Buried and submerged Greek archaeological coastal structures and artifacts as gauges to measure late Holocene seafloor subsidence off Calabria, Italy

This investigation focuses on subsidence of ancient Greek coastal facilities that are now positioned between former shorelines and inner shelf sectors at, and/or seaward of, five Calabrian margin localities in southern Italy. Submerged and/or buried structures provide a record of the following late Holocene long-term average rates of coastal margin subsidence: Sybaris-Thuri on the Taranto Gulf margin (~0.5-1.0 mm/yr); Hipponion-Vibo Valentia positioned along the Tyrrhenian Sea coast (~0.8 to ~3.2 mm/yr); and Locri-Epizefiri, Kaulonia and Capo Colonna on Calabria’s Ionian Sea margin (~1.6, ~1.6-2.4 and ~4.0 mm/yr, respectively). Four of the subsided facilities are positioned near emerged Calabrian areas where prevailing Holocene to ongoing average annual land uplift rates range to ~1.0 mm/yr, while the fifth is in a region where terrains have risen to nearly 2 mm/yr. Submergence of coastal to inner shelf facilities has resulted in part from sea-level rise by about 2 m associated with glacio-hydro-isostatic factors since archaic to classic Greek time. This phenomenon, however, does not explain the wide variation of measured subsidence rates from site-to-site. Particularly significant in this region has been the lowering of coastal site substrates by seismo-tectonic activity (including extensional fault motion), stratal readjustments at depth, and compaction of underlying sediment sequences.