TY - JOUR
T1 - The geomagnetic field during the Cretaceous Normal superchron from marine magnetic anomalies
AU - Granot, R
AU - Dyment, J
AU - Gallet, Y
PY - 2011
Y1 - 2011
N2 - Superchrons are remarkable geomagnetic field features during which the polarity remained stable for several tens of Myr. The latest interval to experience steady polarity, the Cretaceous Normal superchron (CNS, between ~121 and 83 Myr ago), is best expressed above the oceanic crust where sea surface magnetic anomalies lack a prominent stripe pattern. Here we show, using the first deep-tow magnetic profile encompassing the entire CNS, together with widely-distributed sea surface magnetic anomaly data, that the variability of the dipolar geomagnetic field increased at the beginning of the superchron, leading to a period of highly fluctuating field between 110 and 100 Myr ago. A transition back to a more stable field resulted in a subdued magnetic signal in the last 9 Myr of the superchron. This long-term pattern requires that the conditions at the core-mantle boundary have significantly varied during the superchron. Besides their geomagnetic implications, our results provide new time markers to re-evaluate seafloor-spreading history during the CNS, when important plate reorganizations took place and ultrahigh spreading rates have been speculated but not directly confirmed.
AB - Superchrons are remarkable geomagnetic field features during which the polarity remained stable for several tens of Myr. The latest interval to experience steady polarity, the Cretaceous Normal superchron (CNS, between ~121 and 83 Myr ago), is best expressed above the oceanic crust where sea surface magnetic anomalies lack a prominent stripe pattern. Here we show, using the first deep-tow magnetic profile encompassing the entire CNS, together with widely-distributed sea surface magnetic anomaly data, that the variability of the dipolar geomagnetic field increased at the beginning of the superchron, leading to a period of highly fluctuating field between 110 and 100 Myr ago. A transition back to a more stable field resulted in a subdued magnetic signal in the last 9 Myr of the superchron. This long-term pattern requires that the conditions at the core-mantle boundary have significantly varied during the superchron. Besides their geomagnetic implications, our results provide new time markers to re-evaluate seafloor-spreading history during the CNS, when important plate reorganizations took place and ultrahigh spreading rates have been speculated but not directly confirmed.
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JO - Geophysical Research Abstracts
JF - Geophysical Research Abstracts
SN - 1029-7006
ER -