UPLIFT HISTORY OF THE CENTRAL APENNINES (ITALY): COMBINING STABLE ISOTOPES AND THERMOCHRONOLOGY

Estimates of surface uplift and exhumation are necessary to reconstruct the evolution of mountain belts and quantify the contributions of shallow and deep processes to the underlying geodynamics. We focus on the Central Apennines, which formed as an accretionary wedge before undergoing post-orogenic extension. Since ̴3 Ma, it overlies an area of local slab detachment. We aim to better constrain the landscape evolution and relate surface observables to possible geodynamic processes. To do so, we combine stable isotope paleoaltimetry to reconstruct surface topography, and low-temperature thermochronology to date exhumation since Miocene. We draw upon samples from 13 intermontane basins that record both tectonic and climatic syn-orogenic events.

Here, we present a set of >200 lacustrine and paleosol carbonate d¹⁸O measurements collected from various elevations along the windward side of the mountain range, as well as 28 new apatite (U-Th)/He ages from Miocene sandstones. Since the Pliocene, there is a clear orographic signal, with d¹⁸O decreasing with modern elevation of the basin. However, this d¹⁸O gradient with elevation appears to increase from Pleistocene to late Quaternary, which we attribute to increased orographic rainout, reflecting < 1km of uplift since late Pliocene. Mean AHe ages range from 6.5 Ma on the Thyrrenean coast to 1.62 Ma in the Center and East, suggesting a large scale uplift pulse around 2 Ma associated with extremely high exhumation rates (>1mm/yr). Both our isotopic data and exhumation ages match the suggested timing of slab break-off. This supports the hypothesis that the opening of the Adriatic slab window caused substantial uplift in the area. Further understanding of climatic variations is necessary to improve our estimate of the surface uplift.