Open AccessPulsed subduction accretion and tectonic erosion reconstructed since 2.5 Ma from the tephra record offshore Costa Rica
Author(s) -
Clift Peter D.,
Chan LuiHeung,
Blusztajn Jerzy,
Layne Graham D.,
Kastner Miriam,
Kelly Robyn K.
Publication year - 2005
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2005gc000963
Subject(s) - forearc , geology , tephra , subduction , provenance , accretion (finance) , geochemistry , seamount , volcanic arc , tectonics , erosion , accretionary wedge , geomorphology , volcano , paleontology , physics , astrophysics
Tephra layers recovered by Ocean Drilling Program from the forearc and trench regions offshore the Nicoya Peninsula of Costa Rica allow the temporal evolution of the volcanic arc to be reconstructed since 2.5 Ma. Major and trace element analyses by microprobe methods reveal a dominant tholeiitic character and a provenance in the Costa Rican area. The tephra show long‐term coherent variability in geochemistry. One tephra dated at 1.45 Ma shows minimum values in ɛ Nd and maximum Li/Y consistent with very high degrees of sediment recycling at this time. However, overall Li/Y and δ 7 Li increase with SiO 2 content, suggesting addition of heavy Li through forearc tectonic erosion and crustal assimilation. Peak values in δ 7 Li starting at 1.45 Ma and lasting ∼0.5 m.y. indicate enhanced tectonic erosion of the forearc possibly caused by subduction of a seamount at 1.45 Ma. The tephra record indicates significant temporal variability in terms of sediment subduction, reconciling the geologic evidence for long‐term tectonic erosion and geochemical evidence for recent sediment accretion in the modern Central American arc.