Long-Wavelength Quaternary Forearc Deformation Recorded by Marine Terraces in the Calabrian Arc

Constraints on vertical motions in subduction forearcs can improve understanding of the complex processes that govern the development and evolution of these subduction zones, particularly deep-earth processes that are difficult to directly observe. The Calabria region provides an exceptional natural laboratory for investigating the interplay between mantle dynamics, slab break-off, and forearc rock uplift. Previous geophysical studies show slab tears to the north and south of the ~200 km wide subducting Ionian slab, and the Calabrian forearc archives a history of rock uplift in well-preserved marine terraces. However, despite numerous studies on extensive sequences of deformed marine terraces across the region, the temporal and spatial variability of uplift rates, and their relationship to slab geometry, remain poorly constrained. Complications in using Calabrian terraces to understand the surface response to slab tearing and other subduction processes arise from (1) cross-cutting faults and augment the deeper earth signal of rock uplift, (2) preservation issues due to denudation of terrace sequences, and (3) sparse geochronology. Here, we overcome these challenges using detailed mapping, stratigraphic descriptions, and dating of marine terrace sequences along Calabria’s Ionian Coast, where few active surface-breaking events affect marine terraces, making it the location to image hypothesized signals of rock uplift due to slab tearing and mantle geodynamics. By targeting this tectonic setting, we aim to better resolve spatial variations in uplift rates across the entire plate boundary from slab edge to slab edge and beyond, across a transect extending >300 km. Within this area, 12 samples were collected: one for detrital sanidine ⁴⁰Ar/³⁹Ar dating and 11 for luminescence dating. Preliminary age control and correlations to a sea level curve indicate long-wavelength (100s of km) deformation of marine terraces. Marine terrace-derived rock uplift rates increase southward toward the Strait of Messina, reaching ~1.3 mm/yr near the Strait of Messina above the southern slab tear, decline to ~0.8 mm/yr above the subducting slab, and increase to ~2 mm/yr above the northern tear north of the Sila Massif. We are currently analyzing temporal changes in rock uplift rates over the past 200-500 kyr, as afforded by the terrace record, to assess changes in slab tear and subduction dynamics during the mid-to-late Quaternary. These results suggest the fingerprint of slab tearing is imprinted on the coastal geomorphology of the Calabria forearc and highlight the critical importance of geomorphology in aiding in studies of subduction zone geodynamics.