EDIACARAN PALEOMAGNETISM: REVIEW AND NEW DATA FROM BALTICA

All intervals of geologic time are filled with mysteries and enigmas but some offer more intrigue than others. The span of geologic time that stretches from the late Neoproterozoic through the Middle Cambrian (~800-501 Ma) heralded the evolution of complex bauplans and increased bioturbation; some of the most severe glacial episodes in Earth history; rapid changes in continental configurations; oxygenation of the atmosphere, shallow and deep oceans; unique swings in stable isotope ratios; and a host of other enigmatic geological, geophysical and astronomical events. This interval includes the Ediacaran Period (635-542 Ma), the Nemakit-Daldynian interval (542-535 Ma) and the so-called Cambrian explosion during the Tommotian-Botomian interval (535-513 Ma). Precise causes for this unique biological period in Earth history are unknown, but speculation about the rise of animals has run the gamut from purely intrinsic biological causes to extrinsic triggers or some combination of both. Tectonic events during this same time interval created the framework that “guided” the Phanerozoic development of the present-day globe.

It is intriguing that numerous and superficially disconnected phenomena seem to be interrelated at a profound level (Meert & Lieberman, 2008). There have been many attempts to provide a robust Ediacaran paleogeography and one important tool for accomplishing this goal is paleomagnetism. Paleomagnetic studies provide the only quantitative method from which the ancient spatial distribution of major landmasses can be established. Yet, it is precisely the Ediacaran time period where paleomagnetic data are the most controversial. The problems are particularly acute for Laurentia and Baltica where the paleomagnetic data are argued to support high or low latitude positions, rapid continental drift, rapid true polar wander, inertial interchange true polar wander and non-dipole fields depending on the perspective of the author. We review the paleomagnetic data from Baltica for this time interval and offer a glimpse of new paleomagnetic data from parautochthonous sedimentary sequences in the Ural mountains as a possible solution to part of the enigma.