Earth Sciences Commons^™

Holocene Hydrologic Variation At Lake Titicaca, Bolivia/Peru, And Its Relationship To North Atlantic Climate Variation, P. A. Baker, Sherilyn C. Fritz, J. Garland, E. Ekdahl

Department of Earth and Atmospheric Sciences: Faculty Publications

A growing number of sites in the Northern Hemisphere show centennial- to millennial-scale climate variation that has been correlated with change in solar variability or with change in North Atlantic circulation. However, it is unclear how (or whether) these oscillations in the climate system are manifest in the Southern Hemisphere because of a lack of sites with suitably high sampling resolution. In this paper, we reconstruct the lake-level history of Lake Titicaca, using the carbon isotopic content of sedimentary organic matter, to evaluate centennial-to millennial-scale precipitation variation and its phasing relative to sites in the Northern Hemisphere. The pattern and …

Aquitard Effect On Drawdown In Water Table Aquifers, Vitaly A. Zlotnik, Hongbin Zhan

Department of Earth and Atmospheric Sciences: Faculty Publications

The effects of an aquitard on drawdown in an overlying unconfined aquifer can be represented by a drainage-type term at the aquitard-aquifer interface. The functional form of this boundary condition is similar to the Boulton-Neuman boundary condition used for water table aquifers except the kernel contains an inverse square root of time instead of a negative exponential. Type curves using the new boundary condition were obtained in semianalytical form. Examples for several representative conditions show that the effect of the underlying aquitard can contribute to the type curve at early and intermediate times, but the effect becomes negligible at late …

Women In Oceanography: Women Of The Academy And The Sea, Suzanne O'Connell, Mary Anne Holmes

Department of Earth and Atmospheric Sciences: Faculty Publications

Women have played an active role in all areas of oceanography. Defining the number of women oceanographers is not an easy task because the discipline is so broad and the boundaries between subdisciplines are not always distinct.

The Maastrichtian Record From Shatsky Rise (Northwest Pacific): A Tropical Perspective On Global Ecological And Oceanographic Changes, Tracy D. Frank, Deborah J. Thomas, R. Mark Leckie, Michael A. Arthur, Paul R. Brown, Kelly Jones, Jackie A. Lees

Department of Earth and Atmospheric Sciences: Faculty Publications

We present new isotopic and micropaleontological data from a depth transect on Shatsky Rise that record the response of the tropical Pacific to global biotic and oceanographic shifts during the mid-Maastrichtian. Results reveal a coupling between the upper ocean, characterized by a weak thermocline and low to intermediate productivity, and intermediate waters. During the earliest Maastrichtian, oxygen and neodymium isotope data suggest a significant contribution of relatively warm intermediate water from the North Pacific. Isotopic shifts through the early Maastrichtian suggest that this warmer water mass was gradually replaced by cooler waters originating in the Southern Ocean. Although the cooler …

Calcareous Nannofossil Evidence For The Existence Of The Gulf Stream During The Late Maastrichtian, David K. Watkins, Jean M. Self-Trail

Department of Earth and Atmospheric Sciences: Faculty Publications

Upper Maastrichtian calcareous nannofossil assemblages, from eight cores on the South Carolina Coastal Plain (onshore set) and three deep sea drilling sites from the continental slope and abyssal hills (offshore set), were analyzed by correlation and principal component analysis to examine the ancient surface water thermal structure. In addition, a temperature index derived from independently published paleobiogeographic information was applied to the sample data. All three methods indicate a strong separation of the samples into onshore and offshore sets, with the offshore data set exhibiting significantly warmer paleotemperatures. The great disparity between these two sample sets indicates that there was …

Evidence For Marine Influence On A Low-Gradient Coastal Plain: Ichnology And Invertebrate Paleontology Of The Lower Tongue River Member (Fort Union Formation, Middle Paleocene), Western Williston Basin, U.S.A., Edward S. Belt, Neil E. Tibert, H. Allen Curran, John A. Diemer, Joseph H. Hartman, Timothy J. Kroeger, David M. Harwood

Department of Earth and Atmospheric Sciences: Faculty Publications

The Paleocene Tongue River Member of the Fort Union Formation contains trace-fossil associations indicative of marine influence in otherwise freshwater facies. The identified ichnogenera include: Arenicolites, Diplocraterion, Monocraterion, Ophiomorpha, Rhizocorallium, Skolithos linearis, Teichichnus, Thalassinoides, and one form of uncertain affinity. Two species of the marine diatom Coscinodiscus occur a few meters above the base of the member. The burrows occur in at least five discrete, thin, rippled, fine-grained sandstone beds within the lower 85 m of the member west of the Cedar Creek anticline (CCA) in the Signal Butte, Terry Badlands, and Pine Hills areas. T wo discrete burrowed …

Reply To Comment By H. Lough, Department Of Civil Engineering, University Of Canterbury, Christchurch, New Zealand, On The Paper “Stream Depletion Predictions Using Pumping Test Data From A Heterogeneous Stream–Aquifer System (A Case Study From The Great Plains, Usa)”, S. J. Kollet, Vitaly A. Zlotnik

Department of Earth and Atmospheric Sciences: Faculty Publications

1. General remark

2. The study by Kollet and Zlotnik (2003)

3. Remark on the explanation of the drawdown behavior

4. Remark on the re-analysis of the data from piezometer C2d

5. Summary

Vegetation And Climate Change On The Bolivian Altiplano Between 108,000 And 18,000 Years Ago, Alex Chepstow-Lusty, Mark B. Bush, Michael R. Frogley, Paul A. Baker, Sherilyn C. Fritz, James Aronson

Department of Earth and Atmospheric Sciences: Faculty Publications

A 90,000-yr record of environmental change before 18,000 cal yr B.P. has been constructed using pollen analyses from a sediment core obtained from Salar de Uyuni (3653 m above sea level) on the Bolivian Altiplano. The sequence consists of alternating mud and salt, which reflect shifts between wet and dry periods. Low abundances of aquatic species between 108,000 and 50,000 yr ago (such as Myriophyllum and Isoëtes) and marked fluctuations in Pediastrum suggest generally dry conditions dominated by saltpans. Between 50,000 yr ago and 36,000 cal yr B.P., lacustrine sediments become increasingly dominant. The transition to the formation of …

Vertical Movement Of Water In A High Plains Aquifer Induced By A Pumping Well, Xunhong Chen, Yanfeng Yin, James W. Goeke, Robert F. Diffendal Jr.

Department of Earth and Atmospheric Sciences: Faculty Publications

Field observation and numerical simulations were carried out to evaluate the hydraulic relationship between the shallow and deep aquifer of a High Plains Aquifer system, in which shallow and deep aquifers are separated by an aquitard. Pumping from the lower aquifer resulted in a small drawdown in the upper aquifer and a larger drawdown in the aquitard; pumping from the shallow aquifer caused a small drawdown in the aquitard and the deep aquifer. Analysis of pumping test data gives the values of the hydraulic conductivity of the aquitard and the deep aquifer. Long-term observation of groundwater levels in the shallow …

Do Meteorologists Suppress Thunderstorms? Radar-Derived Statics And The Behavior Of Moist Convection, Matthew D. Parker, Jason C. Knievel

Department of Earth and Atmospheric Sciences: Faculty Publications

Most meteorologists are acquainted with the no- tion of a weather hole—that is, a place that receives less exciting weather than does its surroundings. Exciting weather takes many forms, but when people use the term weather hole, they tend to mean a place that thunderstorms often barely miss, or near which approaching storms often dissipate. For this paper, that is the meaning we adopt.

In our experience, many meteorologists and lay weather enthusiasts genuinely believe that they live in weather holes, and this belief, almost without fail, seems to stem from countless hours spent gazing at displays of radar reflectivity. …

Performance Of Quality Assurance Procedures For An Applied Climate Information System, K. G. Hubbard, S. Goddard, Bill Sorensen, N. Wells, Thomas Osugi

Department of Earth and Atmospheric Sciences: Faculty Publications

Valid data are required to make climate assessments and to make climate-related decisions. The objective of this paper is threefold: to introduce an explicit treatment of Type I and Type II errors in evaluating the performance of quality assurance procedures, to illustrate a quality control approach that allows tailoring to regions and subregions, and to introduce a new spatial regression test. Threshold testing, step change, persistence, and spatial regression were included in a test of three decades of temperature and precipitation data at six weather stations representing different climate regimes. The magnitude of thresholds was addressed in terms of the …

In Memoriam: John Platt Bradbury (1936–2005), Walter Dean, Sherilyn C. Fritz, Cathy Whitlock, William Watts

Department of Earth and Atmospheric Sciences: Faculty Publications

John Platt Bradbury, a former United States Geological Survey (USGS) geologist, and a long time and much valued editorial board member for the Journal of Paleolimnology, died of cancer (abdominal mesothelioma) on August 15, 2005, in the log home that he and his wife Vera Markgraf built in the mountains near Monte Vista, Colorado. Platt’s interest in paleolimnology developed during his graduate school years at the University of New Mexico, working with Roger Anderson and Walt Dean. He received his Ph.D. in 1967. He went on to do post-doctoral research at Yale University under G. Evelyn Hutchinson and then …

High-Resolution Ocean Color Remote Sensing Of Benthic Habitats: A Case Study At The Roatan Island, Honduras, Deepak R. Mishra, Sunil G. Narumalani, Donald Rundquist, Merlin P. Lawson

Department of Earth and Atmospheric Sciences: Faculty Publications

Natural resource managers clamor for detailed reef habitat maps for monitoring smaller scale disturbances in reef communities. Coastal ocean color remote sensing techniques permit benthic habitats to be explored with higher resolution than ever before. The objective of this research was to develop an accurate benthic habitat map for an area off the northwest coast of Roatan Island, Honduras, using high-resolution multispectral IKONOS data. Atmospheric (Rayleigh and aerosol path radiance) and water column corrections (water depth and water column attenuation) were applied to the imagery, making it a robust method for mapping benthic habitats. Water depth for each pixel was …

Groundwater Irrigation In The Development Of The Grand Prairie Rice Industry, 1896-1950, John B. Gates

Department of Earth and Atmospheric Sciences: Faculty Publications

Elucidates some of the ways in which groundwater and groundwater irrigation have affected the Grand Prairie's rice industry over time and conversely how the development of the industry has altered the region's groundwater conditions. Concentrates on aspects of the industry's history that have often been overlooked in favor of rice cultivation's social dimensions and consider hydrological systems not just as resources awaiting exploitation or as simple constraints on production but as variables whose roles and effects can change over time.

New Stratigraphic Subdivision, Depositional Environment, And Age Estimate For The Upper Cretaceous Djadokhta Formation, Southern Ulan Nur Basin, Mongolia, Demberelyin Dashzeveg, Lowell Dingus, David B. Loope, Carl C. Swisher Iii, Togtokh Dulam, Mark R. Sweeney

Department of Earth and Atmospheric Sciences: Faculty Publications

Studies of key and newly discovered sections of the Upper Cretaceous Djadokhta Formation along the southern margin of the Ulan Nur Basin allow a new subdivision based on lithology. The formation and its members were mapped at both Bayn Dzak, an area that includes the Flaming Cliffs, and Tugrugyin Shireh, an area about 50 km to the northwest of Bayn Dzak. Stratigraphic sections at both localities were remeasured. The considerably enlarged formation comprises a lower Bayn Dzak Member, dominated by moderate reddish orange sands with subordinate mudstone units, and an upper Tugrugyin Member, composed of pale orange to light gray …

Calcareous Nannoplankton Response To Late Albian Oceanic Anoxic Event 1d In The Western North Atlantic, David K. Watkins, Matthew J. Cooper, Paul A. Wilson

Department of Earth and Atmospheric Sciences: Faculty Publications

Well-preserved nannofossil and stable isotope records from the mid-Cretaceous of Ocean Drilling Project Leg 171B (western North Atlantic) indicate cyclical, productivity-based variations in surface water characteristics, suggesting orbitally paced changes in upwelling intensity and the strength of deep mixing associated with oceanic anoxic event (OAE)1d. Paleontologic and isotopic evidence suggest that collapse of upper water column stratification associated with OAE1d was preceded by approximately 1 m.y. of progressively decreasing water column stability and increasing surface water fertility. Thirteen species went extinct during a short (ca. 200 k.y.) interval associated with OAE1d. Nine of these have morphological characters suggesting adaptation to …

Holocene Paleoecology Along The Blekinge Coast, Southeast Sweden, And Implications For Climate And Sea-Level Changes, Shi-Yong Yu, Björn E. Berglund, Per Sandgren, Sherilyn C. Fritz

Department of Earth and Atmospheric Sciences: Faculty Publications

To investigate the Holocene vegetation history and shoreline displacement along the southeastern Swedish coast, two radiocarbon dated pollen, macrofossil, and mineral magnetic sequences were studied in the western Blekinge coast: Hunnemara Lake and Smygen Bay. Both pollen records show mosaic vegetation with grasslands, heaths and woodlands prior to 11,300 cal. BP. Pinus-dominated mixed forest was initially established by 11,000 cal. BP. By 10,000 cal. BP, mixed forest with higher species diversity was fully established. Expansion of broad-leaved trees began at about 8,600 cal. BP, indicating the onset of the mid-Holocene thermal maximum in Scandinavia. Following the Ulmus decline ~5,800 …

Patterns Of Early Lake Evolution In Boreal Landscapes: A Comparison Of Stratigraphic Inferences With A Modern Chronosequence In Glacier Bay, Alaska, Sherilyn C. Fritz, Daniel R. Engstrom, Stephen Juggins

Department of Earth and Atmospheric Sciences: Faculty Publications

The chronosequence approach, which infers temporal patterns of environmental change from a spatial array of modern sites, has been a major tool for studying successional processes. A model of early lake ontogeny in boreal landscapes, developed from a chronosequence of lakes in Alaska, suggests that long-term soil development and related hydrological change produce a loss of alkalinity and base cations, a decrease in pH, an increase in DOC and a transient increase followed by a decrease in lakewater nitrogen concentrations over time. We compare this model of lake ontogeny with patterns of change reconstructed from diatom assemblages in 10 sediment …

Low Marine Sulphate And Protracted Oxygenation Of The Proterozoic Biosphere, Linda C. Kah, Timothy W. Lyons, Tracy D. Frank

Department of Earth and Atmospheric Sciences: Faculty Publications

Progressive oxygenation of the Earth’s early biosphere is thought to have resulted in increased sulphide oxidation during continental weathering, leading to a corresponding increase in marine sulphate concentration. Accurate reconstruction of marine sulphate reservoir size is therefore important for interpreting the oxygenation history of early Earth environments. Few data, however, specifically constrain how sulphate concentrations may have changed during the Proterozoic era (2.5–0.54 Gyr ago). Prior to 2.2 Gyr ago, when oxygen began to accumulate in the Earth’s atmosphere, sulphate concentrations are inferred to have been <200 >μM, on the basis of limited isotopic variability preserved in sedimentary sulphides4 and experimental …

Correction To ‘‘A Concept Of Maximum Stream Depletion Rate For Leaky Aquifers In Alluvial Valleys" By Vitaly A. Zlotnik, Vitaly A. Zlotnik

Department of Earth and Atmospheric Sciences: Faculty Publications

In the paper ‘‘A concept of maximum stream depletion rate for leaky aquifers in alluvial valleys’’ by Vitaly A. Zlotnik (Water Resources Research, 40(6), W06507, doi:10.1029/2003WR002932, 2004), equations (24), (25), (A11), and (A12) were published with typographical errors. The correct equations are published below.

Three-Dimensional Modeling Of Lacustrine Diatom Habitat Areas: Improving Paleolimnological Interpretation Of Planktic : Benthic Ratios, Jeffery R. Stone, Sherilyn C. Fritz

Department of Earth and Atmospheric Sciences: Faculty Publications

Three-dimensional modeling of lake morphometry enables the calculation of lake volume, planar surface area, and basin surface area, which are critical components of a conceptual model of how planktic and benthic habitat areas change with changing lake level. We have applied three-dimensional modeling to Foy Lake, Montana, and compared model results of changing ratios of planktic and benthic habitat areas at all possible lake levels to sediment cores recovered from the lake. The model allows us to produce semiquantitative depth reconstructions and greatly improves lake-level reconstruction of this morphometrically complex basin. The conceptual model also was modified to examine the …

Impact Of Heterogeneity, Bed Forms, And Stream Curvature On Subchannel Hyporheic Exchange, M. Bayani Cardenas, J. L. Wilson, Vitaly A. Zlotnik

Department of Earth and Atmospheric Sciences: Faculty Publications

Advection through hyporheic zones (HZ) consisting of heterogeneous channel bend streambed deposits and their equivalent homogenous medium was investigated using finite difference groundwater flow and transport simulations and forward particle tracking. The top prescribed head boundary was varied in order to mimic various stream channel head distributions resulting from the presence of bed forms and channel curvature. Flux calculations show that heterogeneity causes significant additional HZ flux compared to an equivalent homogenous medium. However, the major cause of HZ flux is a spatially periodic (sinusoidal) head distribution along the boundary, representing the effect of bed forms. The additional influence of …

Systematics And Phylogeny Of Late Paleocene And Early Eocene Palaeoryctinae (Mammalia, Insectivora) From The Clarks Fork And Bighorn Basins, Wyoming, Jonathan I. Bloch, Ross Secord, Philip D. Gingerich

Department of Earth and Atmospheric Sciences: Faculty Publications

New specimens of Palaeoryctes punctatus from the middle Clarkforkian of the Clarks Fork Basin include a left dentary preserving the crowns of I₁-C₁, P₃, and M_1-2, with alveoli for P₂, P₄, and M₃. The lower dental formula, previously unknown for this species, is 3.1.3.3. A maxillary fragment preserves the crowns of a broken P⁴, complete M¹, and a broken M². Specimens previously referred to Palaeoryctes cf. P. punctatus and cf. Palaeoryctes sp. from the late Tiffanian are morphologically distinct and …

A Concept Of Maximum Stream Depletion Rate For Leaky Aquifers In Alluvial Valleys, Vitaly A. Zlotnik

Department of Earth and Atmospheric Sciences: Faculty Publications

Existing analytical models for evaluating stream depletion by wells in alluvial aquifers are based on the assumption that stream depletion supplies 100% of groundwater withdrawals. Analysis of specific hydrostratigraphic conditions in leaky aquifers indicates that stream depletion may range from 0 to 100%. A new concept of maximum stream depletion rate (MSDR) is introduced and defined as a maximum fraction of the pumping rate contributed by the stream depletion. Several new analytical solutions indicate that the MSDR is determined by aquifer hydrostratigraphic conditions, geometry of recharge and discharge zones, and locations of pumping wells.

Twentieth Century Water Quality Trends In Minnesota Lakes Compared With Presettlement Variability, Joy M. Ramstack, Sherilyn C. Fritz, Daniel R. Engstrom

Department of Earth and Atmospheric Sciences: Faculty Publications

Abstract: A diatom-based transfer function was used to reconstruct water chemistry before European settlement in 55 Minnesota lakes. The lakes span three natural ecoregions, which differ in their history of land use, as well as in surficial geology, climate, and vegetation. Postsettlement trends were compared with water chemistry change reconstructed from two presettlement core sections (circa 1750 and 1800) as a measure of natural variability. Presettlement water quality changes were generally small and nondirectional in all three ecoregions. In contrast, half of the urban lakes showed a statistically significant increase in chloride, whereas 30% of urban and 30% of agricultural …

What Does It Take To Get Tenure?, Annabelle Foos, Mary Anne Holmes, Suzanne O'Connell

Department of Earth and Atmospheric Sciences: Faculty Publications

Data from the National Science Foundation and the American Geological Institute indicate that women geoscientists remain underrepresented at all levels in academia. In addition, the proportion of women geoscience faculty declines with increasing rank, from around 20 percent as assistant professors to 5 percent as full professors.

In 2001, we began a project to collect information that can help mentor women faculty early in their geoscience careers and improve their chances of obtaining tenure. We also wanted to provide institutions with information on retention, tenure and promotion procedures and criteria as they are practiced across the country.

Tropical Westerlies Over Pangaean Sand Seas, David B. Loope, Maureen B. Steiner, Clinton M. Rowe, Nicholas Lancaster

Department of Earth and Atmospheric Sciences: Faculty Publications

Cross-equatorial, westerly winds are key features of tropical circulation in monsoonal regions. Although prominent in numerical climate models of Pangaea (the supercontinent straddling earth’s equator, Late Paleozoic to Early Mesozoic), such flow has not been confirmed previously by migration directions of ancient dunes. Windblown sandstones that span 100 million years of earth history are widely exposed in south-western USA. If recent paleomagnetic data from the Colorado Plateau are used to correct Mesozoic paleogeographic maps, the Plateau is placed about 10° further south than previously assumed, and the prevailing north-westerly surface winds recorded by dune-deposited sandstones are explicable as cross-equatorial westerlies …

Why Has The Land Memory Changed?, Q. Steven Hu, Yongjun Zheng

Department of Earth and Atmospheric Sciences: Faculty Publications

The ‘‘land memory’’ refers to an interseasonal predictability of the summer monsoon rainfall in the south- western United States, describing a relationship of the summer monsoon rainfall anomaly with anomalies in the antecedent winter season snow and land surface conditions in the western United States. This relationship has varied, however, showing a peculiar on-and-off feature in the last century. It is important to understand this variation so that the relationship can be used to assist making predictions of the monsoon rainfall for that region. This note offers the evidence and shows that the change of the land memory may have …

Paleocene Cyclic Sedimentation In The Western North Atlantic, Odp Site 1051, Blake Nose, Mary Anne Holmes, David K. Watkins, Richard D. Norris

Department of Earth and Atmospheric Sciences: Faculty Publications

Upper Paleocene (zone CP8b) cyclic sediment from Ocean Drilling Program (ODP) Site 1051 on Blake Nose, western North Atlantic, alternates from white carbonate-rich to green carbonate-poor in response to precessional forcing. Compositional differences between the two bed types are minor: mineral and nannofossil composition of the beds vary subtly, but grain size of the terrigenous component and biogenic silica content remain constant. Iron content determined by sediment magnetic susceptibility and iron intensity determined by a core-scanning XRF correlates negatively with carbonate content and are higher in green beds. Kaolinite content of green beds is slightly higher as well. Green beds …

Geology And Paleontology Of The Upper John Day Beds, John Day River Valley, Oregon: Lithostratigraphic And Biochronologic Revision In The Haystack Valley And Kimberly Areas (Kimberly And Mt. Misery Quadrangles), Robert M. Hunt Jr., Ellen Stepleton

Department of Earth and Atmospheric Sciences: Faculty Publications

The John Day Formation of north-central Oregon preserves a succession of speciose, superposed Oligocene through early Miocene mammalian faunas that establish the sequence of mid-Cenozoic mammalian evolution within the Pacific Northwest. Upper John Day rock units initially described by Merriam (1900, 1901) in the Kimberly and Haystack Valley areas were later divided into lower (Kimberly) and upper (Haystack Valley) members by Fisher and Rensberger (1972). We focused our study on the lithostratigraphic succession within the Haystack Valley Member. Rocks previously included in the Haystack Valley Member can be subdivided into four unconformity-bounded, genetic lithostratigraphic units that range in age from …