Fig. 5: Schematic models for the two-stage evolution of the Southern California Batholith.
From: Magmatic surge requires two-stage model for the Laramide orogeny
a Late Cretaceous arc flare-up in the SCB occurred from 90–70 Ma. Extension in the backarc occurred in the eastern Mojave region and may be related to lithospheric delamination19, while shortening occurred in the Laramide thrust belt. This phase coincides with possible collision and dextral (northward) translation of the Insular superterrane (IST)18 that may have occurred north of the SCB and the future Garlock Fault (fGF). b Cessation of magmatism, rapid cooling after 75-70 Ma in the SCB, and underthrusting of the Pelona schist is linked to flat-slab subduction and underthrusting of the Hess conjugate (H). Eastward (continentward) migration of the arc is associated with basement-involved thrusting and basin formation in the Laramide fold and thrust-belt. Existing mainstream models focus on this stage of the Laramide orogeny and our data show that this event occurred no earlier than 75-70 Ma and involved the Hess conjugate (rather than the Shatsky conjugate). Global plate reconstructions are modified after42.
