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Titel |
Structural architecture and paleofluid evolution of the Compione fault, Northern Apennines |
VerfasserIn |
Alessio Lucca, Fabrizio Storti, Fabrizio Balsamo, Giancarlo Molli |
Konferenz |
EGU General Assembly 2016
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Medientyp |
Artikel
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Sprache |
en
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 18 (2016) |
Datensatznummer |
250124993
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Publikation (Nr.) |
EGU/EGU2016-4515.pdf |
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Zusammenfassung |
The Compione fault (CF) is part of the basin boundary East Lunigiana extensional fault
system, active since Early Pliocene. This system is composed of three main fault segments,
striking almost NW-SE and dipping 60-70˚ to the SW. The offset of the CF exceeds 1 km
and caused the tectonic juxtaposition of turbiditic sandstones of the Late Oligocene-Early
Miocene Macigno Fm. in the footwall, against the calcareous pelites, siltites and fine
sandstones of the Ottone Fm. (a Late Cretaceous Ligurian Helminthoid Flysch) in the
hangingwall. The CF overprints the previously-formed contractional tectonic stack where the
Ottone Fm. overthrusted the Macigno Fm. during Miocene times. We performed a detailed
structural analysis along a cross-section perpendicular to the CF in its central part, coupled
with laboratory analyses including standard and cold cathodoluminescence petrography,
microtermometric and stable isotope analysis of vein cements, and particle size analysis
of fault core rocks. Field data show that the architecture of the CF is formed by
an about 1.5 km wide asymmetric damage domain, composed of an up to 1 km
wide footwall damage zone, an almost 500 m wide hangingwall damage zone and a
core domain with variable thickness, up to some tens of meters, mostly composed
of cataclastic sandstones and gouge layers, which typically incorporates one or
more shear lenses of Macigno sandstones. In the footwall, extensional deformation
affecting very thick and coarse sandstone strata caused intense fracturing, mostly by
low-displacement conjugate extensional faulting. Hangingwall rocks are less fractured than
footwall rocks due to their different composition and rheology, which favoured
abundant dissolution-cementation processes and extensional faulting along less
numerous, higher displacement shear zones. We propose an evolutionary model of
the CF that starts with upward propagation as a blind extensional fault dissecting
the previously formed thrust-related anticline. Intense fracturing in the footwall
sandstones occurred in the very early fault propagation stages, mostly in the process zone
ahead of the fault tip. With increasing displacement, extensional fault-propagation
folding caused passive rotation of both footwall and hangingwall rocks, and of
previously-formed fracture patterns, up to 55-60˚ to the SW. Eventually, fault
breakthrough caused deformation localization within a thick cataclastic fault core. |
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