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 142

the boreal forest is Picea mariana, accompanied by Abies
balsamea, Betula papyrifera, Populus tremuloides, and Pop-
ulus balsamifera. Picea glauca, Pinus strobus, and Betula
alleghaniensis are also found [Rowe, 1977]. The boreal
forest is replaced by small bands of spruce-fir-heath open
woodland along the coastline because of wind exposure.
This open woodland is composed of spruce (P. mariana)
woodland interspersed with heath barrens (Ericaceae), bogs,
and muskeg [Rowe, 1977].

shore. Other taxa (Betula, Alnus, Tsuga, and Quercus, to list
only a few) see their proportions rapidly decrease across the
Scotian Shelf [Mudie, 1982; Mudie and McCarthy, 1994]. In
addition to these selective transport mechanisms, taxa repre-
sentation in pollen assemblages is not proportional to their
abundance in vegetation. Certain trees such as A. balsamea
and Acer spp generally tend to be underrepresented in pollen
diagrams, while big pollen producers such as Pinus are
overrepresented [Davis and Webb, 1975].
Pollen assemblages in both locations re ect these selective

transport mechanisms and differences in pollen production.
Pollen diagrams of both cores 19 and 12 display greater
proportions of bisaccate pollen (mainly Pinus and Picea)

2.3.2. Vegetation in Nova Scotia and Cape Breton. Most
of Nova Scotia, with the exception of the coastal areas and
Cape Breton, belongs to the Atlantic Uplands and Central
Lowlands subdivision of the Acadian forest region of Rowe
[1977]. The forest of the Atlantic Uplands subregion is
composed mainly of Picea rubens, with Tsuga canadensis,
P. mariana, B. papyrifera, Acer rubrum, A. balsamea, P.
strobus, and Pinus resinosa. In addition to these species, the
vegetation of the Central Lowlands also include Acer sac-
charum, Fagus grandifolia, Quercus spp, Ulmus spp, Frax-
inus nigra, Fraxinus americana, and Tilia americana. Dense
lowstands of A. balsamea, P. mariana, and P. glauca are
found along the coast in the Eastern Atlantic Shore subregion
[Rowe, 1977]. Sphagnum bogs occupy areas with poor drain-
age [Rowe, 1977; Ecoregions Working Group, 1989].
Over Cape Breton (northern part of Nova Scotia), P. g l a u c a
and A. balsamea are the main trees, accompanied by P.
balsamifera, F. americana, and Ulmus americana [Rowe,
1977]. On hilly lands, A. rubrum, B. papyrifera,andB.
alleghaniensis, can also be found. T. canadensis and F.
grandifolia are locally abundant on slopes and ravines. In
areas with poor drainage, P. mariana is common [Rowe,
1977]. The forest becomes predominantly deciduous on the
slopes of the highlands and the main tree species are A.
saccharum, F. grandifolia, B. alleghaniensis, and A. rubrum.
Conifers become more prominent on the Cape Breton Pla-
teau, with A. balsamea as the dominant species, with P.
mariana and P. glauca [Rowe, 1977]. Shrubs (Salix spp,
Ericaceae, Alnus spp) are locally abundant throughout all
vegetation zones described here.

Figure 2. Detrital carbonate (DC) peaks in cores HU87033-19P and
HU83033-07P from Notre Dame Channel on the Northeast New-
foundland Shelf. The thick beds of DC labeled AG in these two
cores correlate to the Agassiz drainage as shown by the bracketing
14 C dates on foraminifera. Total carbonate is the sum of percent
calcite and dolomite on a dry weight basis in the sediment, mea-
sured by the Chittick method using acid dissolution and CO 2
evolution [Dreimanis, 1962]. Constraints on the Lake Agassiz
floods were recently reassessed as 8.33 kyr with an error range of
8.15 - 8.48 kyr [Lewis et al., 2009]. The calibrated 2 σ range of the
dates is shown here for levels marked by the triangles in each core.
Dates were obtained on the planktic foraminifer Neogloboquadrina
pachyderma s (sinistral) coiling. Where two dates are posted for a
single level, the upper date is on N. pachyderma s, and the lower
date is on the benthic foraminifer Nonionellina labradorica.

2.4. Taphonomic Issues Affecting Pollen Assemblages in
Marine Sediments

Modern pollen assemblages in marine sediments from the
eastern Canadian margin reflect the vegetation of adjacent
lands; however, representation of the principal taxa varies
with distance from the shoreline [Mudie, 1982]. Pollen trans-
port tends to be selective. Bisaccate pollen (mainly Pinus spp
and Picea spp) is preferentially transported by wind, and
their proportions gradually increase with distance from