True Polar Wander: A Key Indicator for Plate Configuration and Mantle Convection During the Late Neoproterozoic

Abstract

Large polar motions are observed in the apparent polar wander paths of several continents during the Ediacaran. Among various hypotheses proposed in the literature, one consists of the occurrence of two successive fast and large true polar wander (TPW) episodes, from 615 to 590 Ma and then between 575 and 565 Ma. In this study, we explored the effect of the reactivation of a girdle of subduction to produce such TPW. First, we performed a reconstruction of the main continents between 615 and 520 Ma including Laurentia, Baltica, west and central Gondwana, and Australia‐Antarctica. We then implemented this paleogeography into a simple mantle dynamic model to calculate the TPW during the Ediacaran. Our results show that the reactivation of a girdle of subduction surrounding the continents along with a reduced effect of the return flow rising from the lower mantle can produce two TPW episodes consistent with the paleomagnetic observations. This mechanism is possible if the sinking velocities associated with the girdle of subduction drastically decrease between 635 and 730 Ma. Such a large geodynamic event is consistent with the detrital zircon age distribution of the Neoproterozoic supporting a low subduction activity during the Cryogenian and a boost during the Ediacaran. Decrease of subduction‐related stress induced on the lithosphere may have interrupted the rifting of the supercontinent Rodinia for 100 Ma. Finally, the weakening in subduction magmatism might have strongly reduced the CO2 flux into the atmosphere and played a major role in driving the Neoproterozoic global‐scale glaciations.

Pannotia: in defence of its existence and geodynamic significance

“…Global plate reconstruction models for the Neoproterozoic are poorly constrained because of the limited number of reliable palaeopoles and because of evidence of inferred episodes of true polar wander (e.g. Kirschvink et al, 1997;Evans, 2003;Li et al, 2004Li et al, , 2008Mitchell, 2014;Robert et al, 2018) and the possibility of an anomalous behavior of the geomagnetic field (e.g. Abrajevich and Van der Voo, 2010).…”

“…Nonetheless, palaeomagnetic data are permissive of its existence (e.g., Scotese, 2009;Scotese and Elling, 2017;Robert et al, 2018). It is questionable whether Pannotia would have fulfilled the criterion that a supercontinent should "consist of at least 75 % of the preserved continental crust prior to initial breakup" (Meert, 2012).…”

Testing the occurrence of Late Jurassic true polar wander using the La Negra volcanics of northern Chile

“…The orientation of the TPW axis and the rate and total amplitude of rotation are influenced by the viscosity of the mantle, the distribution of mantle mass anomalies, and the elastic thickness of the lithosphere (Tsai and Stevenson, 2007;Creveling et al, 2012;Greff-Lefftz and Besse, 2014;Chan et al, 2014). Inferences of past TPW have therefore been used to constrain the stability of deep mantle density structure and the occurrence of subduction and mantle plumes through time (Robert et al, 2018). At the same time, studies of paleoenvironments and sea-level records motivate robust determinations of TPW due to the potentially large associated shifts in latitude, local climate, and local sea-level with amplitudes of up to 100 m (Mound and Mitrovica, 1998;Mound et al, 1999;Muttoni and Kent, 2016).…”

Preliminary Appraisal of a Correlation Between Glaciations and Large Igneous Provinces Over the Past 720 Million Years

“…Paleomagnetic comparison demon strates that these three continents were contiguous ca. 615 Ma (Robert et al, 2018), supporting the interpreta tion of a shared CIMP LIP, until the opening of the Iapetus Ocean (Robert et al, 2018;Mitchell et al, 2011). The Ouarzazate group of Morocco includes both a SLIP f ollowed by a LIP (i.e., a pulse of silicic volcanism f ollowed by pulse of basaltic volcanism), both ca.…”