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Authors: | Viola, Giulio* Torgensen, Espen* Mazzarini, Francesco* Musumeci, Giovanni* van der Lelij, Roelant* Schönenberger, Jasmin* Garofalo, Paolo Stefano* |
Title: | New Constraints on the Evolution of the Inner Northern Apennines by K-Ar Dating of Late Miocene-Early Pliocene Compression on the Island of Elba, Italy | Journal: | Tectonics | Series/Report no.: | /37 (2018) | Publisher: | Wiley | Issue Date: | Sep-2018 | DOI: | 10.1029/ 2018TC005182 | URL: | file:///Users/francescomazzarini/Downloads/Viola_et_al-2018-Tectonics.pdf | Keywords: | K-Ar dating fault gouge Northern Apennines Elba Island Neogene geodynamics |
Abstract: | The Northern Apennines (NA) orogenic wedge formed during Oligocene-Miocene convergence and westward subduction of Adria beneath the European Plate. Extension ensued in the Mid-Late Miocene in response to Adria roll-back, causing opening of the back-arc Northern Tyrrhenian Sea. Whether extension continues uninterrupted since the Mid-Late Miocene or it was punctuated by short-lived compressional events, remains, however, uncertain. We used the K-Ar method to date a set of brittle-ductile and brittle deformation zones from the Island of Elba to contribute to this debate. We dated the low-angle Zuccale Fault (ZF), the Capo Norsi-Monte Arco Thrust (CN-MAT), and the Calanchiole Shear Zone (CSZ). The CN-MAT and CSZ are moderately west dipping, top-to-the-east thrusts in the immediate footwall of the ZF. The CSZ slipped 6.14 ± 0.64 Ma (<0.1 μm fraction) and the CN-MAT 4.90 ± 0.27 Ma ago (<0.4 μm fraction). The ZF, although cutting the two other faults, yielded an older age of 7.58 ± 0.11 Ma (<0.1 μm fraction). The ZF gouge, however, contains an illitic detrital contaminant from the Paleozoic age flysch deformed in its hanging wall and the age thus is a maximum faulting age. Removal of ~1% of a 300-Ma-old contaminant brings the ZF faulting age to <4.90 Ma. Our results provide the first direct dating of brittle deformation in the Apennines, constraining Late Miocene-Early Pliocene regional compression. They call for a refinement of current NA geodynamic models in the framework of the Northern Tyrrhenian Sea extension. | Description: | - We provide the first isotopic geochronological constraints on brittle deformation in the NA by illite K-Ar dating of brittle fault rocks - A combined structural-geochronological approach constrains a Late Miocene-Early Pliocene regional compressive stress state |
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Viola_et_al-2018-Tectonics.pdf | New Constraints on the Evolution of the Inner Northern Apennines by K-Ar Dating of Late Miocene-Early Pliocene Compression on the Island of Elba, Italy | 3.35 MB | Adobe PDF | View/Open |
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