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 143

than their onshore counterparts. In core 12, the proportion of
Quercus pollen is also markedly lower compared to onshore
pollen records.
Despite the bias introduced by the selective nature of long-
distance pollen transport, it is possible to recognize the
zonations of terrestrial pollen records in the marine pollen
records [Mudie, 1982; Mudie and McCarthy,1994],and
these zonations will be presented in the results section.
However, since the marine pollen assemblages potentially
integrate the pollen signal from a much larger surface area,
reconstructing a climatic signal using them is ruled out.

brated with the CALIB 6.0.1 online software program [Stui-
ver and Reimer, 1993] using the MARINE09 calibration data
set [Reimer et al., 2009] with a 10 year smoothing function.
A sea ice correction (200 years for core 19 and 35 years for
12) to account for longer-than-present annual sea ice cover
duration in the early Holocene was added to the present-day
Δ R values of 144±38 years for the Labrador and Northeast

Newfoundland shelves and 83±14 years for the Scotian Shelf
[McNeely et al., 2006] during the calibration process. This
procedure is equivalent to subtracting the sea ice correction
from the conventional radiocarbon age before calibration, as
done by Lewis et al. [2009]. Terrestrial conventional 14 C
dates on lake organic sediment were calibrated with the
CALIB 6.0.1 program [Stuiver and Reimer, 1993] using the
INTCAL09 data set [Reimer et al., 2009] with a 10 year
smoothing function. A single calibrated age for a radiocar-
bon date, as used in this chapter, is the mean of the most
probable calibrated age range in the CALIB 6.0.1 calibration
program output (commonly the mean of the two-sigma cal-
ibrated age range). The age is expressed as x.y ka meaning x.
y thousands of calibrated years before present where present
is A.D. 1950.
Sampling resolution for palynological analysis varies with
depth in the cores and inferred sedimentation rates. Samples
for palynological analyses were taken every 10 or 20 cm,
which represents a sample every 100 or 200 years, on aver-
age. In the lower part of core 12, including the interval
representing the Agassiz

3. METHODS

Sediments were analyzed for carbonate content and for
palynological analysis. Calcite and dolomite were measured
by the Chittick method using acid dissolution and CO 2
evolution [Dreimanis, 1962]. The total carbonate shown on
Figure 2 is the sum of percent calcite and dolomite on a dry
weight basis in the sediment.
The dated levels in core 19 were determined either di-
rectly by 14 C dating of monospeci c foraminiferal samples

or mollusc shells or indirectly by correlating to 14 C-dated
DC beds in nearby core HU83033-07 (50°53.2 ′ N53°18.0 ′ W,
457 m water depth; hereafter core 07) and then by corre-
lating core 19 to 14 C-dated onshore lake sediments from
lakes along the Northeast Newfoundland coast (Table 1)
using the similarity of pollen pro le features or pollen zone

boundaries (see section 5). The DC beds contained reduced
concentrations of biogenic carbonate; thus, it was not pos-
sible to date the maximum concentrations of DC; instead,
foraminifera were separated from sediments above and
below each interval and dated in order to bracket the age
of the DC beds.
Conventional 14 C dates on foraminifera from the early
Holocene sections of cores 19 and 12 (Table 2) were cali-

flood, the sampling resolution is a
sample every 40 years. In core 19, this interval is between
100 and 200 years duration.
Sediments were wet sieved at 120

m to remove the
coarsest particles and at 10 μ m to eliminate the fine silt
and clay. The 10

μ

m fraction was processed with cold
hydrochloric acid to remove carbonates and with cold hydro-
fluoric acid (50% concentration) to remove silicates. Lyco-
podium markers were used to estimate concentrations of

- 120 μ

Table 1. Location of Core Sites Studied for This Study and Core Sites Providing Mass Spectrometer Dates Used in This Study

Depth/Elevation
(m)

Latitude
(°N)

Longitude
(°W) Location Core Number Reference

Marine Sites

Notre Dame Channel HU87033-19P 453 50°54.51 ′ 53°15.63 ′ Lewis et al. [2009], Smith and Licht

[2000], this study

Notre Dame Channel HU83033-07P 457 50°53.2 ′ 53°18 ′ Miller [1999], Lewis et al. [2009],

this study

St. Anne ' s Basin HU84011-12P 270 45°46.72 ′ 58°39.16 ′ Levac [2002]

Terrestrial Sites

236 asl a Compass Pond 50°02.05 ′ 56 °11.78 ′ Dyer [1986], Macpherson [1995]

80 asl a Everitt Lake 44°27 ′ 65°52 ′ Green [1987]

61 asl a

Silver Lake 44°34 ′ 63°38.5 ′ Livingstone [1968], Ogden [1987]

a Here asl indicates above sea level.