20 The Boring Billion was not so Boring! Mesoproterozoic Tectonics, Sedimentation, and Geochronology of Northwest Laurentia I

Thursday, 16 May 2024
8:00 AM - 12:00 PM
Cedar Ballroom

BELT-SIBERIA CONNECTION: MATCHING LIPS TIGHTEN PROTEROZOIC RODINIA RESTORATION AND MAY IMPLY A MULTIPOLAR GEOMAGNETIC FIELD

Paper number: 20-4
Program: Theme Sessions
Time: 8:45 AM – 9:05 AM

Authors

  • James Sears Presenting Author
    University of Montana, Missoula, MT

Abstract

The Belt Basin was abruptly truncated by a rift-transform system that broke up supercontinent Rodinia. In central Idaho, the breakup severed three pre- and syn-rift LIPs, establishing a unique assemblage of key piercing points for Rodinia restoration. The Belt LIPs pair with three LIPs at the NE promontory of the Siberian craton. The Siberian promontory neatly connects into the central Idaho re-entrant of west Laurentia's rift margin on the 3000 km-long east Siberia-west Laurentia (Verkhoyansk-Cordilleran) conjugate boundary proposed by Sears and Price (2003). The three pairs of LIPs crop out within a 200-km radius on the Siberia-Laurentia restoration. A) 1500-1470 Ma: Pre-rift diabase dikes and sills in the Belt Basin and its basement trend into correlative ones in Belt-aged basins and their basement in Siberia's Olenek and Anabar Plateaus. B) 1380 Ma: The pre-rift bimodal Shoup LIP in the Belt Basin adjoins the Chieriss dike of Siberia's Anabar Plateau. C) 534-529 Ma: The syn-rift Beaverhead alkalic trend in central Idaho's Belt basin adjoins Siberia's Olenek-Kharaulakh 550-526 Ma LIP, with bimodal diatremes, sills and flows. This last pair of LIPs dates the breakup unconformity for both the Siberian and Laurentian sides of the proposed connection. The breakup was followed by matching Cambrian through Devonian passive continental margin sequences.

The LIP connections augment a dozen pre-rift basement pin lines across the Verkhoyansk-Cordilleran conjugate boundary from Sette Daban-Death Valley to Taimyr-Yukon. The connection, however, is not permitted by a dipolar (GAD) interpretation of paleomagnetic data from the two cratons. Rather, it may imply a multipolar Proterozoic magnetic field.

Geological Society of America Abstracts with Programs. Vol. 56, No. 4

doi: 10.1130/abs/2024CD-397178

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