Title: Upper plate deformation at the Central American Subduction zone
Abstract: Understanding the processes that control the rates, magnitudes, and longevity of forearc deformation is essential for understanding the long-term mass balance of subduction zone systems. This talk will be divided into two parts: In the first part, I will present findings from field geology, offshore seismic data, and IODP coring results to revisit how mass moves through the Central America subduction zone. We’ll explore whether this margin represents a typical “erosive” margin that experiences net mass loss and introduce a model for Plio-Quaternary deformation in southern Costa Rica that does not require significant mass loss from the upper plate. In the second part, I will focus on the causes of uplift above the seismogenic zone of northern Costa Rica. Unlike most subduction zones that show long-term subsidence above the seismogenic zone region, the Nicoya Peninsula experiences prolonged uplift. Paleo-abrasion surfaces at ~500 m elevation in Central Nicoya suggest moderate rock uplift (~0.1 mm/yr) over ~200 km since at least ~1 Ma. This uplift likely involves mechanisms beyond the subduction of bathymetric relief, such as underplating, offshore thrust faults, or megathrust-related uplift. We hypothesize that a decrease in slab curvature, linked to increased slab rigidity beneath Nicoya, drives this long-term uplift, and highlights the role of slab dynamics in vertical tectonism.
Biography: Kristin Morell is an Associate Professor in the School of Earth Sciences at UC Santa Barbara. She is a field geomorphologist that specializes in recent and ongoing active tectonics primarily around subduction zones. Her work spans much of the Pacific margin, with field studies in Central America, Cascadia and Alaska, as well as continental convergence work in the Himalayas. She also has interests in susceptibility of environments to debris flows following major wildfire events.
To join virtually: Zoom
Contact: kmorell@ucsb.edu
Website: https://www.kristinmorell.com
Recording: Zoom Recording (will be available within a week after the seminar)