Fossil slabs attached to unsubducted fragments of the Farallon plate

Yun Wang, Donald W. Forsyth, Christina J. Rau, Nina Carriero, Brandon Schmandt, James B. Gaherty, Brian Savage

Research output: Contribution to journalArticlepeer-review

69 Scopus citations


As the Pacific-Farallon spreading center approached North America, the Farallon plate fragmented into a number of small plates. Some of the microplate fragments ceased subducting before the spreading center reached the trench. Most tectonic models have assumed that the subducting oceanic slab detached fromthesemicroplates close to the trench, but recent seismic tomography studies have revealed a high-velocity anomaly beneath Baja California that appears to be a fossil slab still attached to the Guadalupe and Magdalena microplates. Here, using surface wave tomography, we establish the lateral extent of this fossil slab and show that it is correlated with the distribution of high-Mg andesites thought to derive from partial melting of the subducted oceanic crust. We also reinterpret the high seismic velocity anomaly beneath the southern central valley of California as another fossil slab extending to a depth of 200 km ormore that is attached to the former Monterey microplate. The existence of these fossil slabsmay force a reexamination ofmodels of the tectonic evolution of western North America over the last 30 My.

Original languageEnglish (US)
Pages (from-to)5342-5346
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number14
StatePublished - Apr 2 2013
Externally publishedYes


  • Plate tectonics
  • Seismology
  • Subduction

ASJC Scopus subject areas

  • General


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