Paleomagnetism of Middle Devonian pillow lavas from Germany

For decades, scientists have tried to obtain paleomagnetic data from Devonian rocks, but acquiring accurate data from this time period remains problematic. The lack of data has traditionally been interpreted as caused by overprinting during the Kiaman reverse superchron, but recent studies have suggested that the field could have had a non-dipolar configuration. Either way, overprinting is a common problem, although an overprinting mechanism is sometimes lacking. In other cases, data is not interpretable due to large scatter, and a clear explanation has not been found to date.

The lack of paleomagnetic data from the Devonian significantly hampers the fundamental understanding of long-term (>100 Myr) magnetic field behaviour and the creation of geodynamo models. However, paleointensities can sometimes be successfully determined, and show that the field was weak to extremely weak during the Late Devonian, with values similar to the Ediacaran.

To further constrain the onset of the weak field period, we sampled a succession of Middle Devonian pillow lavas that outcrop in the Philippstein Quarry near Braunfels, Germany. These lavas are subject to some faulting, but are fresh looking and consist of unaltered, unmetamorphosed igneous rock. Pillow lavas cool quickly, which leads to stable magnetic behavior, making them well-suited for magnetic analyses.

Here we present our results of traditional paleomagnetic analyses to determine the direction and intensity of the Devonian paleomagnetic field.