1,721,105 research outputs found
Geologic Map Showing Configuration of the Bedrock Surface, North Platte, 1 ° x 2 ° Quadrangle, Nebraska
Get PDFThe 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. 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.
Scale = 1:250,000 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
The Delaware Limestone (Middle Devonian) of Southwestern Ontario, Canada
Get PDFThe Delaware Limestone of southwestern Ontario was originally called a part of the Corniferous Limestone by Murray (184.3-53). Since that time the same outcroppings have been designated, either wholly or partially, as the Onondaga Formation, the Big Lime, Delaware Limestone, Norfolk Formation, Dundee Limestone, Columbus Limestone, and the Dundee (= Delaware) Limestone. As recently as 1971 the names Dundee Limestone and Delaware Limestone were used for the same formation. Hand specimen and petrographic study of samples from nineteen localities in southwestern Ontario indicates that the limestones of the formation exposed on the Niagara peninsula are intermediate in type between the rocks of the Delaware Limestone of Ohio and those of the Dundee Limestone of Michigan. The formation in Ontario becomes more like the Delaware Limestone southeast of the Findlay Arch and becomes more like the Dundee Limestone northwest of it. A comparison of the fauna and flora shows that more key species are common to the Ontario and Ohio formations than to the Ontario and Michigan ones. On both paleontological and historical grounds, the rocks in Ontario should be designated as the Delaware Limestone
Topographic Maps
Get PDFTopographic maps show the general configuration of the land surface, including its relief and the position of natural and man-made features. The configuration is shown commonly by contour lines, imaginary lines connecting all points of equal elevation on the earth\u27s surface above or below a datum plane such as mean sea level. When the land slope is steeper the contour lines are closer together. Topographic maps at scales of one inch to a mile or greater (shown as 1:63,360 on the map) are used in many ways. They are particularly important in preparation of various types of geologic maps and cross sections that can be used in locating, for example, mineral resources or aquifers. Explorations of the geology and natural resources of the American West were initiated by the King, Wheeler, Hayden, and Powell Surveys from 1867 to 1879, but major topographic mapping efforts began only after 1881. In December 1885 John Wesley Powell, second director of the United States Geological Survey, testified before a joint committee of Congress about the national need for topographic maps of the country. He said that topographic mapping of the country could be completed in twenty-four years. By 1894 about one-fifth of the United States was depicted on topographic maps. Mapping of the United States Great Plains at a scale of 1:24,000 was completed in 1994 by the United States Geological Survey. Topographic maps of the Canadian Prairie Provinces have been completed at a scale of 1:50,000 by the Canada Map Office
Evidence for Quaternary Piracy of Pumpkin Creek, South-Central Morrill County, Nebraska
Get PDFThe occurrence of Quaternary anorthosite-rich sand and gravel deposits in south-central Morrill County, Nebraska, southeast of the mouth of Pumpkin Creek and south of the North Platte River suggests that the creek formerly flowed farther east than it does today. This eastern extension of the creek was abandoned when a headward-cutting tributary of the North Platte River eroded through the divide between Pumpkin Creek and the North Platte just east of Jail and Courthouse rocks, and captured Pumpkin Creek
The Rush Creek Structure, Garden County, Nebraska
Get PDFDetailed field mapping of surface outcrops in southern Garden County, Nebraska, has revealed a drop of 200 feet in three miles in the elevation of the contact between the Ogallala and pre-Ogallala (probably Brule) Formations exposed on the east side of Rush Creek. Beds of silt, sand, siltstone, and volcanic ash in the are a locally dip to the northwest at angles of up to 8½°. The contact between the two formations cannot be seen on the west side of Rush Creek but beds in the Ogallala Formation there dip to the north and northeast. The unusually long valley of Rush Creek runs along the axis of a north plunging syncline which probably controls the position of springs in the Ogallala Formation feeding the only large perennial stream on the south side of the North Platte River in the county. Ogallala outcrops at river level along the south bank of the North Platte River just southeast of Lisco, Nebraska, are also related to this local syncline
Synthetic-Aperture Radar Imagery and Digital Shaded-Relief Map of Northwest Nebraska: Probable Structures and Geomorphic Features of the Region
Get PDFIn 1988 the United States Geological Survey published a radar image mosaic of an area roughly that of the Alliance. Nebraska 1° × 2° topographic map at the same scale, 1:250,000. Striking near-parallel valley trends in the vicinity of Chadron, Nebraska, may be related to jointing or possible faulting. Two sets, oriented approximately N30E and N28W, are obvious in the area east of Chadron. Sets south of Chadron on the Pine Ridge trend approximately N40E and N50W. On the Pine Ridge west of Fort Robinson in Sioux County some E-W and N-S features are also apparent. Other features that may be structurally related are prominent N20W and N30W drainages that cross Box Butte County and seem to continue into the Sand Hills affecting dune position. The Toadstool Park (?Whalen) Fault shown by DeGraw (1971, figure 5) also appears present on the image
Brule (SW) Quadrangle, Keith and Perkins Counties, Nebraska
Get PDF7.5\u27 topgraphic quadrangle showing exposures of bedrock formations and other geologic information.
41° 00\u27 — 41° 07\u2730
101° 52\u2730 — 102° 00\u27
Scale 1:24,000
High resolution .tif file attached below as supplemental fil
Broadwater [SE] Quadrangle, Morrill County, Nebraska
Get PDF7.5\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.]
High resolution .tif file attached below as supplemental fil
Keystone Quadrangle, Keith County, Nebraska
Get PDF7.5\u27 topgraphic quadrangle showing exposures of bedrock formations and other geologic information.
41° 07\u2730 to 41° 15\u27
101° 30\u27 to 101° 37\u2730
Scale 1:24,000
Completed July 16, 1976
High resolution .tif file (130 MB) attached below as supplemental fil
The Inapplicability of the Concept of the Sidney Gravel to the Ogallala Group (Late Tertiary) in Part of Southern Banner County, Nebraska
Get PDFA series of geologic maps of counties in western Nebraska was prepared for the Nebraska Geological Survey during the mid-1 930s. These maps showed the distribution of rock units of Tertiary age including a formation designated as the “Sidney.” The Sidney Gravel was described as a widespread sheetlike complex of channel deposits, but with small areas where it is not developed. In southern Banner County, Nebraska, there are several channels filled with sand and gravel that were mapped as Sidney in this series. Recently one of these channel fills has been observed to cut across the other. The fills are separated from one another by an opaline silcrete bed. In places these deposits directly overlie beds mapped previously as parts of the younger Kimball formation. While the local Ogallala lithostratigraphic relationships can be worked out, the exact relationship between the fills in Banner County and the type Sidney could not be precisely determined in the 1930s and cannot be worked out today. The concept of a gravel sheet does not apply to the study area in Banner County
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