Chains, clumps, and strings; magnetofossil taphonomy with ferromagnetic resonance spectroscopy

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doi: 10.1016/j.epsl.2006.05.001
Author(s): Kopp, Robert E.; Weiss, Benjamin P.; Maloof, Adam C.; Vali, Hojatollah; Nash, Cody Z.; Kirschvink, Joseph L.
Author Affiliation(s): Primary:
California Institute of Technology, Division of Geological and Planetary Sciences, Pasadena, CA, United States
Massachusetts Institute of Technology, United States
McGill University, Canada
Volume Title: Earth and Planetary Science Letters
Source: Earth and Planetary Science Letters, 247(1-2), p.10-25. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X CODEN: EPSLA2
Note: In English. 45 refs.; illus., incl. 4 tables
Summary: Magnetotactic bacteria produce intracellular crystals of magnetite or greigite, the properties of which have been shaped by evolution to maximize the magnetic moment per atom of iron. Intracellular bacterial magnetite therefore possesses traits amenable to detection by physical techniques: typically, narrow size and shape distributions, single-domain size and arrangement in linear chains, and often crystal elongation. Past strategies for searching for bacterial magnetofossils using physical techniques have focused on identifying samples containing significant amounts of single domain magnetite or with narrow coercivity distributions. Searching for additional of traits would, however, increase the likelihood that candidate magnetofossils are truly of biological origin. Ferromagnetic resonance spectroscopy (FMR) is in theory capable of detecting the distinctive magnetic anisotropy produced by chain arrangement and crystal elongation. Here we present analyses of intact and lysed magnetotactic bacteria, dilutions of synthetic magnetite, and sedimentary samples of modern carbonates from the Great Bahama Bank, Oligocene-Miocene deep-sea muds from the South Atlantic, and Pleistocene lacustrine deposits from Mono Basin, California. We demonstrate that FMR can distinguish between intact bacterial magnetite chains, collapsed chains, and linear strings of magnetite formed by physical processes. We also show that sediments in which the magnetization is likely carried by bacterial magnetite have FMR spectra resembling those of intact or altered bacterial magnetite chains.
Year of Publication: 2006
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
Key Words: 09 Paleontology, Paleobotany; Angola Basin; Anisotropy; Atlantic Ocean; Bacteria; Biogenic processes; Biomineralization; California; Cenozoic; DSDP Site 522; Deep Sea Drilling Project; EPR spectra; Great Bahama Bank; Greigite; IPOD; Lacustrine environment; Lake sediments; Leg 73; Magnetic domains; Magnetite; Magnetization; Magnetospirillum; Magnetospirillum magneticum; Magnetotactic taxa; Marine sediments; Microfossils; Miocene; Mono Basin; Mono County California; Morphology; Neogene; North Atlantic; Oligocene; Oxides; Paleogene; Paleomagnetism; Pleistocene; Quaternary; Sediments; Simulation; Single domains; South Atlantic; Spectra; Sulfides; Taphonomy; Tertiary; United States
Coordinates: N220000 N260000 W0760000 W0792000
N373000 N384000 W1175000 W1193000
Record ID: 2008012910
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands