A new structural and kinematic framework for the Alborán Domain (Betic–Rif arc, western Mediterranean orogenic system)

Abstract

The processes that drastically thinned and rapidly exhumed the Alborán Domain in southern Spain are poorly understood. Geological maps, cross-sections and a synthesis of previous work in the Alpujárride Complex provide a new structural framework for the Alborán Domain, with major revision of the previously defined lithotectonic units. Alborán continental lithosphere was buried and thickened in the Paleogene (D 1 ) and subsequently thinned during late-orogenic extension in the early Miocene. Regional patterns of stretching lineations and late recumbent folds record important spatiotemporal changes in the kinematics of extension. East-directed shear (D 2 ) is preserved in deep orogenic levels and thinned the crustal sequence during rapid exhumation and high-temperature metamorphism. North-directed shear (D 3 /D 4 ) is preserved in upper orogenic levels and reworked earlier structures during the later stages of exhumation and cooling. This large-scale switch in the direction of finite stretching resulted from the interaction between components of orogen-parallel (D 2 ) and orogen-perpendicular (D 3 /D 4 ) extension, and associated vertical and lateral gradients in strain. We provide a novel kinematic model for gravity-driven extensional collapse of the Alborán Domain, compatible with both westward motion of the Alborán Domain relative to the Iberian margin and subsequent northward extensional flow and emplacement of Alborán lithosphere onto the Iberian margin. Supplementary material: A list of sample names, coordinates and descriptions, plus a Google Earth .kmz file of sample locations is available at https://doi.org/10.6084/m9.figshare.5508643 . A geological sketch map of the Sierra de las Estancias, indicating the trend of stretching lineations in the Alpujárride Complex and location of major geological boundaries is available at https://doi.org/10.6084/m9.figshare.5513398 .