Publication Date:
2017-04-04
Description:
Magnetotactic bacteria intracellularly biomineralize magnetite of an ideal grain size for recording
palaeomagnetic signals. However, bacterial magnetite has only been reported in a few pre-Quaternary
records because progressive burial into anoxic diagenetic environments causes its dissolution. Deep-sea
carbonate sequences provide optimal environments for preserving bacterial magnetite due to low rates of
organic carbon burial and expanded pore-water redox zonations. Such sequences often do not become anoxic
for tens to hundreds of metres below the seafloor. Nevertheless, the biogeochemical factors that control
magnetotactic bacterial populations in such settings are not well known. We document the preservation of
bacterial magnetite, which dominates the palaeomagnetic signal throughout Eocene pelagic carbonates from
the southern Kerguelen Plateau, Southern Ocean. We provide evidence that iron fertilization, associated with
increased aeolian dust flux, resulted in surface water eutrophication in the late Eocene that controlled
bacterial magnetite abundance via export of organic carbon to the seafloor. Increased flux of aeolian ironbearing
phases also delivered iron to the seafloor, some of which became bioavailable through iron reduction.
Our results suggest that magnetotactic bacterial populations in pelagic settings depend crucially on
particulate iron and organic carbon delivery to the seafloor.
Description:
Published
Description:
441-452
Description:
1.8. Osservazioni di geofisica ambientale
Description:
2.2. Laboratorio di paleomagnetismo
Description:
JCR Journal
Description:
restricted
Keywords:
Magnetotactic bacteria
;
Magnetofossils
;
Magnetite
;
Productivity
;
Iron
;
Organic carbon
;
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
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