Bayesian tectonic subsidence modeling supports polyphase extension of the western continental margin of Laurentia

Geological data and basin subsidence modeling results from the western margin of North America (Laurentia) have supported a late Ediacaran to early Cambrian age for the onset of passive margin sedimentation following the protracted breakup of Rodinia. However, several recent studies posit that increased early Cambrian subsidence may instead be driven primarily by eustatic sea-level rise. Here, we present new quantitative subsidence analyses of Neoproterozoic−Paleozoic strata in the southern Great Basin, USA, using decompaction, backstripping, and Bayesian thermal subsidence modeling methods that statistically propagate uncertainties. Our results support polyphase extension along the ancestral western margin of Laurentia and are consistent with a rift-drift transition in southwestern Laurentia that broadly overlaps with the Ediacaran−Cambrian transition. Although we do not discount the role of eustasy in facilitating increased accommodation space in the early Cambrian, the magnitude and local variability of this signal require additional tectonic forcings.