Aeromagnetic survey map of Sacramento Valley, California
Links
- Document: Map (21.5 MB pdf)
- Datasets:
- Chico survey aeromagnetic data (383.6 MB txt)
- Sacramento survey aeromagnetic data (639 MB txt)
- Redbluff survey aeromagnetic data (346.5 MB txt)
- Aeromagnetic gridded values (26.8 MB txt)
- Maximum horizontal gradients (larger than mean value) (346 KB txt)
- Maximum horizontal gradients (smaller than mean value) (238 KB txt)
- Metadata:
- Read Me: Read me (9 KB txt)
- Download citation as: RIS | Dublin Core
Abstract
Three aeromagnetic surveys were flown to improve understanding of the geology and structure in the Sacramento Valley. The resulting data serve as a basis for geophysical interpretations, and support geological mapping, water and mineral resource investigations, and other topical studies. Local spatial variations in the Earth's magnetic field (evident as anomalies on aeromagnetic maps) reflect the distribution of magnetic minerals, primarily magnetite, in the underlying rocks. In many cases the volume content of magnetic minerals can be related to rock type, and abrupt spatial changes in the amount of magnetic minerals commonly mark lithologic or structural boundaries. Bodies of serpentinite and other mafic and ultramafic rocks tend to produce the most intense positive magnetic anomalies (for example, in the northwest part of the map). These rock types are the inferred sources, concealed beneath weakly magnetic, valley-fill deposits, of the most prominent magnetic features in the map area, the magnetic highs that extend along the valley axis. Cenozoic volcanic rocks are also an important source of magnetic anomalies and coincide with short-wavelength anomalies that can be either positive (strong central positive anomaly flanked by lower-amplitude negative anomalies) or negative (strong central negative anomaly flanked by lower-amplitude positive anomalies), reflecting the contribution of remanent magnetization. Rocks with more felsic compositions or even some sedimentary units also can cause measurable magnetic anomalies. For example, the long, linear, narrow north-trending anomalies (with amplitudes of <50 nanoteslas [nT]) along the western margin of the valley coincide with exposures of the Mesozoic Great Valley sequence. Note that isolated, short-wavelength anomalies, such as those in the city of Sacramento and along some of the major roads, are caused by manmade features.
Study Area
| Publication type | Report |
|---|---|
| Publication Subtype | USGS Numbered Series |
| Title | Aeromagnetic survey map of Sacramento Valley, California |
| Series title | Open-File Report |
| Series number | 2015-1186 |
| DOI | 10.3133/ofr20151186 |
| Year Published | 2015 |
| Language | English |
| Publisher | U.S. Geological Survey |
| Publisher location | Reston, VA |
| Contributing office(s) | Geology, Minerals, Energy, and Geophysics Science Center |
| Description | Map: 32.40 x 44.91 inches; Datasets; Metadata; Read Me |
| Country | United States |
| State | California |
| Other Geospatial | Sacramento Valley |
| Online Only (Y/N) | Y |
| Additional Online Files (Y/N) | Y |
| Google Analytic Metrics | Metrics page |