The onset of extension during lithospheric shortening

A two-dimensional thermomechanical model for lithospheric unrooting

Anna Maria Marotta*, Manel Fernàndez, Roberto Sabadini

*Corresponding author for this work

Research output: Contribution to journalArticle

26 Citations (Scopus)

Abstract

We model the evolution of the lithosphere during its shortening and consequent gravitational collapse with special emphasis on the induced variations in the surface stress regime and dynamic topography. In particular, we analyse the conditions leading, immediately after lithospheric failure, to local extension, eventually coeval with compression. Different crustal rheologies and kinematic conditions as well as thermally imposed mechanical rupture are considered. Numerical calculations have been performed by using a 2-D finite element code that couples the thermal and mechanical equations for a Newtonian rheology with a temperature-dependent viscosity. The results show that, after the failure of a gravitationally unstable lithospheric root, the replacement of lithospheric mantle by warmer asthenospheric material induces a considerable variation in the dynamic topography and in the surface stress regime. The occurrence of local extension, its intensity and its spatial distribution depend mainly on whether convergence continues throughout the process or ceases after or before the lithospheric failure. Similarly, uplift/subsidence and topographic inversion are controlled by kinematic conditions and crustal rheology. Mechanical rupture produces drastic changes in the surface stress regime and dynamic topography but only for a short time period, after which the system tends to evolve like a continuous model.

Original languageEnglish
Pages (from-to)98-114
Number of pages17
JournalGeophysical Journal International
Volume139
Issue number1
DOIs
Publication statusPublished - Oct 1999
Externally publishedYes

Keywords

  • Extension
  • Gravitational collapse
  • Lithospheric shortening
  • Topographic instability

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