Earth Sciences Commons^™

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 …

An Observational Analysis And Evaluation Of Land Surface Model Accuracy In The Nebraska Sand Hills, David B. Radell, Clinton M. Rowe

Department of Earth and Atmospheric Sciences: Faculty Publications

In this study, the influence of subsurface water on the energy budget components of three locations with heterogeneous land surfaces in the Nebraska Sand Hills are examined through observations and use of the Noah land surface model (LSM). Observations of the four primary components of the surface energy budget are compared for a wet interdunal meadow valley, a dry interdunal valley, and a dunal upland location. With similar atmospheric forcing at each site, it was determined that differences in the partitioning of the mean diurnal net radiation (R_net) existed among the three locations due to the influence …

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 …

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

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 …

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) …

Spatial Arrangement Of Fold Types In The Zagros Simply Folded Belt, Iran, Indicated By Landform Morphology And Drainage Pattern Characteristics, Caroline M. Burberry, John W. Cosgrove, Jian Guo Liu

Department of Earth and Atmospheric Sciences: Faculty Publications

The spatial arrangement of fold types within the Zagros Simply Folded Belt was analysed using satellite images, a digital elevation model and a digital drainage network. Distinct fold geometries, principally fault-bend folds and detachment folds, can be identified by characteristic interactions with streams flowing SW from the High Zagros Mountains into the Persian Gulf. In addition, the morphology of the landforms is reflected in the minor channel patterns across the folds. This morphology can also be categorised using geomorphic indices, L/W ratio and symmetry index. The distribution of fold types is shown for the region N27°-N30°, E50°-E54° at a scale …

Inconsistencies Between Pangean Reconstructions And Basic Climate Controls, Clinton Rowe, David B. Loope, Robert J. Oglesby, Rob Van Der Voo, Charles E. Broadwater

Department of Earth and Atmospheric Sciences: Faculty Publications

The supercontinent Pangea dominated our planet from the Permian into the Jurassic. Paleomagnetic reconstructions have been used to estimate the latitudinal position of Pangea during this 100-million-year period. Atmospheric circulation, recorded by eolian sandstones in the southwestern United States, shows a broad sweep of northeasterly winds over their northernmost extent, curving to become northwesterly in the south. This evidence is consistent with paleomagnetic reconstructions of the region straddling the equator in the Early Permian but is at odds with its northward movement to about 20°N by the Early Jurassic. At least one of the following scenarios must be true: the …

Retreating To Advance Women Geoscience Faculty, Suzanne O'Connell, Mary Anne Holmes

Department of Earth and Atmospheric Sciences: Faculty Publications

Seventeen women geoscientists from New England, New York, and New Jersey assembled for a writing retreat at Boston College's Connors Family Retreat and Conference Center, set on 80 pastoral acres on the outskirts of Boston. Funded through the National Science Foundation ADVANCE program, the retreat had two objectives: to facilitate writing and to develop a supportive community. It succeeded on both accounts. Although new to science, retreats of this sort have long been a highly sought after experience for writers in other disciplines. The potential benefits for scientists, in particular, women scientists, are great. Writing is a cornerstone of our …

Sedimentology Of The Whiteclay Gravel Beds (Ogallala Group) In Northwestern Nebraska, Usa: Structurally Controlled Drainage Promoted By Early Miocene Uplift Of The Black Hills Dome, Christopher R. Fielding, Hannan E. Lagarry, Leigh Anne Lagarry, Bruce E. Bailey, James B. Swinehart

Department of Earth and Atmospheric Sciences: Faculty Publications

The newly recognized Whiteclay Gravel Beds (WGB) of the Miocene Ogallala Group crop out as a narrow, discontin­uous ribbon of sands and gravels in Dawes and Sheridan Counties, northwestern Nebraska, USA. The WGB are ex­posed in a series of municipal gravel quarries and natural exposures that define a linear trench in underlying strata at least 20 m deep and up to 300 m wide, with short, southeast-trending reaches separating generally longer east-trend­ing sections. This gravel-filled trench can be recognized from the Nebraska–South Dakota border near Whiteclay, Ne­braska southeastward to east of Gordon, Nebraska, a distance of ~ 30 km. The …

Combined Remote Sensing And Field Investigations Of Hydrocarbon Trap Analogue Structures: Examples From The Zagros Simply Folded Belt, Iran And The Sawtooth Range, Montana [Abstract], Caroline M. Burberry, David Cannon, John W. Cosgrove, Terry Engelder

Department of Earth and Atmospheric Sciences: Faculty Publications

First paragraph of abstract: Structures that outcrop at the surface in fold-thrust belts are frequently good analogues for hydrocarbon traps in compressional environments. Along-strike changes in structure and geometry have important implications for connectivity and fluid flow throughout the petroleum system, e.g. in the Zagros Simply Folded Belt, Iran, and in a surface reservoir analogue in the Sawtooth Range, Montana.

Sedimentology And Stratigraphic Architecture Of The Late Permian Betts Creek Beds, Queensland, Australia, Jonathan P. Allen, Christopher R. Fielding

Department of Earth and Atmospheric Sciences: Faculty Publications

The Late Permian Betts Creek Beds form a succession of coal-bearing alluvial-coastal plain sediments in a basin marginal setting within the northeastern Galilee Basin, Queensland, Australia. The unit is ~ 50–60 m in thick­ness at Porcupine Creek National Park where outcrop is laterally continuous for several kilometers. Eight fa­cies have been identified within the formation and can be grouped into 2 facies associations: (A) channel depos­its and (B) floodbasin deposits. The channel association consists of conglomerate (A1) and trough cross-bedded multistorey sandstone facies (A2), both interpreted as deposits of low-sinuosity river systems, tidally influenced fluvial channels (A3), interbedded sandstone and …

Quaternary Glaciation And Hydrologic Variation In The South American Tropics As Reconstructed From The Lake Titicaca Drilling Project, Sherilyn C. Fritz, Paul A. Baker, Geoffrey O. Seltzer, Ashley Ballantyne, Pedro Tapia, Hai Cheng, R. Lawrence Edwards

Department of Earth and Atmospheric Sciences: Faculty Publications

A 136-m-long drill core of sediments was recovered from tropical high-altitude Lake Titicaca, Bolivia-Peru, enabling a reconstruction of past climate that spans four cycles of regional glacial advance and retreat and that is estimated to extend continuously over the last 370,000 yr. Within the errors of the age model, the periods of regional glacial advance and retreat are concordant respectively with global glacial and interglacial stages. Periods of ice advance in the southern tropical Andes generally were periods of positive water balance, as evidenced by deeper and fresher conditions in Lake Titicaca. Conversely, reduced glaciation occurred during periods of negative …

Drainage Diversion Patterns And Landform Morphology As An Indicator Of Deformation Style: Examples From The Zagros Simply Folded Belt, Islamic Republic Of Iran (Abstract), Caroline M. Burberry, John W. Cosgrove, J.-G. Liu

Department of Earth and Atmospheric Sciences: Faculty Publications

First paragraph of abstract: In the NW-SE trending Zagros Simply Folded Belt, landform organisation is shown to be a straightforward response to tectonic forcing processes using remote sensing. Two end-member fold types (detachment folds and fault-bend folds) interact with streams flowing into the Persian Gulf. Using drainage network analysis and geomorphologic methods, the organisation of emergent landform morphologies is mapped and the distribution of different fold types is inferred.

A Diatom Record Of Late Holocene Climate Variation In The Northern Range Of Yellowstone National Park, Usa, Brandi B. Bracht, Jeffery R. Stone, Sherilyn C. Fritz

Department of Earth and Atmospheric Sciences: Faculty Publications

The changes in diatom species composition in a sediment core from Crevice Lake, Yellowstone National Park, spanning the past 2550 yr, were used to reconstruct long-term limnological and ecological conditions that may be related to late Holocene climate variability. Planktic forms dominate the fossil diatom assemblages throughout this record, but changes in species dominance indicate varying nutrient levels over time, particularly phosphorus. The changes in the nutrient concentrations in the lake were probably driven by changes in temperature and wind strength that affected the duration of watercolumn mixing and thus the extent of nutrient recycling from deep waters. Prior to …

A 2650-Year-Long Record Of Environmental Change From Northern Yellowstone National Park Based On A Comparison Of Multiple Proxy Data, Cathy Whitlock, Walter Dean, Joseph Rosenbaum, Lora Stevens, Sherilyn C. Fritz, Brandi Bracht, Mitchell Power

Department of Earth and Atmospheric Sciences: Faculty Publications

Geochemical, stable-isotope, pollen, charcoal, and diatom records were analyzed at high-resolution in cores obtained from Crevice Lake, a varved-sediment lake in northern Yellowstone National Park. The objective was to reconstruct the ecohydrologic, vegetation, and fire history of the watershed for the last 2650 years to better understand past climate variations at the forest-steppe transition. The data suggest a period of limited bottom-water anoxia, relatively wet winters, and cool springs and summers from 2650 to 2100 cal yrBP (700–150 BC). Dry warm conditions occurred between 2100 and 850–800 cal yrBP (150 BC and AD 1100–1150), when the lake was anoxic, winter …

Sequence Stratigraphic Controls On Synsedimentary Cementation And Preservation Of Dinosaur Tracks: Example From The Lower Cretaceous, (Upper Albian) Dakota Formation, Southeastern Nebraska, U.S.A., Preston Lee Phillips Jr., Greg A. Ludvigson, R. Matthew Joeckel, Luis A. González, Robert L. Brenner, Brian J. Witzke

Department of Earth and Atmospheric Sciences: Faculty Publications

A thin cemented sandstone bed in the Upper Albian Dakota Formation of southeastern Nebraska contains the first dinosaur tracks to be described from the state. Of equal importance to the tracks are stable-isotope (C, O) analyses of cements in the track bed, especially in the context of data derived from generally correlative strata (sandstones and sphaerosiderite-bearing paleosols) in the region. These data provide the framework for interpretations of paleoenvironmental conditions, as well as a novel approach to understanding mechanisms of terrestrial vertebrate track preservation.

High minus-cement-porosity (> 47%) and low grain-to-grain contacts (~2.5) in the track bed indicate early (pre-compaction) …

Leaks In The Pipeline: Why Do Women Remain Curiously Absent From The Ranks Of Academia?, Mary Anne Holmes

Department of Earth and Atmospheric Sciences: Faculty Publications

Family issues can cause women to abandon academia at every rung of the career ladder. Policy-makers have addressed some ways to get more women on to the lower rungs of the ladder. But solutions at the higher steps—tenure and beyond—are proving a little more difficult.

Lacustrine Evidence For Moisture Changes In The Nebraska Sand Hills During Marine Isotope Stage 3, Kimberly C. Jacobs, Sherilyn C. Fritz, James B. Swinehart

Department of Earth and Atmospheric Sciences: Faculty Publications

In the central Great Plains of North America, loess stratigraphy suggests that climate during the late Pleistocene was cold and dry. However, this record is discontinuous, and there are few other records of late-Pleistocene conditions. Cobb Basin, located on the northern edge of the Nebraska Sand Hills, contains lacustrine sediments deposited during Marine Isotope Stage 3, beginning approximately 45,000 cal yr BP and continuing for at least 10,000 yr. The lake was formed by a dune dam blockage on the ancient Niobrara River, and its deposits contain a diatom record that indicates changes through time in lake depth driven by …

Evaluating Climatic And Non-Climatic Influences On Ion Chemistry In Natural And Man-Made Lakes Of Nebraska, Usa, D. M. Bennett, Sherilyn C. Fritz, John C. Holz, Aris A. Holz, Vitaly A. Zlotnik

Department of Earth and Atmospheric Sciences: Faculty Publications

Conductivity and major ion chemistry data were analyzed for a suite of Nebraska (USA) natural lakes, reservoirs, sand pits, and barrow pits to evaluate the magnitude of climatic versus non-climatic influence on ionic concentration and composition. In both natural lakes and sand and barrow pits, conductivity is positively related to longitude and reflects decreasing effective moisture from east to west. Reservoirs showed no relationship between lake conductivity and location, probably because the reservoirs are very strongly influenced by groundwater and surface water inflow and have shorter residence times relative to the other lake types. At smaller spatial scales, conductivity among …

Co2-Forced Climate And Vegetation Instability During Late Paleozoic Deglaciation, Isabel P. Montañez, Neil J. Tabor, Deb Niemeier, William A. Dimichele, Tracy D. Frank, Christopher R. Fielding, John L. Isbell, Lauren P. Birgenheier, Michael C. Rygel

Department of Earth and Atmospheric Sciences: Faculty Publications

The late Paleozoic deglaciation is the vegetated Earth’s only recorded icehouse-to-greenhouse transition, yet the climate dynamics remain enigmatic. By using the stable isotopic compositions of soil-formed minerals, fossil-plant matter, and shallow-water brachiopods, we estimated atmospheric partial pressure of carbon dioxide (pCO₂) and tropical marine surface temperatures during this climate transition. Comparison to southern Gondwanan glacial records documents covariance between inferred shifts in pCO₂, temperature, and ice volume consistent with greenhouse gas forcing of climate. Major restructuring of paleotropical flora in western Euramerica occurred in step with climate and pCO₂ shifts, illustrating the biotic impact associated …

Metastable Equilibria Among Dicarboxylic Acids And The Oxidation State During Aqueous Alteration On The Cm2 Chondrite Parent Body, Jason A. Mcalister, Richard M. Kettler

Department of Earth and Atmospheric Sciences: Faculty Publications

Linear saturated dicarboxylic acids are present in carbonaceous chondrite samples at concentrations that suggest aqueous alteration under conditions of metastable equilibrium. In this study, previously published values of dicarboxylic acid concentrations measured in Murchison, Yamato-791198, and Tagish Lake carbonaceous chondrites are converted to aqueous activities during aqueous alteration assuming water:rock ratios that range from 1:10 to 10:1. Logarithmic plots of the aqueous activities of any two dicarboxylic acids are proximal to lines whose slope is fixed by the stoichiometry of reactions describing the oxidation–reduction equilibrium between the two species. The precise position of any line is controlled by the equilibrium …

Burrows Dug By Large Vertebrates Into Rain-Moistened Middle Jurassic Sand Dunes: A Reply, David B. Loope

Department of Earth and Atmospheric Sciences: Faculty Publications

Odier (2007) is concerned with two issues: (1) I did not cite his work on burrows in the Navajo Sandstones of southeastern Utah in my article (Loope 2006), and (2) he believes I amwrong in interpreting the structures preserved in the Entrada Sandstone as burrows. On the first issue, I failed to cite both his 2004 abstract and the newly published book that he sent me in October 2006. My article was accepted on June 12, 2006; I returned the proofs on August 23; and the issue was published online on October 4, 2006. The timing of these events makes …

The Sensitivity Of Convective Initiation To The Lapse Rate Of The Active Cloud-Bearing Layer, Adam L. Houston, Dev Niyogi

Department of Earth and Atmospheric Sciences: Faculty Publications

Numerical experiments are conducted using an idealized cloud-resolving model to explore the sensitivity of deep convective initiation (DCI) to the lapse rate of the active cloud-bearing layer [ACBL; the atmospheric layer above the level of free convection (LFC)]. Clouds are initiated using a new technique that involves a preexisting airmass boundary initialized such that the (unrealistic) adjustment of the model state variables to the imposed boundary is disassociated from the simulation of convection. Reference state environments used in the experiment suite have identical mixed layer values of convective inhibition, CAPE, and LFC as well as identical profiles of relative humidity …

Observational Analysis Of The 27 May 1997 Central Texas Tornadic Event. Part Ii: Tornadoes, Adam L. Houston, Robert B. Wilhelmson

Department of Earth and Atmospheric Sciences: Faculty Publications

The 27 May 1997 central Texas tornadic event has been investigated in a two-part observational study. As demonstrated in Part I, the 1D environment associated with this event was unfavorable for significant (≥F2) tornadoes. Yet, the storm complex produced at least six significant tornadoes, including one rated F5 (the Jarrell, Texas, tornado). The purpose of this article is to examine the spatiotemporal interrelationships between tornadoes, preexisting boundaries, antecedent low-level mesocyclones, convective cells, and midlevel mesocyclones. It is shown that each of the six observed tornadoes that produced greater than F0 damage formed along the storm-generated gust front, not along preexisting …

Observational Analysis Of The 27 May 1997 Central Texas Tornadic Event. Part I: Prestorm Environment And Storm Maintenance/Propagation, Adam L. Houston, Robert B. Wilhelmson

Department of Earth and Atmospheric Sciences: Faculty Publications

A detailed analysis of the 27 May 1997 central Texas tornadic storm complex is undertaken in an attempt to document the prestorm environment and identify the roles played by preexisting boundaries on storm maintenance/propagation and rotation. Analysis is carried out using a broad suite of synoptic and subsynoptic data but focuses on the level-II and -III Weather Surveillance Radar-1988 Doppler (WSR-88D) data from three Texas radars. The 27 May 1997 event was characterized by a back-building (propagation against the mean flow) storm complex that produced at least 12 tornadoes including the F5 Jarrell, Texas, tornado. Furthermore, five of the eight …

An Improved Qc Process For Temperature In The Daily Cooperative Weather Observations, Kenneth Hubbard, Nathaniel B. Guttman, Jinsheng You, Zhirong Chen

Department of Earth and Atmospheric Sciences: Faculty Publications

TempVal is a spatial component of data quality assurance algorithms applied by the National Climatic Data Center (NCDC), and it has been used operationally for about 4 yr. A spatial regression test (SRT) approach was developed at the regional climate centers for climate data quality assurance and was found to be superior to currently used quality control (QC) procedures for the daily maximum and minimum air temperature. The performance of the spatial quality assessment procedures has been evaluated by assessing the rate with which seeded errors are identified. A complete dataset with seeded errors for the year 2003 for the …

High-Resolution Evidence For Dynamic Transitional Geomagnetic Field Behaviour From A Miocene Reversal, Mcmurdo Sound, Ross Sea, Antarctica, Andrew P. Roberts, Anisch Bakrania, Fabio Florindo, Christopher J. Rowan, Christopher R. Fielding, Ross D. Powell

Department of Earth and Atmospheric Sciences: Faculty Publications

We report a high-resolution record of a Miocene polarity transition (probably the Chron C6r-C6n transition) from glacimarine sediments in McMurdo Sound, Ross Sea, Antarctica, which is the first transition record reported from high southern latitudes. The transition is recorded in two parallel cores through a 10.7 m stratigraphic thickness. The sediments are interpreted as having been deposited in a marine environment under the influence of floating ice or seaward of a glacier terminus from which a large sediment load was delivered to the drill site. The core was recovered using rotary drilling, which precludes azimuthal orientation of the core and …

A Novel Over-Sea-Ice Seismic Reflection Survey In Mcmurdo Sound, Antarctica, S. J. Betterly, M. A. Speece, R. H. Levy, David M. Harwood, S. A. Henrys

Department of Earth and Atmospheric Sciences: Faculty Publications

During the austral spring of 2005, approximately 28 km of over-sea-ice seismic reflection data were recorded over McMurdo Sound, Antarctica, in support of the ANtarctic geological DRILLing Program (ANDRILL). The 2005 ANDRILL Southern McMurdo Sound Project (SMS) seismic survey incorporated techniques that improved the quality of over-sea-ice seismic data. Previous over-sea-ice seismic experiments have had limited success because of poor source coupling caused by thin sea ice and source bubble-pulse effects caused by explosive seismic sources placed in the water column. To mitigate these problems, a Generator-Injector (GI) air gun was used as the seismic source. The GI air gun …

Preservation And Erosion Of Theropod Tracks In Eolian Deposits: Examples From The Middle Jurassic Entrada Sandstone, Utah, U.S.A., Jesper Milán, David B. Loope

Department of Earth and Atmospheric Sciences: Faculty Publications

The Middle Jurassic Entrada Sandstone, exposed near the town of Escalante, southern Utah, consists of large-scale cross-bedded eolian deposits that are interbedded with horizontally laminated sand sheets and thin sets of eolian cross-strata, representing periods with a moister climate. The flat-bedded units contain numerous tracks and trackways from small to large-sized theropod dinosaurs. These tracks are today exposed in several distinct erosional states, allowing detailed studies of track and undertrack formation in eolian deposits. Tracks that originally were emplaced on sloping surfaces show, in their present-day erosional state, a morphology distinct from those originally emplaced on horizontal surfaces. Further, the …