Publication Date:
2020-02-24
Description:
We report a palaeomagnetic investigation of the last full geomagnetic field reversal, the
Matuyama-Brunhes (M-B) transition, as reserved in a continuous sequence of exposed lacustrine sediments in the Apennines of Central Italy. The palaeomagnetic record provides the most direct evidence for the tempo of transitional field behaviour yet obtained for the M-B transition.
40Ar/39Ar dating of tephra layers bracketing the M-B transition provides high-accuracy age constraints and indicates a mean sediment accumulation rate of about 0.2 mm yr–1 during the transition. Two relative palaeointensity (RPI) minima are present in the M-B transition. During the terminus of the upper RPI minimum, a directional change of about 180 ◦ occurred at an extremely fast rate, estimated to be less than 2 ◦ per year, with no intermediate virtual geomagnetic poles (VGPs) documented during the transit from the southern to northern hemisphere. Thus, the entry into the Brunhes Normal Chron as represented by the palaeomagnetic directions and VGPs developed in a time interval comparable to the duration of an average human life, which is an order of magnitude more rapid than suggested by current models.
The reported investigation therefore provides high-resolution integrated palaeomagnetic and radioisotopic data that document the fine details of the anatomy and tempo of the M-B transition in Central Italy that in turn are crucial for a better understanding of Earth’s magnetic field, and for the development of more sophisticated models that are able to describe its global
structure and behaviour.
Description:
Published
Description:
1110-1124
Description:
1A. Geomagnetismo e Paleomagnetismo
Description:
JCR Journal
Description:
restricted
Keywords:
geomagnetic field reversal
;
magnetostratigraphy
;
Matuyama-Brunhes (M-B) transition
;
04. Solid Earth::04.05. Geomagnetism::04.05.02. Geomagnetic field variations and reversals
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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