HR: 1340h
AN: U33A-0036    [Abstracts]
TI: Climate Catastrophe, True Polar Wander, and Inclination Shallowing in the Ediacaran Period
AU: * Raub, T D
EM: timothy.raub@yale.edu
AF: Yale University, Department of Geology and Geophysics, 210 Whitney Ave., New Haven, CT 06511
AU: Evans, D A
EM: dai.evans@yale.edu
AF: Yale University, Department of Geology and Geophysics, 210 Whitney Ave., New Haven, CT 06511
AB: Syntheses of global paleomagnetic data for the Ediacaran Period are difficult to reconcile with standard, uniformitarian plate-tectonic interpretations. Instead, they appear to support a substantial component of true polar wandering (TPW) contributing to each continent's apparent polar wander (APW) path. Construction of magnetostratigraphy-based APWP's has been undertaken in order to quantify the timing and magnitude of putative true polar wander events. If verified, large-scale, multi-episode TPW would establish a second axisymmetric reference frame, about Earth's equatorial minimum inertial axis, suitable for APWP superposition and longitude-controlled paleogeographic reconstruction. In addition to TPW, the terminal Proterozoic interval witnessed repeated episodes of low paleolatitude glaciation. High-resolution magnetostratigraphy of South Australia's Nuccaleena cap dolostone documents three correlatable geomagnetic reversals intimately associated with the solid cap facies. This implies a conservative estimate of 100's kyr duration for postglacial return to "normal" sedimentologic and ocean geochemical regimes. While confirming a low paleolatitude for Marinoan glacial deposits, paleomagnetic inclinations in the Nuccaleena cap dolostone are steeper than those from the underlying, glaciogenic Elatina Formation. Whether due to paleomagnetic compaction shallowing; to geomagnetic low-intensity or non-dipole field contributions; or to rapid APW, demonstration of similar behavior in correlative units across Australia could offer hope of resolving several paleogeographic and geodynamic enigmas that characterize the Ediacaran Period.
DE: 1500 GEOMAGNETISM AND PALEOMAGNETISM
DE: 1520 Magnetostratigraphy
DE: 1525 Paleomagnetism applied to tectonics (regional, global)
DE: 1532 Reference fields (regional, global)
DE: 1560 Time variations--secular and long term
SC: Union [U]
MN: 2004 AGU Fall Meeting