Quantifying finite strain in the poly-deformed Lansdowne Klippe, Garhwal Himalaya, India: An appraisal of popular strain estimation techniques

Abstract

Understanding finite strain in poly-deformed terranes remains a challenge due to multiple deformation phases, impacting accurate estimation. This study presents a comparative analysis of four distinct techniques (Rf/Φ, Fry's, Panozzo, and AMS-based strain estimation) to estimate the finite strain in the Lansdowne Klippe of the Garhwal Himalaya, India. In the estimation of strain, complexities might arise due to the inherent difficulties in assessing the original shape of strain indicators in areas with a history of multiple deformations. Such challenges significantly affect the precision of finite strain estimation, leading to inconsistencies in the obtained values. By analysing the quantitative and qualitative differences among the methodologies, this study reveals the discrepancies in determining 2-D finite strain and respective strain ellipses. The present attempt is the first rigorous multi-method comparison for quantifying strain within a poly-deformed klippe in the Himalayan orogen. In our comparative analysis, Rf/Φ and Fry methods yielded the highest finite strains (Rs ∼1.7–2.3), whereas the Panozzo method gave lower values (Rs ∼1.1–2.0). AMS-derived anisotropy (Pj ∼1.05–1.2) corresponds to only low finite strain. These systematic method-dependent differences underscore that strain magnitudes in a polyphase terrane are strongly influenced by the chosen technique. Our findings also highlight the inherent inconsistencies and limitations in estimating finite strain in regions with polyphase deformation.