Quantified abundance of magnetofossils at the Paleocene-Eocene boundary from synchrotron-based transmission X-ray microscopy

Huapei Wang, Jun Wang, Yu Chen Karen Chen-Wiegart, Dennis V. Kent

Research output: Contribution to journalArticle

2 Scopus citations

Abstract

The PaleocenëCEocene boundary (~55.8 million years ago) is marked by an abrupt negative carbon isotope excursion (CIE) that coincides with an oxygen isotope decrease interpreted as the PaleocenëCEocene thermal maximum. Biogenic magnetite (Fe3O4) in the form of giant (micron-sized) spearhead-like and spindle-like magnetofossils, as well as nano-sized magnetotactic bacteria magnetosome chains, have been reported in clay-rich sediments in the New Jersey Atlantic Coastal Plain and were thought to account for the distinctive single-domain magnetic properties of these sediments. Uncalibrated strong field magnet extraction techniques have been typically used to provide material for scanning and transmission electron microscopic imaging of these magnetic particles, whose concentration in the natural sediment is thus difficult to quantify. In this study, we use a recently developed ultrahighresolution, synchrotron-based, full-field transmission X-ray microscope to study the iron-rich minerals within the clay sediment in their bulk state. We are able to estimate the total magnetization concentration of the giant biogenic magnetofossils to be only ¡10% of whole sediment. Along with previous rock magnetic studies on the CIE clay, we suggest that most of the magnetite in the clay occurs as isolated, near-equidimensional nanoparticles, a suggestion that points to a nonbiogenic origin, such as comet impact plume condensates in what may be very rapidly deposited CIE clays.

Original languageEnglish (US)
Pages (from-to)12598-12603
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume112
Issue number41
DOIs
StatePublished - Oct 13 2015

All Science Journal Classification (ASJC) codes

  • General

Keywords

  • Impact plume condensate
  • Marlboro Clay
  • New Jersey Atlantic Coastal Plain
  • Ocean Drilling Program Leg 174AX
  • Paleocene-Eocene thermal maximum

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