2026/06/02 by Jonny Wu, Edward Clennett · 1 voice
Earth and Planetary Sciences · #Geological and Geochemical Analysis #earthquake and tectonic studies #Paleontology and Stratigraphy of Fossils
paper · doi:10.1144/jgs2026-001
openalex publication_date 2026/06/02 · openalex created_date 2026/06/03 · openalex updated_date 2026/07/02
The subduction history of the North American Cordillera during Laramide times is debated and may involve subduction of conjugate oceanic plateaux related to the Shatsky–Hess Large Igneous Provinces (LIPs) in the central Pacific. We review updated geologic constraints and present a plate tectonic reconstruction of the Shatsky–Hess LIPs and their conjugates on the Farallon plate, which we call SOHCO (Shatsky–Ojin–Hess conjugates). We use an optimization routine to produce new poles for asymmetric Farallon–Pacific seafloor spreading during Shatsky–Hess Rise formation, which is likely because the Shatsky–Hess LIPs are associated with plume–ridge interaction. Our SOHCO model implies a ∼4300 km-long system of amalgamated conjugate plateaux and seamount chain that is >40% longer than previously modelled. SOHCO subducted continuously under western North America over a protracted 30 Myr period, which may help to explain the extended duration of the long-lived Laramide orogeny from Late Cretaceous to Paleogene. Our main model assumes Shatksy conjugate subduction under the southern Sierra Nevadas at 90 Ma and produces SOHCO subduction under Southern California and northern Mexico from ∼90 to 60 Ma. An alternative assumption of Hess conjugate subduction under the Mojave at 70 Ma produces an earlier and more northerly Shatsky conjugate arrival along northern California at 95 Ma that continues in a trajectory towards Idaho, Wyoming and Montana by 90 Ma. Our new Farallon – Pacific asymmetric seafloor spreading poles provide a new framework to link ancient Pacific plate motions to western North America.