Improving the quality of anomalously low paleointensity estimates obtained from Carboniferous-age rocks
Abstract
Paleomagnetism provides a unique set of geophysical data that helps constrain mechanisms in the Earth's deep interior throughout geologic history. Studying the changes in the strength of the Earth's magnetic field provides insight into the evolution of the outer core and changes in geodynamo within. Peering far back into Earth's past, however, is not a straight-forward task. Older rocks have longer and more complex histories than the rocks paleomagnetic techniques are usually tested on, which are often young or artificial. Different protocols have been proposed to improve paleointensity data- either changing the order of de- and remagnetization experimental steps or adding/removing demagnetization steps.
One of the main causes of problems in paleointensity experiments is the presence of large (multi-domain) grains of magnetite, which have asymmetric acquisition and loss of magnetization. Studies have shown that multi-domain grains of magnetite lose their magnetization permanently when cooled below their Verwey transition (125 K) in a magnetic vacuum. In this study, we aim to determine if the addition of a liquid nitrogen demagnetization (77K) after each heating step can improve the quality of data used to generate paleointensity estimates by removing the non-linear multi-domain grain effect. With the additional, improved data, we aim to fill in the dearth in paleointensity estimates during the Carboniferous period, using samples collected from the Kinghorn lavas in Scotland, aged 345-332 Ma. Recent work from Russian samples of Devonian age showed an anomalously weak field. These Kinghorn data sustain this weak field into the Carboniferous, with fields as low as those seen in recent Ediacaran work.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMGP33A..04G
- Keywords:
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- 1503 Archeomagnetism;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 1517 Magnetic anomalies: modeling and interpretation;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 1521 Paleointensity;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 1595 Planetary magnetism: all frequencies and wavelengths;
- GEOMAGNETISM AND PALEOMAGNETISM