Publication Date:
2017-04-04
Description:
Magnetic hysteresis measurements of sediments have resulted in widespread reporting of “pseudo-single-domain”-like magnetic properties. In contrast, the ideal single domain (SD) properties that would be expected to be responsible for high quality paleomagnetic records are rare. Determining whether SD particles are rare or common in sediments requires application of techniques that enable discrimination among different magnetic components in a sediment. We apply a range of such techniques and find that SD particles are much more common than has been reported in the literature and that magnetite
magnetofossils (the inorganic remains of magnetotactic bacteria) are widely preserved
at depth in a range of sediment types, including biogenic pelagic carbonates, lacustrine and marine clays, and possibly even in glaci-marine sediments. Thus, instead of being rarely preserved in the geological record, we find that magnetofossils are widespread. This
observation has important implications for our understanding of how sediments become
magnetized and highlights the need to develop a more robust basis for understanding how biogenic magnetite contributes to the magnetization of sediments. Magnetofossils also have grain sizes that are substantially smaller than the 1–15 mm size range for which there
is reasonable empirical support for relative paleointensity studies. The different magnetic response of coexisting fine biogenic and coarser lithogenic particles is likely to complicate relative paleointensity studies. This issue needs much closer attention. Despite the fact that sediments have been subjected to paleomagnetic investigation for over 60 years, much
remains to be understood about how they become magnetized.
Description:
Published
Description:
B08104
Description:
2.2. Laboratorio di paleomagnetismo
Description:
JCR Journal
Description:
restricted
Keywords:
hysteresis
;
magnetite
;
pseudo-single domain
;
single domain
;
04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism
;
04. Solid Earth::04.05. Geomagnetism::04.05.07. Rock magnetism
;
04. Solid Earth::04.05. Geomagnetism::04.05.09. Environmental magnetism
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
