Sulfur Isotope Stratigraphy

Abstract

The sulfur isotopic composition of dissolved sulfate in seawater has varied through time. Distinct variations and relatively high rates of change characterize certain time intervals. This allows for dating and correlation of sediments using sulfur isotopes. The variation in sulfur isotopes and the potential stratigraphic resolution of this isotope system is discussed and graphically displayed. New data are used to refine the previously published (Geologic Time Scale 2012) for the Paleocene and Eocene.

Full text

Chapter 9
Sulfur Isotope Stratigraphy
A. Paytan, W. Yao, K.L. Faul and E.T. Gray
Chapter outline
9.1 Introduction 259
9.2 Mechanisms driving the variation in the S isotope record 262
9.3 Isotopic fractionation of sulfur 263
9.4 Measurement and materials for sulfur isotope
stratigraphy 263
9.4.1 Isotope analyses 263
9.4.2 Materials for S isotope analysis 264
9.5 A Geologic time scale database 264
9.5.1 General trends 264
9.5.2 Time boundaries 265
9.5.3 Age resolution 265
9.5.4 Specific age intervals 267
9.6 A database of S isotope values and their ages for the past
130 Myr using LOWESS regression 271
9.7 Use of S isotopes for correlation 271
Bibliography 275
Abstract
The sulfur isotopic composition of dissolved sulfate in seawater
has varied through time. Distinct variations and relatively high
rates of change characterize certain time intervals. This allows
for dating and correlation of sediments using sulfur isotopes.
The variation in sulfur isotopes and the potential stratigraphic
resolution of this isotope system is discussed and graphically
displayed. New data are used to refine the previously published
(Geologic Time Scale 2012) for the Paleocene and Eocene.
9.1 Introduction
Sulfur isotope biogeochemistry has broad applications to
geological, biological, and environmental studies. Sulfur
is an important constituent of the Earth’s lithosphere, bio-
sphere, hydrosphere, and atmosphere and occurs as a
major constituent or in trace amounts in various compo-
nents of the Earth system. Many of the characteristics of
sulfur isotope geochemistry are analogous to those of car-
bon and nitrogen, as all three elements occur in reduced
and oxidized forms, and undergo an oxidation state
change as a result of biological processes.
Sulfur as sulfate (SO
4
22
) is the second most abundant
anion in modern seawater with an average present-day
concentration of 28 mmol/kg. It has a conservative distri-
bution with uniform SO
4
22
/salinity ratios in the open
ocean and a very long residence time of close to 10 mil-
lion years (Chiba and Sakai, 1985; Berner and Berner,
1987). Because of the large pool of sulfate in the ocean, it
is expected that the rate of change in either concentration
or isotopic composition of sulfate will be small, thus
reducing the utility of this isotope system as a viable tool
for stratigraphic correlation or dating.
However, as seen in Figs. 9.19.4, the isotopic record
shows distinct variations through time, and at certain inter-
vals, the rate of change and the unique features of the record
may yield a reliable numerical age. The features in the
recordcanalsobeusedtocorrelate between stratigraphic
sections and sequences. This is particularly important for
sequences dominated by evaporites, where fossils are not
abundant or have a restricted distribution range, paramag-
netic minerals are rare, and other stratigraphic tools (e.g.,
oxygen isotopes in carbonates) cannot be utilized.
While the potential for the utility of sulfur isotope
stratigraphy exists, this system has not been broadly
applied. The examples for the application of S isotopes
for stratigraphic correlations predominantly focus on the
Neoproterozoic and often employ other methods of correla-
tion such as
87
Sr/
86
Sr and δ
13
Caswell(Misi et al., 2007;
Pokrovskii et al., 2006; Walter et al., 2000; Hurtgen et al.,
2002; Planavsky et al., 2012; Scott et al., 2014).
It is important to note that the method works only for
marine minerals containing sulfate. Moreover, it is crucial
that the integrity of the record be confirmed to insure the
pristine nature of the record and lack of postdepositional
alteration (Kampschulte and Strauss, 2004; Crockford
et al., 2019). In the application of sulfur isotopes, it is
assumed that the oceans are homogeneous with respect to
259
Geologic Time Scale 2020. DOI: https://doi.org/10.1016/B978-0-12-824360-2.00009-7
©2020 Elsevier B.V. All rights reserved.

sulfur isotopes of dissolved sulfate and that they always
were so. As noted, previously, uniformity is expected
because of the long residence time of sulfate in the ocean
(millions of years) compared to the oceanic mixing time
(thousands of years) and because of the high concentra-
tion of sulfate in seawater compared to the concentration
in major input sources of sulfur to the ocean (rivers,
hydrothermal activity, and volcanic activity). Indeed, in
the present-day ocean, seawater maintains constant sulfur
isotopic composition (at an analytical precision of
B0.2m) until it is diluted to salinities well below those
supportive of fully marine fauna (Crockford et al., 2019)
invalidating this assumption and limiting the utility of sul-
fur isotopes for stratigraphic correlation during such time
intervals. The main limitation to the broader application
of this isotope system for stratigraphy and correlation is
the lack of reliable, high-resolution, globally representa-
tive isotope records that could be assigned a numerical
age scale. As such records become available the utility of
this system could expand considerably.
FIGURE 9.1 Evaporite records (Claypool et al., 1980). Solid lines represent data from Claypool et al. and data he compiled from the literature plot-
ted at their most probable age. Dashed lines show the range of all available few analyses for each time interval. The heavy line is the best estimate of
δ
34
S of the ocean. The shaded area is the uncertainty related to the curve.
260 PART | II Concepts and Methods

FIGURE 9.2 Seawater sulfate S isotope curve from
marine barite for 130 Ma to present. Paytan et al.,
1998;Paytan et al., 2004;Turchyn et al., 2009;
Markovic et al., 2015;Markovic et al., 2016;Yao et
al., 2018;Yao et al., 2020.
FIGURE 9.3 The Phanerozoic seawater sulfate δ
34
S record.
Green circles 5CAS data (Ueda et al., 1987; Strauss, 1993;
Kampschulte and Strauss, 2004; Goldberg et al., 2005;
Mazumdar and Strauss, 2006; Gill et al., 2007; Hurtgen
et al., 2009; Turchyn et al., 2009; Wu et al., 2010, 2014;
Thompson and Kah, 2012;Wotte et al., 2012;Presentetal.,
2015;Sim et al., 2015;Kah et al., 2016;Schobben et al.,
2017;Rennie et al., 2018); gray circles 5evaporites data
(Holser and Kaplan, 1966; Sakai, 1972; Claypool et al.,
1980; Cortecci et al., 1981; Pierre and Rouchy, 1986; Das
et al., 1990;Rick, 1990;Utrilla et al., 1992;Fox and
Videtich, 1997;Strauss, 1997;Worden et al., 1997;
Kampschulte et al., 1998;Strauss, 1993;Strauss et al., 2001;
Longinelli and Flora, 2007; Orti et al., 2010; Peryt et al.,
2005;Surakotra et al., 2018;Crockford et al., 2019); blue
dash line5the modern seawater sulfate δ
34
S value of B21m.
CAS, Carbonate-associated sulfate.
Sulfur Isotope Stratigraphy Chapter | 9 261

9.2 Mechanisms driving the variation in
the S isotope record
The chemical and isotopic composition of the ocean changes
over time in response to fluctuations in global weathering
rates and riverine loads, volcanic activity, hydrothermal
exchange rates, sediment diagenesis, and sedimentation and
subduction processes. All of these are ultimately controlled
by tectonic and climatic changes. Specifically, the oceanic
sulfate δ
34
S at any given time is controlled by the relative
proportion of sulfide and sulfate input and removal from the
oceans and their isotopic compositions (e.g., Bottrell and
Newton, 2006). S is commonly present in seawater and
marine sediments in one of two redox states:
1. in its oxidized state as sulfate and sulfate minerals and
2. in its reduced form as H
2
S and sulfide minerals.
The oceanic sulfate δ
34
S record provides an estimate
for the relative partitioning of S between the oxidized and
reduced reservoirs through time. Changes in both input
and output of sulfur to/from the ocean have occurred in
response to changes in the geological, geochemical, and
biological processes (Strauss, 1997; Berner, 1999). These
changes are recorded in contemporaneous authigenic
minerals that precipitate in the oceanic water column.
Seawater contains a large amount of S
(B40 310
18
mol) that is present, as it has been for at least
the past 500 million years, predominantly as oxidized, dis-
solved sulfate (SO
4
22
)(Holser et al., 1988; Berner and
Canfield, 1989, 1999). Ancient oceans may have at times
had lower sulfate concentrations and thus sulfate residence
timesmayhavebeenshorter(
Lowenstein et al., 2001;
Horita et al., 2002). The largest input today is from river
runoff from the continent. The δ
34
S value of this source is
variable (0m10m) but typically lower than seawater and
depends on the relative amount of gypsum and pyrite in the
drainage basin (Krouse, 1980; Arthur, 2000). Volcanism
and hydrothermal activity also are small sources of S for
the ocean, with δ
34
Scloseto0m(Arthur, 2000). The output
flux is via deposition of evaporites and other sulfate-
containing minerals (δ
34
S
evaporite
δ
34
S
seawater
) and sulfides
with δ
34
S pyrite 15m(Krouse, 1980;Kaplan, 1983). The
typically light isotope ratios of sulfides are a result of the
strong S isotope fractionation involved in bacterial sulfate
reduction, the precursor for sulfide mineral formation
(Krouse, 1980;Kaplan, 1983). This results in the S isotope
ratios of seawater sulfate being higher than any of the input
sources to the ocean. Seawater sulfate today has a constant
δ
34
S value of 21.0m60.2m(Rees et al., 1978). It has also
been suggested that in addition to changes in the relative
rate of burial of reduced and oxidized S, the marine δ
34
S
record has been sensitive to the development of a signifi-
cant reservoir of H
2
S in ancient stratified oceans (Newton
et al., 2004). Specifically, extreme changes over very short
geologic time scales (such as at the PermianTriassic
boundary or the PETM) along with evidence for ocean
anoxia could only be explained via the development of a
large, relatively short-lived, reservoir of H
2
Sinthedeep
FIGURE 9.4 The Proterozoic seawater sulfate δ
34
S
curve. Green circles 5CAS data; gray
circles 5evaporites data; Black circles 5barite data
(Crockford et al., 2019 and references therein). Blue
dash line 5the modern seawater sulfate δ
34
S value of
B21m. The blue and purple boxes denote the periods
of the Great Oxygenation Event (24502000 Ma) and
Cryogenian (635717 Ma), respectively. CAS,
Carbonate-associated sulfate.
262 PART | II Concepts and Methods

oceanic water column followed by oceanic overturning and
reoxygenation of the H
2
S(Newton et al., 2004; Algeo
et al., 2007; Luo et al., 2010; Yao et al., 2018).
The evidence that the S isotopic composition of sea-
water sulfate has fluctuated considerably over time, until
recently, was based on comprehensive, though not contin-
uous, isotope data sets obtained from marine evaporitic
sulfate deposits and pyrite (Claypool et al., 1980; Strauss,
1993). More recently, marine barite has been used to con-
struct a continuous, high-resolution Scurve for the last
130 Ma (Paytan et al., 1998, 2004; Turchyn et al., 2009;
Markovic et al., 2015, 2016; Yao et al., 2018, 2020).
Methods to analyze the sulfate that is associated with
marine carbonate deposits (carbonate-associated sulfate,
CAS) have also been developed, and new data sets using
these methods are becoming available. Specifically, CAS
has been used to reconstruct global change in the sulfur
cycle on both long (Kampschulte and Strauss, 2004) and
short (Ohkouchi et al., 1999; Kampschulte et al., 2001)
time scales. Particularly, CAS data from Foraminifera
that is species-adjusted for fractionation offsets can yield
high-quality data (Rennie et al., 2018). The new data
from barite and from CAS show considerably more detail
and fill significant gaps in the former data sets, revealing
previously unrecognized structure and increasing the
potential for seawater S isotope curves to serve as a tool
for stratigraphy and correlation.
9.3 Isotopic fractionation of sulfur
The sulfur isotope fractionation between evaporitic sulfate
minerals and dissolved sulfate is approximately 1m2m
(Thode and Monster, 1965). Experiments and analyses of
modern evaporites show values 1.1m60.9mheavier than
dissolved ocean sulfate (Holser and Kaplan, 1966).
Modern barites measured by the SF
6
method averaged
0.2mheavier than dissolved ocean sulfate (Paytan et al.,
1998). Carbonates are also expected to have minor frac-
tionation associated with the incorporation of sulfate. The
similarity between the δ
34
S value of sulfate minerals and
dissolved sulfate means that ancient sulfates can be used
as a proxy for the δ
34
S value of the ocean at the time that
the minerals formed.
Reduced S compounds are mostly produced in associa-
tion with processes of bacterial sulfate reduction.
Dissimilatory reduction (converting sulfate to sulfide) is
performed by heterotrophic organisms, particularly sulfate-
reducing bacteria. Bacterial sulfate reduction is an energy-
yielding, anaerobic process that occurs only in reducing
environments (Goldhaber and Kaplan, 1974; Canfield,
2001). Measured fractionations associated with sulfate
reduction under experimental conditions range from 220m
to 246mat low rates of sulfate reduction to 210mat high
reduction rates. The δ
34
S values of sulfides of modern
marine sediments are typically around 240m; however, a
wide range from 240mto 13mis observed. Sulfate reduc-
tion and iron sulfide precipitation continues only as long as:
1. sulfate is available as an oxidant,
2. organic matter is available for sulfate-reducing bacte-
ria, and
3. reactive iron is present to react with H
2
S.
In the marine environment, neither sulfate nor iron
generally limits the reaction. Instead, it is the abundance
of easily metabolized carbon that controls the extent of
sulfate reduction. The broad range of δ
34
S values
observed in sulfides from marine sediments results from
variable fractionation associated with the different sedi-
mentary settings and environmental conditions during sul-
fate reduction (temperature, porosity, diffusion rates, etc.)
as well as other processes in the S cycle that involve frac-
tionation such as sulfur disproportionation reactions
(Canfield and Thamdrup, 1994; Habicht et al., 1998).
Assimilatory reduction occurs in autotrophic organ-
isms where sulfur is incorporated in proteins, particularly
as S
2
2
in amino acids. Assimilatory reduction involves a
valence change from 16to22. The bonding of the prod-
uct sulfur is similar to the dissolved sulfate ion, and frac-
tionations are small (10.5mto 24.5m,Kaplan, 1983).
The δ
34
S value of organic sulfur in extant marine organ-
isms incorporated by assimilatory processes is generally
depleted by 0mto 5mrelative to the ocean.
The wide array of environmental conditions that affect
the fractionation, together with the broad range of S isoto-
pic values of sulfide minerals at any given time, and post-
depositional alteration of assimilatory S into organic
matter, limits the utility of sulfites and S in old organic
matter as tools for stratigraphy and correlation, since mea-
sured values may not be representative of a global oceanic
signature.
9.4 Measurement and materials for sulfur
isotope stratigraphy
9.4.1 Isotope analyses
There are four stable isotopes of sulfur. The isotopes that
are commonly measured are
34
S and
32
S, as these are the
two most abundant of the four. In most but not all sam-
ples, the sulfur isotopes are present in constant ratios to
each other, thus the others could be easily computed (but
see Farquhar et al., 2000). All values are reported as δ
34
S
relative to the Cano
˜n Diablo Troilite (CDT) standard
(Ault and Jensen, 1963) using the accepted delta notation.
Due to scarcity of the CDT standard, secondary synthetic
argentite (Ag
2
S) and other sulfur-bearing standards have
been developed, with δ
34
S values being defined relative to
Sulfur Isotope Stratigraphy Chapter | 9 263

the accepted CTD value of 0m. Samples are converted to
gas (SO
2
or SF
6
) and analyzed on a gas-ratio mass spec-
trometer. Analytical reproducibility is typically 60.2m.
9.4.2 Materials for S isotope analysis
9.4.2.1 Evaporites
Records of oceanic sulfur isotopes through time were
originally reconstructed from the analyses of marine evap-
oritic sulfate minerals (Holser and Kaplan, 1966;
Claypool et al., 1980). Evaporites contain abundant sul-
fate and their formation involves minimal and
predictable fractionation, thus they are suitable archives
for this analysis. Claypool et al. (1980) presented the first
compilation of the secular sulfur isotope record of seawa-
ter for the Phanerozoic (Fig. 9.1) and their work provides
the basis for our understanding of the sulfur isotope
record. However, as a result of the sporadic nature of
evaporite formation through geologic time this record is
not continuous. Moreover, evaporites are hard to date pre-
cisely due to the limited fossil record within these
sequences; thus the stratigraphic age control on the
evaporitic-based sulfur isotope record is compromised.
9.4.2.2 Barite
Like evaporites, the δ
34
S of barite is quite similar to that
of sulfate in the solution from which it precipitated.
Marine barite precipitates in the oceanic water column
and is relatively immune to diagenetic alteration after
burial thus it records the changes in the sulfur isotopic
composition of seawater through time (Paytan et al.,
1998, 2004; Turchyn et al., 2009; Markovic et al., 2015,
2016; Yao et al., 2018, 2020). Moreover, high-resolution,
well-dated, and continuous records can be developed as
long as barite-containing pelagic marine sediments are
available (Paytan et al., 1993). It must be stressed that
reliable seawater sulfur isotope records can only be
derived from marine (pelagic) barite and not diagenetic or
hydrothermal barite deposits (see Eagle et al., 2003 for
more details). A sulfur isotope curve was obtained from
pelagic marine barites of Cretaceous and Cenozoic ages
with unprecedented temporal resolution (Paytan et al.,
1998, 2004;Fig. 9.2). The high-resolution curve shows
some very rapid changes that could be instrumental for
stratigraphic applications.
9.4.2.3 Substituted sulfate in carbonates
Sulfur is a ubiquitous trace element in sedimentary carbo-
nates (e.g., CAS). Concentrations range from several tens
of ppm in inorganic carbonates to several thousand ppm
in some biogenic carbonates (Burdett et al., 1989;
Kampschulte et al., 2001; Lyons et al., 2004). While the
mechanism of sulfate incorporation into carbonates is not
fully understood, CAS is incorporated with little fraction-
ation thus recording seawater ratios. Carbonates offer an
attractive method for refining the secular sulfur curve
because of their abundance in the geological record, ease
of dating, and relatively high accumulation rates. Indeed,
a record for Phanerozoic seawater sulfur isotopes based
on CAS has been compiled and published (Kampschulte
and Strauss, 2004;Fig. 9.3). Extreme caution must, how-
ever, be exercised in extracting CAS from samples and
interpreting the sulfur isotope data obtained because car-
bonates are highly susceptible to postdepositional alter-
ation and secondary mineral precipitation that can
obliterate the record. The degree of modification can be
assessed by obtaining multiple records from distinct loca-
tions (or mineral phases) for the same time interval and
construction of secular trends (Kampschulte and Strauss,
2004). Recent work largely overcame these disadvantages
by using CAS from single shells of different species of
Foraminifera and correcting the data for offsets between
species (Rennie et al., 2018).
9.5 A Geologic time scale database
9.5.1 General trends
The current sulfur isotope records include data sets from
the Proterozoic to the present (Figs. 9.39.5). While the
focus of most studies is on shorter time scales and the
methods that are used are varied, the overlap among pub-
lished records and a few long-term studies serve to give a
comprehensive view of the sulfur isotope record for the
Phanerozoic. Three long-term records have been compiled,
two based on evaporites (Claypool et al., 1980; Strauss,
1997) and one based on CAS (Kampschulte and Strauss,
2004). A compilation of data for the Proterozoic was also
published (Crockford et al., 2019). Sulfate concentrations
in the Proterozoic ocean, however, were much lower than
during the Phanerozoic (e.g., Habicht et al., 2002;Kah
et al., 2004;Canfield and Farquhar, 2009); hence, it is
likely that the oceanic water column was not homogenous
with respect to sulfur isotopes limiting the applicability of
S isotopes for stratigraphy and correlation.
General trends can be seen in these records. The
Proterozoic data show widespread with positive excursions
across the Great Oxidation Event and the lower
Neoproterozoic. In the Cambrian the average δ
34
Svalueis
34.8 62.8min the CAS record (Kampschulte and Strauss,
2004) and around 30min the evaporite record (Claypool,
et al., 1980; Strauss, 1997). These relatively high values are
sustained through the Cambrian in the CAS record, ending
with anomalously high δ
34
S values at the Cambrian/
Ordovician boundary. After this point the δ
34
S decreases
steadily through the remainder of the Paleozoic, reaching a
minimum at the Permian/Triassic boundary with an average
264 PART | II Concepts and Methods

value of 13.2 62.5m. A similar but less time-constrained
decrease is seen in the evaporite record.
Through the Mesozoic, the δ
34
S values are generally
lower than in the Paleozoic, ranging between 14mand
20m. The δ
34
S values increase quite rapidly from
13.2 62.5mat the Permian/Triassic boundary to 17min
the Jurassic and decrease again to about 15min the early
Cretaceous (Claypool et al., 1980; Strauss, 1997;
Kampschulte and Strauss, 2004). The value at the
Cretaceous is about 19mbut two distinct excursions
toward lower values are seen: one at B120 Ma and the
other at B90 Ma (Paytan et al., 2004). A decrease in δ
34
S
values from B20mto 16mis seen in the Paleocene before
climbing sharply in the Early to Middle Eocene to the
near modern value of 21mwhere it remains steady for the
remainder of the Cenozoic (Fig. 9.2).
These broad trends can be useful in obtaining very
general stratigraphic information (e.g., typically only at
the epoch scale) but are not applicable for age assign-
ments at resolution better than tens of millions of years.
9.5.2 Time boundaries
Strauss (1997) reviewed secular variations in δ
34
S across
time boundaries characterized by profound biological or
geological changes. Due to the paucity of evaporite data,
all these time boundary studies have used data obtained
from sedimentary sulfides. The premise behind the study
of S isotope excursions at age boundaries is based on the
expected perturbations in the biosphere which may impact
sulfate reduction rates. During a catastrophic event, where
productivity plunges, the δ
34
S values of the oceans are
expected to decrease because of a reduction in organic
matter availability, leading to lower sulfate reduction. The
subsequent biological radiations should have the opposite
effect. Accordingly, the δ
34
S values of the oceans should
first decrease across a time boundary associated with a
catastrophic extinction or major ecosystem reorganization
and then increase during the period of recovery. The mag-
nitude of the effect is related to the intensity of the extinc-
tion event, the rate of recovery, and the size of the
oceanic sulfur reservoir.
Four extinction events have been studied (see Strauss,
1997 for references): the PrecambrianCambrian, the
FrasnianFamennian, the PermianTriassic, and
the CretaceousTertiary boundaries. Of these, only the
PermianTriassic event shows the expected sulfur trend
(Luo et al., 2010). Fluctuations occur at the other bound-
aries, but no secular (globally concurrent) variations
have been observed (see also Newton et al., 2004). In
part the reason for the inconsistent results between sec-
tions and between extinction events may be related to
the inherent problems of analyzing sulfides instead of
sulfates and the multitude of controls impacting the iso-
topic composition of sulfides. Therefore local effects
may mask any global sulfur variations. More recent data
using CAS Sim et al. (2015) correlated the S isotope
record among sections throughout the world representing
the FrasnianFamennian boundary of the Devonian.
9.5.3 Age resolution
Age resolution of the S isotope curve varies with the type
of data comprising the record and the specific objectives
FIGURE 9.5 LOWESS curve for the last 130 mil-
lion years generated from marine barite data (Paytan
et al., 1998, 2004; Turchyn et al., 2009; Markovic
et al., 2015, 2016; Yao et al., 2018, 2020); see also
Table 9.1.
Sulfur Isotope Stratigraphy Chapter | 9 265

for the various studies producing the data. The older sec-
tions compiled from evaporite and CAS data have a lower
resolution because of the scarcity of evaporites and
because CAS depends on the integrity of the carbonates
and fossils used for reconstruction, which in many loca-
tions, are subjected to extensive postdepositional alter-
ation. In addition, large temporal gaps between samples
make it difficult to correlate between sites and thus make
exact age determinations challenging. Despite these lim-
itations robust records exist for specific time periods and
the confidence within each such time interval is consider-
ably improved from the earlier evaporate records. Age
resolution of records based on barite is much better but so
far barite has been recovered predominantly from pelagic
sediments, limiting the applicability to the last 130 Ma.
The Phanerozoic evaporite record, compiled by
Claypool et al. (1980) with further work done by Strauss
(1997), has several characteristics that make it difficult to
use for S stratigraphy. First, the record has large gaps in it
that leave long periods of time unaccounted for. In
Claypool et al. (1980) a best estimate curve was visually
approximated to combine and extrapolate between dispa-
rate data sets; however, this eliminates the ability to
detect finer fluctuations that may be present. Second, the
absolute S isotope values recorded at each time point
range considerably, confounding the issue. The range of
δ
34
S values within each time interval is approximately 5m
for most of the data sets, which makes pinpointing an age
from a stratigraphic perspective difficult since in many
cases the broad fluctuations that occur over time are
within 65m(Fig. 9.1). Third, the ages used for each
sample are approximate due to the scarcity of fossils in
sections used to compile the isotope curves. Even in the
evaporite record from Strauss (1993) that derives its ages
after Harland et al. (1990), the age uncertainty spans
more than 10 million years depending on the segment (or
specific time range), which makes it difficult to use these
data for stratigraphic correlation (Strauss, 1993).
The S isotope record derived from CAS is more robust
(Fig. 9.3). The record is consistent with the evaporite data
in the broad strokes (Fig. 9.4) but a better constraint on
the ages of the samples is possible. The data set presented
in Kampschulte and Strauss (2004) and references therein
show a record for the Phanerozoic that reduces the uncer-
tainty in age and S isotope values considerably from those
associated with evaporites. The CAS samples were taken
from stratigraphically well-constrained biogenic calcites
(using the time scale of Harland et al., 1990) with a reso-
lution of 15 million years within data sets. However,
the data sets analyzed are not continuous, leaving gaps,
that while not as glaring as those in the evaporite record,
still limit the accuracy of a smooth curve and may miss
finer details. The CAS data that represent older ages have
a wider range of S isotope values than that of more recent
(younger) samples. For example, a “scatter” of 610m
and even up to 20min the Cambrian and Ordovician for
samples with similar ages. More recent samples have nar-
rower ranges, from 5mto 10m, and thus would be more
useful for stratigraphy, although in some places, the low
temporal resolution still makes it difficult to distinguish
noise from trend (Kampschulte and Strauss, 2004).
The data compiled and presented in Kampschulte and
Strauss (2004) use a moving average to create a continuous
curve (Fig. 9.4). The effect is to smooth out the observed
variation that then makes it difficult to assess the error
associated with both the isotope data set (e.g., δ
34
S) and
the age resolution. This makes it difficult to resolve trends
and compare the data with other records or to use the curve
for precise sample age determination. The smoothed curve
of Kampschulte and Strauss (2004) can, however, be used
to assess the utility of certain sections (age intervals) of the
record for dating using S stratigraphy, but because the spe-
cific data sets used to produce the smooth curve were not
available to us, evaluation of age resolution or a detailed
statistical LOWESS fit (McArthur et al., 2001) for deriva-
tion of numeric ages using the CAS record cannot be com-
piled at this time. The analysis of δ
34
S hosted in the calcite
lattice of single-species foraminifera vastly improved stra-
tigraphy afforded by CAS-based records although correc-
tions for species-specific fractionation must be applied
(Rennie et al., 2018). The published Cenozoic foraminifera
record agrees well with the barite-derived record (Yao
et al., 2020).
The marine barite record presented by Paytan et al.
(1998, 2004) is derived from ocean floor sediment. The
current record goes back B130 Ma. The barite-based
S isotope curve provides a record with a resolution of less
than 1 million years with very few gaps. The age of the
samples is constrained by biostratigraphy and Sr isotopes
and typically has an error of less than 100,000 years. The
continuous and secular (based on data from multiple sites
for each time interval) nature and the high resolution of
this record illuminate finer features that are missed in the
lower resolution evaporite and CAS records. The record
also has a narrower range of S isotope values for each
time point, further constraining the curve. These features
make it the most robust of the three available records thus
far and the most useful for stratigraphy, for the periods it
covers. This record serves to illustrate the potential use of
S isotopes for stratigraphy and as more such detailed
high-resolution secular records (e.g., based on coherent
data from multiple locations and settings) become avail-
able for different geological periods, S isotope stratigra-
phy can be more widely utilized. At the moment the
limited availability of continuous high-resolution secular
data and the need for updated and better constrained ages
for previously published records are the biggest obstacles
to using sulfur isotopes as a stratigraphic tool.
266 PART | II Concepts and Methods

9.5.4 Specific age intervals
While the current S record of the Phanerozoic is not ideal
for stratigraphic applications as discussed previously,
there is still potential for using S as a stratigraphic tool
for certain time intervals. The time periods best suited to
dating are those that are distinguished by rapid changes in
δ
34
S. Identifying smaller fluctuations on the “plateaus” of
the isotope curve is difficult because of the limited tem-
poral resolution, and the relatively large error in the δ
34
S
compared to the small fluctuations. These limitations
make the potential use of fine features for stratigraphic
and correlation purposes impossible at this stage.
At this time the most useful record for S stratigraphy
applications is the marine barite curve that extends back
to 130 Ma. The distinct features that appear in this high-
resolution curve show five time periods with relatively
abrupt changes in δ
34
S that could lead to precise dating:
130116, 10796, 9686, 8375, 6540, and B2Ma
to the present. Resolving ages during periods of smaller
fluctuations is possible but would likely necessitate a
much larger data set in order to match multiple points and
avoid offsets between data from distinct sites. The pla-
teaus, notably from B30 Ma to about 2 Ma where the
S isotope values do not significantly change, are not
useful because there are few features that can be teased
out and distinguished from sampling and analytical error.
Next we present the trends in the δ
34
S isotope data for
each time period and a brief discussion of the utility of
the data for stratigraphy is presented. Kampschulte and
Strauss (2004) showed that the Phanerozoic CAS record
is consistent with and better constrained temporally than
the evaporite record. For this reason the trends discussed
next will rely on the CAS record from the Cambrian to
the Jurassic (Kampschulte and Strauss, 2004, and refer-
ences therein) and the barite record from Paytan et al.,
1998, 2004;Turchyn et al., 2009;Markovic et al., 2015,
2016; and Yao et al., 2018, 2020, from the Cretaceous to
the present, unless otherwise specified. Recent studies
also showed that multiple sulfur isotopes (
33
S and
36
S) of
sulfate in the Proterozoic could be powerful tools for stra-
tigraphy (e.g., Crockford et al., 2019;Farquhar and Wing,
2003;Johnston, 2011 and references therein). However,
the use of
33
S and
36
S has so far been limited and will not
be further discussed here.
9.5.4.1 Cambrian
The seawater δ
34
S records for the Cambrian are derived
from carbonate and evaporite rocks (and a few from barite)
in Australia, Canada, China, India, Russia, Spain, and
France (Goldberg et al., 2005; Hough et al., 2006; Hurtgen
et al., 2009; Mazumdar and Strauss, 2006; Peryt et al.,
2005; Wotte et al., 2012).Thevaluesrecordedrepresenta
wide range. The data show an excursion with a maximum
of 50min the lower Cambrian, followed by a systematic
.15mdecrease across the middleupper Cambrian. The
mean value is relatively high ( .30m), although it is
unclear if these high values reflect open ocean seawater
sulfate or if the integrity of these samples was compro-
mised. The high values and intrabasin variability may par-
tially result from the intrabasin microbial sulfate reduction
under sulfate limitation or diagenetic processes as well as
euxinic conditions (Goldberg et al., 2005; Mazumdar and
Strauss, 2006; Peryt et al., 2005; Hough et al., 2006).
The age resolution that can be theoretically obtained
using the moving mean curve is 2.0 Myr from 535 to
525 Ma and 2.8 Myr from 525 to 511 Ma (but note that
the curve averages values over 5 Myr) (Kampschulte and
Strauss, 2004). When looking at the raw data, one sees
that there is a significant age gap between the two time
periods sampled that is smoothed over in the moving
mean. In addition, while the δ
34
S values in both data sets
are relatively high ( .30m) and can be used to identify
samples of Cambrian age, the range of values is similar
for both sets and thus without a larger data set that fills in
the gaps, distinguishing between older and younger sam-
ples within the Cambrian may be difficult. The global
nature of the record should also be verified as sulfate was
most likely a nonconservative anion in the Cambrian
ocean (Wotte et al., 2012).
9.5.4.2 Ordovician
The CAS record in the Ordovician is composed of 16 sam-
ples. The temporal resolution of the record is between 1
and 8 Myr with the older samples dominantly B4 million
years apart and the younger samples 1 million years apart.
The δ
34
S values were determined from whole rock in 15
of these samples, and for 12 of them brachiopod shells
were also used. The record shows a decrease from a mov-
ing mean of 30min the Lower Ordovician to 24min the
uppermost Ordovician (Kampschulte and Strauss, 2004).
The wide range of the measured δ
34
S values
(15m30m) throughout the period complicates the pic-
ture. Without a higher resolution data set it is impossible
to distinguish whether the broad range represents real
fluctuations and the lower values (15m) are a true mini-
mum. Specifically, when considering the time resolution
of the record, values of 15mand B30mthat occur within
the same time frame render the use of such records unreli-
able. However, on a broader scale, the moving average of
δ
34
S values, which plateaus around 24mat B475 Ma and
remain at that level up to the Ordovician/Silurian bound-
ary, can be distinguished from other time periods.
9.5.4.3 Silurian
The Silurian shows a continued trend of decreasing δ
34
S
values with a range from 35.6mto 21.5min the CAS
Sulfur Isotope Stratigraphy Chapter | 9 267

record in 15 brachiopod shells and 17 whole rock samples
over 30 Myr (Kampschulte and Strauss, 2004). The
Ordovician/Silurian boundary exhibits the higher values
(30m35, which drop by 1m2min the Early Silurian.
Following is a narrower range of S isotope values from
B24mto 28mand the moving mean shows a plateau in
the record. The running mean seems to smooth away the
slight downward trend seen in the raw data. Having the
mean at odds with the trend in the raw data makes utility
of the curve from this section within the Silurian difficult
to use for stratigraphic dating because there is no good
method to resolve the inconsistencies without a more
complete record. Nevertheless, the range from B24mto
28mis distinctive to the Late Ordovician and Silurian.
9.5.4.4 Devonian
A total of 18 samples comprise the record for the
Devonian. δ
34
S values in the Devonian show a downward
trend, decreasing from B25min the Late Silurian to
B19min the lower Middle Devonian. The steep slope of
the curve from 408 to 395 Ma makes it useful for stratigra-
phy, specifically a 6mchange over 13 million years and an
isotope analytical error of 0.2mcan yield an age resolution
in the range of 0.5 million years. In the second section,
from 395 to 381 Ma, the curve plateaus: the moving aver-
age remains around 18.819.2. The remainder of the
Devonian exhibits a distinctive peak with δ
34
Sincreasing
from 23min the Frasnian age of the Late Devonian
(371 Ma) to a maximum of 26.9m(Kampschulte and
Strauss, 2004). The age resolution of the data set varies
from 1 to 4 Myr with a gap of 8 million years over the
Devonian/Carboniferous boundary. The shape of the curve
makes this section distinct and thus potentially useful for
stratigraphy; however, the moving mean currently smooths
the data. It is noteworthy that Sim et al. (2015) correlated
the S isotope record among sections throughout the world
representing the FrasnianFamennian boundary, despite
relatively low-resolution data available at that time. The
generally similar B5mdecline in seawater δ
34
S has been
reported for sections in the United States, Belgium, and
Poland, which has the potential for correlation applications
as seen in Fig. 9.6 (Sim et al., 2015 and references therein).
Moreover, the δ
34
Sandδ
13
C excursions may be linked to
the Late Devonian mass extinction (Sim et al., 2015). It is,
however,importanttoobtainmoredatawithbetterdefined
ages from diverse sites to verify a global trend.
9.5.4.5 Carboniferous
The Carboniferous is also characterized by a decrease in the
CAS data from B20min the Early Carboniferous
(Mississippian) to B15mat 334 Ma where it remains until
decreasing to around 12min the Late Carboniferous
(Pennsylvanian: Kampschulte et al., 2001;Kampschulte and
Strauss, 2004;Surakotra et al., 2018). The age resolution of
the record, based on the moving mean, ranges from 5.6 Myr
from 362 to 334 Ma in the Mississippian and 34Myr for
the remainder of the period. The overall range of values in
the raw data is narrower than for other section, which makes
distinguishing between noise and trend easier. However, the
values plateau from 342.8 to 309.2 Ma and leave only the
beginning and end of the period significantly distinguishable
for stratigraphic correlation. Thus there is a potential for
stratigraphic applications for the Early and Late
Carboniferous provided the available data are indeed
FIGURE 9.6 Sulfur and carbon isotope records across the FrasnianFamennian boundary. There is a brief δ
34
S drop throughout the linguiformis bio-
zone and a positive δ
13
C excursion starting in the uppermost part of this biozone. The shaded area denotes the linguiformis conodont biozone.
Abbreviations: L. rhenana, Late rhenana;ling.,linguiformis E.M. triang., Early to middle triangularis. Figure after Sim et al. (2015).
268 PART | II Concepts and Methods

representative of global trends. The potential age resolution
for these time intervals is in the range of about 1 million
years (5mchange over about 20 Myr).
9.5.4.6 Permian
The Permian record maintains the low δ
34
S values that
characterize the end of the Carboniferous, around 12m.
This value is seen in the 16 samples analyzed for the
Permian (Kampschulte and Strauss, 2004). This overall
δ
34
S value is distinctive for the period and is useful for
dating the period as a whole but the plateau in the record
does not lend itself to more precise stratigraphic dating or
correlation within the Permian.
The Permian/Triassic boundary has been sampled at
higher resolution of 1 Myr (Kramm and Wedepohl, 1991;
Scholle, 1995; Newton et al., 2004; Algeo et al., 2007;
Gorjan et al., 2007) and shows distinct fluctuations that
are useful stratigraphically (see next).
9.5.4.7 Triassic
The transition from the Paleozoic to the Mesozoic is char-
acterized by an abrupt increase in the seawater δ
34
S value
from 12min the upper Permian to a maximum value of
B30macross the PermianTriassic boundary (Cortecci
et al., 1981; Worden et al., 1997; Kampschulte and
Strauss 2004; Newton et al., 2004; Algeo et al., 2007;
Longinelli and Flora, 2007; Luo et al., 2010; Song et al.,
2014; Schobben et al., 2017; Bernasconi et al., 2017).
This peak value occurs at the top of the PermianTriassic
extinction interval followed by a sharp drop to around a
mean of 17min the lower and middle Triassic. These
data have been sampled from worldwide locations at a
temporal resolution of less than 1 million years (Fig. 9.7),
indicating that the striking fluctuation is a predominant
and global signal. Previous studies interpreted such
extreme changes as evidence for the development of a siz-
able, relatively short-lived reservoir of reduced sulfur in
the deep oceanic water column followed by oceanic over-
turning and sulfide reoxidation (Newton et al., 2004;
Algeo et al., 2007; Luo et al., 2010; Bernasconi et al.,
2017). The estimated seawater sulfate concentrations
were relatively low for the end Permian and the early
Triassic, varying between 2 and 6 mM (Bernasconi et al.,
2017). More importantly, the positive excursion of more
than 10mover a time scale of a few million years or even
less allows for robust stratigraphic correlations (e.g.,
Luo et al., 2010). For the remainder of the Triassic the
seawater δ
34
S value remains relatively constant at
approximately 16m, followed by short-term fluctuations
between 11mand 25min the uppermost Triassic. The
period of distinct variations is potentially suitable for
correlations.
9.5.4.8 Jurassic
The δ
34
S data for the Jurassic seawater sulfate cluster
between 14mand 18.0mwith two maxima of 23.4min
the lower Middle Jurassic (Toarcian) and 20.7min the
upper Middle Jurassic (Bathonian) (Claypool et al., 1980;
Kampschulte and Strauss, 2004; Williford et al., 2009;
Gill et al., 2011; Newton et al., 2011). The positive excur-
sion is attributed to the early Toarcian Oceanic Anoxic
Event (183 Ma) with the spread of euxinic (i.e., anoxic
and sulfidic) bottom waters and thus increases in pyrite
burial (Jenkyns, 1988; Williford et al., 2009; Jenkyns,
2010; Gill et al., 2011; Newton et al., 2011). This drastic
change coincides with the widespread extinction of ben-
thic organisms in the Northern Europe (Jenkyns, 1988).
The temporal resolution of the evaporite and CAS data
for the Toarcian and Pliensbachian is constrained on the
sub-million-year scale providing more precise information
of seawater δ
34
S variations, which could be used for stra-
tigraphy. However, for the rest of the Jurassic the overall
age uncertainty is relatively large, and more data are
required to show finer δ
34
S changes.
9.5.4.9 Cretaceous
The Cretaceous record (Fig. 9.2) derived from marine bar-
ite by Paytan et al. (2004) and DeBond et al. (2012) is a
continuous record that has a resolution of less than 1 mil-
lion years. A negative shift from B20mto 15moccurs
from 130 to 120 Ma, remaining low until 104 Ma when it
rises to B19mover 10 million years. There is a small
minimum at 88 Ma with a value of 18.3m, returning to
values of 18m19mat B80 Ma for the remainder of the
period.
These results generally agree with the CAS data from
Kampschulte and Strauss (2004). This record and the
observed fluctuations further illuminate variations that
can be seen when the finer scale not smoothed record is
available. The finer detail and the observed changes that
occur in the beginning of this period make this record
useful for stratigraphy and will be discussed later in the
chapter. Specifically, both negative excursions (130120
and 8087 Ma) occur on relatively short time scales,
likely due to the lower seawater sulfate concentration in
the Cretaceous (Horita et al., 2002), which allow for cor-
relation and can provide stratigraphic constraints.
9.5.4.10 Cenozoic
A high-resolution barite curve for the Cenozoic (Fig. 9.2)
with an age resolution of ,1 Myr shows δ
34
S values of
B19mat the Cretaceous/Paleogene boundary, which drop
precipitously to B17mat the Paleocene/Eocene
boundary (Paytan et al., 1998; Markovic et al., 2015;
Rennie et al., 2018; Yao et al., 2020). Following this min-
imum, a relatively rapid rise to B22min the Early to
Sulfur Isotope Stratigraphy Chapter | 9 269

Mid-Eocene is observed and this value is maintained until
the Pleistocene. The decrease and increase observed
between 65 and 40 Ma are useful for stratigraphic pur-
poses (see next). A distinct peak is seen at the PETM
(Yao et al., 2018) and a decrease of about 1mover the
last 2 million years is also evident as reported in
Markovic et al. (2015, 2016). In the previous barite record
the Eocene rise of seawater δ
34
S is defined by only a few
samples from Deep Sea Drilling Project Site 366 (Paytan
et al., 1998), where the biostratigraphy is not well con-
strained (Lancelot et al., 1977, 2016). In addition, the
decreasing porewater sulfate concentrations with depth,
generally higher sedimentation rates (2941.5 m/Myr),
and observable pyrite occurrences at Site 366 throughout
the middle to lower Eocene sections (3856 Ma) imply
an organic-rich and reducing environment during this
FIGURE 9.7 (A) The CAS-based sulfur isotope records across the PermianTriassic boundary at different sections from worldwide locations. (B)
Comparison of the evaporite-based and CAS-based sulfur isotope records across the PermianTriassic boundary. CAS, Carbonate-associated sulfate.
Panel (A): After Luo et al., 2010. Panel (B): After Bernasconi et al., 2017.
270 PART | II Concepts and Methods

time (Boersma and Shackleton, 1977; Lancelot et al.,
1977; Couture et al., 1977), which suggest that the barite
in that section could have been diagenetically altered.
Taking advantage of more recently retrieved cores and a
much improved biostratigraphic framework, Yao et al.
(2020) recently evaluated and refined the Eocene δ
34
S
data with a new high-resolution barite-based δ
34
S record
between 60 and 30 Ma. They showed anomalously high
87
Sr/
86
Sr ratios of Site 366 barites older than 38 Ma, indi-
cating that the local conditions at Site 366 during the
Eocene allowed for sulfate reduction and the formation of
diagenetic barite.
9.6 A database of S isotope values and
their ages for the past 130 Myr using
LOWESS regression
At this early stage of development for S isotope stratigraphy,
we can see the general trends for the record throughout the
Phanerozoic. These trends and values can be used for broad
age assignments and correlations at distinct intervals with
defined excursions (e.g., the PermianTriassic Boundary).
The goal of developing a LOWESS regression curve for S
isotopes and accompanying lookup tables is not yet realized.
Currently, the limits to developing such tables include the
availability of raw data to construct secular trends, the
unknown error associated with age assignments, and gaps in
the data sets. The potential for using LOWESS regression,
however, can be illustrated by the marine barite data sets
over the Cretaceous and Cenozoic (Fig. 9.5). The LOWESS
regression curve shown in Fig. 9.5 was produced according
to (McArthur et al., 2001).
Based on the LOWESS curve we calculated the age
resolution associated with the five age intervals that
exhibit abrupt changes in δ
34
S, 130116, 10796,
9686, 8375, 6540, and B2 Ma to the present. Age
resolutions are 0.5, 0.7, 2.6, 2.1, 1.5, and 0.9 Myr, respec-
tively, based on the data and an analytical error of 0.2m.
From this curve we also generated a preliminary lookup
table for the data set (Table 9.1).
9.7 Use of S isotopes for correlation
S isotopes have not been widely used as the sole stratigraphic
tool for dating samples. The few samples in the literature of
S isotopes used for dating and correlation all also use other
methods such as δ
13
Cand
87
Sr/
86
Sr at the same time (Walter
et al., 2000; Pokrovskii et al., 2006; Misi et al., 2007). Some
studies, particularly those focused on the Permian/Triassic
Boundary (Scholle, 1995; Kramm and Wedepohl, 1991;
Algeo, et al., 2007; Gorjan et al., 2007), use δ
13
C,
87
Sr/
86
Sr,
biostratigraphy, paleomagnetism, and other methods to corre-
late the S isotope records and use the S data to investigate
the causes and consequences of various biogeochemical
cycles across the boundary. Nevertheless, the secular and
defined trend in the S isotope record at this time interval
could be used for correlation and age determination in the
future where methods other than S isotopes are not available
or to refine age assignments based on other records.
The utility of using S isotopes for correlation between
sites is illustrated in Fig. 9.8 from Yao et al. (2018). This
study focuses on the Paleocene Eocene Thermal
Maximum at 56 Ma. Ocean Drilling Program Site 1051 is
located in the North Atlantic and does not have as distinct
a record of the Carbon Isotope Excursion in the δ
13
C
record that is typically used for correlation purposes of
FIGURE 9.8 The sulfur and carbon isotope records across the PETM.
Open and solid diamonds denote the δ
13
C data derived from bulk carbon-
ate and benthic Foraminifera from ODP Hole 1221A (Nunes and Norris,
2005). Black circles, yellow squares, and red triangles denote the barite-
based seawater δ
34
S data (1σ) from ODP Hole 1221A, 1263C, and
1265A (Yao et al., 2018). The gray envelope denotes the 95% confi-
dence interval of the LOESS regression for the total δ
34
S data. Ages and
the PETM stages (shaded boxes) as defined by Nunes and Norris (2005).
Sulfur Isotope Stratigraphy Chapter | 9 271

TABLE 9.1 Preliminary lookup
table for the data set of Fig. 9.5.
Age
(Ma)
δ
34
S
Barite
Error
(6)
0.00 20.86 0.20
0.00 21.05 0.20
0.02 20.70 0.15
0.03 20.70 0.15
0.05 20.60 0.15
0.07 20.70 0.15
0.08 20.80 0.20
0.08 20.80 0.15
0.12 21.04 0.20
0.16 20.70 0.15
0.17 20.80 0.15
0.18 21.00 0.15
0.19 20.90 0.15
0.20 20.98 0.20
0.24 21.21 0.20
0.24 21.10 0.15
0.30 20.90 0.15
0.31 20.81 0.20
0.38 20.80 0.15
0.39 21.00 0.20
0.40 20.90 0.20
0.42 21.10 0.15
0.48 20.93 0.18
0.53 21.10 0.15
0.61 21.00 0.15
0.61 20.86 0.20
0.62 20.90 0.15
0.66 20.90 0.15
0.66 20.90 0.15
0.68 21.14 0.20
0.69 20.85 0.15
0.69 20.90 0.15
0.71 21.00 0.15
0.72 21.10 0.15
0.74 20.90 0.15
0.76 21.22 0.20
(Continued )
TABLE 9.1 (Continued)
Age
(Ma)
δ
34
S
Barite
Error
(6)
0.76 21.08 0.20
0.77 21.10 0.15
0.78 21.10 0.15
0.79 21.20 0.15
0.81 21.30 0.15
0.82 21.30 0.15
0.83 21.30 0.15
0.85 21.40 0.15
0.91 21.34 0.20
0.92 21.30 0.15
0.92 21.20 0.15
0.96 21.20 0.15
0.98 21.20 0.15
1.03 21.35 0.20
1.12 21.30 0.15
1.14 21.10 0.20
1.16 21.40 0.15
1.21 21.45 0.20
1.37 21.80 0.15
1.40 21.70 0.15
1.55 21.80 0.15
1.58 21.80 0.15
1.61 21.80 0.15
1.71 21.80 0.20
1.75 22.00 0.15
1.80 21.80 0.15
1.93 21.80 0.15
1.94 22.05 0.20
1.95 21.90 0.15
2.01 21.90 0.20
2.02 22.10 0.15
2.10 22.00 0.15
2.14 21.90 0.15
2.26 21.90 0.15
2.28 22.02 0.20
2.34 22.00 0.15
2.54 21.80 0.20
(Continued )
TABLE 9.1 (Continued)
Age
(Ma)
δ
34
S
Barite
Error
(6)
2.74 22.10 0.15
2.98 21.90 0.15
3.05 21.67 0.20
3.09 21.85 0.20
3.30 21.50 0.20
3.50 21.90 0.20
3.58 21.51 0.20
3.65 21.95 0.20
3.72 21.70 0.20
3.83 21.90 0.20
4.02 21.77 0.20
4.55 22.04 0.20
4.85 21.94 0.20
5.40 21.93 0.20
5.74 21.96 0.20
5.90 21.63 0.20
6.23 22.26 0.20
6.68 22.32 0.20
7.64 21.86 0.20
7.85 22.37 0.20
9.00 21.80 0.20
9.50 22.10 0.20
10.10 21.90 0.20
11.17 22.17 0.20
12.40 22.10 0.20
12.49 21.96 0.20
12.50 21.90 0.20
12.54 22.71 0.20
12.60 21.98 0.24
12.77 22.70 0.20
12.78 22.30 0.20
13.00 22.35 0.22
13.27 22.04 0.20
13.72 22.06 0.20
14.05 21.75 0.22
14.95 22.10 0.20
14.98 21.87 0.20
(Continued )
272 PART | II Concepts and Methods

TABLE 9.1 (Continued)
Age
(Ma)
δ
34
S
Barite
Error
(6)
16.20 21.88 0.16
17.04 22.09 0.20
18.13 21.83 0.23
19.00 21.80 0.20
20.14 21.64 0.20
21.08 22.01 0.20
22.20 22.00 0.28
23.47 21.89 0.22
23.97 21.81 0.20
24.36 21.64 0.20
24.52 21.48 0.16
25.26 21.66 0.20
25.83 21.70 0.17
27.68 21.27 0.22
28.38 21.44 0.20
29.61 21.20 0.18
30.50 21.39 0.24
30.60 21.83 0.19
31.48 21.17 0.12
32.30 21.52 0.20
33.44 21.32 0.21
33.49 21.39 0.28
33.58 21.99 0.11
33.90 21.57 0.16
33.92 22.00 0.11
34.00 20.33 0.20
34.10 21.40 0.20
34.39 22.74 0.20
34.44 22.25 0.20
34.49 21.50 0.23
34.93 22.29 0.17
35.02 22.40 0.20
35.10 21.23 0.28
35.17 22.16 0.11
35.37 22.02 0.20
35.49 22.26 0.20
35.76 22.14 0.21
(Continued )
TABLE 9.1 (Continued)
Age
(Ma)
δ
34
S
Barite
Error
(6)
35.95 22.05 0.18
35.96 22.39 0.11
36.05 21.60 0.20
36.25 22.52 0.18
36.37 22.03 0.16
36.72 21.78 0.11
36.95 22.17 0.20
37.33 22.31 0.16
37.42 22.14 0.16
37.46 21.52 0.16
37.94 22.36 0.16
38.23 22.32 0.16
38.32 22.20 0.16
38.39 22.36 0.15
38.59 22.51 0.16
38.88 22.00 0.21
38.96 22.37 0.16
39.24 21.91 0.15
39.36 21.98 0.16
39.37 22.36 0.20
39.55 21.80 0.20
40.12 21.71 0.15
40.83 22.19 0.20
40.87 20.94 0.20
40.95 22.39 0.15
41.41 21.66 0.21
41.46 21.47 0.21
41.83 21.38 0.16
42.42 22.49 0.20
43.10 20.25 0.20
43.52 20.50 0.20
44.30 21.48 0.20
44.42 19.73 0.20
44.81 21.30 0.20
45.58 19.23 0.20
45.60 21.33 0.20
45.80 19.24 0.16
(Continued )
TABLE 9.1 (Continued)
Age
(Ma)
δ
34
S
Barite
Error
(6)
46.08 19.74 0.11
46.16 19.69 0.20
46.28 19.61 0.20
46.42 19.49 0.16
46.51 19.74 0.18
46.58 19.09 0.20
46.61 19.37 0.20
46.68 19.06 0.16
46.81 19.36 0.16
46.96 18.71 0.21
47.18 19.05 0.20
47.48 19.11 0.20
47.49 18.67 0.15
47.96 18.06 0.21
48.37 18.53 0.21
48.79 19.58 0.21
48.85 19.96 0.16
49.09 18.17 0.20
49.20 19.40 0.20
49.91 19.31 0.20
49.97 17.83 0.21
50.20 18.97 0.21
50.39 16.72 0.15
50.76 18.12 0.16
50.97 18.08 0.20
51.02 16.95 0.21
51.66 16.57 0.21
52.13 17.95 0.14
52.14 17.30 0.21
52.60 16.35 0.21
52.61 17.15 0.11
52.92 17.42 0.17
53.14 16.77 0.21
53.26 17.58 0.15
53.33 17.40 0.21
53.37 17.45 0.11
53.54 16.86 0.11
(Continued )
Sulfur Isotope Stratigraphy Chapter | 9 273

TABLE 9.1 (Continued)
Age
(Ma)
δ
34
S
Barite
Error
(6)
53.78 17.21 0.21
53.90 17.68 0.11
53.96 17.50 0.21
54.13 16.90 0.11
54.19 16.90 0.20
54.67 16.08 0.11
54.98 17.11 0.21
55.03 17.52 0.11
55.05 17.78 0.11
55.05 17.70 0.11
55.05 17.63 0.21
55.07 17.74 0.14
55.07 17.41 0.14
55.08 17.54 0.11
55.08 17.89 0.14
55.09 17.83 0.21
55.09 17.04 0.21
55.10 17.75 0.21
55.11 17.53 0.21
55.11 17.49 0.11
55.12 17.76 0.21
55.13 17.84 0.21
55.13 17.66 0.21
55.14 17.31 0.21
55.14 17.42 0.22
55.15 17.60 0.11
55.15 17.52 0.21
55.16 17.38 0.21
55.16 17.75 0.21
55.17 17.78 0.21
55.17 17.60 0.21
55.18 17.59 0.21
55.18 17.80 0.21
55.18 17.60 0.21
55.18 17.67 0.21
55.21 18.09 0.21
55.21 16.75 0.20
(Continued )
TABLE 9.1 (Continued)
Age
(Ma)
δ
34
S
Barite
Error
(6)
55.21 17.88 0.21
55.21 18.25 0.11
55.22 18.58 0.11
55.22 17.90 0.11
55.22 18.31 0.21
55.22 17.95 0.21
55.23 18.19 0.21
55.23 18.95 0.11
55.24 17.77 0.11
55.24 17.54 0.11
55.24 17.78 0.11
55.25 17.71 0.22
55.25 17.51 0.20
55.25 17.64 0.20
55.26 17.87 0.20
55.26 17.66 0.21
55.26 17.50 0.20
55.26 17.62 0.15
55.27 17.75 0.16
55.27 17.68 0.20
55.27 17.49 0.21
55.28 17.89 0.20
55.28 17.36 0.20
55.28 17.53 0.20
55.29 17.56 0.15
55.29 17.21 0.20
55.30 17.66 0.20
55.31 17.77 0.16
55.31 17.45 0.16
55.32 17.49 0.16
55.33 17.26 0.20
55.42 17.63 0.20
55.47 17.42 0.20
55.52 17.19 0.20
55.72 17.34 0.20
55.81 18.05 0.20
55.84 16.99 0.20
(Continued )
TABLE 9.1 (Continued)
Age
(Ma)
δ
34
S
Barite
Error
(6)
55.97 17.24 0.20
56.13 17.23 0.20
56.22 17.53 0.20
56.38 16.94 0.20
56.44 17.60 0.20
56.54 17.72 0.20
56.76 18.07 0.20
56.92 17.44 0.20
57.22 17.60 0.20
57.92 17.99 0.20
57.95 17.42 0.20
58.03 18.28 0.20
58.09 17.10 0.20
58.45 17.13 0.20
59.09 17.76 0.20
59.36 17.99 0.20
59.64 18.12 0.20
62.26 18.63 0.20
62.46 19.04 0.20
62.55 19.05 0.20
62.56 19.37 0.20
63.91 19.38 0.20
64.06 19.00 0.20
64.26 18.96 0.20
64.37 19.04 0.20
64.62 19.00 0.20
64.74 19.14 0.20
64.80 18.93 0.20
65.02 19.30 0.20
65.21 18.95 0.30
65.27 18.94 0.30
65.57 19.11 0.30
66.06 18.76 0.30
66.80 18.80 0.30
68.72 18.88 0.27
70.08 18.82 0.30
71.40 19.09 0.30
(Continued )
274 PART | II Concepts and Methods

this time interval making it difficult to correlate to other
sites such as Site 1267 in the South Atlantic. At both
Sites, however, a minimum in the δ
34
S record was
recorded and used to align the two records. Ages were
determined by biostratigraphy.
S isotopes data are becoming more widely available
for many study locations and, as illustrated previously,
have the potential to become a more useful tool for stra-
tigraphy and correlation as we refine the global S isotope
record. The challenge in the next few years is to expand
the data available to produce a reliable, high-resolution,
secular data of seawater S isotope values set such that a
high-resolution curve like the one currently available for
the past 130 Ma could be produced and used for age
determination.
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TABLE 9.1 (Continued)
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110.15 15.35 0.23
(Continued )
TABLE 9.1 (Continued)
Age
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δ
34
S
Barite
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111.68 16.33 0.30
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113.26 15.35 0.30
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115.05 15.79 0.27
115.23 15.34 0.30
115.36 15.30 0.25
117.27 15.32 0.23
117.39 16.40 0.30
117.52 16.55 0.25
117.82 18.70 0.30
117.95 17.83 0.30
119.25 19.21 0.27
120.60 19.56 0.25
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124.65 20.05 0.25
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