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

Abstract

GEOPHYSICAL RESEARCH LETTERS, VOL. 39, L09307, 7 PP., 2012
doi:10.1029/2011GL050828

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

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

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

Daniel Brothers

Woods Hole Coastal and Marine Science Center, U.S. Geological Survey, Woods Hole, Massachusetts, USA

Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, USA

Alistair Harding

Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, USA

Antonio Gonz?lez-Fern?ndez

Department of Geology, CICESE, Ensenada, Mexico

W. Steven Holbrook

Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming, USA

Graham Kent

Nevada Seismological Laboratory, University of Nevada, Reno, Reno, Nevada, USA

Neal Driscoll

Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, USA

John Fletcher

Department of Geology, CICESE, Ensenada, Mexico

Dan Lizarralde

Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA

Paul Umhoefer

School of Earth Sciences and Environmental Sustainability, Northern Arizona University, Flagstaff, Arizona, USA

Gary Axen

Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology, Socorro, New Mexico, USA

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.

/journals/gl/gl1209/2011GL050828/

Received 11 January 2012; accepted 18 March 2012; published 8 May 2012.

Citation: Brothers, D., A. Harding, A. Gonz?lez-Fern?ndez, W. S. Holbrook, G. Kent, N. Driscoll, J. Fletcher, D. Lizarralde, P. Umhoefer, and G. Axen (2012), Farallon slab detachment and deformation of the Magdalena Shelf, southern Baja California, Geophys. Res. Lett., 39, L09307, doi:10.1029/2011GL050828.

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