Reconstructing the evolution of the submarine Monterey Canyon System from Os, Nd, and Pb isotopes in hydrogenetic Fe-Mn crusts

T.A. Conrad; S.G. Nielsen; Bernhard Peucker-Ehrenbrink; J. Blusztajn; D. Winslow; James R. Hein; A. Paytan

doi:10.1002/2017GC007071

Reconstructing the evolution of the submarine Monterey Canyon System from Os, Nd, and Pb isotopes in hydrogenetic Fe-Mn crusts

Geochemistry, Geophysics, Geosystems

By: T.A. Conrad, S.G. Nielsen, Bernhard Peucker-Ehrenbrink, J. Blusztajn, D. Winslow, James R. Hein, and A. Paytan

https://doi.org/10.1002/2017GC007071

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Abstract

The sources of terrestrial material delivered to the California margin over the past 7 Myr were assessed using ¹⁸⁷Os/¹⁸⁸Os, Nd, and Pb isotopes in hydrogenetic ferromanganese crusts from three seamounts along the central and southern California margin. From 6.8 to 4.5 (± 0.5) Ma, all three isotope systems show more radiogenic values at Davidson Seamount, located near the base of the Monterey Canyon System, than in Fe-Mn crusts from the more remote Taney and Hoss seamounts. At the Taney seamounts, approximately 225 km farther offshore from Davidson Seamount, ¹⁸⁷Os/¹⁸⁸Os values, but not Pb and Nd isotope ratios, also deviate from the Cenozoic seawater curve towards more radiogenic values from 6.8 to 4.5 (± 0.5) Ma. However, none of the isotope systems in Fe-Mn crusts deviate from seawater at Hoss Seamount located approximately 450 km to the south. The regional gradients in isotope ratios indicate that substantial input of dissolved and particulate terrestrial material into the Monterey Canyon System is responsible for the local deviations in the seawater Nd, Pb, and Os isotope compositions from 6.8 to 4.5 (± 0.5) Ma. The isotope ratios recorded in Fe-Mn crusts are consistent with a southern Sierra Nevada or western Basin and Range provenance of the terrestrial material which was delivered by rivers to the canyon. The exhumation of the modern Monterey Canyon must have begun between 10 and 6.8 ± 0.5 Ma, as indicated by our data, the age of incised strata, and paleo-location of the Monterey Canyon relative to the paleo-coastline.

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Additional publication details
Publication type	Article
Publication Subtype	Journal Article
Title	Reconstructing the evolution of the submarine Monterey Canyon System from Os, Nd, and Pb isotopes in hydrogenetic Fe-Mn crusts
Series title	Geochemistry, Geophysics, Geosystems
DOI	10.1002/2017GC007071
Volume	18
Issue	11
Year Published	2017
Language	English
Publisher	AGU
Contributing office(s)	Pacific Coastal and Marine Science Center
Description	18 p.
First page	3946
Last page	3963
Country	United States
State	California
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