Rheological and topographic implications of thermal insulation created by supercontinents

Author(s)

Silva, Joao Pedro Macedo ; Sacek, Victor ; Ganade, Carlos Eduardo ; Manatschal, Gianreto

• Document type: Journal article
• Source: Earth and Planetary Science Letters; v. 652, p. 12-pg., 2025-01-08.

Abstract

Thick continental lithosphere represents a thermal insulator, promoting less efficient conductive heat transfer to the surface. As a consequence, the mantle temperature under supercontinents can increase relative to surrounding regions. Conversely, hot asthenospheric mantle can modify the thermal and rheological structure of the base of the lithosphere. The understanding of how the lithosphere and asthenosphere co-evolve considering lateral variable lithospheric thickness depends on the appropriate representation of the mechanical properties of the upper mantle in the geological time scale. Using thermo-mechanical numerical scenarios, we investigate how thick continental lithosphere, here referred to as cratonic keel, can affect heat flow to the surface, the convective pattern inside the asthenospheric mantle and the impacts of thermal evolution of a cratonic keel over time scales of hundreds of millions of years. We considered different lateral positions for the cratonic keel and relative movement between lithosphere and the base of upper mantle to emulate lateral movement over geological time. The numerical results indicate that the thermal insulation promoted by the thick continental lithosphere induces the development of positive thermal anomalies in the asthenosphere, which eventually induce the weakening of the base of the continental lithosphere. The heating of the sublithospheric mantle under cratonic keels is only relevant when the continental lithosphere presents low relative velocity with respect to the base of the upper mantle. Additionally, the presence of a mobile belt with lower effective viscosity than the surrounding cratonic lithosphere contributes to basal erosion due to thermal insulation and upwelling divergent flow in the asthenosphere, inducing the weakening of the continental lithosphere between cratonic blocks. Our results help the understanding of how thermal insulation can affect the evolution of cratonic keels and invite us to revisit natural examples to test the current interpretations of the unconformities present in intracratonic basins that are commonly explained by tectonic and/or dynamic processes. (AU)

• FAPESP's process: 21/06670-4 - From breakup to continental collision: Influence of rifted margins on the dynamics of collisional orogens through time
• Grantee: João Pedro Macedo Silva
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 23/08679-4 - From breakup to continental collision: influence of rifted margins on the dynamics of colisional orogens through time
• Grantee: João Pedro Macedo Silva
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate