Chemical Geology 182 Ž2002. 583–603
www.elsevier.comrlocaterchemgeo
40
Arr39Ar ages and 40Ar ) concentrations of fine-grained sediment
fractions from North Atlantic Heinrich layers
S.R. Hemming a,b,) , C.M. Hall c , P.E. Biscaye a , S.M. Higgins a,b, G.C. Bond a ,
J.F. McManus d , D.C. Barber e,1, J.T. Andrews e, W.S. Broecker a,b
b
a
Lamont-Doherty Earth ObserÕatory, Columbia UniÕersity, Palisades, NY 10964, USA
Department of Earth and EnÕironmental Sciences, Columbia UniÕersity, Palisades, NY 10964, USA
c
Department of Geological Sciences, UniÕersity of Michigan, USA
d
Woods Hole Oceanographic Institute, USA
e
INSTAAR, UniÕersity of Colorado, USA
Accepted 15 June 2001
Abstract
New KrAr ages based on 40Arr39Ar incremental heating of - 2- and 2–20-mm size fractions of the well-characterized,
carbonate-bearing Heinrich layers of core V28-82 in the eastern North Atlantic are 846–1049 Ma, overlapping with
conventional KrAr ages from the same Heinrich layers on the Dreizack seamounts of 844–1074 Ma. This agreement
suggests the equivalence of the methods in fine-grained terrigenous sediments. Additionally, Heinrich layer H2 yielded a
40
Arr39Ar-based KrAr age of 970 " 4 from Orphan Knoll in the southern Labrador Sea, within the range found in eastern
North Atlantic Heinrich layers. Thus, the KrAr data are robust in their indication of a dominant Labrador Sea ice-rafted
source to even the finest sediment fraction in the eastern North Atlantic during the massive detrital carbonate-bearing
Heinrich events of the last glacial cycle ŽH1, H2, H4, H5.. Close correspondence of the radiogenic argon concentration
Ž40Ar ) . from the de-carbonated - 63-mm fractions from V28-82 with the - 2- and 2–16-mm fractions from the Driezack
seamounts demonstrates that this measurement is a rapid and reliable method for correlating these layers within their belt of
distribution.
A 40Arr39Ar-based KrAr age of 433 " 5 million years for H11 in V28-82 is within the range of published data from
background sediments in the eastern North Atlantic, and is consistent with published results across this interval in the
Driezack seamounts. In contrast, the 40Arr39Ar-based KrAr age of H11 in the western Atlantic core EW9303-JPC37 is
614 " 5 million years. A brick red sample from approximately the interval of H3 of core EW9303-GGC40 yielded a
40
Arr39Ar-based KrAr age of 567 " 1 million years, comparable to the published range of 523–543 Ma from the 2–16-mm
fractions from that interval on the Dreizack seamounts. Both JPC37 and GGC40 are located in the path of the North Atlantic
Drift. The older ages from western samples of H3 and H11 may result from dilution of a Hudson Strait source or an elevated
age from southeastern Laurentide sources. q 2002 Elsevier Science B.V. All rights reserved.
Keywords: Heinrich layers; KrAr; 40Arr39Ar; Provenance; North Atlantic; Ice-rafted detritus
)
Corresponding author. Lamont-Doherty Earth Observatory, Columbia University, Geochemistry Building, P.O. Box 1000r61, Route
9W, Palisades, NY 10964, USA. Tel.: q1-845-365-8417; fax: q1-845-365-8155.
E-mail address: [email protected] ŽS.R. Hemming..
1
Present address: Geology Department, Bryn Mawr College.
0009-2541r02r$ - see front matter q 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 0 9 - 2 5 4 1 Ž 0 1 . 0 0 3 4 2 - 4
584
S.R. Hemming et al.r Chemical Geology 182 (2002) 583–603
1. Introduction
The Heinrich events of the North Atlantic are
recognized as prominent layers, rich in ice-rafted
detritus ŽHeinrich, 1988.. They appear to have formed
from massive discharges of icebergs from the Hudson Strait, leaving high concentrations of lithic grains,
including abundant detrital carbonate ŽAndrews and
Tedesco, 1992; Bond et al., 1992; Broecker et al.,
1992.. They are important as they may be related to
extreme climate events worldwide Že.g., Broecker,
1994.. Heinrich layers have anomalous magnetic
properties Že.g., Grousset, 1993; Dowdeswell et al.,
1995; Robinson et al., 1995; Stoner et al., 1996., and
are also recognizable by many different measures of
provenance based on geochemical and isotopic com-
positions ŽHuon and Ruch, 1992; Jantschik and Huon,
1992; Grousset, 1993; Huon and Jantschik, 1993;
Francois and Bacon, 1994; Thomson et al., 1995;
Gwiazda et al., 1996a,b,c; Revel et al., 1996; Hemming et al., 1998, 2000a,b; McManus et al., 1998;
Snoeckx et al., 1999.. These distinctive characteristics make them easy to trace within the ice-rafting
belt ŽRuddiman, 1977. of the North Atlantic ŽFig. 1..
1.1. Isotopic proÕenance studies of fine-grained sediments
Terrigenous clastic sediments represent a mixture
of minerals that variably record the geologic events
in the sediments’ source terrain, including the sedimentary processes by which they are eroded and
Fig. 1. Map of the North Atlantic, modified from Hemming et al. Ž1998., showing the locations of cores used in this study as well as the
area of the original work on the Heinrich layers ŽHeinrich, 1988; Jantschik and Huon, 1992.. Labels indicate the core name, and Heinrich
layers sampled from that core in parentheses. The contours are the isopachs at 10-cm intervals of Heinrich layer H2. The dashed arrows are
the general surface circulation pattern in the North Atlantic ŽRuddiman, 1977; Bond et al., 1992.. Patterned area on the continents marks that
outcrop extent of Paleozoic carbonate deposits ŽBond et al., 1992.. The following initials indicate the location of important places:
BI—Baffin Island, GSL—Gulf of St. Lawrence, HB—Hudson Bay, HS—Hudson Strait, L—Labrador, N—Newfoundland, NS—Nova
Scotia, Q—Quebec. The Dreizack area includes cores ME68-89 and NOAMP site 59 Žsee text for discussion..
S.R. Hemming et al.r Chemical Geology 182 (2002) 583–603
transported to their sites of deposition. Additionally,
it is most common that terrigenous clastic sediments
are mixtures of multiple distinctive geological source
terrains Že.g., Taylor and McLennan, 1985; McLennan et al., 1990, 1993.. These simple facts mean that
any bulk measurement of sediments is a record of
some integrated geological signal. In order to directly measure ice-rafted contributions with confidence it is necessary to separate out individual grains
for measurement Že.g., Gwiazda et al., 1996a,c;
Hemming et al., 1998, 2000a.. Analysis of individual
grains provides an unmatchable degree of understanding about the number and nature of ice-rafting
sources, but the large number of analyses required
for a single sample limits the number of samples that
can be studied in this way. Another way of deconvolving the geological complexity of sediment
sources is to measure multiple isotopic systems with
different sensitivity to geological processes Že.g.,
McLennan et al., 1993.. Using a combination of Pb
isotope analyses of individual grains of feldspar and
40
Arr39Ar ages of individual feldspars, and bulk
sediment analysis of Pb, Nd and Sr isotopes from the
- 63-mm fraction from Heinrich layers H1, H2, H4
and H5, Hemming et al. Ž1998. made the case that
the bulk of the detritus in these Heinrich layers in
eastern Atlantic core V28-82, even in the - 63-mm
fraction, was derived from the Churchill Province
which floors the Hudson Strait ŽFig. 1..
585
relative to other samples from Dreizack core ME-6889 ŽFig. 2.. The ages measured for Heinrich layers
are approximately one billion years Ž809–898 and
899–1141 Ma for the - 2- and 2–16-mm fractions,
respectively., in contrast to the fine fractions from
the background detritus and from Heinrich layers
H3, H6 and H11, which give 350–620 million year
KrAr ages ŽJantschik and Huon, 1992.. No 14 C ages
or measures of ice-rafted detritus Žbesides the KrAr
ages. were reported by Jantschik and Huon Ž1992.
for this core, and the Younger Dryas was not recognized by Heinrich Ž1988. or Jantschik and Huon
Ž1992.. Accordingly, exact agercorrelation assignments for these samples are not possible based on
1.2. K r Ar analyses from the Dreizack area, eastern
North Atlantic
One of the earliest geochemical approaches employed to study the provenance of the Heinrich
layers was the KrAr age of the fine fraction of
sediments from the Dreizack seamount area ŽFigs. 1
and 2. in the eastern North Atlantic Ocean ŽJantschik
and Huon, 1992.. KrAr ages of fine detritus most
likely represent a mixture of source ages, and thus
are apparent ages. Throughout the rest of this paper,
we will use the expression KrAr ages while recognizing this complexity. Because of the fine grain
sizes analyzed by Jantschik and Huon Ž1992. of - 2
and 2–16 mm, these sediments could have been
transported to that site by a variety of sedimentary
processes. However, the KrAr ages of Heinrich
layers H1, H2, H4, and H5 stand out dramatically
Fig. 2. Stratigraphy of %IRD from cores V28-82 Ždata from
Gwiazda et al., 1996b; McManus et al., 1998., and ME69-17
ŽDreizack, data from Heinrich, 1988.. Also shown is the stratigraphic variation of the KrAr ages of the 2–16- and - 2-mm
fractions from core ME68-89 ŽDreizack, data from Jantschik and
Huon, 1992., and the downcore variations in the 40Ar ) concentrations from ME69-17 ŽJantschik and Huon, 1992. and V28-82 Žthis
study..
586
S.R. Hemming et al.r Chemical Geology 182 (2002) 583–603
published data. However, accepting more recent estimations of Heinrich layer ages ŽBond and Lotti,
1995; Jeff Dorale personal communication, 2000., it
is possible to construct a reasonable age–depth model
for the Jantschik and Huon Ž1992. data ŽFig. 3.. It
appears, based on this reassessment of the stratigraphy, that Younger Dryas, H3, and H6 layers have
slightly older KrAr ages compared to the background, especially in the 2–16-mm fraction. If the
Younger Dryas is at 10–12 cm, H3 is at 110–112
cm, and H6 is at 261–293 cm, then the comparison
is 523–620 vs. 428–504 Ma in 2–16-mm fraction
and 469–496 vs. 350–427 Ma in - 2-mm fraction
for these intervals compared to background values.
Although they were uncertain about its designation as Younger Dryas or H1 due to uncertainties in
the age assignments, Huon and Ruch Ž1992. provided 14 C dates across the Holocene from 2.7 to 10.7
14
C ka BP at NOAMP site 59. At this site, they
recorded an excursion to 933 Ma in the 2–16-mm
fraction at about 10 14 C ka BP Accordingly, it
appears that detritus transported to the Dreizack region during the Younger Dryas has a composition
very similar to that of H1, H2, H4 and H5 ŽJantschik
and Huon, 1992.. The intermediate ages of up to 583
Ma near the top of core ME-68-89 may represent
mixing of sediments with ambient and Heinrich layer
provenance as the sedimentation rate dropped from
about 5.2 cmrka between 12 and 65 ka to less than
1 cmrka after 12 ka ŽFig. 3.. At site 59, the Younger
Dryas is between 25 and 30 cm, and thus the
Holocene sedimentation rate is at least double that of
ME-68-89.
Because the massive Heinrich layers are so rich in
ice-rafted detritus, it is reasonable to infer that a
large fraction of the very fine-grained material in
these layers could be composed of glacial flour
derived from old basement rocks. The content of
hornblende, feldspar, and mica is relatively high
within the fine sediment fractions of Heinrich layers
ŽJantschik and Huon, 1992.. However, clay minerals
are still dominant and indicate a significant reworked
sedimentary source.
1.3. Goals of the study
The present study was undertaken to test the
alternative hypotheses of Ž1. sediment mixing at the
ice-rafted detritus source region or Ž2. mixing between an older ice-rafted detritus source region with
Fig. 3. Age–depth correlation for core ME68-89 from the Dreizack area ŽFig. 1.. This core was studied by Jantschik and Huon Ž1992..
Based on published ages of Younger Dryas and Heinrich layers H1, H2, H3, H4, H5, H6 and H11, and the locations of H1, H2, H4 and H5
Žsolid circles, for the clearly distinguishable Heinrich layers with ca. 1 Ga KrAr age. in this core, the estimated locations of YD, H3, H6
and H11 are shown Žopen squares..
S.R. Hemming et al.r Chemical Geology 182 (2002) 583–603
a background sedimentary input of approximately
400 Ma detritus ŽHurley et al., 1963; Jantschik and
Huon, 1992.. A second goal was to determine if
Heinrich layers H3 and H11, which do not exhibit
extremely old ages in the eastern North Atlantic,
have distinctive ages in the western North Atlantic.
An additional goal was test the value of the 40Arr39Ar
system in tracking the sediment provenance of the
fine fraction. The much larger samples measured for
conventional KrAr are problematic for low blank,
high sensitivity 40Arr39Ar mass spectrometry systems, and we were curious about what patterns incremental heating would reveal.
2. Samples and analytical methods
This study was a pilot project designed to test the
utility of the 40Arr39Ar incremental heating method
for tracing the provenance of the fine sediment fraction, and we analyzed only a limited number of
samples. Nine samples were selected for 40Arr39Ar
experiments, and core locations are shown in Fig. 1.
Samples from Heinrich layers H1, H2, H4 and H11
were taken from core V28-82 Ž49827X N, 22816X W,
3935 m.. The stratigraphy in this core ŽFig. 2. is
well-documented in several published studies
ŽGwiazda et al., 1996a; McManus et al., 1998; Hemming et al., 1998. and is shown in Fig. 2. Samples
from H2 were also taken from cores EW9303-GGC29
from Orphan Knoll Ž50.238N, 46.528W, 1845 m. and
HU87-033-009 from the SE Baffin Island slope
Ž62831X N, 59827X W, 1437.. The GGC29 sample was
selected on the basis of carbonate content and comparison with nearby core GGC31 from the same
cruise ŽBond and Lotti, 1995; Bond, unpublished
data.. Heinrich layer H2 from HU87-033-009 core is
documented in several publications Že.g., Andrews
and Tedesco, 1992.. A sample of H11 was taken
from core EW9303-JPC37 Ž43.68N, 46.28W, 3981
m.. The location of the detrital peak with maximum
number of lithic grains per gram in the coarse fraction at Termination II is designated as H11 ŽMcManus, 1997.. A sample from approximately H3 was
taken from a dominantly brick red layer in core
GGC40 Ž41.658N, 51.028W, 3725 m.. The assignment of this layer to H3 is based on bracketing
radiocarbon ages of 22.7 and 27.0 ka Žwith y400
587
year reservoir correction. and a small IRD peak with
a prominent increase in detrital carbonate of about
20% ŽBond, unpublished data..
Samples were prepared for clay mineralogy following the procedure of Biscaye Ž1965.. This procedure consists of three leaching steps to sequentially
remove carbonate, ferromanganese coatings and opal,
and is designed to disaggregate the clays to single
crystallites. Mineralogical compositions of the - 2and 2–20-mm fractions were determined at LDEO
by X-ray diffraction using a Philips X’PERT MPD
X-ray.
Small fractions of the samples were taken from
the X-ray diffraction mounts and prepared for
40
Arr39Ar measurements at University of Michigan.
First, powders from the mounts were centrifuged
down in water in a micro-centrifuge tube. Then, the
water was poured off and the sample dried. A small
clump, much less than 1 mg, was loaded into a
quartz glass tube and evacuated and sealed according
to the procedure of Dong et al. Ž1995. and Hall et al.
Ž1997.. Samples were packaged with abundant monitor standards ŽMmhb, 520.4 Ma, Samson and
Alexander, 1987. spaced throughout the package in
order to quantify the flux at a particular spot in the
package. The package was irradiated for 60 h in
location L67 at the Phoenix-Ford Memorial Laboratory reactor at the University of Michigan.
40
Ar– 39Ar incremental heating of the clay fraction
has advantages over the conventional KrAr method
because it can be used with extremely small samples,
and a KrAr ratio is measured rather than concentrations on separate aliquots. However, it has the potential weakness of recoil loss of argon during irradiation. By encapsulating the samples in a fused silica
tube evacuated to 1 = 10y8 Torr, any argon lost
during recoil can be retained and measured prior to
incremental heating. Thus, an age equivalent to a
conventional KrAr age can be obtained. In principle, additional information may come from step heating the sample ŽDong et al., 1995., although because
of the inherent mixture of minerals and sources in
these sediments, reviewed above, the spectra are not
simple, and may have multiple age interpretations.
40
Arr39Ar measurements were made at the University of Michigan, following the procedure described by Dong et al. Ž1995. and Hall et al. Ž1997..
The irradiated fused silica ampoules were broken
588
Corerdepth Žcm.
V28-82r60 ŽH1.
V28-82r98 ŽH2.
V28-82r197.5 ŽH4.
V28-82r530 ŽH11.
GGC29r108 ŽH2.
GGC40r155 ŽH3.
JPC37r1280 ŽH11.
HU87-009r660 ŽH2.
Sample
weight Žg.
Wt. rec.a
Žg.
20–63 mm
Ž%.
2–20 mm
Ž%. b
- 2 mm
Ž%. b
- 2 mm
KrC S Ž%.
I Ž%.
K Ž%.
C Ž%.
ArI
Artotal
clay
0.25307
0.20180
0.25772
0.25122
0.25670
0.25238
0.26748
0.27035
0.05118
0.07099
0.10360
0.13501
0.09325
0.11879
0.09564
0.08562
37.48
36.61
33.40
34.82
53.35
1.09
22.63
54.45
54.71
55.64
49.23
38.15
37.53
63.98
48.62
31.53
7.82
7.75
17.4
27.0
9.12
34.9
38.8
14.0
1.30
0.92
0.55
1.00
0.50
0.20
0.69
0.78
51
40
25
44
24
42
37
23
28
29
14
23
13
8
22
21
22
31
26
23
26
39
31
27
0.13
0.34
0.40
0.04
0.37
0.16
0.21
0.38
0.017
0.034
0.025
0.004
0.022
0.017
0.020
0.022
0
0
35
10
38
11
10
29
2–20 mm
KrC KrI
CrI
ArI
0.28
0.23
0.57
0.76
0.34
0.38
0.44
0.46
1.9
2.8
1.7
1.1
1.8
1.3
1.5
1.8
0.79
0.89
0.56
0.04
0.53
0.03
0.16
0.55
K—kaolinite, C—chlorite, S—smectite, I—illite, A—amphibole.
a
Wt. rec. is the weight recovered after leaching procedure to remove carbonate, ferromanganese oxides and hydroxides and opal ŽBiscaye, 1965..
b
Italicized size fractions have 40Arr39Ar measurements.
0.54
0.64
0.99
0.87
0.63
0.48
0.68
0.82
S.R. Hemming et al.r Chemical Geology 182 (2002) 583–603
Table 1
Sample weights, size fractions and X-ray diffraction mineralogy of samples from this study
Table 2
Summary of 40Arr39Ar and 40Ar ) results from clay fractionsa
Size range
Žmm.
V28-82 60 cm ŽH1.
Žrep.
V28-82 98 cm ŽH2.
Žrep.
2–20
2–20
-2
-2
2–20
-2
2–20
-2
2–20
-2
-2
-2
2–20
-2
2–20
-2
V28-82 197 cm ŽH4.
V28-82 530 cm ŽH11.
GGC29 108 cm ŽH2.
Žrep.
GGC40 155 cm ŽH3.
JPC37 1280 cm ŽH11.
HU-009 660 cm ŽH2.
a
"
%
Recoil
846
2
3.0
871
1.29
1059
3
8.3
1147
0.41
983
5
3.5
1017
1.23
996
4
4.1
1037
0.47
433
970
5
4
9.4
6.8
474
1036
0.11
0.32
567
1
4.1
590
0.29
614
419
5
10
16.2
81
713
1445
0.37
56.80
Total gas
age ŽMa. b
Retention
age ŽMa. c
Full data set is in Appendix A.
Total gas age is the weighted average of all steps, including the recoil gas.
c
Retention age is the weighted average of all heating steps but does not include the recoil gas.
d
Sample weights for 40Ar ) concentration measurements.
e
Model age assumes 3 wt.% K.
b
Bulk
CarK
Sample
wt. Žmg. d
40
KrAr model
age ŽMa. e
0.3292
0.0186
0.1391
0.4627
0.0186
0.5637
1.06=10ey08
4.82=10ey09
7.88=10ey09
6.83=10ey09
4.82=10ey09
6.79=10ey09
1361
746
1097
984
746
980
0.8051
2.46=10ey09
419
0.0431
0.4046
0.7520
7.20=10ey09
5.89=10ey09
3.59=10ey09
1025
877
583
0.7259
5.74=10ey09
859
0.5242
7.03=10ey09
1006
Ar ) Žmolrg.
S.R. Hemming et al.r Chemical Geology 182 (2002) 583–603
Sample
589
590
S.R. Hemming et al.r Chemical Geology 182 (2002) 583–603
Fig. 4. 40Arr39 and 37Arr39Ar ŽCarK. data from the eight Awell-behavedB samples of this study. The label at the top indicates which Heinrich layer, from which core, and which
size fraction. The total gas ages and percentage of 39Ar lost through recoil are shown for each age spectrum.
S.R. Hemming et al.r Chemical Geology 182 (2002) 583–603
under high vacuum in a borosilicate glass manifold
using a ball bearing and magnet, and the intensity
and composition of released gas was measured to
assess the extent of recoil loss of 39Ar. Samples were
incrementally heated with a continuous Ar ion laser
through the glass manifold and ampoule.
In addition to the 40Arr39Ar analyses, we report
40
Ar ) concentration analyses from - 63-mm decarbonated samples as well as the fine fraction separates analyzed for clay mineralogy. For the analysis
of - 63-mm fractions, we took approximately 100
mg aliquots of the - 63-mm samples remaining
from previous work ŽGwiazda et al., 1996a; McManus et al., 1998; Hemming et al., 1998., and
removed the calcium carbonate using buffered acetic
acid as with the clay mineral preparations ŽBiscaye,
1965.. After an extra leach step to insure complete
removal of the carbonate, we rinsed the samples
three times with distilled water, and then centrifuged
approximately 5–10 mg of the samples, removed the
supernate, and allowed the sample to dry in an oven
at about 60 8C. We broke off a piece of the resulting
clump and weighed the sample into a 21-spot copper
laser disk. Weights of analyzed samples ranged from
1.5 to 6.4 mg ŽTable 3..
Samples were analyzed at LDEO on a VG5400
noble gas mass spectrometer equipped with a modified Nier ion-source and a 908 sector extended geometry. The system is fully automated using software
developed by Al Deino of the Berkeley Geochronology Center. Gasses released from the heating of
samples by CO 2 laser are scrubbed of reactive gases
such as H 2 CO 2 , CO and N2 by exposure to Zr–Fe–V
and Zr–Al sintered metal alloy getters. The remaining inert gasses, principally Ar, are then admitted to
the mass spectrometer. The mass spectrometer is
operated in static mode. Mre 36 cold procedural
blanks for both the extraction system and mass spectrometer are less than 5 = 10y1 4 cm3 STP. Desorption of 40Ar in the stainless steel wall of the vacuum
envelope is less than 1 = 10y1 2 cm3 STPrmin. The
detection limit is approximately 1 = 10y1 4 cm3 STP
Ž; 5 = 10y1 9 mol., or about 1 = 10y3 ArTorr at
200 mA trap current.
The reproducibility of the 40Ar signal as well as
the 40Arr36Ar ratio from the air pipette is about 2%.
Calibration of the sensitivity of 7.48 = 10 8 nArcm3
Ž"2.5%, 2 sm . was made with 16 measurements of
591
glauconite Ar standard GL-O ŽOdin, 1976. with
sample weights between 0.3 and 1.2 mg ŽOdin recommends using no less than 100 mg of this standard
for an analysis, but this is impractical for our work..
Based on the samples of GL-O as well as shale
standard SCO-1, we estimate a precision per individual run, i.e., 1 s external reproducibility, of between
4% and 10%. The 4% comes from the glauconite and
10% from the SCO-1. The greater uncertainty of the
solid samples compared to the air pipette is interpreted to be a product of sample heterogeneity at
such a small scale, although weighing andror extraction uncertainties cannot be ruled out. SCO-1 is a
USGS rock standard with known K but unknown Ar
concentration. We regard it as a good test of the
precision of the machine as it is a similar matrix to
the terrigenous clastic sediment fraction.
3. Results
Sample sizes and clay mineralogy data are provided in Table 1. Summary data from the 40Arr39Ar
Fig. 5. 40Arr39 Ar and
HU87-033-009.
37
Arr39 Ar ŽCarK. data from core
S.R. Hemming et al.r Chemical Geology 182 (2002) 583–603
592
and 40Ar ) analyses of the fine sediment fractions are
given in Table 2, and the full data for 40Arr39Ar
incremental heating analyses are reported in Appendix A. Age and CarK release spectra are shown
in Figs. 4 and 5. 40Ar ) concentrations of the - 63mm samples are given in Table 3 and are shown in
Table 4
Arr39Ar data from individual pelitic rock fragments from H2 in
GGC31
40
Sample Rock
depth
type
90
100
109
CarK Mol 40Ar
Ž=10 14 .
slate
0.155
slate
0.088
11schist 0.575
40.9
20.9
58.2
%40Ar )
Age "1 s
ŽMa.
99.4
98.5
99.9
459 3.6
497 3.6
1708 9.7
Table 3
Ar data from de-carbonated, -63-mm samples from core V28-82
Depth Žcm.
Žrep.
Žrep.
Žrep.
a
5
5
19
25
30
33
33
60
68
71
73
75
77
80
82
84
85
90
94
96
98
100
139
148.5
160
170
180
194
218
231
240
255
260
269
274
281
289
300
309
309
Weight
Žmg.
%atm.
40
Ar ) rg
Ž10y9 mol.
KrAr
model age
ŽMa. a
2.39
1.91
2.93
2.71
2.08
3.98
3.53
3.41
4.06
3.99
4.57
2.90
2.35
5.70
6.41
3.44
5.11
2.58
2.71
2.69
1.59
4.32
2.61
2.34
2.79
1.74
2.59
2.37
2.54
3.19
1.72
2.97
3.01
2.31
2.47
2.49
3.13
3.23
2.41
2.59
20.5
18.6
13.7
6.4
11.8
10.5
11.2
4.0
7.6
8.8
7.7
7.9
11.0
5.5
7.5
4.9
7.5
8.5
3.6
4.2
4.1
1.4
11.1
13.0
11.2
11.5
8.3
4.3
24.2
12.9
3.6
19.1
10.5
15.1
10.7
15.4
20.4
11.5
7.9
8.5
1.26
1.40
1.39
1.61
1.44
1.32
1.56
5.12
2.15
1.86
1.89
2.11
1.74
2.03
2.31
2.37
2.11
2.06
4.17
5.26
5.88
8.26
2.23
2.24
2.30
2.12
3.04
5.95
1.53
1.84
5.94
1.48
1.56
1.92
2.30
1.44
1.15
1.65
2.44
2.47
290
366
344
366
350
268
336
955
480
427
428
473
412
442
510
509
472
465
810
978
1064
1336
512
525
528
493
651
1075
423
441
1068
388
372
467
524
363
312
395
537
546
Model age assumes 3 wt.% K.
Fig. 2. Data from 40Arr39Ar analyses of individual
pelitic rock fragments from Heinrich layer H2 taken
from Orphan Knoll core EW9303-GGC31 are provided in Table 4.
4. Discussion
4.1. 4 0Ar r39Ar from Heinrich layers H1, H2 and H4
In spite of the limited data set, some important
observations appear to be robust. First, the loss to
recoil is generally low, between 3% and 16%. Also,
the release patterns for step ages as well as CarK
Žderived from the 37Arr39Ar measurement. are remarkably consistent for the detrital carbonate-bearing
Heinrich layers H1, H2 and H4 from V28-82 ŽFig.
4A–J. as well as H2 from GGC29 ŽFig. 4M,N.. The
age spectra are quite similar regardless of grain size;
however, the - 2-mm fractions have lower and more
uniform CarK Ž- 0.5; Fig. 4F,N., whereas Žexcept
for H4, Fig. 4H. the 2–20-mm fractions have relatively high CarK of approximately 2.5 for the low
temperature steps and much lower ratios at higher
temperature steps of approximately 1 ŽFig. 4B,D..
The 2–20-mm sample of H4 from V28-82 has a
CarK spectrum similar to the - 2-mm fractions
from H1 and H2 ŽFig. 4H.. Huon and Jantschik
Ž1993. also reported CarK for the same samples
analyzed for KrAr by Jantschik and Huon Ž1992..
Five - 2-mm Heinrich samples from the Dreizack
area average 0.60 " 0.07 and three 2–16-mm samples average 0.87 " 0.09 ŽHuon and Jantschik, 1993..
For comparison, one - 2-mm sample from H2 of
V28-82 has a CarK of 0.41, and three 2–200-mm
samples have CarK of 1 " 0.5.
The major exception to the beautiful reproducibility among the detrital carbonate bearing Heinrich
S.R. Hemming et al.r Chemical Geology 182 (2002) 583–603
layers comes from the - 2-mm fraction of H2 from
HU87-033-009 on the SE Baffin slope, just to the
north of Hatton Basin and Hudson Strait ŽAndrews et
al., 1998; Jennings et al., 1996. ŽFig. 1.. In this
sample, the fraction of 39Ar released due to recoil is
82%. The three heating steps each gave very different ages, ranging from 800 to 1800 Ma ŽFig. 5..
Examination of the clay mineral data in Table 1 does
not reveal an extraordinary composition for this sample. The reason for this anomalous result is unknown.
4.2. 4 0Ar r39Ar from Heinrich layers H3 and H11
We measured 40Arr39Ar ages for the 2–20-mm
fractions from two samples of Heinrich layer H11
Žon Termination II, Heinrich, 1988; McManus et al.,
1994, 1997.: one from V28-82 ŽFig. 4I,J. and the
second from JPC37 ŽFig. 4O,P.. In V28-82, H11 has
a total gas age of 433 " 5 Ma with recoil loss of
9.4% 39Ar. The age is indistinguishable from KrAr
ages for background fine-grained sediment from this
area ŽJantschik and Huon, 1992.. The CarK for H11
in V28-82 is extremely low Ž0.1., consistent with the
low amphibole to illite ratio ŽTable 1. that indicates
less fresh glacial basement rock flour in this sample
compared to H1, H2 and H4. In contrast, H11 from
JPC37 has a higher recoil loss of 16.2% 39Ar, and it
gives a total gas age of 614 " 5 Ma with CarK
ranging from about 0.5 to 0.3. This age is comparable to the slightly elevated ages from the 2–16-mm
fraction at about the H6 interval in ME-68-89
ŽJantschik and Huon, 1992.. The detrital carbonate
content in this sample is 4%, compared to ) 25%
typically found in Orphan Knoll Heinrich layers
ŽBond and Lotti, 1995, although H11 is not reported
from Orphan Knoll., and thus, the older age may be
a diluted Hudson Strait signal. This sample has a
relatively low amphibole to illite ŽArI. ratio compared to the carbonate-bearing Heinrich layers, indicative of a more clay-dominated composition.
We also measured a sample of the 2–20-mm
fraction from a brick red layer ŽH3. at 155 cm in
core GGC40. The total gas age is 567 " 1 Ma with a
recoil loss of 4.1% and the CarK ranges from 0.2 in
the low temperature steps to about 0.5 in the higher
temperature steps. Although correlations at this level
are clearly uncertain, this age is comparable to those
593
reported within that approximate interval of ME-6889 ŽJantschik and Huon, 1992.. This sample also has
a very low ŽArI.. A detrital carbonate content approaching 20% is also found in this interval ŽBond,
unpublished data., and thus, the older age may be a
diluted Hudson Strait signal.
4.3. Total gas and retention ages and incremental
heating spectra in fine-grained sediments
As noted in the Introduction, we made incremental heating analysis out of curiosity about what they
might reveal in sedimentary layers. Recoil loss accounts for 3–16% of the 39Ar from these samples
Žexcept H2 from HU87-003-009 with 82%.. Dong et
al. Ž1995. distinguished an encapsulated total gas age
from a retention age. The total gas age includes the
gas released during irradiation, known as the recoil
gas, which is dominated by 39Ar. The retention age
includes all but the recoil gas. Accordingly, the total
gas age is younger than the retention age by the
percent recoil Ar loss. Dong et al. Ž1995. considered
the total gas age to be equivalent to conventional
KrAr ages. The small difference between these two
ages in all but one sample gives greater confidence
in the overall reproducibility of our measured ages,
but to compare most directly with the conventional
KrAr data of Jantschik and Huon Ž1992., we use the
total gas ages in our discussion of provenance.
The incremental step heating experiments of Dong
et al. Ž1995. and Hall et al. Ž1997. were used to try
to date the diagenetic formation of fine clay minerals. Accordingly, they used the spectra to the detrital
signal from the authigenic signal they wished to
characterize. In the current study, the goal is to
evaluate the provenance of the detrital fraction. This
is a simpler goal in some ways, as a very small
detrital component is very difficult to avoid and has
a strong influence on the measured ages. In our
study, any authigenic component is minor and invisible in the results. Although no plateaus are evident,
the release spectra are relatively simple and uniform
looking except the sample from HU-009. The higher
temperature steps have older apparent ages than the
lower temperature steps. As sediments are surely
mixtures of minerals, and likely mixtures of different
geological terrains, it is impossible to interpret these
results in any detail. The CarK ratios are plotted
594
S.R. Hemming et al.r Chemical Geology 182 (2002) 583–603
against 40Arr39Ar ages for individual steps of all but
sample HU-009 ŽFig. 6.. Except for the 2–20-mm
fraction from V28-82 H4, the 2–20-mm fractions
show younger ages and higher CarK in early steps.
The - 2-mm fractions have low CarK throughout
and have increasing ages in the early steps and
relatively stable composition in the final 70–80% of
the gas ŽFigs. 4 and 6.. Perhaps future work on
40
Arr39Ar incremental heating data from background
sediments will reveal subtle differences in pattern
that may be significant for interpreting provenance.
4.4. Clay mineralogy
Despite the strong agreement in KrAr ages, the
clay mineralogy data from our study are not completely consistent with the results of Jantschik and
Huon Ž1992.. Samples were prepared primarily for
the 40Arr39Ar pilot study; however, XRD measurements typically reported by P. Biscaye were also
collected ŽTable 1.. Due to the lack of tabulated data
in Jantschik and Huon Ž1992., it is difficult to make
direct comparisons. However, it appears that there is
a significantly different clay mineralogy in V28-82
Heinrich layers compared to those from the nearby
Dreizack seamounts ŽJantschik and Huon, 1992.. In
particular, the kaolinite to chlorite ratio ŽKrC. is
greater than or equal to 0.5 from our - 2-mm Heinrich layer samples from V28-82, whereas they appear to be less than 0.3, and mostly considerably less
than 0.3, in the Dreizack samples. The discrepancy
appears to be largely in the kaolinite contents which
are 5% or less in the Jantschik and Huon Ž1992.
plots and 14–29% in the V28-82 Heinrich layers
ŽTable 1.. Jantschik and Huon Ž1992. used the
method of Biscaye Ž1965. to estimate the phyllosilicate contents from diffraction peak heights. However, their pre-treatment procedure was markedly
different and involved only a 10% HCl leaching
followed by grain size separations. It is expected that
if the HCl were to attack any of the clay minerals,
chlorite would be preferentially attacked relative to
kaolinite, so this does not seem to be the likely
source of discrepancy. The method of Biscaye Ž1965.
uses buffered acetic acid to remove carbonate, sodium
dithionate to remove ferromanganese oxides, and
sodium carbonate to remove opal. The goal of these
steps is to quantitatively disaggregate the sediments
to individual clay crystallites. We tentatively conclude that kaolinite may be depleted in the fine
fractions of the Jantschik and Huon Ž1992. samples
due to some of the kaolinites not being fully disaggregated. Without further work, preferably including
Fig. 6. CarK vs. 40Arr39 Ar age for individual steps from all samples except HU87-033-009. F indicates the first and L the last step, and
the steps are connected in order of analysis.
S.R. Hemming et al.r Chemical Geology 182 (2002) 583–603
Fig. 7. CarK vs. amphibolerillite for samples dated by 40Arr39Ar.
interlaboratory comparisons, it is not possible to
resolve this discrepancy.
4.5. Mineralogical controls on the Ca r K and age
spectra
Huon and Jantschik Ž1993. sought to better understand the provenance of Heinrich layer samples from
the KrAr work of Jantschik and Huon Ž1992. by
increasing the scope of the analyses to include major
and rare earth element and Rb–Sr isotopic data.
595
They found some strong geochemical trends related
to grain size and mineralogy. Jantschik and Huon
Ž1992. and Huon and Jantschik Ž1993. found a strong
separation of trends between Heinrich layer and
non-Heinrich layer samples. Within Heinrich layer
samples, they found a positive correlation between
non-clay minerals such as hornblende, plagioclase
and K-feldspar, with KrAr age, effectively indicating an increase in glacial flour of basement lithologies with increased KrAr age. We find consistent
results with our smaller data set. There is a positive
correlation between estimated amphiboliterillite and
CarK for our eight well-behaved samples ŽFig. 7..
Additionally, there is a strong separation between
detrital carbonate-bearing Heinrich layers H1, H2
and H4 compared to H3 and H11, so a plot of age
vs. CarK ŽFig. 8. or age vs. amphibolerillite yields
two populations with different ages and a range of
geochemical and mineralogical composition.
Thus, the one billion year KrAr ages measured in
the fine fraction of the detrital carbonate bearing
Heinrich layers probably represent mixtures between
1.8 billion year basement sources that are documented by 40Arr39Ar analysis of individual hornblende grains ŽGwiazda et al., 1996c; Hemming et
al., 1998, 2000a,b. and reworked Paleozoic pelitic
Fig. 8. 40Arr39Ar total gas ages vs. CarK for fine sediment samples. Also shown are 40Arr39Ar results from Younger Dryas and Heinrich
layers H1 and H3 from Orphan Knoll core GGC31 for hornblende ŽHemming et al., 2000a., feldspar ŽHemming, unpublished data. and from
H2 for pelitic rock fragments ŽTable 4..
596
S.R. Hemming et al.r Chemical Geology 182 (2002) 583–603
and metapelitic sources ŽTable 4, Fig. 8.. Ages
younger than the 1.8-Ga hornblende ages are to be
expected from ground-up feldspar and biotite from
the same sources, due to their lower blocking temperatures to diffusion of Ar ŽMcDougall and Harrison, 1988. as well as from clay minerals derived
from sedimentary rocks. Indeed, single crystal
40
Arr39Ar total fusion ages of feldspars from the
Churchill province appear to be about 400 million
years younger than the hornblende grains, with a
much larger dispersion, and there appears to be a
more substantial Paleozoic terrain contribution to the
feldspars even within Heinrich layers from Orphan
Knoll ŽFig. 8 and Hemming and Rasbury, 2000..
4.6. Labrador Sea proÕenance of the fine fraction
from Heinrich layer H2
The most important result of this study is the
observation that the KrAr signal of the detrital
carbonate bearing Heinrich layers is derived predominantly from the Labrador Sea. A direct comparison can be made with the KrAr ages from the
- 2-mm fractions of Heinrich layer H2 from core
GGC29, Heinrich layers H1, H2 and H4 in V28-82,
and H1, H2, H4 and H5 from the Dreizack seamounts
ŽFig. 1., and thus, the extent of the Labrador Sea
source contribution to the finest fraction of the eastern North Atlantic can be documented. The location
of GGC29 atop Orphan Knoll, at the outlet of the
Labrador Sea, makes it an ideal place to sample the
average composition of sediments transported by
icebergs derived from sources surrounding the
Labrador Sea. 40Arr39Ar data from hornblende grains
in Heinrich layers show a strong peak at 1.8 Ga from
both V28-82 ŽGwiazda et al., 1996c; Hemming et al.,
1998. and from Orphan Knoll ŽHemming et al.,
2000a.. 40Arr39Ar ages from individual hornblende
and Pb isotope compositions of individual feldspar
grains from Baffin Island as well as from Orphan
Knoll, V23-14 in the western North Atlantic and
V28-82 in the eastern North Atlantic indicate a
dominance of Labrador ŽHudson Strait. sources to
the ice-rafted detritus of Heinrich layers H1, H2, H4,
and H5 ŽGwiazda et al., 1996a,c; Hemming et al.,
1998, 2000a,b.. Additionally, the Pb–Nd–Sr isotope
composition of Heinrich layer samples indicates a
consistent source across the spectrum of grain sizes
ŽHemming et al., 1998..
The - 2-mm fraction of H2 at 108 cm in core
GGC29 gives a total gas age of 970 " 4 Ma Ž6.8%
recoil loss.. From 98 cm in core V28-82, the - 2-mm
fraction of H2 gives a total gas age of 1059 " 3
Ž8.3% recoil loss.. Hemming et al. Ž1998. found H1,
H2, H4 and H5 sediments to have very similar
provenance, and thus, we also compare the 40Arr39Ar
results from H1 and H4 in this context. The range of
total gas ages from the detrital carbonate-bearing
Heinrich layers from V28-82 is 846–1059 Ma ŽTable
2., completely consistent with the result from H2 on
Orphan Knoll. Because our 40Arr39Ar and 40Ar )
results from the 2–20-mm fractions of Heinrich layers from core V28-82 in the eastern part of the North
Atlantic entirely overlap the KrAr results of
Jantschik and Huon Ž1992. from the nearby Dreizack
seamounts Ž844–1074 Ma., we can extend this comparison further. In summary, our data from H2 from
GGC29 are indistinguishable from Heinrich layers in
the eastern North Atlantic, and accordingly provide
further evidence that the Labrador Sea is the dominant outlet of icebergs contributing sediments to the
detrital carbonate-bearing Heinrich layers throughout
the ice-rafted detritus belt in the North Atlantic.
5. Conclusions
The results of this study provide good evidence
that the 0.8–1-Ga KrAr ages measured for Heinrich
layers H1, H2, H4 and H5 record a provenance
mixture that was set by Labrador Sea sources. We
have demonstrated that we can reproduce the pattern
of variability of published 40Ar ) concentrations from
the Driezack seamounts in core V28-82. Thus, this
method provides a rapid and reliable tool for mapping the distribution of the detrital carbonate-bearing
Heinrich layers. The similarity of our KrAr age
estimates based on 40Arr39Ar incremental heating
methods to the conventional KrAr ages reported by
Jantschik and Huon Ž1992. demonstrates the potential of the 40Arr39Ar method for tracing fine-grained
sediment sources. The consistency of the Heinrich
layer results from eastern North Atlantic core V28-82
with Heinrich layer H2 from Orphan Knoll core
GGC29 supports the conclusion that detrital carbonate-bearing Heinrich layers from the eastern North
Atlantic are dominated by Labrador Sea iceberg
sources, even down to the finest fractions.
S.R. Hemming et al.r Chemical Geology 182 (2002) 583–603
Our results from Heinrich layers H3 and H11
indicate promise for the KrAr system in identifying
distinct sediment source compositions that may be
traceable across the North Atlantic, but further work
will be necessary to establish the geographic and
stratigraphic patterns across these intervals. In summary, one sample of Heinrich layer H3 Žfrom core
GGC29. has a 567-Ma total gas age, broadly consistent with results from the H3 layer in ME-68-89
ŽJantschik and Huon, 1992.. The sample from the
highest lithic flux interval of Heinrich layer H11 in
V28-82 is indistinguishable from ambient fine detritus from the Dreizack area and has a KrAr age
distinct from the other V28-82 Heinrich layers. However, H11 in the western North Atlantic from JPC37
has an older age, similar to the brick red ŽH3. layer
from GGC-29. Both H11 and H3 samples from the
western North Atlantic have elevated detrital carbonate contents and thus the older KrAr ages may be
diluted Hudson Strait signals. An alternative hypothesis is that KrAr ages of southeastern Laurentide
iceberg sources are also elevated relative to ambient
fine detritus in the North Atlantic, but further analyses are required to evaluate this possibility.
597
Acknowledgements
This project was funded by National Science
Foundation grants OCE-96-33554 and OCE-9907290 to SRH. The Ar lab at LDEO was funded by
grants from the NSF and the Keck Foundation.
Neutron irradiations were kindly provided by the
Phoenix-Ford Memorial Laboratory at the University
of Michigan. Thanks go to Alex Halliday for making
the University of Michigan lab facilities available for
this study. Thanks go to Adele Hanely, Alison Bond
and Marcus Johnson for help in the lab, and to
Carmen Hui and Brent Turrin for providing information on standard analyses of SCO-1 shale and GL-O
glauconite during her summer internship in 2000.
Support for the curating facilities of the LamontDoherty 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 N00014-0186. Thanks to
R.A. Duncan and an anonymous reviewer for their
critical reviews of the manuscript. This is LamontDoherty Earth Observatory contribution 6232.
Appendix A
Cum
39
Ar
Age
V28-82 60 cm 2–20 (H1)
0.0000
35.85
0.0300
35.85
0.0300
83.32
0.0301
83.32
0.0301
y295.13
0.0305
y295.13
0.0305
253.00
0.0307
253.00
0.0307
37.83
0.0312
37.83
0.0312
135.80
0.0325
135.80
0.0325
671.95
0.0424
671.95
0.0424
529.31
Err
CarK
Err
27.31
27.31
3541.45
3541.45
1178.44
1178.44
1164.05
1164.05
578.41
578.41
275.41
275.41
24.98
24.98
115.01
0.96
0.96
5.22
5.22
2.60
2.60
2.37
2.37
1.33
1.33
1.21
1.21
2.66
2.66
2.59
0.02
0.02
4.93
4.93
1.52
1.52
1.61
1.61
0.78
0.78
0.41
0.41
0.07
0.07
0.16
Cum
39
Ar
Age
V28-82 98 cm - 2 (H2)
0.0000
34.00
0.0832
34.00
0.0832
339.96
0.0930
339.96
0.0930
462.41
0.1016
462.41
0.1016
647.69
0.1172
647.69
0.1172
724.06
0.1194
724.06
0.1194
956.20
0.1782
956.20
0.1782
1087.95
0.2357
1087.95
0.2357
1124.37
Err
CarK
Err
4.29
4.29
22.86
22.86
15.59
15.59
10.37
10.37
68.47
68.47
3.88
3.88
4.50
4.50
5.36
0.49
0.49
0.44
0.44
0.43
0.43
0.45
0.45
0.44
0.44
0.41
0.41
0.36
0.36
0.36
0.01
0.01
0.03
0.03
0.04
0.04
0.02
0.02
0.12
0.12
0.01
0.01
0.01
0.01
0.01
S.R. Hemming et al.r Chemical Geology 182 (2002) 583–603
598
0.0448
0.0448
0.0533
0.0533
0.0645
0.0645
0.0794
0.0794
0.0963
0.0963
0.1155
0.1155
0.1342
0.1342
0.1528
0.1528
0.1821
0.1821
0.2152
0.2152
0.2410
0.2410
0.2734
0.2734
0.3088
0.3088
0.3415
0.3415
0.6737
529.31
668.10
668.10
703.87
703.87
720.72
720.72
763.18
763.18
757.32
757.32
773.39
773.39
789.16
789.16
791.95
791.95
803.82
803.82
807.08
807.08
814.66
814.66
834.98
834.98
831.20
831.20
888.88
888.88
115.01
29.27
29.27
23.25
23.25
14.20
14.20
14.37
14.37
10.50
10.50
9.12
9.12
9.91
9.91
6.96
6.96
6.96
6.96
8.61
8.61
8.87
8.87
7.97
7.97
7.60
7.60
3.33
3.33
0.6737 922.33
2.90
0.94 0.01
2.90
63.10
63.10
0.94 0.01
1.38 0.11
1.38 0.11
1.29
0.9966 922.33
0.9966 785.79
1.0000 785.79
Total gas
846 " 2
age
Retention
871
age
2.59
2.57
2.57
2.18
2.18
2.11
2.11
2.09
2.09
2.10
2.10
2.04
2.04
2.11
2.11
2.17
2.17
1.92
1.92
1.62
1.62
1.51
1.51
1.40
1.40
1.24
1.24
1.14
1.14
0.16
0.07
0.07
0.06
0.06
0.06
0.06
0.04
0.04
0.06
0.06
0.05
0.05
0.05
0.05
0.03
0.03
0.02
0.02
0.02
0.02
0.03
0.03
0.03
0.03
0.02
0.02
0.01
0.01
0.2878
0.2878
0.3517
0.3517
0.4913
0.4913
0.5112
0.5112
0.5376
0.5376
0.6138
0.6138
0.6323
0.6323
0.6862
0.6862
0.7940
0.7940
0.8980
0.8980
0.9414
0.9414
0.9661
0.9661
0.9877
0.9877
1.0000
Total gas
age
Retention
age
1124.37
1139.25
1139.25
1153.98
1153.98
1162.37
1162.37
1164.57
1164.57
1159.22
1159.22
1161.93
1161.93
1171.15
1171.15
1187.40
1187.40
1203.37
1203.37
1211.01
1211.01
1202.07
1202.07
1141.64
1141.64
1044.22
1044.22
5.36
4.63
4.63
4.05
4.05
8.43
8.43
6.75
6.75
3.92
3.92
10.23
10.23
2.56
2.56
3.59
3.59
3.96
3.96
4.98
4.98
5.66
5.66
6.81
6.81
15.79
15.79
1059 " 3
0.36
0.34
0.34
0.34
0.34
0.34
0.34
0.36
0.36
0.37
0.37
0.33
0.33
0.37
0.37
0.40
0.40
0.45
0.45
0.51
0.51
0.63
0.63
0.70
0.70
0.96
0.96
0.01
0.01
0.01
0.01
0.01
0.02
0.02
0.02
0.02
0.01
0.01
0.02
0.02
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.02
0.02
0.02
0.02
0.03
0.03
0.41
1147
V28-82 98 cm 2–20 (H2)
V28-82 530 cm 2–20 (H11)
0.0000 y75.12
119.47 1.82 0.31
0.0000 4.71
0.0347 y75.12
119.47 1.82 0.31
0.0947 4.71
0.0347 y4345.48 541507.75 4.06 17.38
0.0947 92.19
0.0356 y4345.48 541507.75 4.06 17.38
0.1026 92.19
0.0356 y243.00
2162.09 12.71 9.10
0.1026 151.45
0.0371 y243.00
2162.09 12.71 9.10
0.1144 151.45
0.0371 539.30
2182.87 7.64 8.91
0.1144 236.05
4.03
4.03
32.53
32.53
16.59
16.59
10.42
0.18
0.18
0.15
0.15
0.14
0.14
0.13
0.00
0.00
0.03
0.03
0.03
0.03
0.01
S.R. Hemming et al.r Chemical Geology 182 (2002) 583–603
0.0383
0.0383
0.0490
0.0490
0.0674
0.0674
0.0931
0.0931
0.1236
0.1236
0.1611
0.1611
0.1937
0.1937
0.2165
0.2165
0.2581
0.2581
0.3182
0.3182
0.3715
0.3715
0.4206
0.4206
0.4607
0.4607
1.0000
Total gas
age
Retention
age
539.30 2182.87 7.64 8.91
652.30
215.41 3.09 1.13
652.30
215.41 3.09 1.13
796.51
115.36 2.30 0.76
796.51
115.36 2.30 0.76
906.90
71.94 1.72 0.51
906.90
71.94 1.72 0.51
911.37
48.99 1.06 0.42
911.37
48.99 1.06 0.42
908.07
54.31 0.86 0.38
908.07
54.31 0.86 0.38
911.96
60.04 1.08 0.37
911.96
60.04 1.08 0.37
876.81
82.82 0.82 0.44
876.81
82.82 0.82 0.44
951.49
51.64 0.92 0.39
951.49
51.64 0.92 0.39
937.77
35.01 0.80 0.26
937.77
35.01 0.80 0.26
992.08
42.57 0.66 0.21
992.08
42.57 0.66 0.21
1036.04
38.24 0.80 0.25
1036.04
38.24 0.80 0.25
966.59
53.93 0.96 0.24
966.59
53.93 0.96 0.24
1074.12
6.23 1.29 0.03
1074.12
6.23 1.29 0.03
983 " 5
0.1360
0.1360
0.1659
0.1659
0.2104
0.2104
0.2433
0.2433
0.2865
0.2865
0.3383
0.3383
0.3928
0.3928
0.4570
0.4570
0.5186
0.5186
0.5754
0.5754
0.6554
0.6554
0.6555
0.6555
0.6615
0.6615
0.8950
0.8950
0.9562
1.23
1017
Total gas
age
Retention
age
GGC29 108 cm - 2 (H2)
0.0000 41.15
0.0678 41.15
0.0678 182.00
0.0703 182.00
0.0703 245.65
0.0773 245.65
0.0773 335.83
3.49
3.49
49.38
49.38
22.36
22.36
18.48
0.36
0.36
0.37
0.37
0.34
0.34
0.34
0.01
0.01
0.08
0.08
0.03
0.03
0.03
599
236.05
10.42
0.13 0.01
303.76
8.52
0.12 0.01
303.76
8.52
0.12 0.01
369.71
5.18
0.11 0.01
369.71
5.18
0.11 0.01
392.98
8.00
0.11 0.01
392.98
8.00
0.11 0.01
416.74
5.36
0.11 0.01
416.74
5.36
0.11 0.01
439.38
4.02
0.10 0.01
439.38
4.02
0.10 0.01
463.31
4.52
0.10 0.01
463.31
4.52
0.10 0.01
481.73
3.77
0.09 0.01
481.73
3.77
0.09 0.01
496.14
3.62
0.09 0.01
496.14
3.62
0.09 0.01
504.52
3.92
0.08 0.01
504.52
3.92
0.08 0.01
512.00
2.65
0.09 0.00
512.00
2.65
0.09 0.00
y131.56 2045.15 y1.03 1.77
y131.56 2045.15 y1.03 1.77
492.46
36.63
0.07 0.03
492.46
36.63
0.07 0.03
542.23
24.84
0.10 0.01
542.23
24.84
0.10 0.01
513.63
3.23
0.10 0.01
513.63
3.23
0.10 0.01
0.9562 515.61
4.04
0.10 0.01
0.9966 515.61
0.9966 508.12
1.0000 508.12
433 " 5
4.04
43.28
43.28
0.10 0.01
0.04 0.12
0.04 0.12
0.11
474
V28-82 197 cm 2–20 (H4)
0.0000 11.23
0.0405 11.23
0.0405 y156.55
0.0416 y156.55
0.0416 391.25
0.0475 391.25
0.0475 773.18
28.78
28.78
535.95
535.95
106.15
106.15
13.19
0.46
0.46
0.90
0.90
0.44
0.44
0.49
0.08
0.08
3.62
3.62
0.56
0.56
0.12
S.R. Hemming et al.r Chemical Geology 182 (2002) 583–603
600
0.0844
0.0844
0.0942
0.0942
0.1059
0.1059
0.1276
0.1276
0.1540
0.1540
0.2027
0.2027
0.2574
0.2574
0.3153
0.3153
0.3644
0.3644
0.4100
0.4100
0.4496
0.4496
335.83
462.55
462.55
580.82
580.82
738.03
738.03
863.61
863.61
951.93
951.93
1006.61
1006.61
1032.95
1032.95
1043.76
1043.76
1053.47
1053.47
1059.13
1059.13
1062.22
18.48
11.09
11.09
9.53
9.53
5.36
5.36
4.79
4.79
2.45
2.45
2.28
2.28
4.48
4.48
3.91
3.91
3.10
3.10
3.42
3.42
3.36
0.34
0.34
0.34
0.31
0.31
0.32
0.32
0.30
0.30
0.28
0.28
0.27
0.27
0.28
0.28
0.28
0.28
0.27
0.27
0.28
0.28
0.29
0.03
0.02
0.02
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.4915
1062.22
3.36
0.29
0.01
0.4915
0.5325
0.5325
0.5711
0.5711
0.6161
0.6161
0.6583
0.6583
0.6976
0.6976
0.7380
0.7380
0.7790
0.7790
0.8188
0.8188
0.8520
0.8520
0.8809
0.8809
0.9124
0.9124
1066.23
1066.23
1067.13
1067.13
1067.11
1067.11
1077.74
1077.74
1078.11
1078.11
1075.39
1075.39
1069.79
1069.79
1073.77
1073.77
1077.32
1077.32
1078.97
1078.97
1080.41
1080.41
1081.97
4.11
4.11
4.59
4.59
4.02
4.02
5.23
5.23
3.51
3.51
3.11
3.11
5.90
5.90
4.48
4.48
5.71
5.71
4.81
4.81
4.70
4.70
5.84
0.30
0.30
0.29
0.29
0.30
0.30
0.31
0.31
0.31
0.31
0.32
0.32
0.34
0.34
0.33
0.33
0.35
0.35
0.38
0.38
0.39
0.39
0.42
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.0726
0.0726
0.1507
0.1507
0.2252
0.2252
0.3763
0.3763
0.4858
0.4858
0.6090
0.6090
0.6975
0.6975
0.7655
0.7655
0.8712
0.8712
0.9901
0.9901
1.0000
Total gas
age
Retention
age
773.18
924.92
924.92
973.73
973.73
1003.77
1003.77
1026.63
1026.63
1041.77
1041.77
1033.35
1033.35
1078.02
1078.02
1099.52
1099.52
1125.59
1125.59
1028.49
1028.49
99 " 4
1037
13.19
9.23
9.23
8.73
8.73
4.66
4.66
7.89
7.89
4.42
4.42
7.97
7.97
5.86
5.86
7.04
7.04
5.53
5.53
29.21
29.21
0.49
0.32
0.32
0.41
0.41
0.46
0.46
0.47
0.47
0.52
0.52
0.46
0.46
0.49
0.49
0.49
0.49
0.51
0.51
0.82
0.82
0.47
0.12
0.07
0.07
0.05
0.05
0.03
0.03
0.03
0.03
0.04
0.04
0.03
0.03
0.05
0.05
0.03
0.03
0.04
0.04
0.33
0.33
S.R. Hemming et al.r Chemical Geology 182 (2002) 583–603
0.9440
0.9440
0.9663
0.9663
0.9856
0.9856
1.0000
Total gas
age
Retention
gas
1081.97
1083.18
1083.18
1084.08
1084.08
1080.43
1080.43
970 " 4
5.84
5.92
5.92
6.29
6.29
11.96
11.96
0.42
0.44
0.44
0.51
0.51
0.58
0.58
0.32
9.25
9.25
7.62
7.62
1.94
1.94
5.22
5.22
4.23
4.23
5.85
5.85
3.15
3.15
6.11
6.11
6.18
6.18
6.08
6.08
3.70
3.70
8.73
8.73
8.31
8.31
15.35
15.35
0.21
0.21
0.16
0.16
0.19
0.19
0.19
0.19
0.22
0.22
0.23
0.23
0.28
0.28
0.27
0.27
0.31
0.31
0.35
0.35
0.41
0.41
0.48
0.48
0.55
0.55
0.54
0.54
601
0.01
0.01
0.01
0.01
0.01
0.02
0.02
1036
GGC40 155 cm 2–20 (H3)
0.0000 y1.35
0.0413 y1.35
0.0413 411.10
0.0816 411.10
0.0816 558.38
0.2625 558.38
0.2625 580.11
0.3137 580.11
0.3137 590.84
0.3984 590.84
0.3984 595.65
0.4687 595.65
0.4687 600.66
0.6016 600.66
0.6016 608.59
0.6638 608.59
0.6638 608.90
0.7294 608.90
0.7294 605.02
0.8063 605.02
0.8063 612.94
0.8887 612.94
0.8887 621.27
0.9298 621.27
0.9298 627.21
0.9700 627.21
0.9700 637.79
0.9887 637.79
0.9887 608.68
44.68 0.73
0.9957 608.68
0.9957 582.45
0.9981 582.45
44.68 0.73
147.62 0.74
147.62 0.74
JPC37 1280 cm 2–20 (H11)
0.04
0.0000 y24.40
0.04
0.1623 y24.40
0.02
0.1623 y499.19
0.02
0.1633 y499.19
0.01
0.1633 221.41
0.01
0.1793 221.41
0.03
0.1793 344.79
0.03
0.2214 344.79
0.02
0.2214 463.11
0.02
0.2489 463.11
0.02
0.2489 648.73
0.02
0.2885 648.73
0.01
0.2885 662.69
0.01
0.3441 622.69
0.04
0.3441 716.54
0.04
0.4283 716.54
0.02
0.4283 722.40
0.02
0.5197 722.40
0.03
0.5197 760.13
0.03
0.6165 760.13
0.02
0.6165 789.76
0.02
0.7626 789.76
0.05
0.7626 795.86
0.05
0.9982 795.86
0.04
0.9982 y977.63
0.04
1.0000 y977.63
0.07
0.07 Total gas
614 " 5
age
0.21 Retention
713
age
0.21
0.61
0.61
31.53
31.53
3393.15
3393.15
194.85
194.85
149.14
149.14
103.01
103.01
66.82
66.82
45.69
45.69
38.84
38.84
26.15
26.15
19.58
19.58
10.36
10.36
9.36
9.36
2690.41
2690.41
0.53 0.07
0.53 0.07
8.32 14.04
8.32 14.04
0.87 0.80
0.87 0.80
0.60 0.29
0.60 0.29
0.34 0.45
0.34 0.45
0.46 0.35
0.46 0.35
0.41 0.25
0.41 0.25
0.29 0.17
0.29 0.17
0.30 0.14
0.30 0.14
0.27 0.14
0.27 0.14
0.25 0.10
0.25 0.10
0.28 0.05
0.28 0.05
3.21 8.42
3.21 8.42
0.37
S.R. Hemming et al.r Chemical Geology 182 (2002) 583–603
602
0.9981
1.0000
Total gas
age
Retention
age
624.50
624.50
567 " 1
201.34
201.34
0.82
0.82
0.29
0.67
0.67
33.57
33.57
270.06
270.06
203.31
203.31
139.91
139.91
16627.60
16627.60
34.05
34.05
40.11
40.11
46.03
46.03
316.35
316.35
465.65
465.65
57
0.49
0.49
4.64
4.64
3.94
3.94
18.31
18.31
4389.45
4389.45
590
HU-009 660 cm - 2 (H2)
0.0000
14.69
0.8149
14.69
0.8149
736.62
0.8723
736.62
0.8723
1591.93
0.9229
1591.93
0.9229
1849.45
0.9995
1849.45
0.9995
6541.55
1.0000
6541.55
Total gas
419 " 23
age
Retention
1445
age
References
Andrews, J.T., Tedesco, K., 1992. Detrital carbonate-rich sediments, northwestern Labrador Sea: implications for ice-sheet
dynamics and iceberg rafting ŽHeinrich. events in the North
Atlantic. Geology 20, 1087–1090.
Andrews, J.T., Kirby, M., Jennings, A.E., Barber, D.C., 1998.
Late Quaternary stratigraphy, chronology, and depositional
processes on the slope of SE Baffin Island, detrital carbonate
and Heinrich events: implications for onshore glacial History.
Geophys. Phys. Quat. 52, 91–105.
Biscaye, P.E., 1965. Mineralogy and sedimentation of recent
deep-sea clay in the Atlantic Ocean and adjacent seas and
oceans. Geol. Soc. Am. Bull. 76, 803–832.
Bond, G.C., Lotti, R., 1995. Iceberg discharges into the North
Atlantic on millennial time scales during the last glaciation.
Science 267, 1005–1010.
Bond, G., Heinrich, H., Broecker, W., Labeyrie, L., McManus, J.,
Andrews, J., Huon, S., Jantschik, R., Clasen, S., Simet, C.,
Tedesco, K., Klas, M., Bonani, G., Ivy, S., 1992. Evidence for
massive discharges of icebergs into the North Atlantic Ocean
during the last glacial period. Nature 360, 245–249 Ž19
November 1992..
Broecker, W.S., 1994. Massive iceberg discharges as triggers for
global climate change. Nature 372, : 421–424 Ž1 December
1994..
Broecker, W.S., Bond, G.C., Klas, M., Clark, E., McManus, J.F.,
1992. Origin of the northern Atlantic’s Heinrich events. Clim.
Dyn. 6, 265–273.
Dong, H., Hall, C.M., Peacor, D.R., Halliday, A.N., 1995. Mechanisms of argon retention in clays revealed by laser 40Ar– 39Ar
Dating. Science 267, 355–359.
Dowdeswell, J.A., Maslin, M.A., Andrews, J.T., McCave, I.N.,
1995. Iceberg production, debris rafting, and the extent and
thickness of Heinrich layers ŽH-1, H-2. in North Atlantic
sediments. Geology 23 Ž4., 301–304.
Francois, R., Bacon, M., 1994. Heinrich events in the North
Atlantic: radiochemical evidence. Deep-Sea Res. 41 Ž2., 315–
334.
Grousset, F.R. et al., 1993. Patterns of ice-rafted detritus in the
glacial North Atlantic Ž408–558N.. Paleoceanography 8 Ž2.,
175–192.
Gwiazda, R.H., Hemming, S.R., Broecker, W.S., 1996a. Tracking
the sources of icebergs with lead isotopes: the provenance of
ice-rafted debris in Heinrich layer 2. Paleoceanography 11,
77–93.
Gwiazda, R.H., Hemming, S.R., Broecker, W.S., 1996b. Provenance of icebergs during Heinrich event 3 and the contrast to
their sources during other Heinrich episodes. Paleoceanography 11, 371–378.
Gwiazda, R.H., Hemming, S.R., Broecker, W.S., Onsttot, T.,
Mueller, C., 1996c. Evidence from 40Arr39Ar ages for a
Churchill Province source of ice-rafted amphiboles in Heinrich
layer 2. J. Glaciol. 42, 440–446.
Hall, C.M., Higueras, P.L., Kesler, S.E., Lunar, R., Dong, H.L.,
S.R. Hemming et al.r Chemical Geology 182 (2002) 583–603
Halliday, A.N., 1997. Dating of alteration episodes related to
mercury mineralization in the Almaden district, Spain. Earth
Planet. Sci. Lett. 148 Ž1–2., 287–298.
Heinrich, H., 1988. Origin and consequences of cyclic ice rafting
in the northeast Atlantic Ocean during the past 130,000 years.
Quat. Res. 29, 142–152.
Hemming, S.R., Rasbury, E.T., 2000. Pb isotope measurements of
sanidine monitor standards: implications for provenance analysis and tephrochronology. Chem. Geol. 165, 331–337.
Hemming, S.R., et al., 1998. Provenance of the Heinrich layers in
core V28-82, northeastern Atlantic: 40Ar– 39Ar ages of icerafted hornblende, Pb isotopes in feldspar grains, and Nd–Sr–
Pb isotopes in the fine sediment fraction. Earth Planet. Sci.
Lett. 164, 317–333.
Hemming, S.R., Bond, G.C., Broecker, W.S., Sharp, W.D., KlasMendelson, M., 2000a. Evidence from 40Arr39Ar Ages of
individual hornblende grains for varying Laurentide sources of
iceberg discharges 22,000 to 10,500 14 C yr BP. Quat. Res. 54,
372–383.
Hemming, S.R., Gwiazda, R.H., Andrews, J.T., Broecker, W.S.,
Jennings, A.E., Onstott, T.C., 2000b. 40Arr39Ar and Pb–Pb
study of individual hornblende and feldspar grains from southeastern Baffin Island glacial sediments: implications for the
provenance of the Heinrich layers. Can. J. Earth Sci. 37,
879–890.
Huon, S., Jantschik, R., 1993. Detrital silicates in northeast Atlantic deep-sea sediments during the late Quaternary: major
element REE and Rb–Sr isotopic data. Eclogae Geol. Helv.
86, 195–218.
Huon, S., Ruch, P., 1992. Mineralogical, K–Ar and 87 Srr86 Sr
isotope study of Holocene and last glacial sediments in a
deep-sea core from the northeast Atlantic Ocean. Mar. Geol.
107, 275–282.
Hurley, P.M., Heezen, B.C., Pinson, W.H., Fairbairn, H.W., 1963.
K-Ar age values in pelagic sediments of the North Atlantic.
Geochimica and Cosmochimica Acta 27, 393–399.
Jantschik, R., Huon, S., 1992. Detrital silicates in northeast Atlantic deep-sea sediments during the late Quaternary: mineralogical and K–Ar isotopic data. Eclogae Geol. Helv. 85,
195–212.
Jennings, A.E., Tedesco, K.A., Andrews, J.T., Kirby, M.E., 1996.
Shelf erosion and glacial ice proximity in the Labrador Sea
during and after Heinrich events ŽH-3 or 4 to H-0. as shown
by foraminifera. In: Andrews, J.T., Austin, W.E.N., Bergsten,
H., Jennings, A.E. ŽEds.., Late Quaternary Palaeoceanography
of the North Atlantic Margins. Geological Society Special
Publications. Geological Society of London, London, UK, pp.
29–49.
McDougall, I., Harrison, T.M., 1988. Geochronology and Thermochronology by the 40Arr39Ar Method. Oxford Univ. Press,
New York.
603
McLennan, S.M., Taylor, S.R., McCulloch, M.T., Maynard, J.B.,
1990. Geochemical and Nd–Sr isotopic composition of deepsea turbidites: crustal evolution and plate tectonic associations.
Geochim. Cosmochim. Acta 54, 2015–2050.
McLennan, S.M., Hemming, S.R., McDaniel, D.K., Hanson, G.N.,
1993. Geochemical approaches to sedimentation, provenance,
and tectonics. In: Johnsson, M.J., Basu, A. ŽEds.., Processes
Controlling the Composition of Clastic Sediments. Geological
Society of America Special Paper, vol. 284. Geological Society of America, Boulder, CO, pp. 21–40.
McManus, J.F., 1997. The last interglacial in the North Atlantic:
deep-sea records of climate variability and sediment flux.
Unpublished PhD dissertation, Columbia, New York, 122 pp.
McManus, J.F., et al., 1994. High-resolution climate records from
the North Atlantic during the last interglacial. Nature 371,
326–329.
McManus, J.F., Anderson, R.F., Broecker, W.S., Fleisher, M.Q.,
Higgins, S.M., 1998. Radiometrically determined sedimentary
fluxes in the sub-polar North Atlantic during the last 140,000
years. Earth Planet. Sci. Lett. 155, 29–43.
Odin, G.S., 1976. La glauconite GL-O, etalon
inter-laboratoires
´
pourl’analyse radiochronometrique.
Analusis 4, 287–291.
´
Revel, M., Sinko, J.A., Grousset, F.E., Biscaye, P.E., 1996. Sr and
Nd isotopes as tracers of North Atlantic lithic particles: paleoclimatic implications. Paleoceanography 11, 95–113.
Robinson, S.G., Maslin, M.A., McCave, N., 1995. Magnetic
susceptibility variations in upper Pleistocene deep-sea sediments of the NE Atlantic: implications for ice rafting and
palaeocirculation at the last glacial maximum. Paleoceanography 10, 221–250.
Ruddiman, W.F., 1977. Late Quaternary deposition of ice-rafted
sand in the subpolar North Atlantic Žlat 408 to 658N.. Geol.
Soc. Am. Bull. 88, 1813–1827.
Samson, S.D., Alexander Jr., E.C., 1987. Calibration of the interlaboratory 40Ar– 39Ar dating standard, MMhb-1. Chem. Geol.
ŽIsot. Geosci. Sect.. 66, 27–34.
Snoeckx, H., Grousset, F., Revel, M., Boelaert, A., 1999. European contribution of ice-rafted sand to Heinrich layers H3 and
H4. Mar. Geol. 158, 197–208.
Stoner, J.S., Channell, J.E.T., Hillaire-Marcel, C., 1996. The
magnetic signature of rapidly deposited detrital layers from the
deep Labrador Sea: relationship to North Atlantic Heinrich
layers. Paleoceanography 11, 309–325.
Taylor, S.R., McLennan, S.M., 1985. The Continental Crust: Its
Composition and Evolution. Blackwell, Oxford, 312 pp.
Thomson, J., Higgs, N.C., Clayton, T., 1995. A geochemical
criterion for the recognition of Heinrich events and estimation
of their depositional fluxes by the 230 Th excess profiling method.
Earth Planet. Sci. Lett. 135, 41–56.