The Role of Hudson Strait Outlet in Younger Dryas Sedimentation in the Labrador Sea - Abrupt Climate Change: Mechanisms, Patterns, and Impacts - page 100

Figure 5. Calcite (%) (solid circles) and dolomite (%) (diamonds) from cores (a) Hu82-57, (b) Hu84-08, (c) Hu97-09
(calcite only), (d) Hu87-09, (e) Hu75-55, and (f) Hu75-56 from the Baf

in margin are plotted in depth (cm) scales. H0, H1,
and H2 events are constrained by 53 14 C-AMS dates. Calcite and dolomite data of these cores are from the works of
Andrews et al. [1993, 1995], Barber [2001], Kirby [1998], and this study. The 14 C-AMS dates are converted to calendar
years B.P. shown as “ ka ” (see section 3 for details).

4.3. H0 Records in Sohm Abyssal Plain of the North Atlantic 5. DISCUSSION

Fine-grained turbidites with high carbonate content are
present on the northeastern SAP in core Hu98-05. These
turbidites interbed with terrigenous mud turbidites and very
thin hemipelagic intervals (Figure 8). Detrital petrography
and the location of the core at the terminus of the NAMOC
led Piper and Hundert [2002] to identify Hudson Strait ice as
the source of the carbonate turbidites, which were transported
through the NAMOC. A ~1.2 m thick unit at about 3 m
subbottom is characterized by high carbonate, L color, and
magnetic susceptibility with prominent laminations picked
out by changes in the abundance of silt (Figure 8). The
proportion of coarse silt decreases upward through the bed
[Benetti, 2006]. Two 14 C-AMS dates immediately above and
below this unit bracket its age between 11.0 and 13.6 ka so
that the carbonate interval most likely correlates with the YD.

5.1. Accuracy of Radiocarbon Dating

Reconstructing stratigraphy close to a former continental
ice sheet margin setting is a dif cult task, as many of the

sediments are devoid of biogenic carbonate required for the
14 C-AMS dating. In addition, the transport of older carbon
and uncertainty in surface ocean reservoir ages complicate
the stratigraphy. We have used a regional reservoir anomaly
( R) of 50 years [Reimer et al., 2009] for converting the 14 C-

AMS dates to calendar years to construct the age models of
the cores used in this study. This is probably a minimum
estimate of

Δ

Δ R as discussed in the methods section; this Δ R

could be hundreds of years. No accurate estimate of the R is

available from the Labrador Sea. However, it is assumed that
the

Δ

Δ R could vary by as much as 400 - 500 years, as revealed