Thermotectonics of the Calabrian Arc, Southern Italy constraints from fission track analysis

Abstract

This study uses fission track analysis to provide temperature and time constraints on the cooling and exhumation history of the basement rocks of the Calabrian Arc of southern Italy. Fission track analysis also provides information on the provenance and burial history of the terrigenous Oligo-Miocene Stilo-Capo d 'Orlando Formation.65 samples from the basement rocks have yielded 57 apatite fission track ages, 54 zircon fission track ages and 25 apatite track length distributions. 9 samples from the Stilo-Capo d 'Orlando Formation have yielded 8 apatite fission track ages, 8 zircon fission track ages and 6 apatite track length distributions.Qualitative and quantitative analysis of the fission track data reveals that the majority of the basement rocks underwent a phase of increased cooling related to exhumation between about 35 Ma (Early Oligocene) and 15 Ma (Middle Miocene). Evidence from the local sedimentary record indicates that erosion played an important role in the exhumation process. Extensional tectonism also contributes to some of the increased exhumation. Analysis of the fission track results obtained from the Stilo-Capo d 'OrlandoFormation confirm a Calabrian basement provenance for the sediments. The previously debated origin of volcanic conglomerate clasts from the formation is also resolved. Finally apatite fission track analysis indicates post-depositional burial at the base of the formation to temperatures greater than 80*C.The final part of this thesis uses the fission track age and temperature constraints to produce an improved tectonic model for the Oligo-Miocene tectonic evolution of the Calabrian Arc. This model proposes that increased exhumation is a consequence of the dynamics of an overthickened orogenic wedge. The model is related to the overall plate dynamics of the western Mediterranean orogeny. Ill A CKNO W LED G EM ENTSThis project was supervised by Dr. Robert Hall, who has provided much advice and encouragement, when not away in the field, and whose valuable criticisms of the initial drafts of this thesis were much appreciated. I must also thank Professor Claudio Vita-Finzi, who proposed southern Italy as the field area after problems developed with the original project proposal. Finally, I am greatly indebted to Dr. Tony Hurford for allowing the use of the facilities of the London Fission Track Research Group. Funding for this project was provided by the Natural Environment Research Council. Financial assistance from the London Fission Track Research Group and Eurotrack was also greatly received.Samples were collected from throughout Calabria and Sicily, and special recommendation must go to Le Pensione Sirene, in Scilla. Assistance and company in the field from Bill Murphy, Dr. Robert Hall, Professor Claudio and Penelope Vita-Finzi and Mark Ferry was invaluable. Also, thanks to Gert Jan Weltje for a valuable discussion in the field, and for providing a pre-print of his work on the Stilo-Capo d 'Orlando Formation.Finally thanks to the FIAT garage at Villa san Giovanni for keeping the...