Fig. 2: Timing of Mesozoic events in the Southern California Batholith (SCB).
From: Magmatic surge requires two-stage model for the Laramide orogeny
a Histogram and kernel density estimates for plutons in the SCB. b Calculated areal addition rates (km2/Ma) versus time for the Mesozoic SCB in 5 m.y. bins. Areal addition rates for the Sierra Nevada Batholith are shown for comparison (not to scale)38. c Temporal evolution of magmatism deformation, metamorphism, deposition, and flat-slab subduction in the SCB. Our new model is compatible with underthrusting of the conjugate Hess oceanic plateau after 75-70 Ma, but is inconsistent with earlier amagmatic models and collision of the putative conjugate Shatsky Rise at ca. 88 Ma. The two stages of the Laramide orogeny are illustrated at the bottom of C. Stage I involved a magmatic flare-up event associated with granulite-facies metamorphism in the SCB, and basement-involved thrusting and basin formation in SW Montana. Stage II involves rapid cooling of the SCB, widespread basement-involved thrusting, and basin formation in Utah, Colorado and Wyoming. We attribute this latter part of the Laramide orogeny to underthrusting of the conjugate Hess oceanic plateau beneath the SCB. SCB Southern California Batholith, SNB Sierra Nevada Batholith.
