Matching mid-to-latest Carboniferous pole paths for eastern Australia and northern Armorica indicate a Pangea-B configuration and a latest Visean-Serpukhovian IITPW event
Authors: Klootwijk Chris 
Published: February 2023

A long and detailed pole path has been defined from Carboniferous ignimbritic successions across the Tamworth Belt forearc basin of a continental arc in the southern New England Orogen (SNEO) of eastern Australia. Stratigraphic successions spanning about 50 myr (~353 Ma to ~306 Ma) have been studied paleomagnetically over four decades, covering some &#160;400 sites and 4500 samples. The Carboniferous SNEO pole path is thought representative for Australia and Gondwana. Its prominent south-over-east-to-north loop with mid Carboniferous apex differs fundamentally from conventional Australian and Gondwanan Carboniferous pole paths featuring south-over-west-to-north loops. The eastern loop of the SNEO path is supported by poles from other workers on the Tamworth Belt. The western loop of conventional paths may reflect unrecognised overprinting and alternative polarity interpretation. Mid-to-latest Carboniferous segments of the SNEO (south) pole path and of a Carboniferous-to-Permian pole path for the northern Variscan massifs of Armorica (AR), defined by Edel (Strasbourg) and co-workers and converted to south poles, are comparable in shape and length, each spanning more than a hundred degrees of arc. Euler pole matching of the two mid-to-latest Carboniferous segments, taken as representative for Gondwana (SNEO) and tentatively so for Laurussia (AR), locates Armorica off northwestern Gondwana, and with it Laurussia, in a Pangea-B configuration. The two mid-to-latest-Carboniferous segments are each bounded by prominent mid Carboniferous and latest Carboniferous-early Permian loops, likely reflecting global tectonic events, dating the Pangea-B configuration as lasting from the Sudetic phase to the Asturian phase of the Variscan Orogeny, with transformation to Pangea-A likely starting therefrom. Such a Pangean evolution offers new insights into location of a northern Gondwanan Armorican Spur, into heating-up of Pangean lithosphere as a cause for the late Carboniferous Hercynian Unconformity, and into latest Carboniferous-to-late Permian transformation of Pangea-B-to Pangea-A as a common driver for contemporaneous oroclinal deformation of the, Gondwanan-antipodal, Ibero-Armorican Arc and SNEO and also as a cause for early Permian Pangea-wide extension. Global movements described by the Carboniferous SNEO pole path and by the matching SNEO and AR mid-to-latest Carboniferous pole path segments suggest causality between a Visean northern excursion of Gondwana that likely disturbed the earth&#8217;s moment-of-inertia, a latest Visean-Serpukhovian Inertial Interchange True Polar Wander (IITPW) event that likely led to latest Visean-Serpukhovian onset of continental glaciation consolidating the Late Paleozoic Ice Age and to the Serpukhovian biodiversity crisis, and the Bashkirian start of the Permo-Carboniferous Reverse Superchron (PCRS) that may have eventuated from changes in heat flow across the core-mantle boundary brought on by IITPW repositioning of the Large Low Shear-wave Velocity Provinces and Ultra-Low Velocity Zones. Such a Variscan-IITPW-PCRS causal chain would constitute an order of magnitude faster (107 yr) top-down feedback between plate tectonics and the geodynamo than could be effectuated through mantle turnover.