Tectonic signatures in the Triassic sediments of the Betic External Zone (southern Spain) as possible evidence of rifting related to the Pangaea breakup

Abstract

This paper describes various soft-sediment deformation structures present in the Triassic deposits of the Betic External Zone (Southern Iberian). These structures, together with variations in deposit thicknesses, internal angular unconformities, and synsedimentary faults, point to intense tectonic activity from the Middle to Late Triassic related to a stage of rifting. The Middle–Late Triassic in the Betic External Zone shows a sedimentary record represented by Muschelkalk and Keuper facies. In the Ladinian Muschelkalk, carbonates appear slumps, breccias, load casts, slide and parallel shear sur faces, and tsunamites. In the sandstones of the Carnian Keuper facies, different seismite beds and ball and pillow structures can be discerned. Above these deposits, the carbonate Zamoranos Formation of the Rhaetian displays volcaniclastic rocks with conglomerates, slumps and synsedimentary faults. All these features and magmatism suggest some tectonic activity, possibly related to the breakup of Pangaea, especially at the end Triassic. We highlight the features that indicate this tectonic activity over time and discuss the factors that triggered the development of these structures, along with the conditions that made this possible.