Effects Of Subduction History On Mantle Convection: Implications For True Polar Wander And Dynamic Topography

The movement of Earth’s tectonic plates is a fundamental input for countless studies in Earth science, including global atmospheric and oceanic circulation, sedimentation and erosion, maturation and location of fossil fuels, and the dynamics of Earth’s deep interior. However, the uncertainty of plate tectonic reconstructions increases rapidly backwards in time. In particular, the circum-Pacific region reaches nearly 60% uncertainty by the Mesozoic (~150 Ma). The primary source of this uncertainty is the subduction of oceanic crust into the mantle along convergent margins; this process of recycling Earth materials destroys the geological data used to reconstruct plate history. To reconcile the long-debated subduction history of the circum-Pacific, this study implements two contrasted plate reconstruction models as boundary conditions for mantle convection models and compares predictions of True Polar Wander (TPW), the geoid, and dynamic topography to observations. We explicitly calculate past mantle states using TERRA forward global geodynamic models that assimilate two different global plate reconstructions: a widely used model we call ‘Earthbyte’ and a recently developed ‘Tomopac’ model that has more circum-Pacific intra-oceanic subduction. For TPW alternative subduction histories produce significant differences (70°+) in modeled TPW that are comparable to changes in assumed mantle viscosities. Tomopac improves the fit between geodynamically modeled and paleomagnetically estimated TPW between 100 Ma to present and best reproduces an abrupt ~50 Ma TPW path change from paleomagnetic data. Our results show that Earth’s subduction history and lower mantle radial viscosity are primary controls on Earth’s TPW history. We find that mantle viscosity and excess ellipticity may enhance or dampen TPW but not to the extent hypothesized for a ’stable Earth’ since the Late Cretaceous. For dynamic topography we show its dependence on deep-time subduction history. The inclusion of intra-oceanic subduction within the Pacific basin improves the fit to the geoid by >20% and observed oceanic residual topography by >37%. Regional changes in subduction history illicit global changes in model predictions.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Geophysics

Grantor

University of Houston

Year dc:date.issued

2024

Author dc:creator

• Calvelage, Christopher M

Advisor dc:contributor.advisor

• Zheng, Yingcai

Committee members dc:contributor.committeemember

• Wu, Jonny
• Colli, Lorenzo
• Suppe, John
• Sager, William

• Mantle Convection
• True Polar Wander
• Dynamic Topography

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10657/17743

OAI identifier oai:identifier

oai:uh-ir.tdl.org:10657/17743