Jökull - 01.01.2009, Blaðsíða 53

Holocene sediment- and paleo-magnetic characteristics from the Iceland and E-Greenland margins
Table 1: Core locations and water depths. Cores 1205 to 1232 represent JM96-cores whereas the remaining
cores were taken in the B997-cruise. –Staðsetning kjarna og sjávardýpi. Kjarnar 1205 til 1232 eiga við kjarna
tekna í JM96 leiðangrinum en aðrir kjarnar voru teknir í B997 leiðangrinum.
Core ID Longitude Latitude Water depth Core length Basal date SAR
(m) (cm) (ka) (cm/ky)
1205 -27.84 68.071 549 507 9.22 55.5
1207 -29.35 68.100 404 324 9.8 33.1
1213 -30.96 67.288 557 475 13.83 34.3
1214 -30.97 67.300 574 564 11.38 49.6
1215 -30.86 67.047 668 587 12.9 45.5
1216 -30.63 65.963 478 246 12.04 20.4
1232 -24.00 66.617 215 279 9.06 30.8
317 -18.86 66.587 494 254 12.27 20.7
321 -18.97 66.891 480 295 7.54 39.1
324 -21.15 66.523 282 283 9.72 29.1
330 -21.08 65.870 165 540 9.42 57.3
335 -24.18 66.686 239 428 10.36 41.3
336 -24.16 66.686 242 501 13.68 36.6
339 -22.80 66.016 104 527 10.45 50.4
342 -22.86 66.258 94 440 9.27 47.5
347 -24.48 63.928 321 480 10.73 44.7
The average rate of sediment accumulation (SAR)
at the core sites is tightly grouped with a mean value
of 40±11 cm/ky and a range between !57 and 20
cm/ky (Table 1); there is no distinct regional SAR
differences between the Icelandic and East Greenland
margins. The slow rate of accumulation at #1216, at
the East Greenland shelf break, is an outlier, but is
consistent with other data from the area (Stein, 1996).
These results indicate that any differences in magnetic
properties cannot be ascribed to differences in the rate
of sediment accumulation.
MEASUREMENT METHODS
All the cores were subject to on-board whole core
magnetic susceptibility (WCMS, SI x 10"5) analy-
ses using a Bartington MS2 system with two differ-
ent diameter loops. The 10-cm-diameter JM96 cores
were measured at 5 cm intervals, whereas the 7-cm-
diameter B997 cores were measured at 3 cm inter-
vals. The cores were shipped to INSTAAR where
they were kept at a constant 4 !C temperature prior
to splitting, description, and photographing. Samples
were obtained for sedimentological analyses at 3–5
cm intervals. Mass susceptibility was measured using
10 cc cubes and dried sediment (massMS as 10"7m3
kg"1) and a Bartington MS2 instrument (Walden et
al., 1999). Finally, the individual core sections were
sampled with a 2 x 2 cm u-channel in either 100-cm
or 150-cm sections.
Magnetic analyses were performed on the sed-
iment in the u-channels at Paleomagnetism Labo-
ratory at University of California at Davis (UCD).
The instrument used was a 2G Enterprises Model
755R long-core cryogenic magnetometer. The mea-
surements were performed at 1 cm interval. The u-
channels were 100 cm long for the JM96 cores and
150 cm in length for the B997 cores. The system is
sensitive to the ends of the channels where measures
of magnetic intensity sharply decrease over an inter-
JÖKULL No. 59 53