K-State Geology Seminar Series Presents

'Slab-mantle interactions control forearc uplift during subduction retreat in central Mediterranean'

by Dr. Sean Gallen, Assistant Professor in the Department of Geosciences at Colorado State University

Thursday, 20 April 2023 | 4:00-5:00 PM

Attend In-Person at 213 Thompson Hall

Title:  Slab-mantle interactions control forearc uplift during subduction retreat in central Mediterranean

Abstract: Landscapes are sensitive recorders of deep Earth processes that we cannot otherwise directly observe and can provide critical constraints on the geodynamic processes involved in subduction zone orogenesis. Here, we recover continuous 30 Myr rock uplift histories for three catchments in the Calabrian forearc of southern Italy using a data-driven inversion of tectonic geomorphology measurements. Rock uplift histories exhibit high rates (>1 mm/yr) from ~30-25 Ma that progressively decline to <0.4 mm/yr by ~15 Ma and stay low before abruptly increasing at ~1.5-1.0 Ma. These results bear little resemblance to the subduction velocity history, implying that crustal thickening through accretionary flux does not dominate uplift. Through comparisons with slab descent reconstructions, we argue that the forearc uplift history primarily reflects the progressive establishment and abrupt destruction of an upper mantle convection cell with strong negative buoyancy. As the slab freely descended through the upper mantle, the size and vigor of the convection cell grew, slowly drawing uplift rates down from ~25-15 Ma. Once the slab encountered the 660 km mantle transition zone, the convection cell was fully established, subduing uplift rates before slab fragmentation and associated small-scale mantle flow disrupted this condition in the Quaternary, facilitating rapid forearc rock uplift.

Bio: 

Sean received his PhD from NC State in 2013 and was the Turner Postdoctoral Fellow in the University of Michigan Department of Earth and Environmental Sciences from 2013-2015. From 2015-2018 he was a senior scientist and lecturer at ETH-Zurich before starting as an Assistant Professor at Colorado State University in 2018. His research is mainly focused on tectonic geomorphology, landscape evolution, and natural hazards.

Modality: In-person at Thompson Hall, Rm 213