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Published November 16, 2007 | Supplemental Material + Updated
Journal Article Open

Magnetofossil Spike During the Paleocene-Eocene Thermal Maximum: Ferromagnetic Resonance, Rock Magnetic, and Electron Microscopy Evidence from Ancora, New Jersey, USA


Previous workers identified a magnetically anomalous clay layer deposited on the northern United States Atlantic Coastal Plain during the Paleocene-Eocene Thermal Maximum (PETM). The finding inspired the highly controversial hypothesis that a cometary impact triggered the PETM. Here we present ferromagnetic resonance (FMR), isothermal and anhysteretic remanent magnetization, first order reversal curve, and transmission electron microscopy analyses of late Paleocene and early Eocene sediments in drillcore from Ancora, New Jersey. A novel paleogeographic analysis applying a recent paleomagnetic pole from the Faeroe Islands indicates that New Jersey during the initial Eocene had a ~6-9 degrees lower paleolatitude (~27.3 degrees for Ancora) and a more zonal shoreline trace than in conventional reconstructions. Our investigations of the PETM clay from Ancora reveal abundant magnetite nanoparticles bearing signature traits of crystals produced by magnetotactic bacteria. This result, the first identification of ancient biogenic magnetite using FMR, argues that the anomalous magnetic properties of the PETM sediments are not produced by an impact. They instead reflect environmental changes along the eastern margin of North America during the PETM that led to enhanced production and/or preservation of magnetofossils.

Additional Information

Author postprint. An edited version of this paper was published by the AGU. Copyright © 2007 by the American Geophysical Union. Received 27 April 2007; revised: 25 July 2007; accepted: 29 August 2007; published: 16 November 2007. We thank A. Maloof, D. Evans, M. Pagani, E. Thomas, and K. Turekian for comments on an earlier version of this article, and G. Dickens for spurring REK's initial interest in magnetically anomalous PETM sediments. We thank D. Kent and the Ocean Drilling Program for access to samples and also thank D. Kent for access to the Rutgers AGM. NASA and the Agouron Institute provided support through grants to JLK. The Natural Sciences and Engineering Research Council of Canada provided support through a grant to HV.

Attached Files

Supplemental Material - 2007pa001473-figS1-AncoraRmgProfiles.pdf

Supplemental Material - 2007pa001473-figS2-AncoraCoercivity.pdf

Supplemental Material - 2007pa001473-figS3-AncoraARM.pdf

Supplemental Material - 2007pa001473-figS4-Anc556-FORC.pdf

Supplemental Material - 2007pa001473-figS5-Anc559-HRTEMandEDS.tif

Supplemental Material - 2007pa001473-readme.txt

Supplemental Material - 2007pa001473-tableS1-sampledata.txt

Supplemental Material - 2007pa001473-tableS2-poleparameters.txt

Supplemental Material - 2007pa001473-tableS3-paleolatitudes.txt

Supplemental Material - 2007pa001473-tex1-RemnanentAndFORC.pdf

Supplemental Material - 2007pa001473-tex2-Paleogeography.pdf

Updated - Kopp2007_Postprint_Magnetofossil_Spike.pdf


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Additional details

August 22, 2023
October 16, 2023