The Zuccale Fault, Elba Island, Italy: A new perspective from fault architecture

The Zuccale Fault, central-eastern Elba Island, has been regarded since the 1990s as a low-angle
normal fault that records Neogene crustal extension in the inner (Tyrrhenian side) portion of the northern
Apennines. The flat-lying attitude of the fault zone and the strong excision of thick nappes were the main
reasons for this interpretation. Previous structural and petrographic studies have focused primarily on the
fault rocks themselves without map-scale investigation of the structural setting and deformation structures
in the hanging wall and footwall blocks. Furthermore, despite the complex history proposed for the
Zuccale Fault, the timing of deformation has not yet been constrained by radiometric age data. We present
the findings of recent geological studies on eastern Elba Island that provide significant new insight on
the nature and tectonic significance of the Zuccale Fault. We document in detail the architecture of
breccias and cataclasites that comprise the Zuccale Fault. Our new observations are consistent with a
purely brittle deformation zone that crosscuts older early-middle and late Miocene regional and local
tectonic structures. The activity on the fault postdates emplacement of the late Miocene Porto Azzurro
pluton, and it displaces a previously formed nappe stack ~6km eastward without any footwall exhumation or
hanging wall block rotation. These new data raise questions about the development of misoriented faults
in the upper crust.