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FRINATEK-Fri mat.,naturv.,tek

A 100 Myr paleomagnetic data gap: Investigating anomalous behaviour of Earth’s magnetic field in the middle Paleozoic

Alternative title: Et paleomagnetisk datagap på 100 millioner år: Undersøkelse av unormal oppførsel av jordens magnetfelt i midten av paleozoikum

Awarded: NOK 8.0 mill.

Earth’s magnetic field is essential for the development of life on Earth, and today it protects us from solar storms that can harm modern technology. Earth’s magnetic field is formed deep inside of our planet, in the outer core, by flowing hot liquid iron. We can imagine the magnetic field as a bar magnet inside the earth, that is aligned with Earth’s rotation axis. Rocks can capture Earth’s magnetic field when they form, so by studying millions of years old rocks, we can find out about Earth’s magnetic field at that time. We have a good understanding of the magnetic field of the last 500 million years, except for one big gap: the middle Paleozoic (440-340 million years ago). Many middle Paleozoic rocks have a poor memory of the magnetic field at that time, and show that they remember magnetic fields from younger times instead. PANDA will study the behaviour and strength of Earth’s magnetic field in the middle Paleozoic, by looking at changes in the direction and intensity, and the number of times the magnetic poles switched position. PANDA will gather data in four locations from sedimentary and volcanic rocks, and use a newly developed powerful microscope, that can look at magnetisations in unprecedented detail. The results from PANDA will be used to constrain fundamental behaviour and strength of Earth’s magnetic field, as well as plate tectonic reconstructions, in a time period that hosts the first forests and terrestrial vertebrates on Earth.

In the middle Paleozoic (~440-340 million years ago), life on land emerged, the first plants and forests developed, and many biotic crises took place. Geoscience research relies on paleogeographical reconstructions of the continents, which are based on paleomagnetism; the study of Earth’s magnetic field as recorded by rocks. However, the middle Paleozoic forms a conspicuous gap in our knowledge of Earth’s magnetic field. The exact limits of this gap have not been established yet, but there is a striking scarcity of high-quality, unambiguous paleomagnetic data for around 100 million years, hindering our understanding of the deep interior of our planet. Importantly, the absence of high quality paleomagnetic data in this time prevents the understanding of the behaviour of Earth’s magnetic field in this key interval for Earth evolution, and hampers the use of paleomagnetism as a tool for dating and correlation. A recurring observation in middle Paleozoic paleomagnetism is that magnetisations are often below sensitivity limits of traditional magnetometers, making them effectively unmeasurable with standard techniques. I hypothesise that scarcity of middle Paleozoic paleomagnetic data does not reflect a lack of dedicated effort or community interest, but is an intrinsic manifestation of a significant natural process not yet clearly identified or adequately understood. PANDA will investigate promising sedimentary and igneous rocks from the late Silurian to early Carboniferous with new high precision techniques. Advances in magnetometer technology in the last few years increased the sensitivity of equipment, which now allows measurements of samples that were previously unmeasurable. PANDA will use the newly developed Quantum Diamond Microscope, to map magnetisations of minerals inside rocks in unprecedented detail. Altogether, PANDA will elucidate the behaviour of Earth’s magnetic field, show whether it was anomalous, and if so, for how long this lasted.

Funding scheme:

FRINATEK-Fri mat.,naturv.,tek