DETERMINING TRUE PALEOLATITUDE: INSIGHTS FROM THE EDIACARAN OUARZAZATE GROUP

The Ediacaran (635 – 539 Ma) was a dramatic period in Earth’s history which recorded global shifts to ocean geochemistry, climatic upheaval, and hosted the first appearance of widespread complex metazoan life. However, the circumstances surrounding these events remain poorly understood due to paleogeographic reconstructions hindered by the lack of high quality paleomagnetic data and confounding paleomagnetic directions from several cratons. At various times, these data have been attributed to true polar wander, very fast plate tectonics, or a chaotic magnetic field. The Ouarzazate Group in the Anti Atlas Mountains of Morocco is a ~2.5-kilometer-thick succession of predominantly volcanic and subordinate siliciclastic rocks deposited during the middle and late Ediacaran. We present paleomagnetic data from the Bou Azzer inlier of the Ouarzazate Group showing a rapid transition from high, to intermediate, to low inclination directions. These directions are consistent across multiple correlatable stratigraphic profiles and the primary nature of remanence is supported by an intraformational conglomerate test. Magnetostratigraphy was employed to create a high-resolution profile of paleomagnetic directions and magnetic field behavior. When paired with high precision geochronology, the rate of apparent motion is much faster than can be attributed to true polar wander or plate tectonics. This suggests that these rocks recorded a chaotic and non-dipolar Ediacaran magnetic field. To determine paleolatitude, paleomagnetists traditionally rely on the approximation of the time-averaged magnetic field as a dipole which overlaps the spin axis. Siliciclastic successions, particularly those with protracted acquisition of chemical remanence, may provide a time-averaged record of the magnetic field and help to filter magnetic noise and excursions. Despite suffering from inclination shallowing, sedimentary rocks provide a continuous record of the magnetic field rather than the temporal snap shots recorded by volcanic rocks. Using high resolution magnetostratigraphy, sedimentary rocks may reveal information about the geometry of the magnetic field and determine true paleolatitudes from otherwise inexplicable data.