Revised History of Pleistocene Vertical Motions in NE Sicily and Southern Calabria, Italy, from 40Ar/39Ar Dating and Fault Zone Morphology

Rebecca Dorsey, Gianfranco Di Vincenzo, Marco Meschis, Sergio Longhitano, William Cavazza, Domenico Chiarella

Long-term rates of crustal uplift in southern Calabria and NE Sicily are incompletely understood due to limited information about the age of marine terraces at 1.0–1.3 km above sea level (asl). This study provides a new constraint on high-elevation terrace ages through integrated analysis of geochronology, stratigraphy, shoreline modeling, and fault-zone morphology. 40Ar/39Ar step-heating experiments on glass from a tuff in marine claystone of the Argille di Spadafora, NE Sicily, yield reproducible age spectra with a mean age of 0.481 ± 0.019 Ma (± 2σ). The Argille di Spadafora and equivalent marl in southern Calabria are overlain by Pleistocene marine terrace deposits, indicating the terraces are younger than 0.50 Ma. Paleoshoreline modeling at Campo Piale, southern Calabria, suggests an age of 525–590 ka for a terrace at 600–630 m asl: this is an overestimate because it assumes no fault offsets, tilting or structural warping despite geomorphic evidence for these processes. We correlate the 630-m terrace to the marine terrace at 1.0–1.3 km asl based on recognition of a relay ramp between the Cittanova and Sant’Eufemia faults, and geomorphic evidence for fault offset of the terrace. We conclude that marine terraces up to 1.0–1.3 km asl are all < 0.50 Ma, roughly half the widely cited estimate of 1.0 ± 0.2 Ma. The revised age suggests an average uplift rate of > 2.5 mm/y for the highest terrace, and variable throw rates up to 1.0 mm/y on normal faults that cut the terraces.