Detailed study on Paleodirections of Gran Canarian Mid‐Miocene Lava Flows covering a reversal of the earth’s magnetic field

Detailed study on Paleodirections of Gran Canarian Mid‐Miocene Lava Flows covering a reversal of the earth’s magnetic field

van Klaveren, S.D.

Molengraaff Fonds

2017

Reversals of the Earth’s magnetic field are governed by complex processes in the liquid outer core, which are still not fully understood. Rock records that cover a reversal are rare. Here we show a high resolution directional description of a Mid-Miocene reversal captured in a thick basaltic sequence formed during the shield building phase of Gran Canaria. We sampled 100 lava flows and determined the direction (Virtual Geomagnetic Pole, VGP) of each flow by AF demagnetization and thermal demagnetization methods on a 2G SQUID cryogenic magnetometer. The results do not directly approve a dynamically coupling between the lower mantle ultra low velocity zones and the processes in the outer core as is hypothesized in previous work. The inclinations show several excursions, where the declination does not, implicating the VGPs move along the great circle of Gran Canaria during these excursions. A stable transitional state has existed before the reversal according to a clustering of VGPs near South America for eleven successive flows. The reversal is recorded within five flows and these VGPs are the only ones that do not plot along this great circle, which is very remarkable. The duration of this reversal is estimated on a minimum of 1500 years, based on relatively high minimal eruption rates of three eruptions per century.

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Utrecht University

Geoscience Reports

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