[DLS] Nicholas Swanson-Hysell (UMN-Twin Cities)

“Rapid Mesoproterozoic Plate Motion Stalled by Collision and the Assembly of the Supercontinent Rodinia”

Lithosphere can move relative to a planet’s spin axis either through differential plate tectonic motion or through wholesale rotation along with the mantle — a process called true polar wander. True polar wander has been proposed to dominate over differential plate motion in some intervals of Earth history. One such interval is leading up to the Mesoproterozoic-Neoproterozoic boundary when abundant paleomagnetic poles with tight temporal constraints for the ancient core of North America (Laurentia) indicate rapid motion. One test for whether this motion from 1,110 to 1,080 million years ago was due to plate motion or true polar wander is whether Laurentia slowed at the onset of the collisional Grenvillian orogeny. New paleomagnetic data for Laurentia from 1,080 to 1,050 Ma and ca. 990 Ma show that Laurentia’s rate of motion dropped by an order of magnitude associated with collisional orogenesis. These results indicate that Laurentia’s rapid equatorward journey was the result of differential plate tectonic motion associated with the closure of the Unimos Ocean basin leading up to the assembly of the supercontinent Rodinia.

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