PALEOCEANOGRAPHY,
VOL. 11,
11,NO.
NO.6,
PAGES 665-678,
665-678, DECEMBER
DECEMBER 1996
PALEOCEANOGRAPHY, VOL.
6, PAGES
1996
Vanadium
in foraminiferal
calcite as
as aa tracer
Vanadium in
foraminiferal calcite
tracer for
for changes
changes
in
in the
the area!
areal extent
extent of
ofreducing
reducingsediments
sediments
11and
and Steven
Steven R.
David
DavidW.
W. Hastings
R.Emerson
Emerson
School of
of Oceanography,
University
Seattle
School
Oceanography,
Universityof
of Washington,
Washington,
Seattle
Alan
Alan C.
C. Mix
Mix
College
Oregon
Collegeof
of Oceanography,
Oceanography,
OregonState
StateUniversity,
University,Corvallis
Corvallis
Abstract.
a tracer
tracer
Abstract. We
Wehave
haveused
usedthe
thevanadium
vanadium concentration
concentration in
in cleaned
cleaned foraminiferal
foraminiferal calcite
calcite as a
of
seawater
V
changes
in
the
past.
Since
the
benthic
flux
of
vanadium
is
sensitive
to
the
redox
poof seawaterV changesin thepast.Sincethebenthicflux of vanadiumis sensitiveto theredoxpotential of
changes
concentration of
of seawater
seawater should
should be
be aa reflection
reflection of
of
tential
of sediments,
sediments,
changesin
in the
the vanadium
vanadiumconcentration
changes
V/Ca in'G.
in G. sacculifer
sacculifer from
from an
an eastern
eastern equatorial
equatorial
changesthat
thatcontrol
controlthe
theredox
redoxstate
stateof
of sediments.
sediments.
V/Ca
Atlantic
17GGC) is
Atlanticcore
core(EN066(ENO66-17GGC)
is 21.6
21.6 (±2.8)
(+_2.8)nmol
nmolV/mol
V/mol Ca.
Ca. This
Thisvalue
valuedoes
doesnot
notchange
changeover
over
35
change
levels over
this
35 kyr,
kyr, indicating
indicatingthat
thatthere
therewas
wasno
nomeasurable
measurable
changein
in seawater
seawatervanadium
vanadiumlevels
overthis
period. Potential
partial dissolution
dissolution are
are not
not significant
significant based
based on
on low,
low, constant
constant values
values
period.
Potentialartifacts
artifactsfrom
from partial
for foraminiferal
(6-7%)
minor correction
for
foraminiferalfragmentation
fragmentation
(6-7%) in
in the
thetop
top50
50 cm
cmof
of the
thecore.
core:A
A.minor
correctionto
toaccount
account
for
with
overgrowths,
estimated
for vanadium
vanadiumassociated
associated
with Mn
Mn carbonate
carbonate
overgrowths,
estimatedfrom
fromtwo
two Caribbean
Caribbeancores
cores
where
this
mixed
phase
dominates
the
deeper
V/Ca
values,
has
been
applied.
Changes
in the
the areal
areal
wherethismixedphasedominates
thedeeper
V/CaValues,
-hasbeenapplied.
Changes
in
extent of
sediments
are
by
value
extent
of anoxic
anoxicand
andsuboxic
suboxic
sediments
arethus
thusconstrained
constrained
bythis
thisconstant
constant
valueand
andthe
thestandard
standard
deviation of
deviation
of the
the measurement,
measurement,±12%.
+_12%.Based
Based on
on aa mass
massbalance
balance for
for vanadium
vanadium where
where suboxic
suboxic sedisediments are
are
are
to
ments
areaa source
sourceand
andanoxic
anoxicsediments
sediments
areaa sink
sinkto
to the
theocean,
ocean'suboxic
suboxicsediments
sediments
arepredicted
predicted
to
have
changed
by
no
more
than
0.5-1.5
times
the
current
value,
assuming
no
change
in
the
areal
havechanged
by nomorethan0.5-1.5timesthecurrent
value,assuming
nochangeintheareal
extent of
of anoxic
anoxic sediments.
This correspondsto
corresponds to 1.3-3.5%
sediments.
Given a
a conconextent
sediments.
This
1.3-3.5%of
oftotal
totalocean
ocean
Sediments.
Given
stant area
area of
of suboxic
sediments,
the areal
areal extentof
extent-of anoXic
anoxic Sediments
sediments didonot
did notincrease
increase by
by more
more than
than
stant
suboxic
sediments,
the
fivefold, or
of
floor
over
the
35
reductions in
in deep
water
fivefold,
or1.5%
1.5%
ofthe
theocean
ocean
floor
over
thepast
past
35kyr.
kyr.The
Thesignificant
significant
reductions
deep
water
oxygen levels
levels and
changes
in
conditions
required
by
deoxygen
andconsequent
consequent
changes
insediment
sedimen
t redox
redox
conditions
required
bypolar
polarnutrient
nutrient
depletion
are
data over
over the
the past
past 35
35 kyr.
kyr. This
This
pletionscenarios
scenarios
arenot
notreflected
reflectedin
in the
theforaniiniferal
foraminiferalvanadium
vanadiumdata
suggests that
that models
which
call
in
water
oxygen
are
suggests
models
which
callon
onless
lessor
orno
nochanges
changes
indeep
deep
Water
oxygen
aremore
morelikely
likely
alternatives.
alternatives.
Introduction
Introduction
One
geochemical
One class
classof
of coupled
coupledocean-atmosphere
ocean-atmosphere
geochemicalmodels
models
developed
to
explain
the
reduced
glacial
age
pCO2
developed
to explainthereducedglacialageatmospheric
atmospheric
pCO2
[Barnola et
et al.,
[Barnola
el., 1987;
1987; Jouzel
Jouzel et
et al.,
el., 1993]
1993] relies
relies on
on more
more effieffi:
cient
cient utilization
utilization of
of nutrients
nutrientsin
inhigh-latitude
high-latitudesurface
surfacewaters
waters
[Knox and
and McElroy,
McElroy, 1984;
Sarmiento and
and Toggweiler,
[Knox
1984; SarmientO
Toggweiler,1984;
1984;
Siegenthaler
and
Wenk,
1984;
Martin
et
al.,
Siegenthalerand Wenk, 1984; Martin et el., 1990].
1990]. A
A conseconsequence
quenceof
of these
thesemodels
modelsis
is that
thatthe
theincreased
increasedexport
exportof
of organic
organic
matter
remineralization
matter to
to the
thedeep
deepocean
oceanand
andsubsequent
subsequent
remineralizationrere'
sults in
in aa large
sults
largedepletion
depletionin
in deep
deepwater
wateroxygen
oxygenduring
duringglacial
glacial
periods.
periods.A
A three-dimensional
three-dimensionalocean
ocean circulation
circulation model
model of
of the
the
Reimer, 1994]
which predict
predict less
less or
Reimer,
1994] which
or no
nooxygen
oxygendepletion
depletiondurduring glacial
_ing
glacialtimes.
times.The
Thediverse
diversemodeling
modelingefforts
effortstherefore
thereforeprepredict
the last
dictdifferent
differentdeep
deepwater
wateroxygen
oxygenlevels
levelsduring
duringthe
lastglacial
glacial
maximum.
Which approach
maximum, Which
approachis
is valid?
valid?
Several
proxies exist
exist to
Several proxies
to assess
assesschanges
changesin
in sediment
sedimentredox
redox
conditions
these
conditionsin order
orderto
to evaluate
evaluateand
andconstrain
constrain
thesedifferent
different
models.
The most
indicator
for
water
m0dels.'
The
mostunambiguous
unambiguous
indicator
forbottom
bottom
water
anoxia
is the existence of laminated
anoxia is
laminated sediments
sediments and the absence
absence
Based on
on the
of
of benthic
benthicforamimfera.
foraminifera.Based
theexistence
existence
of benthic
benthic
fauna in
in most
most sediment
cores, itit is
is safe
fauna
sediment cores,
safe to
to rule
rule out
out vast
vast areas
areas of
of
ocean anoxia
anoxia for
for at
years.
ocean
at least
leastthe
thelast
lastten
tenor
ortwenty
twentythousand
thousand
years.
Evidence of
of decreased
decreased bottom
bottom water
water oxygen
oxygen has
has been
been evaluated
evaluated
Evidence
carbon
and Orr,
carboncycle
cycle [Sarmiento
[Sarrnientoand
Orr, 1991]
1991]predicts
predictsaa decrease
decreasein
in
by
determination
of
trace
metal
enrichment
in
sediments
[e.g.,
bydetermination
oftrace
metal
enrichment
insediments
[e.g,,
average deep
deep water
average
water oxygen
oxygen by
by 40
40 LtM,
!.tM, with
with bottom
bottom water
water'
Dean,
Dean, 1989;
1989; Calvert
Calvert and
and Pedersen,
Pealersen,1993;
1993; Sarkar
Sarkar et
et al.,
el., 1993;
1993;
anoxia
resulting
in
the
southwestern
Indian
Ocean.
Other
modanoxiaresultingin the southwestern
Indian Ocean,Other modColodner et
er el.
al.,' 1994;
Piper and
and Issacs,
1995;
Rosenthal et
et
ColOdner
1994;Piper
Issacs,
1995;Rosenthal
eling efforts to explain reduced pCO2 during the last glacial
al.,
1995;
Yang
er
al.,
1995;
Crusius
et
al.,
1996]
and
faunal
eling
efforts
reduced
pCO2
during
lastglacial
el.,1995;
Yang
etel.,1995'
Crusius
etel.,1996]
andfaunal
age are
are
basedto
onexplain
alkalinity
changes
in the
the
oceanthe
[Broecker
and
age
based
on
alkalinity changes
in
ocean
[BrOecker
and
.
indices
such as
as the
the number
indices
such
numberof
of fecal
fecal pellets
pelletsand
and size
sizeand
andabunabunPeng,
1989;
Opdyke
and
Walker,
1992;
Archer
and
MaierPeng, 1989; Opdyke and Walker, 1992; Archer and Maierdance
[Pedersen
er
dance of
of benthic
benthicforaminifera
foraminifera
[Pedersen
et al.,
al., 1988].
1988].These
These
indicators
are limited
indicatorsare
limitedin
in that
thatthey
theyreflect
reflectlocal
localdepositional
depositional
conditions
primarily
in
equatorial
upwelling
areas. The
The record
record
1Now
at
Department
of
Earth
and
Ocean
Sciences
University
of
primarilyin equatorial
upwelling
areas.
1Nowat Department
of EarthandOceanSciences
University
of conditions
Biitish
can
British Columbia,
Columbia, Vancouver,
Vancouver, Canada.
Canada.
can easily
easily be
be disturbed
disturbedby
byphysical
physicalerosion,
erosion,chemical
chemicalalteralteration,
and
bioturbation
ifif overlain
by
oxygenated
sediments
ation,
and
bioturbation
overlain
by
oxygenated
sediments
Copyright
Union.
Copyright1996
1996by
by the
theAmerican
AmericanGeophysical
Geophysical
Union.
[Thomson et al.,
al., 19951.
Using these
these approaches,
it would
be
[Thomsonet
1995]..
Using
approaches,
it
would
be
necessary
comprehensively
in
necessaryto
to sample
sampleocean
oceansediments
sediments
comprehensively
in
order
order to
to evaluate
evaluateglobal
global changes
changesin
in the
the extent
extentof
of sediments
sediments
Paper number
Paper
number96PA01985.
96PA01985.
0883-8305/96/96PA-01985512.00
0883-8305/96/96PA-01985$l2.00
665
665
666
666
HASTINGS ET
F AL.:
HASTINGS
AL.:VANADIUM
VANADI•,'I IN
INFORAMINIFERAL
FORAMINIFERAL CALCITE
CAI.121•
overlain
by anoxic
water. Since
Since the
the areal
overlain by
anoxic bottom
bottom water.
areal extent
extent of
of
anoxic
is presently
very small,
anoxic sediments
sedimentsis
presentlyvery
small, about
about 0.3%
0.3% of
of the
the
derived Fe
are highly
of
derived
Fe oxyhydroxides
oxyhydroxides
are
highlyefficient
efficientscavengers
scavengers
of
oxyanions
such
and
for
60
oxyanions
suchas
asvanadium
vanadium
andcan
canaccount
account
forremoving
removing
60
ocean floor,
increase
would
±
ocean
floor,an
anorder
orderof
of magnitude
magnitude
increase
wouldbe
beonly
only3%
3%
_+30%
30% of
of the
theriverine
rivefineinput
input[Trefry
[Trefryand
andMetz,
Metz,1989;
1989;Kadko,
Kadko,
of the sediment
of
sediment surface. Such
Such an
an increase
increase would
would be
be difficult
difficult to
to
1993;
Rudnicki and
and Elderfield,
time
1993;Rudnicki
Elderfield,1993].
1993].The
Theresidence
residence
timeof
of V
V
detect. Another
with
detect.
Another approach
approachwhich
which reflects
reflectsglobal
global changes
changesis
is
with respect
respectto
to riverine
rivefineinput
inputis
is 100
100kyr
kyr[Shiller
[Shillerand
andBoyle,
Boyle,
based on
between
31 8 of
oxygen
1987].
based
onthe
thedifference
difference
between/5180
of atmospheric
atmospheric
oxygen 1987].
and seawater
(the Dole
Especially
relevant to
to this
this work
and
seawater (the
Dole effect)
effect) as
as recorded
recorded in
in the
the Vostok
Vostok ice
ice
Especially relevant
work is
is that
that several
several data
data sets
sets
core over
over the
the past
past 130
from
sediments
off
of
Africa
core
130 kyr
kyr [Bender,
[Bender, 1994].
1994]. Since
Since the
the Dole
Dole
fromreducing
reducing
sediments
off the
thecoast
coast
ofnorthwest
northwest
Africasugsugeffect
on
timescale,
out of
of
effectis
isnearly
nearlyunchanged
unchanged
onaaglacial-interglacial
glacial-interglacial
timescale, gest
gestthat
that there
thereis
is aa significant
significantbenthic
benthicflux
flux of
of vanadium
vanadiumout
the
authors
conclude
that
there
cannot
have
been
major
suboxic
sediments,
where
Mn
is
also
diffusing
into
overlying
the authors concludethat there cannot have been major
suboxicsediments,
whereMn is alsodiffusinginto overlying
changes
bottom waters
changesin
in global
globalmarine
marineproductivity
productivityand
andhence
henceminimal
minimal
bottom
waters[Seralarhan
[Seralathanand
andHartmann,
Hartmann,1986;
1986;Legeleux
Legeleuxet
et
excursions
excursions in
in oxic
oxic versus
versus suboxic
suboxic or
or anoxic
anoxic sedimentation.
sedimentation.
al.,
al., 1994;
1994; Hastings
Hastingsand
andEmerson,
Emerson,1995].
1995]. This
Thisisisconsistent
consistent
In
tracer
with the
V is
In this
thiswork
workwe
wedevelop
developaanew
newpaleoceanographic
paleoceanographic
tracerfor
for
with
the observation
observationthat
that in
in hemipelagic
hemipelagicsediments,
sediments,V
is
changes
in
redox
on
using
coupled
with
the
redox
cycle
of
Mn.
In
suboxic
sedichanges
in sediment
sediment
redoxconditions
conditions
onaaglobal
globalscale
scale
using tightly
tightly coupledwith the redox cycle of Mn. In suboxicsedivanadium
in foraminiferal
ments,
defined in
in this
vanadiumincorporation
incorporationin
foraminiferalcalcite
calciteas
asan
anindicator
indicator
ments,operationally
operationally
defined
thiswork
workas
asthose
thosewhere
wherepore
pore
of
in
The
of
of past
pastV
V concentrations
concentrations
in the
theocean.
ocean.
Thepotential
potential
ofusing
using water
wateroxygen
oxygenis
is depleted
depletedwithin
withinthe
theupper
upper1-3
1-3cm,
cm,and
andwhere
where
forarniniferal
vanadium as
proxy
foraminiferalvanadium
asaapaleoceanographic
paleoceanographic
proxyfor
forseasea- no
no surficial
surficial enrichment
enrichmentof
of Mn
Mn oxides
oxidesisisobserved,
observed,lower
lowerbulk
bulk
water
has
concentrations
imply
a
diffusive
flux
of
vanadium
watervanadium
vanadiumconcentrations
concentrations
hasrecently
recentlybeen
beendemonstrated
demonstrated V
V concentrationsimply a diffusive flux of vanadiuminto
into the
the
[Hastings
culture
show
yr1. The
[Hastingset
et al.,
al., 1996a].
1996a].Laboratory
Laboratory
cultureexperiments
experiments
show overlying
overlyingbottom
bottomwaters
watersof
of about
about66 nmol
nmolcm-2
cm-2yr-1.
Theareal
areal
that
extent
that living
living planktonic
planktonicand
andshallow
shallowwater
waterbenthic
benthicforaminifera
foraminifera
extent of these
these suboxic
suboxic sediments
sediments is estimated
estimated to be 2.5%
2.5% of
incorporate
vanadium
into
their
tests
in
direct
to
ocean
based
that
incorporatevanadiuminto their testsin directproportion
proportion
to
oceansediments
sediments
basedon
onsediments
sediments
thathave
havean
anoverlying
overlying
seawater
concentrations. V/Ca
V/Ca values
values for
for the
the same
of
productivity
greater than
than 200 g C
not
seawaterconcentrations.
samespecies
speciesof
productivity
greater
C rn-2
m-2yr1
yr-1atatdepths
depths
notexexforaminifera
in different
for
foraminifera
in
differentocean
oceanbasins
basinsare
areconstant
constant
forcore-top
core-top ceeding
ceeding1500
1500rn.
m. The
The depth
depthand
andproductivity
productivitycriteria
criteriaare
arebased
based
samples
on those
there is
is a diffusive
samplescollected
collectedabove
abovethe
theforaminiferal
foraminiferallysocline
lysoclinein
in differdifferthose sediments
sediments where there
diffusive flux
flux of V out
out of
of
ent
ent ocean
oceanbasins.
basins.The
The mean
meancore-top
core-topvalues
valuesare
are 21.7
21.7 (±
(+ 3.6;
3.6;
n=15) and
n=15)
and112
112 (±9;
(+9; n=3)
n=3) nmol
nmolV/mol
V/mol Ca
Ca for
for Globigerinoides
Globigerinoides
sacculifer and
wuellerstorfi,
Coresacculifer
andCibicidoides
Cibicidoides
wuellerstorfi,respectively.
respectively.
Core-
the
the sediments.
sediments. Other
Other estimates
estimates of
of suboxic
suboxic sediments
sediments are
are
higher,
higher, ranging
ranging from
from 8
8 to
to 13%
13% [Klinkhammer
[Klinkhammer and
and Palmer,
Palmer,
1991;
Reimers et
et al.,
al., 1992],
using
1991;Reimers
1992],but
butare
areevaluated
evaluated
usingdifferent
different
criteria. Based
Based on
on the
theestimate
estimatethat
thatsuch
suchsuboxic
suboxicsediments
sedimentsacaccount
count for
for 2.5%
2.5% of
of ocean
oceansediments,
sediments,the
the V
V flux
flux is
isestimated
estimatedto
to
partial dissolution
of the
depth
to
examipartial
dissolution
of
thetests.
tests.With
Withincreasing
increasing
depthof
ofdepodepo- be
beequivalent
equivalent
to45%
45%of
ofthe
theriverine
rivefineinput.
input.An
Anin-depth
in-depth
examisition, more corrosive
nation
corrosive bottom waters,
waters, and
and thus
thus more
more extensive
extensive
nation of
of the
the marine
marine mass
massbalance
balance for
for vanadium
vanadium and
andassociated
associated
partial
dissolution
of
the
test,
V/Ca
increases
by
[D.
et
in
partialdissolution
of the test,V/Ca increases
by up
upto
to aafactor
factor data
datasets
setsis
isgiven
givenelsewhere
elsewhere
[D. Hastings
Hastings
etal.,
al.,manuscript
manuscript
in
of
4
in
G.
sacculifer
and
by
a
factor
of
2
in
C.
wuellerstorfi.
preparation,
1996].
Assuming
that
other
terms
in
the
oceanic
of 4 in G. sacculiferandby a factorof 2 in C. wuellerstorfi. preparation,1996]. Assumingthat other termsin the oceanic
This
effect
V
over
in
This dissolution
dissolution
effectcan
canbe
beminimized
minimizedby
bycareful
carefulchoice
choiceof
of
V cycle
cycleare
areconstant
constant
overthe
thepast
pastglacial
glacialperiod,
period,changes
changes
in
study
to
the vanadium
concentration
in
should
reflect
studymaterial
materialfrom
fromdepths
depthsshallow
shallowenough
enough
toavoid
avoidsignifisignifi- the
vanadium
concentration
in seawater
seawater
should
reflectchanges
changes
cant
By
that
in the redox state
state of
of the
the surface
surface sediments.
sediments.
cantcalcite
calcitedissolution.
dissolution.
Bydemonstrating
demonstrating
thatincorporation
incorporation in
of vanadium
is
to
of
vanadiumin
in cultured
culturedforaminifera
foraminifera
isdirectly
directlyproportional
proportional
to
seawater
concentrations and
and that
Methods
seawaterconcentrations
that global
globalcore-top
core-topV/Ca
V/Ca values
values Methods
above
the
foraminiferal
lysocline
are
constant,
we
abovethe foraminiferallysoclineare constant,we have
haveshown
shown
Foraminifera were
were obtained
by washing
that
vanadium is
is a
a valuable
Foraminifera
obtainedby
washingand
andsieving
sieving(>63
(>63
thatforaminiferal
foraminiferalvanadium
valuabletool
tool to
to reveal
revealpast
past
J.tm)
bulk
ocean
sediment
several
times
in
5%
changes
in
the
vanadium
levels
in
seawater.
In
this
paper
we
gm) bulk oceansediment
severaltimesin 5%(NaPO3)6
(NaPO3)
6
changesin the vanadiumlevelsin seawater.
In thispaperwe
buffered
pH 88 with
bufferedto
to pH
withNaOH
NaOHto
toremove
removeclays
claysand
andfines.
fines.After
After
examine
the downcore
V/Ca record
changes
examinethe
downcoreV/Ca
recordto
to constrain
constrain
changesin
in
was
(<250,
drying,the
thesediment
sediment
wassieved
sievedinto
intofive
fivesize
sizefractions
fractions
(<250,
seawater
V over
seawaterV
over the
the past
past35
35 kyr,
kyr,which
whichin
inturn
turnprovides
provides drying,
250-355,
information
regarding changes
changes in
in the
250-355, 355-425,
355-425,425-495,
425-495,and
and>495
>495J.Lm),
gm), and
andsingle
single
informationregarding
the redox
redoxstate
stateof
of marine
marine
species
of
were
under
sediments.
sediments.
species
of foraminifera
foraminifera
werehand-picked
hand-picked
underaadissecting
dissecting
microscope
from the
the 355
tm fraction.
microscopefrom
355 to
to 425
425 gm
fraction.Those
Those
individuals
visibly
contaminated
by
black
specks,
assumed
to
individuals
visibly
contaminated
by
black
specks,
assumed
to
The
Marine
Vanadium
Cycle
The Marine Vanadium Cycle
top analyses
analyses along
along two
rises across
the
top
two submarine
submarine rises
across the
foraminiferal lysocline
lysocline indicate
indicate aa significant
foraminiferal
significanteffect
effectrelated
relatedto
to
Vanadium
is aa useful
the flux
Vanadium is
useful tracer
tracer because
because the
flux to
to and
and from
from
ocean sediments
is sensitive
to the
ocean
sediments is
sensitive to
the redox
redox state
state of
of bottom
bottom
water. Since
water.
Sincethe
the vanadium
vanadiumconcentration
concentrationis
is nearly
nearlyconservaconservative throughout
the world
tive
throughoutthe
world ocean
ocean[Collier,
[Collier, 1984],
1984], aa single
singlepapaleoceanographic record
record is
is sufficient
sufficient to
to provide
leoceanographic
provideaa global
globalestiestimate of
of changes
The
mate
changesin
in the
theareal
arealextent
extentof
ofreducing
reducingsediments.
sediments.
The
major source
source of
of dissolved
to the
major
dissolved vanadium
vanadium to
the ocean
ocean is
is riverine
rivefine
input, which
which accounts
accounts for
for aa global
global flux
flux of
of 55 xx 108
mol V
V yr-1
yr1
input,
108mol
[Shiller and
and Boyle,
It is
[Shiller
Boyle, 1987].
1987]. It
is well
well established
establishedthat
thatanoxic
anoxic
sediments, defined
defined here
here as
sediments,
as those
thoseoverlain
overlainby
by anoxic
anoxicbottom
bottom
water,
are
a
known
sink
for
vanadium
[Holland,
water, are a known sink for vanadium [Holland, 1984;
1984; Breit
Breit
and
responsible for
for removing
removing88 +± 5%
5% of
of the
and Wanty,
Wanty,1991]
1991] responsible
the
riverine
riverineinput
input[Emerson
[Emersonand
andHuesred,
Huested,1991].
1991].Hydrothermally
Hydrothermally
be ferromanganese
ferromanganeseoxide, were not
not used.
used.Foraminifera
Foraminiferawere
were
gently crushed
to
chambers
and
gently
crushed
toopen
openthe
theindividual
individual
chambers
andrigorously
rigorously
cleaned
modified
from
cleanedusing
usingaamethod
method
modified
fromBoyle
Boyleand
andKeigwin
Keigwin
[1985/86] to
to eliminate
these
phases.
Two
cleaning
[1985/86]
eliminate
these
phases.
Tworeductive
reductive
cleaning
steps
before
step
Following
steps
beforeand
andafter
afterthe
theoxidative
oxidative
stepwere
wereused.
used.
Following
the
procedure,
all
was
in a
a
thecleaning
cleaning
procedure,
all sample
samplehandling
handling
wasperformed
performed
in
HEPA
laminar flow
flow hood
hood in
in aa class
HEPA laminar
class100
100 clean
cleanroom.
room.A
A comcom-
plete description
of the
is
plete
description
of
thecleaning
cleaningprocedure
procedure
is given
givenby
by
Hastings et
Hastings
et al.
al. [1996a].
[1996a].
Cleaned samples
were
gravimetrically
spiked
Cleaned
samples
weredissolved,
dissolved,
gravimetrically
spiked
with an
an 50V
isotope spike
spike enriched
enriched to
to 44
with
50Visotope
44 atom
atom%,
%,and
andtaken
takento
to
dryness.
Dried
were
eluted
through
cation
dryness.
Driedsamples
samples
wereredissolved,
redissolved,
eluted
through
cation
exchange
interferences,
and
exchangeresin
resinto
to remove
removeCa
Caand
andisobaric
isobaric
interferences,
and
analyzed
analyzedfor
for V
V by
byisotope
isotopedilution
dilutionthermal
thermalionization
ionizationmass
mass
667
667
HASTINGS
Fr AL.:
CALCITE
HASTINGSET
AL.:VANADIUM
VANADIUMIN
INFORAMINTFERAL
FORAMINIFERALCALCITE
spectrometry
(TIMS) or
spectrometry(TIMS)
or by
by isotope
isotopedilution
dilutionelectrothermal
electrothermal
vaporization
inductively
coupled
plasma
vaporizationinductively coupled plasmamass
massspectrometry
spectrometry
(ETV-ICP-MS)
[Hastings et
et al.,
al., l996b].
(ETV-ICP-MS) [Hastings
1996b]. Drying
Drying the
the sample
samplein
in
the ETV
the
ETV unit
unit before
beforeanalysis
analysisquantitatively
quantitativelyeliminates
eliminates the
the
ClO+isobaric
C10
isobaricinterference
interferencewith
with V
V at
atmass
mass51,
51, which
whichis
is aasigsignificant
nificant problem
problemfor
for V
V determination
determinationby
byICP-MS.
ICP-MS. Analyses
Analyses
samples
sample
samplesof
of the
thedissolved
dissolved
samplewere
werediluted
dilutedinto
into25
25mL
mLof
ofLa
La
solution
(400
ppm
La
in
0.05
N
HC1
and
0.002
N
HNO3).
solution(400 ppm La in 0.05 N HC1and0.002 N HNO3).The
The
bulk metal
bulk
metal content
content of
of marine
marinesediments
sedimentswas
was determined
determinedby
by
digesting
dried sediments
in strong
digestingdried
sedimentsin
strongacids
acids(2
(2 mL
mL concentrated
concentrated
HNO3,
HF,
HC1O4)
HNO3, 33 mL
mL concentrated
concentrated
HF,and
and11mL
mLconcentrated
concentrated
HC104)
and
analysis
et al.,
and subsequent
subsequent
analysisby
by ICP-MS
ICP-MS [McLaren
[McLarenet
al., 1987;
1987;
Longerich et
et al.,
al., 1990].
with anomalously
high
at
with
anomalously
highisobaric
isobaricinterferences
interferences
at mass
mass50
50(50Cr
(50Cr Longerich
1990]. Details
Detailson
on the
theprocedure
procedureare
are given
givenby
by
and 5OTi)
that interfere
interfere with
with the
the isotope
Hastings [1994].
and
50Ti) that
isotopedilution
dilutionmeasurement
measurement Hastings
[1994].
are not
not included
mean values
values or
or shown
shown in
in the
the
are
included in
in the
the calculated
calculated mean
figures. This
This problem
occurred in
in 5%
figures.
problemoccurred
5% of
of the
the samples.
samples.
Measurement
precision on
on the
the same
Measurementprecision
samesample
sampleof
of aadissolved
dissolved
CaCO3
CaCO3 standard,
standard,equivalent
equivalentto
to 2.5
2.5 mg
mgcalcite
calciteafter
aftercleaning,
cleaning,
was
was ±3%
+3% (la;
(lo; nn=10)
=10) over
overthe
thecourse
courseof
ofone
oneICP-MS
ICP-MS run
runand
and
±7%
foramimferal
sam+7% (la;
(lo; n=9)
n=9)by
byTIMS.
TIMS.Using
Using55toto15-mg
15-mg
foraminiferal
samples
ples that
that have
havebeen
beencleaned
cleanedindividually
individually reduces
reducesthe
the average
average
precision
on duplicate
samplesto
to +8%
±8% (lo)
(la) by
precisionon
duplicate samples
by ICP-MS
ICP-MS and
and
±9%
+9% (la)
(lo) by
byTIMS.
TIMS. This
Thisreflects
reflectssome
someof
ofthe
thenatural
naturalvarivariability
ability in
in actual
actual samples
samplesand
and is
is also
alsoan
anindication
indicationof
of how
how
effective
effective the
the cleaning
cleaningprocedure
procedureis
is in
inremoving
removingcontaminant
contaminant
phases.
phases.The
The procedural
proceduralblank
blankvalue,
value,determined
determinedby
by nonisotope
nonisotope
dilution
dilution method,
method,was
was 0.27
0.27 pg
pg V.
V. The
The detection
detectionlimit
limit for
forETVETVICP-MS,
ICP-MS, defined
defined as
as 33 times
times the
the standard
standarddeviation
deviation of
of the
theblank
blank
at
at mass
mass51,
51, was
was0.3
0.3 pg
pgV
V without
withoutthe
theisotope
isotopespike
spikeand
and66 pg
pgV
V
using
isotope
dilution.
The
isobaric
interferences
at
mass
using isotope dilution. The isobaric interferencesat mass50
50
from
from Cr
Cr and
andTi
Ti significantly
significantlyaffect
affect the
the value
valuefor
for the
thedetection
detection
limit.
limit. A
A detailed
detailedexplanation
explanationof
of the
the analytical
analyticalmethod
methodis
is given
given
elsewhere
elsewhere[Hastings
[Hastingset
et al.,
al., 1996b].
1996b].
Magnesium, calcium,
Magnesium,
calcium, and
and manganese
manganesewere
were measured
measuredsimulsimultaneously
taneouslyby
by inductively
inductivelycoupled
coupledplasma
plasmamass
massspectrometry
spectrometry
(ICP-MS)
subsamplesof
of the
the dissolved
dissolved sample
(ICP-MS) on
on25-I.LL
25-gL subsamples
samplediluted
diluted
into
et al.,
al., 1996a].
into 2
2 mL
mL of
of 0.1
0.1 N
N HNO3
HNO 3 [Hastings
[Hastings et
1996a]. These
These
values
values were
were used
usedfor
forMg/Ca
Mg/Ca and
andMn/Ca
Mn/Cadeterminations.
determinations.
Calcium
Calcium analyses
analysesused
usedto
to calculate
calculateV/Ca
V/Ca ratios
ratioswere
wereperformed
performed
by
spectrophotometry.
Fifty-.LL
by flame
flameatomic
atomicabsorption
absorption
spectrophotometry.
Fifty-gL subsub-
Site
Description and
Site Description
and Chronology
Chronology
Caribbean
Sea
Caribbean
Sea
Two
shallow cores
cores were
were selected
selectedin
inthe
theCaribb6an
Caribban
Tworelatively
relatively
shallow
Sea.
(1l°39.83'N, 79°35.52'W;
Sea. TT9108-1GC
TT9108-1GC (11ø39.83'N,
79ø35.52'W; 2540
2540 m)
m) is
is
located
located in
in the
the western
westernregion
regionof
of the
theColumbia
ColumbiaBasin
Basin(Figure
(Figure
1). Measurements
of õ180
18O on
on C.
C. wuellerstorfi
Measurements
wuellerstorfiand
andthe
thevisual
visual
description
of the
the core
that the
the top
top 50
descriptionof
core indicate
indicatethat
50 cm
cm of
of the
the sedisediment
ment was
wassampled
sampledtwice.
twice. The
The gravity
gravitycore
coreprobably
probablypenetrated
penetrated
the
the sediment,
sediment,withdrew
withdrew briefly,
briefly, and
andthen
thenrepenetrated.
repenetrated.These
These
additional
50 cm
additional 50
cm are
are not
not included
included in
in data
data shown
shown for
for this
this core.
core.
Core
m) is
Core CP
CP 6001-4
6001-4 (14°55'N,
(14ø55'N, 71°
71 ø 50'W;
50'W; 3645
3645 m)
is from
from the
the
Beata
Beata Ridge
Ridge that
that separates
separatesthe
theColumbia
Columbiaand
andVenezuela
Venezuela
Basins.
Basins.The
The average
averagesedimentation
sedimentationrate
rate was
was 4.2
4.2 cm/kyr.
cm/kyr. Since
Since
the
the top
top 25
25 cm
cm of
of the
thepiston
pistoncore
coreare
aremissing,
missing,the
thedata
datashown
shown
are
are aa composite
compositeof
of the
thetrigger
triggerweight
weightcore
coreand
andthe
thepiston
pistoncore.
core.
The changes
in
l8O, V/Ca,
The
changes
in õ180,
V/Ca,and
andMg/Ca
Mg/Cain
in the
thetop
top50
50cm
cmwere
were
used to
used
to estimate
estimatethe
the extent
extentof
of the
thecore
coretop
topmissing
missingfrom
fromthe
the
piston
piston core.
core.
The 1800-m
The
1800-m sill
sill separating
separatingthe
the Caribbean
Caribbean Sea
Sea from
from the
the
Atlantic
Ocean
blocks
the
inflow
of
North
Atlantic
Atlantic Ocean blocks the inflow of North Atlantic Deep
Deep
Water.
Water. Deep
Deep Caribbean
Caribbeanwaters
waterstherefore
thereforereflect
reflect the
the chemistry
chemistry
of
of Atlantic
Atlantic intermediate
intermediate waters,
waters, and
and sediments
sediments from
from the
the
Caribbean
reflect dissolution
cycles that
that are
Caribbeanreflect
dissolutioncycles
are opposite
oppositein
in sense
sense
600
60 ø
ß
o
30°ø
30
cP6001
-4
ß
EN066 - 17GGC
0°o
o•
ß
ß
ß
30°
30 ø
1200
120ø
600
60ø
00
0o
Figure
Location of
of cores
cores used
used in
and water
water depths
depths for
for these
these cores
cores are
are
Figure 1.
]. Location
in this
this study.
study.Specific
Specific locations
locationsand
EN066-17GGC,
5°22'N, 21ø5'W,
2l°5'W, 3050
EN066-17GGC, 5ø22'N,
3050 m;
m; CP6001-4PC,
CP6001-4PC, 14°55'N,
14ø55'N, 71°50'W,
71ø50'W, 3645
3645 m;
m; and
and Tr9108-1GC,
TT9108-1GC,
ll°39.83'N,
11ø39.83'N, 79°35.52'W,
79ø35.52'W, 2540
2540 m.
m.
668
668
HASTINGS
E AL.:
VANADIUM
IN
CALCITE
HASTINGS
ET
AL.:
VANADIUM
INFORAMINIFERAL
FORAMINIFERAL
CALC1TE
to
to the
the dissolution
dissolutioncycles
cyclesof
of the
thedeep
deepAtlantic
Atlantic[Peterson,
[Peterson,1990;
1990;
see
et al.,
see also
also Imbrie
Irnbrie et
al., 1992].
1992]. In
In contrast
contrast to
to Atlantic
Atlantic sedisedi•
ments,
ments,glacial
glacialCaribbean
Caribbeansediments
sedimentsreflect
reflectenhanced
enhancedcarbonate
carbonate
preservation.
preservation.
Eastern
Eastern Equatorial
Equatorial Atlantic
Atlantic
Core
(5°22'N, 21°5'W)
Core EN066-17GGC
EN066-17GGC (5ø22'N,
21ø5'W) is
is aa278-cm
278-cmgravity
gravity
core
raised
from
3050
m
water
depth
on
the
Sierra
core raisedfrom 3050 m water depth on the SierraLeone
LeoneRise.
Rise.
The
is based
The chronology
chronologyis
basedon
onisotope
isotopestage
stageboundaries
boundariesestiestimated from
from oxygen
isotope changes
measured on
on C.
mated
oxygenisotope
changesmeasured
C. wuellerwueller-
storfi
[Curry and
storfi and
andon
onchanges
changesin
in percent
percentcarbonate
carbonate [Curry
and
Lohmann,
Lohrnann,1986].
1986]. Ages
Agesassociated
associatedwith
with these
thesestage
stageboundaries
boundaries
are from
Imbrie et
et al.
the effects
effects of
of the
are
from Irnbrie
al. [19841
[ 1984] and
and incorporate
incorporatethe
the
now
[Bard
14C-Uyear
yeardifferences
differences
nowobserved
observed
[Bardet
et al.,
al., 1990].
1990].The
The
multilinear algorithm
algorithm [Keigwin
and Jones,
Jones, 1994]
based on
on the
multilinear
[Keigwin and
1994] based
the
original linear
linear equation
original
equation[Bard
[Bard et
et al.,
al., 1993]
1993] was
wasused
usedto
to make
make
the corrections
the
correctionsto
to calendar
calendaryears.
years.Carbonate
Carbonatecontent
contentdecreases
decreases
downcore from
from Holocene
Holocene values
values of
of 75%
75% to
to glacial
downcore
glacial values
valuesof
of
Table
for G.
Table 1.
1.V/Ca,
V/Ca, Mn/Ca,
Mn/Ca, and
andMg/Ca
Mg/Ca Values
Values for
G. sacculifer
sacculifer
From 'Core
Core TT9108-1GC
From
TF9108-1GC
1
Corrected
Depth,
Corrected
Depth,
1
cm
cm
V/Ca,
V/Ca,
nmol/mol
nmol/mol
Mn/Ca,
Mn/Ca,
ILmol/mol
gmol/mol
Mg/Ca,
Mg/Ca,
mmol/mol
mmol/mol
11
20.5
20.5
4.6
4.6
3.87
3.87
1
31.0
31.0
26.6
26.6
6.8
3.98
3.98
7.4
3.75
27.2
27.2
62.4
62.4
36.9
96.2
96.2
89.0
3.8
3.56
3.56
21.5
21.5
3.66
3.66
23.8
23.8
3.58
10
10
20
20
20
:30
30
30
•
49.4
49.4
51.7
51.7
58.4
58.4
59.4
59.4
3.41
3.47
3.47
40
40
146
40
40
60
60
137
261
116
3.07
60
60
261
132
3.26
3.26
80
80
814
152
3.10
3.10
80
80
307
166
3.07
3.07
basin are
are less
than those
basin
less corrosive
corrosive than
those in
in the
the western
western basin
basin due
due to
to
100
100
229
3.11
the relatively
low amount
Bottom Water
Water
the
relatively low
amountof
of corrosive
corrosiveAntarctic
Antarctic Bottom
(AABW)
that enters
enters the
the basin
basin [Warren,
(AABW) that
[Warren, 1981].
1981]. Thunell
Thunell [1982]
[1982]
100
400
400
398
487
469
552
552
216
3.07
3.07
220
220
3.37
3.37
approximately 50%
approximately
50% CaCO3
CaCO3 [Curry
[Curry and
and Lohmann,
Lohrnann,1986,
1986,
1990]. This
This relatively
relatively shallow
core in
1990].
shallow core
in the
theeastern
easternAtlantic
Atlantic was
was
chosen to
to avoid
of calcite.
chosen
avoid dissolution
dissolutionof
calcite. Deep
Deep waters
waters in
in this
this
120
3.27
3.27
3.25
estimated the
the lysocline
lysocline to
to be
be 4800
120
231
3.32
120
3.32
estimated
4800 m
m in
in the
the eastern
easternbasin
basin
compared with
with 4000-4300
4000-4300 mm in
compared
in the
the western
western Atlantic.
Atlantic.
359
3.50
140
3.50
Foraminiferal fragmentation
140
Foraminiferal
fragmentationand
andfraction
fractionofofdissolution-resisdissolution-resis272
3.34
tant species
tant
species increase
increase sharply
sharply at
at 4600
4600 m,
m,suggesting
suggesting
increasing levels
levels of
of dissolution
below that
increasing
dissolutionbelow
that depth
depth[Dubois
[Dubois and
and
1 Depths at and below 10 cm have been corrected for the apparent
1
DePths
atand
below
10cmhave
been
corrected
fortheapparent
Prell, 1988].
accumulation
data
Prell,
1988]. Fragmentation
Fragmentationand
andcarbonate
carbonate
accumulation
data
double Penetration
penetration of
of the
the gravity
50
double
gravitycore
coreby
by subtracting
subtracting
50 cm
cmfrom
fromthe
the
in
the
eastern
basin
indicate
a
shoaling
of
the
lysocline
by
in the easternbasin indicate a shoalingof the lysocline by
original depths.
original
depths.
1000 m
m during
1000
during glacial
glacial stages
stages[Curry
[Curry and
andLohmann,
Lohrnann,19861,
1986],
which implies
implies that
which
that the
the foraminiferal
foraminiferal lysocline
lysocline was
was at
at about
about
3700
between V/Ca
V/Ca and
3700 m
m during
duringthe
the last
lastglacial
glacialperiod.
period.
between
and Mn/Ca
Mn/Ca values
valuesis
is significant,
significant,with
with aa regresregres-
Results
Results
Caribbean Sea
Sea
Caribbean
Relatively
Relatively shallow
shallow cores
corescollected
collectedabove
abovethe
theforaminiferal
foraminiferal
lysocline
were
sampled
in
order
to
avoid
the
lysoclinewere sampledin order to avoidthe effect
effectrelated
relatedto
to
partial
for core
partial dissolution.
dissolution.Foraminiferal
Foraminiferal fragmentation
fragmentationfor
core CP
CP
6001-4
6001-4 (3645
(3645 m)
m) is
is less
lessthan
than10%
10% throughout
throughoutthe
the core
coreto
to stage
stage
5,
5, reflecting
reflecting good
goodpreservation
preservation(L.
(L. Peterson,
Peterson,personal
personalcomcommunication,
munication, 1993).
1993). Sediments
Sedimentsfrom
from core
core TI'
T1r 9108-1,
9108-1, which
which is
is
1100
m shallower
1-4, should
should also
also be
be well
1100 m
shallower than
than CP
CP 600
6001-4,
well prepreserved.
served.Thus
Thus partial
partial dissolution
dissolutionof
of tests
testsshould
shouldnot
not be
be aa signifsignificant
V/Ca ratios
ratios in
in G.
G. sacculifer
icant effect.
effect. In
In core
core 'FT
TT 9108-1,
9108-1, V/Ca
sacculifer
(355-425
increase linearly
linearly with
with depth
(355-425 j.tm)
gm) increase
depth from
from aa core-top
core-top
value
value of
of 20
20 nmol
nmol V/mol
V/mol Ca
Ca to
tovalues
valuesgreater
greaterthan
than500
500
nmol/mol
at 140
nmol/mol at
140 cm
cm (Table
(Table 1).
1). Mn/Ca
Mn/Ca values
valuesalso
alsoincrease
increase
from
Ca •at
at the
from aa value
valueof
of less
lessthan
than88j.tmol
gmol Mn/mol
Mn/mol Ca
the top
top of
of the
the
core
to
270
tmol/mol
at
140
cm.
In
core
CP6001-4,
V/Ca
core to 270 gmol/mol at 140 cm. In core CP6001-4, V/Ca
ratios
ratiosin
in G.
G. sacculifer
sacculifer(355-425
(355-4251.tm)
gm) increase
increasemonotonically
monotonically
with
with depth
depthfrom
from aa mean
meancore-top
core-topvalue
valueof
of 20.5
20.5nmol
nmolV/mol
V/mol Ca
Ca
to
to aa value
valueof
of 312
312nmollmol
nmol/molat
atstage
stageSe
5e(Table
(Table2).
2). Mn/Ca
Mn/Ca ratios
ratios
also
1010J.tmol
alsoincrease
increasefrom
fromaacore-top
core-topvalue
valueofofabout
about
•mol Mn/mol
Mn/mol
Ca
Ca to
to500
500l.tmol/mol
•mol/mol at
at 482
482 cm,
cm,stage
stageSe.
5e.
In these
V values
values at
at
In
these two
two Caribbean
Caribbean cores,
cores, the
the foraminiferal
foraminiferal V
depth
depthare
are 15-25
15-25 times
timesgreater
greaterthan
thanthe
thecore-top
core-topvalue,
value,while
while
the
Mn/Ca
values
are
35-50
times
higher.
The
the Mn/Ca values are 35-50 times higher. The correlation
correlation
sion coefficient
coefficient of r2
r 2 = 0.98 for TT9108-1GC
TT9108-1GC and
and r2
r2 =
= 0.80
0.80 for
for
CP
6001-4
(Figures
2a
and
2b).
Living
foraminifera
incorpoCP 6001-4 (Figures2a and 2b). Living foraminiferaincorporate very
(<15
rate
very little
little Mn
Mn into
intotheir
theirtests
tests
(<15j.Lmol
gmol Mn/mol
Mn/mol Ca),
Ca), as
as
shown
shownby
by core-top
core-topvalues
valuesin
in this
thisstudy
studyand
andprevious
previousmeasuremeasure-
ments of
These data
ments
of sediment
sedimenttrap
trap samples
samples[Boyle,
[Boyle, 1983].
1983]. These
data
suggest
that
a
Mn-rich
phase,
accreted
after
deposition,
suggestthat•a•Mn-rich phase, accretedafter deposition,concontrols both
in
trols
both the
the Mn
Mn and
and V
V contents
contents of
of foraminiferal
foraminiferal calcite
calcite in
these sediments.
It is
oxyhydroxide
these
sediments.
It
isnot
notlikely
likelyto
tobe
beaaFeMn
FeMn
oxyhydroxide
coating since
cleaning step
step used
used to
coating
since the
the reductive
reductive cleaning
to clean
clean the
the
foraminiferal
tests
effectively
removes
these
oxyhydroxides
foraminiferal tests effectively removesthese oxyhydroxides
[Boyle
and Keigwin,
Hastings et
et al.,
[Boyle and
Keigwin, 1985/86;
1985/86; Hastings
al., 1996a].
1996a].
Recrystallization
incorporation
Recrystallizationand
andsubsequent
subsequent
incorporationof
of authigenic
authigenic
Mn
Mn in
in the
theforaminiferal
foraminiferaltest
testis
isnot
notplausible
plausiblesince
sincethe
thestable
stable
isotopic
composition
of
foraminifera
accurately
records
isotopic compositionof foraminiferaaccuratelyrecordsthe
the
chemistry
chemistryof
of the
thewater
waterin
inwhich
whichthey
theygrew.
grew.The
Themost
mostlikely
likely
explanation
is aa mixed
overgrowth
explanationis
mixedMn,
Mn, Ca
Cacarbonate
carbonate
overgrowthon
onthe
the
tests
in
sediments
during
teststhat
thatis
isdeposited
deposited
inthe
thereducing
reducing
sediments
duringdiagendiagenesis
esisfBoy!e,
[Boyle, 1983].
1983.].A
A mixed
mixedMn-Ca-Mg
Mn-Ca-Mg carbonate
carbonatehas
hasbeen
been
identified
in
many
reducing
environments
[Lynn
and
identifiedin many reducingenvironments[Lynn andBonatti,
Bonatti,
1965;
Pedersen and
and Price,
and Price,
1965; Pedersen
Price,1982;
1982;Shimmield
$hirnrnieldand
Price, 1986]
1986]
and
and has
has been
beensuggested
suggestedto
to control
controlpore
porewater
waterMn
Mn concenconcentrations
et al.,
al., 1987].
carbonate
trations[Middelburg
[Middelburget
1987]. Such
Suchmanganoan
manganoan
carbonate
coatings
are
highly
enriched
in
trace
elements,
including
coatingsare highly enrichedin trace elements,includingBa,
Ba,
Cd,
Cd, and
and U
U [Boyle,
[Boyle, 1983;
1983; Russell
Russell et
et al.,
al., 1994,
1994, 1996].
Vanadium
is enriched
Vanadium is
enrichedin
in other
otherMn
Mn phases,
phases,including
includingmanmanganese
ganesenodules
nodules[Cronan,
[Cronan,1976]
1976]and
andMn-rich
Mn-richmetalliferous
metalliferoussedsed-
669
669
HASTINGS ET
Er AL.:
CALCiTE
AL.:VANADIUM
VANADIUM IN
INFORAMINTFERAL
FORAMINIF'-F_RAL
CALCITE
Table
Table 2.
2. V/Ca,
V/Ca,Mn/Ca,
Mn/Ca,and
andMg/Ca
Mg/CaValues
Valuesfor
for G.
G. sacculifer
sacculifer
Samples
From
Caribbean
Core
CP6001-4
(3654
SamplesFrom CaribbeanCore CP6001-4(3654m)
m)
V/Ca,
V/Ca,
Corrected
Depth,1
Corrected
Depth,
1
cm
cm
Mn/Ca,
Mn/Ca,
nniol/mol
nmol/mol
Mg/Ca,
Mg/Ca,
mmol/mol
mmol/mol
Itmol/mol
gmol/mol
Trigger
TriggerWeight
WeightCore
Core
1
1
25.0
25.0
11
16.4
16.4
7
15.6
15.6
7
28.8
28.8
60.2
60.2
52.6
52.6
97.0
97.0
22
22
22
41
41
41
(311))
(311
3.71
3.84
8.7
8.7
47.9
47.9
47.8
47.8
3.87
3.87
3.63
3.63
3.66
3.66
3.12
3.12
3.09
3.09
125
Piston
Piston Core
Core
39.7
39.7
76.0
76.0
67.4
67.4
63.7
63.7
62.9
62.9
51.7
51.7
3.67
3.67
2.96
2.96
3.17
3.17
3.10
3.10
3.24
3.24
3.24
3.24
105
102
79.1
79.1
78.9
78.9
57.7
57.7
55.3
55.3
111
25.5
25.5
71.3
71.3
31.5
31.5
42
42
52
52
52
72
72
162
162
202
202
202
202
242
242
242
242
542
542
542
542
662
662
662
662
4.32
4.32
10.2
10.2
8.4
8.4
139
129
45.2
45.2
146
123
110
3.07
3.07
3.15
3.15
3.17
3.17
113
113
3.18
3.18
114
154
159
184
179
304
304
320
320
96.0
96.0
95.2
95.2
484
484
3.36
3.36
3.45
3.45
3.86
3.86
506
506
3.91
160
3.16
3.12
150
iments
iments [Piper,
[Piper, 1973].
1973]. Based
Basedon
on the
therelated
relatedgeochemistries
geochemistriesof
of
Mn and
Mn
and V
V and
and the
the enrichment
enrichment of
of other
other trace
trace metals
metals in
in Mn
Mn carcarbonate, the
bonate,
the Mn
Mn carbonate
carbonateovergrowth
overgrowthwould
would also
alsobe
bepredicted
predicted
to be enriched
to
enriched in vanadium.
vanadium.
To obtain
V, itit is
is essential
to monitor
To
obtain reliable
reliable foraminiferal
foraminiferal V,
essential to
monitor
Mn levels.
Mn
levels. Samples
Samples with
with Mn/Ca
Mn/Ca >
> 50
50 limol/mol
!.tmot/moland
and with
with
foramin*feral VV values
values that
that are
are linearly
foraminiferal
linearly correlated
correlatedwith
with Mn/Ca,
Mn/Ca,
such
suchas
as those
thosefrom
from the
theCaribbean
Caribbeancores,
cores,cannot
cannotbe
beinterpreted
interpreted
as
indices
of
paleo-seawater
vanadium
levels.
However,
based
as indices of paleo-seawatervanadiumlevels. However, based
on measured
Mn/Ca values
values from
from aa given
on
measured Mn/Ca
given sample
sample and
and the
the
correlation observed
correlation
observed in the
the Caribbean
Caribbean cores
cores where
where the
the Mn
Mn carcar-
bonate
bonate phase
phasecontrols
controls the
the V
V content,
content,we
wecan
canquantitatively
quantitatively
estimate
the
fraction
of
V
from
the
Mn
carbonate
estimatethe fraction of V from the Mn carbonatephase.
phase.The
The
estimated
is 0.2
estimated V
V content
content of
of the
the Mn
Mn carbonate
carbonate is
0.2 and
and 0.06
0.06 molar
molar
percent for
for cores
cores TT
TI' 9l08-1GC
percent
9108-1GCand
andCP
CP6001-4,
6001-4,respectively,
respectively,
based
basedon
on the
the slope
slopeof
of the
theregression
regressionlines
linesshown
shownin
in Figure
Figure 2.
2.
Although
leaching
briefly
with
acid
(0.1
N
HNO3)
does
Althoughleachingbriefly with acid (0.1 N HNO3) doesappear
appear
to
to preferentially
preferentiallydissolve
dissolvethe-Mn
the-Mn carbonate
carbonatephase
phaserelative
relative to
to
the
the calcite,
calcite, removal
removal of
of the
the Mn
Mn carbonate
carbonateis
is incomplete,
incomplete,and
and
losses
associated
with
this
modified
cleaning
lossesassociatedwith this modified cleaningprocedure
procedureare
are
unacceptably
high given
unacceptablyhigh
given the
the required
requiredsample
samplesize.
size.
Eastern Equatorial
Eastern
Equatorial Atlantic
Atlan½,ic
Foraminiferal V/Ca
V/Ca values
valuesin
in G.
G. sacculifer
sacculifer (355-425
tm)
Foraminiferal
(355-425 !.tm)
from core
core ENO66-17GGC
EN066-17GGC are
from
arerelatively
relativelyconstant
constantin
in the
the upperuppermost 50
50 cm
most
cm (Figure
(Figure 3;
3; Table
Table 3)
3) and
andare
areconsistent
consistentwith
with the
the
global
data set
et al.,
al., 1996a].
In the
the 50
global core-top
core-top data
set [Hastings
[Hastingset
1996a]. In
50 to
to
90-cm
dramatically
90-cm interval,
interval,V/Ca
V/Ca increases
increases
dramaticallyto
to105
105nmol/mol,
nmol/mol,
aa value
value55 times
timesgreater
greaterthan
thanthe
thecore-top
core-topvalue,
value,and
andthen
thendoes
does
not
not change
changesignificantly.
significantly. Mn/Ca
Mn/Ca ratios
ratios increase
increaselinearly
linearly with
with
depth
depth to
to values
valuesof
ofapproximately
approximately200
200j.tmollmol
!.tmol/molat
at 200
200 cm.
cm.
Although
both Mn/Ca
Although both
Mn/Ca and
and V/Ca
V/Ca increase
increasewith
with depth,
depth,the
the
changes
(Figure
changesare
are asynchronous
asynchronous
(Figure4).
4).
11Piston
Piston core
The dramatic
dramatic increase
increase in
in foraminiferal
foraminiferal vanadium
vanadium from
from 50 to
to
depths
have
been
corrected
by
25
core
depths
have
been
corrected
byadding
adding
25cm
cmtotoaccount
account The
for
90
for loss
lossof
of core
coretop.
top.
90 cm
cm is
is due
dueto
topartial
partialdissolution
dissolutionof
offoraminiferal
foraminiferaltests
testsfolfol-
300
300
ß
I
'
I
'
I
'
I
'
I
600
6OO
:
(a)
TT9108 ...,
....'"'•
250
25O
ß
I
'
I
'
I
'
I
'
I
'
I
(b) CP 6001
5OO
500
'
....).
ß
.
o
E
200
200
0
400
400
0
300
3OO
E
o
E 150
E
'3
Q
c1
100
lOO
Q
200
200
50
5O
100
lOO
0
o
0o
0
100
100
200
200
300
500
300 400
400
500 600
600
V/Ca
V/Ca(nmoVmol)
(nmol/mol)
•
0
0
.,.?
.......
- ......+++
_•,"' I
50
50
,
I
,
I
,
I
,
I
100 150
350
100
150 200
200 250
250 300
300 350
V/Ca
V/Ca (nmol/mol)
(nmol/mol)
Figure
TT91O8-1and
and CP
CP 6001-4.
6001-4. Calculated
Calculated regressions
Figure 2.
2. V/Ca
V/Caplotted
plottedversus
versusMn/Ca
Mn/Ca for
forCaribbean
Caribbeancores
coresTT9108-1
regressions
are
intervals
are shown
shown by
by the
the dotted
dotted lines.
lines. (a)
(a) Core
Core TT9108T1'9l08are indicated
indicatedby
by the
theheavy
heavylines
linesand
and99%
99%confidence
confidence
intervalsare
1:
calculated slope
slope == 0.513,
1: calculated
0.513, y
y intercept
intercept=
= -4.5,
-4.5, r2=0.98,
r2=0.98, and
and n
n == 18.
18.(b)
(b) Core
CoreCP
CP6001-4:
6001-4:calculated
calculatedslope
slope=
=
1.52,
y intercept
1.52, y
intercept=
= -62.9,
-62.9, r2=0.81,
r2=0.81,and
andnn == 23.
23.
HASTINGS HF
ET AL.: VANADIUM
VANADIUM IN
IN FORAMINIFERAL
FORAMINIFERAL CALCITE
670
180
80 (%ø)
(%)
44.5
4
3.5
3
Mn/Ca
Mn/Ca(j.tmol/mol)
(pmol/mol)
G.
sacculifer
G. sacculifer
0
2.5
0
.._*_
E
0
9
a)
.'
+
3.
.
.
.
-
',
5
+
-
.
.
-
-
---;.
..
200
2oo
.
:.-..
-
-
250
25o
(a)
.
C.
C. wuellerstorfi
wuellerstorfi
100 150
50
50
100
150 200
200
50
0
100
150
00
I_D
.
--+
-
++
.
-I- -I-
.................
xx
.
.
x
x
o
.-
,-'
X
4.
G. sacculifer
sacculifer
G.
..................
..+I-
,x
+
--'I.
150
15o
I
--x
50
50
100
lOO
200
200
I
IC
Q
.c
100
100
(
V/Ca (nmol/mol)
V/Ca
(nmol/mol)
V/Ca (nmoVmol)
V/Ca
(nmol/mol)
::::::::::::::::::::::::::::::::::::::::::::::::::
;-:::::::::::::::::::::::::::::::::::::::
-II-H-
.
++
- -
X
x
-
+4-
+
.
.
-
++
+:::
.... :::::'. ........................
-s.-
:::::::::
.............
::::::::::::::::::::::::
:.:,:,:,:.:,:.1.1,;
:::::::::::::::::::::::
++
...............
:1-:+;-.'.-,-...,,,,.,',
-
(b)
::::::::::::::::::::::::::
(c)
)
(d) -
Figure 3.
equatorial
Atlantic
at 3050
Figure
3. Eastern
Eastern
equatorial
Atlanticcore
coreEN066-17GGC
EN066-17GGCat
3050 m.
m. (a)
(a) 6180
b]80 from
from C.
C. wuellerstorfi;
wuellerstorfi;glacial
glacial
6180
stages
1-6
are
indicated
on
the
right
side
of
the
depth
profile
and
separated
by dashed
dashed lines.
lines. (b)
(b) Mn/Ca
Mn/Ca and
stages1-6 areindicatedon therightsideof the8•80 depthprofileandseparated
by
and
(c)
with depth
species C.
C. wuellerstoifi
(c) V/Ca
V/Ca variations
variationswith
depthin
in cleaned
cleanedG.
G. sacculifer.
sacculifer.(d)
(d) V/Ca
V/Ca in
in cleaned
cleanedbenthic
benthicspecies
wuellerstorfi
from select
from
select intervals.
intervals.
lowing deposition.
deposition. In
In this
this core,
lowing
core, mean
mean V/Ca
V/Ca values
valuesfor
for each
each
isotope stage
stage show
show aa clear
on the
the relative
relative extent
extent of
of
isotope
clear dependence
dependenceon
dissolution,
as
estimated
by
the
fragmentation
data
(Figure
5).
dissolution,as estimatedby the fragmentationdata (Figure 5).
Foraminiferal fragmentation
fragmentation in
in the
Foraminiferal
the >250-Jim
>250-I.tm fraction,
fraction, aa relireliable indicator
indicator of
of dissolution,
is 6-7%
6-7% for
for stage
able
dissolution,is
stage 11 and
and glacial
glacial
stage 2,
33and
stage
2, increases
increasesto
to 13%
13%and
and23%
23%for
forstages
stages
and4,4,respecrespectively,
and
decreases
to
10%
for
interglacial
stage
[Curry and
and
tively, and decreases
to 10% for interglacialstage55 [Curry
Lohmann,
Lohmann,1986].
1986]. Based
Basedon
on this
thisindex,
index,the
thegreatest
greatestdissolution
dissolution
would be
be expected
with
would
expectedin
in stage
stage4,
4, consistent
consistent
withfragmentation
fragmentation
data
data from
from adjacent
adjacentcores
coresat
at the
theSierra
SierraLeone
LeoneRise.
Rise.Individual
Individual
foraminifera
of aa given
foraminiferaof
givenspecies
speciesin
in the
the85
85 to
to90-cm
90-cminterval
intervalare
are
visibly
than those
those at
visibly more
more dissolved
dissolved than
at or
or above
above50
50 cm
cmwhen
when
viewed
to
viewed at
at 40x
40x magnification,
magnification, lending
lending qualitative
qualitative support
support to
this
In the
only the
the 00 to
this conclusion.
conclusion.In
the following
following sections,
sections,only
to 5050-
cm interval
is considered
from this
this core
this is
is the
cm
interval is
considered from
core because
because this
the
only section
artifacts
only
sectionlargely
largely free
free of
of postdepositional
postdepositional
artifactsrelated
related
to partial
to
partial dissolution
dissolutionof
of foraminifera
foraminifera tests.
tests.
Since aa Mn-rich
Since
Mn-rich phase
phasehas
hasbeen
beeninferred
inferredtotoaffect
affectsignifisignificantly
the
vanadium
content
of
foraminifera
even
cantly the vanadium content of foraminifera even at
at Mn/Ca
Mn/Ca
ratios below
the V/Ca
V/Ca values
values from
ratios
below100
100j.LmolJmol,
gmol/mol, the
from core
coreEN066EN066-
117GGC
7GGChave
have been
been corrected
corrected for
for the
the amount
amount of
of vanadium
vanadium
expected to
to be
expected
be in
in the
thecontaminant
contaminantphase.
phase.Based
Basedon
on the
the slope
slope
of
shown
of the
theregression
regression
shownin
in Figure
Figure2b
2bbetween
betweenMn/Ca
Mn/Ca and
andV/Ca
V/Ca
in the
in
the Caribbean
Caribbean core
core CP
CP 6001-4,
6001-4, 0.06
0.06 molar
molar percent
percent V
V is
is
predicted to
to be
be in
predicted
in the
theMn
Mn carbonate
carbonatephase.
phase.Sediments
Sedimentsfrom
from CP
CP
6001-4
6001-4 are
are more
morerepresentative
representativeof
of the
thepelagic
pelagicconditions
conditions
encountered
at
the
Sierra
Leone
Rise
in
the
equatorial
encounteredat the Sierra Leone Rise in the equatorialAtlantic;
Atlantic;
the
the shallower
shallowerwater
waterdepth
depthand
andhigher
higherproductivity
productivityof
of overlying
overlying
water
water suggest
suggestthat
that sediments
sedimentsfrom
from TT9108-IGC
TT9108-1GC are
are more
more
reducing with
reducing
with higher
higher pore
pore water
water[Mn]
[Mn] than
thanthose
thosefrom
fromeither
either
CP 6001-4
located in
in the
of the Caribbean
Sea or
or the
the
CP
6001-4 located
the middle
middle of
Caribbean Sea
equatorial Atlantic.
Atlantic. The
The correction
equatorial
correctionfor
for Mn
Mn carbonate
carbonateassumes
assumes
that some
that
someMn
Mn is
is incorporated
incorporatedinto
into the
theforaminiferal
foraminiferaltest
testwhen
when
it is
it
is originally
originallyformed.
formed.Based
Basedon
on the
the average
averageMn/Ca
Mn/Ca value
value of
of
15 limol/mol
15
I.tmol/mol for
for reductively
reductivelycleaned
cleanedplanktonic
planktonicforaminifera
foraminifera
collected
and the
collectedin
in sediment
sedimenttraps
traps[Boyle,
[Boyle, 1983]
1983] and
the range
rangeof
of
core-top
in this
core-topMn
Mn values
valuesdetermined
determinedin
this work
work (5-10
(5-10 imolJmol),
!.tmol/mol),
an
for
an average
averagevalue
valueof
of Mn/Ca
Mn/Ca =
= 10
10 tmol/mol
I.tmol/molhas
hasbeen
beenchosen
chosen
for
lattice-bound
overgrowth
lattice-boundMn.
Mn. The
The Mn
Mn carbonate
carbonate
overgrowthcorrection
correction
for
for V/Ca
V/Ca is
is
(V/Ca)corr
((Mn/Ca)m
10)xO.6
(V/ Ca)cor
r =(V/Cm
(V/ Ca)m
- ((Mn/ Ca)m
- 10)x0.6
(1)
(1)
where (V/Ca)m
where
(V/Ca)m and
and(Mn/Ca)m
(Mn/Ca)m refer
refer to
to measured
measuredratios
ratiosin
in the
the
cleaned
calcite inin units
units of
of nmol
cleaned foraminiferal
foraminiferal
calcite
nmol V/mol
V/mol Ca
Ca and
and
jimol
I.tmol Mn/mol
Mn/mol Ca,
Ca, respectively.
respectively.Corrections
Corrections are
are small:
small: less
less
than
than 15%
15% of
of the
theinitial
initialvalues,
values,except
exceptfor
forthe
the50-cm
50-cminterval,
interval,
which
which is
is corrected
correctedby
by 30%.
30%. Unless
Unlessstated
statedotherwise,
otherwise,all
all V/Ca
V/Ca
data
presented
in
the
following
sections
are
corrected
data presentedin the following sectionsare correctedvalues.
values.
The
The mean
mean corrected
correctedV/Ca
V/Ca value
value of
of 21.6
21.6 (±2.8;
(+2.8; n=14)
n=14) nmollmol
nmol/mol
for
for this
this 35-kyr
35-kyr period
period(Figure
(Figure6)
6) compares
compareswell
well with
with the
themean
mean
global
value of
of V/Ca
= 21.7
global core-top
core-topvalue
V/Ca =
21.7 (±3.6)
(+3.6) for
for G.
G. sacculifer
sacculifer
[Hastings
[Hastingset
et al.,
al., 1996a].
1996a].
The
The trends
trends in
in the
the vanadium
vanadium measurements
measurements for
for benthic
benthic
species
speciesC.
C. wuellerstorfi
wuellerstorfi(250-425
(250-425lIm)
gm) are
aresimilar
similarto
to the
theplankplank-
tonic
tonic profile,
profile, with
with aa constant
constantV/Ca
V/Ca value
valueof
of109
109nmol/mol
nmol/mol
(±10%)
in
the
top
30
cm
and
a
significant
increase
(+10%) in the top 30 cm and a significantincreaseat
at 90
90 cm
cm
(Figure
con(Figure 3d;
3d; Table
Table 4).
4). The
Theexisting
existingbenthic
benthicmeasurements
measurements
confirm
species.
firm the
thetrend
trendobtained
obtainedfrom
fromthe
theplanktonic
planktonic
species.
671
671
HASTINGS
Er AL:
VANADIUM
IN
CALCITE
HASTINGS
ET
AL.:
VANADIUM
INFORAMINIFERAL
FORAMINIFERAL
CALCITE
Table
for
From
Equatorial
Atlantic
Table3.
3.V/Ca,
V/Ca,Mn/Ca,
Mn/Ca,and
andMg/Ca
Mg/CaValues
Values
forG.
G.sacculifer
sacculifer
FromEastern
Eastern
Equatorial
AtlanticCore
CoreEN066-17GGC
EN066-17GGC
Depth,
Depth,
cm
cm
Age,
Age,
ka
ka
V/Ca,
V/Ca,
nmol/mol
nmol/mol
(V/Ca)co,' 1
(V/Ca)corr
22.1
22.1
(31.0)
(31.0)
21.6
21.6
20.0
24.8
1
0.8
22.1
1
3.5
3.5
3.5
3.5
0.8
0.8
(31.0)
(31.0)
21.6
21.6
20.0
1
10
2.9
2.9
8.3
10
8.3
8.3
20
16.0
20
16.0
24
24
30
30
37
37
50
70
70
70
70
90
90
90
90
110
130
130
130
150
150
170
190
190
200
200
200
200
210
210
210
210
220
220
220
220
230
230
230
230
240
240
240
240
250
250
250
250
18.5
18.5
22.4
22.4
22.4
22.4
26.9
26.9
34.8
46.7
46.7
46.7
58.6
58.6
58.6
58.6
69.0
69.0
24.8
17.8
17.8
142
142
28.2
20.9
51.5
41.3
76.6
76.6
68.9
71.8
62.2
62.2
61.8
62.7
62.7
48.5
48.5
66.1
-2.0
-2.0
-8.5
-8.5
32.3
32.3
4.6
4.6
43.4
43.4
44.9
44.9
93.5
93.5
21.0
21.0
107
6.1
140
140
(347)
103
--17.2
19.6
106
19.1
122
122
11.4
123
123
59.5
105
97.1
103
108
110
97.3
97.3
97.3
111.9
111.9
126.5
126.5
122
110
113
86.0
86.0
83.5
135
121
145
145
136
136
199
199
98.0
98.0
103
99.5
99.5
19.9
19.9
19.4
3.74
3.74
3.66
3.66
3.66
3.73
3.82
3.64
3.37
3.48
3.48
3.11
3.10
3.22
3.12
2.93
2.93
2.99
2.91
3.03
3.03
3.00
3.00
3.09
3.09
3.21
3.51
3.49
3.49
3.48
3.48
3.70
3.70
3.76
3.76
3.75
3.75
3.73
3.73
3.93
3.93
3.88
3.88
3.52
3.52
3.38
3.38
3.57
3.57
3.44
3.44
3.45
3.45
3.73
3.73
3.64
3.66
3.66
3.68
3.68
3.66
3.66
3.78
3.78
7.5 ;;
11.1
11.1 •
10.3
10,3
33.1
33.1
30.5
69.8
18.5
18.5
Mg/Ca,
MgtCa,
minol/mol
mmol/mol
2.3
2.3
2.3
2.3
8.0
8.0
8.9
6.4
6A •'i.
23.3
23.3
24.7
24.7
20.3
20.3
21.1
21.1
82.7
147.0
147.0
147.0
147.0
153.8
153.8
153.8
160.6
160.6
160.6
160.6
167.6
167.6
167.6
167.6
17.8
17.8
Mn/Ca,
Mn/Ca,
iniol/mol
gmol/mol
24.0
24.9
22.4
23.0
21.2
22.8
24.1
82.7
82.7
126.
126.5
133.4
133.4
133.4
133.4
140.2
140.2
140.2
140.2
nmol/mol
nmol/mol
13.6
13.6
13.1
13,1
14.5
14.5
14.8
14.8
17.9
18.2
18.2
26.0
26.0
30.8
30.8
30.6
30.6
44.7
44.7
43.9
43.9
47.3
67.1
67.1
70.6
70.6
85.3
85.3
87.9
87.9
68.4
68.4
123
128
143
160
160
141
127
146
146
166
166
120
120
117
117
,
,
Foraininiferal V
of
Foraminiferal
V values
valuesbelow
below50
50cm
cmare
arenot
notreliable
reliabledue
dueto
topartial
partialdissolution
dissolution
oftests.
tests.
=
-_((Mn/Ca)
-- 10)
text).
1(V/Ca)0
(V/Ca)corr
_ (V/Ca)measd
(V/Ca)measured
((Mn/Ca)
10)xx 0.6
0.6(see
(see
text).
Since
of VV in
in sediments
is 44 orders
Since the
the concentration
concentration of
sediments is
orders of
of
magnitude
calcite,
magnitudehigher
higherthan
thanthat
thatin
inforaminiferal
foraminiferal
calcite,the
thepotenpotenfor
exchange
between
the
two
phases
tial exists
exists for exchange between the two phases if
if
foraminiferal
is not lattice
foraminiferal vanadium
vanadium is
lattice bound. In sediments
sediments from
from
core
core EN066-17GGC,
EN066-17GGC, the
the bulk
bulk V
V content
contentisisrelatively
relativelyconstant
constant
with
with depth
depth (Table
(Table 5)
5) and
andshows
showsno
nocorrelation
correlationwith
with
foraminiferal
foraminiferalvanadium
vanadium(Figure
(Figure7),
7), which
whichvaries
variesconsiderably
considerably
downcore.
downcore.This
This suggests
suggeststhat
thatthe
thevanadium
vanadiumin
inforaminiferal
foraminiferal
calcite
calcite is
is aa closed
closedsystem
systemwith
with respect
respectto
tobulk
bulksedimentary
sedimentaryV
V
and
does
not
exchange
over
the
1
60-kyr
period
represented
by
and doesnot exchangeover the 160-kyrperiodrepresented
by
the
the core.
core.
Sensitivity
SensitivityAnalysis
Analysis
A
based on
A simple
simpletime-dependent
time-dependentmodel
model based
on the
the marine
marinemass
mass
balance
balancefor
for vanadium
vanadiumis
is used
usedto
toevaluate
evaluatethe
thesensitivity
sensitivityof
ofdisdissolved V
V to
solved
to changes
changesin
in the
theareal
arealextent
extentof
of anoxic
anoxicand
andsuboxic
suboxic
sediments
over time,
time, as
as well
and
sedimentsover
well as
as the
the other
otherimportant
importantsource
sourceand
sink
sink terms.
terms.
9C
•C
R +A50F0 A0F0 AaFa H
Vo'•- ==JR
+Aso
Fso
- Ao
Fo- Aa
Fa- JH
V0
(2)
where
is the
the ocean
of
whereV0
Vo is
oceanvolume;
volume;C
C is
isthe
theconcentration
concentration
ofvanavana-
672
67 2
HASTINGS ET
FT AL.: VANADIUM
HASTINGS
VANADIUM IN
IN FORAMINIFERAL
FORAMINIFERAL CALCITE
CALCITE
200
V/Ca (nmoVmol)
V/Ca
(nmol/mol)
0
0
0
150
150
ß
-i-
.,i-
E
100
lOO
20
20
10
10
'
'
'
'
I
4,
4,
10
10
40
40
30
30
I •,•
-i-
50
++
+ +
+
.4
0
20
w20
D)
ß
0
0
(1
+ ++
I
50
5O
i
i
100
1O0
i
I
0
+4-;o
i
150
+
0o
4-
+
0
30
30
V/Ca
V/Ca(nmol/mol)
(nmol/mol)
Figure 4.
V/Ca versus
Figure
4. Foraminiferal
Foraminiferal V/Ca
versus Mn/Ca
Mn/Ca for
for eastern
eastern
equatorial Atlantic
equatorial
Atlantic core
core EN066-17GGC.
EN066-17GGC.
+
0
40
40
(0
dium
F0,
flux
diumin
in seawater;
seawater;
Fo,Fa,
Fa,and
andF50
Fsoare
areequal
equalto
tothe
thevanadium
vanadium
flux
from
sediments,
respectively;
A0,
fromoxic,
oxic,anoxic
anoxicand
andsuboxic
suboxic
sediments,
respectively;
Ao,
Aa,
and
A50
are
equal
to
the
areal
extent
of
oxic,
anoxic,
Aa, andAso are equalto the areal extentof oxic, anoxic,and
and
suboxic
sediments;
R is
is the
the fiveddne
nverine flux
flux of
of vanadium;
vanadium;and
andJH
H
suboxic
sediments;
JR
is removal
Fe oxides.
is
removalby
by hydrothermally
hydrothermallyproduced
producedFe
oxides.An
An instaninstantaneous change
change is
is assumed
at tt == 00 using
seawater
taneous
assumedat
usingthe
thepresent
present
seawater
value
of
36
nM.
Removal
to
anoxic
and
oxic
sediments
and
valueof 36 nM. Removalto anoxicandoxicsediments
andby
by
hydrothermally derived
derived Fe oxyhydroxides
oxyhydroxides is modeled
modeled as
as a firstfirsthydrothermally
25
25
I
'
I
'
I
carbonate phase
plotted
versus
calendar
age
carbonate
phase
plotted
versus
calendar
agein
inthe
theuppermost
uppermost
50
equatorial
Atlantic
EN066-17GGC.
50 cm
cmof
ofeastern
eastern
equatorial
Atlanticcore
core
EN066-17GGC.
Corrected V/Ca
V/Ca values
values (see
(see text)
by
Corrected
text)are
areindicated
indicated
byplus
plussigns,
signs,
and
values
by
anduncorrected
uncorrected
valuesare
areindicated
indicated
by open
opencircles,
circles,for
forcomcomparison. Vertical
line
the
coreparison.
Verticaldashed
dashed
lineindicates
indicates
theglobal
globalmean
mean
coretop
determined
earlier
et
topvalue
valueof
of21.7
21.7nmol/mol
nmol/mol
determined
earlier[Hastings
[Hastings
etal.,
al.,
1996b].
1996b].
sented
sentedin
in the
theappendix.
appendix.
The
sensitivity
of
to changes
changes in source
The sensitivity
of[V]5
[V]swto
sourceand
andsink
sinkterms
terms
is
in
A0,
is illustrated
illustrated
in Figure
Figure8.
8.Increasing
Increasing
Aa, the
theareal
arealextent
extentof
of
anoxic sediments,
sediments, by
by a factor
anoxic
factorof 10
10 from
from 0.3% to
to 3%
3% of
of ocean
ocean
15
cn.
O5
o$
c•,w
V/Ca
a'•
Figure 6.
Figure
6. V/Ca
V/Ca values
values corrected
correctedfor vanadium
vanadiumin the
theMn
Mn
order
A
description
of the
orderreaction.
reaction.
A complete
complete
description
of
themodel
modelis
isprepre-
20
20
.2
- aE
2E
OD)
oo)
V/Ca
corrected
corrected V/Ca
V/C
,
sediments results
results in
in aa 12-nM
sediments
12-nM or
or 32%
32% decrease
decreasein
in vanadium
vanadium
©
concentration
after 50
50 kyr,
kyr, or
concentration
after
or about
abouthalf
halfaaglacial
glacialcycle.
cycle.
Increasing
A50,
the area
area of
of suboxic
sediments,
by aa factor
Increasing
Aso,the
suboxic
sediments,
by
factorof
of 55
from
fromthe
thecurrent
currentestimated
estimatedvalue
valueof 2.5%
2.5% to
to 12.5%
12.5%of
of the
theocean
ocean
bottom
increase
bottomresults
resultsin
in aacorresponding
corresponding
increaseof 22
22 nM
nM or
or62%
62%
after
after50
50 kyr.
kyr.
10
10
LU o
5
5
0
ß
0
I
,
20
20
I
40
,
Table 4.
Mn/Ca
from
Table
4. V/Ca
V/Caand
and
Mn/CaValues
Valuesfor
forC.
C.wuel!erstorfl
wuellerstiirfi
from
I
60
6o
80
V/Cacorr (nmol/mol)
V/Cacorr
(nmol/mol)
Figure 5.
V/Ca
Figure
5. Mean
Meancorrected
corrected
V/Ca for
for isotope
isotopestages
stages1,
1, 2,
2, 3,
3,
and 44 shown
fragmentation
in
and
shownas
asaafunction
functionof
offoraminiferal
foraminiferal
fragmentation
in
eastern equatorial
eastern
equatorialAtlantic
Atlanticcore
coreEN066-17GGC.
EN066-17GGC. Each
Eachisotope
isotope
stage
number
stage is
is indicated
indicatedby
bythe
thecorresponding
corresponding
numberinside
insidethe
the
open circle.
circle. Error
Error bar
bar for
the actual
range of
of
open
for stage
stage33 indicates
indicatesthe
actualrange
foraminiferal V/Ca
V/Ca values
values for
for that
foraminiferal
thatinterval,
interval.Increasing
IncreasingV/Ca
V/Ca
with increasing
is consistent
with
increasingfragmentation
fragmentationis
consistentwith
with earlier
earlier data,
data,
indicating that
that foraminiferal
V is
is sensitive
indicating
foraminiferal V
sensitiveto
to partial
partialdissodisso-
lution of
of tests.
lution
tests.
Eastern Equatorial
1 7GGC
Eastern
EquatorialAtlantic
AtlanticCore
CoreEN066EN066-17GGC
Sample
SampleDepth.
Depth,
cm
cm
2-6
2-6
6-11
6-11
25-30
25-30
30-35
30-35
86-90
86-90
V/Ca,
V/Ca,
nmol/mol
nmol/mol
119
Mn/Ca,
Mn/Ca,
Itmol/mol
gmol/mol
11.1
11.1
110
110
14.8
14.8
98
32.0
(243)
(243)
104
104
57.8
202
673
673
HASTINGS
EF AL.:
AL.: VANADIUM
CALCITh
HASTINGS ET
VANADIUM IN
IN FORAMINIFERAL
FORAMINIFERAL CALCITE
Table
Bulk Metal
Table 5.
5. Bulk
Metal Concentrations
Concentrationsfor
for Equatorial
EquatorialAtlantic
Atlantic
Core EN0661 7GGC
EN066-17GGC
Depth,
Mn,
Depth, CaCO3,'
CaCO3,1Mn,
%
cm
ppm
cm
%
ppm
10
40
75
53
53
%
%
V,
V,
ppm
ppm
Al,
AI,
516
516
0.86
0.86
34.6
34.6
2.11
546
546
2.34
2.34
77.0
77.0
4.44
4.44
measurable change
change within
within this
almeasurable
this interval.
interval.Postdepositional
Postdepositional
alterations including
terations
including partial
partial dissolution
dissolutionand
and Mn
Mn carbonate-overcarbonate-•vergrowth are
are not
not important
in this
growth
important in
this interval,
interval, as
as reflected
reflected in
in the
the
Fe,
Fe,
%
70
58
58
411
2.06
2.06
61.7
61.7
4.27
4.27
100
36
36
299
299
1.30
1.30
43.8
43.8
3.05
3.05
130
130
67
3.14
3.14
89.5
89.5
5.33
5.33
160
160
56
56
58
276
276
370
370
317
317
287
287
342
342
190
220
220
250
250
45
38
38
value
= 10)
di
value of
of 0.3%
0.3% to
to 3%
3% (relative.change
(relative•ehange
=
10) and
and the
the extent
extento•
suboxic
did not
not change
= 1),
suboxicsediments
sedimentsdid
change(relative
(relative change
change=
1), the
the
vanadium
concentration of
of seawater
vanadium concentration
seawaterwould
would be
be expected
expectedto
to
decrease
by
30%
over
35
kyr,
as
indicated
by
the
in
decreaseby 30% over 35 kyr, as indicatedby the asterisk
asteriskin
---
70.0
70.0
---
1.77
54.2
3.47
3.47
2.16
2.16
76.1
4.60
4.60
--
86.5
86.5
--
1I Percent
Percent carbonate
carbonate data
from
Curry
and
Lohmann
[1986].
data
from
Curry
and
Lohmann
[1986].
Because the
the riverine
Because
riverine input
input and
andhydrothermal
hydrothermalactivity
activity are
are
major terms
major
termsin
in the
themarine
marinevanadium
vanadiumcycle,
cycle,possible
possibletemporal
temporal
variability in
in these
variability
these processes
processesmust
must also
also be
beconsidered.
considered.
Changes
in
chemical
erosion
and
riverine
input
Changesin chemical erosion and riverine inputover
overglacialglacialinterglacial cycles
cycles are
interglacial
are not
not well
well constrained.
constrained.Recent
Recentcalculacalculations based
tions
basedon
on changes
changesin
in global
globalbicarbonate
bicarbonatefluxes
fluxesestimate
estimate
that chemical
chemical erosion
erosion at
at 18
that
18 ka
ka B.P.
B.P. was
wasonly
only 20%
20% greater
greaterthan
than
present-day values
values [Gibbs
present-day
[Gibbsand
and Kump,
Kump, 1994].
1994]. A
A 20%
20% increase
increase
by only
only 22 nM,
in chemical
erosion would
wouldincrease
increase[V]sw
[]5 by
in
chemicalerosion
nM, or
or
6%, relative
6%,
relative to
to present
presentconditions.
conditions.Doubling
Doubling the
the riverine
riverine
input, as
as predicted
by Froelich
Froelich et
input,
predictedby
et al.
al. [1992],
[1992], would
wouldresult
resultin
in aa
35%
increase
in
V
(12.5
nM)
over
50
kyr,
clearly
a
significant
35% increasein V (12.5 nM) over 50 kyr, clearly a significant
change (Figure
(Figure 8).
8). Riverine
Riverine flux
flux is
is assumed
to be
be constant
in
change
assumedto
constantin
the interpretation
the
interpretationof
of the
the foraminiferal
foraminiferaldata.
data.
Change
is one
of
Changein
in the
the rate
rateof
of seafloor
seafloorspreading
spreadingis
one indicator
indicatorof
variations in
in metalliferous
variations
metalliferoussediment
sedimentproduction
productionat
at hydrotherhydrothermal spreading
mal
spreadingcenters.
centers.Precise
Preciseestimates
estimatesof
of seafloor
seafloorspreading
spreading
rates indicate
rates
indicate that
that plate
plate motions
motionshave
have been
beennearly
nearly constant
constant
(±3%)
over the
the past
(_+3%) over
past 5
5 million
million years
years [Wilson,
[Wilson, 1993].
1993]. Plate
Plate
velocities averaged
averaged over
over shorter
shorter timescales
timescales of
of several
velocities
several to
to aa
dozen years
years agree
agree within
within _+5%
±5% to
to those
over the
the past
dozen
those over
past 33 Myr
Myr
[Gordon,
[Gordon, 1993].
1993]. Consequently,
Consequently,removal
removal by
by hydrothermally
hydrothermally
produced Fe
Fe and
produced
and Mn
Mn rich
rich oxides
oxidesis
is assumed
assumedto
to be
beconstant.
constant.
Figure 9.
Figure
9.
From 35
From
35 kyr
kyr B.P.
B.P. to
tothe
thepresent,
present,corrected
correctedV/Ca
V/Ca values
valuesare
are
constant in
constant
in equatorial
equatorialAtlantic
Atlanticcore
coreEN066-17GGC.
EN066-17GGC.Analysis
Analysis
of benthic
of
benthicspecies
speciesC.
C. wuellerstorfi
wuellerstorficonfirms
confirmsthe
the result
resultof
of no
no
foraminiferal fragmentation
fragmentation data,
data, which
which indicate
indicate no
no change
foraminiferal
changein
in
dissolution intensity.
intensity. Mn/Ca
Mn/Ca levels
levels are
are low
low (<30
(<30 •tmol/mol),
imoI/mol),
dissolution
and correlation
correlation between
between foraminiferal
Mn and uncorrected V
V is
and
foraminiferal Mn
poor
that a
a
poorover
overthis
thisperiod
period(r2
(r2 == 0.4;
0.4;Figure
Figure4),
4), demonstrating
demonstrating
that
Mn
carbonate
overgrowth
phase
is
not
important.
Mn carbonate overgrowth phase is not important.
Foraminiferal
Foraminiferal vanadium
vanadium data indicate that
that there
there was
was no
no measurmeasurable
in [V]5.
the
in
ablechange
changein
[V]sw.Consequently,
Consequently,
thechanges
changes
in the
theextent
extent
of reducing
by the
of
reducingsediments
sedimentspredicted
predictedby
themodel
modelare
areconstrained
constrained
by the
of the
±12%,
by
the standard
standarddeviation
deviation.of
themeasurement,
measurement,
_+12%,which
whichis
is
indicated by
by the
the stippled
region in
in Figure
indicated
stippledregion
Figure9.
9. The
The model
modelresults
results
indicate
indicatethat
that assuming
assumingno
no change
changein
in the
thearea
areaof
of suboxic
suboxicsedisediments,
the
areal
extent
of
anoxic
sediments
did
not
by
ments,the arealextentof anoxicsediments
did notincrease
increase
by
more
morethan
thanfivefold,
fivefold, or
or 1.5%
1.5% of
of the
theocean
oceanfloor,
floor,over
overthe
thepast
past
35 kyr.
kyr. This
This is
arrows
35
is shown
shownby
by the
theannotated
annotated
arrowsat
atyy == 11and
andxx ==
5.
5. Alternatively,
Alternatively, given
given aa constant
constantarea
areaof
ofanoxic
anoxicsediments,
sediments,
suboxic
are
by
suboxicsediments
sediments
arepredicted
predictednot
notto
tohave
havedecreased
decreased
bymore
more
than
0.5 times
than 0.5
times or
or enlarged
enlargedby
by more
morethan
than1.5
1.5 times
timesthe
the current
current
value.
Assumingaa current
current value
value of
of 2.5%
[Hastings and
value. Assuming
2.5% [Hastings
and
Emerson, 1995]
Emerson,
1995] this
this corresponds
correspondsto
to 1.3-3.5%
1.3-3.5% of
of total
totalocean
ocean
sediments.
Simultaneous
increases in
in both
sediments.
Simultaneous
increases
bothvariables
variablesmight
mightbe
be
expected. For
For example,
example, aa fivefold
increase in
in the
the area
expected.
fivefold increase
area of
of
anoxic sediments
constrains the
the change
in suboxic
anoxic
sedimentsconstrains
changein
suboxicsediments
sediments
from approximately
approximately 1I to
from
to 22 times
timesthe
thecurrent
currentvalue.
value.
Since
in
sedSincereal-world
real-worldchanges
changes
in the
theareal
arealextent
extentof
ofreducing
reducing
sed-
iments are
are not
another
iments
not likely
likely to
to be
beinstantaneous,
instantaneous,
anothermodel
model was
was
100
+
-I-
80
80
+
+
+
E60
+
60
Discussion
Discussion
To interpret
data, the
To
interpret the
the foraminiferal
foraminiferal data,
the model
model and
and V
V mass
mass
balance presented
presented earlier
earlier are
are used
used to
changes in
in the
balance
to constrain
constrainchanges
the
area
area of
of reducing
reducingsediments.
sediments.The
The change
changein
in the
the vanadium
vanadiumconconcentration
of seawater
that would
be predicted
35 kyr
kyr after
centrationof
seawaterthat
would be
predicted35
after an
an
instantaneous
change
instantaneous
changein
in the
theareal
arealextent
extentof
ofanoxic
anoxicand
andsuboxic
suboxic
sediments is
is illustrated
illustrated in
in Figure
sediments
Figure 9.
9. Since
Sincethe
the changes
changesin
in subsuboxic and
oxic
and anoxic
anoxicsediments
sedimentsare
arelikely
likely to
to be
becorrelated,
correlated,different
different
combinations of
of changes
1,
combinations
changesare
are shown.
shown.The
The modem
modernvalue
valueatatx=
x=l,
y=l
y=l isisindicated
indicatedby
byaasolid
solidsquare.
square.Using
Usingthe
themodem
modernvalues
values
estimated for
for the
the extent
estimated
extent of
of anoxic
anoxic and
and suboxic
suboxic sediments
sediments of
of
0.3%
0.3% and
and2.5%,
2.5%, respectively,
respectively,the
thepercent
percentchanges
changesin
in seawater
seawater
V
V concentration
concentrationare
are given
given in
in this
thiscontour
contourplot.
plot. For
For example,
example,if
if
the area
area of
of anoxic
anoxic sediments
sediments increased
increased tenfold
tenfold from
from the
the current
current
+,,I-
+
+
40
+
20
20
0
ß
0
0
,
ß
i
!
50
50
i
i
i
i
I
i
100 •
100
i
i
i
150
150
V/Ca (nmol/mol)
V/Ca
(nmol/mol)
Figure 7.
Figure
7. Solid
Solidphase
phasevanadium
vanadiumversus
versusforaminiferal
foraminiferalvanavanadium in
in eastem
dium
easternequatorial
equatorialAtlantic
Atlanticcore
coreEN066-17GQC.
EN066-17GGC.
HASTINGS
Er AL.:
AL.: VANADIUM
HASTINGSET
VANADIUMIN
INFORAMINIFERAL
FORAMINIFERALCALCITE
CALCITE
674
200
200
Asuboxic
A
suboxic x5
x5
150
150-
100
100a)
0
5050-
-
J river
J
river x2
x2
-T
x
*.-
x
Aanoxjc
A anoxic x5
x5
AanoxjcXlO
A anoxic x I 0
50
-50
00
40
20
60
80
100
100
time
time (kyr)
(kyr)
in the
concentrationinin seawater
seawateras
as aa function
function of
of time
Figure
Figure 8.
8. Percent
Percentchange
changein
the vanadium
vanadiumconcentration
time after
after an
an
instantaneous
fivefold
and
aafiveinstantaneous
fivefold(crosses)
(crosses)
andtenfold
tenfold(triangles)
(triangles)increase
increasein
in the
thearea!
arealextent
extentof
ofanoxic
anoxicsediments,
sediments,
fivefold
(circles),
fold increase
increasein
in suboxic
suboxicsediments
sediments
(circles),and
andaadoubling
doublingof
ofriverine
riverineinput
input(squares).
(squares).
created using
totoilluscreated
usingaa variable
variableinput.
input.This
Thismodel
modelisispresented
presented
illustrate the
ininthe
trate
the effect
effectof
ofgradual
gradualchanges
changes
thearea!
arealextent
extentofofsubsuboxic sediments.
oxic
sediments.Since
Since changes
changesin
in the
the areal
arealextent
extentof
ofanoxic
anoxic
sediments
result in
in relatively
sedimentsresult
relatively minor
minor changes
changesin
in [V],
[V]sw comcompared with
pared
with suboxic
suboxicsediments,
sediments,Aa
Aa is
isassumed
assumedto
to be
beconstant.
constant.
Changes
in the
Changesin
the area
areaof
of suboxic
suboxicsediments
sedimentsare
areproportional
proportionalto
to
10
'
9
9•
observed
changes in
in the
6180
observed
changes
thestacked
stacked
•5180SPECMAP
SPECMAPrecord
record
[Martinson
er al.,
[Martinson et
al., 19871.
1987]. Two
Two different
different solutions
solutionsare
areprepresented,
given an
an increase
in the
sented,given
increasein
the areal
areal extent
extentof
of suboxic
suboxicsedisedi-
8 •
ments by
by aa factor
ments
factor of
of 2x
2x and
and4x
4x during
duringthe
thelast
lastglacial
glacialmaximum
maximum
(LGM)
(Figure
1
Oa).
The
value
for
A50
at
other
times is
(LGM) (Figure 10a). The value for Aso at othertimes
is scaled
scaled
to the
of
to
the curve
curveshown
shownin
in Figure
FigurelOb.
10b.Concentrations
Concentrations
of vanadium
vanadium
in seawater
by stepping
in time
in
seawaterwere
were calculated
calculatedby
steppingforward
forward in
time using
using
the
the model
model described
describedearlier
earlier but
but reassigning
teassigningthe
the initial
initial condicondition
tion every
every 66 kyr.
kyr.
Foraminiferal V/Ca
V/Ca values
values limit
limit the
Foraminiferal
the changes
changesof
of [V]
[V]swwithin
within
the
the last
last35
35 kyr
kyr to
toless
lessthan
than±12%,
+12%,or
orabout
about±4
+4nM,
nM, equivalent
equivalent
to
to aa maximum
maximumglacial-interglacial
glacial-interglacialdifference
differenceof
of 24%.
24%. For
Forthe
the
7
6
5
4
•
+50%
3
scenario
in which
scenario in
which suboxic
suboxic sediments
sediments are
are doubled,
doubled, the
the
variability
variability reflected
reflectedin
in model-derived
model-derived[V]5
[V]sw is
is 33 nM
nM (8%),
(8%),
0
1
I
23 45
2
3
4
5
6
7
7
8
9
10
10
Relative
change in
in extent
Relative change
extent of
of anoxic
anoxicsediments
sediments
Figure 9.
Figure
9. Percent
Percentchange
changein
in the
thevanadium
vanadiumconcentration
concentrationof
of
seawater
predicted 35
change
seawaterpredicted
35 kyr
kyr after
afteran
aninstantaneous
instantaneous
changein
in the
the
areal
areal extent
extent of
of anoxic
anoxic and
and suboxic
suboxic sediments.
sediments. Units
Units for
for the
the x
x
and
y axes
and y
axesare
arechanges
changesin
in their
theirareal
arealextent
extentcompared
comparedwith
with the
the
modern
modern values
values of
of 0.3%
0.3% and
and2.5%
2.5%respectively.
respectively.The
Themodern
modern
value
at x=l,
x=I, y=l
value at
y=l isisindicated
indicatedby
bythe
thesolid
solidsquare.
square.The
The stippled
stippled
region corresponds
to the
region
correspondsto
theprecision
precisionof
of the
theV/Ca
V/Cameasurement
measurement
(±12%),
whichisisused
usedas
asaa proxy
proxyfor
for[V]sw.
[V]. Changes
(+12%), which
Changesin
in the
the
areal
over the
the past
areal extent
extent of
of reducing
reducingsediments
sedimentsover
past 35
35 kyr
kyr are
are
constrained
to this
constrainedto
thisstippled
stippledgray
grayregion.
region.
which
is within
Aso is
which is
within this
thismargin
marginof
of error.
error.For
For the
thecase
casewhere
whereAso
is
changes
by 99
expanded
by
a
factor
of
4,
model-derived
[V]
expandedby a factor of 4, model-derived[V]sw changesby
nM, or
the last
nM,
or 25%,
25%, during
during the
last 35
35 kyr,
kyr, which
which is
is larger
largerthan
thanthe
the
measurement error.
error. Given
Given aa variable
input for
measurement
variable input
for Aso
Aso based
basedon
on
changes in 6180,
VV data
constrain
the
changes
•5180,the
theforaminiferal
foraminiferal
data
constrain
theinincrease in
crease
in the area!
areal extent
extent of
of suboxic
suboxic sediments
sediments to
to no
no more
more than
than
aa factor
factorof
of 4,
4, equivalent
equivalentto
to10%
10%of
oftotal
totalocean
oceansediments.
sediments.
Previous reconstructions
of sediment
Previous
reconstructions of
sediment redox
redox conditions
conditions difdiffer in
of Cd
fer
in their
their conclusions.
conclusions. Based
Based on
on enrichments
enrichments of
Cd and
and U
U in
in
glacial Subantarctic
glacial
Subantarcticsediments,
sediments,Rosenthal
Rosenthaler
etal.
al.[1995]
[1995]sugsuggest that
gest
that higher
higherglacial
glacialproductivity
productivitymight
mighthave
haveincreased
increasedthe
the
areal extent
to 16%
areal
extent of
of reducing
reducing sediments
sediments to
16% during
during the
the last
last
glacial maximum,
twice the
the current
glacial
maximum, twice
currentvalue
valueof
of 8%.
8%. Other
Otherrecords
records
from the
the Sea
of Japan
Japan [Piper
[Piper and
from
Sea of
and Issacs,
Issacs,1995]
1995] and
andthe
the southsouth-
675
675
HASTINGS
Er AL.:
HASTINGSET
AL.:VANADIUM
VANADIUMIN
INFORAMINIFERAL
FORAMINIFERALCALCITE
CALCITE
(a)
(a)
60
60
A.
x
50
50- -
U)
ci)
x
x
Aso= 4x
4x at
at LGM
LGM
Aso=
0O
Aso= 2x
2x at
at LGM
LGM
Aso=
F
40 •'
40
X)cxx
30
30- -
:
:
XXx
x
:
:
:
x
ß
:...
:
:
-C
C)
x
20
20-
-
*0
00
10 -
ß
:
0
000.0* ox
o
o
o
:
ß
:
o
o
x
x
:X X X X X X
0ø',000090
000*00
0
40
20
0
0
60
60
80
80
100
100
120
120
time
(kyrBP)
time (kyr
BP)
(b)
I
1
I
I
I
fF
I
---I;
C
0
C-)
C
=
U-
0.5
0.5
4'
0
,
0
0
II
20
20
,
I
I
,
40
40
I
60
60
,
I
80
80
,
I
100
1 O0
,
I
120
120
time (kyr
time
(kyrBP)
BP)
Figure
changes for
for the
the areal
areal extent
of subFigure 10.
10. (a)
(a) Percent
Percentchange
changein
in[V]5
[V]sw relative
relativeto
to 36
36 nM,
nM, given
given gradual
gradualchanges
extentof
suboxic
by
and
at the
oxic sediments.
sediments.A0
Asoisisincreased
increased
byaafactor
factorof
of22(crosses)
(crosses)
and 44 (squares)
(squares)at
the last
lastglacial
glacialmaximum
maximumand
andis
is
scaled
for
scaledto
to the
theoxygen
oxygenisotope
isotopestratigraphy
stratigraphy
for the
theother
othertimes
timesusing
usingthe
thefunction
functionplotted
plottedin
in Figure
FigurelOb.
10b.
eastern Indian
eastern
Indian Ocean
Ocean [McCorkle
[McCorkle et
et al.,
al., 1994]
1994] also
also suggest
suggest
more reducing
more
reducingconditions
conditionsin
in glacial
glacial sediments.
sediments.The
The observed
observed
ical
ical and
and chemical
chemical alteration
alteration of
of the
the tracers
tracers used
used to
to make
make the
the
estimates.
estimates.
increase
in export
increasein
exportproduction
productionin
in the
theglacial
glacialSouthern
SouthernOcean,
Ocean,
based
on
several
radionuclide
proxies
and
coincident
with an
basedon severalradionuclideproxiesand coincidentwith
an
35 kyr,
kyr, global
35
global changes
changesin
in the
theareal
arealextent
extentofofsuboxic
suboxicsedisedi-
increase in
in lithogenic
increase
lithogeniciron
iron input
inputfrom
fromwind-blown
wind-blowndust
dust[Kumar
[Kurnar
be expected
to
et
al., 1995],
et al.,
1995], would
would be
expectedto
to drive
drive glacial
glacial sediments
sedimentsto
more
By contrast,
more reducing
reducingconditions.
conditions.By
contrast,the
the existence
existenceof
of aa Mn
Mn
spike
with aa pulse
spike in
in Panama
Panamabasin
basinsediments
sedimentscoincident
coincidentwith
pulsein
in
organic
organiccarbon
carbonis
is evidence
evidencethat
thatoverlying
overlyingwaters
watersin
in the
theeastern
eastern
equatorial
Pacific could
could not
not be
equatorialPacific
be suboxic
suboxicand
andmust
musthave
havebeen
been
[Yang
et
al.,
1995]
since
the
mechanism
to
preserve
oxic
oxic [Yang et al., 1995] since the mechanismto preservethe
the
Mn
Mn spike
spikerequires
requiresan
an oxic
oxic cap
cap [Calvert
[Calvertand
andPederson,
Pederson,1996].
1996].
These eastern
These
easternequatorial
equatorialPacific
Pacificsediments
sedimentsare
areparticularly
particularlysensensitive
sitive to
to potential
potentialchanges
changessince
sinceaa pulse
pulsein
inorganic
organiccarbon
carbonrerelated
1.a.tedto
to higher
higherproductivity
productivityseen
seenduring
during the
the last
last glacial
glacialwould
would
be expected
be
expectedto
to drive
drive them
themto
to aamore
morereduced
reducedstate.
state.These
Theseestiestimates
matesof
of sediment
sedimentredox
redoxconditions
conditionsare
aretypically
typicallyqualitative,
qualitative,
restricted
restrictedto
to local
local environments,
environments,and
andsubject
subjectto
topossible
possiblephysphys-
The
The foraminiferal
foraminiferalvanadium
vanadiumdata
data indicate
indicatethat
that over
over the
thepast
past
ments and
and sediments
by anoxic
ments
sediments overlain
overlain by
anoxic bottom
bottom water
water were
were
minimal.
If our
minimal. If
our understanding
understandingand
and assumptions
assumptionsabout
about the
the V
V
mass
massbalance
balanceare
are correct,
correct,this
thisexcludes
excludesthe
thepolar
polarnutrient
nutrientmodmodels
els as
asdescribed
describedby
by simple
simplebox
box model
modelsimulations
simulations[Knox
[Knox and
and
1984; Sarmiento
McElroy, 1984;
1984;
McElroy,
Sarrniento and
and Toggweiler,
Toggweiler, 1984;
Siegenthaler
and Wenk,
Siegenthalerand
Wenk,1984]
1984] as
as aa viable
viableexplanation
explanationfor
for
reduced
pCO2 during
reducedatmospheric
atmosphericpCO2
duringthe
the last
lastglacial
glacial period.
period.The
The
nutrient
global
nutrientdepletion
depletionmodel
model using
usingaa three-dimensional
three-dimensional
globalcircirculation
model is
is also
culation model
also not
not viable,
viable, as
as it
it results
resultsin
in bottom
bottom water
water
oxygen
depletion of
of 40
I.tM 02
02 [Sar,niento
oxygen depletion
40 IxM
[Sarrnientoand
andOrr,
Orr,1991],
1991],
leading
Indian
leading to
to anoxic
anoxic sediments
sedimentsin
in the
thesouthwestern
southwestern
Indian Ocean.
Ocean.
Although
difficult to
to quantify,
quantify, an
an increase
in the
the areal
Although difficult
increasein
areal extent
extent
of
of suboxic
suboxicsediments
sedimentswould
wouldbe
be expected
expectedto
toaccompany
accompanyan
anexexpansion
pansionin
in anoxic
anoxic sediments.
sediments.Both
Both of
of these
thesechanges
changesare
are large
large
676
676
HASTINGS ET
EF AL.:
AL: VANADIUM
CALCiTE
HASTINGS
VANADIUM IN
IN FORAMINIFERAL
FORAMINIFERAL CALC•
enough
enoughto
to be
bereflected
reflectedin
inthe
thevanadium
vanadiumforaminiferal
foraminiferalrecord,
record,
yet
change
yet there
thereis
isno
nodetectable
detectable
changein
inthe
theV/Ca
V/Cavalues.
values.
Other mechanisms
mechanisms to
to explain
pCO22 during
the last
last
Other
explain lowered
loweredpCO
duringthe
glacial
maximum
rely
on
alkalinity
changes
in
the
ocean.
The
glacial maximum rely on alkalinity changesin the ocean.The
polar
1989]
polar alkalinity
alkalinity hypothesis
hypothesis [Broecker
[Broecker and
and Peng,
Peng, 1989]
increases
increases the
the alkalinity
alkalinity of
of glacial
glacialage
ageCircumpolar
CircumpolarDeep
Deep
Water,
Water, which
which results
resultsin
in an
analkalinity
alkalinity increase
increasein
in Antarctic
Antarcticsursurface waters
reduced
pCO2.
face
watersand
andconsequently
consequently
reducedatmospheric
atmospheric
pCO 2.An
An
increase
increase in
in the
theorganic
organiccarbon/CaCO3
carbon/CaCO3ratio
ratioof
ofmaterial
material
changes in
in deep
by
changes
deepwater
water oxygen
oxygenlevels
levelsand
andcan
canbe
beconstrained
constrained
by
the data
the
dataset
setpresented
presentedhere.
here.Polar
Polarnutrient
nutrientdepletion
depletionscenarios
scenarios
require significant
oxygen reductions
reductions in
in bottom
require
significant oxygen
bottom waters
waters that
that
would have
have led
would
led to an
an increase
increase in
in the
the areal
areal extent
extent of
of anoxic
anoxic sedsed-
iments and
iments
and suboxic
suboxicsediments
sedimentsin
in parts
partsof
of the
theworld
word ocean.
ocean.The
The
foraminiferal vanadium
vanadium data
data indicate
foraminiferal
indicatesuch
suchchanges
changeshave
havenot
not
occurred
over the
based
occurredover
the past
past35
35 kyr.
kyr. Those
Thosescenarios
scenarios
basedon
onalkaalkalinity changes
in the
little or
or no
linity
changesin
the global
globalocean,
ocean,which
which require
requirelittle
no
change
with
changein
in deep
deepwater
wateroxygen,
oxygen,are
areconsistent
consistent
with the
theconstant
constant
V/Ca
V/Ca values
valuesobserved
observedin
in this
thisstudy.
study.
reaching
reachingthe
the sediments
sedimentswould
wouldincrease
increaseorganic-carbon-driven
organic-carbon-driven
dissolution
and
drive
up
the
[CO3=]
dedissolutionand drive up the [CO3=]with
witha acorresponding
corresponding
decrease
pCO2
creasein
in atmospheric
atmospheric
pCO2 [Archer
[Archerand
andMaier-Reimer,
Maier-Reimer,1994].
1994].
Appendix
Appendix
The
[Opdyke
The coral
coralreef
reefhypothesis
hypothesis
[Opdykeand
andWalker,
Walker,1992]
1992]relies
re}ieson
on
decreased
The model
in
decreasedcoral
coral growth
growth in
in shallow
shallowsurface
surfacewaters
watersduring
during glacial
glacial
The
model for
for sensitivity
sensitivityof
of the
thevanadium
vanadiumconcentration
concentration
in
times
with
a
corresponding
shift
of
CaCO3
deposition
to
the
seawater
to
changes
in
the
redox
state
of
sediments
is
based
times with a correspondingshift of CaCO3 depositionto the
seawaterto changesin the redox stateof sedimentsis basedon
on
deep
the oceanic
the
oceanic mass balance
balance for
for vanadium.
vanadium.
deepsea.
sea.These
Thesemodels
modelsrequire
requireless
lessor
or no
no deep
deepwater
wateroxygen
oxygen
reduction,
reduction,no
no additional
additionalanoxic
anoxicsediments,
sediments,and
andno
no significant
significant
increases
in the
increases in
the areal
areal extent
extent of
of suboxic
suboxic sediments.
sediments. The
The
foraminiferal vanadium
vanadium data
data presented
in this
foraminiferal
presentedin
this work
work support
support
explanations
explanationsthat
that require
requireminimal
minimal excursions
excursionsin
in the
theareal
arealexextent
tent of
of anoxic
anoxicor
or suboxic
suboxicsediments
sedimentsover
over the
the past
past35
35 kyr.
kyr.
Conclusions
Conclusions
Downcore
profiles of
of foraminiferal
in the
Downcore profiles
foraminiferal vanadium
vanadium in
the
Caribbean
Caribbeanand
and Atlantic
Atlantic basins
basinsreveal
reveal the
the utility
utility of
of V/Ca
V/Ca ratios
ratios
as
a
paleotracer
of
seawater
vanadium.
Postdepositional
efas a paleotracerof seawatervanadium.Postdepositional
effects,
fects,including
includingpartial
partialdissolution
dissolutionand
andprecipitation
precipitationof
of an
anininferred
ferredMn
Mn carbonate
carbonateovergrowth
overgrowthphase,
phase,can
cansignificantly
significantlyalter
alter
the
in
theoriginal
originalV/Ca
V/Ca values.
values.Such
Sucheffects
effectsmust
mustbe
beconsidered
considered
in all
all
efforts
efforts to
to interpret
interpret the
the data.
data.The
Theadvantage
advantageof
of examining
examiningaa
conservative
tracer such
conservative tracer
such as
as vanadium
vanadium is
is that
thatonly
only one
oneacceptacceptable
able core
core is
is required
requiredto
to yield
yield aaglobal
globalrecord
recordof
ofchanges
changesin
in
vanadium
The top
35
vanadiumconcentrations.
concentrations.
The
top 50
50 cm
cm(representing
(representing
35 kyr)
kyr)
of
such
a
core
in
the
eastern
equatorial
Atlantic
yields
of such a core in the easternequatorialAtlantic yieldssuch
suchaa
record.
record.
Using
Using foraminiferal
foraminiferal V
V data
data from
from the
theCaribbean
Caribbeanwhere
wherethe
the
Mn
phase controls
controls the
the VV content
of the
the tests,
Mn carbonate
carbonate phase
content of
tests, aa
minor
was applied
applied to
to the
the top
minor correction
correctionwas
top 50
50 cm
cm of
of the
theeastern
eastern
equatorial
to
for
equatorialAtlantic
Atlantic V
V measurements
measurements
to compensate
compensate
for the
the V
V in
in
this contaminant
phase. The
this
contaminantphase.
The corrected
correctedV/Ca
V/Ca profile
profile for
for this
this
interval reveals
interval
revealsno
no change,
change,indicating
indicatingthat
that within
within the
the error
errorof
of
the
the measurement
measurement (±12%),
(_+12%), seawater
seawater vanadium
vanadium levels
levels have
have not
not
changed
over the
changedover
the past
past35
35 kyr.
kyr. Applying
Applying an
an oceanic
oceanicmass
massbalbalance
ance for
for vanadium
vanadiumand
andaatime-dependent
time-dependentmodel,
model,this
thisconstant
constant
value
constrains
the
changes
in
the
areal
extent
of
value constrainsthe changesin the areal extent of anoxic
anoxicand
and
suboxic
suboxicsediments.
sediments.Assuming
Assumingno
no change
changein
in the
thearea
areaof
ofanoxic
anoxic
sediments,
the area
sediments,the
area of
of suboxic
suboxicsediments
sedimentsis
is predicted
predictednot
not to
to
have
have changed
changedby
by more
more than
than0.5
0.5 to
to1.5
1.5times
timesthe
thecurrent
currentvalue,
value,
which
to 1.3-3.5%
of the
which corresponds
corresponds
to
1.3-3.5% of
the total
total area
areaof
of ocean
oceansedsediments. This
This is
is the
iments.
the first
first effort
effort to
to quantify
quantifythe
the global
global change
changein
in
suboxic
over late
suboxic sediments
sediments over
late Pleistocene
Pleistocene climate
climate cycles.
cycles.
Alternatively, assuming
Alternatively,
assumingaa constant
constantarea
areaof
ofsuboxic
suboxicsediments,
sediments,
the areal
the
areal extent
extentof
of anoxic
anoxicsediments
sedimentsdid
did not
notincrease
increaseby
by more
more
than
than five-fold,
five-fold, or
or 1.5%
1.5% of
of the
theocean
oceanfloor
floorover
overthe
thepast
past35
35kyr.
kyr.
Using
Using aa numerical
numericalmodel
model where
where changes
changesin
in the
the extent
extentof
of subsubi8O, the
oxic
are
to
in
oxicsediments
sediments
areproportional
proportional
to changes
changes
in •5•O,
the
increase in
in suboxic
increase
suboxic sediments
sediments is constrained
constrained to no more
more than
than aa
factor of
of 4,
factor
4, equivalent
equivalentto
to 10%
10% of
of total
totalocean
oceansediments.
sediments.
Model simulations
presented to
to explain
in atmoModel
simulations presented
explain changes
changesin
atmospheric
pCO2
during
the
glacial
period
differ
in
their
predicted
sphericpCO2 duringthe glacial perioddiffer in their predicted
3C
+ A50F50 - A0F0 - Aa Fa - -'H
=
Vø•tt =
JR+
asoFso
- aoFo
- aaFa
- JH
V0
where V0
where
Vo is
is the
the ocean
oceanvolume;
volume; C
C is
is the
theconcentration
concentrationof
of disdissolved vanadium
vanadium in
in seawater;
F0,
solved
seawater;
Fo,Fa,
Fa,and
andF50
Fsoare
arethe
thevanadium
vanadium
flux
from
oxic,
anoxic
and
suboxic
sediments,
respectively;
flux from oxic, anoxicand suboxicsediments,
respectively;
A0,
Aa,
A50 are
are equal
equal to
to the
A
o, A
a, and
andAso
theareal
arealextent
extentof
ofoxic,
oxic,anoxic,
anoxic,
and suboxic
R is
is the
the riverine
and
suboxicsediments;
sediments'JR
riverineflux
flux of
of vanadium;
vanadium;and
and
H is
is removal
produced
iron
JH
removalby
by hydrothermally
hydrothermally
produced
ironoxides.
oxides.
Sinks are
(C):
Sinks
are proportional
proportionalto
to vanadium
vanadiumconcentration
concentration
(C):
F0
'h =eC
F
o ==j3C;
tiC' Fa
Fa =
= aC
aC. Jh
= eC.Here,
Here,B,
13,a,
Ix,and
and care
œaresolved
solved
for using
values, C
C=o
are
for
usingpresent-day
present-dayvalues,
t=o== 36
36nM.
nM.Constants
Constants
are
V0
= 1.37
cm3;
A ==3.61
xx1018
cm2;
Vo =
1.37xx1024
1024
cm3'A
3.61
1018
cm2'.1,.
Jr==5.4
5.4Xx108
108
mol
F0
nmol
cm2
Assumed
present
day
molyrt;
yr-l'and
and
Fo==0.12
0.12
nmol
cm-2yr*
yr-1.
Assumed
present
day
values are
= 2.5%
2.5% A
A and
and A
Aaa =
= 0.3%
values
areA50
Aso=
0.3%A.
A.
Solution is
Solution
is
C= --+
A
X exp (-7t)
7
where
where
R+A,F5
X=C1_0_!.
= Ao13+Aaa+e
R+AsoFso
Aofi
+V0
Aaa
+e X
Ct=
0 .
V0
- 7r
Vo
Vo
Acknowledgments.
sediment
cores
from
Acknowledgments. Ocean
Ocean
sediment
cores
fromthe
theSierra
SierraLeone
Leone
Rise
were graciously
graciouslyprovided
providedby
by Bill
the
Rise (EN066-17GGC)
(EN066-17GGC) were
Bill Curry
Curry and
andthe
Seafloor
Institution.
SeafloorSamples
SamplesLab
Lab of
of the
theWoods
WoodsHole
HoleOceanographic
Oceanographic
Institution.
Caribbean
108) was
was kindly
kindly provided
provided by
by the
Caribbeancore
core(TT-9
(TT-9108)
the Oregon
OregonState
State
University core
core library
University
library and
and funded
fundedby
by NSF
NSF grant
grant0CE94-02298.
OCE94-02298.
Samples
-4 were
Samplesfrom
fromCaribbean
Caribbeancore
coreCP600I
CP6001-4
werecheerfully
cheerfullysupplied
suppliedby
by
Larry
who
stable
isotope
values
and
LarryPeterson,
Peterson,
whoalso
alsoprovided
provided
stable
isotope
values
andbackground
background
information for
for the
information
the core.
core. Jack
Jack Fassett
Fassett at
at National
National Institute
Institute of
of Standards
Standards
and Technology
kindly
the enriched
50V
isotope spike
spike necesnecesand
Technology
kindlyprovided
provided
the
enriched
50Visotope
sary for
sary
for this
thiswork.
work.Louis
LouisLu
Luand
andTooba
ToobaDurrani
Durranihelped
helpedpick
pickmany,
many,
many of the
Critical reviews
reviews by
by Steve
Lea,
many
theforarninifera.
foraminifera.Critical
SteveCalvert,
Calvert,David
DavidLea,
Harry Elderfield,
Elderfield, Yair
Yair Rosenthal,
Rosenthal,Ross
RossHeath,
Heath, Ann
Ann Russell,
Russell,and
and Tamara
Tamara
Nameroff
Support
for
Nameroffgreatly
greatlyimproved
improvedthis
thismanuscript.
manuscript.
Support
forthis
thiswork
workwas
was
provided
16316 and
165providedby
byNSF
NSFgrant
grantOCE-91
OCE-9116316
andby
byACS-PRF
ACS-PRFgrant
grant25
25165AC8
A C8 to
to S.
S.Emerson.
Emerson.Kristin
Kristin Orians
Oriansand
andthe
theUniversity
Universityof
of British
British
Columbia provided
provided support
of
Columbia
supportduring
duringthe
thepreparation
preparation
ofthis
thismanuscript.
manuscript.
This
contribution
This is
is University
Universityof
of Washington
WashingtonSchool
Schoolof
ofOceanography
Oceanography
contribution
2151.
2151.
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