SILICICLASTIC PRELUDE TO DEGLACIATION OF MARINOAN SNOWBALL EARTH: MAGNETOSTRATIGRAPHY OF THE ELATINA-NUCCALEENA-BRACHINA TRANSITION
We extend Sohl et al.'s magnetostratigraphy from this red sheet sandstone unit upward through Nuccaleena cap carbonate. High-resolution sampling at two sections (Elatina Creek and Trezona Bore) and moderate-resolution sampling at three more sections (Bunyeroo Creek, Enorama Creek GSSP, and Parachilna Gorge) suggests high dispersion of virtual geomagnetic poles in the topmost Elatina and lowest Nuccaleena interval. Most of Nuccaleena dolostone spans two ensuing polarity chrons, with generally low VGP dispersion but several centimeter-scale VGP departures. Multiple polarity zones characterize overlying, lowest Brachina siliciclastics. Collectively, these results appear to suggest that Marinoan cap carbonate records finescale structure of the earliest Ediacaran geomagnetic field, including excursions, reversal excursions, intervals of geomagnetic instability, and a high reversal frequency.