Review Article Kinematic constraints on buckling a lithospheric-scale orocline along the northern margin of Gondwana: A geologic synthesis A. Brandon Weil a, ⁎, G. Gutiérrez-Alonso b , S.T. Johnston c , D. Pastor-Galán b a Department of Geology, Bryn Mawr College, Bryn Mawr, PA 19010, USA b Departamento de Geología, Universidad de Salamanca, Plaza de los Caídos s/n, 37008 Salamanca, Spain c School of Earth & Ocean Sciences, University of Victoria, PO Box 3065 STN CSC, Victoria BC,Canada V8P 4B2 abstract article info Article history: Received 9 July 2012 Received in revised form 27 September 2012 Accepted 2 October 2012 Available online 12 October 2012 Keywords: Orocline Variscan Iberia Cantabria Delamination Paleomagnetism The Paleozoic Variscan orogeny was a large-scale collisional event involving amalgamation of multiple con- tinents and micro-continents. Existing data, suggests oroclinal buckling of an originally near-linear conver- gent margin during the last stages of Variscan deformation in the late Paleozoic. Closure of the Rheic Ocean resulted in E–W shortening (present-day coordinates) in the Carboniferous, producing a near linear N–S trending, east-verging belt. Subsequent N–S shortening near the Carb-Permian boundary resulted in oroclinal buckling. This late-stage orogenic event remains an enigmatic part of final Pangea amalgamation. The present-day arc curvature of the Variscan has inspired many tectonic models, with little agreement be- tween them. While there is general consensus that two separate phases of deformation occurred, various models consider that curvature was caused by: dextral transpression around a Gondwana indentor; strike-slip wrench tectonics; or a change in tectonic transport direction due to changing stress fields. More recent models explain the curvature as an orocline, with potentially two opposite-facing bends, caused by secondary rotations. Deciphering the kinematic history of curved orogens is difficult, and requires establish- ment of two deformation phases: an initial compressive phase that forms a relatively linear belt, and a second phase that causes vertical-axis rotation of the orogenic limbs. Historically the most robust technique to accu- rately quantify vertical axis-rotation in curved orogens is paleomagnetic analysis, but recently other types of data, including fracture, geochemical, petrologic, paleo-current and calcite twin data, have been used to cor- roborate secondary buckling. A review of existing and new Variscan data from Iberia is presented that argues for secondary buckling of an originally linear orogenic system. Together, these data constrain oroclinal buckling of the Cantabrian Orocline to have occurred in about 10 Ma during the latest Carboniferous, which agrees well with recent geodynamical models and structural data that relate oroclinal buckling with lithospheric delamination in the Variscan. © 2012 Elsevier B.V. All rights reserved. Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 2. Opening of the Rheic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3. Closing of the Rheic and the Variscan orogeny . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 4. Observations used for establishing secondary rotation of the Cantabrian Orocline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 4.1. Paleomagnetic data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 4.2. Structural data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 5. Oroclinal lithospheric delamination model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 6. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 Tectonophysics 582 (2013) 25–49 ⁎ Corresponding author. Fax: +1 610 526 5086. E-mail address: aweil@brynmawr.edu (A.B. Weil). 0040-1951/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.tecto.2012.10.006 Contents lists available at SciVerse ScienceDirect Tectonophysics journal homepage: www.elsevier.com/locate/tecto