Foundered Lithospheric Segments Dropped into the Mantle Transition Zone Beneath Southern California, USA


The diverse range of active tectonics occurring in southern California, USA, offers an opportunity to explore processes of continental deformation and modification in response to the instability of the Pacific and Farallon plates. Here, we present a high-resolution receiverfunction image of the mantle transition zone (MTZ). Our result reveals significant lateral heterogeneities in the deep mantle beneath southern California. Both seismic tomography and MTZ discontinuity deflections reveal foundered lithospheric segments that have dropped into the MTZ beneath the western Transverse Ranges, the Peninsular Ranges, and part of the southern Sierra Nevada. Water dehydrated from these foundered materials may contribute to the observed MTZ thickening. Our observations, combined with previous tomography and geochemical results, indicate that lithospheric foundering of fossil arc roots provides a way for geochemical heterogeneities to be recycled into the underlying mantle, and suggest that the foundered materials can play a significant role in inducing lateral variations of MTZ structure.


Geosciences and Geological and Petroleum Engineering

Research Center/Lab(s)

Center for Research in Energy and Environment (CREE)

Second Research Center/Lab

Center for High Performance Computing Research

Keywords and Phrases

Seismology, Continental deformation; Geochemical heterogeneity; Lateral heterogeneity; Lateral variations; Mantle transition zone; Seismic tomography; Southern California; Southern sierra nevada, Geochemistry, deflection; deformation; discontinuity; geochemistry; heterogeneity; image analysis; lithosphere; mantle; plate tectonics; seismic tomography, California; Coast Ranges; Peninsular Ranges; Sierra Nevada [California]; Transverse Ranges; United States

International Standard Serial Number (ISSN)

0091-7613; 1943-2682

Document Type

Article - Journal

Document Version


File Type





© 2020 Geological Society of America (GSA), All rights reserved.

Publication Date

01 Feb 2020