Search USGS⌕ Search

USGS · 70223884

On the use of magnetic cleaning in paleointensity studies

Abstract

The use of partial alternating field demagnetization and, to a lesser extent, partial thermal demagnetization has been found useful as a means of removing secondary components of magnetization from rocks used in certain methods of determining paleointensities. During the course of this investigation, which was carried out on lavas erupted during historic times, it was also learned that a partial remanence characterized by relatively low coercivity possessed blocking temperatures throughout the blocking temperature spectrum. On the other hand, a partial remanence characterized by low blocking temperatures possessed only low coercivity.

Explore related subjects

90° N90° S · 180° W ← longitude → 180° E
Source-reported bounding extent: 18.890695349102117° to 19.748609300218842° latitude; -155.93719482421875° to -154.79461669921875° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Richard R. Doell, Peter J. Smith. 1969. On the use of magnetic cleaning in paleointensity studies. https://doi.org/10.5636/jgg.21.579

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

Magnetic and gravity constraints on forearc upper crustal structure and composition, offshore northeast Japan

Marine magnetic and gravity data from the northeast Japan forearc offer insight to the subsurface structure, density and magnetization from which geologic interpretations and tectonic reconstructions can be made. Positive marine magnetic anomalies, on-land geology, drill hole data, and 2-1/2-dimensional models reveal that Kitakami plutons and possibly their associated volcanic rocks constitute part of the modern forearc basement and lie 100-150 km further east than previously thought. A method to create magnetization and density contrast maps was employed to produce a three-dimensional picture of the forearc basement rock properties averaged over a 14-km thickness. -Author

Pacific Ocean↗

Quiet geomagnetic field representation for all days and latitudes

This paper describes a technique for obtaining the quiet-time geomagnetic field variation expected for all days of the year and distribution of latitudes from a limited set of selected quiet days within a year at a discrete set of locations. We used a data set of observatories operated by Indian and USSR scientists in 1976 and 1977 near 75°E longitude as illustration. Our method relies upon spatial smoothing of the decomposed spectral components. An evaluation of the fidelity of the resulting model shows correlation coefficients usually above 0.9 at the lower latitudes and near 0.7 at the higher latitudes with variations identified as dependent upon season and field element.

Journal of Geomagnetism & Geoelectricity↗

Analysis of geomagnetic secular variation during 1980-1985 and 1985- 1990, and geomagnetic models proposed for the 1991 revision of the International Geomagnetic Reference Field

The secular variation of the main geomagnetic field during the periods 1980-1985 and 1985-1990 was analyzed in terms of spherical harmonics up to the eighth degree and order. Data from worldwide magnetic observatories and the Navy's Project MAGNET aerial surveys were used. The resulting pair of secular-variation models was used to update the Definitive Geomagnetic Reference Field (DGRF) model for 1980, resulting in new main-field models for 1985.0 and 1990.0. These, along with the secular-variation model for 1985-1990, were proposed for the 1991 revision of the International Geomagnetic Reference Field (IGRF).

Journal of Geomagnetism & Geoelectricity↗