In situ magnetic identification of giant, needle-shaped magnetofossils in Paleocene-Eocene Thermal Maximum sediments.

Affiliation

Wagner CL(1), Egli R(2), Lascu I(3), Lippert PC(4)(5), Livi KJT(6), Sears HB(7).
Author information:
(1)Department of Geology and Geophysics, University of Utah, Salt Lake City, UT 84112; [Email]
(2)Division of Data, Methods and Models, Central Institute of Meteorology and Geodynamics, 1190 Vienna, Austria.
(3)Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560.
(4)Department of Geology and Geophysics, University of Utah, Salt Lake City, UT 84112.
(5)Global Change and Sustainability Center, University of Utah, Salt Lake City, UT 84112.
(6)Materials Characterization and Processing Center, Department of Materials Sciences and Engineering, Johns Hopkins University, Baltimore, MD 21218.
(7)Department of Geology, Colby College, Waterville, ME 04901.

Abstract

Near-shore marine sediments deposited during the Paleocene-Eocene Thermal Maximum at Wilson Lake, NJ, contain abundant conventional and giant magnetofossils. We find that giant, needle-shaped magnetofossils from Wilson Lake produce distinct magnetic signatures in low-noise, high-resolution first-order reversal curve (FORC) measurements. These magnetic measurements on bulk sediment samples identify the presence of giant, needle-shaped magnetofossils. Our results are supported by micromagnetic simulations of giant needle morphologies measured from transmission electron micrographs of magnetic extracts from Wilson Lake sediments. These simulations underscore the single-domain characteristics and the large magnetic coercivity associated with the extreme crystal elongation of giant needles. Giant magnetofossils have so far only been identified in sediments deposited during global hyperthermal events and therefore may serve as magnetic biomarkers of environmental disturbances. Our results show that FORC measurements are a nondestructive method for identifying giant magnetofossil assemblages in bulk sediments, which will help test their ecology and significance with respect to environmental change.