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an increase to 11 months year
1
within that interval. The
impact of the meltwater flow on SST appears to be rather
small with a 3°C difference.
Reconstructions for core 12 (Figure 13) show a drop in
temperature between 680 and 720 cm, just before the level
dated at 8.26 ka and another decline immediately after that
(560
(core DA80004-33 [Scott et al., 1984]), maximum I. minu-
tum values similar to those of core 12 at the time of the 8.2 ka
event are observed. In Cabot Strait core 111 [de Vernal et al.,
1993], I. minutum is present, but adequate chronology is
lacking, and it is not possible to correlate it to the Agassiz
drainage. The change in dinocyst assemblages corresponds
to a 1
640 cm). These drops in SST are between 2°C and 3°C.
August SSS also shows small drops of 1
‰-
2
‰
in nearby
intervals. The sea ice cover duration would have been longer
by 1
-
drop in August SSS around 8.2 ka in La Have
Basin and in Bay of Islands [Levac, 2001, 2003]. In La Have
Basin, the Agassiz
‰-
2
‰
flood also marks the end of the Holocene
optimum in SST, during which SST was at least 5°C higher
than present [Levac, 2001]. This was possibly the result of a
more northerly path of the Gulf Stream in the early Holocene
[Levac, 2001] as also proposed by Keigwin et al. [2005].
2 months during the interval with lowered temperature
and salinity.
-
6. DISCUSSION
The recognition of an AG-aged DC layer in core 19 [Miller
et al., 2006] and coincident changes in dinoflagellate cyst
assemblages in both cores 12 and 19, indicate shifts to
colder, fresher, surface waters. Combined with previously
published paleoceanographic data from other sites in the
area, there is strong evidence that the Lake Agassiz meltwa-
ter outburst transited via the Labrador Current [Lewis and
Miller, 2005; Lewis et al., 2009] and had a significant impact
on sea surface conditions along the eastern Canadian margin.
6.2. Evidence From Foraminiferal and Isotopic Records
The meltwater drainage has been reported in other offshore
planktic foraminiferal and
18
O isotope records. Low iso-
topic values, coincident with the drainage of Lake Agassiz,
are recorded in cores from the Laurentian Fan, Nova Scotia
rise, and as far south as Cape Hatteras [Keigwin and Jones,
1995, Keigwin et al., 2005]. Isotopic records from Cart-
wright Saddle on the Labrador Shelf show slight shifts that
may indicate the AG meltwater pulse, but there is no evi-
dence of it in records from the Labrador Sea [Andrews et al.,
1999; Hillaire-Marcel et al., 2007]. Similar records are not
available for the Scotian Shelf because planktic foraminifera
are affected by dissolution in that region [Scott et al., 1984].
On the Northeast Newfoundland Shelf, benthic forami-
niferal evidence from core 07 indicates bottom water mass
changes and increased stratification in outer Notre Dame
Channel at the time of both the AG-aged meltwater in
δ
6.1. Impact of Fresh Water on Dinoflagellate
Cyst Assemblages
The significant changes in dinoflagellate cyst assemblages
within DC layers of core 19, especially those occurring
within the DC layer coeval with the Agassiz outburst, clearly
indicate that the meltwater flow over Notre Dame Channel
impacted sea surface conditions. Increases in the percent
occurrences of Arctic taxa (e.g., I. pallidum) and of other
taxa indicative of greater water stratification (in this case A.
tamarense) correspond to an approximately 10
uxes
and at the time of deposition of the underlying DC bed
[Miller, 1999; Miller et al., 2006]. A unique fauna charac-
terized by Melonis barleeanum, Cassidulina carinata, and
Pullenia spp (Pullenia osloensis, Pullenia quinqueloba, and
Pullenia bulloides) suddenly appear (and disappear) twice
in intervals that correlate closely to the AG DC bed and the
DC bed below. Enhanced
lowering
of SSS. Farther south, on the Scotian Shelf, Arctic taxa such
as I. pallidum are far less abundant, and cold conditions are
indicated instead by high percentages of I. minutum. In core
12, a peak in I. minutum is centered at 640 cm, dated 8.26
ka, that corresponds to a 2°C
-
3°C drop in SST and a 1
‰-
2
‰
flux of the Labrador Current
moving south over the upper slope could have laterally
over
‰
drop in salinity, as determined by the transfer functions.
Changes in dino
owed the shelf-edge sill and carried the indigenous
slope fauna with it into the deep shelf basin. With subse-
quent flux reduction, freshened waters were isolated in the
basins, which then mixed with overlying waters and de-
creased shelf water salinities. The upper slope benthic
fauna was replaced with an assemblage characterized by
hyposaline-tolerant species, notably Islandiella spp (Islan-
diella helenae and Islandiella norcrossi) and increases in
Stainforthia spp (Stainforthia complexa, Stainforthia con-
cave, and Stainforthia pauciloculata)[Miller, 1999; Miller
et al., 2001]. Bottom water salinities gradually returned to
agellate cyst assemblages around the
time of the 8.2 ka event, consistent with lower SSS and
stronger strati
cation, are also observed in other palynolog-
ical records on the southeast Canadian margin. Increased
percentages of Arctic taxon I. pallidum, as seen in core 19,
are recorded in core HU03033-03 on the Scotian Slope
(E. Levac, unpublished data, 2009) and in Bay of Islands
core MD99-2225 [Levac, 2003]. In La Have Basin (core
HU95030-24 [Levac, 2001]), Emerald Basin (CSS Dawson
core DA77002-20 [Scott et al., 1984]), and Canso Basin
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