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Journal ArticleDOI

A Pliocene-Pleistocene stack of 57 globally distributed benthic δ18O records

01 Mar 2005-Paleoceanography (John Wiley & Sons, Ltd)-Vol. 20, Iss: 1, pp 1-17
TL;DR: In this paper, a 53-Myr stack (LR04) of benthic δ18O records from 57 globally distributed sites aligned by an automated graphic correlation algorithm is presented.
Abstract: [1] We present a 53-Myr stack (the “LR04” stack) of benthic δ18O records from 57 globally distributed sites aligned by an automated graphic correlation algorithm This is the first benthic δ18O stack composed of more than three records to extend beyond 850 ka, and we use its improved signal quality to identify 24 new marine isotope stages in the early Pliocene We also present a new LR04 age model for the Pliocene-Pleistocene derived from tuning the δ18O stack to a simple ice model based on 21 June insolation at 65°N Stacked sedimentation rates provide additional age model constraints to prevent overtuning Despite a conservative tuning strategy, the LR04 benthic stack exhibits significant coherency with insolation in the obliquity band throughout the entire 53 Myr and in the precession band for more than half of the record The LR04 stack contains significantly more variance in benthic δ18O than previously published stacks of the late Pleistocene as the result of higher-resolution records, a better alignment technique, and a greater percentage of records from the Atlantic Finally, the relative phases of the stack's 41- and 23-kyr components suggest that the precession component of δ18O from 27–16 Ma is primarily a deep-water temperature signal and that the phase of δ18O precession response changed suddenly at 16 Ma

Summary (5 min read)

1. Introduction

  • [2] Alley [2003] recently called for a paleoceanographic ‘‘type section’’ to which all paleoceanographic measurements could be compared, in the same way that researchers have used data gathered by the Second Greenland Ice Sheet Project (GISP2) and Greenland Ice Core Project (GRIP) in studies of the last glacial cycle.
  • Here the authors present a new 5.3-Myr benthic d18O stack (the ‘‘LR04’’ stack), which they propose would make an excellent paleoceanographic type section for the Pliocene-Pleistocene. [3].
  • In the following section the authors provide background infor- mation on d18O and previously published stacks.
  • Section 5 describes the creation of the orbitally tuned LR04 age model, which is additionally constrained by two measures of global sedimentation rate.
  • Owing to the observed similarity of most marine d18O records and the global nature of the ice volume signal, d18O measurements also serve as the primary means for placing marine climate records on a common timescale.

3. Data

  • The stack presented in this paper contains benthic d18O records from 57 globally distributed sites.
  • These sites are well distributed in latitude, longitude, and depth in the Atlantic and Pacific and include two sites in the Indian Ocean (Figure 1).
  • Most of the d18O measurements in these records are from Uvigerina peregrina or Cibicidoides wuellerstorfi, with appropriate species offset corrections [Shackleton and Hall, 1984].
  • The included records vary widely in resolution and time span.
  • The aligned d18O records used in the stack are shown in Figure 2.

4.1. Graphic Correlation

  • Graphic correlation is the process of aligning paleoclimate signals based on the features within those signals [Prell et al., 1986], for example, by matching corresponding PA1003 LISIECKI AND RAYMO: PLIOCENE-PLEISTOCENE BENTHIC STACK 2 of 17 PA1003 peaks.
  • This allows the LSR at individual sites to vary a great deal and preserves as much coherent d18O variation as possible.
  • Graphic correlation actually corrects for any potential mixing lags between sites to produce an estimate of the d18O signal as if it had been recorded with the same phase everywhere. [12].
  • The authors also add white noise (s = 0.15%) to the d18O values of each alignment target before applying their graphic correlation and stacking algorithms.
  • Figure 3 shows test PA1003 LISIECKI AND RAYMO: PLIOCENE-PLEISTOCENE BENTHIC STACK 3 of 17 PA1003 PA1003 LISIECKI AND RAYMO: PLIOCENE-PLEISTOCENE.

4.2. Stacking

  • The alignment process for the stack’s construction is iterative.
  • The LR04 stack (Figure 4) is the average of all d18O records aligned to the transitional stack.
  • This final step improves alignment accuracy because the transitional stack resembles the average d18O curve more closely than any individual site does.
  • For any given time interval, the PA1003 LISIECKI AND RAYMO: PLIOCENE-PLEISTOCENE BENTHIC STACK 5 of 17 PA1003 concentration of data used in the LR04 stack is at least twice as high as in any previous stack or individual d18O record spanning that interval.
  • The authors do not adjust the mean or variance of the records, except to make species offset corrections.

5. Age Model

  • Because the LR04 stack is constructed by graphic correlation, its stratigraphic features are essentially independent of any timescale.
  • Below the authors describe the construction of an age model which takes advantage of the high signal-to-noise ratio of the stack and analysis of the sedimentation rates at 57 sites.
  • Almost any age model could be applied to the LR04 stack.
  • Constraining average LSR does not prevent individual sites from exhibiting highly variable sedimentation rates.
  • Therefore their tuning goals are to prevent rapid fluctuations in stacked LSR and to minimize its variance.

5.1. From 0 to 135 ka

  • While generally robust, their LSR tuning strategy is not effective for the most recent portion of the stack, where apparent sedimentation rates can be distorted by uncompacted sediments in the top few meters of a core [e.g., Skinner and McCave, 2003; Huybers and Wunsch, 2004].
  • Fortunately, reliable age estimates are available for this portion of the benthic d18O record.

5.2. Tuning Target

  • The authors tuning target is a simple nonlinear model of ice volume, y, which follows the equation dy dt ¼ 1 b Tm x yð Þ ð1Þ where the nonlinearity coefficient b is subtracted during ice growth and added during ice decay [Imbrie and Imbrie, 1980].
  • The authors allow the nonlinearity b and mean time constant Both increase linearly to 0.6 and 15 kyr, respectively, by 1.5 Ma and remain at those values to the present.
  • The authors assume that small ice sheets respond more quickly than the massive ones of the late Pleistocene and choose early Pliocene values of b and Tm to reflect the absence of large northern hemisphere ice sheets.
  • Different values of tidal dissipation in the orbital solution can shift the age model by 5 kyr at 5 Ma [Laskar et al., 1993].

5.3. Sedimentation Rate Constraints

  • To prevent tuning errors the authors monitor the implied average sedimentation rate of the stack throughout the tuning process.
  • The authors construct two different estimates of global sedimentation rates: an LSR stack, which averages the sites’ sedimentation rates, and a ‘‘normalized’’ LSR stack, which compensates for different mean sedimentation rates (MSR) across sites.
  • The LSR of each site is calculated by placing its d18O record on the stack’s timescale and calculating its sedimentation rate.
  • For the eleven sites with d18O records aligned to the stack in multiple segments, the LSR of each segment is normalized separately.
  • For the idealized case in which each LSR is generated by an independent, stationary random process, the normalized LSR stack for the ‘‘true’’ age model would converge to a constant value of unity.

5.4. Tuning

  • The LR04 stack is tuned to their simple ice model in a two-step process by the addition of age control points with an average spacing of 20 kyr.
  • Figure 5 shows the early Pleistocene portion of the stack and illustrates the balance achieved between strictly tuning the stack and minimizing the variance of normalized LSR. [26].
  • The authors ice-model tuning target, which inherently accentuates the effects of obliquity relative to precession due to its long time constant, produces a fairly good match to the d18O stack.
  • The normalized LSR stack generally varies by less than 10% from 4.3–0.1.
  • The stack is generally incoherent with respect to the eccentricity component of insolation, but coherence with the obliquity component is at the 95% confidence level for most of its length and is always above the 80% confidence level.

6. Results

  • The LR04 benthic stack reconstructs the average d18O signal of each marine isotope stage and substage within the Pliocene and Pleistocene.
  • The features of these stages are largely independent of the assigned age model because the stack is constructed by graphic correlation.
  • Overall, the mean standard error of the stack is 0.06%, and only 2% of the data points have errors greater than 0.1%.
  • The authors define termination magnitude as the difference between the maximum d18O value of the preceding glacial and the minimum of the following interglacial.
  • In comparison, stages 9 and 5 remained below 3.6% for 13 and 12 kyr, respectively, and the Holocene interglacial has lasted 11 kyr so far.

6.2. MIS Identification

  • Below MIS 104 the authors adopt the stage identification scheme of Shackleton et al. [1995a] (hereinafter referred to as SHP95).
  • Co2 is the uppermost glacial excursion within the Cochiti subchron.
  • Additionally, the flexibility of the SHP95 numbering scheme minimizes the number of renamed stages because new stages in one magnetic subchron will not alter MIS names in other subchrons. [33].
  • Some of the smaller Pliocene stages from Sites 607 and 846 become better defined in the stack (e.g., MIS 77 and 83) while others almost disappear because they are small or absent in most d18O records.
  • Below the Mammoth subchron, the LR04 stack reduces noise in some portions of the record to the extent that new isotopic stages can be resolved.

6.3. Paleomagnetic Polarity Reversals

  • Errors in these estimates can arise from both age model construction and reversal identification within sediment cores.
  • Because fewer records are available, below the Matuyama the authors also use reversal identifications from Leg 138, correlated to Site 846 [Shackleton et al., 1995b].
  • Ages for the Kaena and Mammoth subchrons are averages from Sites 607 and 846 while the Gauss/Gilbert boundary and the top of the Cochiti subchron are dated from Sites 659 and 846.
  • All other polarity reversals are based solely on Site 846.
  • Given the error involved in reversal identification, the authors observe that all four age models are quite similar.

6.4. Comparison to S95 Composite

  • With a few exceptions, the LR04 global PliocenePleistocene stack is similar to the S95 composite, which contains unstacked, high-resolution benthic records from sites V19-30, ODP 677, and ODP 846.
  • Additionally, the higher signal-to-noise ratio of the LR04 stack allows us to resolve new isotopic stages in the early Pliocene, as detailed above.
  • On the basis of the average sedimentation rates of over 30 marine sediment records, the authors propose that the MIS 13 and 14 age estimates of the S95 composite and EDC2 are in error.
  • Because the EDC2 timescale is otherwise in close agreement with ours, the misalignment of stages 13 and 14 may indicate a stratigraphic disturbance in the ice core at the top of MIS 15. [38].
  • Ma the S95 composite is on average 7 kyr older than the LR04 age model, primarily due to the different phase lag assumptions used.

6.5. Comparison to Other Stacks

  • The LR04 benthic stack is generally similar to previously published stacks with respect to MIS features and timescale but differs somewhat in its variance and spectral density.
  • Indeed, the tropical stack has only 25% as much precessional variance as the LR04 stack (Table 5).
  • These age differences all fall within the uncertainty estimates published for the HW04 age model.
  • The leading EOF of their best benthic and planktonic records contains proportionally more variance than the LR04 stack in the 100-kyr band but less in the 41- and 23-kyr bands.
  • The spectral power and substage features of their EOF are also affected by the use of only 17 age control points to align the records.

7.1. Age Model Uncertainty

  • The greatest potential source of error in the LR04 age model is uncertainty in the orbital solution, which may be as high as 25 kyr in the early Pliocene.
  • Relative to the orbital solution, their tuning errors should be no more than a few thousand years because the authors tune a low-noise signal and avoid spikes in the stack’s average sedimentation rate.
  • Ma the LR04 age model is also subject to increased uncertainty because the stack contains fewer records and inherently has fewer tuning and alignment constraints. [44].
  • In the more recent part of the age model, most of the uncertainty derives from their sedimentation rate constraint and the assumed response times of the ice sheets.
  • The LSR tuning technique may neglect some real but highfrequency changes in global LSR, such as those resulting from global climate reorganizations over glacial-interglacial cycles.

7.2. Precession Phase and Deep-Water Temperature

  • As explained in section 5.4, the time constant of their ice model is the primary factor controlling the stack’s phase relative to obliquity.
  • Indeed, Figure 7 shows that the stack’s lag in precession actually decreases at 2.7.
  • This small lag suggests that a PA1003 LISIECKI AND RAYMO: PLIOCENE-PLEISTOCENE BENTHIC STACK 14 of 17 PA1003 significant portion of the precession component of late Pliocene d18O is a deep-water temperature signal which leads ice volume.
  • Ma the precession lag suddenly jumps by 45 relative to that of obliquity, putting it in close agreement with their ice model for the rest of the Pleistocene. [46].
  • If the ice model’s mean time constant Tm is held constant at 15 kyr for the last 3 Myr, a 30 change in precession lag still occurs at 1.6 Ma.

8. Conclusions

  • The global Pliocene-Pleistocene stack presented in this paper contains benthic d18O data from 57 globally distributed sites and has an average standard error of only 0.06%.
  • The LR04 stack and the LR04 agemodel provide the paleoclimate community with two stratigraphic tools, which can be applied to a wide variety of Pliocene-Pleistocene studies.
  • The authors define 24 new isotopic stages from 5.0– 3.4 Ma and identify several likely errors in the S95 composite.
  • Tm mean time constant of ice, kyr; s standard deviation. [51].
  • L. Lisiecki also thanks T. Herbert, W. Prell, and S. Clemens for their guidance throughout this project.

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Content maybe subject to copyright    Report

A Pliocene-Pleistocene stack of 57 globally distributed
benthic D
18
O records
Lorraine E. Lisiecki
Department of Geological Sciences, Brown University, Providence, Rhode Island, USA
Maureen E. Raymo
Department of Earth Sciences, Boston University, Boston, Massachusetts, USA
Received 8 July 2004; revised 9 November 2004; accepted 23 November 2004; published 18 January 2005.
[1] We present a 5.3-Myr stack (the ‘LR04’ stack) of benthic d
18
O records from 57 globally distributed sites
aligned by an automated graphic correlation algorithm. This is the first benthic d
18
O stack composed of more
than three records to extend beyond 850 ka, and we use its improved signal quality to identify 24 new marine
isotope stages in the early Pliocene. We also present a new LR04 age model for the Pliocene-Pleistocene derived
from tuning the d
18
O stack to a simple ice model based on 21 June insolation at 65N. Stacked sedimentation
rates provide additional age model constraints to prevent overtuning. Despite a conservative tuning strategy, the
LR04 benthic stack exhibits significant coherency with insolation in the obliquity band throughout the entire
5.3 Myr and in the precession band for more than half of the record. The LR04 stack contains significantly
more variance in benthic d
18
O than previously published stacks of the late Pleistocene as the result of higher-
resolution records, a better alignment technique, and a greater percentage of records from the Atlantic. Finally,
the relative phases of the stack’s 41- and 23-kyr components suggest that the precession component of d
18
O
from 2.71.6 Ma is primarily a deep-water temperature signal and that the phase of d
18
O precession response
changed suddenly at 1.6 Ma.
Citation: Lisiecki, L. E., and M. E. Raymo (2005), A Pliocene-Pleistocene stack of 57 globally distributed benthic d
18
O records,
Paleoceanography, 20, PA1003, doi:10.1029/2004PA001071.
1. Introduction
[2] Alley [2003] recently called for a paleoceano-
graphic ‘type section’ to which all paleoceanographic
measurements could be compared, in the same way that
researchers have used data gathered by the Second
Greenland Ice Sheet Project (GISP2) and Greenland Ice
Core Project (GRIP) in studies of the last glacial cycle.
A type section which provides a common timescale and
reference of comparison for all paleoceanographic
records would improve communication within the commu-
nity and elucidate subtle differences among the ever-
growing number of paleoceanographic records. Here we
present a new 5.3-Myr benthic d
18
O stack (the ‘LR04’
stack), which we propose would make an excellent paleo-
ceanographic type section for the Pliocene-Pleistocene.
[
3] Alley [2003] describes the ideal type section as high in
resolution, multiply replicated by different laboratories,
containing multiple paleoclimate proxies, and spanning as
much time as possible. The LR04 stack contains over
38,000 individual d
18
O measurements from 57 sites, sam-
pled at many different laboratories. Because this stack
incorporates infor mation from so many sites, it has a
higher signal-to-noise ratio than any previous d
18
O record
and more accurately reflects changes in global cl imate.
The stack’s resolution of orbital-scale (23-kyr) features in
the Pleistocene is comparable to that of millennial-scale
(1.5-kyr) features in the GISP2 d
18
O record [Grootes et al.,
1993], with 10 20 samples per cycle. The stack spans the
entire Pliocene-Pleistocene with error bars averaging only
0.1%. We also use the LR04 stack to develop a conser-
vatively tuned d
18
O timescale, which minimizes deviations
in globally averaged sedimentation rates. Although the
LR04 stack contains only one paleoceanographic param-
eter, any paleoclimate proxy taken from a marine core
with reliable d
18
O data can easily be aligned to the LR04
stack through the use of automated graphic correlation
software [e.g., Lisiecki and Lisiecki, 2002]. The LR04 stack
and supplemental results are archived at the National Geo-
physical Data Center (http://www.ngdc.noaa.gov/paleo/
paleocean.html).
[
4] In the following section we provide background infor-
mation on d
18
O and previously published stacks. Section 3
describes the d
18
O data used in the LR04 stack. Section 4
contains a detailed description of the stack’s construction
and demonstrates the effectiveness of our graphic correlation
and stacking techniques in reducing the noise level of
d
18
O-like signals. Section 5 describes the creation of the
orbitally tuned LR04 age model, which is additionally con-
strained by two measures of global sedimentation rate. In
section 6 we present specific d
18
O estimates with error bars
and define 24 new marine isotope stages (MIS) in the early
Pliocene. We als o compare the LR04 stack to four previously
PALEOCEANOGRAPHY, VOL. 20, PA1003, doi:10.1029/2004PA001071, 2005
Copyright 2005 by the American Geophysical Union.
0883-8305/05/2004PA001071
PA1003 1of17
Correction published 24 May 2005

published d
18
O stacks. Finally, in section 7 we discuss the
uncertainty in the LR04 age model and interpret changes in
the phase of benthic d
18
O relative to precession.
2. Stacks of D
18
O
[5] Time series of the d
18
O of foraminiferal calcite tests
provide an important record of climate change. Foraminif-
eral d
18
O is a function of the temperature and d
18
Oofthe
water in which it forms, and the d
18
O of seawater is a
function of glo bal ice volume and water salinity. (The
scaling between d
18
O and these two factors can vary with
patterns of sea ice formation, evaporation, and precipita-
tion.) Owing to the observed similarity of most marine d
18
O
records and the global nature of the ice volume signal, d
18
O
measurements also serve as the primary means for placing
marine climate records on a common timescale. Stacks,
which are averages of d
18
O records from multiple sites,
improve the signal-to-noise ratio of the climate signal and
make useful alignment targets and references for compari-
son. Benthic d
18
O records should produce a better stack than
planktonic records because the deep ocean is more uniform
in temperature and salinity than surface water. Less local
and regional climatic variability improves the accuracy of
alignment and produces a better estimate of average d
18
O
change. While a stack alone cannot address the relative
contributions of ice volume and temperature to the benthic
d
18
O signal, a good stack does provide an accurate estimate
of how much total change must be explained.
[
6] Table 1 contains a summary of some notable d
18
O
stacks. The most widely used stack is the one constructed by
SPECMAP [Imbrie et al., 1984] (hereinafter referred to as
SPECMAP), which is composed of five planktonic records
and extends back to 750 kyr ago (ka). While studies
support the basic structure of this stack and its timescale
back to 625 ka [e.g., Shackleton et al., 1990; Pisias et al.,
1990; Raymo, 1997; Huybers and Wunsch, 2004], many
longer and higher resolution d
18
O records are now available.
Another important d
18
O r eference signal is the 6-Myr
composite benthic d
18
O sequence of Shackleton [1995]
(hereinafter referred to as S95), which was constructed by
placing high-resolution d
18
O records from three different
sites (V19-30, ODP 677, and ODP 846) in series. Karner et
al. [2002] construct an 860-kyr ‘minimally tuned’ benthic
stack by aligning the 41-kyr components of 13 benthic
records. However, they present a second, tropical stack
containing only six of these records because they find their
alignment technique to be inadequate for cores with highly
variable sedimentation rates. Last, Huybers and Wunsch
[2004] recently published a depth-derived age model for the
last 780 kyr (hereinafter referred to as HW04), accompanied
by the leading empirical orthogonal function (EOF1) of five
planktonic and five benthic d
18
O records. Their age model
assumes that the average sedimentation rate across 21 cores
was constant between 17 isotopic events, after applying a
correction for the effects of down-core compaction. Many
other age models have been created by tuning data from
individual sites [e.g., Tiedemann et al., 1994; Tiedemann
and Franz, 1997]; the proliferation of such age models can
greatly complicate the comparison of data from different
sites.
[
7] The LR04 stack contains 57 benthic records aligned
using a graphic correlation technique [Lisiecki and Lisiecki,
2002] and is the first benthic d
18
O stack containing more
than three records to extend beyond 850 ka. In section 6, we
compare the LR04 stack with the S95 composite, the
SPECMAP stack, the minimally tuned tropical stack of
Karner et al. [2002], and the depth-derived age model of
HW04. We discuss several isotope stages for which the
S95 composite is not representative of global mean d
18
O
as well as two likely errors in the S95 age model.
3. Data
[8] The stack presented in this paper contains benthic d
18
O
records from 57 globally distributed sites. These sites are
well distributed in latitude, longitude, and depth in the
Atlantic and Pacific and include two sites in the Indian
Ocean (Figure 1). Most of the d
18
O measurements in these
records are from Uvigerina peregrina or Cibicidoides wuel-
lerstorfi, with appropriate species offset corrections
[Shackleton and Hall, 1984]. The included records vary
widely in resolution and time span. The only benthic d
18
O
records purposefully excluded from the LR04 stack ar e
those with sample spacings greater than 12 kyr, a resolution
too low for accurate alignment. Our stacking technique,
described below, is robust to the inclusion of records of
varying quality because sites with higher resolution are more
heavily weighted in the averaging process. The aligned d
18
O
records used in the stack are shown in Figure 2. The stack
contains 47 records back to 0.4 Ma, 25 records from 1
3 Ma, at least 12 records back to 4.9 Ma, and 5 records
from 5 5.33 Ma. No one record represents more than 30%
of the data in a 10-kyr interval except before 5 Ma, when
Site 846 [Shackleton et al., 1995a] provides approximately
40% of the data. In total, the LR04 stack incorporates
38,229 individual d
18
O measurements.
4. Stack Construction
4.1. Graphic Correlation
[
9] Graphic correlation is the process of aligning paleo-
climate signals based on the features within those signals
[Prell et al., 1986], for example, by matching corresponding
Table 1. Notable d
18
O Stacks
Stack
Component
d
18
O Records
a
Approximate
Length
SPECMAP
b
5 p. 750 kyr
Pisias et al. [1984] 5 b. 300 kyr
c
Prell et al. [1986] 11 p., 2 b. 750 kyr
c
Williams et al. [1988] 3 p., 1 b. 1.9 Myr
Raymo et al. [1990] 3 b. 2.5 Myr
Bassinot et al. [1994] 2 p. 900 kyr
S95 Composite
d
3 b. (in series) 6 Myr
Karner et al. [2002] 6 13 b. 860 kyr
HW04
e
5 p., 5 b. (EOF) 780 kyr
LR04 (this study) 57 b. 5.3 Myr
a
Planktonic (p.) or benthic (b.).
b
From Imbrie et al. [1984].
c
No timescale assigned to stack.
d
From Shackleton [1995].
e
From Huybers and Wunsch [2004].
PA1003 LISIECKI AND RAYMO: PLIOCENE-PLEISTOCENE BENTHIC STACK
2of17
PA1003

peaks. Graphic correlation inherently requires some judg-
ment to determine which features correspond to one another
and to distinguish noise from isotopic features. Automated
correlation algorithms provide the most objective correla-
tion techniques because alignment criteria are explicit and
applied consistently. However, each alignment must also be
evaluated by eye because stratigraphic disturbances result-
ing from hiatuses, coring gaps, and duplicated sections can
produce errors in the automated correlation.
[
10] We align 57 benthic d
18
O records using an automated
graphic correlation program [Lisiecki and Lisiecki, 2002],
which considers all possible alignments to find the best
global fit and penalizes alignments based on extreme
sedimentation rates and sudden sedimentation rate changes.
Alignments are performed using normalized d
18
O r ecords to
maximize the algorithm’s accuracy. Each alignment i s
evaluated by eye and adjusted, if necessary, by changing
the sedimentation rate penalties or adding tie points until a
good alignment is achieved which agrees reasonably well
with previously published age estimates (e.g., those derived
from paleomagnetic reversals or biostratigraphic data). In
general, we keep sedimentation rate penalties small
because little is known about how linear sedimentation rates
(LSR) vary with time. This allows the LSR at individual
sites to vary a great deal and preserves as much coherent
d
18
O variation as possible. With our alignments and age
model, the average standard deviation (s) in a site’s LSR is
1.8 cm/kyr. As a percentage of each site’s mean LSR, s
averages 41% and ranges from 24% at Site GeoB1041 to
164% at ODP Site 927 from 5.02.6 Ma.
[
11] Graphic correlation allows the stack’s construction to
be largely independent of its assigned timescale and, con-
sequently, any specific forcing model for d
18
O. However,
stacking with graphic correlation does involve two assump-
tions: that each site records the same global d
18
O signal with
little phase difference and that the alignment procedure is
not overly sensitive to noise. In support of the first assump-
tion, each site does appear to record the same d
18
O signal;
the average correlation between the LR04 stack and indi-
vidual records (after alignment) is 0.88. Also, phase differ-
ences in d
18
O between sites should be minimal because the
average mixing time of the deep ocean is only 1 kyr.
Glacial ventilation rates are uncertain, but benthic-plank-
tonic age differences at the last glacial maximum yield
deep-water age estimates of 1.1 kyr in the deep Atlantic
[Keigwin and Schlegel, 2002] and 2 kyr in the deep Pacific
[Broecker et al., 2004]. Graphic correlation actually corrects
for any potential mixing lags between sites to produce an
estimate of the d
18
O signal as if it had been recorded with
the same phase everywhere.
[
12] The assumption that alignments are insensitive to
noise is a concern because sedimentation rates at individual
sites are only loosely constrained in order to maximize the
amplitude of isotopic features. Therefore we perform a
series of simple experiments to test t he ability of our
alignment technique to reduce noise without artificially
increasing signal amplitude. In the experiments, we con-
struct test stacks from twenty noisy copies of a single
isotope record. The noisy copies are created by the
addition of white noise with standard deviations of 2 kyr
and 0.2% to the ages and d
18
O values of the initial signal.
We also add white noise (s = 0.15%)tothed
18
O values
of each alignment target before applying our graphic
correlation and stacking algorithms. Figure 3 shows test
Figure 1. Location of the cores used in this study. Benthic d
18
O data are taken from Deep-Sea Drilling
Project (DSDP) and Ocean Drilling Program (ODP) sites (crosses), GeoB sites (diamonds), and others
(circles).
PA1003 LISIECKI AND RAYMO: PLIOCENE-PLEISTOCENE BENTHIC STACK
3of17
PA1003

Figure 2. Graphically aligned benthic d
18
O data, plotted with their original variance but offset
vertically. Data are from Sites 502 [deMenocal et al., 1992], 552 [Shackleton and Hall, 1984], 607
[Ruddiman et al., 1989; Raymo et al., 1989; Raymo et al., 1992; this study], 610 [Raymo et al., 1992],
658 [Tiedemann, 1991], 659 [Tiedemann et al., 1994], 662 (this study), 664 [Raymo et al., 1997], 665
[Curry and Miller, 1989], 677 [Shackleton et al., 1990], 704 [Hodell and Venz, 1992], 722 [Clemens et
al., 1996], 758 [Chen et al., 1995], 806 [Berger et al., 1993], 846 [Mixetal., 1995a; Shackleton et al.,
1995a], 849 [Mix et al., 1995b], 925 [Bickert et al., 1997; Billups et al., 1998; Franz, 1999], 927 [Bickert
et al., 1997; Franz, 1999], 928 [Franz, 1999], 929 [Bickert et al., 1997; Billups et al., 1998; Franz,
1999], 980 [Oppo et al., 1998; McManus et al., 1999; Flower et al., 2000], 981 [Mc Intyre et al., 1999;
Raymo et al., 2004], 982 [Venz et al., 1999; Venz and Hodell, 2002; this study], 983 [Mc Intyre et al.,
1999; Raymo et al., 2004], 984 [Raymo et al., 2004], 999 [Haug and Tiedemann, 1998], 1012 and 1020
[Herbert et al., 2001; Z. Liu, personal communication, 2002], 1085 (D. Andreasen, personal
communication, 2002), 1087 [Pierre et al., 2001], 1088 [Hodell et al., 2003], 1089 [Hodell et al.,
2001], 1090 [Venz and Hodell, 2002], 1092 [Andersson et al., 2002], 1123 [Hall et al., 2001; Harris,
2002], 1143 [Tian et al., 2002], 1146 (S. Clemens, personal communication, 2002), 1148 [Jian et
al., 2003], GeoB 1032, 1041, 1101 [Bickert and Wefer, 1996], GeoB 1113 [Sarnthein et al., 1994], GeoB
1117, 1211, 1214 [Bickert and Wefer, 1996], GeoB 1312 [Hale and Pflaumann, 1999], GeoB 1505 [Zabel
et al., 1999], MD95-2042 [Shackleton et al., 2000], PC72 [Murray et al., 2000], RC13-110 [Mix et al.,
1991; Imbrie et al., 1992], RC13-229 [Oppo et al., 1990], V19-28 [Ninkovitch and Shackleton, 1975],
V19-30 [Shackleton and Pisias, 1985], V21-146 [Hovan et al., 1991].
PA1003 LISIECKI AND RAYMO: PLIOCENE-PLEISTOCENE BENTHIC STACK
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PA1003

stacks generated from initial signals of Pleistocene (s =
0.43%) and Pliocene (s = 0.21%) d
18
O data. In 400
replications, the stacks’ error relative to the initial isotope
signal (for either time period) has a standard deviation of
0.09 ± 0.01%, less than the noise in the alignment target
and half that of the noisy records used to construct the
stack. Experiments performed with red noise produce
similar results. Stacking records of varying resolution
(while holding the total number of data points constant)
tends to reduce stack error by improving the alignment
accuracy of high resolution records. In conclusion, the
extraordinary similarity between the test stacks and the
initial isotope signal s demonstrates the ability of our
alignment and stacking technique to increase the signal-
to-noise ratio of Pleistocene and Pliocene d
18
O records.
4.2. Stacking
[
13] The alignment proce ss for the stack’s construction is
iterative. Our initial alignment targets are high-resolution
segments of seven d
18
O records: GeoB1041 from 0
0.15 Ma, ODP Site 1012 from 00.6 Ma, ODP Site 927
from 0 1.4 Ma, ODP Site 677 from 02.0 Ma, ODP Site
849 from 1.7 3.6 Ma, ODP Site 846 from 2.7 5.3 Ma,
and ODP Site 999 from 3.3 5.3 Ma. Each d
18
O record is
first aligned to these targets in the depth domain to create
seven short stacks. In the intervals where these stacks
overlap, we observe that the features of the stacks are
largely independent of which site serves as the alignment
target.
[
14] The seven stacks are assigned timescales taken from
the S95 composite and spliced together to form a transi-
tional stack spanning the entire 5.3-Myr interval. In con-
structing the transitional stack, we select portions of the
short stacks which are most representative of the component
records and which best resolve substage features. These
comparisons help prevent hiatuses, sediment disturbances,
and splicing errors within an alignment target from affecting
the final stack. Where possible, we also avoid using the first
and last 5% of each stack due to added uncertainty in the
graphic correlation [Lisiecki a nd Lisiecki, 2002]. After
creating the transitional stack, we make a few adjustments
to its age model to eliminate large deviations in the sites’
sedimentation rates and perform a final set of alignments
using the transitional stack as the alignment target.
[
15] The LR04 stack (Figure 4) is the average of all d
18
O
records aligned to the transitional stack. This final step
improves alignment accuracy because the transitional stack
resembles the average d
18
O curve more closely than any
individual site does. Also, because the transitional stack
spans the entire 5.3 Myr, most of our records could be
aligned to it in one piece, reducing the potential for errors
where the shorter stacks join together. The d
18
O records
from eleven sites are aligned to the stack in multiple pieces
because they are greater than 3 Myr in length or contain
large gaps. In Figure 4 we show the final LR04 stack
assigned to the LR04 age model, described in section 5.
[
16] Our stacking technique is similar to one used by
Pisias et al. [1984]. The stack’s time domain is divided into
small, equally spaced intervals (Table 2), and an average is
taken of all d
18
O measurements lying within each time
interval. Therefore each point in the stack is the average of
all of the data which fall in a particular time interval. Unlike
the averaging of evenly interpolated records, this technique
weights high-resolution records more heavily and prevents
interpolation across gaps or hiatuses from affecting the
stack. The final LR04 stack is composed of four sections
of different resolution due to the decreasing number of
records available in the more distant past. Table 2 provides
the interval size (equivalent to stack resolution) and data
statistics for each section. For any given time interval, the
Figure 3. Test of alignment and stacking technique for (a) Pleistocene and (b) Pliocene d
18
O. (top) One
of 20 artificial noisy d
18
O records used to produce (middle) a test stack, which is compared to (bottom)
the initial d
18
O signal. (See text for discussion.)
PA1003 LISIECKI AND RAYMO: PLIOCENE-PLEISTOCENE BENTHIC STACK
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PA1003

Citations
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Journal ArticleDOI
07 Aug 2009-Science
TL;DR: The responses of the Northern and Southern Hemispheres differed significantly, which reveals how the evolution of specific ice sheets affected sea level and provides insight into how insolation controlled the deglaciation.
Abstract: We used 5704 14C, 10Be, and 3He ages that span the interval from 10,000 to 50,000 years ago (10 to 50 ka) to constrain the timing of the Last Glacial Maximum (LGM) in terms of global ice-sheet and mountain-glacier extent. Growth of the ice sheets to their maximum positions occurred between 33.0 and 26.5 ka in response to climate forcing from decreases in northern summer insolation, tropical Pacific sea surface temperatures, and atmospheric CO2. Nearly all ice sheets were at their LGM positions from 26.5 ka to 19 to 20 ka, corresponding to minima in these forcings. The onset of Northern Hemisphere deglaciation 19 to 20 ka was induced by an increase in northern summer insolation, providing the source for an abrupt rise in sea level. The onset of deglaciation of the West Antarctic Ice Sheet occurred between 14 and 15 ka, consistent with evidence that this was the primary source for an abrupt rise in sea level ~14.5 ka.

2,691 citations

Journal ArticleDOI
15 May 2008-Nature
TL;DR: It is found that atmospheric carbon dioxide is strongly correlated with Antarctic temperature throughout eight glacial cycles but with significantly lower concentrations between 650,000 and 750,000 yr before present, which extends the pre-industrial range of carbon dioxide concentrations during the late Quaternary by about 10 p.p.m.v.
Abstract: Changes in past atmospheric carbon dioxide concentrations can be determined by measuring the composition of air trapped in ice cores from Antarctica. So far, the Antarctic Vostok and EPICA Dome C ice cores have provided a composite record of atmospheric carbon dioxide levels over the past 650,000 years. Here we present results of the lowest 200 m of the Dome C ice core, extending the record of atmospheric carbon dioxide concentration by two complete glacial cycles to 800,000 yr before present. From previously published data and the present work, we find that atmospheric carbon dioxide is strongly correlated with Antarctic temperature throughout eight glacial cycles but with significantly lower concentrations between 650,000 and 750,000 yr before present. Carbon dioxide levels are below 180 parts per million by volume (p.p.m.v.) for a period of 3,000 yr during Marine Isotope Stage 16, possibly reflecting more pronounced oceanic carbon storage. We report the lowest carbon dioxide concentration measured in an ice core, which extends the pre-industrial range of carbon dioxide concentrations during the late Quaternary by about 10 p.p.m.v. to 172-300 p.p.m.v.

1,977 citations

Journal ArticleDOI
10 Aug 2007-Science
TL;DR: It is suggested that the interplay between obliquity and precession accounts for the variable intensity of interglacial periods in ice core records.
Abstract: A high-resolution deuterium profile is now available along the entire European Project for Ice Coring in Antarctica Dome C ice core, extending this climate record back to marine isotope stage 20.2, ∼800,000 years ago. Experiments performed with an atmospheric general circulation model including water isotopes support its temperature interpretation. We assessed the general correspondence between Dansgaard-Oeschger events and their smoothed Antarctic counterparts for this Dome C record, which reveals the presence of such features with similar amplitudes during previous glacial periods. We suggest that the interplay between obliquity and precession accounts for the variable intensity of interglacial periods in ice core records.

1,723 citations

01 Jan 2006
TL;DR: A high-resolution deuterium profile is available along the entire European Project for Ice Coring in Antarctica Dome C ice core, extending this climate record back to marine isotope stage 20.2, ∼800,000 years ago.
Abstract: A high-resolution deuterium profile is now available along the entire European Project for Ice Coring in Antarctica Dome C ice core, extending this climate record back to marine isotope stage 20.2, ∼800,000 years ago. Experiments performed with an atmospheric general circulation model including water isotopes support its temperature interpretation. We assessed the general correspondence between Dansgaard-Oeschger events and their smoothed Antarctic counterparts for this Dome C record, which reveals the presence of such features with similar amplitudes during previous glacial periods. We suggest that the interplay between obliquity and precession accounts for the variable intensity of interglacial periods in ice core records.

1,566 citations

Journal ArticleDOI
TL;DR: From ∼1,000 observations of sea level, allowing for isostatic and tectonic contributions, this work quantified the rise and fall in global ocean and ice volumes for the past 35,000 years and provides new constraints on the fluctuation of ice volume in this interval.
Abstract: The major cause of sea-level change during ice ages is the exchange of water between ice and ocean and the planet's dynamic response to the changing surface load. Inversion of ∼1,000 observations for the past 35,000 y from localities far from former ice margins has provided new constraints on the fluctuation of ice volume in this interval. Key results are: (i) a rapid final fall in global sea level of ∼40 m in <2,000 y at the onset of the glacial maximum ∼30,000 y before present (30 ka BP); (ii) a slow fall to -134 m from 29 to 21 ka BP with a maximum grounded ice volume of ∼52 × 10(6) km(3) greater than today; (iii) after an initial short duration rapid rise and a short interval of near-constant sea level, the main phase of deglaciation occurred from ∼16.5 ka BP to ∼8.2 ka BP at an average rate of rise of 12 m⋅ka(-1) punctuated by periods of greater, particularly at 14.5-14.0 ka BP at ≥40 mm⋅y(-1) (MWP-1A), and lesser, from 12.5 to 11.5 ka BP (Younger Dryas), rates; (iv) no evidence for a global MWP-1B event at ∼11.3 ka BP; and (v) a progressive decrease in the rate of rise from 8.2 ka to ∼2.5 ka BP, after which ocean volumes remained nearly constant until the renewed sea-level rise at 100-150 y ago, with no evidence of oscillations exceeding ∼15-20 cm in time intervals ≥200 y from 6 to 0.15 ka BP.

1,558 citations

References
More filters
Journal ArticleDOI
15 Jul 1993-Nature
TL;DR: In this paper, the authors present a detailed stable isotope record for the full length of the Greenland Ice-core Project Summit ice core, extending over the past 250 kyr according to a calculated timescale, and find that climate instability was not confined to the last glaciation, but appears also have been marked during the last interglacial (as explored more fully in a companion paper), and during the previous Saale-Holstein glacial cycle.
Abstract: RECENT results1,2 from two ice cores drilled in central Greenland have revealed large, abrupt climate changes of at least regional extent during the late stages of the last glaciation, suggesting that climate in the North Atlantic region is able to reorganize itself rapidly, perhaps even within a few decades. Here we present a detailed stable-isotope record for the full length of the Greenland Ice-core Project Summit ice core, extending over the past 250 kyr according to a calculated timescale. We find that climate instability was not confined to the last glaciation, but appears also to have been marked during the last interglacial (as explored more fully in a companion paper3) and during the previous Saale–Holstein glacial cycle. This is in contrast with the extreme stability of the Holocene, suggesting that recent climate stability may be the exception rather than the rule. The last interglacial seems to have lasted longer than is implied by the deep-sea SPECMAP record4, in agreement with other land-based observations5,6. We suggest that climate instability in the early part of the last interglacial may have delayed the melting of the Saalean ice sheets in America and Eurasia, perhaps accounting for this discrepancy.

4,367 citations

Journal ArticleDOI
TL;DR: In this article, new values for the astronomical parameters of the Earth's orbit and rotation (eccentricity, obliquity and precession) are proposed for paleoclimatic research related to the Late Miocene, the Pliocene and the Quaternary.

3,712 citations

Journal ArticleDOI
TL;DR: An adjusted geomagnetic reversal chronology for the Late Cretaceous and Cenozoic is presented that is consistent with astrochronology in the Pleistocene and Pliocene and with a new timescale for the Mesozoic.
Abstract: Recently reported radioisotopic dates and magnetic anomaly spacings have made it evident that modification is required for the age calibrations for the geomagnetic polarity timescale of Cande and Kent (1992) at the Cretaceous/Paleogene boundary and in the Pliocene. An adjusted geomagnetic reversal chronology for the Late Cretaceous and Cenozoic is presented that is consistent with astrochronology in the Pleistocene and Pliocene and with a new timescale for the Mesozoic. The age of 66 Ma for the Cretaceous/Paleogene (K/P) boundary used for calibration in the geomagnetic polarity timescale of Cande and Kent (1992) (hereinafter referred to as CK92) was supported by high precision laser fusion Ar/Ar sanidine single crystal dates from nonmarine strata in Montana. However, these age determinations are now

3,582 citations


"A Pliocene-Pleistocene stack of 57 ..." refers background in this paper

  • ...to as SCHPS95) and Cande and Kent [1995] (hereinafter referred to as CK95) also result in higher LSR variability before 4....

    [...]

Journal ArticleDOI
10 Jun 2004-Nature
TL;DR: The recovery of a deep ice core from Dome C, Antarctica, that provides a climate record for the past 740,000 years is reported, suggesting that without human intervention, a climate similar to the present one would extend well into the future.
Abstract: The Antarctic Vostok ice core provided compelling evidence of the nature of climate, and of climate feedbacks, over the past 420,000 years. Marine records suggest that the amplitude of climate variability was smaller before that time, but such records are often poorly resolved. Moreover, it is not possible to infer the abundance of greenhouse gases in the atmosphere from marine records. Here we report the recovery of a deep ice core from Dome C, Antarctica, that provides a climate record for the past 740,000 years. For the four most recent glacial cycles, the data agree well with the record from Vostok. The earlier period, between 740,000 and 430,000 years ago, was characterized by less pronounced warmth in interglacial periods in Antarctica, but a higher proportion of each cycle was spent in the warm mode. The transition from glacial to interglacial conditions about 430,000 years ago ( Termination V) resembles the transition into the present interglacial period in terms of the magnitude of change in temperatures and greenhouse gases, but there are significant differences in the patterns of change. The interglacial stage following Termination V was exceptionally long - 28,000 years compared to, for example, the 12,000 years recorded so far in the present interglacial period. Given the similarities between this earlier warm period and today, our results may imply that without human intervention, a climate similar to the present one would extend well into the future.

1,995 citations

Journal ArticleDOI
01 Dec 1993-Nature
TL;DR: In this article, the authors present the complete oxygen isotope record for the Greenland Ice Sheet Project 2 (GISP2) core, drilled 28 km west of the GRIP core, and observe large, rapid climate fluctuations throughout the last glacial period.
Abstract: RECENT results1,2 from the Greenland Ice-core Project (GRIP) Summit ice core suggest that the climate in Greenland has been remarkably stable during the Holocene, but was extremely unstable for the time period represented by the rest of the core, spanning the last two glaciations and the intervening Eemian inter-glacial. Here we present the complete oxygen isotope record for the Greenland Ice Sheet Project 2 (GISP2) core, drilled 28 km west of the GRIP core. We observe large, rapid climate fluctuations throughout the last glacial period, which closely match those reported for the GRIP core. However, in the bottom 10% of the cores, spanning the Eemian interglacial and the previous glacia-tion, there are significant differences between the two records. It is possible that ice flow may have altered the chronological sequences of the stratigraphy for the bottom part of one or both of the cores. Considerable further work will be necessary to evaluate the likelihood of this, and the extent to which it will still be possible to extract meaningful climate information from the lowest sections of the cores.

1,885 citations


"A Pliocene-Pleistocene stack of 57 ..." refers background in this paper

  • ...The LR04 stack contains significantly more variance in benthic d18O than previously published stacks of the late Pleistocene as the result of higherresolution records, a better alignment technique, and a greater percentage of records from the Atlantic....

    [...]

  • ...The stack’s resolution of orbital-scale (23-kyr) features in the Pleistocene is comparable to that of millennial-scale (1.5-kyr) features in the GISP2 d18O record [Grootes et al., 1993], with 10–20 samples per cycle....

    [...]

Frequently Asked Questions (21)
Q1. What are the contributions mentioned in the paper "A pliocene-pleistocene stack of 57 globally distributed benthic do records" ?

The authors present a 5. This is the first benthic dO stack composed of more than three records to extend beyond 850 ka, and the authors use its improved signal quality to identify 24 new marine isotope stages in the early Pliocene. The authors also present a new LR04 age model for the Pliocene-Pleistocene derived from tuning the dO stack to a simple ice model based on 21 June insolation at 65 N. Stacked sedimentation rates provide additional age model constraints to prevent overtuning. Finally, the relative phases of the stack ’ s 41and 23-kyr components suggest that the precession component of dO from 2. 

The LR04 stack is also the first stack to extend before 2. 5 Ma and therefore offers an invaluable improvement in signal quality for the early to mid-Pliocene. Finally, the LR04 stack ’ s phase relative to precession suggests the presence of a large deep-water temperature signal from 2. 7– 1. 6 Ma and reveals a sudden change in the phase of precession response at 1. 

Because the authors emphasize obliquity in their tuning process, its phase relative to insolation is primarily determined by the lag generated by their ice model. 

Stacking records of varying resolution (while holding the total number of data points constant) tends to reduce stack error by improving the alignment accuracy of high resolution records. 

The stages which are unusually small or poorly defined in the LR04 stack are MIS 68, 69, 79, 80, 94, 102, G5, G8, G9, K2, and KM6. [34] 

Automated correlation algorithms provide the most objective correlation techniques because alignment criteria are explicit and applied consistently. 

Another important d18O reference signal is the 6-Myr composite benthic d18O sequence of Shackleton [1995] (hereinafter referred to as S95), which was constructed by placing high-resolution d18O records from three different sites (V19-30, ODP 677, and ODP 846) in series. 

Site 846 is the only record in the stack to contain both large glacial excursions, suggesting a possible coring or splicing error. 

The normalized stack, in which each LSR record is divided by its mean sedimentation rate, has a standard deviation of 0.09 in the final LR04 age model. 

The stack is generally incoherent with respect to the eccentricity component of insolation, but coherence with the obliquity component is at the 95% confidence level for most of its length and is always above the 80% confidence level. 

Phase differences of up to 11 kyr between their d18O records can be expected to reduce their stack’s precession component in particular. 

The authors align 57 benthic d18O records using an automated graphic correlation program [Lisiecki and Lisiecki, 2002], which considers all possible alignments to find the best global fit and penalizes alignments based on extreme sedimentation rates and sudden sedimentation rate changes. 

Their stacking technique, described below, is robust to the inclusion of records of varying quality because sites with higher resolution are more heavily weighted in the averaging process. 

The authors choose not to adjust the isotope curves based on their modern bottom water temperatures because the temperature differences between sites may have changed dramatically over the last 5.3 Myr. 

This age model is more reliable than one from a single d18O record because individual d18O records have more noise and fewer constraints on linear sedimentation rates (LSR) than a stack. 

Their tuning target is a simple nonlinear model of ice volume, y, which follows the equationdy dt ¼ 1 b Tm x yð Þ ð1Þwhere the nonlinearity coefficient b is subtracted during ice growth and added during ice decay [Imbrie and Imbrie, 1980]. 

Because this initial age model is derived primarily from globally averaged sedimentation rates with minimal orbital tuning, the authors avoid assumptions about the age or length of each glacial cycle. 

most of their records could be aligned to it in one piece, reducing the potential for errors where the shorter stacks join together. 

the lower precession power of the tropical stack (Figure 12) is not caused by age model differences because using the LR04 age model only increases the tropical stack’s precession power to 2.8% of total variance. [42] 

Benthic d18O records should produce a better stack than planktonic records because the deep ocean is more uniform in temperature and salinity than surface water. 

they present a second, tropical stack containing only six of these records because they find their alignment technique to be inadequate for cores with highly variable sedimentation rates.