Jökull - 01.01.2009, Side 51

Reviewed research article
A comparison of Holocene sediment- and paleo-magnetic
characteristics from the margins of Iceland and East Greenland
John T. Andrews1 and Jórunn Harðardóttir2
1Institute of Arctic and Alpine Research and Department of Geological Sciences, Box 450,
University of Colorado, Boulder, CO 80309, USA
email: andrewsj@colorado.edu
2Icelandic Meteorological Office, Bústaðavegur 9, IS-150 Reykjavík, Iceland
jorunn@vedur.is
Abstract — We present environmental and paleo-magnetic data from sixteen cores from either side of the
Denmark Strait; six are from East Greenland and the remainder from the SW, NW, and N Iceland shelf. The
bedrock geology in both regions mainly consists of Tertiary and Quaternary basalts. The cores were sampled by
u-channels and processed in a cryogenic magnetometer at 1-cm intervals; in addition we measured whole core
and discrete sample mass magnetic susceptibility. For eight cores we also have quantitative weight% measure-
ments of magnetite, hematite, and quartz. We restrict our analyses to the last 10,000 14C yrs BP and present the
spatial variability of the median, standard deviation, and coefficient of variation on magnetic parameters that
reflect changes in concentration, grain-size, and mineralogy, based on a sediment volume basis. Our results
show a consistent difference in terms of median values and coefficient of variation between East Greenland
versus Icelandic sediments in terms of several magnetic properties. In particular the sediments from Iceland
have lower mass magnetic and anhysteretic susceptibilities, and lower and more variable median destructive
fields. In part this is attributable to higher values of carbonate and volcanic glass in Icelandic sediments.
Magnetic grain-size is usually coarser in Iceland sediments, especially in sites from Vestfirðir. Paleomagnetic
measurements revealed that the maximum angular deviations (MAD) are small for East Greenland sediments
(<5!) and higher and more variable for the Iceland sediments, but still generally <10 !. Normalized intensity
and inclination are more uniform across the area, with a median inclination value of 73 ! at all sites compared
to an expected geocentric dipole value of 77!.
INTRODUCTION
Scientific investigation in and on both sides of the
Denmark Strait between Iceland and Greenland has
intensified during the last decade. This region has, in
many studies, been portrayed as one of the key re-
gions for studies of past and present environments,
including research in the marine, terrestrial, lacus-
trine, and glacial environments. The environments
on either side of the Denmark Strait are very dis-
similar – with the East Greenland margin being po-
lar in character with extensive glacier and sea-ice,
whereas the Iceland margin is influenced by the rela-
tively warm Irminger Current (Stefánsson, 1962), was
totally deglaciated by ca. 13 ka BP, and any influence
from extensive land ice had disappeared by 9 ka BP
(Norðdahl, 1990; Geirsdóttir et al., 1997). Tertiary
and Quaternary flood basalts dominate the bedrock
geology of both areas (Larsen, 1983) thus imposing
a broad mineralogical control on magnetic sediment
properties.
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