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Institutionen för naturgeografi
Examensarbete grundnivåNaturgeografi, 15 hp
Peloponnesian Stalagmites and Soda Straw Stalactites as
Climate Archives
Stable Isotopes in New Speleothem Material from Kapsia Cave, Peloponnese, Greece
Linn Haking
NG 632017
Förord
Denna uppsats utgör Linn Hakings examensarbete i Naturgeografi på grundnivå vid
Institutionen för naturgeografi, Stockholms universitet. Examensarbetet omfattar 15
högskolepoäng (ca 10 veckors heltidsstudier).
Handledare har varit Martin Finné, Institutionen för arkeologi och antik historia, Uppsala
universitet. Examinator för examensarbetet har varit Steffen Holzkämper, Institutionen för
naturgeografi, Stockholms universitet.
Författaren är ensam ansvarig för uppsatsens innehåll.
Stockholm, den 4 januari 2018
Steffen Holzkämper
Chefstudierektor
Abstract
This study presents results from stable isotope analyses of amodern stalagmite and
threesodastrawstalactites fromKapsiaCave, thePeloponnese,Greece.The resulting
valuesfromthestalagmiteareputintocontextof localmeteorologicaldata,aswellas
previous research fromKapsiaCave.Thepotential forusing soda straw stalactites as
complementary climate archives on shorter time scales on the Peloponnese is also
explored.Theisotopicvaluesinthestalagmiteconfirmastronglinktotheamounteffect
onanannualscale.Onaseasonalscale,variationsintheisotopicsignalcanbedetected
asaresultofi.e.increasedcaveairtemperatureinsummer.Thestableisotopevaluesin
the soda straw stalactites largely correspond to previous isotopic measurements in
Kapsia Cave. The trend of the isotopic carbon signal in two of the straws also
strengthens earlier theories suggesting a link to CO2 concentrations in the external
atmosphere. Soda straws are, thus, encouraged for use in future climate studies,
although the sampling method should be further explored. The results of this study
contributetoan increasedunderstandingofPeloponnesianspeleothemsinrelationto
environmental processes and new insights are suggested into the use of soda straw
stalactitesasclimatearchives.
KeywordsStableIsotopes;Stalagmite;SodaStrawStalactites;ClimateArchive;ClimateVariability;
TheAmountEffect;IsotopicFractionation;KapsiaCave;Peloponnese;Greece;Mediterranean
Tableofcontent
1. Introduction 1
2. Aimandresearchquestions 2
3. Background 3
3.1 Speleothemformation 3
3.2 Speleothemsasclimatearchives 4
3.2.1 Sodastrawstalactites 5
3.2.2 Stalagmites 6
3.3 Speleothemsandstableisotopesofcarbonandoxygen 7
3.4 Isotopicfractionationandequilibriumconditions 9
3.5 Setting 10
3.5.1 KapsiaCave 10
3.5.2 Localclimate 12
3.5.3 PreviousresearchinKapsiaCave 13
4. Materialandmethod 14
4.1Fieldwork 14
4.2Lab-work 15
5. Results 16
5.1StalagmiteGK02MODERN 16
5.2SodastrawstalactitesKS2,KS3andKS4 18
6. Discussion 19
6.1StalagmiteGK02MODERN 19
6.2SodastrawstalactitesKS2,KS3andKS4 22
7. Conclusion 25
Acknowledgements 26
8. References 26
8.1Electronicreferences 31
1
1.Introduction
Speleothems are calcareous cave deposits that can form and be preserved over long
periods of time making them interesting as natural climate archives. They offer the
possibility to study climate variability through several proxies, for example, oxygen-
andcarbon isotopes, traceelements (e.g.Mg,Sr,Ba),andpetrographicchanges in the
speleothemlaminea,whichcanbeusedincombinationwithpreciseradiometricdating
withUranium-Thorium.Proxyrecordsfromspeleothemscanbeofdifferentresolutions
fromsub-annualtomillennialandsometimescoverextensivetimeseries(upto105of
years)(Fairchildetal.2006).Speleothemstudiesmostlycovertropical-tosub-tropical
regionsoftheworld(e.g.Williamsetal.1999;Bakeretal.2007;Verheydenetal.2008;
Joetal. 2010;Boyd2015;Bergeletal.2017;Scroxtonetal.2017)andare important
complementsasterrestrialarchivesfromlowlatitudestostudiesone.g. icecoresand
oceansedimentscores(Bakeretal.2014).
Several speleothem climate studies have been conducted around the
Mediterranean (e.g. Bar-Matthews et al. 1996; Bard et al. 2002; Bar-Matthews et al.
2003;Frisiaetal.2003;Bakeretal.2007;Verheydenetal.2008;Fleitmannetal.2009;
Zanchetta et al. 2014; Surić et al. 2017). However, they are sparse on the Greek
peninsulaPeloponnese,wherespeleothemmaterialwasfirstpublishedonlyafewyears
ago (Finné et al. 2014). Before 2014 this area constituted a gap in the speleothem
climate research. Furtherwork fromFinné (Finné2014;Finnéetal.2015) aswell as
Boyd(2015),hascontributedwithvaluabledatafortheregion,andongoingwork(e.g.
Finnéetal.inpress)willnotonlycontinuetocontributetotheoverallclimatehistoryof
the Peloponnese and the Mediterranean in general, but also to local archaeological
research(e.g.Kordatzakietal.2016;Weibergetal.2016;Ntinou&Tsartsidou2017).
ThearchaeologyofthePeloponneseisextensiveandcomplexsocietiesstartedto
form as early as 8750BP (6800BC) at the beginning of the Neolithic revolution
(Demoule & Perlès 1993). Current archaeological research of the Peloponnese is
focusingonelucidatinghowpastsocietiesfrom8750BP(6800BC)to1650BP(AD300)
havedevelopedinrelationtoclimatevariabilityandaimstoincreaseourpossibilitiesto
interprethuman-environmentalinteractions(e.g.Weibergetal.2016;DoLPproject).
The overall objective of this study is to contribute to the speleothem climate
recordofthePeloponneseand,hence,increasetheknowledgeaboutclimatevariability
inthisregion.Inparticular,newmodernspeleothemmaterialconsistingofastalagmite
2
(formingwithinthelast5years)fromKapsiaCave,centralPeloponnese,isanalysedfor
stable oxygen- and carbon isotopes in order to investigate how isotopic signals in
speleothemscorrelatewith theexternalclimateof today. Incombinationwithashort
reviewon soda straw stalactite studies, three soda straws fromKapsia Cave are also
analysed for stable isotopes to explore whether this kind of speleothem has the
potentialtobeusedforfutureclimatestudiesonthePeloponnese.
Theresultsofthisstudyincreaseandstrengthentheknowledgeandpotentialof
the Peloponnesian speleothem climate record. It also brings some new insights into
how soda straw stalactites may be used for future climate studies in general, and
further contributes to our understanding of how meteorological data and isotopic
signalsinspeleothemscorrelateinKapsiaCaveinparticular.
2.Aimandresearchquestions
ThisstudyaimstocontributetothePeloponnesianspeleothemclimaterecordthrough
1)stableoxygen-andcarbonisotopeanalysisofnewspeleothemmaterialfromKapsia
Cave, as well as by 2) exploring possibilities in using soda straw stalactites for
Peloponnesian climate studies. The study further aims to relate the stable isotope
resultsfromthestalagmitetolocalmeteorologicaldataandexaminetherelationshipto
previousisotopicmeasurements,withtheambitiontoconfirmandstrengthenexisting
dataandbringmoreinsightintoclimatevariability.
Researchquestions:
- How do the isotopic values analysed in the speleothem material compare to
previousisotopicmeasurementsfromKapsiaCave?
- In what ways does the isotopic signal in the stalagmite respond to external
climatevariabilityandkineticfractionationinthecave?
- Whatpotentialexists inusingsodastrawstalactitesascomplementaryclimate
archives?
3
3.Background
3.1Speleothemformation
Speleothems are calcite deposits created from drip water in karstic caves, cavities
formedthroughdissolutionofcarbonaterockssuchaslimestone(CaCO3)anddolomite
(CaMg(CO3)2). The process of speleothem formation (fig. 1) starts as surface water
percolatesthroughsoilrichincarbondioxideduetorespirationofplantsanddecayof
organic matter, creating acidic water (carbonic acid (H2CO3)). As the acidic water
reaches theepikarst (azoneof fissuredbedrockunderlying thesoilzone) itdissolves
the carbonate bedrock, which in turn makes the calcium concentration rise in the
solution.The calcium-saturatedwater continues through fractures in theporous rock
anddescendsintothecave.Asthecarbondioxidepressure(pCO2)islowerinthecave
than inthesoil-andepikarstzone,degassingofcarbondioxideoccursasthesolution
reachesthecave.Thiscausescalcitedeposition,initiatingtheformationofspeleothems
(Ford&Williams2007;Fairchild&Baker2012).
Figure1.Theprocessofspeleothemformation(createdbyauthorafterFairchildetal.2006).
4
Speleothemsoccurinseveralsizesandshapes(fig.1),forexampleasflowstones,
stalactitesandstalagmites.Flowstonesformaswaterflowsdownthecavewallsandon
the floorcreating layersofcalcite film, sometimesalsohanging likecurtains fromthe
ceiling and wall. Stalactites start as soda straws (thin tubular speleothems) hanging
fromtheceiling,whichwithtimegrowsinlengthandthickness,whilestalagmitesbuild
up from the cave floor. Speleothems growing from the ceiling and the floor may
eventuallymeetandformacolumn(Ford&Williams2007).
3.2Speleothemsasclimatearchives
Even thoughspeleothemshavebeenstudied forover40years it isduring the last20
yearsthattheiruseasclimatearchiveshasincreasedrapidly.Thisincreasecanmainly
betracedtoimprovementsoftheradiometricUranium-Thoriumdatingmethod(U-Th
dating). By calculating the disequilibrium between the parent isotope 234U and its
daughterisotope230Th,thistechniquehasthestrengthtoprovideprecisedatingtothe
speleothemlaminae,upto500,000yearsback intime(Doraleetal.2004;Fairchild&
Baker2012).
Todayspeleothemsarewidelyusedasclimatearchivesthankstothepotentialof
providing detailed time series using U-Th dating as well as counting of regularly
forminglaminae.Inaddition,speleothemshavethecapabilitytogrowcontinuouslyfor
hundreds of thousands of years, thanks to the sheltered cave environment, and
preserveaclimatesignalwithintheirrobuststructure.Asaterrestrialclimatearchive,
speleothemsaswellasicesheetsprovideclimatedatacomparabletootherarchiveslike
ocean sediment cores, covering extensive time periods. The possibility of precise
independentdating,however,iswhatmakesspeleothemsstandoutasaclimatearchive
(McDermott2004;Fairchildetal.2006;Fairchild&Baker2012;Bakeretal.2014).
Proxiesthatarecommonlystudiedinspeleothemsarestableisotopesofcarbon
(δ13C) (e.g.Breecker2016) andoxygen (δ18O) (e.g.McDermott2004; Lachniet2009),
trace elements such as Magnesium (Mg), Strontium (Sr) and Barium (Ba) (e.g.
Desmarchelieretal.2006),aswellasgrowthratesandthicknessoflaminae(e.g.Frisia
et al. 2003; Tan et al. 2006). Though these proxies may be studied to provide an
external climate signal, variations in the depositional environment, such as
temperature, CO2 concentrations, humidity and air circulation in the cave,may affect
thisconnection(seesection3.3and3.4forfurtherdetails)(Fairchildetal.2006).
5
3.2.1Sodastrawstalactites
Sodastrawstalactitesare thevery first
state in the formation of the more
robustconicalstalactites(StPierreetal.
2009). The name soda straw originates
from the tubular shape of this
speleothemresemblingadrinkingstraw
(Desmarchelier et al. 2006). Like all
speleothems, soda straw stalactites
form from supersaturated drip water.
As the water enters the cave and
degassing of CO2 occurs, calcite
precipitates from the drop, which is
hanging from the cave ceiling. Due to
gravity, the drop eventually falls,
leaving a ring of calcite from where it
was hanging. As the straw in this
manner builds towards the cave floor,
thedripwaterwillmoveinthecentreof
theformingtube,increasinginsupersaturation,depositingasmalleramountofcalcite
in its inner canal and a greater amount at the tip as a ring. Because of this calcite
deposition,sodastrawsmanytimesdemonstratehorizontalbandingfrom0.05–0.5mm
thick,interpretedasannuallaminae(fig.2)(Moore1962;Huangetal.2001;Pauletal.
2013). The average diameter of soda straws normally measures around 5mm. The
thicknessof thetubewalls isusually100-300μmat thetipand increasestowardsthe
root,decreasingthewidthof its innercanal.Calcitegrowthbecomes lateralwhenthe
central canal of the straw gets blocked and, thus, begins to form a conical stalactite
(Baldini2001;Fairchild&Baker2012).
Although it is not uncommon to find straws over a metre in length they are
usuallynot longer thana fewdecimetresowing to their fragility (Desmarchelieretal.
2006; Fairchild & Baker 2012). It is commonly believed that soda straws form and
remain intact fora relatively limited timeperiodestimated torangeata fewdecades
butpossiblyuptoacentury.However,growthatthesamepositionmaycontinueafter
Figure 2. Formation and structure of a banded sodastraw stalactite with a suggested sample span forfragments vs. powder (created by author afterPaul et al. 2013, original published inInternationalJournalofSpeleology).
6
breakage(Williamsetal.1999;StPierreetal.2009;Fairchild&Baker2012).Growth
ratesvarygreatly,butcanbeasfastas40mmperyear(Joetal.2010).
Becauseofthefragilenatureofsodastraws,theyhavemanytimesbeenavoided
for paleoclimate research (Desmarchelier et al. 2006) and, thus, the supply of such
studiesislimited.Still,manyrelevantareasarecovered:dating(e.g.StPierreetal2009;
StPierreetal2012),growthrateandstructure(e.g.Moore1962;Baldini2001;Perrette
&Jaillet2010;Pauletal.2013),traceelements(e.g.Huangetal.2001;Desmarchelieret
al. 2006), and stable isotopes (e.g. Baskaran & Krishnamurthy 1993; Williams et al.
1999;Woo etal.2005). Studies on short-term climate variability and climate change
overthepastcenturyareanimportantstepinunderstandingthecorrelationbetween
stableisotopesinspeleothemsandtheexternalclimate.Thisisanecessarycomplement
topaleoclimateresearchandbecauseanalysesforbothisotopesanddatingtodayallow
small sample size, soda straws stand a potential candidate for this kind of research
(McDermott2004;Wooetal.2005;Fairchildetal.2006;Pauletal.2013).
3.2.2Stalagmites
Stalagmites are used to a great extent in paleoclimate research. Among the climate
proxiesnormallystudiedinstalagmites,morphologyandpetrographycanbeaphysical
indicationtoclimatevariability(Bakeretal.2014).Laminaethicknessandcolourmay,
forexample,provideaninsightintochangesinexternaltemperature(Frisiaetal.2003).
Changesindriplocationandindriprates,largelycontrolledbyrainfall,canbeseenin
thegrowthgeometryandporositiesofthestalagmite(Genty&Quinif1996;Frisiaetal.
2003;McDermott2004;Fairchildetal.2006).Tanetal.(2006)alsodemonstratedthe
possibility of tracing long-term climate changes from the growth structure and
thickness of stalagmite lamination. Although they emphasise that stalagmite laminae
and its sensitivity to the external climate may differ greatly between individual
specimens,theusageofstalagmitesbeforeotherspeleothemsisstillencouraged(Tanet
al.2006).
7
3.3Speleothemsandstableisotopesofcarbonandoxygen
Naturallyoccurringstableisotopesarevariationsofthesameelement,butthenumber
ofneutrons in theatom’snucleidiffersandconsequently constitutesadifferentmass
weight.Thisweightdifferencemaycausephysicalseparationofthedifferentisotopes,
socalledisotopicfractionation,forexamplewhenelementsaretransferredbetweenthe
reservoirsoftheEarthsystemdrivenbysolarenergy.Therelativeabundanceofheavy
andlightisotopesineachreservoirisdependentonthefavouredtransferofoneisotope
overtheotherasaresultofisotopicmassaswellastemperature.Thiscreatesaratioof
heavytolightisotopethatcanbemeasuredandisreportedinrelationtoasetstandard
(v-SMOW:ViennaStandardMeanOceanWater)(Sharp2017).
Theratioofstableoxygenisotopesincarbonatesisdefinedbytheformula:
δ18O‰V-PDB(ViennaPeeDeeBelemnite)=(Rsample/Rstandard-1)×1000whereR=18O/16O.
Similarly,theratioofstablecarbonisotopesincarbonatesisexpressedas:
δ13C‰V-PDB(ViennaPeeDeeBelemnite)=(Rsample/Rstandard-1)×1000whereR=13C/12C
(e.g.Rozanskietal.1993).
The most common stable isotopes that are analysed in speleothems for
paleoclimatological purposes are oxygen and carbon. In nature, oxygen is normally
foundwith8protonsand8neutronsinitsnuclei(16O–abundance:99.76%),whilethe
most common formof naturally occurring carbon contains 6 protons and6 neutrons
(12C–abundance:98.89%).Theheavier isotopesof theseelementsoccurwithoneor
two more neutrons forming: 17O (abundance: 0.04%), 18O (abundance: 0.2%), 13C
(abundance:1.11%)and14C(radioactive).Amongthese,18Oand13Careusedforstable
isotopeanalysisincarbonates(Sharp2017).
Theisotopicsignalinthecavedripwater,capturedwithinthegrowthlaminaeof
speleothems,canunderequilibriumconditionsoriginatefrommeteoricwaterand,thus,
climate-regulatedprocessesonthesurfacecontrolthe18Oabundanceinrelationtothe
set standard. As a simplified example, a warmer climate with high solar energy
increasesoceanwaterevaporationallowingmoreoftheheavieroxygenisotopes(18O)
togetintotheatmosphere.Inturn,heavierisotopesarefavouredduringcondensation,
causing isotopic enrichment with increasing condensation temperature (the
condensation effect). Consequently, meteoric precipitation will hold a high
concentrationoftheheavierisotope18O,eventuallycausinggroundwatertobeenriched
in 18O and, thus, to display relatively enriched δ18O values.This relationship between
8
temperature at the ocean water source and 18O is known as the ocean source effect
(Dansgaard1964;Williamsetal.1999;Sharp2017).Examplesoffurtheralterationsof18Omayoccuraccordingto theamounteffect,whereδ18Oofprecipitation is inversely
related to precipitation amount, or the seasonal effect,where δ18O of precipitation is
more depleted in winter. The distance between precipitation and its source, the
continental effect, also has an impact on δ18O, as the abundance of 18Owill decrease
furtherfromthesource(Rozanskietal.1993;Williamsetal.1999).
The amount of 13C that gets transported into the groundwater is partly
controlled by CO2 concentrations in the atmosphere. In an article from Baskaran &
Krishnamurthy(1993),sodastrawstalactites,conicalstalactitesandstalagmiteswere
analysed for stable isotopes to determine the influence of atmospheric CO2 in calcite
cavedeposits.Theyargued that soda strawsdated to the last century recordedmore
enrichedδ13Cvaluesclosertopreindustrialtimes(anaveragearound−5.9‰(v-PDB)
inAD1920)andmoredepletedvaluestowardsthetipofthestrawdepositedinrecent
times (an average around−8.2‰ (v-PDB) in AD1990), which was interpreted as a
resultofglobalindustrialemissionsofCO2.Williamsetal.(1999)aswellasWooetal.
(2005)confirmthecorrelationbetweenmoreenrichedδ13Cvalueswithdistancefrom
thetipinmodernsodastraws.
Consequently,higherconcentrationof13Candmoreenrichedδ13Cvaluesindrip
wateraregeneratedwhenCO2concentrationsarelowintheatmosphere,forinstance,
on longer time scales during periods of colder climate (glacial conditions) when
vegetationisforcedtoabsorbeventheheavierCO2molecules(13CO2).Otherfactorsthat
affect δ13C in speleothems are photosynthesis in C3versus C4 plants, microbiological
processesandhumanlanduse(Wooetal.2005;Ford&Williams2007;Sharp2017).
Hence,theδ18Osignal incavedripwatercanbeinterpretedasanindicatorfor
changes in thehydrological cycleandpropertiesofprecipitation, suchasamountand
temperature,whiletheδ13CsignalisrelatedtoatmosphericCO2,vegetationcoverand
biological activity in the soil zone (Williams et al. 1999; Woo et al. 2005; Ford &
Williams2007;Sharp2017).
9
3.4Isotopicfractionationandequilibriumconditions
Eventhoughtheoxygenandcarbonisotoperatioincavedripwateroriginatesfromthe
externalenvironment,thisclimatesignalmaybecompromisedifthespeleothemdoes
notdepositin,ornear,equilibrium.EquilibriumreferstothestatewhereHCO-3andCO2
ofthecavedripwaterremainsunfractionatedduringcalciteprecipitation(Hendy1971;
Mickleretal.2004;Sharp2017).
SincetheworkofHendy(1971),theprocessesthatimpactisotopicfractionation
haveremainedanongoingdebate.Inhisarticle,Hendydiscussespossiblekineticeffects
onthedripwateras itentersthecave,causingcalcitetoprecipitate indisequilibrium
withitsparentwater,possiblycompromisinganyclimatesignal.Processesthatcanlead
to enriched isotopic values compared to equilibrium are, for example, (1) rapid
degassingofCO2ifpCO2inthedripwatersolutionismuchhigherthanpCO2inthecave
atmosphere,enrichingbothδ18Oandδ13C,aswellas(2)evaporationofthedripwaterif
the relativehumidityof the cave is low, causingδ18O in the solution tobecomemore
enriched(Hendy1971).
Subsequentstudieshavefurtherexploredthisconcept(e.g.Bar-Matthewsetal.
1996;Mickleretal.2004;Dietzeletal.2009;Lachniet2009;Tremaineetal.2011;Stoll
et al.2015). Mickler et al. (2004) examined kinetic fractionation and equilibrium in
modern speleothems in relation to contemporary climatology and groundwater
chemistry.Althoughmost speleothemsat thecavesitewereexpected todepositnear
equilibrium because of a stable depositional environment and high humidity, their
results showed that especially δ18O values were far from what they predicted. They
argued that several fractionating processesmust have acted on the dripwater since
isotopicvalueswerebothenrichedanddepletedindifferentplacesinthecave.Mickler
et al. (2004) concluded that enriched isotopic values were seen close to the cave
entrance where stronger air ventilation lowered the CO2 concentrations and caused
increaseddegassingofCO2inthedripwater,aswellasincreasingtheevaporationdue
toamorevariedhumidity.Lateron, the studyofTremaineetal. (2011)also showed
that a linear enrichment in calcite δ13C could be detectedwith closer distance to the
caveentrance.Mickleretal.(2004)furtherarguedthatrapidorlargevariabilityinrates
ofcalciteprecipitationcouldhaveadepletingeffectonδ13C,butalsoenrichδ18O.
Alterationof the δ18Omay also occur according to the cavetemperatureeffect,
wherefractionationofthedripwateroccursasaneffectofthecaveairtemperatureby
10
−0.24‰per °C increase in cooler temperatures (around 10°C), and−0.22‰per °C
increaseintemperaturesaround20°C(Friedman&O’Neil1977;Williamsetal.1999).It
has been suggested, however, that the cave temperature effect is largely
counterbalanced by the condensation effect in the atmosphere causing enrichment of
δ18O by 0.2-0.3‰ per °C. This is especially evident on longer time scales since a
warming of the atmosphere also will lead to warming of the cave air over time
(Williams et al. 1999; Finné et al.2014).Williams et al. (1999) argued that the cave
temperatureeffectislikelytobecomemoredominantwithincreaseddistancefromthe
moisturesource.
Itisgenerallybelievedthatpaleoclimaterecordsfromspeleothemsshouldonly
be considered reliable if modern calcite precipitation occurs in or near equilibrium,
whichistobedeterminedbysite-specificmonitoring(e.g.Mickleretal.2004;Dietzelet
al.2009; Lachniet 2009; Tremaine etal.2011).Nevertheless, it is acknowledged that
themanydifferentfractionatingprocessesrarelyofferperfectequilibriumdepositionof
calcite, and that the existent of such a state is highly questionable. Although this
complicates the possibility of interpreting an isotopic signal in speleothems, external
climate signalsmay still be retrieved (Sharp 2017). If, however, kinetic fractionation
occurs,complementarystudiesareneededtofurtherinvestigatetheprocessesbehind
theobserveddisequilibrium inorder toobtainareliable interpretationof the isotope
signal(e.g.Lachniet2009;McDermottetal.2011).
3.5Setting
3.5.1KapsiaCave
KapsiaCave(N37.623°,E22.354°), centralPeloponnese,Greece,(fig.3)liesbeneath20-
30mofTriassic-EoceneGavrovo-Tripolitzazonelimestonebedrockandisstretchingfor
about200m.It is locatedontheMantineaPlainat thebaseof theMainaloMountains.
Abovethecave,patchesofsoil,exposedbedrockanddeadjunipertrunks,showthatthe
vegetation is sometimes subject to burning (last noted in AD1997). Further, the
vegetationiscomprisedof2mhighoakshrubs,grassspecies,LamiaceaeandEuphorbia.
KapsiaCavehasanaturalentranceandanartificialentrance,constructedin2004,both
about700ma.s.l. Since2010partsof the cave areopen to tourists.Themeanannual
temperature measured over the last 3.5 years is 11.9°C ±0.52°C and mean annual
11
relativehumidity is≥95%.Anunusually lowrelativehumidityof89%wasmeasured
duringthewinterof2012(Finnéetal.2014;Finné2014).
The many varied and impressive speleothems in Kapsia Cave (stalactites,
stalagmites,flowstones,curtainsetc.)arepartlycoveredbyalayerofclay,indicatinga
high-watermark from flooding events occurring both in the distant past (e.g. 500BC,
70BC, andAD450) andmore recently (last noted in AD2001). Low-lying parts of the
cavehavemeter-thickdepositsofclaysuggestingrepeatedflooding.Thisisalsoevident
from a previous speleothem study in Kapsia Cave by Finné (2014), where a sliced
stalagmite showed clayhorizons in its laminae.These floodingshaveoccurred as the
drainagecapacityof5sinkholes(oneadjacent to thenaturalentranceof thecave)on
theMantinea Plain has been exceeded by the surfacewater input (Finné etal.2014;
Finné2014).
Though no systematic excavations have been made so far, traces from many
archaeological periods have been identified in Kapsia Cave. Undated human remains
from50individualsofallagesarescatteredinthecave,aswellastracesofhumanmade
fires,whichdatetotheNeolithic(6500-3000BC).It isstilldiscussedwhetherthecave
wasusedasaburialgroundorifthesepeoplewerevictimsofafloodingevent(Finnéet
al.2014 and references therein). Further, artefacts from the Hellenistic period (323-
31BC) and the 4th-6th century AD have been found deep in Kapsia, among the things
somebronzecoinsandfibulaefromthe2ndhalfofthe6thcenturyAD(Finnéetal.2014).
Figure3. LocationofKapsiaCaveontheGreekpeninsulaPeloponnese (afterFinné2014).
12
3.5.2Localclimate
Meteorological data from AD2010 to 2017 (fig. 4) has been collected from a
meteorological station in Tripoli (N37.509°, E22.418°, 10 km south of Kapsia, 646m
elevation). Previousmeteorological data, also displayed in figure 4,was presented in
the study by Finné (2014), which likewise was collected from a station in Tripoli,
although a different one. The meteorological data indicates a characteristic
Mediterraneanclimatewheresummersarehotanddryandwintersaremildandwet.
Themeanannual temperaturebetweenAD1980-2004andAD2010-2016combined is
13.7°C±0.4°Cwithaslightlycoldermeantemperature in themostrecentperiod.The
meantotalprecipitationforthewetseason(ONDJFMA)betweenAD1980and2017is
around580mm.Duringthewetseason,70-80%oftheyearlyamountfalls(Dotsikaet
al.2010). The limited amount of rainfall in the dry season is commonly occurring as
heavy rain showers, which is clear when going through the monthly meteorological
reports during the last seven years. In earlier studies (e.g. Finné et al. 2014; Finné
2014), the contribution of dry season (MJJAS) precipitation to the karstic aquifer has
been considered to be negligible since these rain showers cause fast runoff and no
significant percolation of rainwater into deeper soils occur. Therefore, the cave drip
waterinKapsiaisassumedtoprimarilyoriginatefromwetseasonprecipitation(Finné
2014);hencethisstudyisbasedonthesamepremises.
Figure4.AnnualwetseasonprecipitationdatacompiledfromFinné(2014)andTripoliMeteosearch.
13
3.5.3PreviousresearchinKapsiaCave
EventhoughspeleothemsfromseveralcountriesaroundtheMediterraneanhavebeen
analysed for paleoclimate research since many years back (e.g. Bar-Matthews et al.
1996;Bardetal.2002;Bar-Matthewsetal.2003;Frisiaetal.2003;Bakeretal.2007;
Verheydenetal.2008;Fleitmannetal.2009),noextensivestudieshadbeenconducted
on thePeloponneseuntil2009whenKapsiaCaveandGlyfadaCave firststarted tobe
monitored for a PhD project by Martin Finné (2014). By establishing the first
stalagmite-basedrecord for thePeloponnese, thisproject, in2014,couldpresentnew
data on changes in the local environment covering a period from 2900 to 1120BP
(950BCtoAD830),aswellasregionalclimatechanges.Periodswithwetterclimatethan
averagewereidentified2800,2650,2450,2350-2050,1790-1650,and1180BPthrough
stableoxygenisotopevariations(δ18O),whichcontributedtotheoverallpictureofthe
paleoclimateof theMediterraneanaswell as to archaeological research in the region
(e.g. Weiberg et al. 2016; DoLP project). Variations in stable carbon isotopes (δ13C)
couldfurtherbeassociatedwithbiologicalactivityandlocalhumanlanduse(Finnéet
al.2014;Finné2014).
Stable isotopeanalyseswerealsoconductedforthelaminatedmoderntopofa
stalagmite (GK02) from Kapsia Cave. Lamina counting suggests that the top formed
from the 1980’s until collection in 2009. The topwas analysed for stable isotopes at
sub-annual resolution. These high-resolution δ18O valueswere binned into individual
years and an annual averagewas calculated. These annual average δ18O valueswere
then correlated to the total amount ofwet season rainfall (Finné 2014). This data as
well asmonitoringofKapsiaCave fromSeptember2009 toMarch2013has revealed
thatdripwater is supersaturated all year aroundanda strong seasonal variability in
driprate.Thereisalsoarelativelystrongcorrelationbetweenprecipitationamountand
variationsinδ18O,i.e.theamounteffect,whenconsideringalagof1-2years,i.e.thetime
ittakesforwatertopassthroughtheaquifer.Thisisseenasdepletedδ18Ovalueswhen
rainfall increases during wet season (Finné 2014). A correlation between δ13C and
rainfallhasnotbeendetectedinthemodernlaminaeofGK02,noristhereacorrelation
inδ18Oandδ13Ctosurfacetemperature(Finné2014).
Although the risk of kinetic fractionation has been noted to increase since the
openingoftheartificialentrancein2004(Finné2014),inaccordancewiththestudyof
Mickleretal.(2004)andTremaineetal.(2011),calculationsindicatethatspeleothems
14
inKapsiaCavearelikelytodepositnearequilibrium(Finnéetal.2014;Finné2014).
Further climate studies for the Peloponnese and Kapsia Cave, using both past
andrecent timeseries, canhelp toprovidemoreknowledgeon thecorrelationof the
externalclimateandisotopicsignalscapturedwithinspeleothems,aswellasknowledge
ofkineticeffects. Inthisway,correlationsso farobservedcanhopefullybeconfirmed
andstrengthenedand,thus,provideastrongerpaleoclimaterecord(Finné2014).
4.Materialandmethod
4.1Fieldwork
Forthisstudy,fieldworkwascarriedoutduringonedayonthe25thofSeptember2017,
inKapsiaCave, central Peloponnese.The initial objectivewas to cleanoutpreviously
installed monitoring equipment and to collect an actively growing stalagmite
(GK02MODERN,acontinuationofstalagmiteGK02 collected in2009)thatwasdepositing
onaplasticfilmontopofadripsensorplacedinabucketsinceMarch2013(fig.5a&
5b).Unfortunately, the installationhad fallenand,hence, theonlypresent calcitehad
formedontheartificialbasebeneaththefallensensorandbucket.Thestalagmitewas,
nevertheless, collected for furtheranalysis.However, thestartdateof its formation is
unknown.
Figure5.a)SamplesiteforstalagmiteGK02MODERNandlocationofpreviouslysampledsodastraws(KS2,KS3andKS4)inKapsiaCave(afterFinnéetal.2014).b)InstallationfortheformationofGK02MODERN(Finné2014).
15
In addition, the positions of three previously collected soda straws were
analysed (KS2, KS3 and KS4). They had been noted to actively drip at the tip and
seeminglydepositingcalciteunderneathuponcollection.Thiscouldalsobenotedinthe
field,andsothesethreestrawswereselectedforfurtheranalysesinthisstudy.
Point measurements of temperature (12.9°C) and relative humidity (96%)
duringthefieldworkfallswithintherangeofearliermeasurementsfrommonitoringof
thecavebetween2009-2013.
4.2Lab-work
Both the stalagmite (GK02MODERN) and the three soda straw stalactites (KS2, KS3and
KS4) were prepared for stable isotope analysis in the lab of the Physical Geography
Department,StockholmUniversity.
StalagmiteGK02MODERNwas cut in half,with a diamond-coatedwire, across the
centre where it was thickest. The height of the stalagmite wasmeasured to roughly
1.5mm in cross-section. Three layers could be distinguished when looking at the
specimen in microscope (fig. 6a). It is not clear whether these have been deposited
annually.
FoursampleswereextractedfromGK02MODERNbyscrapingwithahandhelddrill
(Dremmel)withadiamond-coateddrillbit(fig.6a&6b).Sample1wasextractedfrom
theuppermosthalfoflayer1,whilesample2wastakenfromthelowesthalfoflayer1.
Sample3representslayer2andsample4representslayer3.
Figure6.a)SamplesinGK02MODERNindicatedbynumberswithapproximatespan(picturebyauthor).b)GK02MODERNaftersampling(picturebyauthor).
16
ThesodastrawstalactitesKS2,KS3andKS4werestudiedunderamicroscopein
order to identify any banding. Since no unambiguous banding or structure could be
distinguished, thestrawsweredivided into5mmintervals,starting fromthetip, from
which samples were extracted. The straws measured 45 to 60mm in length (KS2≈
45mm,KS3≈60-70mm,andKS4≈55-60mm).
StrawKS2andKS3weresimilarinstructure,beingmorefragileinthefirsthalf
from the tip and becomingmore solid towards the root of the straw.KS4 wasmore
fragileandthethicknessof itswallsdidnot increasewithdistance fromthetipalong
thepartremovedfromthecave,despitebeingaboutthesamelengthastheothertwo
straws.
Samples were extracted from the 5mm intervals starting from the tip of the
straws,excludingtherootofKS2andKS3.Thiswasdonebyscrapingthesurfaceusinga
handheld drill (Dremmel) with a diamond-coated drill bit. In the more fragile parts
(closertothetip),fragmentswereinsteadcollectedandlatergroundtoapowderwith
anagatemortar.StrawKS2yielded8samples,KS3yielded10samplesandKS4yielded
11samples.However,sampleKS4:7didnotyieldenoughmaterialforthestableisotope
analysis(yieldedlessthan0.2mg)andwasconsequentlyexcluded.
The material was sent to the stable isotope laboratory in Geo Zentrum
Nordbayern at theUniversity of Erlangen-Nuremberg, Germany,where aGasbench II
connectedtoaThermoFisherDeltaVPlusmassspectrometerwasused.Reproducibility
forδ13Candδ18Owas±0.04and±0.05(1standarddeviation),respectively.
5.Results
5.1StalagmiteGK02MODERN
The stable oxygen isotope values in the four samples extracted from stalagmite
GK02MODERNrangefrom−4.35‰(v-PDB)to−4.82‰(v-PDB),withincreaseddepletion
towardsthetop(fig.7).
17
The stable carbon isotope values in GK02MODERN, ranging from−9.13‰ (v-PDB) to
−9.97‰(v-PDB), shows a similar, but not the exact same pattern as δ18O, due to a
slightenrichmentfromsample4tosample3,andthenmovestowardsdepletion(fig.8).
Figure7.StableoxygenisotopevaluesfromGK02MODERNwithindicationofsamplespansinrelationtodepth.
Figure8.StablecarbonisotopevaluesfromGK02MODERNwithindicationofsamplespansinrelationtodepth.
18
5.2SodastrawstalactitesKS2,KS3andKS4
ThethreesodastrawstalactitesKS2,KS3andKS4yieldedstableoxygenisotopevalues
ranging from−4.03‰ (v-PDB) to−5.30‰ (v-PDB). A couple of sample points are
withinthemeasureduncertaintyofonestandarddeviation(±0.05‰)ofeachother(fig.
9).
Asforthestablecarbonisotopevalues,KS2andKS3areclosetoparallelwitha
fewsamplepointswithinornearthemeasureduncertaintyofonestandarddeviation
(±0.04‰).However,KS4yieldedmoredepletedstablecarbonvaluesthananysample
pointoftheotherstrawsandalsohasasmootherisotopiccurve(fig.10).Valuesrange
from−6.16‰(v-PDB)to−11.13‰(v-PDB).
Figure9.StableoxygenisotopevaluesfromthesodastrawstalactitesKS2,KS3andKS4,withindicationofonestandarddeviation.SampletypedisplayedwiththelettersP(powder)andF(fragment).ThemissingsampleKS4:7isseenasagapinKS4.
Figure10.(Nextpage)StablecarbonisotopevaluesfromthesodastrawstalactitesKS2,KS3andKS4,withindicationofonestandarddeviation(notvisibleonthisscale).SampletypedisplayedwiththelettersP(powder)andF(fragment).ThemissingsampleKS4:7isseenasagapinKS4.
19
6.Discussion
6.1StalagmiteGK02MODERN
StalagmiteGK02MODERN that has been analysed in this study has been growing in the
same place as a stalagmite (GK02) collected in Kapsia Cave in 2009 for paleoclimate
research of the Peloponnese (Finné etal.2014; Finné 2014). Themaximum possible
time of formation forGK02MODERN is 4.5 years (March 2013 to September 2017), but
since the installation on which this stalagmite grew had tipped over causing the
stalagmitetorestartitsgrowth,theactualtimeperiodisshorter,butunknown.
The calculated growth rate in the fossil part (2900 to 1120BP) of stalagmite
GK02was0.15mm/year(Finnéetal.2014),whilethemostrecentlaminae(AD1996to
2008) indicateagrowthrateof0.9mm/year inaverage(calculatedafterFinné2014).
CalculatingthegrowthrateinGK02MODERNbasedonitsthicknessandthemaximumtime
periodof formationresults inagrowthrateof0.33mm/year,which is closer to fossil
rates rather than modern rates. If instead the recent growth rate of 0.9mm/year is
appliedto thestalagmite,consideringthemodernandactivedepositionofcalcite, the
timeperiodofformationiscalculatedto1yearand8months.Althoughtherearesome
uncertaintiesconcerningthegrowthrate,themodernratehasbeenconsideredtobea
morelikelyestimateandis,thus,usedastheagemodelinthisstudy.
20
With an assumed growth rate of 0.9mm/year the start of deposition in
GK02MODERN ismodelled toJanuary2016.Theconstructedagemodelsuggests that the
top sample consists of calcite deposited during the summermonths of 2017 (June -
September). The material in sample 2 has been deposited between February – May
2017, while sample 3 and 4 cover a longer time span; material in sample 3 was
depositedJuly2016–January2017,andsample4wasdepositedJanuary2016–June
2016.
Even though the isotopic values of these samples arewellwithin the range of
previous measurements, both fossil and recent, from Kapsia Cave (mean−4.9‰ (v-
PDB)foroxygenand−9.3‰(v-PDB)forcarbonforthelast30years)(fig.11)(Finné
2014 for further details), the top sample clearly shows more depleted oxygen- and
carbonvaluesthantheothersamplesinGK02MODERN.
Inpreviousresearch(Finné2014)theamounteffecthasproventoberelatively
strong(R2=0.30)onanannualscale(AD1989-2009).Anapproximateannualaverageof
thesamplevaluesfromthisstudy,yieldingδ18O−4.62‰(v-PDB)andδ13C−9.65‰(v-
PDB)for2017,andδ18O−4.36‰(v-PDB)andδ13C−9.15‰(v-PDB)for2016,suggest
a climate trend towards wetter conditions with richer vegetation and increased
biologicalactivity,i.e.towardsdepletionofδ18Oandδ13C.Thecorrelationbetweenδ18O
andprecipitationamountdoes,however,slightlydecrease(R2=0.28)whenaddingthe
valuesfromthisstudytotheearlierregressionanalysis(fig.12).
Even though the monitoring of Kapsia Cave has shown that the environment
remainsrelativelystablethroughouttheyear,an increaseof thecaveair temperature
has been recorded in summer. Since the top sample inGK02MODERN is suggested as a
summerdepositionalsignal itcouldhavebeenaffectedbythecavetemperatureeffect,
drivingtheoxygenvaluestowardsdepletionwithincreasedcaveairtemperature.The
reason for the depleted carbon value is not as clear, but could possibly be related to
higherCO2concentrationsinthecaveinsummer.Inwinter,isotopicvaluesmayinstead
become slightly enriched due to lower CO2 concentrations in the cave atmosphere
(Finné 2014). Hence, if the top sample in GK02MODERN also would include winter
depositionofcalciteliketheothersamples,theisotopicvaluewouldbelessdepleted.
Sincenoextremevariations in theenvironmenthavebeenobserved inKapsia,
these fractionating processes are probably acting on a smaller scale that cannot be
observed when examining isotopic values at multi-annual resolution. Instead, the
21
amounteffectiscontrollingthegeneraltrend.Althoughtheannualaverageδ18Ovalues
calculated for GK02MODERN does not show a strong correlation to the wet season
precipitation with the response time of 1-2 year that has been estimated for Kapsia
Cave(Finné2014),itislikelythattheaverageisotopicvaluefor2017willbecomeless
depleted,sincethefall/winter(OND)depositionsignalisnotincluded.Asthepotential
cavetemperatureeffectisreduced,leadingtomoreenrichedδ18Ovalues,theimprintof
theamounteffect on the isotopic signalwill becomemore pronounced. Addingmore
datapoints to this regressionanalysiswouldbevaluable in the future. In accordance
withthestudyofFinné(2014), thisstudyneither indicates thatexternal temperature
stronglycorrelatestoδ18Oandδ13C,northatastrongcorrelationexistsbetweenδ13C
andrainfall.
Figure11.StableisotopevaluesfromGK02(AD1989-2009)(afterFinné2014)andGK02MODERN(afteragemodel,AD2016-2017)
22
6.2SodastrawstalactitesKS2,KS3andKS4
Thethreesodastrawswereofunknownageandhadnotbeenmonitored in thecave
beforebeingcollectedatthesametime.Eventhoughthetimeperiodcoveredbysoda
straws normally do not exceed a century, approaching this issue by, for example,
correlating the oxygen isotope signal to precipitation from the last hundred years to
find a dating is not reliable in this case. First, the risk of kinetic fractionation may
compromise the δ18O correlation to the amount effect. Second, even under near
equilibriumdepositionandanexpectedrelationshipwiththeamounteffect,thegrowth
ratesareunknownandalsohavebeenshowntovaryconsiderablyinstraws.Hence,the
oxygenisotopecurvemayberespondingtoprecipitationonamonthly,annual,decadal
orcentennialbasis.Withtheseuncertainties,theisotopicsignalcouldpossiblyfitatany
Figure12.CorrelationbetweenprecipitationamountandstableoxygenisotopesinGK02(afterFinné2014)andGK02MODERN.
23
placeinthelastcoupleofhundredyears.Consequently,theoriesondatingofthesoda
strawsKS2,KS3andKS4havebeendeliberatelyavoidedinthisstudy.
It is stillpossible todiscusswhether the threestrawsarecoeval, regardlessof
theexactdate.AlthoughstrawKS4measuredaroundthesamelength(~55-60mm)as
KS2andKS3(~45-65mm),itclearlydifferedinappearance.KS2andKS3hadfragiletips
andincreasingthicknessofthetubewallstowardstheroot.Despitethattheveryrootof
KS4wasnevercollected itexhibiteda fragilestructurealong itswhole lengthwithout
increasingsolidityandthicknessofthetubewalls.Itcould,forexample,bearguedthat
thewholecollectedlengthofKS4depositedfasterthanKS2andKS3andiscoevalwith
the tips of the other two straws. Still, there is not any additional evidence for this
conclusionandeventhoughKS4wasdripping, liketheothertwostraws,when itwas
collected,itmaynothavebeendepositingatthetimeofKS2andKS3ifthewaterwas
notsupersaturatedwithcalcite.
The stable isotopes analysedmay further reveal the relationship between the
three straws. KS2 and KS3 seem to follow a general trend towards more depleted
isotopicvaluestowardsthetips,morepronouncedincarbon,whichisnotseeninKS4
(fig. 9 & 10). Despite that only a few sample points in KS2 and KS3 are within the
measureduncertaintyofonestandarddeviation(±0.05‰foroxygenand±0.04‰for
carbon), their common trend possibly indicates thatKS2andKS3are coeval. This is
furtherstrengthenedbythesimilarappearanceinthetwostrawsaswellastheactive
drippingwhentheywerecollected.
Theδ18Ovaluesinallthreestrawsarewithintherangeofearliermeasurements
onstalagmites(Finné2014forfurtherdetails).Likewise,thisistruefortheδ13Cvalues
inKS2andKS3. Their general trend in δ13C also strengthen the theory presented by
Baskaran & Krishnamurthy (1993), indicating a correlation between increasing CO2
concentrations in the external atmosphere and depletion of carbon values in soda
straws.SuchanalysesareencouragedforfurtherstudiesonmaterialfromKapsiaCave
andthePeloponnese,aswellasforsodastrawstudiesingeneral.
UnlikestrawKS2andKS3,KS4 showsδ13Cvaluesnotonlymoredepleted than
those in the other two straws, but also more depleted values than in any of the
previously presented speleothems from Kapsia Cave, both in modern- and fossil
laminae (Finné 2014 for further details). The reasons for the significantly depleted
valuesinstrawKS4couldbemany.Fractionatingprocessessuchasrapidorvarieddrip
24
ratescouldleadtoδ13Cdepletion.WiththeopeningoftheartificialentranceinKapsia
Caveitisalsoprobablethatairventilationbecamestronger,increasingdegassingofthe
dripwaterasCO2concentrationsgetlower,aswellasalteringthehumidityinthecave
and, thus, increasing evaporation. However, these processes have previously been
associatedwithisotopicenrichmentandcannotexplainthedepletionofcarboninKS4.
Anotherpossibility is thatKS4 formeda fewyearsafter the latestwild fireabove the
cave(AD1997).Atfirst,isotopiccarbonvalueswouldbecomeenrichedduetotheloss
ofvegetation.Afewyearslaterasvegetationisestablishedagain,theremainsfromthe
firemayhaveafertilisingeffectincreasingthebiologicalactivityanddepletingisotopic
carbonvalues.Still,thisstrongdepletionincarbonhasnotbeenobservedinanyofthe
previouslyanalysedspeleothemscoveringthisperiod.Thereasonforthedepletedδ13C
inKS4istoovaguetoargueandwillbeleftunansweredinthisstudy.
In the case of the soda straw stalactites it is important to highlight the way
sampleswereextracted since a standard techniquehasnotbeen clearlypresented in
previousstudiesandthiskindofspeleothemhasnotbeenusedforclimatestudieson
the Peloponnese. As for the fragile parts of the straws it was not possible to obtain
samplesbyscrapingoffpowderfromthesurface,buthadtobecollectedasfragments,
whichwerelatergroundtopowder.Thesesamplesrepresentthewholethicknessofthe
tube wall, unlike powder samples that only represent the outer surface. Since some
calcite also deposits inside the central canal during formation, several yearsmay be
includedinonesample(fig.2).Thiscouldpossiblyresultinagreatersmoothingofthe
isotopicsignal,if,forexample,thereisamixingofwinterandsummerdepositionlikein
GK02MODERN. It is also possible that calcite deposited inside the canal yield different
valuesduetoe.g.alessexposeddepositionalenvironmentthanatthetipofthestraw.
A smoother isotopic curve, both for oxygen and carbon in all three straws, is
presentwheresampleswerecollectedasfragmentsincontrasttopowder(fig.9&10).
This could possibly explain some existing differences between KS2 and KS3, if they
happen to be coeval, as well as the remarkably smooth carbon curve for KS4.
Nevertheless, this phenomenon should be further examined in future studies to
increase the possibility of interpreting the isotopic signal in soda straw stalactites.
Dating of soda straws from Kapsia Cave and the Peloponnese is also encouraged in
combination with stable isotope analyses and analyses of trace elements, to further
explorethepossibilitiesofusingthesespeleothemsasahigh-resolutionclimatearchive.
25
7.Conclusions
Thisstudycontributes toan increasedandstrengthenedunderstandingofhowstable
isotopes in Peloponnesian speleothems correlate to climate variability and their
depositionalcaveenvironment.Thestudyfurtherelucidateshowsodastrawstalactites
canbeusedinclimateresearch,locallyaswellasingeneral.Thefollowingconclusions
havebeenestablishedonthebasisoftheresearchquestionsofthisstudy:
- Theassumedannualaveragesaswellasthemeasuredindividualsamplevalues
inGK02MODERNarewellwithintherangeofpreviouslymeasuredisotopicvalues
inKapsiaCave.
- The newdata points added fromGK02MODERNsupport the relatively strong link
between isotopicdepletionandwetseasonprecipitation(linkedto theamount
effect) thathasbeenpreviouslyestablished forKapsiaCave. It is likely that an
averageoxygenisotopevalueassumedfor2017willbecomeenriched,asparts
ofthewetseason(OND)havenotbeenincluded.Thisenrichmentwouldleadto
a stronger correlationbetween rainfall andδ18O in speleothems,possibly than
whatpreviouslyhasbeenshown.
- The top sample from the stalagmite should be regarded as a summer
depositionalsignal, likelydepositedduringthesummerof2017.It issuggested
thathighertemperaturesduringsummercausethissampletobemoredepleted.
This is not observable in the same way in the other samples, which are less
depleteddue to themixof summerandwinterdeposition.Thus, onanannual
scalecalciteδ18Oisstronglylinkedtotheamounteffect.
- The results from the stable isotopeanalysisof the soda strawstalactites show
potential in using this speleothem as a climate archive, as they yielded values
thatarewithin the rangeofpreviousmeasurements,with theexceptionof the
δ13CinstrawKS4.Theδ13CtrendinKS2andKS3isalsoinaccordancewithwhat
hasbeenconcludedinearlierstudiesonsodastraws,suggestingthatthecarbon
valuescorrespondtoexternalatmosphericCO2.
- Thesamplingtechniqueinsodastrawstalactitesmayaffecttheisotopicvalues,
wheresampling fragments fromstraws incontrast topowder fromthesurface
yields a smoothed isotopic signal. If this relationship is further explored, soda
straws may provide a complementary high-resolution climate archive on a
shortertimescaleonthePeloponneseandingeneral.
26
Acknowledgement
Firstofall,specialthankstomysupervisorMartinFinnéforlettingmetakepartinhisresearchandfor
interesting discussions, an inspiring field trip and supportive and dedicated supervision. I also thank
SteffenHolzkämper,HeadDirectorof Studies and lecturer at theDepartmentofPhysicalGeographyat
Stockholm University, for providing me with the opportunity to work on this project with Martin as
supervisor.FurtherthankstomyamazingfriendsResaandKristerDavénforproof-readingmyEnglish.
Many thanks tomyother friendsand family forencouragementandsupport, and last,butnot least, to
Alexwhoalwaysmanagestomakemehappyfromanypartoftheworld.
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8.1Electronicreferences
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http://www.arkeologi.uu.se/Research/Projects/domesticated-landscapes-en/ (6thofDecember2017)
TripoliMeteosearch,meteorologicaldataforTripoli,Greece:
http://meteosearch.meteo.gr/stationInfo.asp
(6thofNovember2017)
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