TECTONOPHYSICAL PALEOSTRESS RECONSTRUCTIONS: INTERPRETATION CHALLENGES AND POSSIBLE SOLUTIONS
Yu.L. Rebetsky, A.V. Marinin,
and L.A. Sim
О.Yu. Schmidt United Institute of the Physics of the Earth, Russian Academy of Sciences, ul. Bol’shaya Gruzinskaya 10, Moscow, 123995, Russia
Keywords: Slickensides, stress, tectonophysics, shear, fold, deformation phase, paleostress
Abstract
Paleostress inversion may be
ambiguous when several markedly different local stress states are inferred for
a group of outcrops. Attempts of reconstructing regional stress regimes
(compressional, extensional, or strike-slip) by selecting local principal
stresses of proximal directions turn out to have poor grounds. Each stress
permutation (e.g., extension to compression) attendant with buildup of large
irreversible strain (fault slip) requires a 5–6 kbar change in middle-crust
horizontal stress and at least 50 Myr stable and uniform loading.
Tectonophysical stress reconstructions for present active intracontinental
orogens show heterogeneous patterns: Stress directions in uplifts are different
from those in large intermontane basins and even in relatively subsided parts
of mountain ranges or in adjacent uplifted zones (e.g., a plateau and a range).
Paleostresses should be interpreted with reference to present stress fields in
the respective areas. It is suggested to reconstruct regional stresses using
the approach of L. Sim implying search for “common stress fields”. Another
important technique is to trace stress changes in specific structures (large
folds etc.) in the course of their evolution. The available data indicate
correlation and bipolarity of stress states in large basins and uplifts.
DOI: 10.15372/RGG2019048
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