Laurentia’s Grenville Loop: Tracking Rodinia across the Mesoproterozoic, Yiming Zhang - MagIC 3/1/23
Channel: Magnetics Information Consortium (MagIC)
Date: 2023-03-15

"New perspectives on Laurentia’s Laurentia’s Grenville Loop: Tracking Rodinia across the Mesoproterozoic to Neoproterozoic Boundary" by Yiming Zhang, University of California, Berkeley

Talk presented at the 2023 Magnetics Information Consortium (MagIC) Workshop: Magnetism and Earth History: Field Evolution, Environmental Change and Paleogeography, Feb 28th-Mar 2nd, 2023. Convened at the Scripps Institute of Oceanography, UCSD in La Jolla, California and sponsored by the National Science Foundation (NSF).

Workshop website: https://earthref.org/events/MAGIC/2023/

Talk Abstract:
The paleogeography of Laurentia throughout the Neoproterozoic is critical for reconstructing global paleogeography due to its central position in the supercontinent Rodinia. We develop a new paleomagnetic pole from red siltstones of the early Neoproterozoic Jacobsville Formation which is now constrained to be ca. 990 Ma in age. High-resolution thermal demagnetization experiments resolve detrital remanent magnetization. These remanence directions held by hematite pass an intraclast conglomerate test, giving confidence that the magnetization is detrital and primary. An inclination-corrected mean pole paleomagnetic position for the Jacobsville Formation confirms continued plate motion of Laurentia across the equator in the late Mesoproterozoic to early Neoproterozoic. Laurentia’s motion slowed down significantly following the onset of the Grenvillian orogeny. The distinct position of this well-dated pole from those acquired during exhumation and cooling in the Grenville Province that have been assigned a similar age indicates that the ages of the Grenville poles need to be revised to be younger. We use inverted cooling history models based on new apatite U-Pb ID-TIMS thermochronological data to obtain quantitative estimates on the cooling rate and timing of magnetic remanence acquisition for the Adirondack Highlands of the Grenville Province.