Earth Sciences Commons^™

Ice-Wedge Casts Of Wisconsinan Age In Eastern Nebraska, William J. Wayne

Department of Earth and Atmospheric Sciences: Faculty Publications

Sand-filled, wedge-shaped structures beneath a thin layer of aeolian sand penetrate a preIllinoian till and gravel in northeastern Nebraska. Interpreted to be relic thermal contraction crack wedges, they provide the first definite evidence in this State of the former presence of permafrost. The wedges are 5- 7 m apart, 1.8-2.8 m deep and 0.6-0.9 m across at the top, taper downward to a crack and intersect to form polygons. They are filled with medium sand that contains mostly rounded and frosted grains. Vertical fabric is present in each wedge. Ventifacts lie along the top of the till, which is covered …

Recent Secular Variations In The Extent Of Northern Hemisphere Snow Cover, David A. Robinson, Kenneth F. Dewey

Department of Earth and Atmospheric Sciences: Faculty Publications

Northern hemisphere snow cover during 1988 and 1989 was at its lowest extent since the advent of reliable satellite snow-cover monitoring 1972; running some 8-10% below the eighteen-year annual mean of 25.7 million km² . Monthly minima for the period of record occurred six times during these two years. In general, the last nine years of the satellite record had less extensive cover than the 1972-80 interval. Negative anomalies during the 1980s were largest over Eurasia in all seasons, and in the Spring over North America. Hemispheric seasonal means for the most recent nine years were 3.7% to 8.4% …

Resultats Preliminaires De La Campagne De Forages Du Joides Resolution Sur Le Plateau De Kerguelen (Odp Leg 120)/ Preliminary Results Of Odp Leg 120 In The Central And Southern Kerguelen Plateau, Roland Schlich, Marc Munschy, Hubert Whitechurch, Marie-Pierre Aubry, Sherwood Wise Jr., Amanda Palmer, William Berggren, Peter Bitschene, Neal Blackburn, James Breza, Millard Coffin, David M. Harwood, Franz Heider, Mary Anne Holmes, William Howard, Hiroo Inokuchi, Kerry Kelts, David Lazarus, Andreas Mackenzen, Toshiaka Maruyama, Elizabeth Pratson, Patrick Quilty, Frank Rack, Vincent Salters, James Sevigny, Michael Storey, Atsushi Takemura, David Watkins, James Zachos

Department of Earth and Atmospheric Sciences: Faculty Publications

Resume - Le Leg 120 du programme international de forages oceaniques (Ocean Drilling Project) a permis de determiner la nature et l'age du plateau de Kerguelen et de decrire son evolution depuis Ie Cretace. Le socle, fore aux sites 747, 749 ct 750, est compose de coulees basaltiqucs qui correspondent a des tholeiites transitionnelles saturees en silice. Ces basaltes se sont mis en place dans des conditions aeriennes ou sub-aeriennes avant Ie Cenomanien sur une surface quasiment horizontalc. Les premiers sediments, d'age Cenomanien, se sont deposes en milieu fluviatile. Au Campanien et a la fin du Maestrichtien Ie plateau a …

Evolution Of The Aeluroid Carnivora: Significance Of The Ventral Promontorial Process Of The Petrosal, And The Origin Of Basicranial Patterns In The Living Families, Robert M. Hunt Jr.

Department of Earth and Atmospheric Sciences: Faculty Publications

In studies of carnivoran phylogeny, the configuration and ontogenetic development of the auditory bulla enclosing the middle ear have been useful in tracing modern lineages to their first appearances in the mid-Cenozoic. Pre-Oligocene carnivorans, however, lack preserved bullae and have been difficult to relate to later Cenozoic groups. The carnivoran petrosal bone, because of its durability both in intact skulls and as an isolated element, can be tracked through Cenozoic time, and can supply new information on lineage continuity through its geometry and spatial relationships. Aeluroid carnivorans are united by a petrosal of characteristic shape, distinguished by a ventral promontorial …

Early Lake Ontogeny Following Neoglacial Ice Recession At Glacier Bay, Alaska, Daniel R. Engstrom, Sherilyn C. Fritz

Department of Earth and Atmospheric Sciences: Faculty Publications

This study explores the environmental forces controlling lake ontogeny at Glacier Bay as a model for early Holocene lake evolution in north temperate lakes worldwide. Long-term chemical and biological changes in lakes are investigated with two complementary research strategies: (1) limnological conditions are compared among 32 lakes of known age and in different stages of primary catchment succession and (2) sediment cores from these same lakes are analyzed stratigraphically for fossil diatoms to ascertain developmental trends in pH, alkalinity, algal composition, and trophic status at individual sites.

Trends in water chemistry inferred from the chronosequence approach include a progressive loss …

Leg 101--An Overview, James A. Austin Jr., Wolfgang Schlager, Amanda A. Palmer, Paul A. Comet, André Droxler, Gregor Eberli, Eric Fourcade, Raymond Freeman-Lynde, Craig S. Fulthorpe, Gill Harwood, Gerhard Kuhn, Dawn Lavoie, Mark Leckie, Allan J. Melillo, Arthur Moore, Henry T. Mullins, Christian Ravenne, William W. Sager, Peter Swart, Joost W. Verbeek, David K. Watkins, Colin Williams

Department of Earth and Atmospheric Sciences: Faculty Publications

During Leg 101, the inaugural leg of the Ocean Drilling Program, the JOIDES Resolution drilled 19 holes at 11 sites in the Bahamas. Grids of high-resolution seismic profiles provided information crucial for both site selection and regional stratigraphic interpretations. The first major scientific objective was to understand the long-term evolution of the bank-and-basin pattern that currently characterizes the Bahamas archipelago. Drilling and seismic surveys have indicated considerable platform expansion and retreat rather than stationary upward growth. Upbuilding in the Late Jurassic-Early Cretaceous was followed by drowning and retreat in the mid-Cretaceous and by renewed expansion in the Cenozoic. At Site …

Calcareous Nannofossil Biostratigraphy From Leg 101, Northern Bahamas, David K. Watkins, Joost W. Verbeek

Department of Earth and Atmospheric Sciences: Faculty Publications

Leg 101 of the Ocean Drilling Program drilled 19 holes at 11 sites to investigate the geology of the Straits of Florida and the northern Bahamas. Drilling at Site 626 indicated that the Gulf Stream has had significant flow through the Straits of Florida for at least the last 24 million years. Winnowed, foraminiferal grainstones and packstones with sparse nannofossil assemblages and the reworking of older nannofossils suggest strong bottom-current activity throughout this interval. Drilling north of Little Bahama Bank and in Exuma Sound documents the growth of platform slopes during the late Cenozoic. Nannofossil biostratigraphy of the upper Cenozoic …

10. Evidence For Continuous And Discontinuous Alteration In Dsdp Hole 418a Basalts And Its Significance To Natural Gamma-Ray Log Readings, Mary Anne Holmes

Department of Earth and Atmospheric Sciences: Faculty Publications

During Ocean Drilling Program Leg 102, the Schlumberger natural gamma-ray spectrometry tool measured high potassium levels in one interval of DSDP Hole 418A basalts. Samples from that hole were examined by X-ray diffraction, SEM, and EDS analyses in order to identify mineral species responsible for the high readings. The results indicate that high K readings observed on wireline logs run in basement can be attributed to extensive low-temperature oxidative alteration resulting in formation of palagonite and K-rich clays (celadonite, potassic nontronite, and mixed-layer celadonite/ nontronite). Where these readings are accompanied by high porosity, low density, and low velocity readings, a …

Paleontological Results From Ocean Drilling Program Leg 101, David K. Watkins, Eric Fourcade, R. Mark Leckie, Allan J. Melillo, Amanda A. Palmer, Joost W. Verbeek, Jacques Butterlin, Renée Damotte, Claude Guernet, Edwige Masure, Michael J. Moran

Department of Earth and Atmospheric Sciences: Faculty Publications

Leg 101 of the Ocean Drilling Program recovered Albian through Holocene sediments from a variety of carbonate depositional environments. Data from four microplanktonic groups (calcareous nannofossils, planktonic foraminifers, radiolarians, and dinoflagellates) and four benthic groups (larger foraminifers, smaller benthic foraminifers, ostracodes, and sponge spicules) yield a biostratigraphic and paleoecologic framework for these varied sediments. Winnowed, skeletal-planktonic foraminiferal packstones and grainstones from the central Straits of Florida (Site 626) reflect a late Oligocene to Holocene history of sporadic sedimentation greatly influenced by strong bottom-current activity. Neogene to Quaternary sediments from two carbonate-slope transects (Sites 627 to 633) indicate significant slope accretion …

Pliocene-Pleistocene Variations In Aragonite Content And Planktonic Oxygen-Isotope Record In Bahamian Periplatform Ooze, Hole 633a, André W. Droxler, Christopher H. Bruce, William W. Sager, David K. Watkins

Department of Earth and Atmospheric Sciences: Faculty Publications

Hole 633A was drilled in the southern part of Exuma Sound on the toe-of-slope of the southeastern part of Great Bahama Bank during ODP Leg 101. The top 55 m, collected as a suite of six approximately 9.5-m-long hydraulic piston cores, represents a Pliocene-Pleistocene sequence of periplatform carbonate ooze, a mixture of pelagic calcite (foraminifer and coccolith tests), some pelagic aragonite (pteropod tests), and bank-derived fine aragonite and magnesian calcite. A 1.6-m.y.-long hiatus was identified at 43.75 mbsf using calcareous nannofossil biostratigraphy and magnetostratigraphy.

The 43.75-m-thick periplatform sequence above the hiatus is a complete late Pliocene-Quaternary record of the past …

Oligocene Calcareous-Nannofossil Biostratigraphy From Leg 101, Site 628, Little Bahama Bank Slope, Michael J. Moran, David K. Watkins

Department of Earth and Atmospheric Sciences: Faculty Publications

Drilling at Hole 628A, Leg 101 of the Ocean Drilling Program, recovered a thick, relatively complete Oligocene section of nannofossil-foraminifer chalk and ooze. Sediments from Cores 101-628A-16H through 101-628A-29X were examined using the light microscope to provide information about biostratigraphy of calcareous nannofossils. Several authors noted a problem in distinguishing the first appearance of species within the Sphenolithus predistentus-S. ciperoensis lineage of the mid-Oligocene, particularly Sphenolithus ciperoensis, because of the gradual evolution of its members. Successful separation of species in this lineage is critical for accurately dating relative age of mid- and upper-Oligocene nannofossil sediments. Length and taper of …

The Onset Of Spring Melt In First-Year Ice Regions Of The Arctic As Determined From Scanning Multichannel Microwave Radiometer Data For 1979 And 1980, Mark R. Anderson

Department of Earth and Atmospheric Sciences: Faculty Publications

Sea ice ablation is an important physical process affecting the global climate system. During the Arctic melt season, rapid changes occur in both sea ice surface conditions and the extent of ice. These changes alter the albedo and vary the surface energy budget. Understanding variations in Arctic sea ice is critical for global climate studies. This paper investigates the spring onset of melt in the Arctic seasonal sea ice zone through analysis of melt signatures derived from Nimbus 7 scanning multichannel microwave radiometer data. Satellite-derived melt signatures, determined by 18- and 37-GHz vertical brightness temperatures, are associated with the initial …

Snow Melt On Sea Ice Surfaces As Determined From Passive Microwave Satellite Data, Mark R. Anderson

Department of Earth and Atmospheric Sciences: Faculty Publications

SMMR data for the year 1979, 1980 and 1984 have been analyzed to determine the variability in the onset of melt for the Arctic seasonal sea ice zone. The results show melt commencing in either the Kara/Barents Seas or Chukchi Sea and progressing zonally towards the central Asian coast (Laptev Sea). Individual regions had interannual variations in melt onset in the 10-20 day range. To determine whether daily changes occur in the sea ice surface melt, the SMMR 18 and 37 GHz brightness temperature data are analyzed at day/night/twilight periods. Brightness temperatures illustrate diurnal variations in most regions during melt. …

45. Clay Mineralogy Of The Lower Cretaceous Deep-Sea Fan, Deep Sea Drilling Project Site 603, Lower Continental Rise Off North Carolina, Mary Anne Holmes

Department of Earth and Atmospheric Sciences: Faculty Publications

The clay mineralogy of Lower Cretaceous deep-sea fan sediment in the western North Atlantic is dominated by smectite in most intervals, and by illite in samples from intervals of high sand input. Different intervals of high sand input are enriched in kaolinite. Kaolinite and illite levels do not correlate in this sediment, indicating that the input of each clay type was independent and represents either a different provenance or a different depositional mode. The latter hypothesis is preferred because equivalent, continental strata have clay mineral suites dominated in most cases by kaolinite, and in other cases by illite. Only marine …

Evolution Of The Aeluroid Camivora: Significance Of Auditory Structure In The Nimravid Cat Dinictis, Robert M. Hunt Jr.

Department of Earth and Atmospheric Sciences: Faculty Publications

Evolutionary lineages among living and extinct Carnivora can be identified by a diagnostic pattern of ontogenetic elements forming the auditory bulla enclosing the middle ear, best observed in newborn and juvenile animals. However, in the fossil record, the delicate unfused bulla parts of very young carnivorans are rarely preserved. Thus bulla composition in extinct lineages is difficult to determine unless juveniles with well-preserved auditory bullae can be found. Discovery in 1981 of an intact cranium of a juvenile aeluroid carnivoran (Dinictis) from the White River Group (Oligocene) in northwestern Nebraska has resulted in an improved understanding of bulla …

34. Provenance And Deposition Of Lower Cretaceous Turbidite Sands At Deep Sea Drilling Project Site 603, Lower Continental Rise Off North Carolina, Mary Anne Holmes, James Breza, Sherwood Wise

Department of Earth and Atmospheric Sciences: Faculty Publications

During the drilling of Hole 603B on Deep Sea Drilling Project Leg 93, an unexpected series of sand-, silt-, and claystone turbidites was encountered from Cores 603B-45 through -76 (1224-1512 m sub-bottom depth). Complete and truncated Bouma sequences were observed, some indicating deposition by debris flows. Sand emplacement culminated with the deposition of a 30-m-thick, unconsolidated sand unit (Cores 603B-48 through -45).
The purpose of this preliminary study is to determine the nature of the heavy mineral suites of this sediment in order to make tentative correlations with onshore equivalents. The heavy mineralogy of Lower Cretaceous North American mid-Atlantic coastal …

Analysis And Interpretation Of Ice-Deformed Sediments From Harrison Bay, Alaska, Steven A. Fischbein

Department of Earth and Atmospheric Sciences: Faculty Publications

The surficial sediments present on the continental shelf off the north coast of Alaska in the vicinity of Harrison Bay consist dominantly of fine grained sand, silt, and mud that were deposited during Holocene time. Depositional environments in Harrison Bay range from outer shelf to prodelta and delta front. Ice sediment interaction has overprinted structural deformation on many of the sediments present in Harrison Bay, and has in some cases obliterated the original lithologic continuity of the sediments. Ice related deformation ranges from simple loading features to more complex folded and faulted structures. A hypothetical model has been proposed which …

Identification And Analysis Of Climatic Fields Through Dot-Density Shading, Stephen J. Lavin, Randall S. Cerveny

Department of Earth and Atmospheric Sciences: Faculty Publications

Gridded matrices of climatic data can be mapped by computer with a variety of symbolization methods, all of which have some shortcomings. A new mapping procedure, dot-density shading, is herein proposed as an alternative mapping form. Dot-density shading produces continuous-appearing dot patterns whose density is proportional to the data. Significant algorithms are those for computing dot numerosity and quasi-random dot placement. A number of application including data error detection and anomaly recognition are discussed.

A Possible Mechanism For The Diurnal Oscillations Of Tropical Cyclones, Jay S. Hobgood

Department of Earth and Atmospheric Sciences: Faculty Publications

A possible mechanism for the diurnal oscillations of tropical cyclones is presented. In the conceptual model developed to explain these features, the diurnal cycle of net radiation at the cloud tops is identified as the primary cause of the oscillations. Radiative cooling of the cloud tops at night steepens the lapse rate and increases convection. This generates a slight intensification in the storm. The reverse occurs during the daytime as the cloud tops absorb solar radiation. This process may be augmented by differential cooling of cloudy and clear areas.

This conceptual model is tested through the use of a numerical …

Seasonal Temperature Forecasts As Products Of Antecedent Linear And Spatial Temperature Arrays, Merlin Lawson, Randall S. Cerveny

Department of Earth and Atmospheric Sciences: Faculty Publications

Our objective is to evaluate the potential for extracting the maximum information contained in antecedent temperature patterns that operationally could be used in formulating winter seasonal forecasts in the United States. In particular, examination of the predictability of winter temperatures given autumn temperatures is made using derived contingency tables, discriminant equations of antecedent principal components, and canonical correlation analysis.

Contingency tables were constructed based on tercile classifications of a seventy-five-year dependent record (1895-1969). Testing of an independent data period (1970-78) using these tables produced winter forecasts with no appreciable skill in the aggregate (-0.04). Discriminant analysis derived linear combinations of …

Drainage Patterns And Glaciations In Eastern Nebraska, William J. Wayne

Department of Earth and Atmospheric Sciences: Faculty Publications

Most of the stream courses of eastern Nebraska came into existence during the recession of an ice margin. Their patterns include many drainage anomalies that suggest both the manner and the times of ice disappearance. Rivers coming from the west flow down the regional slope of the High Plains. Along and east of the "Kansan" glacial border most streams are subparallel, trend S300 _40 0 E, and probablY mark pauses of an actively retreating ice margin. Logan Creek, an underfit stream, flows S4SoE from Hartington to the Thurston/Burt c<;mnty line, then directly southward to the Elkhorn. East of Logan Creek and above the bend, South Blackbird, Omaha, and Cow creeks flow parallel to Logal Creek then bend abruptly back northward to the Missouri. The Bow creeks in Cedar and Knox counties describe a series of arcs that surely mark successive retreatal positions of an ice lobe that crossed the Missouri trench around Yankton, South Dakota. Bazile Creek in the Santee Sioux Reservation flows northward to the Missouri, but the gravel and sand along it indicate a southeastward flow for the currents that deposited them. These sediments can be traced into the North Fork of the Elkhorn, thence to the Platte Valley near Fremont. These drainage lines define the lobate margins of the ice through the J ames and Red River lowlands. The degree of dissection and alteration of the associated tills suggests the relative lengths of time since the ice melted from them. The compact and weathered tills in east-central Nebraska are oldest (classical Kansan); the softer, less weathered tills near the Missouri are younger (Illinoian?); Wisconsinan ice may have blocked the Missouri River near Yankton and shunted it to the Elkhorn, but left little till on the south side of the Missouri.

Cretaceous Calcareous Nannofossils From Deep Sea Drilling Project Leg 77, Southeast Gulf Of Mexico, David K. Watkins, Jay L. Bowdler

Department of Earth and Atmospheric Sciences: Faculty Publications

Five of the six sites drilled during Leg 77 of the Deep Sea Drilling Project yielded Cretaceous sediments. Two of these sites, 535 and 540, form a composite section that spans the upper Berriasian through most of the Cenomanian. Olive black marly limestones in this interval yield relatively rich, well-preserved nannofossil assemblages that allow biostratigraphic subdivision of the sequence. This composite section provides important information on the Early Cretaceous history of the Gulf of Mexico, as well as additional information on tropical Lower Cretaceous nannofossil assemblages. The post-Cenomanian nannofossil (and sedimentary) record is limited to a thin, condensed section of …

Cenozoic Calcareous Nannofossils From Deep Sea Drilling Project Leg 77: Biostratigraphy And Delineation Of Hiatuses, Thomas H. Lang, David K. Watkins

Department of Earth and Atmospheric Sciences: Faculty Publications

Three of the six Deep Sea Drilling Project (DSDP) Leg 77 sites drilled in the western approaches to the Straits of Florida yielded thick sequences of Cenozoic sediment rich in calcareous nannofossils. Hiatuses are prominent in each of these continuously cored intervals. A prominent upper Oligocene hiatus, observed at each of these three sites, can be correlated to a large-scale "global" regression event. Other disconformable horizons present in the study area cannot be positively related to sealevel fluctuations and may be caused by a number of factors including local tectonic activity. Paleogene sections are generally marked by thick accumulations within …

Miocene Burrows Of Extinct Bear Dogs: Indication Of Early Denning Behavior Of Large Mammalian Carnivores, Robert M. Hunt Jr., Xue Xiang-Xu, Joshua Kaufman

Department of Earth and Atmospheric Sciences: Faculty Publications

Partial skeletons of four species of extinct carnivores have been found in their dens excavated in the floodplain of an early Miocene ephemeral braided stream at Agate Fossil Beds National Monument, Nebraska. Bear dogs (Carnivora: Amphicyonidae) were the principal occupants; their den dimensions and body size are similar to those of living wolves and hyenas. Discovery of this predator community extends the record of denning behavior of large mammalian carnivores to the early Miocene, 20 million years ago.

Relative Dating Techniques To Distinguish Late Pleistocene-Holocene Continental Sediments, William J. Wayne

Department of Earth and Atmospheric Sciences: Faculty Publications

Radiometric dating, particularly with ¹⁴C, provides ages for those Late Pleistocene and Holocene sediments that contain datable materials. Standard stratigraphic and morphostratigraphic techniques of superposition, geomorphic position, partial overlap, and offlap provide relative chronology in many situations. The use of multiple relative dating (RD) techniques, developed for the study of glacial deposits, makes use of these techniques where possible, but depends heavily on the additional comparison of the results of surface processes that act continuously and more or less uniformly after accumulation is complete. For sediments at the surface that have not been buried, the most important of …

Glacial Chronology Of The Ruby Mountains–East Humboldt Range, Nevada, William J. Wayne

Department of Earth and Atmospheric Sciences: Faculty Publications

The Ruby Mountains-East Humboldt Range, one of the interior mountain groups of the Basin and Range Province, lies about midway between the Wasatch Mountains and the Sierra Nevada. After Blackwelder’s description in his review of glaciation in the western mountains, Sharp mapped and named the deposits of the Lamoille and Angel Lake glaciations and correlated them with early and late Wisconsin deposits of the Great Lakes area. The refinement of relative dating (RD) methods, the availability of air photos and modem topographic maps, and new road cuts have aided the restudy of these alpine glacial deposits and the basis for …

Paleontological Synthesis, Leg 77, David K. Watkins, Charles L. Mcnulty

Department of Earth and Atmospheric Sciences: Faculty Publications

Biostratigraphic age assignment and paleoecological analysis of the sedimentary material recovered on Deep Sea Drilling Project Leg 77 provide a temporal and paleoenvironmental framework for the reconstruction of the Cretaceous and Cenozoic geologic history of the deep southeastern Gulf of Mexico. Planktonic foraminiferal and calcareous nannofossil biostratigraphy, in conjunction with sedimentologic evidence, indicates the sporadic nature of sedimentation during the Türonian through Holocene throughout the study area. This trend is especially well developed within the Upper Cretaceous, which is largely represented only by a thin, condensed section at a single site. The Cenozoic is somewhat better represented, although the thin, …

Multiple Glaciations Of The Cordon Del Plata, Mendoza, Argentina [Glaciaciones Multiples Del Cordon Del Plata, Mendoza, Argentina], William J. Wayne, Arturo E. Corte

Department of Earth and Atmospheric Sciences: Faculty Publications

Evidence exists for four glaciations in the Río Blanco basin west of Mendoza, Argentina. Morphology, superposition of tills, soil-profile development, loess thickness, and boulder weathering have been the techniques most useful in mapping the tills. Glaciers of Vallecitos (= Wisconsinan) age extended to 2600 m and left distinctive moraines. Tills of two preVallecitos glacier advances cover the floor of the valley from 2600 m to below 2100 m, and remnants of one of the tills extend nearly to the junction with Río Mendoza (1400 m) 13 km below the lowest Vallecitos moraines. These deposits were considered to be mudflows rather …

Jurassic Calcareous Nannofossil Zonation And Overview With New Evidence From Deep Sea Drilling Project Site 534, Peter H. Roth, Alan W. Medd, David K. Watkins

Department of Earth and Atmospheric Sciences: Faculty Publications

A zonation is presented for the oceanic late Middle Jurassic to Late Jurassic of the Atlantic Ocean. The oldest zone, the Stephenolithion bigotii Zone (subdivided into a Stephanolithion hexum Subzone and a Cyclagelosphaera margerelii Subzone), is middle Callovian to early Oxfordian. The Vagalapilla stradneri Zone is middle Oxfordian to Kimmeridgian. The Conusphaera mexicana Zone, subdivided into a lower Hexapodorhabdus cuvillieri Subzone and a Polycostella beckmannii Subzone, is the latest Kimmeridgian to Tithonian. Direct correlation of this zonation with the boreal zonation established for Britain and northern France (Barnard and Hay, 1974; Medd, 1982; Hamilton, 1982) is difficult because of poor …

Miocene Burrows Of Extinct Bear Dogs: Indication Of Early Denning Behavior Of Large Mammalian Carnivores, Robert M. Hunt Jr., Xue Xiang-Xu, Joshua Kaufman

Department of Earth and Atmospheric Sciences: Faculty Publications

Partial skeletons off our species of extinct carnivores have been found in their dens excavated in the floodplain of an early Miocene ephemeral braided stream at Agate Fossil Beds National Monument, Nebraska. Bear dogs (Carnivora: Amphicyonidae) were the principal occupants; their den dimensions and body size are similar to those of living wolves and hyenas. Discovery of this predator community extends the record of denning behavior of large mammalian carnivores to the early Miocene, 20 million years ago.