HR: 1340h
AN: GP23A-0029    [Abstracts]
TI: The Cretaceous Quiet Zone: How Quiet?
AU: Gallet, Y
EM: gallet@ipgp.jussieu.fr
AF: CNRS UMR 7154, Institut de Physique du Globe de Paris, 4 place Jussieu, Paris, 75005 France
AU: * Dyment, J
EM: jdy@ipgp.jussieu.fr
AF: CNRS UMR 7154, Institut de Physique du Globe de Paris, 4 place Jussieu, Paris, 75005 France
AU: Kitazawa, M
EM: mitsu@ipgp.jussieu.fr
AF: CNRS UMR 7154, Institut de Physique du Globe de Paris, 4 place Jussieu, Paris, 75005 France
AU: Bouligand, C
EM: bouligan@ipgp.jussieu.fr
AF: CNRS UMR 7154, Institut de Physique du Globe de Paris, 4 place Jussieu, Paris, 75005 France
AU: Hoise, E
EM: hoise @ipgp.jussieu.fr
AF: CNRS UMR 7154, Institut de Physique du Globe de Paris, 4 place Jussieu, Paris, 75005 France
AU: Kim, M
EM: moon20@snu.ac.kr
AF: Seoul National University, School of Earth and Environmental Sciences, Bld 25-1, Room 318, Sillim-dong, Gwanak-gu, Seoul, 151-747 Korea, Republic of
AU: Savary, J
EM: savary@ipgp.jussieu.fr
AF: CNRS UMR 7154, Institut de Physique du Globe de Paris, 4 place Jussieu, Paris, 75005 France
AU: Royer, J
EM: jyroyer@univ-brest.fr
AF: CNRS UMR 6538 Domaines oceaniques, Intitut Universitaire Europeen de la Mer, Universite de Bretagne Occidentale, 1 place N. Copernic, Plouzane, 29280 France
AU: Choi-Dyment, Y
EM: choi@ipgp.jussieu.fr
AF: CNRS UMR 7154, Institut de Physique du Globe de Paris, 4 place Jussieu, Paris, 75005 France
AU: Gotab, B
EM: gotab@ipgp.jussieu.fr
AF: CNRS UMR 7154, Institut de Physique du Globe de Paris, 4 place Jussieu, Paris, 75005 France
AB: Geomagnetic field intensity variations deduced from magnetostratigraphic data are mainly restricted to the past few million years. As a consequence, many important questions, such as the long-term evolution of the geomagnetic field intensity and the temporal distribution of excursions, remain unsolved yet. The possibility to recover these fluctuations over a long time interval from marine magnetic anomalies is therefore of particular interest. Within the period documented by these anomalies, the Cretaceous Normal Superchron (CNS) presents a major interest in geomagnetism as little is known on the characteristics of the geomagnetic field during this event, except that it apparently did not reverse for about 35 Myr. Cruise Magofond 3 of R/V Suroit (July-August 2005) was dedicated to the CNS, with a target area on the Cretaceous Quiet Zone off Western Africa, on the eastern flank of the Mid-Atlantic Ridge. Both sea-surface and deep tow magnetic anomaly profiles have been collected. Magnetic observatory data from M'Bour (Senegal) and Guimar (Canary Islands) have been regularly transmitted to the ship in order to check for any external magnetic field disturbance which may have affected the data. In addition, seismic reflection data were acquired to insure that the observed anomalies are not caused by the basement topography and, eventually, to estimate and correct such an effect. Altogether, these data brings new constraints on the variability of the geomagnetic field during the superchron. As a preliminary result, they show the occurrence of several consistent short-wavelength magnetic anomalies which may be linked either to short reversed polarity intervals or to excursions. In particular, the ISEA reversed polarity subchron at the beginning of the CNS seems to be present in most profiles. Other observed anomalies may also depict subchrons and would therefore challenge the concept of a non-reversing geodynamo during the exceptionally long CNS.
DE: 1513 Geomagnetic excursions
DE: 1522 Paleomagnetic secular variation
DE: 1535 Reversals: process, timescale, magnetostratigraphy
DE: 1550 Spatial variations attributed to seafloor spreading (3005)
DE: 1560 Time variations: secular and longer
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005