Physical Sciences and Mathematics Commons^™

Coupled Collaborative In-Class Activities And Individual Follow-Up Homework Promote Interactive Engagement And Improve Student Learning Outcomes In A College-Level Environmental Geology Course, Leilani Arthurs, Alexis Templeton

Department of Earth and Atmospheric Sciences: Faculty Publications

Interactive engagement pedagogies that emerge from a constructivist model of teaching and learning are often a challenge to implement in larger classes for a number of reasons including the physical layout of the classroom (e.g. fixed chairs in an amphitheater-style room), the logistics of organizing a large number of students into small peer-learning groups, the ability of a single instructor to personally interact with each of many small groups, and the design of small group activities that are engaging and facilitate student learning. For a large introductory-level Environmental Geology college course, 5 coupled collaborative class-long in-class activities and individual follow-up …

Evolution Of The Cretaceous Calcareous Nannofossil Genus Eiffellithus And Its Biostratigraphic Significance, J. L. Shamrock, David K. Watkins

Department of Earth and Atmospheric Sciences: Faculty Publications

The calcareous nannofossil genus Eiffellithus is an important taxon of mid- to Upper Cretaceous marine sediments in biostratigraphy and paleoceanography. The definition of species within Eiffellithus have been both broadly interpreted and variably applied by nannofossil workers. This is particularly true for the Eiffellithus eximius plexus. While the taxonomy of mid-Cretaceous Eiffellithus species has recently been well-defined, the remaining 35 m.y. history of the genus has not been closely examined. Our investigation of Cenomanian to Maastrichtian sediments from the Western Interior Seaway, Gulf of Mexico, and Western Atlantic gives rise to six new species of Eiffellithus that can be reliably …

Field Evidence Of A Negative Correlation Between Saturated Hydraulic Conductivity And Soil Carbon In A Sandy Soil, Tiejun Wang, David A. Wedin, Vitaly A. Zlotnik

Department of Earth and Atmospheric Sciences: Faculty Publications

Soil organic matter (SOM) is generally assumed to be positively correlated with saturated hydraulic conductivity (KS). However, recent studies of pedotransfer functions suggest a possible negative KS-SOM relationship that still needs independent verification. Our field KS study of sandy soils in a semiarid region provides such in situ evidence of a negative KS-SOM relationship, which is nonlinear and is strongest at the lowest levels of soil carbon (<0.1%). A regression analysis also shows that soil carbon is an important factor for explaining KS in those soils. The likely reason for the observed negative KS-SOM relationship is a reduced wettability caused by SOM, which is believed to outweigh the impacts of any increase in KS caused by soil aggregation. The low SOM content and large particle size of sand may explain the limited effect of SOM on soil aggregation processes in the examined soils.

Holocene Lake-Level Trends In The Rocky Mountains, Usa, Bryan Shuman, Anna K. Henderson, Steven M. Colman, Jeffery R. Stone, Sherilyn C. Fritz, Lora R. Stevens, Mitchell J. Power, Cathy Whitlock

Department of Earth and Atmospheric Sciences: Faculty Publications

The availability of water shapes life in the western United States, and much of the water in the region originates in the Rocky Mountains. Few studies, however, have explicitly examined the history of water levels in the Rocky Mountains during the Holocene. Here, we examine the past levels of three lakes near the Continental Divide in Montana and Colorado to reconstruct Holocene moisture trends. Using transects of sediment cores and sub-surface geophysical profiles from each lake, we find that mid-Holocene shorelines in the small lakes (4–110 ha) were as much as ~10 m below the modern lake surfaces. Our results …

Reply To The Comments Of W. Helland-Hansen On “Towards The Standardization Of Sequence Stratigraphy” By Catuneanu Et Al. [Earth-Sciences Review 92 (2009), Pp. 1–33], Octavian Catuneanu, V. Abreu, J. P. Bhattacharya, M. D. Blum, R. W. Dalrymple, P. G. Eriksson, Christopher R. Fielding, W. L. Fisher, W. E. Galloway, M. R. Gibling, K. A. Giles, J. M. Holbrook, R. Jordan, C. G. St.C. Kendall, B. Macurda, O. J. Martinsen, A. D. Miall, J. E. Neal, D. Nummedal, L. Pomar, H. W. Posamentier, B. R. Pratt, J. F. Sarg, K. W. Shanley, R. J. Steel, A. Strasser, M. E. Tucker, C. Winker

Department of Earth and Atmospheric Sciences: Faculty Publications

We thank William Helland-Hansen for his compliments and feedback on our paper. We aimed to establish a consensus in sequence stratigraphy by using a neutral approach that focused on model-independent, fundamental concepts, because these are the ones common to various approaches. This search for common ground is what we meant by “standardization,” not the imposition of a strict, inflexible set of rules for the placement of sequence- stratigraphic surfaces. Our work is meant to eliminate the present state of methodological and nomenclatural confusion within sequence stratigraphy, which is largely the result of uncoordinated effort in the development of the method …

Fluvial-Estuarine Reinterpretation Of Large, Isolated Sandstone Bodies In Epicontinental Cyclothems, Upper Pennsylvanian, Northern Midcontinent, Usa, And Their Significance For Understanding Late Paleozoic Sea-Level Fluctuations, Steven A. Fischbein, R. Matthew Joeckel, Christopher R. Fielding

Department of Earth and Atmospheric Sciences: Faculty Publications

The Upper Pennsylvanian Indian Cave Sandstone (ICS) in southeastern Nebraska is herein reinterpreted as three multistory incised valley fills and one single-storey channel fill, altogether representing at least two different intervals of time. ICS lithosomes are linear bodies, as much as 2000 m wide and 30 m thick, incised into pre-existing cyclothems, and have relatively steep sides and flat bases. They include crudely fining-upwards successions of trough cross-bedded sandstones, interpreted as tidally-influenced fluvial deposits, overlain by upper estuarine heterolithic facies, with local coals, and a restricted trace fossil assemblage. The vertical facies succession suggests sediment accumulation in a regime of …

Using Pedotransfer Functions In Vadose Zone Models For Estimating Groundwater Recharge In Semiarid Regions, Tiejun Wang, Vitaly A. Zlotnik, Jirka Šimunek, Marcel G. Schaap

Department of Earth and Atmospheric Sciences: Faculty Publications

Process-based vadose zone models are becoming common tools for evaluating spatial distributions of groundwater recharge (GR), but their applications are restricted by complicated parameterizations, especially because of the need for highly nonlinear and spatially variable soil hydraulic characteristics (SHCs). In an attempt to address the scarcity of field SHC data, pedotransfer functions (PTF) were introduced in earlier attempts to estimate SHCs. However, the accuracy of this method is rarely questioned in spite of significant uncertainties of PTF-estimated SHCs. In this study, we investigated the applicability of coupling vadose zone models and PTFs for evaluating GR in sand and loamy sand …

Antarctic Drilling Recovers Stratigraphic Records From The Continental Margin, David M. Harwood, Fabio Florindo, Franco M. Talarico, Richard Levy, Gerhard Kuhn, Tim Naish, F. Niessen, Ross Powell, Alex Pyne, Gary Wilson

Department of Earth and Atmospheric Sciences: Faculty Publications

The Antarctic Geological Drilling (ANDRILL) program—a collaboration between Germany, Italy, New Zealand, and the United States that is one of the larger programs endorsed by the International Polar Year (IPY; http:// www .ipy .org)—successfully completed the drilling phase of the Southern McMurdo Sound (SMS) Project in December 2007. This second drill core of the program’s campaign in the western Ross Sea, Antarctica, complements the results of the first drilling season [Naish et al., 2007] by penetrating deeper into the stratigraphic section in the Victoria Land Basin and extending the recovered time interval back to approximately 20 million years ago.

The …

Holocene Carbon Burial By Lakes In Sw Greenland, N. J. Anderson, W. D'Andrea, Sherilyn C. Fritz

Department of Earth and Atmospheric Sciences: Faculty Publications

The role of the Arctic in future global change processes is predicted to be important because of the large carbon (C) stocks contained in frozen soils and peatlands. Lakes are an important component of arctic landscapes although their role in storing C is not well prescribed. The area around Kangerlussuaq, SW Greenland (66–68°N, 49–54°W) has ex¬tremely high lake density, with ~20 000 lakes that cover about 14% of the land area. C accumulation rates and standing stock (kg C m⁻²), representing late- to mid-Holocene C burial, were calculated from AMS ¹⁴C-dated sediment cores from 11 lakes. Lake …

Estimating Hydraulic Conductivity From Drainage Patterns Derived From Dem-A Case Study In The Oregon Cascades, B. P. Grudzinski, W. Luo, Darryll T. Pederson

Department of Earth and Atmospheric Sciences: Faculty Publications

Hydraulic conductivity is an important parameter in hydrology which describes the ease with which water moves through porous media. This parameter is also important in understanding the hydrology of Mars. On Earth, this parameter can be measured by conducting controlled experiments in laboratories or conducting pumping tests in the field. This study introduces a new method of estimating hydraulic conductivity from drainage dissection pattern derived from digital elevation model (DEM). This method can be applied to Mars if it is robustly tested on Earth.

Inventories And Mobilization Of Unsaturated Zone Sulfate, Fluoride, And Chloride Related To Land Use Change In Semiarid Regions, Southwestern United States And Australia, Bridget R. Scanlon, David A. Stonestrom, Robert C. Reedy, Fred W. Leaney, John B. Gates, Richard G. Cresswell

Department of Earth and Atmospheric Sciences: Faculty Publications

Unsaturated zone salt reservoirs are potentially mobilized by increased groundwater recharge as semiarid lands are cultivated. This study explores the amounts of pore water sulfate and fluoride relative to chloride in unsaturated zone profiles, evaluates their sources, estimates mobilization due to past land use change, and assesses the impacts on groundwater quality. Inventories of water-extractable chloride, sulfate, and fluoride were determined from borehole samples of soils and sediments collected beneath natural ecosystems (N = 4), nonirrigated ("rain-fed") croplands (N = 18), and irrigated croplands (N = 6) in the southwestern United States and in the Murray Basin, …

Biostratigraphy Of The Hunter Creek Sandstone, Verdi Basin, Washoe County, Nevada, Thomas S. Kelly, Ross Secord

Department of Earth and Atmospheric Sciences: Faculty Publications

The Hunter Creek Sandstone of the Verdi Basin, Nevada, yielded a succession of superposed continental faunal assemblages ranging in age from the late Clarendonian (late Miocene) through the late Blancan (late Pliocene) in the North American land mammal age framework, or ca. 10.5-2.5 Ma. We describe two new local faunas from the Hunter Creek Sandstone: the East Verdi local fauna, of late-medial to late Clarendonian age, which includes Dinohippus cf. D. leardi, Camelidae, ?Antilocapridae, and Mammutidae or Gomphotheriidae; and the Mogul local fauna, of Hemphillian age, which includes Dinohippus sp., Rhinocerotidae, Camelidae (at least two species), Mammut sp., and …

Towards The Standardization Of Sequence Stratigraphy, Octavian Catuneanu, V. Abreu, J. P. Bhattacharya, M. D. Blum, R. W. Dalrymple, P. G. Eriksson, Christopher R. Fielding, W. L. Fisher, W. E. Galloway, M. R. Gibling, K. A. Giles, J. M. Holbrook, R. Jordan, C. G. St.C. Kendall, B. Macurda, O. J. Martinsen, A. D. Miall, J. E. Neal, D. Nummedal, L. Pomar, H. W. Posamentier, B. R. Pratt, J. F. Sarg, K. W. Shanley, R. J. Steel, A. Strasser, M. E. Tucker, C. Winker

Department of Earth and Atmospheric Sciences: Faculty Publications

Sequence stratigraphy emphasizes facies relationships and stratal architecture within a chronological framework. Despite its wide use, sequence stratigraphy has yet to be included in any stratigraphic code or guide. This lack of standardization reflects the existence of competing approaches (or models) and confusing or even conflicting terminology. Standardization of sequence stratigraphy requires the definition of the fundamental model-independent concepts, units, bounding surfaces and workflow that outline the foundation of the method. A standardized scheme needs to be sufficiently broad to encompass all possible choices of approach, rather than being limited to a single approach or model.

A sequence stratigraphic framework …

The Nature And Origin Of Decadal To Millennial Scale Climate Variability In The Southern Tropics Of South America: The Holocene Record Of Lago Umayo, Peru, Paul A. Baker, Sherilyn C. Fritz, Stephen J. Burns, Erik Ekdahl, Catherine A. Rigsby

Department of Earth and Atmospheric Sciences: Faculty Publications

This paper serves two purposes: to review current ideas about the nature and forcing of decadal to millennial scale precipitation variation in the southern tropics of South America during the late Quaternary and to present a new methodology for the reconstruction of precipitation as applied to a Holocene stable isotopic record of carbonate sediments in a tropical Andean lake, Lago Umayo, Peru. The basic thesis of the first part of the paper is that, although modern instrumental records suffice for deducing climate variability at decadal and shorter time scales, these records cannot adequately characterize the nature and forcing of lower-frequency …

Phytoplankton Productivity Across Prairie Saline Lakes Of The Great Plains (Usa): A Step Toward Deciphering Patterns Through Lake Classification Models, Courtney R. Sahm, Jasmine E. Saros, Sherilyn C. Fritz, Christopher L. Osburn, David M. Reineke

Department of Earth and Atmospheric Sciences: Faculty Publications

Abstract: We investigated patterns of primary production across prairie saline lakes in the central and northern Great Plains of the United States. Based on comparative lake sampling in 2004, seasonal predictors of algal primary productivity were identified within subsets of similar lakes using a combination of Akaike's information criterion (AIC) and classification and regression trees (CART). These models indicated complex patterns of nutrient limitation by nitrogen (N), phosphorus (P), and iron (Fe) within different lake groups. Nutrient enrichment assays (control, + Fe, + N, + P, + N + P) were performed in spring and summer of 2006 to determine …

Evolution Of The Cretaceous Calcareous Nanofossil Genus Eiffellithus And Its Biostratigraphic Significance, Jamie L. Shamrock, David K. Watkins

Department of Earth and Atmospheric Sciences: Faculty Publications

The calcareous nanofossil genus Eiffellithus is an important taxon of mid- to Upper Cretaceous marine sediments in biostratigraphy and paleoceanography. The definition of species within Eiffellithus have been both broadly interpreted and variably applied by nanofossil workers. This is particularly true for the Eiffellithus eximius plexus. While the taxonomy of mid-Cretaceous Eiffellithus species has recently been well-defined, the remaining 35 m.y. history of the genus has not been closely examined. Our investigation of Cenomanian to Maastrichtian sediments from the Western Interior Seaway, Gulf of Mexico, and Western Atlantic gives rise to six new species of Eiffellithus that can be reliably …

High-Resolution Calcareous Nannofossil Biostratigraphy For The Coniacian/Santonian Stage Boundary, Western Interior Basin, Stacie A. Blair, David K. Watkins

Department of Earth and Atmospheric Sciences: Faculty Publications

The Ten Mile Creek area (Dallas, Texas) is a proposed Global Stratotype Section and Point (GSSP) candidate for the Coniacian/Santonian Stage boundary. The Santonian Working Group has designated the first appearance of Inoc¬eramus (Cladoceramus) undulatoplicatus as the diagnostic macrofossil bioevent for the base of the Santonian Stage. Cal¬careous nannofossils were examined from sediments of the Bruceville Marl at the proposed GSSP site and from well-preserved sediments of the coeval Smoky Hill Member-type area (northwestern Kansas) of the Niobrara Formation. Nannofossil bioevents were correlated with the lowest stratigraphic occurrence of I. undulatoplicatus to create a high resolution biostratigraphic framework and stratigraphic …

Clues To The Medieval Destabilization Of The Nebraska Sand Hills, Usa, From Ancient Pocket Gopher Burrows, Rebecca L. Schmeisser, David B. Loope, David A. Wedin

Department of Earth and Atmospheric Sciences: Faculty Publications

The Nebraska Sand Hills are a stabilized dune field in the central United States that reflect past conditions of drought. The most recent drought, known as the Medieval Climatic Anomaly, occurred from A.D. 900 to A.D. 1300 and had an enormous effect on the thriving prairie ecosystem, which included large populations of the plains pocket gopher (Geomys bursarius). Burrows of these organisms across a paleosol-eolian sand boundary in the Sand Hills indicate abrupt climate change during the transition from stabilized to active dune field and from humid to arid conditions. Medieval gophers tunneled at greater depths below the …

Long-Legged Pursuit Carnivorans (Amphicyonidae, Daphoeninae) From The Earlymiocene Of North America, Robert M. Hunt Jr.

Department of Earth and Atmospheric Sciences: Faculty Publications

In the early Miocene, endemic North American amphicyonids of the subfamily Daphoeninae evolved a lineage of large beardogs adapted for prey pursuit over open terrain. Three species comprise this lineage, here placed in the genus Daphoenodon, subgenus Borocyon Peterson, 1910, the sister subgenus to the daphoenine beardog Daphoenodon (Daphoenodon). These species (Borocyon robustum, B. niobrarensis, B. neomexicanus, n. sp.) are distinguished by limbs modified for fore–aft motion and parasagittal alignment contributing to a lengthened stride. These adaptive features are most evident in the terminal species, B. robustum, where the forelimb is conspicuously …

Paleohydrology Of Kangerlussuaq (Søndre Strømfjord), West Greenland During The Last ~8,000 Years, Frank Aebly, Sherilyn C. Fritz

Department of Earth and Atmospheric Sciences: Faculty Publications

Major fluctuations of hydroclimate in West Greenland are recorded in paleoshoreline terraces that encircle several lakes near Kangerlussuaq, Greenland (67°01’N, 50°40’W). Geomorphic and stratigraphic analyses were used to construct a lake-level curve for Hunde Sø, a large closed-basin lake in this region. Changes in lake volume associated with lake-level fluctuations were calculated, and a water-balance model was used to determine the primary factors influencing lake volume and the changes in those factors necessary to affect reconstructed lake-level change. Sensitivity tests suggest that mean annual precipitation and the relative proportion of summer versus winter precipitation are the primary climate drivers of …

Interannual Variations In The Opening Date Of The Prudhoe Bay Shipping Season: Links To Atmospheric And Surface Conditions, Sheldon D. Drobot, James A. Maslanik, Mark R. Anderson

Department of Earth and Atmospheric Sciences: Faculty Publications

This paper examines interannual variability in the opening date for the Prudhoe Bay shipping season (1953-2005), considers how variations in antecedent sea-ice and atmospheric conditions influence the opening date, and then develops a forecasting technique to predict whether the opening date will be early, normal, or late. Analysis of antecedent sea ice and atmospheric conditions indicates that there are significant differences in the Bering Sea ice cover as early as February in years preceding early versus late opening dates. In particular, prior to early opening years, the sea-ice cover in the southern Bering Sea is reduced in February, and as …

Chapter 13: Space- And Ground-Based Studies Of Lightning Signatures, Timothy Hamlin, Kyle Wiens, Abram Jacobson, Tracey E. L. Light, Kenneth B. Eack

Department of Earth and Atmospheric Sciences: Faculty Publications

This article provides a brief survey of the space- and ground-based studies of lightning performed by investigators at Los Alamos National Laboratory (LANL). The primary goal of these studies was to further understand unique lightning signatures known as Narrow Bipolar Events (NBEs). First, an overview is presented of the Fast On-orbit Recording of Transient Events (FORTE) satellite and of the ground-based Los Alamos Sferic Array (LASA). This is followed by a summary of the phenomenology, physics, and meteorological context of NBEs and NBE-related discharges. This article also discusses additional radio frequency and optical observations of lightning made by the FORTE …

Estimating Hydraulic Conductivity From Drainage Patterns Derived From Dem -- A Case Study In The Oregon Cascades, B. P. Grudzinski, W. Luo, Daryll Pederson

Department of Earth and Atmospheric Sciences: Faculty Publications

Hydraulic conductivity is an important parameter in hydrology which describes the ease with which water moves through porous media. This parameter is also important in understanding the hydrology of Mars. On Earth, this parameter can be measured by conducting controlled experiments in laboratories or conducting pumping tests in the field. This study introduces a new method of estimating hydraulic conductivity from drainage dissection pattern derived from digital elevation model (DEM). This method can be applied to Mars if it is robustly tested on Earth.

Paleolimnological Evidence Of The Effects On Lakes Of Energy And Mass Transfer From Climate And Humans, Peter R. Leavitt, Sherilyn C. Fritz, N. J. Anderson, P. A. Baker, T. Blenckner, L. Bunting, J. Catalan, D. J. Conley, W. O. Hobbs, E. Jeppesen, A. Korhola, S. Mcgowan, K. Rühland, J. A. Rusak, G. L. Simpson, N. Solovieva, J. Werne

Department of Earth and Atmospheric Sciences: Faculty Publications

The premise of this article is that climate effects on lakes can be quantified most effectively by the integration of process-oriented limnological studies with paleolimnological research, particularly when both disciplines operate within a common conceptual framework. To this end, the energy (E)–mass (m) flux framework (Em flux) is developed and applied to selected retrospective studies to demonstrate that climate variability regulates lake structure and function over diverse temporal and spatial scales through four main pathways: rapid direct transfer of E to the lake surface by irradiance, heat, and wind; slow indirect effects of E via changes in …

Detecting Source Regions Of Wave Activities In The Tropical Atmosphere By Applying Beamforming To Interpolated Data Grids, Q. Steven Hu, Zhaoning Liang

Department of Earth and Atmospheric Sciences: Faculty Publications

Wave activities are primary sources of weather disturbances and cyclones in the tropical atmosphere. One such activity is the intraseasonal variations in wind, convection, and precipitation in the tropical Indian and western tropical Pacific region. These variations affect the intensity, break and reset, and rainfall in the Indian and the East Asian monsoons. Detecting the source regions of these wave activities is essential for understanding and for prediction of wave development. In this study, a fixed beamforming method is proposed to deduce source regions of some wave activities in the tropical atmosphere. This method is tested with simulations of single …

Obliquity-Paced Pliocene West Antarctic Ice Sheet Oscillations, T. Naish, R. D. Powell, R. Levy, G. Wilson, R. Scherer, F. Talarico, L. Krissek, F. Niessen, M. Pompilio, T. J. Wilson, L. Carter, R. Deconto, P. Huybers, R. Mckay, D. Pollard, J. Ross, D. Winter, P. Barrett, G. Browne, R. Cody, E. A. Cowan, J. Crampton, G. Dunbar, N. Dunbar, F. Florindo, C. Gebhardt, I. Graham, M. Hannah, D. Hansaraj, David M. Harwood, D. Helling, S. Henrys, L. Hinnov, G. Kuhn, P. Kyle, A. La¨Ufer, P. Maffioli, D. Magens, K. Mandernack, W. Mcintosh, C. Millan, R. Morin, C. Ohneiser, T. Paulsen, D. Persico, I. Raine, J. Reed, C. Riesselman, L. Sagnotti, D. Schmitt, C. Sjunneskog, P. Strong, M. Taviani, S. Vogel, T. Wilch, T. Williams

Department of Earth and Atmospheric Sciences: Faculty Publications

Thirty years after oxygen isotope records frommicrofossils deposited in ocean sediments confirmed the hypothesis that variations in the Earth’s orbital geometry control the ice ages¹, fundamental questions remain over the response of the Antarctic ice sheets to orbital cycles². Furthermore, an understanding of the behaviour of the marinebased West Antarctic ice sheet (WAIS) during the ‘warmerthan- present’ early-Pliocene epoch ( ~5–3Myr ago) is needed to better constrain the possible range of ice-sheet behaviour in the context of future global warming³. Here we present a marine glacial record from the upper 600mof the AND-1B sediment …

Does Sedimentary 231Pa/230Th From The Bermuda Rise Monitor Past Atlantic Meridional Overturning Circulation?, Jörg Lippold, Jens Grützner, Diane Winter, Yann Lahaye, Augusto Mangini, Marcus Christl

Department of Earth and Atmospheric Sciences: Faculty Publications

Ocean circulation may have undergone reductions and reinvigorations in the past closely tied to regional climate changes. Measurements of ²³¹Pa/²³⁰Th ratios in a sediment core from the Bermuda Rise have been interpreted as evidence that the Atlantic Meridional Overturning Circulation (AMOC) was weakened or completely eliminated during a period of catastrophic iceberg discharges (Heinrich-Event 1, H1). Here we present new data from the Bermuda Rise that show further ²³¹Pa/²³⁰Th peaks during Heinrich-2 (H2) and Heinrich-3 (H3). Additionally, a tight correlation between diatom abundances (biogenic silica) and ²³¹Pa/²³⁰Th is discovered in this …

The Dilemma Of Disappearing Diatoms: Incorporating Diatom Dissolution Data Into Paleoenvironmental Modeling And Reconstruction, David B. Ryves, Richard W. Battarbee, Sherilyn C. Fritz

Department of Earth and Atmospheric Sciences: Faculty Publications

Taphonomic issues pose fundamental challenges for Quaternary scientists to recover environmental signals from biological proxies and make accurate inferences of past environments. The problem of microfossil preservation, specifically diatom dissolution, remains an important, but often overlooked, source of error in both qualitative and quantitative reconstructions of key variables from fossil samples, especially those using relative abundance data. A first step to tackling this complex issue is establishing an objective method of assessing preservation (here, diatom dissolution) that can be applied by different analysts and incorporated into routine counting strategies. Here, we establish a methodology for assessment of diatom dissolution under …

On The Role Of Groundwater And Soil Texture In The Regional Water Balance: An Investigation Of The Nebraska Sand Hills, Usa, Tiejun Wang, Erkan Istanbulluoglu, John D. Lenters, Durelle T. Scott

Department of Earth and Atmospheric Sciences: Faculty Publications

Partitioning of precipitation between evapotranspiration and runoff at the basin scale is primarily controlled by climate and basin characteristics. Here we use the Budyko hypothesis to investigate the impacts of soil texture and groundwater (e.g., baseflow) on annual and long-term mean annual water balances of basins in a semiarid region located in and around the Sand Hills region of Nebraska, USA. Native grasslands are dominant across the study area with soil textures dramatically different for the Nebraska Sand Hills (primarily sand deposits) and the adjacent regions (mainly less permeable silt loam). For each basin, long-term hydrologic and meteorological data are …