Geologic map showing configuration of the bedrock surface, North Platte, 1 degree x 2 degrees quadrangle, Nebraska

The map area, in west-central Nebraska, is largely covered by surficial deposits of eolian sand, loess, and alluvium ranging in age from Holocene to Pliocene. Holocene and late Pleistocene(?) eolian sand, as much as 300 ft (91 m) thick, covers most of the area north of the North Platte and Platte Rivers, and also covers a small area south of those rivers. The Peoria Loess of Quaternary age overlies most of the remaining upland north of the Platte River in southwestern Logan, northeastern Lincoln, and much of western Custer and extreme northwestern Dawson Counties. Loess also mantles the divide between the North and South Platte Rivers and most of the upland south of the South Platte River in Keith, Lincoln, and Perkins Counties. Holocene alluvium underlies the valleys of the rivers and their larger tributaries. Older alluvium of Pleistocene and Pliocene age occurs beneath loess on the divide between the North and South Platte Rivers, beneath eolian sand along the north side of the North Platte River valley, and along the Dismal and Middle Loup Rivers. Rocks of the Miocene Ogallala Group crop out principally along the south side of the North Platte River valley and on either side of the South Platte River, and locally in roadcuts and along other stream valleys. The Ogallala is present beneath the surficial deposits throughout the quadrangle except in two local areas (fig. 1). The Arikaree Group (Miocene and Oligocene) underlies the Ogallala over much of western Nebraska but no outcrops were recognized in the quadrangle. However, Arikaree deposits have been recognized in drill holes near the Grant County-Arthur County line in the northwestern part of the map area. The Oligocene Brule Formation of the White River Group unconformably underlies the Ogallala Group in outcrops in the quadrangle. Exposures of the Brule are confined to tributary streams along the south side of the North Platte River from Kingsley Dam eastward for about 2 mi (1.2 km). The Brule in the quadrangle conforms to the expanded definition of the formation in western Nebraska by Swinehart and others (1985). Data on the depth to bedrock and the thickness of the Ogallala Group are from logs of drill holes and irrigation wells in the data collections of the Conservation and Survey Division, University of Nebraska-Lincoln. Additional geologic data were derived from maps and reports listed in the Selected References and from the unpublished soil survey of Keith County (S.A. Scheinost, unpub. data, 1991). J.B. Swinehart, research geologist, Nebraska Geological Survey, collaborated with the author in preparation of the bedrock contour map. North Latitude: 42° 0\u27 0 N (42.0000) South Latitude: 41° 0\u27 0 N (41.0000) East Longitude: 100° 0\u27 0 W (-100.0000) West Longitude: 102° 0\u27 0 W (-102.0000

Brule NW Quadrangle, Keith County, Nebraska

7.5\u27 topgraphic quadrangle showing exposures of bedrock formations and other geologic information. 41° 07\u2730 — 41° 15\u27 101° 52\u2730 — 102° 00\u27 Scale 1:24,000 Completed 14 August 197

Broadwater [SE] Quadrangle, Morrill County, Nebraska

7.5\u27 topgraphic quadrangle showing exposures of bedrock formations and other geologic information. 41° 30\u27 — 41° 37\u2730 102° 45\u27 — 102° 52\u2730 Scale 1:24,000 Completed [n.d.

Overview of Nebraska and the Regional Aquifer from Proceedings of the 1985 Water Resources Seminar Series

During each spring semester, the Nebraska Water Resources Center sponsors a Water Resources Seminar Series at the University of Nebraska - Lincoln. The 1985 seminar series was entitled Aspects of Groundwater Quality . This article appeared in the proceedings

Brule SE Quadrangle, Keith & Perkins Counties, Nebraska

7.5\u27 topgraphic quadrangle showing exposures of bedrock formations and other geologic information. 41° 00\u27 — 41° 07\u2730 101° 45\u27 — 101° 52\u2730 Scale 1:24,00

Ecoregions of Nebraska and Kansas

Ecoregions denote areas of general similarity in ecosystems and in the type, quality, and quantity of environmental resources; they are designed to serve as a spatial framework for the research, assessment, management, and monitoring of ecosystems and ecosystem components. Ecoregions are directly applicable to the immediate needs of state agencies, including the development of biological criteria and water quality standards, and the establishment of management goals for nonpoint-source pollution. They are also relevant to integrated ecosystem management, an ultimate goal of most federal and state resource management agencies. The approach used to compile this map is based on the premise that ecological regions can be identified through the analysis of the patterns of biotic and abiotic phenomena that reflect differences in ecosystem quality and integrity (Wiken, 1986; Omernik, 1987, 1995). These phenomena include geology, physiography, vegetation, climate, soils, land use, wildlife, and hydrology. The relative importance of each characteristic varies from one ecological region to another regardless of the hierarchical level. A Roman numeral hierarchical scheme has been adopted for different levels of ecological regions. Level I and level II divide the North American continent into 15 and 52 regions, respectively (Commission for Environmental Cooperation Working Group 1997). At level III, the continental United States contains 104 regions (United States Environmental Protection Agency [US EPA], 2000). However, depending on the objectives of a particular project, ecoregions may be aggregated within levels of the hierarchy for data analysis and interpretation. Explanations of the methods used to define the US EPA’s ecoregions are given in Omernik (1995), Griffith and others (1994), and Gallant and others (1989). Albers equal area projection; Standard parallels 38° N and 42° N PRINCIPAL AUTHORS: Shannen S. Chapman (Dynamac Corporation), James M. Omernik (US EPA), Jerry A. Freeouf (USFS), Donald G. Huggins (KBS), James R. McCauley (KGS), Craig C. Freeman (KBS), Gerry Steinauer (NGPC), Robert T. Angelo (KDHE), and Richard L. Schlepp (USDA, NRCS). COLLABORATORS AND CONTRIBUTORS: Steven R. Walker (NDEQ), Kenneth R. Bazata (NDEQ), Sharon W. Waltman (USDA, NRCS-National Soil Survey Center [NSSC]), William J. Waltman (USDA, NRCS-NSSC), Roger Kanable (USDA, NRCS), Steven C. Schainost (NGPC), Craig Engelhard (USDA, NRCS), James W. Merchant (Center for Advanced Land Management Information Technologies [CALMIT], University of Nebraska, Lincoln [UNL]), Virginia L. McGuire (USGS), Chris Mammoliti (KDWP), James L. Stubbendieck (UNL), David A. Mortensen (UNL), Thomas Wardle (Nebraska Forest Service), David T. Lewis (UNL), Robert F. Diffendal Jr. (Nebraska Conservation and Survey Division-Nebraska Geological Survey) and Jeffrey A. Comstock (OAO Corporation). This project was partially supported by funds from the U.S. Environmental Protection Agency’s Office of Water, Biological Criteria Program. Reverse side and supplementary 1-page versions attached below

Broadwater [SE] Quadrangle, Morrill County, Nebraska

7.5\u27 topgraphic quadrangle showing exposures of bedrock formations and other geologic information. 41° 30\u27 — 41° 37\u2730 102° 45\u27 — 102° 52\u2730 Scale 1:24,000 Completed [n.d.

Ground Water

A geologic overview of the groundwater supply underlying Cheyenne County, Nebraska (1997)

The Sidney Gravel and Kimball Formation; Supposed Parts of the Ogallala Group (Neogene), Are Not Objectively Mappable Units

In the 1930•s. G. L. Lueninghoener and A. L. Lugn prepared geologic maps of several counties. including Kimball and Cheyenne in the southern Nebraska Panhandle. for the Nebraska Geological Survey. Rock units designated as the Kimball Formation and the underlying Sidney Gravel were shown on these maps. Studies by Swinehart (1974). Breyer (1975. 1981). and Diffendal (1985) demonstrated that these units could not be defined in several areas in western Nebraska. Results of this study show clearly that the Kimball Formation and Sidney Gravel cannot be traced for more than a few kilometers from their type areas. The Kimball Formation does not have a base that can be traced with confidence away from th~ type area south of Kimball. No gravel sheet (Sidney Gravel) occurs at this locality beneath the Kimball. Furthermore. at least the lower two of the three gravel lithologies supposedly typical of the formation occur repeatedly throughout the Ogallala sequence. The discontinuous remnant sand and gravel at the type exposure of the Sidney Gravel have the characteristics of the material originally described by Lugn (l939a). To the north. across an intermittent stream. the lower of two sand and gravel bed sequences separated by caliche sandstones is at the same elevation as the type Sidney and could be the same unit. Farther to the north and east of the type exposure. several sand and gravel bed sequences are laterally and vertically discontinuous. Each one could be equivalent to the original Sidney. but none can be traced back to the type area. Complex geometries and possible post-Ogallala deformation also make correlations questionable. Arbitrarily designating rocks as part of the Kimball Formation if they occur high in a local section. as Lueninghoener and Lugn did. is poor practice. Designating any sand and gravel in the Ogallala sequence as the Sidney or always assigning the stratigraphically highest sand and gravel observed at each exposure in the southern Panhandle to the Sidney has resulted in miscorrelations. The formations as originally defined are not mappable. Usage of the terms should be abandoned. and the term Ash Hollow Formation should be used in their place