Deep mantle structure as a reference frame for movements in and on the Earth

Area of Science:

• Geophysics
• Plate Tectonics
• Earth Sciences

Background:

• Earth's geoid is dominated by a degree-2 mode linked to deep mantle structures.
• Large low shear-wave velocity provinces (LLSVPs) beneath Africa and the Pacific influence surface geology.
• Previous models lacked robust absolute plate motion reconstructions for early geological eras.

Purpose of the Study:

• To develop a model for absolute plate motion from the earliest Paleozoic (540 Ma) to the present.
• To investigate the long-term influence of deep mantle structures on plate tectonics.
• To test the hypothesis of a persistent degree-2 convection mode in Earth's mantle.

Main Methods:

• Correlating surface geological features (large igneous provinces, kimberlites) with core-mantle boundary structures.
• Utilizing a novel iterative approach for paleomagnetic reference frame determination, corrected for true polar wander.
• Reconstructing continental positions and plate motions over geological timescales.

Main Results:

• Identified six phases of slow, oscillatory true polar wander during the Paleozoic.
• Paleozoic true polar wander rates are comparable to Mesozoic rates, but absolute plate velocities were twice as high.
• Reconstructions show large igneous provinces and kimberlites originating from LLSVP margins, consistent with later geological periods.

Conclusions:

• A degree-2 convection mode in Earth's mantle may have operated throughout the entire Phanerozoic eon.
• Deep mantle structures significantly controlled plate motion and geological events over vast timescales.
• The study provides a geologically plausible kinematic model for early Earth history.