A paleomagnetic record of the last 640 kyr from an eastern Mediterranean piston core and a review of geomagnetic excursions in the Brunhes

Details A paleomagnetic record of the last 640 kyr from an eastern Mediterranean piston core and a review of geomagnetic excursions in the Brunhes A paleomagnetic record of the last 640 kyr from an eastern Mediterranean piston core and a review of geomagnetic excursions in the Brunhes

Dec 2004

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004agufmgp41b..08o&link_type=abstract

American Geophysical Union, Fall Meeting 2004, abstract #GP41B-08

Astronomy and Astrophysics

Astronomy

1513 Geomagnetic Excursions, 1520 Magnetostratigraphy

Scientific paper

Core KC01 (25.93 m long) was taken from a small ridge on the lower slope of the southern Calabrian Ridge (Pisano Plateau, 36deg15.25'N, 17deg44.34'E, 3643m water depth) during cruise MD69 of the French R/V Marion Dufresne in June-July 1991. The sediment consists of hemipelagic sediments with intercalated sapropel and tephra layers. They form an alternation of grey, greenish, olive-coloured, yellowish, white and beige shades. Sapropel layers are black to dark green. Paleomagnetic samples (6.4 cm3 cubes) were taken from the half split cores and measurements of the natural remanent magnetization was conducted at Utrecht University with a DC SQUID magnetometer (2G Enterprises model 740-R). Stepwise alternating field demagnetization was done at 8-11 steps up to 60-80 mT on each sample. Core KC01 (37.04 m long) was taken as a companion core from core KC01B at the same locality, earlier subjected to magnetostratigraphic work (Langereis et al., 1997). Langereis et al. (1997) established an age model based on the matching of (ghost-)sapropels with insolation minima. They applied the 65degN summer insolation calculated from the astronomical solution La90 (Laskar 1990; Laskar et al., 1993) as target curve and included a time lag of 3-kyr - based on the age difference between the radiocarbon dated midpoint of S1 at 8.5 ka and the insolation maximum at 11.5 ka following the method by Lourens et al. (1996). Lourens (2004) modified the astronomical chronology established by Langereis et al. (1997) and investigated the sapropel chronology on KC01B and KC01 based on high resolution colour correlation with ODP Site 964, which is 1 km away, and constructed an improved age model, which gives a better estimate for these two cores. Langereis et al. (1997) reported four excursions (CR0, CR1, CR2, CR3) with ages of 261, 318, 515, and 573 ka based on the chronology of sapropels on Core KC01B. Lourens (2004) revised the chronology of Core KC01B and redated the excursions as 260, 319, 543, and 593 ka. In this study, these four excursion records were confirmed and dated as 258-263, 313-319, 541-542, 592-594 ka based on the new chronology. Also Laschamp, Norwegian-Greenland Sea, Iceland Basin and Jamaica excursions were found at ages of 41-43, 77, 193-194 and 212-213 ka. Finally, we conducted a review of published excursion records and identified a maximum of 23 excursions and a minimum of 16 excursions in the Brunhes.

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