Reconstructing orogenic exhumation histories using synorogenic detrital zircons and apatites: an example from the Betic Cordillera, SE Spain
Fission track thermogeochronology using detrital apatite and zircon from a synorogenic foreland basin on the northern margin of the Betic Cordillera Internal Zone is used to reconstruct the cooling and unroofing history of the sediment source areas in the Oligo- Miocene mountain belt. Previously, a heavy mineral study on the same sedimentary rocks showed that progressively deeper tectonometamorphic units were being unroofed during the latest Oligocene to middle Miocene at a minimum rate of 3 km Myr−1. The fission track data have further constrained the exhumation history showing that the structurally highest (i.e. shallowest) parts of the mountain belt (Malaguide Complex) cooled relatively slowly during the atest Oligocene–Aquitanian, while the deeper metamorphic units (Alpujarride Complex) cooled at much higher rates (up to 300 °C Myr−1) during the Burdigalian–Langhian. These fast cooling rates from synorogenic detritus are consistent with cooling rates calculated previously for the deeper parts of the early Miocene orogenic belt, using 39Ar–40Ar dating of muscovite, biotite and amphibole from basement metamorphic rocks. Rapid cooling in the early Miocene, which commenced at#21 Ma, is attributed to the change in process from erosional to tectonic denudation by orogen-scale extension within the eastern Betic Cordillera.