Forearc topography and inferred paleotopography are key constraints on the processes acting at plate interfaces along subduction margins. We used along-strike variations in modern topography, trench sediment thickness, and instrumental seismic data sets over >2000 km of the Chilean margin to test previously proposed feedbacks among subducted sediments, plate interface rheology, megathrust seismicity, and forearc elevation. Observed correlations are consistent with subducted sediments playing a prominent role in controlling plate interface rheology, which, in turn, controls the downdip distribution of megathrust seismicity and long-term forearc elevation. High (low) rates of trench sedimentation promote long-term interseismic coupled offshore forearc uplift (subsidence) and onshore forearc platform subsidence (uplift). Low trench sedimentation rates also promote deeper megathrust seismic slip, enhancing short-wavelength coastal zone uplift. Shallowing of subducting slabs contributes to a reduction in coastal zone–onshore forearc relief, in turn preventing formation of onshore forearc basins. The extremely low denudation rates of hyperarid northern Chile have allowed better reconstructions of the histories of paleoelevations and paleoclimate compared to other sections of the forearc. Even if these histories are not suffi ciently resolved to unequivocally assign causality among climate variability, changes in plate interface frictional properties, and forearc elevation, they are consistent with the onset of hyperaridity in the coastal zone at 25–20 Ma (1) triggering long-term, long-wavelength offshore forearc subsidence and onshore forearc uplift, and (2) accelerating short-wavelength coastal zone uplift.
Nicolás J. Cosentino*
Department of Earth and Atmospheric Sciences, Cornell University, 2122 Snee Hall, Ithaca, New York 14853-1504, USA; Universidad Nacional de Córdoba, Facultad de Ciencias Exactas, Físicas y Naturales, Av. Vélez Sársfi eld 299, X5000JJC, Córdoba, Argentina; and Consejo Nacional de Investigaciones Científi cas y Tecnológicas (CONICET), Centro de Investigaciones en Ciencias de la Tierra (CICTERRA), Av. Vélez Sársfi eld 1611, Edifi cio CICTERRA, X5016CGA, Ciudad Universitaria, Córdoba, Argentina
Felipe Aron; Jorge G.F. Crempien
Departamento de Ingeniería Estructural y Geotécnica, Pontificia Universidad Católica de Chile, Vicuña Mackenna 4860, Macul, Santiago, Chile, and National Research Center for Integrated Disaster Risk Management (CIGIDEN), Vicuña Mackenna 4860, Macul, Santiago, Chile
Teresa E. Jordan
Department of Earth and Atmospheric Sciences, Cornell University, 2122 Snee Hall, Ithaca, New York 14853-1504, USA