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Free keywords:
Faulting; Isotopes; Sea level; Surface waters, Accretionary wedge; Central Apennines; Geodynamic process; Normal faulting; Slab break-off; Slab detachment; Stable isotopes; Stable oxygen isotopes, Topography
Abstract:
The central Apennines, an accretionary wedge overlying an area of slab detachment, are characterized by prominent topography, active normal faulting, and high uplift rates. However, previous studies have failed to resolve the surface uplift history, complicating efforts to link the topographic evolution with underlying geodynamic processes. We aim to better quantify orographic changes by using stable oxygen isotope paleoaltimetry. Modern surface water δ18O are 5‰ lower at high elevation than at sea level, reflecting orographic rainout over the Apennines. We present 262 new lacustrine and paleosol carbonate δ18O measurements collected from ten extensional intermontane basins—spanning both high and low elevations—and combine these with 1,166 published δ18O data, permitting us to constrain changes in δ18O both spatially and temporally. Since the Pliocene, δ18O in present-day high-elevation basins has continuously decreased, even as δ18O in lowland basins has remained constant over time. We attribute this continuous 5‰ shift to increased orographic rainout as the central Apennines were uplifted. We estimate an increase in mean elevation of approximately 1–2 km since the late Pliocene, and these estimates match the suggested timing and expected amplitude of slab break-off related uplift. This supports the hypothesis that the opening of the Adriatic slab window and associated mantle flow contributed significantly to building topography in the central Apennines. © 2020 Elsevier B.V.
