Combined glacio-eustatic forcing and volcano-tectonic uplift: Geomorphological and geochronological constraints on the Tiber River terraces in the eastern Vulsini Volcanic District (central Italy)
2019
Marra, F. | Costantini, L. | Di Buduo, G.M. | Florindo, F. | Jicha, B.R. | Monaco, L. | Palladino, D.M. | Sottili, G.
In the present paper, we analyze the regional interplay between glacio-eustasy and volcano-tectonic uplift on the Tyrrhenian Sea margin of central Italy. We reconstruct a succession of fluvial terraces in the Tiber River Valley east of the Vulsini Volcanic District and we provide geochronologic constraints allowing for correlation with the sea-level highstands of the Marine Isotope Stage timescale. Results of this study show that glacio-eustatic forcing affected the hydrographic network of the Tiber River, as far as 70 km inland with respect to the present Tyrrhenian coast, consistent with a regional uplift on the order of several tens of meters that affected this region over the last 250 ka. Using six new 40Ar/39Ar dates, we demonstrate the synchronicity between sea-level rise during glacial termination IV and the deposition of a fining-upward sedimentary succession of the Paleo-Tiber River in this area. A detailed reconstruction of the chronostratigraphic setting enabled us to assess local uplift and fault displacement due to volcano-tectonic processes associated with the activities of Bolsena-Orvieto and Latera volcanoes since 350 ka, and develop an uplift curve for the different sectors of the investigated area. Moreover, we estimate sedimentation rate during post-glacial sea-level rise. Strong differential uplift, with rates on the order of 0.6–1.2 mm/yr corresponded with the onset of major eruptive phases, whereas a homogeneous regional uplift of 0.24 mm/yr during the last 125 ka followed this climactic phase. These uplift rates are significantly smaller than sedimentation rate during the glacial termination, consistent with the observed independence of the glacio-eustatic signal.
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