Quaternary International 99-100 (2003) 29–43
Ice-rafted detritus evidence from 40Ar/39Ar ages of individual
hornblende grains for evolution of the eastern margin of the
Laurentide ice sheet since 43 14C ky
Sidney R. Hemminga,*, Irena Hajdasb
a
Department of Earth and Environmental Sciences and Lamont-Doherty Earth Observatory of Columbia University, Rt. 9W, Palisades, NY 10964, USA
b
AMS 14C Lab, ETH Hoenggerberg, HPK H27, CH-8093 Zurich, Switzerland
Abstract
During the last glacial interval, the North Atlantic ice sheets expanded and contracted in approximate synchronicity with orbitally
forced global climate change. Variation in ice rafted detritus content in North Atlantic marine sediment cores record the waxing and
waning of glaciers, as well as the abrupt temperature changes at millennial time scales. The background variations of ice rafting are
punctuated by Heinrich layers, which appear to record the catastrophic collapse of the Laurentide ice sheet through the Hudson
Strait. The objective of this paper is to document the evolution of glaciation on Laurentia during the last 43 14C kyr. We present a
provenance study based on 40Ar/39Ar dates of individual hornblende grains from 57 samples taken at 2 cm spacing between 4 and
134 cm from core V23-14 (43.41N, 45.251W, 3177 m). Sedimentation rates outside of the Heinrich layers are very low in this core, but
the Heinrich layers are easily identified. Laurentide glaciation did not extend into the ocean south of 551N until about 26 14C kyr,
and retreated to the coastline or beyond by 14 14C kyr. Documenting the history of this major ice sheet has significant implications
for understanding ice rafting sources in more distal locations where mixing among different ice sheets is likely.
r 2002 Elsevier Science Ltd and INQUA. All rights reserved.
1. Introduction
The occurrence of ice rafted detritus (IRD) in marine
sediments outlines the former presence of ice sheets that
extended to the edges of the continental shelves, and the
occurrence of both sea ice and iceberg IRD indicates the
geographic extent of drifting ice (Ruddiman, 1977;
Smythe et al., 1985). The distribution of IRD in the
North Atlantic has been used to infer the major iceberg
sources and the general pattern of surface circulation
during the glacial cycles of the Pleistocene. It also has
confirmed a similar pattern for glacial and interglacial
times with a southward shift in the locus of melting
related to colder surface water in glacial times (Ruddiman, 1977; Grousset et al., 1993; Dowdeswell et al.,
1995; Robinson et al., 1995). Ruddiman (1977) showed
that the flux of IRD during the last glacial cycle is
correlated to the extent of ice sheets in the Northern
*Corresponding author. Tel.: +1-845-365-8417; fax: +1-845-3658155.
E-mail addresses: [email protected] (S.R. Hemming),
[email protected] (I. Hajdas).
Hemisphere. In addition to the depositional pattern, the
composition of IRD constrains the origin of the
icebergs. Accordingly, within the limits of grain size
uncertainties in separating iceberg from sea ice rafting,
IRD studies lend themselves to studying the evolutions
of ice sheets, but only as the glaciers extended into the
marine realm and began to release icebergs.
In order to eventually document the relative IRD
contribution of the different Northern Hemisphere ice
sheets, it is necessary to constrain the compositions and
relative timing along different ice sheet margins such as
the Arctic, Labrador and Atlantic sectors of the
Laurentide ice sheet. However, it is important to state
up front that an increase of IRD from a particular
source, by itself, does not require or even suggest a
collapse of a particular ice sheet. The only IRD events
where the documented evidence is strong for catastrophic collapse of an ice sheet are the Heinrich layers,
particularly H1, H2, H4 and H5. This evidence is
combined observations of greatly increased sediment
flux (Francois and Bacon, 1994; Thomson et al., 1995;
McManus et al., 1998; Veiga-Pires and Hillaire-Marcel,
1999), and distinctive provenance (e.g., Jantschik and
1040-6182/02/$ - see front matter r 2002 Elsevier Science Ltd and INQUA. All rights reserved.
PII: S 1 0 4 0 - 6 1 8 2 ( 0 2 ) 0 0 1 1 0 - 6
30
S.R. Hemming, I. Hajdas / Quaternary International 99-100 (2003) 29–43
Fig. 1. Maps of the North Atlantic with generalized basement geology (modified from Hemming et al., 1998). (A) flux of IRD to the North Atlantic
(mg/cm2/kyr) from 40 to 25 kyr (from Ruddiman, 1977). (B) flux of IRD to the North Atlantic from 25 to 13 kry (from Ruddiman, 1977).
Huon, 1992; Bond et al., 1992; Grousset et al., 1993;
Gwiazda et al., 1996a, b; Hemming et al., 1998). The
many other documented ice rafting events are also
important for understanding ocean–ice–atmosphere
interactions, but they do not appear to represent major
flux changes. In this study we present data at
approximately 1 kyr resolution from 14 to 34 14C kyr
and at approximately 4 kyr resolution from 6 to 14 and
from 34 to 43 14C kyr in northwest Atlantic core V23-14.
Although data are included for Heinrich layers H1–H5,
the goal of this work is to understand the general
evolution of IRD compositions, and by extension the
evolution of ice caps on Laurentia, during Marine
Isotope Stages (MIS) 3, 2 and 1. Due to the location of
V23-14 (Fig. 1), we expect that the dominant IRD
sources during glacial times will be the Laurentian
margin; accordingly, we take variations in the provenance to represent variations in the extension of the ice
caps into the marine environment such as proposed by
Hemming et al. (2000b).
2. Samples and methods
Core V23-14 (43.41N, 45.251W, 3177 m) was sampled
at 2 cm intervals from 4 to 142 cm (total core length is
S.R. Hemming, I. Hajdas / Quaternary International 99-100 (2003) 29–43
Table 1 (continued)
Table 1
Counting results from V23-14
Depth Weight F>63 split #forams/g %pachy #lithics/g %IRD
(cm) (g)
mm
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
42
44
46
48
50
52
54
56
58
60
1.428
1.426
1.373
1.409
1.485
1.811
1.249
2.507
2.724
2.115
2.025
2.140
2.336
2.260
2.063
2.648
2.589
2.233
2.350
2.810
3.034
2.660
2.642
1.868
2.081
1.926
2.426
2.834
2.170
0.45
0.27
0.33
0.25
0.23
0.24
0.25
0.46
0.50
0.39
0.34
0.32
0.39
0.37
0.44
0.40
0.35
0.30
0.25
0.27
0.26
0.29
0.22
0.24
0.21
0.22
0.31
0.29
0.21
62
64
66
68
70
72
74
76
78
80
82
84
86
88
90
92
94
96
98
100
102
104
106
108
110
112
114
116
118
120
122
2.493
1.922
3.062
2.865
2.070
2.261
2.711
1.783
1.783
1.670
2.155
3.373
3.373
2.298
2.511
2.274
2.581
2.137
2.263
1.516
2.355
1.949
1.924
2.276
1.706
2.294
1.778
2.702
1.905
2.299
2.408
0.20
0.34
0.38
0.30
0.32
0.38
0.62
0.50
0.49
0.44
0.44
0.28
0.21
0.29
0.40
0.45
0.52
0.53
0.48
0.30
0.31
0.24
0.25
0.19
0.24
0.23
0.25
0.25
0.21
0.22
0.21
31
16
4
8
4
4
4
7352
28
1282
91
5
152
28
5547
1548
2045
2314
1519
2238
43
98
61
96
100
94
16
16
16
16
16
16
8
16
16
8
8
8
4780
6413
8539
6986
4082
5131
2248
3730
90
73
56
61
76
68
55
69
53
37
36
3236
3389
4757
3967
3933
3672
3183
5476
5360
4067
5294
2884
40
35
36
36
49
42
59
59
58
82
83
97
8
8
4
8
8
8
8
32
75
29
51
12
4
10
2515
2529
1071
1803
1511
1836
2723
99
97
97
97
99
100
100
8
8
8
8
8
8
8
8
32
32
64
64
64
32
8
32
64
32
64
64
64
16
16
16
16
8
8
16
8
32
8
16
8
18
1545
99
45
87
193
3
0
2674
16,525
14,718
13,389
14,718
12,978
3824
1705
6766
18,327
11,569
19,246
16,322
15,638
1034
1135
213
166
130
28
28
50
118
38
7
73
1075
566
1821
2092
2674
3053
7495
5133
7502
3718
7216
5588
3925
3522
2625
2308
4985
4432
5627
4654
4504
2725
4748
2913
2977
3020
3434
3422
2150
2644
2532
96
87
90
100
100
53
31
26
36
20
36
59
70
34
13
17
21
21
26
82
80
93
97
96
99
99
99
97
98
100
97
871
1114
89
14
78
39
41
64
52
45
47
73
68
46
52
55
57
55
Depth Weight F>63 split #forams/g %pachy #lithics/g %IRD
(cm) (g)
mm
124
126
128
130
132
134
136
138
140
142
2.884
3.378
3.387
2.947
4.018
3.580
3.522
5.201
3.862
3.119
0.23
0.27
0.54
0.60
0.28
0.24
0.23
0.21
0.26
0.27
16
16
32
64
32
32
32
32
32
8
28
28
4015
12,401
3233
2020
136
117
0
113
66
60
28
38
2607
4651
5981
5017
3369
2878
3861
2966
3314
1755
99
99
60
29
51
59
97
96
100
94
813 cm). Samples were dried, weighed and disaggregated
and then wet-sieved at 63 mm. The weight of the >63 mm
fraction was recorded. Samples were then sieved at
150 mm, and the 63–150 mm fraction saved for future
work. The >150 mm fraction was split to save an archive
for counting (fractions counted are reported in Table 1),
and hornblende grains for 40Ar/39Ar dating and
foraminifera for 14C dating were picked from the
working fraction.
Counts were made of the total foraminifera content,
% Neoglobigerina pachyderma (s.) where possible, and
total IRD from the >150 mm fraction. 14C analyses were
made at the AMS lab at ETH Zurich. An early batch of
five samples was measured in 1992 for W. S. Broecker.
Samples to confirm and enhance the chronology were
measured in 2000 and 2001.
An effort was made to select at least 15 hornblende
grains per sample; however, in some cases this was not
possible, and all the grains were picked and analyzed.
Hornblende grains were co-irradiated with hornblende
monitor standard Mmhb (age=525 Myr, Samson and
Alexander, 1987) in the Cd-lined, in core facility
(CLICIT) at the Oregon State reactor. Analyses were
made in the Ar geochronology laboratory at LamontDoherty Earth Observatory. Individual grains were
fused with a CO2 laser, and ages were calculated from
Ar isotope ratios corrected for mass discrimination,
interfering nuclear reactions, procedural blanks and
atmospheric Ar contamination.
3. Results
Data are presented in Tables 1–3 and Figs. 2–6.
Heinrich layers can be identified in this core by visual
inspection of the >150 mm fraction. Within the Heinrich
layers, foraminifera are absent and detrital carbonate
percentages are high. The locations of the Heinrich
layers can thus be easily spotted based on the low
number of foraminifera per gram (Fig. 2). It can also be
seen that the Heinrich layers in this core are character-
S.R. Hemming, I. Hajdas / Quaternary International 99-100 (2003) 29–43
32
Table 2
14
C ages and H-layer identifications from core V23-14
ETH
9894
22,560
22,561
9586
22,562
22,563
22,564
9582
24,638
24,639
9581
9580
ST
3218
10,812
10,813
3036
10,814
10,815
10,816
3032
11,896
11,897
3031
3030
H-1
H-2
H-3
H-4
H-5
Depth (cm)
4
18
24
30
72
74
76
85
96
128
130
170
14
Fossil
Inflata
N. Pachy
N. Pachy
N. Pachy
N. Pachy
N. Pachy
N. Pachy
N. Pachy
N. Pachy
N. Pachy
N. Pachy
N. Pachy
C agea (yr)
b
(left)
(left)
(left)
(left)
(left)
(left)
(left)
(left)
(left)
(left)
(left)
6175
14,580c
16,040c
17,360b
23,710c
23,620c
24,860c
28,010b
30,730c
36,670c
38,660b
>37,360b
Interval (cm)
14
10–17
40–64
B85–87e
106–126e
136–ende
14,000
20,500
27,000
35,000
43,000
71s
65
150
120
130
190
210
210
300
260
430
760
420
d13C
8.9
0.8
0.2
0.7
0.4
0.8
2.1
5.4
1.5
0.7
1.4
6.4
71s
1.1
1.2
1.2
1.4
1.2
1.2
1.2
1.4
1.1
1.1
2.4
1.8
C aged (yr)
Radiocarbon measurements made at ETH, Zurich.
.
Not corrected for B400 year reservoir effect.
Samples measured in 1992. Blank age B38000.
c
Samples measured in 2000 and 2001. Blank age B45,000.
d
Heinrich layer 14C age estimates are based on data from Bond et al. (1992, 1993) and Voelker et al. (1998, 2000)
e
Between 66 and 76 cm, there is little detrital carbonate. At 78 cm there is abundant detrital carbonate, but also abundant foraminifera. From 78 to
142 cm (the bottom of the studied interval), there is detrital carbonate. H-3, H-4, and H-5 are picked where the abundance of foraminifera is very low.
a
b
ized by a low fraction of >63 mm material relative to the
bulk sediment, and by a relatively low number of lithic
grains per gram (Fig. 2). While the numbers of
foraminifera, and thus % IRD are consistent with
previous identifications of the Heinrich layers, the
numbers of lithic grains per gram are low in core V2314 compared to those reported at other sites (e.g., V2882, McManus et al., 1998).
Results of 14C analyses are presented in Table 2, and
stratigraphic information and an age model are presented in Figs. 2 and 3, respectively. Core V23-14 has a
low sedimentation rate outside of the Heinrich layers,
particularly above H1 and below H4, B0.5 cm/kyr.
Between Heinrich layers within the H1–H4 interval the
sedimentation rate is approximately 2 cm/kyr. Heinrich
layers H1, H2, and H4, interpreted to have been
deposited almost instantaneously, have thicknesses of
7, 24, and 20 cm, respectively (Table 1, Figs. 2 and 3).
One thousand and thirty-eight individual hornblende
grains from 57 samples, covering the interval of
approximately 6–43 14C kyr, were analyzed for this
study (Table 3, Fig. 4). Outside of Heinrich layer
samples, there are only four samples where fewer than
13 grains were analyzed. Three of these are the 3 samples
above H1, and the other is at 40 cm, just above H2.
Hornblende age populations are presented on histogram plots for specific intervals within the core: (1)
above H1 (Fig. 5a), (2) H1 (Fig. 5b), (3) between H1 and
H2 (Fig. 5c), (4) H2 (Fig. 5d), (5) between H2 and H3
(Fig. 5e), (6) H3 (Fig. 5f), (7) between H3 and H4
(Fig. 5g), (8) H4 (Fig. 5h), (9) between H4 and H5
(Fig. 5i). The histogram age bin intervals are not even,
but rather are divided based on known major geological
provinces around the North Atlantic (Fig. 1). It is
apparent from these plots that most of the intervals have
a dominant Paleoproterozoic (1650–1900 Myr) age
population. The two exceptions are the intervals
between H3 and H2 and between H2 and H1. In these
two intervals, there is a substantial increase in Paleozoic
(250–600 Myr) and Mesoproterozoic (Grenville, 800–
1100 Myr) populations.
4. Discussion
Core V23-14 is located within the thickest part of
Ruddiman’s (1977) IRD belt, and directly downstream
of any Gulf of St. Lawrence region contributions
(Fig. 1). We suggest that the results presented here
provide constrains on the evolution of the Laurentide
ice sheet or smaller satellite ice sheets (e.g., Stea et al.,
1998) and their contributions of icebergs to the northwest Atlantic margin. In Fig. 6, the individual hornblende data are binned according to the age brackets as
in the histograms (Fig. 5) for individual sample depths
between the Heinrich layers. Data from within the
Heinrich layers are lumped into one interval with an
assumed duration of 0.1 kyr. There is some disagreement
S.R. Hemming, I. Hajdas / Quaternary International 99-100 (2003) 29–43
Table 3
40
A/39Ar hornblende data from core V23-14
Depth
(cm)
40
33
Table 3 (continued)
7
Age
(14C ky BP)
Ca/K
% Ar*
Age
(Myr)
4
4
4
4
4
4
4
4
4
6
6
6
6
6
8
8
8
8
8
8
8
8
8
5.8
5.8
5.8
5.8
5.8
5.8
5.8
5.8
5.8
8.5
8.5
8.5
8.5
8.5
11.3
11.3
11.3
11.3
11.3
11.3
11.3
11.3
11.3
23.3
7.6
6.1
7.4
28.4
32.1
19.7
9.9
7.4
18.0
14.2
11.1
5.0
7.4
6.3
6.3
12.0
6.8
10.1
13.7
12.4
10.1
19.9
97.2
99.8
99.2
99.6
99.1
98.8
97.8
99.6
99.5
100.1
99.7
99.4
98.7
99.4
99.7
99.8
30.8
99.7
100.0
97.4
96.0
99.0
97.4
1465
1755
1786
1763
1690
1670
1751
1900
2636
1643
2574
1834
2116
1879
1689
1719
81
1697
2635
1596
1650
1644
1725
5
5
8
8
16
12
28
8
13
10
8
7
7
8
4
4
5
6
13
23
32
12
14
10
10
10
10
10
10
10
10
10
12
12
12
12
12
12
12
12
14
14
14
14
14
14
14
14
14
16
16
16
16
16
16
18
18
18
18
18
14.0
14.0
14.0
14.0
14.0
14.0
14.0
14.0
14.0
14.0
14.0
14.0
14.0
14.0
14.0
14.0
14.0
14.0
14.0
14.0
14.0
14.0
14.0
14.0
14.0
14.0
14.0
14.0
14.0
14.0
14.0
14.1
14.7
14.7
14.7
14.7
14.7
22.2
7.6
33.6
35.6
10.4
21.4
5.6
6.6
7.6
13.2
25.2
13.7
21.4
9.2
37.2
4.0
9.5
6.9
21.3
10.3
6.2
7.6
14.3
9.2
12.5
6.9
35.1
7.4
15.7
8.2
14.6
7.7
25.2
7.9
18.1
6.5
8.0
99.6
99.4
99.5
88.1
97.7
99.0
99.7
93.9
100.2
99.3
93.1
95.9
93.3
98.7
95.2
97.8
100.0
99.8
98.9
65.1
99.4
97.7
82.7
98.2
99.4
99.2
78.3
97.6
99.1
97.9
98.4
97.4
98.1
96.6
98.7
99.7
99.6
1715
1857
2360
1992
1773
1773
2557
1711
1705
1755
1697
1740
2336
2815
1814
1524
1712
1703
1694
1786
1725
1652
2065
1697
2546
1734
1747
1709
2461
1706
1724
2530
1785
2053
1851
1653
2592
5
15
18
31
5
10
32
22
11
17
48
12
48
16
47
4
10
5
16
19
11
14
39
8
28
11
9
7
12
12
11
14
6
6
7
4
13
7
Age
(14C ky BP)
Ca/K
%40Ar*
18
18
18
18
18
18
18
18
18
18
18
18
18
18
18
18
18
14.7
14.7
14.7
14.7
14.7
14.7
14.7
14.7
14.7
14.7
14.7
14.7
14.7
14.7
14.7
14.7
14.7
32.7
14.1
13.2
11.1
6.0
5.7
5.1
6.7
9.8
34.9
8.8
10.9
6.4
8.4
18.9
8.1
8.0
97.7
97.8
99.0
98.4
98.4
99.8
99.7
99.9
99.8
89.1
97.3
94.7
97.0
99.7
78.3
99.0
98.2
1687
1858
1739
1720
1211
1698
1716
2622
1707
1658
1658
1797
1549
1017
1735
2545
1397
12
11
9
7
3
4
6
7
7
21
5
8
6
7
9
14
11
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
22
22
22
22
22
22
22
22
22
22
22
22
22
22
22
22
22
22
22
22
22
22
22
22
22
22
15.2
15.2
15.2
15.2
15.2
15.2
15.2
15.2
15.2
15.2
15.2
15.2
15.2
15.2
15.2
15.2
15.2
15.2
15.7
15.7
15.7
15.7
15.7
15.7
15.7
15.7
15.7
15.7
15.7
15.7
15.7
15.7
15.7
15.7
15.7
15.7
15.7
15.7
15.7
15.7
15.7
15.7
15.7
15.7
12.1
9.4
26.6
10.9
23.7
3.6
7.2
6.1
24.5
34.9
28.8
8.6
13.3
9.5
32.1
13.4
27.8
6.9
34.6
10.8
6.2
7.8
9.6
9.2
15.2
8.1
8.0
23.9
4.8
9.3
6.1
10.2
13.6
13.8
11.7
12.0
8.3
19.5
8.6
6.5
9.4
12.7
12.2
1.6
98.7
99.4
98.7
99.5
97.5
93.9
99.4
99.3
97.7
92.4
97.0
99.4
98.8
99.2
95.3
97.6
99.4
98.9
99.0
98.3
98.5
91.9
95.2
99.0
98.6
99.0
95.2
98.9
69.0
99.6
97.5
99.0
91.0
99.9
97.8
99.1
99.7
98.5
98.3
98.0
94.9
95.5
88.2
5.3
2133
1952
1906
1774
1709
396
1963
1787
1724
1768
3260
1814
1748
1812
1970
2139
2393
2617
1837
1710
1738
2163
1177
2639
1745
1735
2555
1635
47
2537
2443
1752
851
1800
985
1821
2616
1776
2654
1730
1815
2007
1595
1048
4
5
6
6
9
2
9
8
16
15
38
6
8
14
29
25
28
18
8
8
7
10
8
11
8
6
8
16
2
13
79
10
11
12
17
19
21
33
33
19
80
64
68
212
Depth
(cm)
Age
(Myr)
S.R. Hemming, I. Hajdas / Quaternary International 99-100 (2003) 29–43
34
Table 3 (continued)
Depth
(cm)
22
22
22
22
22
22
22
22
24
24
24
24
24
24
24
24
24
24
24
24
24
26
26
26
26
26
26
26
26
26
26
26
26
26
26
26
26
26
26
26
26
26
26
26
26
26
26
26
26
28
28
28
28
28
28
28
28
28
28
28
28
28
Table 3 (continued)
Age
(14C ky BP)
Ca/K
15.7
15.7
15.7
15.7
15.7
15.7
15.7
15.7
16.3
16.3
16.3
16.3
16.3
16.3
16.3
16.3
16.3
16.3
16.3
16.3
16.3
16.8
16.8
16.8
16.8
16.8
16.8
16.8
16.8
16.8
16.8
16.8
16.8
16.8
16.8
16.8
16.8
16.8
16.8
16.8
16.8
16.8
16.8
16.8
16.8
16.8
16.8
16.8
16.8
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
1.3
5.9
5.2
6.2
2.0
2.6
5.8
7.2
7.6
11.6
9.3
31.7
18.0
6.7
7.6
5.6
7.4
16.9
7.6
10.3
6.3
16.5
1.6
8.2
2.2
5.7
7.5
11.7
6.1
8.5
6.7
24.0
6.3
7.0
6.9
8.5
8.9
10.7
10.2
20.9
31.7
8.1
31.3
5.8
5.6
3.7
9.1
5.9
6.2
1.8
34.0
5.0
7.4
10.5
6.9
5.3
7.5
35.7
13.9
7.2
8.2
25.3
%40Ar*
38.3
92.0
93.1
87.0
71.8
92.8
88.1
92.1
98.3
99.0
99.5
96.5
99.4
98.4
99.4
99.9
99.1
99.6
96.2
99.4
99.7
93.3
96.2
82.6
99.5
99.1
99.6
98.8
98.1
99.6
98.4
97.3
95.0
99.4
99.4
99.5
99.9
98.1
96.0
70.0
89.9
98.0
89.2
96.2
98.9
66.3
99.0
96.3
100.9
99.5
67.5
99.6
99.6
98.2
98.8
99.1
98.8
75.3
99.1
100.0
99.6
97.7
Age
(Myr)
397
1772
933
897
640
1325
1022
1981
864
950
1446
1648
3296
1042
940
1738
1012
1724
936
1734
1687
470
1731
1077
1933
1023
1828
988
909
2655
950
1760
1136
2613
2316
1741
1818
1778
1818
965
422
2588
2099
1069
1818
549
1744
415
1019
1660
1050
1045
1044
1409
1796
1026
1702
759
1035
1762
1770
1842
7
23
53
27
29
10
40
31
48
3
7
7
22
19
6
6
10
9
22
6
9
9
4
10
11
34
8
12
10
12
26
7
19
8
13
16
12
13
19
15
63
11
18
57
10
16
60
17
6
15
17
23
8
11
10
12
7
10
9
22
13
16
50
Depth
(cm)
28
28
28
28
28
28
28
28
28
28
28
28
28
28
28
28
28
28
28
28
28
28
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
32
32
32
32
32
32
32
32
32
32
32
32
32
32
32
32
32
32
Age
(14C ky BP)
Ca/K
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.3
17.9
17.9
17.9
17.9
17.9
17.9
17.9
17.9
17.9
17.9
17.9
17.9
17.9
17.9
17.9
17.9
17.9
17.9
17.9
17.9
17.9
17.9
18.4
18.4
18.4
18.4
18.4
18.4
18.4
18.4
18.4
18.4
18.4
18.4
18.4
18.4
18.4
18.4
18.4
18.4
4.8
5.9
6.6
29.6
18.0
9.5
6.1
5.9
7.2
7.8
13.4
25.5
7.5
7.3
8.6
4.6
5.9
2.6
26.0
7.0
7.4
37.9
3.9
7.0
11.3
16.0
5.0
9.8
36.9
7.4
10.0
8.8
7.3
1.7
17.9
25.2
12.4
5.7
35.4
7.9
10.0
4.3
9.9
5.6
10.7
5.5
6.9
35.5
23.9
5.3
5.4
6.2
11.5
7.0
17.9
9.8
27.0
5.4
11.3
18.5
8.7
8.9
%40Ar*
97.4
97.5
93.9
96.6
103.4
49.2
95.3
97.8
98.8
98.5
98.9
56.8
99.4
93.9
95.2
99.6
98.4
41.9
89.9
97.6
98.6
97.7
23.9
92.5
98.9
98.9
99.8
99.2
95.9
99.2
97.6
95.4
99.5
101.2
98.3
97.7
99.5
98.8
80.2
97.9
99.6
98.4
98.9
96.5
92.8
99.4
98.4
92.1
97.6
98.0
96.2
99.4
99.7
97.1
60.2
99.5
95.1
99.6
98.8
99.0
98.3
98.2
Age
(Myr)
1053
1734
1790
1844
61
418
1826
1031
2044
1041
994
1729
1852
995
1801
1771
1831
406
1859
1920
1793
1875
75
440
775
2394
1801
2584
1006
1875
1423
1778
1013
70
1695
1833
1965
1070
1871
1070
2671
1764
1750
815
798
1758
974
495
3005
1357
1699
2542
2120
971
27
973
1850
1796
1827
1737
1818
1814
7
13
37
55
41
33
43
46
10
12
10
21
90
13
13
39
12
15
37
79
20
13
80
13
3
6
34
10
17
15
11
12
30
8
10
21
28
25
10
98
18
13
12
12
9
7
16
13
6
23
9
15
25
13
11
5
9
36
16
15
18
17
20
S.R. Hemming, I. Hajdas / Quaternary International 99-100 (2003) 29–43
Table 3 (continued)
Depth
(cm)
32
32
32
32
32
32
32
32
32
32
32
32
32
32
34
34
34
34
34
34
34
34
34
34
34
34
34
34
34
34
34
34
34
34
34
34
34
34
34
34
34
34
34
34
34
34
34
34
34
34
36
36
36
36
36
36
36
36
36
36
36
36
35
Table 3 (continued)
Age
(14C ky BP)
Ca/K
18.4
18.4
18.4
18.4
18.4
18.4
18.4
18.4
18.4
18.4
18.4
18.4
18.4
18.4
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
18.9
19.4
19.4
19.4
19.4
19.4
19.4
19.4
19.4
19.4
19.4
19.4
19.4
4.6
6.9
11.7
1.5
6.4
6.5
5.6
10.6
5.2
19.9
18.8
13.6
36.6
27.2
7.3
23.9
9.7
27.4
39.8
2.5
8.2
32.8
9.3
4.9
12.7
11.8
5.2
9.6
15.5
5.6
5.9
10.2
4.1
4.2
7.1
5.0
24.6
5.2
29.3
9.1
7.6
15.9
3.7
1.8
21.6
8.7
9.1
11.5
14.5
13.4
10.3
7.6
15.1
8.0
7.9
31.2
7.6
6.5
5.0
38.7
8.6
12.7
%40Ar*
97.7
98.1
98.7
95.7
99.7
94.6
98.0
99.1
99.6
89.8
87.1
96.5
92.3
88.7
99.8
97.8
98.9
98.8
99.2
100.0
99.9
70.7
99.8
99.6
90.9
99.3
85.1
98.9
99.7
98.8
99.7
98.8
99.5
87.6
99.2
99.9
97.3
99.0
98.2
99.6
99.7
97.2
97.7
68.9
95.8
99.7
99.1
99.1
98.7
99.2
94.7
99.8
99.4
99.7
98.8
98.3
99.5
99.9
99.4
96.6
100.4
99.7
Age
(Myr)
1063
1842
1816
343
1841
404
1909
1958
1712
1756
964
1910
1706
500
1758
1858
2057
2866
2503
2359
1781
421
1722
1793
951
1737
1705
1841
2665
1923
1822
1835
1795
531
968
1664
1872
2226
1904
2548
1066
543
382
133
1797
1805
1767
1819
1833
1818
421
1916
2105
1781
1804
3029
1741
1761
1737
1507
1805
2638
7
11
21
36
3
17
4
20
21
10
19
14
22
43
12
10
11
14
40
29
35
18
22
17
13
18
17
15
18
11
12
13
24
13
5
7
10
26
11
33
23
7
6
3
5
25
17
14
16
20
14
4
11
21
14
15
26
14
13
13
24
16
22
Depth
(cm)
%40Ar*
Age
(Myr)
7
Age
(14C ky BP)
Ca/K
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
36
38
38
38
38
38
38
38
38
38
38
38
38
38
38
38
38
38
38
38
38
38
38
38
38
19.4
19.4
19.4
19.4
19.4
19.4
19.4
19.4
19.4
19.4
19.4
19.4
19.4
19.4
19.4
19.4
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
10.7
5.4
8.0
1.8
9.1
11.9
8.6
7.6
4.7
6.9
10.8
18.8
6.2
7.4
19.0
7.3
9.5
3.5
10.3
22.9
4.2
6.6
24.7
32.2
29.5
5.0
5.7
8.1
16.0
5.4
10.3
2.9
5.6
7.7
13.9
5.0
29.0
7.2
7.3
8.5
99.5
99.8
99.7
98.8
93.2
99.4
99.1
94.1
93.5
99.8
99.5
99.6
99.0
98.2
99.2
97.7
98.7
98.0
99.7
100.3
99.8
100.1
104.3
98.7
96.5
99.4
97.8
100.0
99.3
99.5
99.9
95.0
99.5
99.4
98.7
97.8
91.7
98.7
99.6
99.2
1820
1749
2721
1784
1746
1732
1747
1855
1776
1043
1817
1791
1739
1737
2537
1716
2128
551
1788
2036
1954
1776
1927
2540
1912
1900
1802
1834
1819
1792
2668
530
1648
1876
1738
1937
2401
1798
1777
1799
16
17
20
22
16
22
20
24
36
9
18
32
14
14
43
16
15
6
25
23
11
15
60
15
28
16
15
14
13
12
23
5
11
11
16
17
33
15
11
15
40
40
40
40
40
42
42
42
42
42
42
42
42
42
42
42
44
44
44
46
46
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
22.0
9.4
12.8
11.1
19.5
10.2
5.6
17.1
12.4
9.6
8.8
4.0
7.9
36.6
23.9
6.2
9.2
16.3
14.7
9.1
35.7
98.6
99.6
99.3
100.0
97.8
99.6
99.5
95.0
98.4
98.2
100.2
99.9
99.3
92.4
97.6
99.7
95.7
98.1
97.2
98.8
96.5
1406
2468
2651
2677
1953
1778
1909
2494
1607
1966
1756
1756
1846
1836
1778
1811
1784
1825
1828
2673
2042
19
14
21
22
48
15
18
29
16
26
19
16
15
57
33
17
19
23
25
16
20
S.R. Hemming, I. Hajdas / Quaternary International 99-100 (2003) 29–43
36
Table 3 (continued)
Depth
(cm)
46
46
46
46
46
50
50
50
52
52
52
52
52
52
52
52
52
52
52
54
54
54
54
54
54
56
56
56
56
56
56
56
56
56
56
56
56
56
56
56
56
56
56
56
56
56
56
56
56
56
56
56
56
56
56
58
58
58
58
58
58
58
Table 3 (continued)
Age
(14C ky BP)
Ca/K
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
12.1
8.2
12.4
10.6
16.9
17.8
13.5
4.9
37.5
27.2
25.9
2.4
5.9
12.1
16.3
12.7
8.0
21.5
7.8
2.1
7.0
4.4
8.3
10.3
11.3
11.5
19.2
10.1
13.4
10.3
8.7
9.6
11.0
3.2
7.9
8.4
11.9
7.9
6.7
9.8
5.7
1.6
10.7
11.2
19.1
9.6
4.9
11.1
6.8
21.0
14.6
6.1
20.3
24.8
6.9
7.7
20.5
6.9
7.0
9.3
12.4
5.9
%40Ar*
94.2
99.3
79.6
100.4
90.7
99.0
98.7
99.3
95.5
99.1
94.6
98.5
100.6
100.3
99.2
99.3
98.7
85.6
99.2
81.9
99.9
96.9
98.2
100.0
100.0
95.6
99.1
99.5
100.1
99.5
99.3
98.7
98.7
59.4
99.1
99.5
99.2
99.5
99.8
99.0
98.1
97.4
99.9
100.2
99.1
66.5
99.9
99.5
99.7
99.8
98.0
99.4
96.0
92.7
100.2
99.7
99.5
99.9
99.5
99.3
98.0
99.9
Age
(Myr)
1733
2027
1719
1765
1757
1750
1904
2960
2542
1839
1349
2208
1858
1804
1738
1831
2583
1629
2607
658
1756
1723
2583
1778
1797
2009
1928
1826
2735
1816
1848
1848
1773
2647
1761
1705
1809
1761
2727
2745
1809
662
1794
1828
2402
532
1751
1760
1783
1752
1836
1733
1772
1729
1929
1761
1663
1920
1878
1776
1775
1790
7
21
23
67
25
22
18
47
16
15
18
20
41
24
21
26
15
19
74
15
7
15
24
37
22
30
15
17
17
27
16
16
24
12
253
18
12
20
15
13
34
32
10
24
18
16
10
14
19
17
47
35
18
32
24
37
12
13
14
11
14
46
17
Depth
(cm)
%40Ar*
Age
(Myr)
7
Age
(14C ky BP)
Ca/K
58
58
58
58
58
58
58
60
60
60
60
60
60
60
60
60
60
60
60
62
62
62
62
62
62
64
64
64
64
64
64
64
64
64
64
64
64
64
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
20.5
26.0
6.6
5.1
21.7
7.0
5.4
36.9
4.2
21.8
4.7
6.5
8.1
5.3
32.6
7.0
8.2
7.1
5.9
14.7
10.4
9.7
8.6
26.6
13.3
12.4
8.8
6.9
10.7
18.0
9.4
5.7
8.0
17.6
5.2
16.2
13.1
31.0
8.0
100.0
78.7
99.5
99.2
99.9
99.1
99.1
100.2
92.6
98.9
98.7
83.7
98.6
89.8
99.1
99.9
99.6
99.6
99.8
99.1
99.5
99.1
98.3
97.9
98.5
98.1
99.5
99.1
95.7
100.2
99.6
100.4
75.7
99.7
99.3
99.8
99.7
96.6
2797
1620
2483
1718
2635
1793
1986
2621
648
1744
1831
3135
1836
1891
2023
1838
1737
1752
2520
2505
1730
1756
2038
1773
1772
1775
1987
2791
567
1807
1743
1857
1731
1741
1800
2549
1812
1648
33
21
14
35
14
18
12
41
9
16
16
25
18
75
19
14
19
22
32
15
11
18
60
32
26
27
16
52
5
14
4
13
86
12
15
31
58
38
66
66
66
66
66
66
66
66
66
66
66
66
66
66
66
66
66
66
68
68
68
68
68
21.1
21.1
21.1
21.1
21.1
21.1
21.1
21.1
21.1
21.1
21.1
21.1
21.1
21.1
21.1
21.1
21.1
21.1
21.8
21.8
21.8
21.8
21.8
19.2
6.2
21.4
5.3
37.4
14.1
16.1
13.2
6.5
2.8
5.6
11.3
8.4
23.5
6.9
13.6
9.3
25.8
28.1
3.5
6.1
10.0
8.8
98.0
99.0
88.0
99.8
43.0
99.5
99.0
99.6
98.4
62.3
99.0
98.6
94.9
96.2
93.2
59.3
97.9
50.9
12.0
98.0
98.8
98.6
99.5
844
1777
427
1791
53
2158
1801
1856
2757
539
1770
518
1633
1979
1783
475
1753
385
390
596
986
1799
1810
12
15
23
16
13
13
19
19
10
4
6
6
15
30
57
43
13
19
62
4
7
13
12
S.R. Hemming, I. Hajdas / Quaternary International 99-100 (2003) 29–43
Table 3 (continued)
Depth
(cm)
68
68
68
68
68
68
68
68
68
68
68
68
68
68
68
70
70
70
70
70
70
70
70
70
70
70
70
70
72
72
72
72
72
72
72
72
72
72
72
72
72
72
72
72
74
74
74
74
74
74
74
74
74
74
74
74
74
74
76
76
76
76
37
Table 3 (continued)
Age
(14C ky BP)
Ca/K
21.8
21.8
21.8
21.8
21.8
21.8
21.8
21.8
21.8
21.8
21.8
21.8
21.8
21.8
21.8
22.4
22.4
22.4
22.4
22.4
22.4
22.4
22.4
22.4
22.4
22.4
22.4
22.4
23.1
23.1
23.1
23.1
23.1
23.1
23.1
23.1
23.1
23.1
23.1
23.1
23.1
23.1
23.1
23.1
23.7
23.7
23.7
23.7
23.7
23.7
23.7
23.7
23.7
23.7
23.7
23.7
23.7
23.7
24.4
24.4
24.4
24.4
16.5
8.4
24.6
16.5
7.4
7.0
6.8
16.5
4.9
7.7
23.8
7.9
7.5
13.9
5.5
13.7
4.6
29.2
14.4
6.2
4.6
8.4
25.7
20.4
14.6
23.8
12.7
5.0
15.1
4.1
40.4
15.5
20.8
37.3
26.3
14.1
36.0
7.6
9.8
9.4
8.6
10.5
6.2
7.9
8.5
20.1
12.1
1.7
7.6
3.9
12.5
5.8
20.7
7.5
19.0
5.8
4.5
15.9
14.5
17.8
14.4
9.6
%40Ar*
92.0
99.9
97.2
97.7
83.5
100.0
96.0
13.8
99.2
99.3
98.7
99.4
99.6
86.3
96.6
74.8
99.7
68.4
92.1
98.9
89.2
99.0
73.2
90.5
85.9
87.2
99.3
97.2
97.6
98.0
99.9
95.7
99.0
76.4
97.8
95.2
92.6
99.4
99.1
100.1
96.2
99.6
99.3
98.4
60.4
41.6
58.1
99.2
98.9
-6.9
99.5
96.6
97.8
99.2
91.2
96.9
98.8
83.1
99.5
96.1
14.7
99.9
Age
(Myr)
718
1066
1222
1694
1044
1780
980
333
1003
1755
1847
1753
1803
975
993
455
996
427
483
993
409
1737
447
983
1617
436
1818
1780
1677
984
1666
1721
1724
995
2227
1767
1509
950
2384
1700
1043
1841
1625
70
13
5
28
1725
1769
2
1850
1434
2716
1814
65
1804
2160
396
1761
1748
40
2607
7
5
11
12
76
55
39
13
283
9
23
20
10
10
93
10
6
8
16
5
8
4
22
11
28
30
24
22
14
5
5
44
14
17
47
21
27
34
7
13
19
28
22
15
11
1
1
4
30
11
2
14
10
25
12
11
12
14
14
8
8
16
10
Depth
(cm)
76
76
76
76
76
76
76
76
76
76
76
76
76
76
76
76
76
76
76
78
78
78
78
78
78
78
78
78
78
78
78
78
78
78
78
78
78
78
78
78
78
78
78
78
78
78
78
78
80
80
80
80
80
80
80
80
80
80
80
80
80
80
Age
(14C ky BP)
Ca/K
%40Ar*
24.4
24.4
24.4
24.4
24.4
24.4
24.4
24.4
24.4
24.4
24.4
24.4
24.4
24.4
24.4
24.4
24.4
24.4
24.4
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.6
25.6
25.6
25.6
25.6
25.6
25.6
25.6
25.6
25.6
25.6
25.6
25.6
25.6
29.4
7.0
23.7
16.2
11.3
6.0
16.5
11.2
8.6
20.7
13.1
7.8
11.3
15.4
18.0
8.7
10.0
10.8
9.7
4.6
4.8
24.8
12.0
12.4
8.0
10.5
18.4
9.9
34.4
9.3
37.5
7.0
5.2
34.7
8.2
9.0
7.3
6.7
13.3
9.2
7.9
6.2
8.5
6.5
8.1
12.4
15.6
10.2
12.0
6.0
6.1
9.7
36.1
9.6
10.0
8.8
27.1
9.9
4.9
6.7
8.5
8.9
99.7
99.7
98.0
98.9
98.8
99.8
95.2
96.9
99.9
99.3
81.5
99.6
90.5
98.0
98.7
99.7
97.6
99.4
99.0
99.1
99.6
98.7
99.4
98.6
97.6
98.3
98.7
93.0
98.3
98.9
94.5
99.2
99.6
98.5
99.9
99.6
99.9
99.9
98.0
98.4
99.3
99.4
98.7
99.3
98.6
99.1
99.0
96.9
99.4
99.8
99.7
97.2
93.9
99.8
99.3
99.2
97.6
99.2
99.8
99.7
98.4
98.9
Age
(Myr)
4001
1722
1654
1892
1703
1710
1904
1656
1713
1782
65
1710
175
1885
1656
2586
1704
2670
1732
1667
1713
2575
1775
1726
2514
2570
1850
4027
1731
1814
4483
1729
1808
1703
1705
1767
1629
915
1813
1821
1687
1763
2590
1237
1799
1747
2562
1987
2645
1753
1635
1743
2647
1709
1746
1698
1782
2597
1657
1776
1847
1729
7
71
9
21
19
13
6
15
13
6
16
7
8
17
11
15
12
11
13
7
5
6
23
6
16
21
15
9
45
15
9
36
9
7
24
7
11
10
5
20
7
8
8
16
7
13
15
32
20
6
6
5
5
18
5
11
16
35
12
26
13
14
7
S.R. Hemming, I. Hajdas / Quaternary International 99-100 (2003) 29–43
38
Table 3 (continued)
Depth
(cm)
Table 3 (continued)
%40Ar*
Age
(Myr)
7
Age
(14C ky BP)
Ca/K
80
80
80
80
80
80
82
82
82
82
82
82
82
82
82
82
82
82
82
82
82
82
82
82
82
82
82
82
82
25.6
25.6
25.6
25.6
25.6
25.6
26.3
26.3
26.3
26.3
26.3
26.3
26.3
26.3
26.3
26.3
26.3
26.3
26.3
26.3
26.3
26.3
26.3
26.3
26.3
26.3
26.3
26.3
26.3
5.9
9.2
7.9
10.3
6.9
9.9
10.0
30.2
7.0
4.5
8.7
8.0
4.9
8.9
9.6
9.5
5.4
8.5
6.5
9.8
5.2
8.7
14.3
8.5
8.9
8.3
6.9
18.4
21.4
99.2
100.0
96.6
93.4
99.4
97.4
99.6
96.9
99.4
99.8
99.8
99.9
99.8
99.1
99.7
98.3
99.6
98.4
99.0
99.4
99.1
96.4
98.4
99.8
99.6
98.2
99.5
95.3
46.0
1945
1721
1684
1704
2592
1624
2674
1494
1652
1762
1017
2529
1729
2522
2618
2637
1794
1025
1555
1995
1703
2624
465
1807
1682
1816
2000
1640
1875
45
18
18
12
13
21
7
42
4
4
6
11
6
24
8
10
7
8
7
12
7
18
7
9
19
12
10
15
61
84
84
84
84
84
84
84
84
84
84
84
84
84
84
84
84
84
84
84
84
84
84
84
26.9
26.9
26.9
26.9
26.9
26.9
26.9
26.9
26.9
26.9
26.9
26.9
26.9
26.9
26.9
26.9
26.9
26.9
26.9
26.9
26.9
26.9
26.9
39.1
20.4
14.4
7.7
16.2
4.7
7.8
12.4
9.0
7.4
19.7
6.8
14.6
6.3
8.1
6.6
8.6
21.1
9.0
8.7
6.8
34.3
6.9
98.2
99.0
98.3
99.3
99.6
77.2
99.4
99.1
99.3
99.6
97.4
99.5
97.6
99.4
99.5
99.6
99.6
96.2
98.9
99.3
99.8
97.7
99.3
2276
1453
1752
1888
1765
1673
1778
2382
1712
1760
1816
1933
1765
1833
2697
1764
2601
1771
1754
2587
1722
1019
1763
8
16
9
7
14
6
9
13
6
6
7
9
11
6
24
8
20
36
12
11
7
16
18
86
86
86
86
86
86
86
86
27.6
27.6
27.6
27.6
27.6
27.6
27.6
27.6
8.3
5.7
17.1
18.1
23.3
18.5
19.9
19.0
99.9
99.2
93.0
96.9
90.9
99.0
99.5
99.5
1769
1874
1808
2142
1866
1886
1942
1910
6
6
8
44
44
8
18
23
7
Age
(14C ky BP)
Ca/K
%40Ar*
86
86
86
86
86
86
86
86
86
86
86
86
86
27.6
27.6
27.6
27.6
27.6
27.6
27.6
27.6
27.6
27.6
27.6
27.6
27.6
17.2
18.2
7.8
8.3
5.4
13.6
4.1
7.0
16.6
12.2
24.3
19.2
17.9
98.6
99.0
99.4
99.7
99.7
98.7
99.0
98.7
99.2
99.7
98.5
98.7
98.8
1822
1856
1857
2259
1759
1841
1822
1770
3248
1717
2334
1941
1829
25
16
7
11
8
18
9
7
43
14
29
16
20
88
88
88
88
88
88
88
88
88
88
88
88
88
88
88
88
88
88
88
88
88
88
88
88
88
88
88
88
88
88
88
88
88
88
88
88
88
88
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
28.2
7.8
21.0
17.1
20.9
16.9
14.2
7.6
5.8
7.9
12.7
10.2
8.4
19.6
28.2
10.3
21.7
7.2
3.0
5.9
11.8
8.8
15.2
4.0
7.1
30.1
1.5
8.4
18.5
4.7
10.8
4.3
13.1
7.0
16.7
15.7
8.2
10.2
7.6
98.3
98.3
99.0
99.3
97.8
99.4
99.8
99.7
99.6
98.9
99.5
98.8
92.1
97.9
99.1
97.3
99.5
93.7
98.8
99.8
99.9
99.4
99.4
99.8
99.3
82.3
94.3
98.3
97.8
98.6
95.2
89.9
98.8
98.0
98.6
99.4
98.8
99.1
1812
1754
1763
1859
1679
1607
1706
1653
1703
1877
2593
1748
368
1795
2928
1717
1716
1288
1618
2498
2555
2543
1838
1696
2575
816
1684
1703
1606
1874
1887
1643
1772
1658
2883
2436
1742
1723
4
6
6
6
7
7
4
4
5
7
8
8
12
7
15
11
11
37
9
10
15
14
6
6
14
3
17
21
11
24
19
75
15
35
27
20
18
13
90
90
90
90
90
90
90
90
90
28.9
28.9
28.9
28.9
28.9
28.9
28.9
28.9
28.9
8.9
4.1
11.0
10.4
8.3
7.4
9.8
8.8
6.0
96.3
99.0
99.7
99.8
98.7
99.5
99.5
99.6
100.0
1790
1152
1769
2668
1727
1813
1788
1783
1750
6
3
6
8
8
7
6
10
10
Depth
(cm)
Age
(Myr)
S.R. Hemming, I. Hajdas / Quaternary International 99-100 (2003) 29–43
Table 3 (continued)
Depth
(cm)
90
90
90
90
90
90
90
90
90
90
90
90
90
90
90
90
90
90
92
92
92
92
92
92
92
92
92
92
92
92
92
92
92
92
92
92
92
92
92
92
92
92
92
92
92
92
94
94
94
94
94
94
94
94
94
94
94
94
94
94
94
94
39
Table 3 (continued)
Age
(14C ky BP)
Ca/K
28.9
28.9
28.9
28.9
28.9
28.9
28.9
28.9
28.9
28.9
28.9
28.9
28.9
28.9
28.9
28.9
28.9
28.9
29.5
29.5
29.5
29.5
29.5
29.5
29.5
29.5
29.5
29.5
29.5
29.5
29.5
29.5
29.5
29.5
29.5
29.5
29.5
29.5
29.5
29.5
29.5
29.5
29.5
29.5
29.5
29.5
30.1
30.1
30.1
30.1
30.1
30.1
30.1
30.1
30.1
30.1
30.1
30.1
30.1
30.1
30.1
30.1
8.0
8.9
1.1
7.7
4.9
8.0
9.0
6.6
17.8
12.0
10.0
7.3
26.3
9.9
6.0
14.4
7.5
3.6
25.0
12.2
6.9
21.8
20.9
15.8
6.7
13.4
8.7
8.1
8.9
13.2
8.6
7.3
7.1
11.5
15.5
7.0
6.6
18.4
6.5
6.0
6.7
20.4
4.9
39.0
8.2
10.1
12.6
7.0
7.2
37.5
4.8
7.9
6.1
10.1
6.9
12.8
9.3
8.2
8.9
4.5
12.6
16.8
%40Ar*
99.6
91.9
98.8
84.3
97.5
99.2
98.7
96.2
99.3
99.5
99.7
99.6
71.1
99.6
99.9
100.0
98.8
83.9
98.8
99.5
99.7
99.1
86.1
96.7
99.3
99.2
99.0
98.8
98.0
99.5
97.3
98.8
99.4
99.7
98.0
98.1
97.4
96.4
99.2
99.8
99.8
88.8
99.5
91.9
99.3
97.6
99.2
99.7
99.8
99.8
99.8
99.6
91.4
99.8
99.2
98.4
81.8
99.9
99.8
99.9
99.6
97.6
Age
(Myr)
1784
1650
1716
1703
1661
2518
2018
1712
1703
2501
1776
1713
1431
1668
1708
1709
1719
376
1452
1897
1682
2546
1507
2724
1670
1638
1611
1758
1717
2677
1677
1690
1756
2576
1770
1722
1682
1661
1682
1694
1771
517
1575
1595
2540
1819
1718
1684
1650
2175
1689
1765
1783
1772
1758
1753
1560
1726
1722
1714
1682
1717
7
Depth
(cm)
Age
(14C ky BP)
Ca/K
9
12
5
9
12
10
16
8
18
12
12
13
60
18
12
47
21
26
5
7
6
21
61
24
6
10
8
15
12
21
15
13
20
16
18
15
8
26
12
10
11
16
12
46
12
28
5
4
5
11
8
6
11
5
6
9
8
5
8
6
8
12
94
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
98
98
98
98
98
98
98
98
98
98
98
98
98
98
98
98
98
98
98
100
100
100
100
100
30.1
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
30.8
31.4
31.4
31.4
31.4
31.4
31.4
31.4
31.4
31.4
31.4
31.4
31.4
31.4
31.4
31.4
31.4
31.4
31.4
31.4
32.1
32.1
32.1
32.1
32.1
30.2
8.1
17.5
7.6
22.9
10.6
9.3
5.6
7.4
8.6
19.8
20.4
5.6
7.9
7.5
9.1
13.5
4.9
12.7
20.2
11.4
3.9
35.7
5.3
30.9
3.9
18.9
5.4
9.8
6.1
29.0
7.2
28.5
8.1
6.1
12.9
18.1
6.5
23.4
8.0
8.3
8.6
5.7
18.3
7.7
8.3
8.0
7.3
6.7
6.4
5.8
14.7
17.3
18.3
8.3
15.2
6.4
7.0
13.9
7.1
7.3
7.1
%40Ar*
97.1
99.7
98.9
99.6
94.8
97.2
95.9
99.3
84.6
97.6
98.4
99.4
99.7
99.5
99.6
92.4
99.6
99.7
98.8
98.1
98.7
99.7
99.2
99.8
99.3
99.6
100.3
99.7
99.7
99.4
99.7
99.5
97.6
99.5
99.8
99.7
101.3
100.3
99.7
99.8
99.6
98.2
99.7
99.4
99.4
99.8
99.7
99.6
99.9
97.1
99.8
99.4
98.7
97.6
99.8
99.6
99.8
99.1
97.3
99.6
99.7
100.0
Age
(Myr)
1696
1760
1700
2046
1712
1133
1747
1654
1517
1794
1765
1609
1491
2086
1761
1702
1780
1693
1662
1719
1732
1719
1642
1663
1760
1827
2720
1633
2760
1650
1646
1717
1466
1689
1657
1758
1794
1743
1792
1811
1757
1768
2582
1788
1741
1730
1755
1705
1716
1792
1745
1696
1728
2342
1793
1701
1780
1735
1710
1768
1825
1715
7
28
6
9
6
8
5
8
7
8
8
18
8
4
10
7
14
9
6
19
14
11
25
28
8
31
21
73
7
13
11
21
13
37
13
7
20
48
14
5
7
14
11
11
10
12
10
8
5
8
8
11
14
10
28
12
17
15
8
18
6
10
8
S.R. Hemming, I. Hajdas / Quaternary International 99-100 (2003) 29–43
40
Table 3 (continued)
Table 3 (continued)
%40Ar*
Depth
(cm)
Age
(14C ky BP)
Ca/K
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
102
102
102
102
102
102
102
102
102
102
102
102
102
102
102
102
102
102
102
102
102
102
102
102
102
102
102
102
32.1
32.1
32.1
32.1
32.1
32.1
32.1
32.1
32.1
32.1
32.1
32.1
32.1
32.1
32.1
32.1
32.7
32.7
32.7
32.7
32.7
32.7
32.7
32.7
32.7
32.7
32.7
32.7
32.7
32.7
32.7
32.7
32.7
32.7
32.7
32.7
32.7
32.7
32.7
32.7
32.7
32.7
32.7
32.7
7.3
8.0
16.5
10.3
4.6
9.6
10.9
25.9
6.7
10.3
23.2
9.5
5.4
7.6
9.9
13.0
7.9
3.3
8.7
6.5
8.4
32.8
5.9
8.8
12.1
11.7
9.2
7.9
5.7
13.7
6.8
8.3
13.0
9.1
9.6
26.0
14.6
28.3
7.2
11.5
19.3
8.7
7.9
6.7
98.3
99.9
92.6
101.4
100.3
100.5
99.9
89.1
94.7
99.7
99.0
95.8
98.6
99.1
98.4
94.6
99.3
99.7
99.6
99.7
99.1
98.2
99.2
99.8
99.4
99.1
99.0
99.4
99.4
97.1
99.4
100.0
98.7
100.6
99.6
98.4
100.1
96.2
95.6
99.3
95.1
99.1
91.7
97.2
106
106
106
106
106
106
106
106
106
106
106
106
106
106
106
106
106
34.0
34.0
34.0
34.0
34.0
34.0
34.0
34.0
34.0
34.0
34.0
34.0
34.0
34.0
34.0
34.0
34.0
10.0
14.8
8.3
8.7
13.2
7.5
11.5
16.4
18.9
9.0
13.6
11.1
9.9
7.9
7.5
15.2
6.2
99.7
99.6
99.6
99.4
99.8
99.5
96.8
99.4
100.0
100.1
79.8
99.8
99.8
99.9
99.6
99.7
98.9
7
Depth
(cm)
Age
(14C ky BP)
Ca/K
1815
1740
1812
1778
1711
1704
1674
1950
1693
1707
1926
1691
2161
1792
1784
1510
1728
1616
1743
2647
1690
1589
1736
1683
1703
1842
1750
1839
1736
2590
1742
1774
1771
1768
1855
1870
1739
1757
1688
2633
1663
1660
1675
1605
31
8
19
54
9
23
24
61
14
12
19
29
15
11
8
28
4
4
9
8
6
44
12
27
12
31
6
9
8
31
10
11
17
26
34
50
28
22
8
16
11
17
14
10
106
110
110
110
110
110
110
110
110
110
110
110
110
110
110
114
114
114
114
114
114
114
114
114
114
114
114
114
114
114
114
114
126
126
126
126
126
126
126
126
126
126
126
34.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
15.0
9.8
14.5
8.1
3.3
5.9
17.3
7.3
7.2
8.3
8.3
12.8
21.2
14.4
16.0
10.1
20.4
7.2
36.3
24.0
12.9
19.4
8.2
9.8
11.5
10.2
7.4
8.7
10.5
9.7
8.4
9.1
19.6
15.0
7.7
10.4
8.4
36.3
26.6
12.8
9.9
9.7
8.4
99.4
99.2
100.0
99.9
94.6
99.4
99.6
99.7
99.4
99.2
99.4
100.1
98.8
100.3
99.2
99.6
98.8
99.8
99.6
99.3
99.5
99.4
99.4
99.6
99.5
99.6
99.0
99.4
99.9
99.8
99.8
99.8
99.5
99.7
99.7
99.9
99.4
93.7
99.5
97.5
99.7
98.5
99.4
1777
1619
1764
1819
2953
1748
1784
1688
1664
1680
1800
1543
1718
1687
1784
1749
1932
1806
1748
2122
1728
1716
2689
1789
1726
1708
1788
1717
2553
1723
1727
1819
1722
1840
1743
2605
1668
1825
2249
1730
1914
1706
1735
22
19
12
18
57
7
35
11
15
11
11
15
20
22
10
6
11
6
12
7
5
11
9
8
9
6
10
9
18
10
6
7
5
6
4
6
4
105
9
8
6
6
6
1761
1724
1711
1761
1709
1998
1731
1734
1683
1780
1708
1898
1913
1734
1727
1782
1696
7
5
6
10
9
7
9
26
15
7
17
12
7
15
8
12
8
128
128
128
128
128
128
128
128
128
128
128
128
128
128
128
128
128
128
36.2
36.2
36.2
36.2
36.2
36.2
36.2
36.2
36.2
36.2
36.2
36.2
36.2
36.2
36.2
36.2
36.2
36.2
8.4
15.2
24.7
20.1
14.1
8.3
9.0
10.6
9.9
8.1
7.4
8.2
30.9
7.1
10.9
10.3
7.8
17.5
99.6
99.0
83.5
99.6
98.6
99.4
99.2
96.9
99.6
99.2
99.9
99.2
99.4
99.8
98.8
99.4
100.0
85.8
1826
1758
392
1696
949
1759
1731
1759
1755
1690
1692
1698
1767
1728
1819
1754
1777
461
4
7
6
6
5
5
6
7
10
6
8
9
21
7
10
7
8
13
Age
(Myr)
%40Ar*
Age
(Myr)
7
S.R. Hemming, I. Hajdas / Quaternary International 99-100 (2003) 29–43
41
Table 3 (continued)
Depth
(cm)
Age
(14C ky BP)
Ca/K
128
128
128
128
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
132
134
134
134
134
134
134
134
134
134
134
134
134
134
134
134
134
134
134
134
36.2
36.2
36.2
36.2
38.2
38.2
38.2
38.2
38.2
38.2
38.2
38.2
38.2
38.2
38.2
38.2
38.2
38.2
38.2
38.2
38.2
38.2
40.1
40.1
40.1
40.1
40.1
40.1
40.1
40.1
40.1
40.1
40.1
40.1
40.1
40.1
40.1
40.1
40.1
42.1
42.1
42.1
42.1
42.1
42.1
42.1
42.1
42.1
42.1
42.1
42.1
42.1
42.1
42.1
42.1
42.1
42.1
42.1
5.9
22.2
17.8
9.2
13.6
10.8
6.6
33.5
11.8
35.1
14.8
8.6
3.9
7.4
8.9
13.9
6.7
25.8
32.9
7.3
7.1
7.1
18.9
7.0
8.8
6.8
9.8
25.5
8.7
6.5
26.4
7.7
8.3
39.7
29.5
9.1
10.2
7.2
7.9
6.5
30.2
14.9
24.2
7.6
7.5
14.5
14.7
7.8
4.9
7.7
11.6
9.0
11.1
8.7
11.1
18.8
6.0
11.9
%40Ar*
96.2
98.1
98.3
98.8
99.5
100.0
99.9
99.7
99.8
92.7
99.7
99.7
96.3
98.9
99.7
99.8
99.6
98.0
93.5
99.9
99.7
99.9
99.1
99.7
99.4
99.7
99.8
99.4
100.0
99.9
99.6
99.8
98.8
97.0
84.2
99.8
99.8
99.3
99.3
99.7
99.4
99.6
99.5
99.8
99.7
99.1
99.6
99.3
99.0
98.5
99.1
98.7
99.6
99.0
99.3
97.7
99.6
97.1
Age
(Myr)
1495
1734
2271
1771
1752
1737
1746
1787
2612
2312
1734
1759
1539
1767
1832
1914
1862
1706
1656
1730
1738
1804
1843
1688
2595
1700
2631
2047
2625
1710
1758
1800
1770
1751
1852
1759
1728
2585
1755
2033
2249
2057
2684
1740
1672
2153
2704
1736
532
1820
1727
1773
1701
1725
1799
1650
1838
1726
7
7
35
19
10
4
6
5
9
10
17
6
8
42
9
7
11
8
10
22
5
5
8
7
5
7
5
6
14
13
6
16
8
7
24
24
10
7
11
6
3
7
5
15
6
6
8
8
7
4
9
9
9
8
9
11
14
6
13
about the duration of Heinrich layers, from estimates
that they were virtually instantaneous, to estimates of
1000 years or more. Currently available published
Fig. 2. Stratigraphy of core V23-14 based on numbers of foraminifera/
gram (top), fraction of >63 mm size (middle), and numbers of lithic
grains/gram (bottom). Intervals of Heinrich layers H1–H5 are shaded.
Fig. 3. C-14 age-depth model for core V23-14 based on measurements
as well as the locations of Heinrich layers, and ages determined from
other sources (Table 2).
results of dating and flux methods used do not allow
clearly constraining these estimates, although one pair
of 14C estimates on either side of H2 are analytically
indistinguishable from core SU90-09 (F. Grousset, Pers.
Comm., 2001; IRD data for this core are published in
Grousset et al., 2001). We take the very pure provenance
of the Heinrich layers in eastern Atlantic core V28-82 to
indicate close to instantaneous deposition of the detritus
in order to swamp out other contributions (Hemming
et al., 1998). By lumping the Heinrich layer samples into
42
S.R. Hemming, I. Hajdas / Quaternary International 99-100 (2003) 29–43
Fig. 4. Scatter plot of measured hornblende age in Myr (x-axis)
plotted with depth (y-axis) in core V23-14. The positions of Heinrich
layers are indicated. The two vertical lines labeled ‘‘C’’ show the range
of 40Ar/39Ar ages (1650–1900 Myr) considered to represent the
Churchill Province (Gwiazda et al., 1996b; Hemming et al., 1998,
2000a).
a small interval, and plotting the cumulative fraction
data against estimated age, we emphasize the ambient
evolution of the Laurentide ice sheet (Fig. 6).
Between 42.5 and 26 14C kyr, there is little evidence of
iceberg contributions from Laurentian sources south of
551N which should provide dominantly Grenville and
Appalachian ages (Fig. 1). In contrast, between 26 and
14 14C kyr, there is abundant evidence of contributions
from this sector. Finally, between 14 and 6 14C kyr,
Grenville and Appalachian ages are again absent. These
observations are consistent with the results of Hemming
et al. (2000b) from Orphan Knoll in the interval above
H2. They are also consistent with the observations of
Ruddiman (1977), who presented IRD fluxes across the
North Atlantic in several time intervals, including 40–
25, and 25–13 kyr. The average flux appears to be
approximately double the 40–25 kyr flux in the 25–
13 kyr interval, and there is an overall correspondence
between the flux of IRD and the extent of the Northern
Hemisphere ice sheets (Ruddiman, 1977).
Fig. 5. Histogram plots of hornblende populations in different
segments of core V23-14, as labeled on graph.
evolution of ice sheets of the northwest Atlantic margin
since 43 kyr. Between Heinrich layers H5 and H3 (MIS
3), it appears that the ice sheet (or sheets) was (were) not
extended far enough southeast to drop iceberg deposits
with Grenville or Appalachain derivation into the North
Atlantic. Between H3 and H1 (MIS 2), and outside the
Heinrich layers, significant portions of the hornblende
grains have ages indicating derivation from the southeastern sector, and thus indicate a significant expansion
at about 26 14C kyr. After H1 (MIS 1), no detritus
attributable to the southeastern sector is found, and
judging from the present day situation, most of the IRD
was likely derived from the Greenland ice sheet in the
Holocene interval.
Acknowledgements
5. Conclusion
Results from studies of the ice rafted detritus
population from core V23-14 provide insights into the
Thanks go to Millie Mendelson for counting the
samples, and for picking foraminifera for 14C dating,
Elizabeth Clark for picking hornblende grains, and
S.R. Hemming, I. Hajdas / Quaternary International 99-100 (2003) 29–43
Fig. 6. Down-core plot as a function of age of the hornblende
populations from core V23-14. Heinrich layers are indicated by the
dashed lines. Ages are reported in Table 3, and the geological
subdivisions used are discussed in the text.
Wally Broecker for supporting the 14C analyses. Thanks
to Patty Catanzaro for drafting help with the figures.
Discussions with Wally Broecker, Roberto Gwiazda,
Jerry McManus, Sean Higgins, Donny Barber, and
Ralph Stea have added valuable insights. Editorial
comments were made for the journal by C. Periera and
N. Catto. This research was supported by NSF Grant
OCE 99-07290. Support for the curating facilities of the
Lamont-Doherty Earth Observatory Deep-Sea Sample
Repository is provided by the National Science Foundation through Grant OCE94-02150 and the Office of
Naval Research through Grant N00014-I-0186. This is
Lamont-Doherty Earth Observatory contribution 6369.
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