Open AccessPaleoproterozoic Geomagnetic Field Strength From the Avanavero Mafic Sills, Amazonian Craton, Brazil
Author(s) -
Di Chiara A.,
Muxworthy A. R.,
Trindade R. I. F.,
BispoSantos F.
Publication year - 2017
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1002/2017gc007175
Subject(s) - mafic , geology , craton , sill , amazonian , earth's magnetic field , geochemistry , petrology , paleontology , tectonics , amazon rainforest , magnetic field , ecology , physics , quantum mechanics , biology
A recent hypothesis has suggested that Earth's inner core nucleated during the Mesoproterozoic, as evidenced by a rapid increase in the paleointensity (ancient geomagnetic field intensity) record; however, paleointensity data during the Paleoproterozoic and Mesoproterozoic period are limited. To address this problem, we have determined paleointensity from samples from three Paleoproterozoic Avanavero mafic sills (Amazonian Craton, Brazil): Cotingo, 1,782 Ma, Puiuà, 1,788 Ma, and Pedra Preta, 1,795 Ma. We adopted a multiprotocol approach for paleointensity estimates combining Thellier‐type IZZI and LTD‐IZZI methods, and the nonheating Preisach protocol. We obtained an average VDM value of 1.3 ± 0.7 × 10 22 Am 2 (Cotingo) of 2.0 ± 0.4 × 10 22 Am 2 (Puiuà) and 6 ± 4 × 10 22 Am 2 (Pedra Preta); it is argued that the Cotingo estimate is the most robust. Our results are the first data from the upper Paleoproterozoic for South America and are comparable to data available from other regions and similar periods. The new data do not invalidate the hypothesis of that Earth's inner core nucleated during the Mesoproterozoic.