Origins and significance of rocks in an imbricate thrust zone beneath the Pindos ophiolite, northwestern Greece

Abstract

Summary Major zones of imbrication under the Pindos ophiolite of northwestern Greece relate to the formation of frontal and oblique ramp structures. These are marked by a northwest-trending line of tectonic windows in the ophiolite and a northeast-trending anticlinal structure which folds thrust contacts. The simplified structural sequence from top to bottom is: (1) Ophiolite lithologies, mainly pillow basalts and basal serpentinite; (2) Metabasites and meta-sediments of the ophiolite dynamothermal aureole ranging up to lower amphibolite facies; (3) A complex sequence of basalt, gabbro, pelagic sediments, olistostromes, debris flows and breccias interpreted as a sea floor sequence (the Perivoli Complex); (4) Early Cretaceous calcareous flyschoid sediments; and (5) Tertiary Pindos Flysch and melange. All the greenschist facies and the higher grade metamorphic rocks are interpreted as part of the metamorphic aureole and not as Palaeozoic basement. The generalized sequence of major deformational episodes is: (A) Thrusting within the sea floor with concurrent metamorphism causing polyphase deformation and juxtaposition of the ophiolite, the dynamothermal aureole and the Perivoli Complex. (B) The main imbrication along NNW-trending, E-dipping planes, involving all the lithologies and associated with the formation of major frontal and oblique ramp structures. (A) occurred during the Middle Jurassic ‘displacement’ of the ophiolite sheet. ‘Emplacement’-related deformation may have occurred in (1), (2) and (3), but is difficult to isolate due to the intensity of episode (B) which occurred during westward overthrusting in the Late-Tertiary and may have been related to an E-dipping subduction zone.