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Database for the Geologic Map and Structure Sections of the Clear Lake Volcanics, Northern California
This geologic map database is a reproduction of U.S. Geological Survey Miscellaneous Investigations Map I–2362: “Geologic Map and Structure Sections of the Clear Lake Volcanics, Northern California” (Hearn, Donnelly-Nolan, and Goff, 1995). The database consists of a geologic map, three structural cross sections and a table of petrographic data for each map unit by mineral type, abundance, and size. The Clear Lake Volcanics are in the California Coast Ranges about 150 km north of San Francisco. This Quaternary volcanic field has erupted intermittently since 2.1 million years ago. This volcanic field is considered a high-threat volcanic system (Ewert and others, 2005). The adjacent Geysers geothermal field, the largest power-producing geothermal field in the world, is powered by the magmatic heat source for the volcanic field. The geology of parts of the area underlain by the Cache Formation is based on mapping by Rymer (1981); the geology of parts of the areas underlain by the Sonoma Volcanics, Franciscan assemblage, and Great Valley sequence is based on mapping by McLaughlin (1978). Volcanic compositional map units are basalt, basaltic andesite, andesite, dacite, rhyodacite, and rhyolite, based on SiO2 content. Most ages are potassium-argon (K/Ar) ages determined for whole-rock samples and mineral separates by Donnelly-Nolan and others (1981), unless otherwise noted. A few ages are carbon-14 ages or were estimated from geologic relationships. Magnetic polarities are from Mankinen and others (1978; 1981) or were determined in the field by B.C. Hearn, Jr., using a portable fluxgate magnetometer. Thickness for most units is estimated from topographic relief except where drill-hole data were available. This database does not reproduce all elements of the original publication. Omissions include the chart and figures showing erupted volumes of different lava types through time, and the chart and diagram for the correlation of map units. Users of this database are highly encouraged to cross reference this database with the original publication.
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Database for the geologic map of Lassen Volcanic National Park and vicinity, California - Geodatabase
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A database of geologic map of Lassen Volcanic National Park as described in the original abstract: The geologic map of Lassen Volcanic National Park (LVNP) and vicinity encompasses 1,905 square kilometers at the south end of the Cascade Range in Shasta, Lassen, Tehama, and Plumas Counties, northeastern California. Most of the map area is underlain by middle to late Pleistocene volcanic rocks; Holocene, early Pleistocene, and late Pliocene volcanic rocks (less than 3.5 m.y.) are less common. The southernmost Cascade Range consists of a regional platform of basalt and basaltic andesite, with subordinate andesite and sparse dacite, erupted from small, relatively short-lived volcanoes. Nested within these regional volcanoes are "volcanic centers," defined as large, long-lived, composite, calc-alkaline edifices erupting the full range of compositions from basalt to rhyolite, but dominated by andesite and dacite. Volcanic centers are produced by the focusing of basaltic flux from the mantle and resultant enhanced interaction of mafic magma with the crust. Collectively, volcanic centers mark the axis of the southernmost Cascade Range. The map area includes the entire, presently active, Lassen Volcanic Center, parts of three older volcanic centers (Maidu, Dittmar, and Latour), and the products of regional volcanism. The deposits of several glacial advances are widespread.
Database of the Geologic Map of the Lassen Peak, Chaos Crags, and Upper Hat Creek Area, California - Database
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A database of geologic map of Lassen Peak, Chaos Crags, and Upper Hat Creek volcanic area as described in the original abstract: The Lassen Peak, Chaos Crags, and Upper Hat Creek map area lies near the southern end of the Cascade Range in northern California. The map area includes parts of the three elements that together form the Lassen volcanic center: the Lassen dacitic dome field, the Central Plateau andesitic lava field, and the underlying deeply eroded and partly altered Brokeoff andesitic stratocone. The Lassen volcanic center is the southernmost active long-lived center of the present-day Cascades volcanic arc. This geologic map contributes to understanding the youngest major volcanic events in the evolution of the Lassen dacitic dome field and provides the basis for a revised assessment of its volcano hazards by emphasizing the youngest eruptive products of the dome field. The most recent eruptive activity, mainly steam-blast eruptions, occurred intermittently between May, 1914, and June, 1917, and climaxed during a week of magmatic eruptions of Lassen Peak in May, 1915. The original report consists of a geologic map and an accompanying explanatory pamphlet. Geologic mapping was compiled at a scale of 1:24,000 for the entire mapping area with some 1:2,500-scale mapping for the summit area of Lassen Peak. The geologic mapping was compiled as a digital geologic map database in ArcInfo GIS format.
Database of the Geologic Map of the Lassen Peak, Chaos Crags, and Upper Hat Creek Area, California - Database
공공데이터포털
A database of geologic map of Lassen Peak, Chaos Crags, and Upper Hat Creek volcanic area as described in the original abstract: The Lassen Peak, Chaos Crags, and Upper Hat Creek map area lies near the southern end of the Cascade Range in northern California. The map area includes parts of the three elements that together form the Lassen volcanic center: the Lassen dacitic dome field, the Central Plateau andesitic lava field, and the underlying deeply eroded and partly altered Brokeoff andesitic stratocone. The Lassen volcanic center is the southernmost active long-lived center of the present-day Cascades volcanic arc. This geologic map contributes to understanding the youngest major volcanic events in the evolution of the Lassen dacitic dome field and provides the basis for a revised assessment of its volcano hazards by emphasizing the youngest eruptive products of the dome field. The most recent eruptive activity, mainly steam-blast eruptions, occurred intermittently between May, 1914, and June, 1917, and climaxed during a week of magmatic eruptions of Lassen Peak in May, 1915. The original report consists of a geologic map and an accompanying explanatory pamphlet. Geologic mapping was compiled at a scale of 1:24,000 for the entire mapping area with some 1:2,500-scale mapping for the summit area of Lassen Peak. The geologic mapping was compiled as a digital geologic map database in ArcInfo GIS format.
i08 GeologicUnits SacramentoValley
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This data set is a series of polygons denoting the geologic units mapped in USGS Publication MF-1790, "Geologic Map of the Late Cenozoic Deposits of the Sacramento Valley and Northern Sierran Foothills, California" (Helley and Harwood,1985). This data set was created by scanning the five- original sheets from USGS Publication MF-1790 (Helley and Harwood, 1985), the five sheets were georeferenced individually and the geologic information was digitized using AutoCAD 2006. The accuracy of the digitized lines was deemed to be within acceptable error tolerances, with the digitized lines accurately matching the original drafted lines in USGS Publication MF-1790 (Helley and Harwood, 1985). In general, the width of the contact lines on the paper copy, accounting for scale, ranged up to about 20 meters (66 feet). During the original digitization, minor topological mistakes (such as identical rock units on both sides of a lithologic contact or unclosed polygons) and omissions (such as unidentified lithologic units) were applied according to the best available knowledge. Comparisons were made between the original mylar and colorized field sheets (as available), in addition to the Geologic Map of the Battle Creek Fault Zone, Northern Sacramento Valley, California (USGS Map MF-1298, 1981), the Geologic Map of the Chico Monocline and Northeastern Part of the Sacramento Valley, California (USGS Miscellaneous Investigations Series Map I-1238, 1981), the Geologic Map of the Red Bluff 30' X 60' Quadrangle, California (USGS Geologic Investigation Series Map I-2542, 1995), and the Geologic Map of the Whitmore Quadrangle, California (Geologic Quadrangle Map GQ-993) . The correlation and description of geologic units were excerpted from USGS Publication MF-1790m (Helley and Harwood, 1985).
Recalculated geochemistry data for volcanic rocks in the Mushroom Rock region, northeastern California
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Recalculated geochemistry data for bedrock volcanic samples listed in Table 1 Volcanic Rock Samples. Samples collected from the Mushroom Rock region, northeastern California.
Recalculated geochemistry data for volcanic rocks in the Mushroom Rock region, northeastern California
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Recalculated geochemistry data for bedrock volcanic samples listed in Table 1 Volcanic Rock Samples. Samples collected from the Mushroom Rock region, northeastern California.
Database for the geologic map of the central San Juan caldera cluster, southwestern Colorado
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This geodatabase contains all the geologic map information for the Geologic Map of the San Juan caldera cluster, southwestern Colorado and is part of U.S. Geological Survey Geologic Investigations Map Series I-2799. The San Juan Mountains are the largest erosional remnant of a composite volcanic field that covered much of the southern Rocky Mountains in middle Tertiary time. The San Juan field consists mainly of intermediate-composition lavas and breccias, erupted about 35-30 Ma from scattered central volcanoes (Conejos Formation) and overlain by voluminous ash-flow sheets erupted from caldera sources. In the central San Juan Mountains, eruption of at least 8,800 km3 of dacitic-rhyolitic magma as nine major ash flow sheets (individually 150-5,000 km3) was accompanied by recurrent caldera subsidence between 28.3 Ma and about 26.5 Ma. Voluminous andesitic-dacitic lavas and breccias were erupted from central volcanoes prior to the ash-flow eruptions, and similar lava eruptions continued within and adjacent to the calderas during the period of more silicic explosive volcanism. Exposed calderas vary in size from 10 to 75 km in maximum dimension, the largest calderas being associated with the most voluminous eruptions.
Database for the geologic map of the central San Juan caldera cluster, southwestern Colorado
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This geodatabase contains all the geologic map information for the Geologic Map of the San Juan caldera cluster, southwestern Colorado and is part of U.S. Geological Survey Geologic Investigations Map Series I-2799. The San Juan Mountains are the largest erosional remnant of a composite volcanic field that covered much of the southern Rocky Mountains in middle Tertiary time. The San Juan field consists mainly of intermediate-composition lavas and breccias, erupted about 35-30 Ma from scattered central volcanoes (Conejos Formation) and overlain by voluminous ash-flow sheets erupted from caldera sources. In the central San Juan Mountains, eruption of at least 8,800 km3 of dacitic-rhyolitic magma as nine major ash flow sheets (individually 150-5,000 km3) was accompanied by recurrent caldera subsidence between 28.3 Ma and about 26.5 Ma. Voluminous andesitic-dacitic lavas and breccias were erupted from central volcanoes prior to the ash-flow eruptions, and similar lava eruptions continued within and adjacent to the calderas during the period of more silicic explosive volcanism. Exposed calderas vary in size from 10 to 75 km in maximum dimension, the largest calderas being associated with the most voluminous eruptions.
Data release of Geologic data for the Aeromagnetic Map of Northeastern California
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This digital data release contains geospatial geologic data compiled for northeastern California, a region predominantly covered by Quaternary and Neogene volcanic rocks. Geologic map data were compiled for the purposes of interpreting data from two aeromagnetic surveys that were flown for the area; geologic compilation focused on the existence and location of faults and volcanic features - those geologic elements considered most likely to produce a magnetic anomaly. Geologic data, compiled from published sources, include the location and characteristics of geologic contacts and faults, mapped geologic polygons, boundaries of volcanic edifices, and the location of volcanic vents. The digital geologic database presented here is a companion dataset to two data releases of geophysical data from the aeromagnetic surveys. Both the geologic and geophysical data are intended to support the eventual interpretive USGS publication "Aeromagnetic Map of Northeastern California ". The geologic database includes spatial feature classes that collectively contain the geologic information that will be presented in the published map plate. The spatial data are accompanied by non-spatial tables that describe the sources of geologic information, a description of geologic map units, a glossary of terms, and a Data Dictionary that duplicates the Entity and Attribute information contained in the metadata file. Spatial data are also released as shapefiles.
Data release of Geologic data for the Aeromagnetic Map of Northeastern California
공공데이터포털
This digital data release contains geospatial geologic data compiled for northeastern California, a region predominantly covered by Quaternary and Neogene volcanic rocks. Geologic map data were compiled for the purposes of interpreting data from two aeromagnetic surveys that were flown for the area; geologic compilation focused on the existence and location of faults and volcanic features - those geologic elements considered most likely to produce a magnetic anomaly. Geologic data, compiled from published sources, include the location and characteristics of geologic contacts and faults, mapped geologic polygons, boundaries of volcanic edifices, and the location of volcanic vents. The digital geologic database presented here is a companion dataset to two data releases of geophysical data from the aeromagnetic surveys. Both the geologic and geophysical data are intended to support the eventual interpretive USGS publication "Aeromagnetic Map of Northeastern California ". The geologic database includes spatial feature classes that collectively contain the geologic information that will be presented in the published map plate. The spatial data are accompanied by non-spatial tables that describe the sources of geologic information, a description of geologic map units, a glossary of terms, and a Data Dictionary that duplicates the Entity and Attribute information contained in the metadata file. Spatial data are also released as shapefiles.
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