Widespread Neogene remagnetization in Jurassic limestones of the South-Iberian palaeomargin (Western Betics, Gibraltar Arc)

Abstract

Palaeomagnetic investigations in Upper Jurassic carbonate rocks from the Western Subbetics (Betic Cordillera, Southern Spain) testify to a widespread Neogene remagnetization. Progressive thermal and alternating field demagnetization analyses reveal the presence of two stable components of the natural remanent magnetization (NRM). The NRM is dominated by a pervasive Neogene overprint, which always shows normal polarity and maximum unblocking temperatures of 450°C throughout the whole region studied. The primary Jurassic component, however, can also be isolated in many outcrops. This component has low intensity values and maximum unblocking temperatures of about 550°C, showing both normal and reversed polarities. Palaeomagnetic and rock magnetic analyses indicate that both primary Jurassic and secondary Neogene components are carried by magnetite. The incremental fold test performed in all sampling localities demonstrates that the remagnetization occurred during some stage of the Neogene deformation of the Subbetics, being pre-, syn- or post-folding in the various folds studied.