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Remnant of the ancient Farallon Plate breakup: A low‐velocity body in the lower oceanic crust off Nicoya Peninsula, Costa Rica ‐ evidence from wide‐angle seismics
Author(s) -
Walther Christian,
Flueh Ernst
Publication year - 2002
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2002gl015026
Subject(s) - geology , crust , oceanic crust , seismology , fibrous joint , continental crust , underplating , plate tectonics , igneous rock , geophysics , subduction , paleontology , tectonics , medicine , anatomy
A seismic wide‐angle section offshore Costa Rica is presented across the boundary between oceanic crust generated at the East Pacific rise (EPR) and at the Galápagos spreading center (GSC) as indicated by magnetic anomalies. This suture, where the Farallon plate broke up ∼23 Ma ago, is marked by pronounced velocity variations throughout the crust including a low‐velocity body in the lower crust. This body is well constrained by refracted waves above the inversion zone and by strong P m P reflections from its lower boundary. The distinctness of this body and the local gravity field point to an igneous intrusion rather than serpentinized rock. Typical oceanic crust is found adjacent to the suture zone.