Jökull - 01.12.1993, Blaðsíða 21

wood by eskimos on the coasts of St. Lawrence Island
which made it possible to (a) date Eskimo sites, (b)
to detect the source of the driftwood, and (c) to ex-
tend the previous living tree-ring chronologies from
the Alaskan interior further back in time. When this
extension was achieved Giddings realised the possi-
bility to use the driftwood dates as an aid to map the
Arctic sea currents (Giddings 1941 and 1943). Later
on he found that logs from the shores west of Point
Barrow, on the north coast of Alaska, had a tree-ring
pattern restricted to the Yukon region, and that east of
Point B arrow the driftwood had a similar pattern as the
trees from the Mackenzie delta. From this compari-
son he was able to map the coastal currents (Giddings,
1952).
Oswalt (1951) was able to trace the origin of drift-
wood logs at Hooper Bay, Alaska by cross-dating them
with his own samples from the lower Yukon River and
with Gidding’s (1941) living tree-ring chronologies
from the Alaskan interior. Van Stone (1958) made
similar studies on the Nunivak Island driftwood, to
provide additional information for the study of ocean
currents in the Bering Sea.
Bartholin and Hjort (1987) analysed driftwood
from Isfjorden on the west coast of Spitsbergen, to
further evaluate the potential for constructing den-
drochronological series on Arctic driftwood samples.
They were able to date most of the logs, via master
chronologies from the Arkhangelsk region and their
work showed the potential of further tree-ring studies
on Arctic driftwood and provided the impetus for the
present study.
Eggertsson (1994a) made a study on the origin of
the Mackenzie river driftwood and was able to identify
and date American driftwood in collections from the
coasts of Greenland. Eggertsson (1994b) also stud-
ied the origin of the driftwood on the northern coast
°f Spitsbergen, and compared his results with those
°f Bartholin and Hjort (1987), gaining information
°n changes in the relative influence of the currents -
Atlantic versus Transpolar - in the Svalbard area.
DRIFTWOOD FROM RAISED BEACHES
When studying the isostatic rebound after the last
glaciation and Holocene eustatic transgressions in the
Arctic, driftwood on raised beaches is commonly
dated along with bones and molluscs by the Carbon-
14 method (e.g. Blake, 1972; Salvigsen, 1981). The
decomposition of driftwood is slow in the dry and
cold arctic climate and it is therefore commonly pre-
served. Driftwood is preferred as a dating material
because bones and molluscs often give too old ages,
due to contamination of the marine samples with old
carbon. The mollusc and other marine animal datings
thus have to be corrected for a marine reservoir effect
(e.g. Mangerud and Gulliksen 1975; Salvigsen, 1978).
The oldest post-glacial driftwood dates from Sval-
bard range from 9800 to 9500 14C years BP, and come
from a beach on Kong Karls Land situated 100 m
a.s.l. (Salvigsen, 1981). Driftwood dates ranging
from 8800-8500 BP have also been reported from high
beaches on the Arctic islands of Canada (Blake, 1972;
Stewart and England, 1983). These dates indicate the
early re-establishment of the boreal forest after the last
glaciation.
In Iceland, "old" driftwood logs are commonly
detected when digging drainage ditches on the lowland
(Kristjánsson, 1980), but no datings have been carried
out on such material. The most common driftwood
taxa present on the raised beaches of the Arctic are:
Larix, Picea, Salix and Populus. Pinus is rare in these
old driftwood collections.
Parker et al. (1983) applied dendrochronological
studies on driftwood from raised beaches on the Hud-
son Bay coast in Canada, for examining the potential
for extending the living tree-ring records from the area
by dating driftwood. Almost all samples obtained
from the youngest beaches could be dated, extend-
ing the tree-ring record for the area back 50 years to
1656. However, none of the driftwood samples from
the older beaches fitted into the living tree-ring record.
Driftwood deposited at the margins of glacier-
dammed lakes have been dated by matching the tree
rings in the driftwood with those of nearby living old
trees. An example of this was the study of Clague et
al. (1982) who reconstructed the history of filling and
emptying of a former glacial-dammed lake in south-
western Yukon Territory, Canada.
JÖKULL, No. 43,1993 19