Full-vector behavior of the geomagnetic field during a mid-Miocene reversal in Gran Canaria: An absolute intensity study

Full-vector behavior of the geomagnetic field during a mid-Miocene reversal in Gran Canaria: An absolute intensity study

Marijnissen, K.A.

Molengraaff Fonds

2017

The dynamo of the solid inner core and liquid outer core gives rise to the Earth’s magnetic field, a field that changes in direction and intensity and can be reversed. This process of geomagnetic reversals is still poorly understood, because only a few sections have been recorded in high resolution, which are crucial to get a better understanding of the geomagnetic reversals. We recorded a good exposed lava sequence in high resolution. Leonhardt et al. (2002) researched this mid-Miocene lava sequence in the west of Gran Canaria before, which contains a reversal. To study the reversal the IZZI-Thellier protocol, an absolute intensity technique, is used. We show what happens to the intensity during the geomagnetic reversal in Gran Canaria around 14.5 Ma based on the IZZI-Thellier protocol. The research contains a field trip to Gran Canaria to sample the 100 lava flows with 8-12 samples per flow. After the fieldwork measurements are made in Fort Hoofddijk at the Utrecht University by using the 2G cryogenic magnetometer based on the IZZI-Thellier protocol and interpreted by the Thellier-GUI. The absolute intensity values are compared to the relative intensity values (pseudo-Thellier). We show that it can be stated that the intensity of the section is lower than expected, a reversal will happens when the intensity is below 5 μT. In the section an excursion, a reversal from reversed to normal and a second excursion are found. The intensity progression is similar to Leonhardt et al. (2002), but due to higher resolution more fluctuation in intensity arises. Furthermore, it can be stated that the intensity is low for a long period, namely 50 flows, before the reversal and after the reversal the intensity gets a higher value than before the reversal.

http://resolver.tudelft.nl/uuid:84a57126-d295-44c9-8f91-cee662fa7040

Utrecht University

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