scholarly journals Geomagnetic polarity reversal model of deep-tow profiles from the Pacific Jurassic Quiet Zone

1998 ◽  
Vol 103 (B3) ◽  
pp. 5269-5286 ◽  
Author(s):  
William W. Sager ◽  
Chester J. Weiss ◽  
Maurice A. Tivey ◽  
H. Paul Johnson
Keyword(s):  
Polarity Reversal ◽  
The Pacific ◽  
Geomagnetic Polarity

Magnetite magnetofossils record biogeochemical remanent magnetization in hydrogenetic ferromanganese crusts

Geology ◽  
2020 ◽  
Vol 48 (3) ◽  
pp. 298-302 ◽  
Author(s):  
Wei Yuan ◽  
Huaiyang Zhou ◽  
Zhenyu Yang ◽  
James R. Hein ◽  
Qunhui Yang
Keyword(s):  
Remanent Magnetization ◽  
Deep Ocean ◽  
Natural Remanent Magnetization ◽  
Paramagnetic Resonance ◽  
Ferromanganese Crusts ◽  
Transmission Electron ◽  
The Pacific ◽  
Genetic Mechanisms ◽  
Geomagnetic Polarity ◽  
Fine Resolution

Abstract Records of natural remanent magnetization (NRM) and geomagnetic polarity reversals preserved within ferromanganese (Fe-Mn) crusts, together with the application of fine-resolution magnetostratigraphic analysis, have been successfully demonstrated. However, because Fe-bearing precipitates or minerals are thought to be either oxides and/or hydroxides precipitated from ambient oxic seawater or detrital minerals, the magnetic properties of the ferromagnetic minerals and the genetic mechanisms remain controversial; moreover, the origin of the NRM is unclear. Here, we show that nanometer-scale magnetite crystals found in Fe-Mn crusts from the Pacific Ocean and South China Sea are magnetosome fossils based on their narrow size range, chain arrangement, chemical purity, and crystallographic perfection, as indicated by transmission electron microscopy. Furthermore, our new data from rock magnetic and electron paramagnetic resonance analyses, combined with a previously reported micro-magnetostratigraphic sequence, indicate that magnetotactic bacteria and their post-mortem remains contribute to a biogeochemical remanent magnetization of Fe-Mn crusts. In addition, the results provide evidence for a previously unappreciated pathway for the biogeochemical cycling of iron in the deep ocean.

scholarly journals Refined magnetostratigraphic position of the Shyrokyne unit in loess sequences from Central Ukraine

2019 ◽  
Vol 28 (2) ◽  
pp. 301-312
Author(s):  
D. V. Hlavatskyi
Keyword(s):  
Transition Zone ◽  
Careful Analysis ◽  
Magnetic Polarity ◽  
Polarity Reversal ◽  
Preliminary Results ◽  
Soil Complex ◽  
Lowermost Part ◽  
Geomagnetic Polarity

The youngest geomagnetic polarity reversal, the Matuyama–Brunhes boundary (MBB), which occurred 780 kyr ago, is a “golden spike” in the age calibration of sediment sequences. The use of palaeomagnetic method as a stratigraphic tool in the study of loess sequences from Ukraine originated some 50 years ago. One major problem in using the available data is the contradictory position of the MBB in different stratigraphic units, which affected historic evolution of thechronostratigraphic models of the Quaternary in Ukraine. The most important units in this regard are the Shyrokyne and Martonosha units, in which the MBB had been defined most often. This paper provides the careful analysis of the previous magnetostratigraphic data and new preliminary results from key loess-palaeosol sections in Central Ukraine. Shyrokyne palaeosol complex in four loesspalaeosol sections located in the Middle Dnieper and Podolia regions has been palaeomagnetically studied. It is shown that the transition zone of the Matuyama–Brunhes palaeomagnetic reversal is most likely located at the base of the soil complex. In the Vyazivok section the MBB has been found in the lowermost part of Shyrokyne palaeosol sh1. Preliminary palaeomagnetic studies of theStari Kaydaky section reveal that the MBB cannot be defined at least above sh1 subunit. Medzhybizh and Holovchyntsi sections were deposited after the Matuyama–Brunhes reversal; however, the palaeomagnetic informativeness of the part of studied strata is doubtful. Magnetostratigraphic position of the Shyrokyne unit below the MBB in some previous studies is explained by methodological reasons and inconsistent chronostratigraphic models. The paper substantiates that normal magnetic polarity zone in the Pryazovya loess and upper part of the Shyrokyne soil is not associated with the influence of secondary processes on the palaeomagnetic record.

K–Ar and 40Ar/39Ar Age of the Laschamp geomagnetic polarity reversal

Nature ◽  
1978 ◽  
Vol 274 (5670) ◽  
pp. 462-464 ◽  
Author(s):  
CHRIS M. HALL ◽  
DEREK YORK
Keyword(s):  
Polarity Reversal ◽  
Geomagnetic Polarity
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