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Articles 1 - 30 of 37
Full-Text Articles in Physical Sciences and Mathematics
The Tiffanian Land-Mammal Age (Middle And Late Paleocene) In The Northern Bighorn Basin, Wyoming, Ross Secord
The Tiffanian Land-Mammal Age (Middle And Late Paleocene) In The Northern Bighorn Basin, Wyoming, Ross Secord
Department of Earth and Atmospheric Sciences: Faculty Publications
The Tiffanian North American land-mammal age is an informal biochronologic unit that spans 4.5 myr of the middle and late Paleocene. It is preceded and succeeded by the Torrejonian and Clarkforkian land-mammal ages, respectively. The Tiffanian was initially based on a small collection of mammals from southern Colorado, but faunas of Tiffanian age are now known throughout the Rocky Mountain region. The richest and most complete sequence of middle and late Tiffanian faunas known occurs in the northern Bighorn Basin. These faunas are the primary basis for regional Tiffanian biochronology. The Bighorn Basin sequence is also important because it preserves …
Loess Record Of The Pleistocene–Holocene Transition On The Northern And Central Great Plains, Usa, Joseph A. Mason, Xiaodong Miao, P.R. Hanson, William C. Johnson, Peter M. Jacobs, Ronald J. Goble
Loess Record Of The Pleistocene–Holocene Transition On The Northern And Central Great Plains, Usa, Joseph A. Mason, Xiaodong Miao, P.R. Hanson, William C. Johnson, Peter M. Jacobs, Ronald J. Goble
Department of Earth and Atmospheric Sciences: Faculty Publications
Various lines of evidence support conflicting interpretations of the timing, abruptness, and nature of climate change in the Great Plains during the Pleistocene–Holocene transition. Loess deposits and paleosols on both the central and northern Great Plains provide a valuable record that can help address these issues. A synthesis of new and previously reported optical and radiocarbon ages indicates that the Brady Soil, which marks the boundary between late Pleistocene Peoria Loess and Holocene Bignell Loess, began forming after a reduction in the rate of Peoria Loess accumulation that most likely occurred between 13.5 and 15 cal ka. Brady Soil formation …
The Lower Permian Wasp Head Formation, Sydney Basin: High-Latitude, Shallow Marine Sedimentation Following The Late Asselian To Early Sakmarian Glacial Event In Eastern Australia, Michael C. Rygel, Christopher R. Fielding, Kerrie L. Bann, Tracy D. Frank, Lauren Birgenheier, Stuart C. Tye
The Lower Permian Wasp Head Formation, Sydney Basin: High-Latitude, Shallow Marine Sedimentation Following The Late Asselian To Early Sakmarian Glacial Event In Eastern Australia, Michael C. Rygel, Christopher R. Fielding, Kerrie L. Bann, Tracy D. Frank, Lauren Birgenheier, Stuart C. Tye
Department of Earth and Atmospheric Sciences: Faculty Publications
ited during the transition to a non-glacial period following the late Asselian to early Sakmarian glacial event in eastern Australia. This shallow marine, sandstone-dominated unit can be subdivided into six facies associations. (i) The marine sediment gravity flow facies association consists of breccias and conglomerates deposited in upper shoreface water depths. (ii) Upper shoreface deposits consist of cross-stratified, conglomeratic sandstones with an impoverished expression of the Skolithos Ichnofacies. (iii) Middle shoreface deposits consist of hummocky cross-stratified sandstones with a trace fossil assemblage that represents the Skolithos Ichnofacies. (iv) Lower shoreface deposits are similar to middle shoreface deposits, but contain more …
Constraining The Amplitude Of Late Oligocene Bathymetric Changes In Western Ross Sea During Orbitally-Induced Oscillations In The East Antarctic Ice Sheet: (1) Implications For Glacimarine Sequence Stratigraphic Models, Gavin B. Dunbar, T. R. Naish, Peter J. Barrett, Christopher R. Fielding, R. D. Powell
Constraining The Amplitude Of Late Oligocene Bathymetric Changes In Western Ross Sea During Orbitally-Induced Oscillations In The East Antarctic Ice Sheet: (1) Implications For Glacimarine Sequence Stratigraphic Models, Gavin B. Dunbar, T. R. Naish, Peter J. Barrett, Christopher R. Fielding, R. D. Powell
Department of Earth and Atmospheric Sciences: Faculty Publications
Abstract Late Oligocene shallow glacimarine sequences recovered from western Ross Sea, Antarctica by the Cape Roberts (drilling) Project display orbitally-influenced cycles of advance and retreat of a laterally-extensive ice sheet across the continental shelf, in concert with changes in contemporary water-depth. During interglacial periods, when the glacier terminated on land, the coastline was largely ice-free and wave-influenced, and sediments accumulated in hydrodynamic equilibrium with the contemporary wave-climate. Here, we present estimates of paleobathymetry from intervals of three Milankovitch-duration glacimarine sequences (9, 10 and 11) that accumulated in open ocean conditions. We utilize an approach where the percentage of mud ( …
Rationale For A Permanent Seismic Network In The U.S. Central Plains Utilizing Usarray, Stephen S. Gao, Tina M. Niemi, Ross A. Black, Kelly H. Liu, Raymond R. Anderson, Robert M. Joeckel, Robert W. Busby, John Taber
Rationale For A Permanent Seismic Network In The U.S. Central Plains Utilizing Usarray, Stephen S. Gao, Tina M. Niemi, Ross A. Black, Kelly H. Liu, Raymond R. Anderson, Robert M. Joeckel, Robert W. Busby, John Taber
Department of Earth and Atmospheric Sciences: Faculty Publications
The eastern two thirds of the coterminous United States (from the Rocky Mountain Front to the east coast) are sparsely equipped with seismic monitoring instruments, with the number of permanent broadband seismic stations per unit area of the order of 5–10% of that in the western U.S. orogenic zone. In this Forum, we use the Central Plains area (CP)—defined here as the fourstate area including Nebraska, Kansas, Iowa, and Missouri—as an example to argue that a greatly densified permanent seismic network in the stable part of the United States could significantly improve our understanding of the processes that led to …
Alternative Indices For The Warm-Season Nao And Precipitation Variability In West Greenland, Frank A. Aebly, Qi Hu, Sherilyn C. Fritz
Alternative Indices For The Warm-Season Nao And Precipitation Variability In West Greenland, Frank A. Aebly, Qi Hu, Sherilyn C. Fritz
Department of Earth and Atmospheric Sciences: Faculty Publications
Observed precipitation records from Kangerlussuaq, Greenland, and atmospheric variables from the NCEP–NCAR reanalysis were used in a statistical analysis to elucidate controls on the seasonal variation of precipitation and develop indices that may be potentially useful for analyzing precipitation variability in paleoclimate and future climate change investigations. Three distinct patterns of correlation between precipitation and the 500-hPa geopotential height were found to represent three dominant atmospheric patterns that strongly influence precipitation for different times of the year. All three patterns show a relation to the North Atlantic Oscillation signature found in the first empirical orthogonal function of the 500-hPa height …
Postgraduate Conference Fund, Conference Reports: Complexity In Geomorphology: 38th Annual Binghamton Geomorphology Symposium, Duke University, North Carolina, Usa, 5-7 October 2007, Caroline M. Burberry
Postgraduate Conference Fund, Conference Reports: Complexity In Geomorphology: 38th Annual Binghamton Geomorphology Symposium, Duke University, North Carolina, Usa, 5-7 October 2007, Caroline M. Burberry
Department of Earth and Atmospheric Sciences: Faculty Publications
The British Society for Geomorphology Postgraduate Conference Fund, Conference Report on Complexity in Geomorphology: 38th Annual Binghamton Geomorphology Symposium, held at Duke University, North Carolina, USA, October 5-7, 2007.
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 …
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 …
Late Holocene Island Reef Development On The Inner Zone Of The Northern Great Barrier Reef: Insights From Low Isles Reef, Tracy D. Frank
Late Holocene Island Reef Development On The Inner Zone Of The Northern Great Barrier Reef: Insights From Low Isles Reef, Tracy D. Frank
Department of Earth and Atmospheric Sciences: Faculty Publications
A sedimentological and stratigraphic study of Low Isles Reef off northern Queensland, Australia was carried out to improve understanding of factors that have governed Late Holocene carbonate deposition and reef development on the inner to middle shelf of the northern Great Barrier Reef. Low Isles Reef is one of 46 low wooded island-reefs unique to the northern Great Barrier Reef, which are situated in areas that lie in reach of river flood plumes and where inter-reef sediments are dominated by terrigenous mud. Radiocarbon ages from surface and subsurface sediment samples indicate that Low Isles Reef began to form at ca …
Global Distribution Of Solid And Aqueous Sulfate Aerosols: Effect Of The Hysteresis Of Particle Phase Transitions, Jun Wang, Andrew A. Hoffmann, Rokjin J. Park, Daniel L. Jacob, Scot T. Martin
Global Distribution Of Solid And Aqueous Sulfate Aerosols: Effect Of The Hysteresis Of Particle Phase Transitions, Jun Wang, Andrew A. Hoffmann, Rokjin J. Park, Daniel L. Jacob, Scot T. Martin
Department of Earth and Atmospheric Sciences: Faculty Publications
The partitioning between solid and aqueous phases of tropospheric sulfate-ammonium particles is simulated with a global 3-D chemical transport model (CTM). The simulation explicitly accounts for the hysteresis of particle phase transitions by transporting aqueous sulfate and three solid sulfate forms (namely, ammonium sulfate, letovicite, and ammonium bisulfate). Composition-dependent deliquescence relative humidities (DRH) and crystallization relative humidities (CRH) are based on recent laboratory data. We find that the solids mass fraction on a sulfate basis is 0.34, partitioned as 93% ammonium sulfate, 6% letovicite, and 1% ammonium bisulfate. The fraction increases with altitude from 0.10 to 0.30 in the boundary …
Atlantic And Pacific Sst Influences On Medieval Drought In North America Simulated By The Community Atmospheric Model, Song Feng, Robert J. Oglesby, Clinton M. Rowe, David B. Loope, Qi Steven Hu
Atlantic And Pacific Sst Influences On Medieval Drought In North America Simulated By The Community Atmospheric Model, Song Feng, Robert J. Oglesby, Clinton M. Rowe, David B. Loope, Qi Steven Hu
Department of Earth and Atmospheric Sciences: Faculty Publications
Severe drought is arguably one of the greatest recurring natural disasters that strikes North America. A synthesis of multiproxy data shows that North America was in the grip of a severe centennial-scale drought during medieval times (800–1300 AD). In this study, the Community Atmospheric Model (CAM) is used to investigate the role of sea surface temperature (SST) anomalies from the North Atlantic and the tropical Pacific Ocean on this megadrought. These anomalies are obtained from proxy reconstructions of SST. Four model experiments with prescribed SST anomalies in the tropical Pacific and/or North Atlantic Ocean were made. The CAM results captured …
Stable Isotopes In Early Eocene Mammals As Indicators Of Forest Canopy Structure And Resource Partitioning, Ross Secord, Scott L. Wing, Amy Chew
Stable Isotopes In Early Eocene Mammals As Indicators Of Forest Canopy Structure And Resource Partitioning, Ross Secord, Scott L. Wing, Amy Chew
Department of Earth and Atmospheric Sciences: Faculty Publications
The three dimensional structure of vegetation is an important component of ecosystems, yet it is difficult to reconstruct from the fossil record. Forests or woodlands prevailed at mid-latitudes in North America during the early Eocene but tree spacing and canopy structure are uncertain. Here we use stable carbon isotope values (δ13C) in early Eocene mammalian faunas to infer canopy structure. We compare δ13C values in two diverse fossil assemblages from the central Bighorn Basin to values predicted for mammals in a variety of open and closed habitats, based on modern floras and faunas. We conclude that …
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, …
The Geology Of Ukhaa Tolgod (Djadokhta Formation, Upper Cretaceous, Nemegt Basin, Mongolia), Lowell Dingus, David B. Loope, Demberlyin Dashzeveg, Carl C. Swisher Iii, Chuluun Minjin, Michael J. Novacek, Mark A. Norell
The Geology Of Ukhaa Tolgod (Djadokhta Formation, Upper Cretaceous, Nemegt Basin, Mongolia), Lowell Dingus, David B. Loope, Demberlyin Dashzeveg, Carl C. Swisher Iii, Chuluun Minjin, Michael J. Novacek, Mark A. Norell
Department of Earth and Atmospheric Sciences: Faculty Publications
The lithostratigrahy and sedimentology of the fossiliferous Upper Cretaceous strata exposed in the Gobi Desert of Mongolia at Ukhaa Tolgod are described and mapped on aerial photos. Topographic features are also mapped by plane table and alidade.
Five lithologic and sedimentologic facies are described: E-1, distinctly cross-stratified sandstone with fine structure, interpreted to represent eolian dune deposits; E-2, vaguely bedded sandstone with cross-stratified concretionary sheets, interpreted to represent eolian dune deposits modified by diagenetic formation of slope-parallel concretionary sheets of pedogenic calcite; S, structureless sandstone lacking concretions or cross-strata, interpreted to represent sandslide deposits generated by mass wasting along the …
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 …
Modelling The Deformation Front Of A Fold-Thrust Belt: The Effect Of An Upper Detachment Horizon (Abstract), Caroline M. Burberry, H. Koyi, F. Nilfouroushan, John W. Cosgrove
Modelling The Deformation Front Of A Fold-Thrust Belt: The Effect Of An Upper Detachment Horizon (Abstract), Caroline M. Burberry, H. Koyi, F. Nilfouroushan, John W. Cosgrove
Department of Earth and Atmospheric Sciences: Faculty Publications
First sentence of abstract: Structures found at the deformation fronts of fold-thrust belts are variable in type, geometry and spatial organisation, as can be demonstrated from comparisons between structures in the Zagros Fold-Thrust Belt, Iran and the Sawtooth Range, Montana.
Seismic Facies And Stratigraphy Of The Cenozoic Succession In Mcmurdo Sound, Antarctica: Implications For Tectonic, Climatic And Glacial History, Christopher R. Fielding, Joanne Whittaker, Stuart A. Henrys, Terry J. Wilson, Timothy R. Naish
Seismic Facies And Stratigraphy Of The Cenozoic Succession In Mcmurdo Sound, Antarctica: Implications For Tectonic, Climatic And Glacial History, Christopher R. Fielding, Joanne Whittaker, Stuart A. Henrys, Terry J. Wilson, Timothy R. Naish
Department of Earth and Atmospheric Sciences: Faculty Publications
Integration of data from fully cored stratigraphic holes with an extensive grid of seismic reflection lines in McMurdo Sound, Antarctica, has allowed the formulation of a new model for the evolution of the Cenozoic Victoria Land Basin of the West Antarctic Rift. The Early Rift phase (Eocene to Early Oligocene) is recorded by wedges of strata confined by early extensional faults, and which contain seismic facies consistent with drainage via coarse-grained fans and deltas into discrete, actively subsiding grabens and half-grabens. The Main Rift phase (Early Oligocene to Early Miocene) is represented by a lens of strata that thickens symmetrically …
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 …
High-Spectral Resolution Simulation Of Polarization Of Skylight: Sensitivity To Aerosol Vertical Profile, Jing Zeng, Qingyuan Han, Jun Wang
High-Spectral Resolution Simulation Of Polarization Of Skylight: Sensitivity To Aerosol Vertical Profile, Jing Zeng, Qingyuan Han, Jun Wang
Department of Earth and Atmospheric Sciences: Faculty Publications
A vector radiative transfer model was used in conjunction with the line-by-line radiative transfer model and the database of high-resolution transmission (HITRAN) molecular absorption to simulate the degree of linear polarization of skylight in cloud-free conditions. Differences between simulated and measured polarization data in highspectral resolution are found to be within 1% after aerosol scattering and gas absorptions are carefully considered. Limiting experiments are conducted at wavelengths around 0.760–0.765 μm O2-A absorption band for the same columnar aerosol optical thickness but different aerosol profiles. Results showed that the degree of linear polarization of skylight at surface varies strongly …
The Optimal Bulk Wind Differential Depth And The Utility Of The Upper-Tropospheric Storm-Relative Flow For Forecasting Supercells, Adam L. Houston, Richard L. Thompson, Roger Edwards
The Optimal Bulk Wind Differential Depth And The Utility Of The Upper-Tropospheric Storm-Relative Flow For Forecasting Supercells, Adam L. Houston, Richard L. Thompson, Roger Edwards
Department of Earth and Atmospheric Sciences: Faculty Publications
An analysis of 4 yr of Rapid Update Cycle-2 (RUC-2) derived soundings in proximity to radar-observed supercells and nonsupercells is conducted in an effort to answer two questions: 1) over what depth is the fixed-layer bulk wind differential (BWD; the vector difference between the wind velocity at a given level and the wind velocity at the surface) the best discriminator between supercell and nonsupercell environments and 2) does the upper-tropospheric storm-relative flow (UTSRF) discriminate between the environments of supercells and nonsupercells? Previous climatologies of sounding-based supercell forecast parameters have documented the ability of the 0–6-km BWD in delineating supercell from …
Variation Of The North American Summer Monsoon Regimes And The Atlantic Multidecadal Oscillation, Q. Steven Hu, Yongjun Zheng
Variation Of The North American Summer Monsoon Regimes And The Atlantic Multidecadal Oscillation, Q. Steven Hu, Yongjun Zheng
Department of Earth and Atmospheric Sciences: Faculty Publications
The North American summer monsoon holds the key to understanding warm season rainfall variations in the region from northern Mexico to the Southwest and the central United States. Studies of the monsoon have pictured mosaic submonsoonal regions and different processes influencing monsoon variations. Among the influencing processes is the “land memory,” showing primarily the influence of the antecedent winter season precipitation (snow) anomalies in the Northwest on summer rainfall anomalies in the South- west. More intriguingly, the land memory has been found to vary at the multidecadal time scale. This memory change may actually reflect multidecadal variations of the atmospheric …
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 …
Gender Imbalance In U.S. Geoscience Academia, Mary Anne Holmes, Suzanne O'Connell, Connie Frey, Lois Ongley
Gender Imbalance In U.S. Geoscience Academia, Mary Anne Holmes, Suzanne O'Connell, Connie Frey, Lois Ongley
Department of Earth and Atmospheric Sciences: Faculty Publications
Geoscientists explain women’s under-representation in our field along three dominant themes: the structure of academia, historically low numbers of women, and women’s views and choices. Which factor they perceive as most important depends overwhelmingly on their gender.
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) …
Ground-Based Thermography Of Fluvial Systems At Low And High Discharge Reveals Potential Complex Thermal Heterogeneity Driven By Flow Variation And Bioroughness, M. Bayani Cardenas, Judson W. Harvey, Aaron I. Packman, Durelle T. Scott
Ground-Based Thermography Of Fluvial Systems At Low And High Discharge Reveals Potential Complex Thermal Heterogeneity Driven By Flow Variation And Bioroughness, M. Bayani Cardenas, Judson W. Harvey, Aaron I. Packman, Durelle T. Scott
Department of Earth and Atmospheric Sciences: Faculty Publications
Temperature is a primary physical and biogeochemical variable in aquatic systems. Field-based measurement of temperature at discrete sampling points has revealed temperature variability in fluvial systems, but traditional techniques do not readily allow for synoptic sampling schemes that can address temperature-related questions with broad, yet detailed, coverage. We present results of thermal infrared imaging at different stream discharge (base flow and peak flood) conditions using a handheld IR camera. Remotely sensed temperatures compare well with those measured with a digital thermometer. The thermal images show that periphyton, wood, and sandbars induce significant thermal heterogeneity during low stages. Moreover, the images …
Sensitivity Of Sulfate Direct Climate Forcing To The Hysteresis Of Particle Phase Transitions, Jun Wang, Daniel J. Jacob, Scot T. Martin
Sensitivity Of Sulfate Direct Climate Forcing To The Hysteresis Of Particle Phase Transitions, Jun Wang, Daniel J. Jacob, Scot T. Martin
Department of Earth and Atmospheric Sciences: Faculty Publications
The effects of solid-aqueous phase transitions on sulfate direct climate forcing (SDCF) are investigated by using both a column model and a global chemical transport model. Aqueous particles have a larger mass extinction efficiency but a smaller backscattered fraction than their solid counterparts. The column model shows that the hysteresis of the phase transition can result in an uncertainty in the SDCF of 20%. The global chemical transport model explicitly accounts for the relative humidity processing of particles and the associated hysteresis. The model also treats the extent of sulfate neutralization by ammonia. For the anthropogenic sulfate, the base case …
Atlantic And Pacific Sst Influences On Medieval Drought In North America Simulated By The Community Atmospheric Model, Song Feng, Robert Oglesby, Clinton M. Rowe, David B. Loope, Qi Hu
Atlantic And Pacific Sst Influences On Medieval Drought In North America Simulated By The Community Atmospheric Model, Song Feng, Robert Oglesby, Clinton M. Rowe, David B. Loope, Qi Hu
Department of Earth and Atmospheric Sciences: Faculty Publications
Severe drought is arguably one of the greatest recurring natural disasters that strikes North America. A synthesis of multiproxy data shows that North America was in the grip of a severe centennial-scale drought during medieval times (800–1300 AD). In this study, the Community Atmospheric Model (CAM) is used to investigate the role of sea surface temperature (SST) anomalies from the North Atlantic and the tropical Pacific Ocean on this megadrought. These anomalies are obtained from proxy reconstructions of SST. Four model experiments with prescribed SST anomalies in the tropical Pacific and/or North Atlantic Ocean were made. The CAM results captured …
Wind Scour Of Navajo Sandstone At The Wave (Central Colorado Plateau, U.S.A.), David B. Loope, Winston M. Seiler, Joseph A. Mason, Marjorie A. Chan
Wind Scour Of Navajo Sandstone At The Wave (Central Colorado Plateau, U.S.A.), David B. Loope, Winston M. Seiler, Joseph A. Mason, Marjorie A. Chan
Department of Earth and Atmospheric Sciences: Faculty Publications
At the Wave, a photogenic landform on the Utah–Arizona border, modern, southwesterly, sand-carrying winds abrade the Navajo Sandstone. Abundant trains of centimeter-scale, transverse, upwind-facing treads and risers cut sedimentary structures at a high angle. Central to the formation of these erosional steps are crusts produced by microbes lying just beneath exposed sandstone surfaces. Treads and risers are present on the walls of smoothly curved troughs at the Wave, on the walls of nearby circular scour pits, and on bedrock domes found at the center of scour pits. Because of their locations and orientations, the large-scale troughs and scour pits could …
Chloride And The Environmental Isotopes As The Indicators Of The Groundwater Recharge In The Gobi Desert, Northwest China, J. Z. Ma, Z. Ding, John B. Gates, Y. Su
Chloride And The Environmental Isotopes As The Indicators Of The Groundwater Recharge In The Gobi Desert, Northwest China, J. Z. Ma, Z. Ding, John B. Gates, Y. Su
Department of Earth and Atmospheric Sciences: Faculty Publications
The long term recharge in Gobi Desert from Hexi Corridor to Inner Mongolia Plateau was estimated to Be 1 mm year-1 by using the chloride mass balance method from one unsaturated zone profile, which shows that no effective modern recharge is taking place. A good rainfall database from Zhangye provides definition of the stable isotopic composition of modern rainfall. The signature of groundwater from the late Pleistocene differs markedly from that of the Holocene, shown clearly by the compositions of -10.5‰ δ18O as compared with values of -7‰ at the present day. It is apparent that the …