Open AccessIntensity of the Earth's magnetic field since Precambrian from Thellier‐type palaeointensity data and inferences on the thermal history of the core
Author(s) -
Prévot Michel,
Perrin Mireille
Publication year - 1992
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.1992.tb04640.x
Subject(s) - geology , precambrian , dynamo theory , dynamo , geophysics , paleomagnetism , inner core , dipole , secular variation , core–mantle boundary , mantle (geology) , paleontology , magnetic field , physics , quantum mechanics
SUMMARY We present a compilation of palaeointensity data obtained by the Thellier method from magmatic rocks up to 3.5 Gyr old. No apparent very long‐term variation occurs from present to Early Precambrian. The overall data are compatible with a gravitationally powered dynamo model in which the inner core is some 4.0 Gyr old. However, palaeointensity data are still too incomplete to dismiss the possibility of a more complex field history with a geodynamo first thermally driven then gravitationally powered. Despite the limited number of data currently available, large differences in the dipole field moment are clearly documented with a time‐scale of the order of 50‐100 Myr. The changes in intensity can be due to repetitive instabilities of the thermal boundary layer at the base of the mantle.