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Published September 2, 2004 | Supplemental Material
Journal Article Open

Active foundering of a continental arc root beneath the southern Sierra Nevada in California

Abstract

Seismic data provide images of crust–mantle interactions during ongoing removal of the dense batholithic root beneath the southern Sierra Nevada mountains in California. The removal appears to have initiated between 10 and 3 Myr ago with a Rayleigh–Taylor-type instability, but with a pronounced asymmetric flow into a mantle downwelling (drip) beneath the adjacent Great Valley. A nearly horizontal shear zone accommodated the detachment of the ultramafic root from its granitoid batholith. With continuing flow into the mantle drip, viscous drag at the base of the remaining ~35-km-thick crust has thickened the crust by ~7 km in a narrow welt beneath the western flank of the range. Adjacent to the welt and at the top of the drip, a V-shaped cone of crust is being dragged down tens of kilometres into the core of the mantle drip, causing the disappearance of the Moho in the seismic images. Viscous coupling between the crust and mantle is therefore apparently driving present-day surface subsidence.

Additional Information

© 2004 Nature Publishing Group. Received 16 February 2004; Accepted 12 July 2004. G.Z. thanks G. Gehrels, P. Kapp and B.Hacker for comments on preliminary interpretations and manuscripts. Authors' contributions: G.Z., H.G., T.J.O. and C.H.J. cooperated on the seismology analysis and interpretation. M.D. and J.S. provided the geologic and tectonic context. C.H.J. led the PASSCAL deployment to collect the data. G.Z. wrote the Article with contributions from all the authors.

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