Thrusts control the thermal maturity of accreted sediments

Abstract

Thermal maturity assessments of hydrocarbon-generation potential and thermal history rarely consider how upper-plate structures developing during subduction influence the trajectories of accreted sediments. Our thermomechanical models of subduction support that thrusts evolving under variable sedimentation rates and décollement strengths fundamentally influence the trajectory, temperature, and thermal maturity of accreting sediments. This is notably true for the frontal thrust, which pervasively partitions sediments along a low- and a high-maturity path. Our findings imply that interpretations of the distribution of thermal maturity cannot be detached from accounts of the length and frequency of thrusts and their controlling factors. Our approach takes these factors into consideration and provides a robust uncertainty estimate of maximum exposure temperatures as a function of vitrinite reflectance and burial depth. As a result, our models reduce former inconsistencies between predicted and factual thermal maturity distributions in accretionary wedges.