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At least 1,261 records · Page 70Linked to original sources
USGS1994

Geologic map of the eastern part of the Challis National Forest and vicinity, Idaho

The paper version of the Geologic Map of the eastern part of the Challis National Forest and vicinity, Idaho was compiled by Anna Wilson and Betty Skipp in 1994. The geology was compiled on a 1:250,000 scale topographic base map. TechniGraphic System, Inc. of Fort Collins Colorado digitized this map under contract for N.Shock. G.Green edited and prepared the digital version for publication as a GIS database. The digital geologic map database can be queried in many ways to produce a variety of geologic maps.

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USGS1995

Geologic and topographic maps of the Elysium Paleolake basin, Mars

These geologic and topographic maps show a basin in the Elysium region of Mars that is thought to have been the site of a large paleolake during the most recent period (Amazonian) in Mars’ history (Scott and Chapman, 1991b). The basin, referred to as the Elysium basin, extends for more than 2,000 km across the lowland plains (fig. 1). It is important, not only geologically, but because the amount, location, and duration of liquid water that it may have contained would have been critical factors governing the possible origin and survival of life on Mars. The Elysium basin is the only large depositional basin on Mars where direct evidence, both geologic and topographic, of former water levels and spillways has been found. However, indications of possible paleoshorelines have been observed in several other areas along the highland-lowland boundary (described under Geologic and Physiographic Setting; Parker and others, 1989; De Hon and Pani, 1992; Scott and others, 1992). Our study of the Elysium basin had two objectives, to determine (1) the maximum extent of the basin and (2) the former volume of water in the basin and the sources of this water. To fulfill these objectives, we have compiled this sets of maps. The geologic maps shows the source channels and circumbasin materials, and the topographic map of the paleolake, on a new topographic base, shows former shorelines and drainage channels.

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USGS1994

Geologic map of the MTM-15147 quadrangle, Mangala Valles region of Mars

The map area is in the Mangala - M e mnonia region (fig. 1), which contains remarkably diverse geologic features and terrain types. Studies of the Mariner 9 images revealed the wide range of ages of the major rock units in this region ; age assignments wer e based on the density of impact craters preserved on the various surfaces ( Mutch and others, 1976, p. 56-60; Scott and Carr , 1978; Mut c h and Morris, 1979). The region includes ancient cratered highlands, more sparsely cratered smooth plains, young volcanic plains, and the Mangala Valles channel system. The sinuosity of the streamlined l an dforms within the Man g ala Valles, combined with braided channels evident throughout the lower reaches of the valley system, were recognized as indicators that he Mangala area was subject to substantial erosion by a flowing fluid, most likely water (Milton, 1973; Baker and Milton, 1974; Sharp and Malin , 1975). Recent global mapping based on the Viking Orbiter images (Scott and Tanaka , 1986 ) has refined the relative ages of many rock units on Mars, but it has modified only slightl y the basic interpretations of features in the Mangala- Memnonia region.

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