Primeval turn of the Iberian Peninsula?

Magnetic signals indicate rock rotation 300 million years ago

Moving History: The Iberian Peninsula may have turned in the course of its genesis. © NASA / Jeff Schmaltz
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The Iberian peninsula may have turned in the course of its history. At least magnetic signals in minerals from the northwest of Spain, as researchers report. Accordingly, the rock has experienced a rotation of nearly 60 degrees about 300 million years ago. The result of this process can still be seen today as a kink in the Cantabrian Mountains.

The geography of the Iberian Peninsula is a mystery to scientists. Because the Cantabrian Mountains - the extension of the Pyrenees in northwestern Spain - has a strange curvature. These are, as the experts agree, was not there from the beginning. The kink must have formed after the original formation of the mountain range - but how did it come about?

One possible explanation is that the Iberian Peninsula has turned throughout its history. Researchers around the geologist Javier Fernández-Lozano from the University of Salamanca have now studied rocks from the province of Léon in northwestern Spain - and indeed found clues that support this theory.

Collision of two continents

For his study, the team analyzed 320 samples of volcanic rock and limestone from a time when the newly forming Iberian Peninsula was still part of the prehistoric major continent of Godwana on the edge of the Rheian Ocean.

"They deposited on the ocean floor about 440 million years ago, and their constituents then aligned with the earth's magnetic field, " explains Fernández-Lozano. The magnetic signals contained in the rock therefore tell researchers something about the history of the samples. display

Hidden in the rock: Magnetic signals indicate rotation. © J. Fernøndez-Lozano et al.

But there are other magnetic signals in the minerals triggered by a change in the direction of the Earth's magnetic field. According to the researchers, this took place about 120 million years later through a major tectonic event: the so-called Variscan orogeny. The two original continents Godwana and Laurussia collided, whereby the Rheische Ozean closed and a new mountain range developed.

Rotation by 60 degrees

The new magnetic measurements indicate that the rock has not maintained its position after the collision of the two continents. Shortly after this event, the rock of the mountain range must have experienced a rotation of almost 60 degrees. According to researchers, this process during the mountain formation could have affected the entire Iberian Peninsula, which was still in its formation at the time.

"Using the information in the rock, we can demonstrate tectonic activity and better understand how such a rock is created in mountains, " the researchers conclude. (Tectonophysics, 2016; doi: 10.1016 / j.tecto.2016.02.019)

(Tectonophysics, 07.03.2016 - DAL)