5:15 PM - 7:15 PM
[SEM16-P06] Variation in paleodirection during a period of high reversal rate deduced from lava flows in eastern Iceland-a new report from the Seyðisfjörður region lava flows
The Earth’s magnetic field has been frequently reversing between normal polarity and reversed polarity at various time intervals, and the history of these reversals has been known back to 160 million years ago (e.g. Ogg, 2020). On the other hand, the history of variation in paleomagnetic intensity and the range of variation in paleomagnetic direction, which change significantly even during the same polarity period, remain largely unclear. Elucidating such behavior of the paleomagnetic field by focusing on the temporal evolution of reversal frequency is important for a deeper understanding of the essential property of the geo dynamo that produces the Earth’s magnetic field.
The highest reversal frequency since the Cretaceous was reported about, 11 million years ago, with a reversal frequency of 4.7 per million years(a period of high reversal rate).Variations in paleomagnetic direction involve this period have been reported from lava flows in eastern Iceland (Kristjansson et al., 1995), where lava with intermediate polarity is relatively common in the Mjoifjördur region. We have a total of 66 lava samples with clear stratigraphic relationships that were systematically collected from two adjacent sections(EP,EO) and conducted various analyses. To date,we have completed stepwise AF demagnetization analysis on each of the five specimens from each lava and clarified the paleomagnetic declination variations. As a result, it is becoming apparent that the virtual geomagnetic pole(VGP) tended to vary over a much lower latitude range than that at present, and the possibility that the geo dynamo at that time may have been of a relatively unstable property was reported in Koremura et al. (2024JpGU). Additionally, rock magnetic analysis confirmed that the paleomagnetic direction recorded in these samples are independent of the rock magnetic properties (Koremura et al., 2024SGEPSS).
In this study, paleomagnetic core samples were systematically collected from a total of 72 lavas spanning two new sections (ET,ES) in the Seyðisfjörður region, located northern side of the Mjoifjördur ragion on the same peninsula, in order to elucidate variation in paleomagnetic direction. According to the geological map published by the Icelandic Institute of Natural History, the ES section is considered to be stratigraphically upper than the EP section. Together with the previous results, we will report paleomagnetic direction variations for a total of four sections(ET,ES,EP and EO), and discuss the longer time scale variation in paleomagnetic direction during the high reversal rate period.
The highest reversal frequency since the Cretaceous was reported about, 11 million years ago, with a reversal frequency of 4.7 per million years(a period of high reversal rate).Variations in paleomagnetic direction involve this period have been reported from lava flows in eastern Iceland (Kristjansson et al., 1995), where lava with intermediate polarity is relatively common in the Mjoifjördur region. We have a total of 66 lava samples with clear stratigraphic relationships that were systematically collected from two adjacent sections(EP,EO) and conducted various analyses. To date,we have completed stepwise AF demagnetization analysis on each of the five specimens from each lava and clarified the paleomagnetic declination variations. As a result, it is becoming apparent that the virtual geomagnetic pole(VGP) tended to vary over a much lower latitude range than that at present, and the possibility that the geo dynamo at that time may have been of a relatively unstable property was reported in Koremura et al. (2024JpGU). Additionally, rock magnetic analysis confirmed that the paleomagnetic direction recorded in these samples are independent of the rock magnetic properties (Koremura et al., 2024SGEPSS).
In this study, paleomagnetic core samples were systematically collected from a total of 72 lavas spanning two new sections (ET,ES) in the Seyðisfjörður region, located northern side of the Mjoifjördur ragion on the same peninsula, in order to elucidate variation in paleomagnetic direction. According to the geological map published by the Icelandic Institute of Natural History, the ES section is considered to be stratigraphically upper than the EP section. Together with the previous results, we will report paleomagnetic direction variations for a total of four sections(ET,ES,EP and EO), and discuss the longer time scale variation in paleomagnetic direction during the high reversal rate period.