Magnetostratigraphic constraints on the late Ediacaran paleomagnetic enigma

Abstract

Paleogeography of the Ediacaran Period has remained poorly understood because of paleomagnetic studies commonly yielding perplexing or conflicting data. Here, we report new magnetostratigraphic data from the Ediacaran Ouarzazate Group in the Anti-Atlas Mountains of Morocco, which have primary magnetizations supported by a positive conglomerate test and stratigraphically consistent directions within volcanic units across multiple localities. Comprehensive magnetostratigraphic sampling shows highly variable directions, consistent with a rapidly changing geomagnetic field along a longitudinally preferred band. High-precision geochronology constrains the geomagnetic variability to ~568 to 562 million years and suggests rates that are likely too rapid for true polar wander or plate tectonic interpretations. Comparison of igneous- and sedimentary-derived data, using a new statistical approach combining Bingham and Fisher distributions, indicates a high-inclination paleomagnetic direction that is compatible with independent evidence for regional glaciation. Our analysis produces a late Ediacaran paleogeographic reconstruction that is consistent with paleomagnetic and geologic constraints.