Raised coastal terraces along the Ionian Sea coast of northern Calabria, Italy, suggest space and time variability of tectonic uplift rates
A detailed study of uplifted Middle–Late Pleistocene marine terraces on the eastern side of northern Calabria, southern Italy, provides insights into the temporal and spatial scale variability of vertical displacement rates over a time span of ∼400 ka. Calabria is located in the frontal orogen of southern Italy above the westerly-plunging Ionian slab, and a combination of lithospheric, crustal, and surface processes concurred to rapid Late Quaternary uplift. Eleven terrace orders and a raised Holocene beach were mapped up to ∼480 m a.s.l., and were correlated between the coastal slopes of Pollino and Sila mountain ranges across the Sibari Plain, facing the Ionian Sea side of northeastern Calabria. Precise corrections were applied to the measured shoreline angles in order to account for uncertainty in measurement, erosion of marine deposits, recent debris shedding, and bathymetric range of markers. Radiometric (ESR and 14C) dating of shells provides a crono-stratigraphic scheme, although many samples were found to be resedimented in younger terraces. Terrace T4, whose inner margin stands at elevations of 94–130 m, is assigned to MIS 5.5 (∼124 ka), based on new ESR dating and previous amino acid racemization estimations. The underlying terraces T3, T2 and T1 are attributed to MIS 5.3 (∼100 ka), 5.1 (∼80 ka) and 3 (∼60 ka), as inferred from their relative position supplemented by ESR and 14C age determinations. The age of higher terraces is poorly constrained, but conceivably is tracked back to MIS 11 (∼400 ka). The reconstructed depositional sequence of terraces attributed to MIS 5.5 and 7 reveals two regressive marine cycles separated by an alluvial fanglomerate, which, given the steady uplift regime, points to minor sub-orbital sea-level changes during interstadial highstands. Based on the terrace chronology, uplift in the last ∼400 ka occurred at an average rate of 1 mm/a, but was characterized by the alternation of more rapid (up to ∼3.5 mm/a) and slower (down to ∼0.5 mm/a) periods of displacement. Spatial variability in uplift rates is recorded by the deformation profile of terraces parallel to the coast, which document the growth of local fold structures.
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