Plio-Pleistocene Glacial Deposits in Northeastern Nebraska: New Exposures and Interpretations

A field trip sponsored by the Nebraska Geological Society. Trip Leaders: Dr. M.R. Voorhies, University of Nebraska State Museum. & Dr. R.G. Goodwin, HWS Technologies Inc. Spring 1989 Recent interpretation of oxygen isotopic data for benthic and planktonic foraminifera recovered during ocean drilling programs suggest that world ice volume was greater than the ice volume of 18 thousand years ago (Late Wisconsinan) approximately 2.5 million years ago (Prentice and Matthews, Geology, November, 1988). This agrees well With biostratigraphic and paleoecologic interepretations drawn from sediment cores obtained from the Arctic Ocean Basin. The latter data suggest complete ice cover of the basin during the period 2.2-2.4 million years ago (Scott et at., G.S.A. Bulletin, February, 1989). John Boollstorff inferred that one or more glacial tills of the North American mid-continent were deposited at this time. BoeUstorff drew his conclusions primarily from subsurface samples and from volcanic ash horizons dated by the fisssion-track method. The purpose of this trip is to examine fossil-bearing outcrops of sand and gravel or silt that are associated With volcanic ash or glacial till and that provide information about the timing of glacier advance into northeastern Nebraska. The trip Will begin at the Knox County Court House, Center, Nebraska at noon on saturday May 6, 1989. Participants are responsible for providing their own transportation

PLIO-PLEISTOCENE GLACIAL DEPOSITS IN NORTHEASTERN NEBRASKA: NEW EXPOSURES AND INTERPRETATIONS

Recent interpretation of oxygen isotopic data for benthic and planktonic foraminifera recovered during ocean drilling programs suggest that world ice volume was greater than the ice volume of 18 thousand years ago (Late Wisconsinan) approximately 2.5 million years ago (Prentice and Matthews, Geology, November, 1988). This agrees well With biostratigraphic and paleoecologic interepretations drawn from sediment cores obtained from the Arctic Ocean Basin. The latter data suggest complete ice cover of the basin during the period 2.2-2.4 million years ago (Scott et at., G.S.A. Bulletin, February, 1989)

Plio-Pleistocene Glacial Deposits in Northeastern Nebraska: New Exposures and Interpretations

A field trip sponsored by the Nebraska Geological Society. Trip Leaders: Dr. M.R. Voorhies, University of Nebraska State Museum. & Dr. R.G. Goodwin, HWS Technologies Inc. Spring 1989 Recent interpretation of oxygen isotopic data for benthic and planktonic foraminifera recovered during ocean drilling programs suggest that world ice volume was greater than the ice volume of 18 thousand years ago (Late Wisconsinan) approximately 2.5 million years ago (Prentice and Matthews, Geology, November, 1988). This agrees well With biostratigraphic and paleoecologic interepretations drawn from sediment cores obtained from the Arctic Ocean Basin. The latter data suggest complete ice cover of the basin during the period 2.2-2.4 million years ago (Scott et at., G.S.A. Bulletin, February, 1989). John Boollstorff inferred that one or more glacial tills of the North American mid-continent were deposited at this time. BoeUstorff drew his conclusions primarily from subsurface samples and from volcanic ash horizons dated by the fisssion-track method. The purpose of this trip is to examine fossil-bearing outcrops of sand and gravel or silt that are associated With volcanic ash or glacial till and that provide information about the timing of glacier advance into northeastern Nebraska. The trip Will begin at the Knox County Court House, Center, Nebraska at noon on saturday May 6, 1989. Participants are responsible for providing their own transportation

Pamphlet to Accompany Geologic Map GMC-34: Geologic Map of the O’Neill 1º x 2º Quadrangle, Nebraska, with Configuration Maps of Surfaces of Formations

This map is necessarily generalized. It is based primarily on data from 7.5’ surficial geologic quadrangle maps of the map area prepared by the authors principally from 1991 to 2000, from Voorhies (unpub. data, 1974), as well as data from test-hole drilling done across the quadrangle by the Conservation and Survey Division, University of Nebraska, and its cooperators over many years since the 1930s. For more detailed information, consult the geologic data files of the Conservation and Survey Division, School of Natural Resources, University of Nebraska-Lincoln. The quadrangle is mostly covered by vegetation and Holocene sediments. Limited good exposures of older sediments and bedrock occur usually in road cuts, in quarry and pit excavations, on valley sides, on stream and river cut banks, and in isolated erosional remnants on uplands. Users of this map should remember that the scale of the map is small and allows only a general picture of the geology of the quadrangle to be depicted. Users should check with the authors regarding specific sites and, if necessary, do field checks of these sites. As new data become available the authors intend to update the data sets used in preparation of this quadrangle text and maps and to issue refined versions, if necessary. The earliest geologic map that included part of the study area was published by Charles Lyell in 1845 (Diffendal, 1993). Other geologic maps at different scales that include all or parts of the map area are by Darton (1899, 1905), Condra (1908), Schulte (1952), Mendenhall (1953), Lampshire (1956), Burchett (1986), Weeks and Gutentag, (1981), Weeks and others (1988), Swinehart and others (1994), and Diffendal and Voorhies (1994). Geologic maps of adjacent areas in Nebraska and South Dakota include Burchett and others (1975), Burchett and others (1988), Diffendal (1991), and Souders (2000) for Nebraska and Stevenson and Carlson (1950, 1951), Baker and others (1952), Collins and French (1958), Schoon and Sevon (1958), Stevenson and others (1958), and Stevenson and others (1959) for parts of South Dakota. Detailed groundwater investigations and associated stratigraphic test drilling (of parts or all of the map area) were done by Darton (1905), Condra (1908), Reed (1944), Keech and Schreurs (1953, 1954), Cronin and Newport (1956), Reed (1957), Smith (1958), Newport (1959), Souders and Shaffer (1969), Souders (1976), Gutentag and Weeks (1980), Luckey and others (1981), Lawton and Hiergesell (1988), Weeks and others (1988), Pierce (1989), Rahn and David (1989), Burchett and Smith (1992), and Lackey and others (1995, 1998a, 1998b, 2000)

Bayesian Surprise in Indoor Environments

This paper proposes a novel method to identify unexpected structures in 2D floor plans using the concept of Bayesian Surprise. Taking into account that a person's expectation is an important aspect of the perception of space, we exploit the theory of Bayesian Surprise to robustly model expectation and thus surprise in the context of building structures. We use Isovist Analysis, which is a popular space syntax technique, to turn qualitative object attributes into quantitative environmental information. Since isovists are location-specific patterns of visibility, a sequence of isovists describes the spatial perception during a movement along multiple points in space. We then use Bayesian Surprise in a feature space consisting of these isovist readings. To demonstrate the suitability of our approach, we take "snapshots" of an agent's local environment to provide a short list of images that characterize a traversed trajectory through a 2D indoor environment. Those fingerprints represent surprising regions of a tour, characterize the traversed map and enable indoor LBS to focus more on important regions. Given this idea, we propose to use "surprise" as a new dimension of context in indoor location-based services (LBS). Agents of LBS, such as mobile robots or non-player characters in computer games, may use the context surprise to focus more on important regions of a map for a better use or understanding of the floor plan.Comment: 10 pages, 16 figure

Ashfall Tephra in the Ogallala Group of the Great Plains: Characteristics and Significance

The Miocene Ogallala Group blankets the Great Plains east of the Rocky Mountains. This sheet of largely fluvial deposits, lying downwind of major silicic volcanic fields to the west, was ideally located to receive and preserve tephra from these fields. This investigation brings modern methods of tephrochronlogy to bear on the age and identity of Ogallala tephra. Results indicate that ~40 separate tephra layers, ranging in age from ~16.5–5.0 Ma, in the Ogallala. Most tephra came from Yellowstone hotspot sources. The relative frequency of hotspot tephra in the Ogallala matches that in more proximal regions to the west with peak intensities in the intervals ~16.5−15 Ma nd ~13.0−8.5 Ma. About 30 of the Ogallala tephra are correlated with tephra of known age the the Basin and Range to the west. Using the ages of correlative tephra to the west insight into the age of the Ogallala, the correlation of Ogallala tephra from region to region in the Great Plains, and sedimentation rates within the Ogallala. In the Ogallala sedimentation rates vary. The rates are lowest (3–9 m/Ma) in the Cap Rock Mbr. of the Ash Hollow Fm. along the Niobrara River and in undifferentiated Ogallala strata and in the undifferentiated Ogalala Gp. in NW Kansas. Rates of 40–80 m/Ma characterize the Valentine Fm. beneath the Cap Rock Mbr. Finally, one tephra, the 11.37 Ma Cougar Point Tuff XI, is recognized at 6 localies. This key horizon provides the first detailed structure contours within the Ogallala. These contours show a sharply increasing slope of the Ogallala west of 101° W that reflects the post–6 Ma tilt along the western edge of the Ogallala. East of 101º W the gradients mirror the gradients of the major rivers (1.3 to 1.6 m/km.). West of 101º W gradients increase and reach a maximun of 4.6 m/km at the crest of the Gangplank

Ashfall Tephra in the Ogallala Group of the Great Plains: Characteristics and Significance

The Miocene Ogallala Group blankets the Great Plains east of the Rocky Mountains. This sheet of largely fluvial deposits, lying downwind of major silicic volcanic fields to the west, was ideally located to receive and preserve tephra from these fields. This investigation brings modern methods of tephrochronlogy to bear on the age and identity of Ogallala tephra. Results indicate that ~40 separate tephra layers, ranging in age from ~16.5–5.0 Ma, in the Ogallala. Most tephra came from Yellowstone hotspot sources. The relative frequency of hotspot tephra in the Ogallala matches that in more proximal regions to the west with peak intensities in the intervals ~16.5−15 Ma nd ~13.0−8.5 Ma. About 30 of the Ogallala tephra are correlated with tephra of known age the the Basin and Range to the west. Using the ages of correlative tephra to the west insight into the age of the Ogallala, the correlation of Ogallala tephra from region to region in the Great Plains, and sedimentation rates within the Ogallala. In the Ogallala sedimentation rates vary. The rates are lowest (3–9 m/Ma) in the Cap Rock Mbr. of the Ash Hollow Fm. along the Niobrara River and in undifferentiated Ogallala strata and in the undifferentiated Ogalala Gp. in NW Kansas. Rates of 40–80 m/Ma characterize the Valentine Fm. beneath the Cap Rock Mbr. Finally, one tephra, the 11.37 Ma Cougar Point Tuff XI, is recognized at 6 localies. This key horizon provides the first detailed structure contours within the Ogallala. These contours show a sharply increasing slope of the Ogallala west of 101° W that reflects the post–6 Ma tilt along the western edge of the Ogallala. East of 101º W the gradients mirror the gradients of the major rivers (1.3 to 1.6 m/km.). West of 101º W gradients increase and reach a maximun of 4.6 m/km at the crest of the Gangplank