The timescale and spatial extent of recent vertical tectonic motions in Italy: insights from relative sea-level changes studies

Luigi Ferranti, Fabrizio Antonioli , Carmelo Monaco, Marco Anzidei, and Paolo Stocchi

Vertical tectonic displacements in Italy since 125 to 1 kyr BP are drawn from relative sea-level (RSL) history studies at coastal sites, and, together with instrumental observations, allow to bridge the gap with events recorded in the geologic (1 Myr) archive. Our analysis aims at establishing the appropriate spatial extent, rate and duration of vertical tectonic motion within individual crustal segments, and at placing constraints on the contribution to displacements coming from regional (deep) and local (shallow-crustal) sources. The central and northern Tyrrhenian Sea and the Ligurian Sea margins are nearly stable during the last 100 kyr, except for subsidence in coastal basins and uplift, at places high, at volcanic centers. On the contrary, sustained, large magnitude uplift of Calabria and eastern Sicily embeds a deep-seated contribution, highlighted by the spatial coincidence of the uplifting province with a lithospheric slab, and a contribution from local faults and folds. Holocene uplift was higher than uplift recorded by Middle-Late Pleistocene markers, and the rate of changes was tuned among all coastal sites. The recent increase in uplift rate, detected also in the instrumental record, is related to clustering of fault strain release, possibly triggered by the isostatic response to deglaciation. A weak deformation signal is recorded on the central Adriatic coastline, and may record slow Apennines thrust belt migration. In the northern Adriatic Sea, vertical tectonic motions result from opposite displacements in the Southern Alps, internal Dinarids and Northern Apennines, but flexure of the Adriatic (micro-) plate beneath the Northern Apennines appears the dominating contributor. Here, rate and spatial extent of displacements are steady over different time-scales, highlighting the control exercised by slab dynamics.