora R. Stevens, Jeffery R. Stone, Mitchell J. Power, Joseph R. Rosenbaum, Kenneth L. Pierce, Brandi B. Bracht-Flyr

Department of Earth and Atmospheric Sciences: Faculty Publications

A 9400-yr-old record from Crevice Lake, a semi-closed alkaline lake in northern Yellowstone National Park, was analyzed for pollen, charcoal, geochemistry, mineralogy, diatoms, and stable isotopes to develop a nuanced understanding of Holocene environmental history in a region of northern Rocky Mountains that receives both summer and winter precipitation. The limited surface area, conical bathymetry, and deep water (>31 m) of Crevice Lake create oxygen-deficient conditions in the hypolimnion and preserve annually laminated sediment (varves) for much of the record. Pollen data indicate that the watershed supported a closed Pinus-dominated forest and low fire frequency prior to 8200 …

Does Gender Bias Influence Awards Given By Societies?, Mary Anne Holmes, Pranoti Asher, John Farrington, Rana Fine, Margaret S. Leinen, Phoebe Leboy

Department of Earth and Atmospheric Sciences: Faculty Publications

AGU is a participant in a U.S. National Science Foundation (NSF)–funded project called Advancing Ways of Awarding Recognition in Disciplinary Societies (AWARDS), which seeks to examine whether gender bias affects selection of recipients of society awards. AGU is interested in learning why there is a higher proportion of female recipients of service and education awards over the past 2 decades. Combined with a lower rate of receipt of research awards, these results suggest that implicit (subconscious) bias in favor of male candidates still influences awardee selection.

Six other professional societies (American Chemical Society, American Mathematical Society, American Society of Anesthesiologists, …

The Pennsylvanian–Permian Transition In The Low-Latitude Carbonate Record And The Onset Of Major Gondwanan Glaciation, Jesse Koch, Tracy D. Frank

Department of Earth and Atmospheric Sciences: Faculty Publications

Recent studies suggest a marked expansion of glacial ice across much of Gondwana beginning in the earliest Permian. Because expansion of glacial ice results in a lowering of sea level, the imprint of ice expansion should be evident worldwide as significant exposure event, hiatuses, or other evidence for sea level drop at or near the Pennsylvanian–Permian boundary. This literature review investigates the signature of an Early Permian expansion of Gondwanan ice through examination of stratigraphic records from eight carbonate-dominated, palaeotropical regions across Pangaea. Tropical carbonate environments are used because most form in tectonically quiescent regions and are sensitive indicators of …

Environmental History Of A Closed-Basin Lake In The Us Great Plains: Diatom Response To Variations In Groundwater Flow Regimes Over The Last 8500 Cal. Yr Bp, William O. Hobbs, Sherilyn C. Fritz, Jeffery R. Stone, Joseph J. Donovan, Eric C. Grimm, James E. Almendinger

Department of Earth and Atmospheric Sciences: Faculty Publications

Sediment records from closed-basin lakes in the Northern Great Plains (NGP) of North America have contributed significantly to our understanding of regional paleoclimatology. A high-resolution (near decadal) fossil diatom record from Kettle Lake, ND, USA that spans the last 8500 cal. yr BP is interpreted in concert with percent abundance of aragonite in the sediment as an independent proxy of groundwater flow to the lake (and thus lake water level). Kettle Lake has been relatively fresh for the majority of the Holocene, likely because of the coarse substrata and a strong connection to the underlying aquifer. Interpretation of diatom assemblages …

The Collaborative Colorado– Nebraska Unmanned Aircraft System Experiment, Adam L. Houston, Brian Argrow, Jack Elston, Jamie Lahowetz, Eric W. Frew, Patrick C. Kennedy

Department of Earth and Atmospheric Sciences: Faculty Publications

Unmanned aircraft (UA) can provide observations of atmospheric phenomena that are either difficult or impossible to obtain with existing platforms. It is for this reason that facilitating the maturation of this relatively new technology has become a high priority in the atmospheric sciences. This position is reflected in the 2007 National Research Council Decadal Survey, which states that unmanned aircraft technology “should be increasingly factored into the nation’s strategic plan for Earth science” (National Research Council 2007, p. 14). Moreover, the fiscal year 2008 budget for the National Oceanic and Atmospheric Administration (NOAA) featured an increased investment in unmanned aircraft …

Abrupt Holocene Climate Change As An Important Factor For Human Migration In West Greenland, William J. D'Andrea, Yongsong Huang, Sherilyn C. Fritz, N. John Anderson

Department of Earth and Atmospheric Sciences: Faculty Publications

West Greenland has had multiple episodes of human colonization and cultural transitions over the past 4,500 y. However, the explanations for these large-scale human migrations are varied, including climatic factors, resistance to adaptation, economic marginalization, mercantile exploration, and hostile neighborhood interactions. Evaluating the potential role of climate change is complicated by the lack of quantitative paleoclimate reconstructions near settlement areas and by the relative stability of Holocene temperature derived from ice cores atop the Greenland ice sheet. Here we present high-resolution records of temperature over the past 5,600 y based on alkenone unsaturation in sediments of two lakes in West …

Taxonomic Composition, Paleoecology And Biostratigraphy Of Late Cretaceous Diatoms From Devon Island, Nunavut, Canadian High Arctic, Jakub Witkowski, David M. Harwood, Karen Chin

Department of Earth and Atmospheric Sciences: Faculty Publications

Upper Cretaceous sediments of the Kanguk Formation exposed in Eidsbotn and Viks Fiord grabens on Devon Island, Nunavut, Canadian High Arctic, yielded 91 fossil marine diatom species and varieties (including indeterminate taxa), representing 41 genera. Excellent preservation of the assemblages was aided by shallow burial, protection in down­faulted linear grabens, and the presence of abundant volcanic material. Planktonic species and resting spores com­prise nearly 70% of the diatom assemblage, and provided abundant food resources for the Late Cretaceous Arctic eco­system. Deposition of the approximately 225 m-thick stratigraphic sequence was predominantly in a shallow marine neritic setting, with an upward progression …

Late Pleistocene Paleohydrography And Diatom Paleoecology Of The Central Basin Of Lake Malawi, Africa, Jeffery R. Stone, Karlyn S. Westover, Andrew S. Cohen

Department of Earth and Atmospheric Sciences: Faculty Publications

Analysis of sedimentary diatom assemblages (10 to 144 ka) form the basis for a detailed reconstruction of the paleohy­drography and diatom paleoecology of Lake Malawi. Lake-level fluctuations on the order of hundreds of meters were in­ferred from dramatic changes in the fossil and sedimentary archives. Many of the fossil diatom assemblages we observed have no analog in modern Lake Malawi. Cyclotelloid diatom species are a major component of fossil assemblages prior to 35 ka, but are not found in significant abundances in the modern diatom communities in Lake Malawi. Salinity- and alkalin­ity-tolerant plankton has not been reported in the modern …

Aragonite Loss In A Cold-Water Coral Mound: Mechanisms And Implications, Tracy D. Frank, Jürgen Titschack, Mieke Thierens

Department of Earth and Atmospheric Sciences: Faculty Publications

Selective dissolution of aragonitic grains is emerging as a volumetrically significant process that affects a broad range of modern carbonate settings. This study explores mechanisms and implications of aragonite loss in Challenger Mound, a giant cold-water coral (Lophelia pertusa) mound of Pleistocene age, which lies on the continental slope off southwest Ireland. A comprehensive sampling scheme allowed the integration of petrographic data with geochemical analyses of sediment and pore water. The mound remains virtually unlithified and consists of stacked, fining-upward cycles of silty coral floatstone–rudstone and bafflestone grading into wackestone. Whereas calcitic grains appear unaltered, aragonitic grains are …

Late Cretaceous To Recent Deformation Related To Inherited Structures And Subsequent Compression Within The Persian Gulf: A 2d Seismic Case Study, Caroline M. Burberry, C. A.-L. Jackson, J. W. Cosgrove

Department of Earth and Atmospheric Sciences: Faculty Publications

The Persian Gulf is part of an asymmetric foreland basin related to the Zagros Orogen. Few published studies of this basin and associated onshore areas include seismic reflection data. We present a seismic-stratigraphic interpretation based on marine 2D seismic data, which reveals the presence of two types of compressional structures within the basin: (1) faulted domes related to salt movement and the offshore trace of a NNE–SSW-trending dextral basement fault (the Kazerun Fault); (2) long-wavelength (16 km), low-amplitude (60 ms two-way travel time) folds relating to the advancing deformation front associated with the orogen. Thinning of age-constrained stratal units across …

Dissolved Organic Matter Composition And Photoreactivity In Prairie Lakes Of The U.S. Great Plains, Christopher L. Osburn, Courtney R. Wigdahl, Sherilyn C. Fritz, Jasmine E. Saros

Department of Earth and Atmospheric Sciences: Faculty Publications

Dissolved organic matter (DOM) of 27 prairie saline lake ecosystems was investigated in the Northern and Central Great Plains of the United States using absorbance, fluorescence, lignin concentration, and stable C isotope values. The majority of variation in DOM fluorescence among lakes was due to humic (peak C) and microbially formed (peak M) fluorescent components, which appear to be derived from autochthonous primary production. Strong correlations between peak M and nutrients allow us to model total phosphorus (TP) concentration using peak M fluorescence and chromophoric dissolved organic matter (CDOM) absorption. The rate of primary production (PP) was positively correlated with …

A Regional-Scale Climate Reconstruction Of The Last 4000 Years From Lakes In The Nebraska Sand Hills, Usa, Jens Schmieder, Sherilyn C. Fritz, James B. Swinehart, Avery L. C. Shinneman, Alexander P. Wolfe, Gifford Miller, N. Daniels, K. C. Jacobs, Eric C. Grimm

Department of Earth and Atmospheric Sciences: Faculty Publications

High-resolution paleohydrological reconstructions were carried out in five shallow lakes in the Nebraska Sand Hills across an east–west transect in order to 1) determine whether long-term droughts of the past 4000 years were spatially and temporally coherent across the region, 2) distinguish local variation in climate or hydrology from regional patterns of change, and 3) compare the paleolimnological results with the existing dune-inferred drought records. Diatom- inferred lake-level was reconstructed for all sites and compared with other regional records. Alterations between high and low lake-levels were frequent during the past 4000 years, which suggests that shifts between dry and wet …

Evolution Of Large Carnivores During The Mid-Cenozoic Of North America: The Temnocyonine Radiation (Mammalia, Amphicyonidae) Robert M., Robert M. Hunt Jr.

Department of Earth and Atmospheric Sciences: Faculty Publications

This study describes and summarizes the Temnocyoninae (Mammalia, Carnivora), a subfamily of amphicyonid carnivores of considerable diversity and singular ecomorphology within Cenozoic faunas of North America. In temnocyonines, we see the first carnivorans to occupy an ecological niche as large cursorial predators. The subfamily is confined to the Arikareean NALMA, ranging in age from the latest early Oligocene to the early Miocene. Distributed from the Pacific Northwest to the Great Plains and Florida, there are four genera (Temnocyon, Mammacyon, Delotrochanter n. gen., Rudiocyon n. gen.) and 12 species, of which eight are newly described (Temnocyon subferox …

Mass Wasting As A Geologic Hazard In The Province Of Salta, Argentina, William J. Wayne

Department of Earth and Atmospheric Sciences: Faculty Publications

The north-south orient ation ofthe mo unta inous part ofthe Province ofSalta form s a massive barrier to easy communication between the more populate d region in the central pan of the provin ce and the communities to the west. Routes follow deeply entrenched valleys th at are frequ entl y th e sites ofdebris flows that cause disruptions in th e flow of traffic during the months of December through March , wh en most of the precipitation of the region is recorded . The steep topography and the tecton ic settings have resulted in nearly 150 large landslides …

Estimating Hydraulic Conductivity For The Martian Subsurface Based On Drainage Patterns — A Case Study In The Mare Tyrrhenum Quadrangle, Wei Luo, Bartosz Grudzinski, Darryll T. Pederson

Department of Earth and Atmospheric Sciences: Faculty Publications

Hydraulic conductivity K, as the coefficient of proportionality in Darcy’s Law, is critical in understanding the past Martian hydrologic cycle, climate, and landform evolution. However, K and its spatial variability on Mars are thus far poorly constrained due to lack of accessibility. Using an innovative method based on surface drainage dissection patterns, which has been successfully tested in the Oregon Cascades on Earth, we estimated K in the Mare Tyrrhenum Quadrangle on Mars. The basic assumption is that under long-term dynamic equilibrium conditions, the overall dissection pattern in a watershed as reflected in drainage density is controlled by the …

Late Pleistocene Dune Activity In The Central Great Plains, Usa, Joseph A. Mason, James B. Swinehart, Paul R. Hanson, David Loope, Ronald J. Goble, Xiaodong Miao, Rebecca L Schmeisser

Department of Earth and Atmospheric Sciences: Faculty Publications

Stabilized dunes of the central Great Plains, especially the megabarchans and large barchanoid ridges of the Nebraska Sand Hills, provide dramatic evidence of late Quaternary environmental change. Episodic Holocene dune activity in this region is now well-documented, but Late Pleistocene dune mobility has remained poorly documented, despite early interpretations of the Sand Hills dunes as Pleistocene relicts. New optically stimulated luminescence (OSL) ages from drill cores and outcrops provide evidence of Late Pleistocene dune activity at sites distributed across the central Great Plains. In addition, Late Pleistocene eolian sands deposited at 20–25 ka are interbedded with loess south of the …

Rapid Landscape Transformation In South Island, New Zealand, Following Initial Polynesian Settlement, David B. Mcwethy, Cathy Whitlock, Janet M. Wilmshurst, Matt S. Mcglone, Mairie Fromont, Xun Li, Ann Dieffenbacher-Krall, William O. Hobbs, Sherilyn C. Fritz, Edward R. Cook

Department of Earth and Atmospheric Sciences: Faculty Publications

Humans have altered natural patterns of fire for millennia, but the impact of human-set fires is thought to have been slight in wet closed-canopy forests. In the South Island of New Zealand, Polynesians (Māori), who arrived 700–800 calibrated years (cal y) ago, and then Europeans, who settled ∼150 cal y ago, used fire as a tool for forest clearance, but the structure and environmental consequences of these fires are poorly understood. High-resolution charcoal and pollen records from 16 lakes were analyzed to reconstruct the fire and vegetation history of the last 1,000 y. Diatom, chironomid, and element concentration data were …

Development Of An Arcuate Fold-Thrust Belt As A Result Of Basement Configuration: An Example From The Rocky Mountain Front Range, Montana, Caroline M. Burberry, D. L. Cannon, T. Engelder, J. W. Cosgrove

Department of Earth and Atmospheric Sciences: Faculty Publications

The Sawtooth Range forms part of the Montana Disturbed Belt in the Front Ranges of the Rocky Mountains, along strike from the Alberta Syncline in the Canadian Rockies. The belt developed in the footwall to the Lewis Thrust during the Sevier orogeny and is similar in deformation style to the Canadian Foothills, with a series of stacked thrust sheets carrying Palaeozoic carbonates. The Sawtooth Range can be divided into an inner and outer deformed belt, separated by exposed fold structures in the overlying clastic sequence. Structures in the deformed belts plunge into the culmination of the NE-trending Scapegoat-Bannatyne trend, part …

Subsurface Images Shed Light On Past Tsunamis In India, Rajesh R. Nair, Ilya Buynevich, Ronald J. Goble, P. Srinivasan, S. G. N. Murthy, S. C. Kandpal, C. S. Vijaya Lakshmi, D. Trivedi

Department of Earth and Atmospheric Sciences: Faculty Publications

The 2004 Indian Ocean tsunami caused massive devastation and left a lasting impact along many of the major coastal regions in South Asia, including the coast of Tamil Nadu, a state in the southeastern tip of India. Following the event, sand deposits draped the low-lying areas and buried the muddy sediments of the coastal plain [Babu et al., 2007; Srinivasalu et al., 2007]. In addition, erosional features related to the tsunami, such as channels and scarps, have been observed along many parts of the coast (Figure 1a). This tsunami, along with a recorded history of intense monsoons, …

The Waterfalls Of Kauai, Hawaii, Darryll T. Pederson

Department of Earth and Atmospheric Sciences: Faculty Publications

Everyone enjoys the sounds and sights of a tropical waterfall. They are the setting for romantic and action packed movies. Fantasy Island used Wailua Falls on Kauai to open their weekly TV series. From a different viewpoint waterfall origin and evolution has been attributed to a wide range of geologic processes. The Hawaiian Island's waterfalls and amphitheater-headed valleys have been cited by many as equivalent to similar features seen on Mars. After a number of years of studying these features on Kauai, I offer the following thoughts and observations about Kauai's waterfalls and amphitheater-headed valleys.

Continental Warming Preceding The Paleocene–Eocene Thermal Maximum, Ross Secord, Philip D. Gingerich, Kyger C. Lohmann, Kenneth G. Macleod

Department of Earth and Atmospheric Sciences: Faculty Publications

Marine and continental records show an abrupt negative shift in carbon isotope values at ~55.8 Myr ago. This carbon isotope excursion (CIE) is consistent with the release of a massive amount of isotopically light carbon into the atmosphere and was associated with a dramatic rise in global temperatures termed the Paleocene–Eocene thermal maximum (PETM). Greenhouse gases released during the CIE, probably including methane, have often been considered the main cause of PETM warming. However, some evidence from the marine record suggests that warming directly preceded the CIE, raising the possibility that the CIE and PETM may have been linked to …