Farallon slab detachment and deformation of the Magdalena Shelf, southern Baja California

Abstract

Subduction of the Farallon plate beneath northwestern Mexico stalled by ∼12 Ma when the Pacific‐Farallon spreading‐ridge approached the subduction zone. Coupling between remnant slab and the overriding North American plate played an important role in the capture of the Baja California (BC) microplate by the Pacific Plate. Active‐source seismic reflection and wide‐angle seismic refraction profiles across southwestern BC (∼24.5°N) are used to image the extent of remnant slab and study its impact on the overriding plate. We infer that the hot, buoyant slab detached ∼40 km landward of the fossil trench. Isostatic rebound following slab detachment uplifted the margin and exposed the Magdalena Shelf to wave‐base erosion. Subsequent cooling, subsidence and transtensional opening along the shelf (starting ∼8 Ma) starved the fossil trench of terrigenous sediment input. Slab detachment and the resultant rebound of the margin provide a mechanism for rapid uplift and exhumation of forearc subduction complexes.

Seismic structure beneath the Gulf of California: a contribution from group velocity measurements

“…Based on our coverage, this feature is not continuous with the fossil slab we interpret to the north, it is deeper than that and smaller in lateral extent. Using active source seismic reflection and wideangle seismic refraction profiles across southwestern Baja California (∼24.5 o N), Brothers et al (2012) infer an oceanic slab detachment beneath the western margin of Baja ∼40 km landwards of the extinct Farallon-North America trench. While we do not have good resolution as far west as Brothers et al (2012), we do observe a high-velocity anomaly starting at around ∼50-km depth near the western Baja coastline and beneath Baja (Fig.…”

Modo de extension de la corteza y formacion del Sistema Extensional de Cerralvo, sur del Golfo de California, a partir de datos de reflexion sismica en 2D

“…Con base en correlaciones litológicas regionales, Fletcher et al (2007) demostraron que el desplazamiento finito acomodado por la zona de cizalla al oeste de Baja California es menor a 150 km. Este sistema no sólo consiste en fallas laterales sino también presenta grandes cuencas extensionales, lo cual demuestra que el régimen de cizalla es uno de transtensión integrada Brothers et al, 2012). Además, estudios geodésicos demuestran que este sistema de fallas sigue siendo activo en el presente (Dixon et al, 2000;Gonzalez-Garcia et al, 2003, Plattner et al, 2007.…”

“…Estimaciones similares han sido calculadas al sur del GC hacia la Elevación del Pacífico Oriental (Figura 1; Páramo et al, 2008). La extensión estimada en esta región es de 35 km, en la cual la corteza continental, 28 km de espesor, se ha adelgazado hasta alcanzar 7 km de corteza oceánica, lo que resulta en un factor de estiramiento de 4 (Páramo et al, 2008;Brothers et al, 2012;Bot et al, 2016). El análisis de la interacción entre la deformación y la sedimentación sin-tectónica en el SEC sugiere que la magnitud del transporte tectónico es hasta tres veces mayor en magnitud respecto a la sedimentación marina en la región, lo que resulta en tasas de sedimentación relativamente bajas en comparación con las cuencas sedimentarias del norte del GC, donde los sedimentos alcanzan espesores de hasta 5 km (e.g., cuenca Tiburón; Contreras-Pérez et al, 2012).…”

Untitled

“…The increasing northwestward motion of Baja California follows its coupling with the shallow part of the subducted Magdalena plate once the lower part of the slab had detached and started foundering in the mantle (Ferrari, 2004). The precise location of slab detachment in the Gulf of California area is debated, but it is thought to have initiated 13-12 Ma Pallares et al, 2007;Brothers et al, 2012). The ascent of hot asthenospheric mantle into the slab gap that formed after the slab detachment may have triggered extensive melting of the subduction-modifi ed former mantle wedge, which ultimately led to the ca.…”