Some like moving mountains, but we prefer moving continents, oceans, and even the entire silicate Earth

1 March, 2023

In a new EDRG-led Earth-Science Reviews paper, we publish the first data-rich full-plate global evolution history for the 2000–540 Ma interval, and utilise palaeomagnetic true polar wander (TPW) and global plume records to determine likely palaeolongitude for past reconstructions and the dynamic evolution of first-order mantle structures.

Establishing how tectonic plates have moved since deep time is essential for understanding how Earth’s geodynamic system has evolved and operates, thus answering longstanding questions such as what “drives” plate tectonics. Such knowledge is a key component of Earth System science, and has implications for wide ranging fields from core-mantle-crust interaction and evolution, geotectonic phenomena such as mountain building and magmatic and basin histories, the episodic formation and preservation of Earth resources, to global sea-level changes, climatic evolution, atmospheric oxygenation, and even the evolution of life.

In this work, we took advantage of the rapidly improving database and conceptual breakthroughs regarding the presence of a supercontinent cycle and possible dynamic coupling between the supercontinent cycle and mantle dynamics, and established a full-plate global reconstruction from 540 Ma back to 2000 Ma. We utilise a variety of global geotectonic databases to constrain our reconstruction, and use palaeomagnetically recorded true polar wander events and global plume records to help evaluate competing geodynamic models and provide new constraints on the absolute longitude of continents and supercontinents.

A revised reconstruction of Nuna using both geological and kinematic constraints, and by matching palaeomagnetic poles with the common APWP for the core continents. The Euler rotations for the reconstruction are given in Table 5. Lambert Equal Area Azimuthal projection with map centre at (15°N, 00°E) following the 1400 Ma reconstruction. Geotectonic features of 2000—1200 Ma are highlighted. Ant. = Antarctica; SAC = South Australian craton; WAC = West Australian craton; NAC = North Australian craton; Cath. = Cathaysia, South China; S.F. = São Francisco.

A revised Rodinia reconstruction based on both geological connections and palaeomagnetism. The Euler rotations for the reconstruction are given in Table 5. Lambert Equal Area Azimuthal projection with map centre at (20°N, 90°E) following the 850 Ma reconstruction. Geotectonic features of 1200—700 Ma are highlighted. Ant. = Antarctica; SAC = South Australian craton; WAC = West Australian craton; NAC = North Australian craton; Cath. = Cathaysia, South China; S.F. = São Francisco.

After revising the configuration and life span of both supercontinents Nuna (1600–1300 Ma) and Rodinia (900–720 Ma), we present a 2000–540 Ma animation featuring the rapid assembly of large cratons and supercratons (or megacontinents) between 2000 Ma and 1800 Ma. This occurred after a billion years of dominance by small cratons, and kick-started the ensuing Nuna and Rodinia supercontinent cycles and the emergence of stable, hemisphere-scale (long-wavelength) degree-1/degree-2 mantle structures.

Global 2000—540 Ma full-plate animation following the extended-orthoversion principle, Scenario Ia (0–90W–0)

Global 2000—540 Ma full-plate animation following the extended-orthoversion principle, Scenario Ib (0–90E–0)

We further use the geodynamicly-defined type-1 and type-2 inertia interchange true polar wander (IITPW) events, which likely occurred during Nuna (type-1) and Rodinia (type-2) times as shown by the palaeomagnetic record, to argue that Nuna assembled at about the same longitude as the latest supercontinent Pangea (320–170 Ma), whereas Rodinia formed through introversion assembly over the legacy Nuna subduction girdle either ca. 90° to the west (our preferred model) or to the east before the migrated subduction girdle surrounding it generated its own degree-2 mantle structure.

Schematic mantle convection patterns in relation to evolving tectonic systems from the Archaean time (after Li and Zhong, 2009; Zhong et al., 2007). (a) Archaean time with many cratons and smaller-scale convection cells. (b) The occurrence of multiple supercratons during Archaean–Paleoproterozoic time, featuring reduced number and larger mantle convection cells. (c) The start of the supercontinent cycle since the Paleoproterozoic, featuring supercontinent assembly over a mantle superdownwelling. (d) Circum-supercontinent subduction girdle eventually turns the sub-supercontinent superdownwelling as in (c) into a superupwelling (also called superplume, which includes the lower-mantle seismic LLSVP, not explicitly shown here), which triggers the break-up of the supercontinent. (d)-(e) If the axis of Earth’s minimum moment of inertia (Imin), the long axis of a prolate geoid defined by the two antipodal superupwellings (superplumes), does not intersect the equator, Earth’s spinning force would cause the entire silicate Earth to rotate as a true polar wander (TPW) event of up to 90° (d), bringing Imin (along with the antipodal superupwelling and the breaking-up supercontinent) onto the equator (Evans, 2003; Li et al., 2004) (e). Once at the equator, oscillating inertial interchange true polar wander (IITPW) may then occur around Imin (Evans, 1998; Kirschvink et al., 1997) (e). (f) A conceptual model of a circum-supercontinent subduction girdle producing two antipodal LLSVPs, with the supercontinent eventually breaks apart largely driven by the sub-supercontinent superupwelling (Li et al., 2008a; Li and Zhong, 2009). See 6.3 for further discussion. The small grey cartoon Earth models in (a) and (b) isare from Bleeker (2003). Note that LLSVPs in the lower mantle are not exclipitly shown in cartoons (a)-(e).

Two scenarios of IITPW occurring during the supercontinent cycle driven by the reorganization of mantle structure (a-c), likely examples of Type-1 IITPW during Nuna time (d) and Pangaea time (f, modified after Steinberger and Torsvik, 2008), example of Type-2 IITPW during Rodinia time (e), and (f-g) a possible normal TPW event during Pangaea time between 340 Ma and 270 Ma (g, modified after Merdith et al., 2021) followed by episodes of Type-1 IITPW events between 250 and 100 Ma (Steinberger and Torsvik, 2008). The rotating outline of Nuna and Rodinia are marked with ages in (d) and (e), respectively (note that the assembly of Nuna was not yet completed but was close at 1700 Ma), with arrows indicating TPW events.

Cartoons illustrating the implications of two alternative scenarios based on the extended-orthoversion geodynamic assumption where a 90° longitudinal change occurs between supercontinents and associated mantle structures (e.g., LLSVPs, and the Imins as defined by the two antipodal LLSVPs). (a-h) Scenario Ia where Nuna is centred at 0°E, Rodinia at 90°W, and Pangaea at 0°E (0–90 W-0). (i-p) Scenario Ib where Nuna is centred at 180°E, Rodinia at 90°E, and Pangaea at 0°E (0–90E-0).

Our interpretation is broadly consistent with the global LIP record. Using TPW and LIP observations and geodynamic model predictions, we further argue that the Phanerozoic supercontinent Pangaea assembled through extroversion on a legacy Rodinia subduction girdle with a geographic centre at around 0°E longitude before the formation of its own degree-2 mantle structure from 250 Ma, the legacy of which is still present in present-day mantle.

Contact person: Prof Zheng-Xiang Li & Dr Yebo Liu, Earth Dynamics Research Group, Curtin University.

Relevant publication:

Li, Z.X., Liu, Y., Ernst, R., 2023. A dynamic 2000—540 Ma Earth history: From cratonic amalgamation to the age of supercontinent cycle. Earth-Science Reviews, 238, 104336. https://doi.org/10.1016/j.earscirev.2023.104336