The Impact of the Final Lake Agassiz Flood Recorded in Northeast Newfoundland and Northern Scotian Shelves Based on Century-Scale Palynological Data - Abrupt Climate Change: Mechanisms, Patterns, and Impacts - page 150

5.3. Dinoflagellate Cyst Zonation spp are typical of ice-edge environments [Mudie et al.,

2001]. Proportions of S. elongatus greater than 20% are only
seen in Baf 5.3.1. Dinoflagellate Cyst Zones in Core 19. The dino a- in Bay and in the Iceland and Norwegian Seas

[Rochon et al., 1999; de Vernal et al., 2001]. The presence of
S. elongatus indicates greater northern influence, and could
signal an increase in meltwater

gellate cyst assemblage in core 19 zone 1 (500 900 cm)

(Figure 10) is dominated by Islandinium minutum, with
Brigantedinium spp. Other cysts (Pentapharsodinium dalei,
Operculodinium centrocarpum, and Nematosphaeropsis la-
byrinthus) occur sporadically in small proportions.
I. minutum and Brigantedinium spp are abundant in arctic-
subacrtic neritic environments (i.e., Newfoundland and
Labrador shelves) [Rochon et al., 1999] and in the Cana-
dian Arctic [Mudie et al., 2001; de Vernal et al., 2001].
P. dalei is found in small percentages in assemblages of the
eastern Canadian margin, including our study region, and it is
found in high percentages only in the Gulf of St. Lawrence
[Rochon et al., 1999; de Vernal et al., 2001]. This assemblage
probably reflects cold postglacial sea surface conditions.
In dino

-

flow southward as well as

colder SST.
Assemblages are once again dominated by I. minutum in
dino 400 cm). Propor-

tions of Brigantedinium spp decrease throughout the zone.
O. centrocarpum and P. dalei are consistently present but in
small proportions. S. elongatus is also present, but its pro-
portion decreases upward. The appearance of Impagidinium
pallidum and Alexandrium tamarense type cysts in this zone
(in the DC layers) is noted.
I. pallidum is typically an Arctic taxon [Rochon et al.,
1999; de Vernal et al., 2001] and today is not found south
of the northern Labrador Shelf. Its presence suggests cold sea
surface conditions as it is rare where temperatures are higher
than 10°C. A. tamarense is a taxon responsible for harmful
algal blooms, which are favored by increased water stratifi-

agellate cyst assemblage zone 3 (350 -

500 cm),
assemblages are dominated by both I. minutum and Brigan-
tedinium spp, with 10% - 20% of Spiniferites elongatus. Low
percentages of O. centrocarpum are present at the top of the
zone. At high latitudes, high percentages of Brigantedinium

agellate cyst assemblage zone 2 (400 -

-
cation [Mudie et al., 2002]. Its presence could be an

Figure 10. Dinoflagellate cysts diagram for core HU87033-19P, Notre Dame Channel. Calibrated ages are the same as in
Figures 6 and 8. Lines on the right are the results of the cluster analysis.