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

• Published in: Geophysical research letters Vol. 39; no. 9
• Main Authors: Brothers, Daniel, Harding, Alistair, González-Fernández, Antonio, Holbrook, W. Steven, Kent, Graham, Driscoll, Neal, Fletcher, John, Lizarralde, Dan, Umhoefer, Paul, Axen, Gary
• Format: Journal Article
• Language: English
• Published: Washington, DC Blackwell Publishing Ltd 01.05.2012; American Geophysical Union; John Wiley & Sons, Inc
• Subjects: adakite; Detachment; Earth sciences; Earth, ocean, space; Exact sciences and technology; exhumation; Fossils; Geology; Plate tectonics; rifting; Seismic engineering; Seismic phenomena; seismic refraction; Seismology; Shelves; Slabs; subduction; transtension; Trenches; Great Britain; Kent England; Europe; Baja California; England; Mexico; United Kingdom; Pacific Ocean; Western Europe; waves; seismic refraction; isostatic rebound; exhumation; Thick plate; North America; microplates; Pacific Plate; coupling; North American Plate; subduction; Farallon Plate; uplifts; seismic reflection; erosion; cooling; subsidence; deformation; subduction zones; slabs; trenches
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2011GL050828

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. Key Points First detailed crustal image of southern Baja California microplate Beneath the western Baja California margin, ~40 km of relic Farallon slab exists Relationship between slab detachment, uplift, magmatism, and transtension