Re-computing palaeopoles for the effects of tectonic finite strain

Abstract

The pre-Messinian limestone cover (∼ 58–8 Ma) to the Troodos ophiolite (∼ 88 Ma) of southern Cyprus is penetratively strained as shown by ubiquitous magnetic fabrics and, in many sites, stylolitic cleavage. These define a gently N-dipping foliation and an N-plunging extension. South-vergent folding and thrusting is well known in very localized whereas the bulk of the strained limestone cover dips gently south, disturbed by faulting. The magnetic fabrics and stylolitic cleavage define the axes of finite strain in all sites studied, and the calcite matrix was suitably ductile to permit the original palaeomagnetic directions to be de-strained assuming continuum behaviour. The optimum de-straining (30–40% shortening in a flattening strain) is compatible with the stylolitic cleavage development, restores bedding to the near-horizontal, and restores the characteristic remanent magnetization vectors (ChRMs) to concentrated, symmetrical Fisherian distributions. The strain-corrected ChRMs yield more reasonable palaeopole locations for the Lefkara and Pakhna Limestone and more uniform micro-plate rotation rates. Corrected palaeopoles reveal a relatively uniform anticlockwise rotation of the Troodos plate since the creation of the late Cretaceous (∼ 88 Ma) ocean lithosphere. It did not accelerate during the deposition of the limestone cover as required by palaeopoles calculated from data not corrected for finite strain but turned at ∼ 1.5° Ma − 1 since ∼ 58 Ma.