Earth Sciences Commons^™

Provenance Of Sand In Periglacial Sand Wedges And Sheet Sand, Northeastern Nebraska, Usa, William J. Wayne

Department of Earth and Atmospheric Sciences: Faculty Publications

Sand-wedge polygons on upland surfaces beneath thin loess in northeastern Nebraska record existence of permafrost around the margin of the Wisconsinan glacier at its maximum advance. Strong unidirectional wind not only kept the upland surfaces free of snow, allowing frost to penetrate deeply and thermal contraction cracks to develop, but also dessicated the surface material so that frost action and sublimation of pore ice could loosen surface material. The strong NW-SE winds deflated soils from upland surfaces, made ventifacts of the cobbles in the lag that remained and created fields of yardangs oriented NW-SE. Sand derived from the soils and …

Early Deglaciation In The Tropical Andes, G. O. Seltzer, D. T. Rodbell, P. A. Baker, Sherilyn C. Fritz, P. M. Tapia, H. D. Rowe, R. B. Dunbar, Peter U. Clark

Department of Earth and Atmospheric Sciences: Faculty Publications

Analysis of sediment records from lakes located beyond the glacial limit in the Andes has provided, for the first time, an independent assessment of effective moisture ( precipitation minus evaporation) and the timing of the last glaciation (1). Conditions were wet at the LGM and remained so until approximately 15,000 cal yr B.P. (2). However, deglaciation was under way from the LGM between 22,000 and 19,500 cal yr B.P., which reinforces the observation that deglaciation in the tropical Andes was primarily forced by an increase in mean annual temperature during a wet postglacial interval (3, 4).

Development And Implementation Of A Comprehensive Lake And Reservoir Strategy For Nebraska As A Model For Agricultural Dominated Ecosystems, John C. Holz, James W. Merchant, Anatoly A. Gitelson, Sherilyn C. Fritz, Kyle D. Hoagland, Istvan Bogardi, Donald C. Rundquist

Department of Earth and Atmospheric Sciences: Faculty Publications

In agriculturally dominated regions, land use practices have an unusually large impact on water bodies and, therefore, land use may reduce the utility of current ecoregion-based approaches to lake classification by dampening the signals that underlie the ecoregion framework. A team of water quality researchers has been assembled to develop a comprehensive classification scheme for agriculturally dominated ecosystems, using Nebraska as a highly representative model. Three objectives critical to achieving this goal are to establish: (1) a protocol for aggregating water bodies in agricultural ecosystems into classification strata and identifying reference conditions for these classes; (2) the role of remote …

The Mount Feather Diamicton Of The Sirius Group: An Accumulation Of Indicators Of Neogene Antarctic Glacial And Climatic History, G. A. Wilson, J. A. Barron, A. C. Ashworth, R. A. Askin, J. A. Carter, M. G. Curren, D. H. Dalhuisen, E. I. Friedmann, D. G. Fyodorov-Davidov, D. A. Gilichinsky, M. A. Harper, David M. Harwood, J. F. Hiemstra, T. R. Janecek, K. J. Licht, V. E. Ostroumov, R. D. Powell, E. M. Rivkina, S. A. Rose, A. P. Stroeven, P. Stroeven, J. J. M. Van Der Meer, M. C. Wizevich

Department of Earth and Atmospheric Sciences: Faculty Publications

A paucity of data from the Antarctic continent has resulted in conflicting interpretations of Neogene Antarctic glacial history. Much of the debate centres on interpretations of the glacigene Sirius Group strata that crop out as discrete deposits along the length of the Transantarctic Mountains and in particular on its age and the origin of the siliceous microfossils it encloses. Pliocene marine diatoms enclosed within Sirius Group strata are inferred to indicate a dynamic East Antarctic ice sheet that was much reduced, compared with today, in the early-middle Pliocene and then expanded again in the late Pliocene. However, the geomorphology of …

Geomorphic Effectiveness, Sandur Development, And The Pattern Of Landscape Response During Jökulhlaups: Skeiöarársandur, Southeastern Iceland, F. J. Magilligan, B. Gomez, L. A. K. Mertes, L. C. Smith, Norman D. Smith, D. Finnegan, J. B. Garvin

Department of Earth and Atmospheric Sciences: Faculty Publications

By contrast with other historical outburst floods on Skeióarársandur, the 1996 jökulhlaup was unprecedented in its magnitude and duration, attaining a peak discharge of ~53,000 m³/s in <17 h. Using a combination of field sampling and remote sensing techniques (Landsat TM, SAR interferometry, airphotos, and laser altimetry), we document the sandur-wide geomorphic impacts of this event. These impacts varied widely across the Skeióarársandur and cannot be singularly attributed to jökulhlaup magnitude because pre-jökulhlaup glacial dynamics and the extant setting largely conditioned the spatial pattern, type, and magnitude of these impacts. Topographic lowering and asymmetric retreat of the ice front during the late twentieth century has decoupled the ice sheet from the moraine/sandur complex along the central and western sandur. This glacial control, in combination with the convex topography of the proximal sandur, promoted a shift from a primarily diffuse-source braided outwash system to a more point-sourced, channelized discharge of water and sediment. Deposition dominated within the proglacial depression, with approximately 3.8*10⁷ m³ of sediment, and along channel systems that remained connected to subglacial sediment supplies. This shift to a laterally dissimilar, channelized routing system creates a more varied depositional pattern that is not explicitly controlled by the concave longitudinal profile down-sandur. Laterally contiguous units, therefore, may vary greatly in age and sediment character, suggesting that current facies models inadequately characterize sediment transfers when the ice front is decoupled from its …

Groundwater Flow To A Horizontal Or Slanted Well In An Unconfined Aquifer, Hongbin Zhan, Vitaly A. Zlotnik

Department of Earth and Atmospheric Sciences: Faculty Publications

New semianalytical solutions for evaluation of the drawdown near horizontal and slanted wells with finite length screens in unconfined aquifers are presented. These fully three-dimensional solutions consider instantaneous drainage or delayed yield and aquifer anisotropy. As a basis, solution for the drawdown created by a point source in a uniform anisotropic unconfined aquifer is derived in Laplace domain. Using superposition, the point source solution is extended to the cases of the horizontal and slanted wells. The previous solutions for vertical wells can be described as a special case of the new solutions. Numerical Laplace inversion allows effective evaluation of the …

Early Warming Of Tropical South America At The Last Glacial-Interglacial Transition, G. O. Seltzer, D. T. Rodbell, P. A. Baker, Sherilyn C. Fritz, P. M. Tapia, H. D. Rowe, R. B. Dunbar

Department of Earth and Atmospheric Sciences: Faculty Publications

Glaciation in the humid tropical Andes is a sensitive indicator of mean annual temperature. Here, we present sedimentological data from lakes beyond the glacial limit in the tropical Andes indicating that deglaciation from the Last Glacial Maximum led substantial warming at high northern latitudes. Deglaciation from glacial maximum positions at Lake Titicaca, Peru/Bolivia (16°S), and Lake Junin, Peru (11°S), occurred 22,000 to 19,500 calendar years before the present, several thousand years before the Bølling-Allerød warming of the Northern Hemisphere and deglaciation of the Sierra Nevada, United States (36.5° to 38°N). The tropical Andes deglaciated while climatic conditions remained regionally wet, …

Late-Quaternary Lowstands Of Lake Titicaca: Evidence From High-Resolution Seismic Data, Karin D'Agostino, Geoffrey Seltzer, Paul A. Baker, Sherilyn C. Fritz, Robert Dunbar

Department of Earth and Atmospheric Sciences: Faculty Publications

Approximately 600 km of high-resolution seismic reflection data were collected to investigate the late-Quaternary stratigraphic development of Lake Titicaca. The focus of this report is on two seismic sequence boundaries, which are interpreted as erosional surfaces formed at times of low lake level. The younger erosional surface occurs as much as 90 m below the present lake level and up to 8 m below the present sediment–water interface. This erosional surface is interpreted to be coeval with a well-documented early- to mid-Holocene lowstand, dated between ~8,000 and 3,600 cal yr BP. An earlier and previously unknown erosional surface occurs at …

Dynamic Interpretation Of Slug Tests In Highly Permeable Aquifers, Brian R. Zurbuchen, Vitalya. Zlotnik, James J. Butler Jr.

Department of Earth and Atmospheric Sciences: Faculty Publications

Considerable progress has been made in developing a theoretical framework for modeling slug test responses in formations with high hydraulic conductivity K. However, several questions of practical significance remain unresolved. Given the rapid and often oscillatory nature of test responses, the traditional hydrostatic relationship between the water level and the transducer-measured head in the water column may not be appropriate. A general dynamic interpretation is proposed that describes the relationship between water level response and transducer-measured head. This theory is utilized to develop a procedure for transforming model-generated water level responses to transducer readings. The magnitude of the difference …

Upper Cretaceous Diatom Biostratigraphy Of The Arctic Archipelago And Northern Continental Margin, Canada, Pedro M. Tapia, David M. Harwood

Department of Earth and Atmospheric Sciences: Faculty Publications

Strata in the Canadian Arctic contain diverse and moderately well-preserved Late Cretaceous siliceous microfossil assemblages. One-hundred-twelve samples were analyzed from a composite stratigraphic section (1094m-thick) of the Smoking Hills, Mason River and Kanguk formations. Four sections were examined: (1) Slidre Fjord on Ellesmere Island; (2) Hoodoo Dome on Ellef Ringnes Island; (3) Cape Nares on Eglinton Island; and (4) Horton River on the Anderson Plains, Northwest Territories. Two hundred- three diatom taxa were identified in forty-nine productive samples. Four Upper Cretaceous diatom zones are proposed for the Canadian Arctic based on the biostratigraphic distribution of diatoms: (i) the Upper Cenomanian …

New Amphicyonid Carnivorans (Mammalia, Daphoeninae) From The Early Miocene Of Southeastern Wyoming, Robert M. Hunt Jr.

Department of Earth and Atmospheric Sciences: Faculty Publications

Latest Arikareean sediments of the upper Arikaree Group in southeastern Wyoming produced rare fossils of large, early Miocene amphicyonid carnivorans for field parties of the Frick Laboratory, American Museum, from 1932 to 1940. Recent geologic field investigations, including mapping, have discovered additional remains of these carnivorans, clarifying their geographic and stratigraphic distribution, and permitting a more informed description of the earlier collections. These carnivorans come from tuffaceous sandstones of the Upper Harrison beds, the terminal formation-rank unit of the Arikaree Group in southeastern Wyoming. A large species of the amphicyonid Daphoenodon (D. falkenbachi, n. sp.) occurs in northern …

Intercontinental Migration Of Neogene Amphicyonids (Mammalia, Carnivora): Appearance Of The Eurasian Beardog Ysengrinia In North America, Robert M. Hunt Jr.

Department of Earth and Atmospheric Sciences: Faculty Publications

At the beginning of the Neogene a remarkable faunal turnover occurred within the North American carnivore community. The dominant larger Oligocene carnivores (creodonts, nimravid cats, the amphicyonid Daphoenus) became extinct during the late Oligocene and were replaced in the early Miocene by amphicyonine amphicyonids and hemicyonine ursids that entered North America from Eurasia. During a five million-year interval from ~23 to 18 Ma, large amphicyonines appear in late Arikareean and early Hemingfordian faunas of the North American midcontinent. Although most fossils are from western Nebraska and southeastern Wyoming, occurrences of amphicyonines at several sites in the eastern United States …

Concordant Paleolatitudes For Neoproterozoic Ophiolitic Rocks Of The Trinity Complex, Klamath Mountains, California, Edward A. Mankinen, Nancy Lindsley-Griffin, John R. Griffin

Department of Earth and Atmospheric Sciences: Faculty Publications

New paleomagnetic results from the eastern Klamath Mountains of northern California show that Neoproterozoic rocks of the Trinity ophiolitic complex and overlying Middle Devonian volcanic rocks are latitudinally concordant with cratonal North America. Combining paleomagnetic data with regional geologic and faunal evidence suggests that the Trinity Complex and related terranes of the eastern Klamath plate were linked in some fashion to the North American craton throughout that time, but that distance between them may have varied considerably. A possible model that is consistent with our paleomagnetic results and the geologic evidence is that the Trinity Complex formed and migrated parallel …

Arctic Ocean Snow Melt Onset Dates Derived From Passive Microwave, A New Data Set, Mark R. Anderson, Sheldon D. Drobot

Department of Earth and Atmospheric Sciences: Faculty Publications

Snow melt onset is defined as the point in time when the appearance of liquid water in the snow pack changes the crystalline structure within the pack. Owing to the associated increase in surface albedo during melt, surface energy absorption increases rapidly after the onset of snow melt. Monitoring interannual variations in snow melt onset is therefore useful for accurately modeling surface conditions, and it is also valuable for validating climate models and detecting climate change. Since microwave emission changes rapidly when liquid water appears in the snow pack, passive microwave remote sensing techniques can monitor melt onset. Passive microwave …

An Improved Method For Determining Snowmelt Onset Dates Over Arctic Sea Ice Using Scanning Multichannel Microwave Radiometer And Special Sensor Microwave/Imager Data, Sheldon D. Drobot, Mark R. Anderson

Department of Earth and Atmospheric Sciences: Faculty Publications

Ablation of snow over sea ice is an important physical process affecting the Arctic surface energy balance. An improved understanding of the spatial and temporal variations in snowmelt onset could be utilized to improve climate simulations in the Arctic, as well as monitor the Arctic for signs of climate change. Utilizing an updated approach for monitoring snowmelt onset over Arctic sea ice, spatial variability in passive microwave derived snowmelt onset dates is examined from 1979 through 1998. The improved technique, termed the advanced horizontal range algorithm (AHRA), utilizes temporal variations in 18/19G Hz and 37 GHz passive microwave horizontal brightness …

Orbitally Induced Oscillations In The East Antarctic Ice Sheet At The Oligocene/Miocene Boundary, Tim R. Naish, Ken J. Woolfe, Peter J. Barrett, Gary S. Wilson, Cliff Atkins, Steven M. Bohaty, Christian J. Bücker, Michele Claps, Fred J. Davey, Gavin B. Dunbar, Alistair G. Dunn, Christopher R. Fielding, Fabio Florindo, Michael J. Hannah, David M. Harwood, Stuart A. Henrys, Lawrence A. Krissek, Mark Lavelle, Jaap Van Der Meer, William C. Mcintosh, Frank Niessen, Sandra Passchier, Ross D. Powell, Andrew P. Roberts, Leonardo Sagnotti, Reed P. Scherer, C. Percy Strong, Franco Talarico, Kenneth L. Verosub, Giuliana Villa, David K. Watkins, Peter-N. Webb, Thomas Wonik

Department of Earth and Atmospheric Sciences: Faculty Publications

Between 34 and 15 million years (Myr) ago, when planetary temperatures were 3-4°C warmer than at present and atmospheric CO₂ concentrations were twice as high as today, the Antarctic ice sheets may have been unstable. Oxygen isotope records from deep-sea sediment cores suggest that during this time fluctuations in global temperatures and high-latitude continental ice volumes were influenced by orbital cycles. But it has hitherto not been possible to calibrate the inferred changes in ice volume with direct evidence for oscillations of the Antarctic ice sheets. Here we present sediment data from shallow marine cores in the western Ross …

Experimental Diatom Dissolution And The Quantification Of Microfossil Preservation In Sediments, D. B. Ryves, S. Juggins, Sherilyn C. Fritz, R. W. Battarbee

Department of Earth and Atmospheric Sciences: Faculty Publications

Four laboratory experiments on fresh, modern diatoms collected from lakes in the Northern Great Plains of North America were carried out to assess the effects of dissolution on diatom abundance and composition. Marked differences in mean dissolution susceptibility exist between species, despite sometimes significant intra- specific variation between heterovalves. Twenty-four taxa were ranked according to susceptibility to dissolution using an exponential decay model of valve abundance. This dissolution ranking was used to derive two weighted indices of sample preservation. A third index (F) was based on a simple binary classification of valve morphology into dissolved and pristine categories, …

Late Quaternary Climate And Hydrology Of Tropical South America Inferred From An Isotopic And Chemical Model Of Lake Titicaca, Bolivia And Peru, Scott L. Cross, Paul A. Baker, Geoffrey O. Seltzer, Sherilyn C. Fritz, Robert B. Dunbar

Department of Earth and Atmospheric Sciences: Faculty Publications

A simple mass balance model provides insight into the hydrologic, isotopic, and chemical responses of Lake Titicaca to past climatic changes. Latest Pleistocene climate of the Altiplano is assumed to have been 20% wetter and 5°C colder than today, based on previous modeling. Our simulation of lacustrine change since 15,000 cal yr B.P. is forced by these modeled climate changes. The latest Pleistocene Lake Titicaca was deep, fresh, and overflowing. The latest Pleistocene riverine discharge from the lake was about 8 times greater than the modern average, sufficient to allow the expansion of the great paleolake Tauca on the central …

Tropical Climate Changes At Millennial And Orbital Timescales On The Bolivian Altiplano, Paul A. Baker, Catherine A. Rigsby, Geoffrey O. Seltzer, Sherilyn C. Fritz, Tim K. Lowenstein, Niklas P. Bacher, Carlos Veliz

Department of Earth and Atmospheric Sciences: Faculty Publications

Tropical South America is one of the three main centers of the global, zonal overturning circulation of the equatorial atmosphere (generally termed the “Walker” circulation). Although this area plays a key role in global climate cycles, little is known about South American climate history. Here we describe sediment cores and down-hole logging results of deep drilling in the Salar de Uyuni, on the Bolivian Altiplano, located in the tropical Andes. We demonstrate that during the past 50,000 years the Altiplano underwent important changes in effective moisture at both orbital (20,000-year) and millennial timescales. Long-duration wet periods, such as the Last …

The History Of South American Tropical Precipitation For The Past 25,000 Years, Paul A. Baker, Geoffrey O. Seltzer, Sherilyn C. Fritz, Robert B. Dunbar, Matthew J. Grove, Pedro M. Tapia, Scott L. Cross, Harold D. Rowe, James P. Broda

Department of Earth and Atmospheric Sciences: Faculty Publications

Long sediment cores recovered from the deep portions of Lake Titicaca are used to reconstruct the precipitation history of tropical South America for the past 25,000 years. Lake Titicaca was a deep, fresh, and continuously overflowing lake during the last glacial stage, from before 25,000 to 15,000 calibrated years before the present (cal yr B.P.), signifying that during the last glacial maximum (LGM), the Altiplano of Bolivia and Peru and much of the Amazon basin were wetter than today. The LGM in this part of the Andes is dated at 21,000 cal yr B.P., approximately coincident with the global LGM. …

Calcareous Nannofossils From Cape Roberts Project Drillhole Crp-3, Victoria Land Basin, Antarctica, David K. Watkins, S. W. Wise Jr., G. Villa

Department of Earth and Atmospheric Sciences: Faculty Publications

Fossil specimens of the exclusively oceanic calcareous nannoplankton were found only in the upper 200 m of the Cape Roberts Project 3 (CRP-3) cores. These assemblages are depauperate and sporadic in occurrence. The majority of the assemblages contain fewer than 4 species, indicating a severe palaeoecological restriction. The clear domination of these assemblages by reticulofenestrid species, coupled with the almost total exclusion of Coccolithus pelagicus, indicates cold surface water conditions in the Victoria Land Basin during the lives of these poor algae. These cold surface water conditions, perhaps coupled with abnormal surface water chemistry, excluded almost all of the …

Vertical Profiles Of Streambed Hydraulic Conductivity Determined Using Slug Tests In Central And Western Nebraska, David L. Rus, Virginia L. Mcguire, Brian R. Zurbuchen, Vitaly A. Zlotnik

Department of Earth and Atmospheric Sciences: Faculty Publications

Many issues of water-resources management rely on modeling of ground-water/surface-water interactions, and streambed hydraulic conductivity is a key parameter controlling the water fluxes across the stream/aquifer interface. However, in central and western Nebraska, this parameter is generally undefined. The U.S. Geological Survey, in cooperation with the Nebraska Platte River Cooperative Hydrology Study Group, performed slug tests at 15 steam sites in the Platte, Republican, and Little Blue River watersheds to determine the hydraulic conductivity of streambeds in central and western Nebraska. Slug tests were completed at several discrete depth intevals using pneumatic or mechanical methods, and the water-level response was …

Small Oligocene Amphicyonids From North America (Paradaphoenus, Mammalia, Carnivora), Robert M. Hunt Jr.

Department of Earth and Atmospheric Sciences: Faculty Publications

North American amphicyonid camivorans are important members of the mid-Cenozoic terrestrial carnivore community during the late Eocene to late Miocene (Duchesnean to Clarendonian). Species range in size from < 5 kg to > 200 kg. Among the smallest and rarest amphicyonids are Oligocene species of Paradaphoenus Wortman and Matthew, found at a few localities in the Great Plains and the Pacific Northwest. Paradaphoenus is known from only 10 individuals placed in 3 species (P. minimus; P. tooheyi. n. sp.; P. cuspigerus). representing a single lineage ranging from the Orellan to Arikareean. The existence of three skulls, one with associated mandibles, allows …

Variations Of Teleconnection Of Enso And Interannual Variation In Summer Rainfall In The Central United States, Q. Steven Hu, Yongjun Zheng

Department of Earth and Atmospheric Sciences: Faculty Publications

Summer rainfall in the central United States has singular interannual variations of a 3–6-yr period. Identifying the causes of these variations assures improvement in predictions of summer rainfall in the region.

A review of previous studies revealed a puzzling situation: the outstanding interannual variations of the summer rainfall in the central United States showed no persistent correlations with known influential interannual variations in the Northern Hemisphere and the El Nin ̃o–Southern Oscillation (ENSO). This study was undertaken to identify the cause of this situation and ultimately explain the causes of the observed interannual summer rainfall variations. Its results showed a …

Laser-Derived Particle Size Data From Crp-3, Victoria Land Basin, Antarctica: Implications For Sequence And Seismic Stratigraphy, Christopher R. Fielding, G. B. Dunbar, S. M. Bryce

Department of Earth and Atmospheric Sciences: Faculty Publications

Seven hundred and nineteen samples from throughout the Cainozoic section in CRP-3 were analysed by a Malvern Mastersizer laser particle analyser, in order to derive a stratigraphic distribution of grain-size parameters downhole. Entropy analysis of these data (using the method of Woolfe & Michibayashi, 1995) allowed recognition of four groups of samples, each group characterised by a distinctive grain-size distribution. Group 1, which shows a multi-modal distribution, corresponds to mudrocks, interbedded mudrock/sandstone facies, muddy sandstones and diamictites. Group 2, with a sand-grade mode but showing wide dispersion of particle size, corresponds to muddy sandstones, a few cleaner sandstones and some …

Chronostratigraphy Of The Crp-3 Drillhole, Victoria Land Basin, Antarctica, M J. Hannah, F Florindo, David M. Harwood, Christopher R. Fielding, Cape Roberts Science Team

Department of Earth and Atmospheric Sciences: Faculty Publications

An 823 m thick glaciomarine Cenozoic section sitting unconformably on the Lower Devonian Beacon Supergroup was recovered in CRP –3. This paper reviews the chronostratigraphical constraints for the Cenozoic section. Between 3 and 480.27 mbsf 23 unconformity bounded cycles of sediment were recorded. Each unconformity is thought to represent a hiatus of uncertain duration. Four magnetozones have been recognised from the Cenozoic section. The record is complex with several “tiny wiggles” recorded throughout. Biostratigraphical or Sr ages, which could be used to link these magnetozones to the magnetic polarity time scale are restricted to the upper 190 m of sediment. …

Chronostratigraphy Of The Crp-3 Drillhole, Victoria Land Basin, Antarctica, M. J. Hannah, F. Florindo, David M. Harwood, Christopher R. Fielding, Cape Roberts Science Team

Department of Earth and Atmospheric Sciences: Faculty Publications

An 823 m thick glaciomarine Cenozoic section sitting unconformably on the Lower Devonian Beacon Supergroup was recovered in CRP –3. This paper reviews the chronostratigraphical constraints for the Cenozoic section. Between 3 and 480.27 mbsf 23 unconformity bounded cycles of sediment were recorded. Each unconformity is thought to represent a hiatus of uncertain duration. Four magnetozones have been recognised from the Cenozoic section. The record is complex with several “tiny wiggles” recorded throughout. Biostratigraphical or Sr ages, which could be used to link these magnetozones to the magnetic polarity time scale are restricted to the upper 190 m of sediment. …

Sedimentary Cyclicity In Crp Drillcore, Victoria Land Basin, Antarctica, T. R. Naish, P. J. Barrett, G. B. Dunbar, K. J. Woolfe, A. G. Dunn, S. A. Henrys, M. Claps, R. D. Powell, Christopher R. Fielding

Department of Earth and Atmospheric Sciences: Faculty Publications

The upper 1200 m of pre-Pliocene sediment recovered by Cape Roberts Project (CRP) drilling off the Victoria Land coast of Antarctica between 1997-1999 has been subdivided into 54 unconformity-bound stratigraphic sequences, spanning the period c. 32 to 17 Ma. The sequences are recognised on the basis of the cyclical vertical stacking of their constituent lithofacies, which are enclosed by erosion surfaces produced during the grounding of the advancing ice margin onto the sea floor. Each sequence represents deposition in a range of offshore shelf to coastal glacimarine sedimentary environments during oscillations in the ice margin across the Western Ross Sea …

Early Oligocene Siliceous Microfossil Biostratigraphy Of Cape Roberts Project Core Crp-3, Victoria Land Basin, Antarctica, David M. Harwood, S. M. Bohaty

Department of Earth and Atmospheric Sciences: Faculty Publications

Early Oligocene siliceous microfossils were recovered in the upper c. 193 m of the CRP-3 drillcore. Although abundance and preservation are highly variable through this section, approximately 130 siliceous microfossil taxa were identified, including diatoms, silicoflagellates, ebridians, chrysophycean cysts, and endoskeletal dinoflagellates. Well-preserved and abundant assemblages characterize samples in the upper c. 70 m and indicate deposition in a coastal setting with water depths between 50 and 200 m. Abundance fluctuations over narrow intervals in the upper c. 70 mbsf are interpreted to reflect environmental changes that were either conducive or deleterious to growth and preservation of siliceous microfossils. Only …

Basicranial Anatomy Of The Living Linsangs Prionodon And Poiana (Mammalia, Carnivora, Viverridae), With Comments On The Early Evolution Of Aeluroid Carnivorans, Robert M. Hunt Jr.

Department of Earth and Atmospheric Sciences: Faculty Publications

The living Asian linsang, Prionodon pardicolor, shares marked anatomical similarities in basicranium and dentition with the extinct Oligocene aeluroid, Palaeoprionodon lamandini, from the Quercy fissures, France. The living African linsang, Poiana richardsoni, is similar yet slightly more derived in basicranial traits relative to Prionodon pardicolor, and also has basicranial and dental features indicating a relationship to the living genets (Genetta). The basicranial and auditory anatomy of a series Palaeoprionodon-Prionodon-Poiana can be interpreted as a morphocline showing the progressive alteration of the form of the petrosal and auditory bulla from the plesiomorphic aeluroid state in …