 |
|
|
||||
| Data Series 138: Nebraska, Kansas, and Oklahoma Aeromagnetic Compilation |
|
| About USGS / Science Topics / Maps, Products & Publications / Education / FAQ |
|
Aeromagnetic anomalies are due to variations in the Earth's magnetic field caused by the uneven distribution of magnetic minerals (primarily magnetite) in the rocks that make up the upper part of the Earth's crust. The features and patterns of the aeromagnetic anomalies can be used to delineate details of subsurface geology including the locations of buried faults, magnetite-bearing rocks, and the thickness of surficial sedimentary rocks (which are generally nonmagnetic). This information is valuable for mineral exploration, geologic mapping, and environmental studies.
The Nebraska, Kansas, and Oklahoma aeromagnetic maps are constructed from grids that combine information (see data processing details) collected in 28 separate aeromagnetic surveys conducted between 1954 and 1985. (The Nebraska map contains data from 12 separate surveys conducted between 1963 and 1980. The Kansas map contains data from 7 surveys conducted between 1975 and 1985. The Oklahoma map contains data from 9 surveys conducted between 1954 and 1980.) The data from these surveys are of varying quality. The design and specifications (terrain clearance, sampling rates, line spacing, and reduction procedures) varied from survey to survey depending on the purpose of the project and the technology of that time. Every attempt was made to acquire the data in digital form. Most of the available digital data were obtained from aeromagnetic surveys flown by the U.S. Geological Survey (USGS), flown on contract with the USGS, or were obtained from other Federal agencies and State universities. The Kansas data were flown by and acquired from the Kansas Geological Survey (Yarger and others, 1981). Some of the 1954, 1963, and 1964 data are available only on hand-contoured maps and had to be digitized. These maps were digitized along flight-line/contour-line intersections, which is considered to be the most accurate method of recovering the original data. Digitized data are available as USGS Open-File Report 99-0557. All surveys have been continued to 304.8 m (1,000 ft) above ground and then blended or merged together. An index plot gives an overview of the original surveys, and a data table summarizes the detailed specifications of the surveys. The final aeromagnetic map can be downloaded as a grid with a 1,000-m grid interval.
Also included are maps and grids of some of the individual surveys at their original flight altitude that were generated with a finer grid spacing due to having a finer flight-line spacing. These were then regridded to the final grid spacing of 1,000 m for use in the State merge.
Our priority in the construction of the aeromagnetic compilations for the States of Nebraska, Kansas, and Oklahoma was always to acquire the best resolution aeromagnetic data sets for any given area. (See the Nebraska, Kansas, and Oklahoma aeromagnetic data index maps.) Where local high-resolution surveys were not available, in either digital or digitized format, we used aeromagnetic data collected by the National Uranium Resource Evaluation (NURE) program of the U.S. Department of Energy, which is available in digital format and covers the entire State. However, because magnetic surveying was not the primary objective in the design of the NURE surveys, these data are subject to certain limitations. Although the NURE surveys were flown at altitudes close to the reduction datum level, the spacing between flight lines ranged from 4,800 m to 9,600 m (3 to 6 mi). The wide spacing between flight lines flown at low altitudes over surface rock units having high magnetizations causes anomalies with short spacial wavelengths to be elongated between flight lines, producing lineations perpendicular to the flight-line direction and 'pearl string' anomalies along the flight line. Also, problems related to the reduction of navigation control and inconsistent datum levels between NURE surveys can cause herringbone features, which are sometimes observed within and at the boundaries of these surveys.
This project was supported by the Mineral Resource Program / Crustal Imaging and Characterization Team of the USGS.
Top || NE, KS, & OK Mag || References || Crustal Team
| AccessibilityFOIAPrivacyPolicies and Notices | |
  |
|