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

Abstract

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 Ma) 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 show stability at all scales, except for subsidence in coastal basins and uplift, at places high, at volcanic centers. On the contrary, sustained, large magnitude uplift of Calabria 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 up larger than since Middle-Late Pleistocene, with rate changes tuned among all sites. The recent increase in uplift rate, detected also in the instrumental record, is related to clustering of strain release, possibly triggered by isostatic response to deglaciation. A weak deformation signal is recorded on the central Adriatic coastline, and records 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 is the dominating contributor. Here, rate and spatial extent of displacements are steady over different time-scales, suggesting prevailing control exercised by plate dynamics.