Continental collision and lateral escape deformation in the lower and upper crust: An example from Caledonide Svalbard

Abstract

Ductile Caledonian structures of eastern Svalbard and the pattern of brittle deformation in eastern Anatolia are examined in an attempt to understand the different mechanical responses of the upper and the lower crust in collision and lateral escape systems. In Svalbard, Early to Middle Proterozoic basement structures were reworked under amphibolite facies conditions, in Late Silurian time, during the Caledonian orogeny when synmetamorphic ductile to postmetamorphic brittle, left‐lateral shearing was concentrated in narrow zones. The widespread distribution of contractional and elongation structures over the northern and northeastern Svalbard indicates that this deformation was the result of E–W convergence and N–S lateral escape of the whole continental mass along an array of deep crustal shear zones. The combination of vertical shear zones with parallel low‐angle compressional shear zones and associated folds in Ny Friesland represents the ductile or plastic flow response of the lower crust to the orthogonal‐lateral escape setting. The westward escape of the Anatolian block, accompanying the active Arabia‐Eurasia collision, is associated with a 150 km wide zone of thrust faulting and NE–SW sinistral strike‐slip faults along the East Anatolian Fault Zone. Arrays of dextral and sinistral strike‐slip faults with thrust and normal faults between the Eastern Anatolian and the North Anatolian Fault Zones represent an elastic response of the upper crust that is considered to be the superficial equivalent of the ductile flow in the lower crust of Caledonide Svalbard in a convergence‐lateral escape setting.