Jökull - 01.01.2009, Page 60

J. T. Andrews and J. Harðardóttir
Figure 4. Biplot of the scores on the first two PC
axes on the sediment magnetic variables (Table 2). –
Punktarit sem sýnir gildi fyrstu tveggja höfuðþátta-
ásanna (PC) á setsegulsbreyturnar (tafla 2).
Figure 5. Cluster diagram of the 16 sites based on the
six magnetic parameters (Appendix 2). A, B and C re-
fer to groupings of the data. –Klasamynd af stöðunum
16 sem byggir á segulkennistærðunum sex (Viðauki
1). A, B og C eiga við flokkun gagnanna.
CONCLUSIONS
Data are presented from 16 cores in terms of median
values, standard deviations, and coefficient of varia-
tion. An analysis of the median values of a number of
environmental and paleo-magnetic characteristics of
gravity and piston cores from the East Greenland and
West/North Iceland margins show systematic differ-
ences in several of the environmental magnetic vari-
ables between the two areas. Even though the sedi-
ments in both areas are derived principally from ero-
sion of basaltic rock the lower mass susceptibility on
the Icelandic margin is caused by higher carbonate
and TOC, which, together with high wt% of amor-
phous silica (glass), dilutes the magnetic susceptibil-
ity response. These same Icelandic sediments also
tend to have a higher ratio of ARM(J0)/ARM(J20)
than their East Greenland counterparts (= coarser sed-
iments). Physical grain size tends to be slightly
greater on the Iceland margin than the East Green-
land margin, probably to a large extent due to frequent
coarse-grained tephra deposition on the Iceland shelf
and possibly more wave action on the shallow banks.
The coefficients of variations are systematically lower
on the East Greenland margin than their counterparts
from Iceland suggesting that the input of glacially de-
rived sediment has been relatively consistent during
the Holocene. Paleomagnetic variables, such as nor-
malized intensity and the median inclination show no
such spatial variation, suggesting that these are true
regional parameters.
How far changes in the various variables discussed
above coincide in the time-domain is, of course, an
important question. Our data will be available for
such analyses.
Acknowledgements
The research was supported by grants from NSF-
OPP-972510 and -0004233, and ATM-9531397,
and grants from the Iceland Research Council
(981870098, 981870099, and 991440099) to Dr Ás-
laug Geirsdóttir. We are grateful to the staff at the
UC-Davis Cryogenic Magnetometer Facility for their
assistance to Harðardóttir. We thank Drs Frank Hall
and JohnWalden for commenting on a draft of this pa-
per; Dr J. Stoner provided advice during completion
of the final version. Anonymous referees are thanked
for their comments and assistance in improving the fi-
nal manuscript. The NRM, ARM, and IRM data from
the cores will be deposited in the NOAA Paleoclimate
databases (www.ngdc.noaa.gov/paleo/data.html).
60 JÖKULL No. 59