Late Miocene uplift in the Romagnan Apennines and the detachment of subducted lithosphere

We report part of a test of the hypothesis that detachment of subducted lit hosphere may be a process of lateral propagation of a horizontal tear [Wort el and Spakman, Proc. Ken. Ned. Akad. Wetensch., 95 (1992) 325-347]. We hav e used the Apennines as a test area. The test procedure consists of the com parison of hypothetical vertical motions, predicted from the expected redis tribution of slab pull forces, with observed vertical motions. We demonstra te that a Late Miocene depocentre migration from the Northern towards the C entral Apennines is associated with uplift of (the fore-are of) the Norther n Apennines. Such a combination of a depocentre shift and uplift is thought to be diagnostic for lateral migration of slab detachment. The depocentre migration was identified in earlier work [van der Meulen et al., Earth Planet, Sci. Lett., 154 (1998) 203-219]. This contribution focus es on uplift, which has primarily been identified through the geohistory an alysis of the Monte del Casino Section (Romagnan Apennines, Northern Italy) . Owing to methodological problems, the start and duration of the uplift ph ase could not be constrained: and only a minimum estimate of the total amou nt of uplift (483 +/- 180 m) is obtained. The data do allow for an estimate of the uplift rate: 163 +/- 61 cm/ky. A review of regional data results in better constraints on the timing of the above lateral reorganisation of th e fore-are, and on the spatial extent of the uplifted area. Depocentre deve lopment in the Central Apennines began between 8.6 and 8.3 Ma B.P. Uplift s tarted between 9 and 8 Ma B.P., and affected the entire northernmost Apenni nes. (C) 1999 Elsevier Science B.V. All rights reserved.