DECIPHERING THE PALEOMAGNETIC CONSTRAINTS ON LAURENTIA'S NEOPROTEROZOIC TECTONIC EVOLUTION (Invited Presentation)

The Neoproterozoic-Cambrian tectonics associated with supercontinent fragmentation has been proposed as an important control on global climate perturbations, atmospheric oxygen fluctuations, and marine chemical perturbations, and biological radiations. However, supercontinent paleogeography and dynamics of continental separation around its centerpiece, Laurentia, remain poorly constrained. Paleomagnetism provides a quantitative tool to determine ancient paleogeography and quantify variations in plate motions. As the field of paleomagnetism has matured, the number of studies has increased, and it has become apparent that not all data are equally reliable. Fortunately, concurrent progress has been made in data acquisition techniques and analysis methods. Accordingly, paleomagnetism provides valuable datasets that can independently evaluate paleogeographic hypotheses formulated from geochronologic and geologic datasets and illuminate innovative possibilities. In this talk, my goal is to demystify paleomagnetic reconstructions by highlighting advances that can help clarify uncertainties and enhance paleogeographic interpretations. First, I will discuss advances within the paleomagnetic community, including refined reliability criteria, statistical analytical methods, and considerations for presenting and dealing with uncertainty. Second, I will introduce a compilation of existing datasets from Laurentia, including new paleomagnetic data from the late Tonian Chuar Group in the Grand Canyon, Arizona. These datasets are incorporated with recent high-precision geochronological data to present a new Laurentian apparent polar wander path. Comparison of this Laurentian apparent polar wander path with paleomagnetic database of other cratons allows for more quantitative evaluation of proposed global paleogeography and Neoproterozoic supercontinent configurations. These reconstructions are consistent with Australia located near the present southern margin of Laurentia, but also highlight key issues that require greater investigation. Future evaluations of Neoproterozoic global connections require a continued combination of geologic, geochronologic and paleomagnetic scrutiny.