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Physical properties of geologic units are important for geophysical interpretation because they provide the tie between lithology and geophysical fields. For gravity data, the applicable physical property is bulk density, which is the overall mass per unit volume of rocks, sediments, and their pore spaces. Bulk dry density is the mass per unit volume measured when the sample is dry. Saturated density is the mass per unit volume measured when the sample is saturated with fresh water, which has a density of 1,000 kg/m^3. The two values are commonly compared in order to determine the porosity of a sample, that is, the percentage of the volume that is composed of open space. Density is commonly reported in kilograms...
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Regional surface elevation grid files (provided in Grid eXchange File format) were used to study crustal architecture beneath the Southern Midcontinent (USA) by McCafferty and others (2019). The study covered a rectangular, multi-state area of 924 by 924 kilometers centered on Missouri, and a corresponding volume extending from the topographic surface to a depth of 50 kilometers below sea level. The grid files (magnetic field observation surface, topographic surface, Precambrian basement surface, and Moho interface) were used to construct templates and initial physical property models for 3D inversions. A masked version of the Precambrian basement surface grid was used to remove inverted densities and magnetic susceptibilities...
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The U.S. Geological Survey (USGS) collected rock physical property measurements to help understand causative sources of gravity and magnetic survey anomalies in the Iron Mountain-Menominee region, Michigan-Wisconsin. A total of 2,356 measurements of magnetic susceptibility and density from 152 locations have been conducted on Precambrian rocks. The measurements aid in interpretation of newly acquired ground-based gravity and airborne magnetic data that are helping to understand concealed Precambrian geology and potential mineral resources. Multiple measurements were made at each location and sample lithology units were derived from existing USGS geologic maps noted in the supplemental information section of the...
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Regional grid files and 3D voxel models were used to study crustal architecture beneath the Southern Midcontinent (USA) by McCafferty and others (2019). The study covered a rectangular, multi-state area of 924 by 924 kilometers centered on Missouri, and a corresponding volume extending from the topographic surface to a depth of 50 kilometers below sea level. The grid files consist of surface grids (magnetic field observation surface, topographic surface, Precambrian basement surface, and Moho interface) used to construct templates and initial physical property models for 3D inversions, observed geophysical data grids (Bouguer gravity anomaly and reduced-to-pole (RTP) aeromagnetic anomaly) used in the inversions,...
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The U.S. Geological Survey (USGS) collected rock magnetic susceptibility measurements to help understand causative sources of airborne magnetic survey anomalies in the Iron Mountain-Menominee region, Michigan-Wisconsin. The measurements were made on outcrop and drill core using a handheld magnetic susceptibility meter. The measurements facilitate the interpretation of aeromagnetic anomalies and help map the distribution of Precambrian rocks in the region.
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This 3D voxel model of density in GOCAD format was used to study crustal architecture beneath the Southern Midcontinent (USA) by McCafferty and others (2019). The study covered a rectangular, multi-state area of 924 by 924 kilometers centered on Missouri, and a corresponding volume extending from the topographic surface to a depth of 50 kilometers below sea level. The 3D voxel model describes the density of the crust and upper mantle as interpreted using 3D inversion. The masked version excludes densities in areas where the Precambrian basement surface elevations are unknown. The individual voxel elements are 2,000 by 2,000 meters by 500 meters thick. The GOCAD voxel (GRID3D or Voxet) file format is documented...


    map background search result map search result map Physical-property measurements on core samples from drill-holes DB-1 and DB-2, Blue Mountain Geothermal Prospect Physical Properties by Geologic Unit in the Southern San Luis Basin, New Mexico Crustal Architecture Beneath the Southern Midcontinent (USA) -- Data Grids and 3D Geophysical Models Crustal and upper mantle density model for the southern midcontinent Elevation surface grids for the southern midcontinent Density and magnetic susceptibility measurements on Precambrian rocks in the Iron Mountain-Menominee region, Michigan-Wisconsin Magnetic susceptibility measurements in the Iron Mountain-Menominee region, Michigan-Wisconsin Magnetic susceptibility measurements in the Iron Mountain-Menominee region, Michigan-Wisconsin Density and magnetic susceptibility measurements on Precambrian rocks in the Iron Mountain-Menominee region, Michigan-Wisconsin Physical Properties by Geologic Unit in the Southern San Luis Basin, New Mexico Crustal Architecture Beneath the Southern Midcontinent (USA) -- Data Grids and 3D Geophysical Models Crustal and upper mantle density model for the southern midcontinent Elevation surface grids for the southern midcontinent