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Durham University

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Publication details for Dr Nicola De Paola

Collettini, C., De Paola N. , Holdsworth, R.E. & Barchi, M.R. (2006). The development and behaviour of low angle normal faults during Cenozoic asymmetric extension in the Northern Apennines, Italy. Journal of Structural Geology 28: 333-352.

Author(s) from Durham

Abstract

Movements on low-angle normal faults (LANF) are not predicted by traditional Anderson–Byerlee frictional fault mechanics. Our
investigations centre on three normal fault systems active at distinct times during the regional extension of the Northern Apennines, with each
showing different degrees of crustal exhumation. These are (from E to W): the Altotiberina fault system, Umbria; the Radicofani fault
system, Tuscan mainland; and the Zuccale fault system, Isle of Elba. Regional extension has been a continuous process since middle
Miocene, migrating progressively from west to east, with deformation accommodated by a set of E to NE-dipping LANF and more steeply
SW-dipping antithetic structures. The LANF acted as regional detachments, accommodating a majority of the extension in the Northern
Apennines, with individual faults exhibiting several kilometres of displacement. Regionally, the stress field has been characterised by a
vertical s1 and a NE–SW- (Tuscan mainland and Umbria) to E–W (Elba)-trending s3. Where exposed at the surface, the main LANF
detachments possess a well-developed fault core of foliated fault rocks in which fluids have played a key role in weakening due to reaction
softening and the onset of stress-induced solution–precipitation mechanisms. We speculate that the E-dipping normal faults initiated with
relatively low-angles of dip due to differential drag generated by mantle flow following slab retreat and roll-back beneath the Apennine chain.