INSIGHTS ON THE THERMAL EVOLUTION OF THE LIGURIAN APENNINES (ITALY) THROUGH FISSION-TRACK ANALYSIS

Apatite fission-track analysis has been applied on 24 samples from the geometrically upper units (Internal and External Ligurids) of the Nor thern Apennines nappe pile. They yield ages between c. 20 Ma and c. 6 Ma. Two samples were also dated with fission tracks in zircon (ages of c. 155 Ma and c. 199 Ma). Together the data reveal that during post-l ate Cretaceous compression the Internal Ligurids reached temperatures to completely anneal fission tracks in apatite (T > c. 120 degrees C) but not in zircon (T < c. 300 degrees C). After Eocene continental col lision these rocks were cooled (below c. 120 degrees C) and stal ted a gain to retain fission tracks in apatite. Since the Oligocene a furthe r burial under episutural sediments ensued that caused a partial to to tal apatite fission-track annealing. During a final phase of exhumatio n the sedimentary cover was removed. This exhumation can be linked to Late Miocene extensional tectonics, that started at c. 8-9 Ma in the c entral and southern portions of the study area.