Late Glacial to mid-Holocene palaeoclimate development of Southern Greece inferred from the sediment...

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Quaternary International xxx (2013) 1e19

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Late Glacial to mid-Holocene palaeoclimate development of Southern Greeceinferred from the sediment sequence of Lake Stymphalia (NE-Peloponnese)

Christian Heymann a,b,*, Oliver Nelle a,b, Walter Dörfler a,c, Helen Zagana d, Norbert Nowaczyk f,Jibin Xue b,e, Ingmar Unkel a,b

aGraduate School “Human Development in Landscapes”, Christian-Albrechts-University, Leibnizstr. 3, D-24118 Kiel, Germanyb Institute for Ecosystem Research, Christian-Albrechts-University, Olshausenstraße 75, D-24118 Kiel, Germanyc Institute for Pre- and Protohistory, Christian-Albrechts-University Kiel, Johanna-Mestorf-Straße 2-6, D-24118 Kiel, GermanydDepartment of Geology, University of Patras, Rio 26500 Patras, Greecee School of Geography, South China Normal University, 510631 Guangzhou, ChinafHelmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Telegrafenberg/Haus C321, D-14473 Potsdam, Germany

a r t i c l e i n f o

Article history:Available online xxx

* Corresponding author. Institute for Ecosystem RUniversity, Olshausenstraße 75, D-24118 Kiel, German

E-mail address: [email protected] (C. H

1040-6182/$ e see front matter � 2013 Elsevier Ltd ahttp://dx.doi.org/10.1016/j.quaint.2013.02.014

Please cite this article in press as: Heymann,the sediment sequence of Lake Stymphalia

a b s t r a c t

The sedimentary sequence of Lake Stymphalia (NE-Peloponnese) for the first time sheds light on thepalaeoclimate development of Southern Greece from 15 to 5 ka BP. New geochemical data based on high-resolution X-ray fluorescence scanning provide in-situ, and continuous analysis of predefined elementsuites on split-core surfaces. Variations of elements over time were assessed constructing correlationmatrices based on the calculation of Pearson correlation coefficients. The element suite includes Al, Si, K,Ca, Ti, Mn, Fe, Zn, Rb, Sr, and Zr. A major result includes that changes in element behaviour are related tohydrological changes in the catchment (precipitation), lake level status, and evaporation (insolation/solaractivity), and are ultimately driven by climate.

Major trends/shifts in elemental ratios correspond to the climate development in the Eastern Medi-terranean region. Based on correlation of Rb/Sr, reflecting wet/dry climates, with foraminiferal proxies ofmarine core LC21 from the Southern Aegean Sea, and the stable oxygen-isotope record of Soreq Cave(Israel), the BøllingeAllerød, the Younger Dryas, and the 8.2 ka cold event were identified.

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1. Introduction

Terrestrial climate development during the Late Pleistocene andHolocene on the northern and south-eastern margin of the EasternMediterranean has been well investigated over the past decade.Linkages to marine records have been established to identifyNorthern Hemisphere oceaneatmospheric processes that influencethe Eastern Mediterranean climate (e.g., Rohling et al., 2002; Bar-Matthews et al., 2003; Marino et al., 2009; Bar-Matthews andAyalon, 2011). Palaeoclimate reconstructions from lakes in North-ern Greece are based on pollen assemblages, e.g. Lake Ioannina(e.g., Lawson et al., 2004) and aim for long-term climate re-constructions such as at Tenaghi Philippon (e.g., Tzedakis et al.,2006). In case of Tenaghi Philippon, the chronology for the Holo-cene is less reliable (Kotthoff et al., 2008a,b), but Peyron et al. (2011)identified the regional response to the short-lived 8.2 ka event of

esearch, Christian-Albrechts-y.eymann).

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C., et al., Late Glacial tomid-H(NE-Peloponnese), Quaternar

meltwater outbursts of North American proglacial lakes into theNorth Atlantic in the pollen record by correlating key events withmarine core SL152 from the Aegean Sea (Kotthoff et al., 2008a,b).Major problems with the reconstruction of climate history frompollen assemblages exist, such as random preservation of pollenand non-trivial linkage of pollen records to the processes thattrigger changes in vegetation.

With respect to the Mediterranean climate, the Peloponnese(Southern Greece) is located in the transition zone between thetemperate mid-latitudes at the edge of the Northern low-pressuresystem and the tropical low-latitude region with its descendingbranch of the Hadley cell (e.g., Köppen, 1936; Lionello et al., 2006).Hence, a lake in such a climatically sensitive region is an excellentarchive of climate change. However, the development of the con-tinental climate on the Peloponnese is not well understood so far.Recent reviews of Eastern Mediterranean palaeoclimate focussingon the past 25 and 6 ka, identified spatio-temporal gaps in palae-oclimate data from regions such as Southern Greece (Robinsonet al., 2006; Finné et al., 2011). Continuous lacustrine archivesare sparse on the Peloponnese. Modern Lake Stymphalia (NE-Peloponnese) is the only natural, perennial lake in this region.

olocene palaeoclimate development of Southern Greece inferred fromy International (2013), http://dx.doi.org/10.1016/j.quaint.2013.02.014

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C. Heymann et al. / Quaternary International xxx (2013) 1e192

Studies conducted on the Peloponnese aimed for a reconstruc-tion of relative changes in palaeoclimate for the past 7000 yearsfrom lacustrine and lagoonal archives based on pollen assemblagezones (Atherden et al., 1993; Jahns, 1993; Kontopoulos andAvramidis, 2003). In the Phlious basin directly east of Stymphalia,studies on colluvial and lacustrine archives focused on separate timeslices, like the reconstruction of Holocene soil erosion (Fuchs et al.,2004; Fuchs, 2007), or the reconstruction of Upper Pleistocenevegetation history (Urban and Fuchs, 2005). Fuchs (2007) evaluatessoil erosion based on colluvial archives as a result either of naturalagents such as climate, tectonics or both, or as a result of anthro-pogenic activities in the NE-Peloponnese. Comparing the sedimen-tation rates from Phlious basin calculated on the basis of OSL ages topalaeo-rainfall data from Israel, Fuchs (2007) established a linkbetween increased sedimentation rates and enhanced settlementactivity since Neolithic times but admits that continuous climaterecords for the Holocene are not available for Southern Greece.Colluvial archives are known to be discontinuous, making theirpalaeoenvironmental interpretation non-trivial.

This paper presents the first continuous XRF record of a sedi-mentary sequence from Lake Stymphalia which captures thepalaeoclimate development of the Peloponnese for the time from15 to 5 ka BP. The aim of this paper is to examine the elementalvariations as a response to climate change in the Eastern Mediter-ranean region with focus on the hydrological regime of the catch-ment and in-lake processes. Special attention is given to (1) theinvestigation of element relationships and their change over time,(2) reconstruction of trends/shifts in sediment input, grain size,lake level, in-lake carbonate precipitation, redox conditions, lakeproductivity, and catchment climate based on elemental proxies,(3) relation of these trends/shifts to results from sedimentologicalanalysis and other geochemical proxies, and (4) discussion of cli-matic implications that can be drawn from the analysis of theelemental suite.

2. Study area

Lake Stymphalia (37�5005800N, 22�2703800E) is located in thenorth-eastern Peloponnese, Greece, 25 km south of the Gulf ofCorinth, at 600m a.s.l (Fig.1b). It is situatedwithin a karst polje thatencloses the southern slope of Mt. Kyllini (or Mt. Ziria) which risesto a height of 2374 m a.s.l. The southern margin of the Stymphaliapolje is themountain ridge of Oligirtos (1925m a.s.l.). The lake has asurface area of 3.5 km2 which can extend to 5 km2 during highwater levels in spring. Its average water depth is 1.5 m with amaximum water depth of 2.3 m. Lake Stymphalia is the largestmountain lake in the Peloponnese and its catchment area is in therange of 218 km2 (Morfis and Zojer, 1986). Several karst springs, thelargest of them named Stymphalia and Kefalari, and some minortorrential river systems feed the lake (Morfis and Zojer, 1986). Adoline (katavothre), located near the SW border of modern LakeStymphalia, acts as natural underground water discharge, butnowadays it is not active due to artificial water regulation. Tracerexperiments revealed a subterraneous hydrogeological connectionto the karst springs of Kiveri and Lerni 30 km to the SE of LakeStymphalia at the Gulf of Argos (Morfis and Zojer, 1986). Since thelate 19th century, a former Roman build tunnel from the 2nd cen-tury AD (“Hadrianic aqueduct”) at the SE rim of the lake channelspart of the lake waters for agricultural purposes to the neighbouringpolje of Scotini and from there to the coastal plain of Kiato (Morfisand Zojer, 1986; Lolos, 1997). The modern Lake Stymphalia is re-ported as an eutrophic (Papastergiadou et al., 2007), hard-waterlake (pH 8.5; alkalinity 123 mg CaCO3 l�1; 44.2 mg Ca l�1) with aconductivity of 208 mS cm�1 (measurements during the fieldcampaign in March 2010, cf. Morfis and Zojer, 1986).

Please cite this article in press as: Heymann, C., et al., Late Glacial tomid-Hthe sediment sequence of Lake Stymphalia (NE-Peloponnese), Quaternar

In principle, the region has a Mediterranean climate (cf. Köppen,1936; Lauer and Bendix, 2006) with mild wet winters and warm tohot, dry summers. However, the general climate patterns aremodulated on the local scale by extreme differences of relief onshort distances. Due to its latitudinal position between 36� and 38�

N (Fig. 1a), the Peloponnese is located in a transitional zone, wherethe influence of mid-latitude climate variability patterns such asthe North Atlantic Oscillation (NAO) and tropical influence of thedescending branch of the Hadley cell are both important (Lionelloet al., 2006). Furthermore, the Peloponnese is exposed to the Si-berian high-pressure system in winter and to the South AsianMonsoon in summer (Lionello et al., 2006).

Precipitation in the karst valley of Stymphalia amounts to900 mm y�1, a value that rises to 1200 mm y�1 in the uppercatchment area above 1500 m a.s.l. in the Kyllini (Ziria) mountains(Morfis and Zojer, 1986). Summer temperatures vary between 15�

and 30 �C, while winter temperatures range from 2� to 10 �C withfrequent drops below 0 �C (Morfis and Zojer, 1986).

Papastergiadou et al. (2007) distinguished eight different landcover/use types. Forests in the Stymphalia valley are dominated bythe endemic species Abies cephalonica, as well as on wet forestedland Salix alba and Populus alba. Garrigues typical of the EasternMediterranean consist mainly of Quercus coccifera, Pistacia lentiscusand Cistus spp. Different crops, e.g. tomatoes are grown on agri-cultural land in the vicinity of the lake. Periodically flooded areasare characterized by communities of Molinio-Holoschoenion,Magnocaricetea, and different associations of Phragmitelia. Themacrophyte community of the lake is dominated by Phragmitesaustralis which grows in reed beds within and around the lake.Open water species are of the class Potametea and Lemnetea. Dueto intensified agricultural land use in the area around Lake Stym-phalia, siltation and eutrophication increased over the past 60 yearswhich led to a lake surface reduction by reed bed extension(Papastergiadou et al., 2007).

Catchment geology is dominated by carbonate rocks (Fig. 1a).According toMorfis and Zojer (1986) and IGME geological maps, sixgeological units can be distinguished. (1) A phyllite-quartzite unit(PQ-unit) consisting of quartzites and mica schists which is over-thrust by the anchimetamorphic phyllites and schists of the Tyroslayer, as well as limestones and flysch of the (2) Tripolis nappe. (3) Atectonoesedimentary complex marks the contact zone to the suc-ceeding (4) Olonos-Pindos nappe. The nappe consists of limestones,marls, radiolarites, hornstone, flysch, and basic eruptives. On top ofthis nappe follow (5) Neogene deposits which are mainly brackishto lacustrine marls, and fluviatile to lacustrine conglomerates. Theyoungest geological unit is characterised by (6) Quaternary lacus-trine clays interfingering with coarse fan deposits at the mountainslopes.

3. Materials and methods

Field work was carried out at Lake Stymphalia in March 2010and MarcheApril 2011. An additional detailed reconnaissance wasconducted in September 2010. The 16 m long core STY-1A with a5.6 m long parallel core STY-1B was retrieved in 1 m sections of80 mm and 55 mm diameter with a Usinger piston corer (Mingramet al., 2007) on a floating platform. Overlap between individualone-meter-sections of cores STY-1A/B was at least 40 cm. Thesediment cores were stored in PVC tubes, wrapped in plastic, andtransported by truck to Kiel, where they were kept at þ4 �C in areefer container until cutting, logging, and sub-sampling.

The following core parameters were described in the lab:lithology, sediment texture (grain size), sediment colour accordingto Munsell (2000), sediment structures (boundary types) andcomponents.


Fig. 1. a. Map of the Eastern Mediterranean showing the study area and locations of palaeorecords mentioned in this paper. b. Topographic and geological map of the Stymphaliabasin showing the drainage system and the approximate catchment area.

C. Heymann et al. / Quaternary International xxx (2013) 1e19 3

Please cite this article in press as: Heymann, C., et al., Late Glacial tomid-Holocene palaeoclimate development of Southern Greece inferred fromthe sediment sequence of Lake Stymphalia (NE-Peloponnese), Quaternary International (2013), http://dx.doi.org/10.1016/j.quaint.2013.02.014


Magnetic susceptibility (k) was measured on split-core surfacewith a step size of 1mm at the Paleomagnetic Laboratory of the GFZPotsdam using a Bartington MS2E/1 spot reading sensor in com-bination with an automated logging system (Nowaczyk, 2001;Nowaczyk et al., 2002). k was mainly used for correlation of thecores and only secondarily as a palaeoenvironmental proxy.

Loss on ignition (LOI) was measured to determine organicmatter and carbonate content on core STY-1A with a sampling in-terval of 5 cm in the upper 5.6 m of the core. Samples were dried at105 �C for 12 h, weighed and combusted at 550 �C and 925 �C for6 h. As LOI at 550 �C is dependent on temperature and exposuretime, as well as sample size (Heiri et al., 2001), dry weight of thesamples was kept in the same size range of <1.2 g with only 13% ofsamples exceeding this range by up to 0.5 g. The exposure time of6 h at 550 �C and 925 �C is sufficient to remove all organic matter,and evolve all carbon dioxide from carbonates, respectively (Heiriet al., 2001). Continued weight loss by e.g., clay minerals losingstructural water at 550 �C at an intermediate exposure time of 6 h isnegligible (Heiri et al., 2001). Organic matter and carbonate contentwere calculated according to Dean (1974) and Heiri et al. (2001).

Lasergranulometric analysis was performed on a MalvernMastersizer 2000 (www.malvern.com). Samples were taken foreach sediment unit in the upper 5 m of core STY-1A. Sedimentsamples were pre-treated with hydrogen peroxide to destroyorganic substance, sodium acetateeacetic acid buffer to destroycarbonates, and sodium pyrophosphate for dispersal. Grain sizeswere classified according to DIN EN ISO 14688-1 (01/2007).Obtaining reproducible results from laser diffraction indicated anobscuration around 20% (Sperazza et al., 2004).

Non-destructive X-ray fluorescence (XRF) measurements usingenergy dispersive fluorescence radiation on split core surfaces wereperformed with an Avaatech XRF Core Scanner (Richter et al., 2006)at the Institute of Geosciences, Kiel University. A Rhodium X-raysource was used which theoretically allows the measurement of awide range of elements from Aluminium to Uranium depending onthe selected tube voltage. Preparation of the split core surfaces forXRF analysis was done according to Tjallingii et al. (2007). The res-olution of the scans of the upper 5m of core STY-1A and overlappingintervals of core STY-1B was 1 mmwith an exposure time of 10 s at10 kV and 15 s at 30 kV, respectively. Modelling of the spectrogramwas done usingWinAxil X-ray analysis software (Canberra) assuringfor quality control that the Chi-square value of the 10 and 30 kVmodel was smaller than 3 (Tjallingii, 2007). Eleven elements (10 kV:Al, Si, K, Ca, Ti,Mn, Fe; 30 kV: Zn, Rb, Sr, Zr)were selected for detailedanalysis based on their presence within the sediment and theirpalaeoenvironmental and -climatic importance (cf. ch. 4.3).Furthermore, elements with intensities less than 300 total counts,which are less reliable (Tjallingii, 2007), were excluded. The XRFscanning results represent element intensities in total counts whichmainly depend on element concentration, but also onmatrix effects,physical properties, sample geometry, and hardware settings of thescanner (Röhl and Abrams, 2000; Tjallingii et al., 2007). The XRFscanning results are reported as log-ratios that can be interpreted aschanges in relative concentration of an elemental pair, to avoidstatistical analysis of data sensitive to the closed-sum effect andelemental ratios being asymmetric (Weltje and Tjallingii, 2008). El-ements were normalized to the inert element Al (Löwemark et al.,2011). Assessing the normalized elemental data in a palae-oenvironmental and palaeoclimatic context considers relativechanges of one element against another, rather than with absolutechanges in element concentration. Assessing these relative changesof element A against element B avoids taking into account theamount of material that might be transported away in times whenthewaters of Lake Stymphalia reach the doline, orwhen the doline isblocked (e.g., due to an earthquake) and a tectonically driven lake


level rise increases the accommodation space but also shifts thedepositional centre. Therefore, trends in elemental ratios and sig-nificant peaks whichmight indicate rapid environmental or climaticchange are reported.

Relationships between different elemental ratios are exploredcalculating Pearson’s correlation coefficients and are presented ascorrelation matrices (Trauth, 2010). Furthermore, correlationmatrices of elemental ratios will give an insight into the coupling/decoupling of elements over time. In general, grain size of thedominant mineral host and subsequent particle size sorting con-trols the chemistry of sediments (e.g., Das and Haake, 2003; Koiniget al., 2003; Jin et al., 2006b; Kylander et al., 2011). Therefore, theelemental data were grouped according to lithostratigraphic unitsprior to statistical analysis, before analyzing time slices (LateGlacial: 15e11.7 ka BP, early Holocene: 11.7e8 ka BP, mid-Holocene:8e5 ka BP). The fields of correlation matrix represent Pearson’scorrelation coefficients for each pair of elemental ratio for whichconfidence intervals and a probability value (t-test) were calculated(Trauth, 2010).

Spectral analysis is a very useful tool in palaeoclimate researchin order to understand the physical processes which generate thevariability recorded in a time series. This study assessed cyclicalvariations in the ratio of Rb/Sr time series using REDFIT (Schulz andMudelsee, 2002), which was specifically designed for unevenlyspaced time series data.

3.1. Chronology

Two organic sediment samples (BETA324349/324350) for 14Canalysis were pre-treated (acid washes) and the bulk organic frac-tionmeasured at Beta Analytic Inc. (USA). All other organic sedimentsamples (KIA42912, 44003-06, 45954-58, 47446, 47449) and onecharred plant remain sample (KIA42912) for 14C analysis were pre-treated and measured at the Leibniz-Laboratory for RadiometricDating and Isotope Research at Kiel University (Germany).

The organic sediment samples were checked for any contami-nants under the microscope. The selected material was extractedwith hydrochloric acid (1%) and sodium hydroxide (1%) at 60 �C, andagain hydrochloric acid (1%) (alkali residue fraction). The organicmaterial (humic acid fraction) extracted by the basewas precipitatedwith hydrochloric acid, washed, and dried for further treatment. Thecombustion of all fractions to carbon dioxide was performed at900 �C in a closed quartz tube together with copper oxide and silverwool. The developed carbon dioxide was reduced to graphite withhydrogen at 600 �C over an iron catalyst. The iron-graphite-alloywaspressed into a pellet in the target holder. The targets were measuredwith a 3MV Tandetron 4130 AMS system (High-Voltage EngineeringEuropa). The analytical precision for this system is 0.3e0.4% forsamples younger than 2000 years, resulting in typical 14C age un-certainties (1s) of �40 years (Nadeau et al., 1997, 1998).

The radiocarbon dates on alkali residue and humic acid fractionsof the organic sediment samples are given in Table 1. Radiocarbondates on humic acids and therefore also the dates on the bulkorganic fractionwere excluded from the ageedepth-model becausethey are assumed to be more mobile within the sediment, possiblyintroduced by younger plant roots to depth. Furthermore, the dateon the charred plant remain (KIA 42913) was excluded because athorough identification was not possible, leaving the possibilitythat this remain is plant root material. The alkali residue date(KIA44003) at a depth of 0.32 m is an outlier most probably due tobioturbation or reworking of the sediment by increased windstress. In addition, dates on alkali residuewith a carbon content lessthan 0.07% within the sample fraction are less reliable (KIA45956-58 and 47449) and most probably give too old ages. Alkali residueages younger than 4.2 ka cal BP that are included in the ageedepth


http://www.malvern.com


model were corrected for a hard-water error under the assumptionthat the Late Holocene climate processes of the Northern Hemi-sphere, including the Eastern Mediterranean region, are the sameas today (Walker et al., 2012). The hard-water error was determinedby dating an alga which was sampled in-situ at the bottom of LakeStymphalia during field work (MarcheApril 2011). Its conventionalage is reported as 280 � 20 14C years and 96.55 per cent moderncarbon (pmC; analysis no. KIA44002). Taking into account that thepresent day atmosphere (as of 2011) has a pmC value of 104, perdefinition the atmosphere of 1950 AD had a value of 100 pmC, theamount of 315 14C years has to be added. Therefore, analysisassumed a hard-water error of 600� 10 14C years. Calibration of theradiocarbon ages was done with the INTCAL09 calibration curve(Reimer et al., 2009) within the Oxcal 4.1 program (Bronk Ramsey,2001, 2008, 2009a).

Table 1List of radiocarbon samples taken from Lake Stymphalia core STY-1A. All samples are calibrated with OxCal 4.1. All ages are unmodelled ages in 1s range. (The sample numbersrefer to the sampling depth before adjusting the field-based correlations between individual core sections in the laboratory.)

Sample no. Analysisno.

Sample material Samplefraction

C weight(mg)

Sample Ccontent inthis fraction[%]

CorrectedpMC

d13C (&) 14C age �1s(BP)

IntCal09a Depth(cm)

STY-1/32 KIA44003 Organic sediment Alkali residue 1.58 0.42 67.36 � 0.25 �22.74 � 0.16 3174 � 29 3442e3370 32STY-1/52 KIA45954 Organic sediment Alkali residue 1.57 0.27 76.20 � 0.26 �21.40 � 0.16 2184 � 28 2304e2146/

1521e1417b52c

STY-1/72 KIA47446 Organic sediment Alkali residue 3.12 0.44 76.32 � 0.19 �25.25 � 0.10 2171 � 20 2299e2133/1514e1414b

72c

STY-1/72 KIA47446 Organic sediment Alkali residue 3.12 0.44 75.80 � 0.19 �24.50 � 0.19 2225 � 20 2313e2160/1553e1424b

72c

STY-1/72 KIA47446 Organic sediment Humic acids 1.52 0.07 85.22 � 0.37 �25.28 � 0.23 1285 � 35 1276e1180 72STY-1/92.5 KIA44004 Organic sediment Alkali residue 2.55 0.31 69.38 � 0.21 �23.77 � 0.17 2935 � 25 3161e3009/

2354e2338b107c

STY-1/149.5 KIA42912 Organic sediment Alkali residue 1.62 0.35 66.45 � 0.24 �24.94 � 0.21 3285 � 30 3557e3471/2841e2755b

164c

STY-1/149.5 KIA42912 Organic sediment Humic acids 2.21 0.69 84.47 � 0.24 �27.22 � 0.19 1355 � 23 1299e1279 164STY-1/216.5 KIA44005 Organic sediment Alkali residue 6.03 0.83 60.62 � 0.23 �24.77 � 0.25 4020 � 30 4522e4438 236c

STY-1/216.5 KIA44005 Organic sediment Humic acids 2.09 0.41 64.18 � 0.23 �24.03 � 0.22 3563 � 29 3903e3830 236STY-1/246.5 KIA44006 Organic sediment Alkali residue 2.89 0.29 45.35 � 0.22 �27.00 � 0.13 6350 � 40 7411e7182 266c

STY-1/246.5 KIA44006 Organic sediment Humic acids 1.95 0.28 54.76 � 0.23 �26.22 � 0.15 4837 � 34 5608e5485 266STY-1/280 KIA45955 Organic sediment Alkali residue 1.77 0.19 40.92 � 0.20 �25.89 � 0.19 7178 þ 39/�38 8015e7960 280c

STY-1/300 KIA42913 Charred plantmaterial/root?

Alkali residue 1.76 4.92 38.30 � 0.16 �27.64 � 0.10 7710 � 35 8540e8450 324

STY-1/345 KIA45956 Organic sediment Alkali residue 0.42 0.04 21.77 � 0.40 �26.91 � 0.59 12,249 þ 148/�146 14,525e13,915 345c

STY-1/345 BETA-324349

Organic sediment Bulk organic e e e �25.50 10,270 � 50 12,126e11,839 345

STY-1/354 KIA47449 Organic sediment Alkali residue 0.58 0.07 17.05 � 0.28 �27.26 � 0.13 14,209 þ 133/�131 17,511e17,081 354STY-1/375 KIA45957 Organic sediment Alkali residue 0.42 0.02 16.21 � 0.39 �24.85 � 0.77 14,615 þ 194/�190 18,394e17,478 375STY-1/375 BETA-

324350Organic sediment Bulk organic e e e �24.40 11,120 � 50 13,104e12,936 375

STY-1/423 KIA45958 Organic sediment Alkali residue 0.64 0.09 14.27 � 0.28 �25.71 � 0.20 15,639 þ 156/�153 18,925e18,635 423c

a Based on Reimer et al. (2009).b With a reservoir correction of 600 yrs.c Radiocarbon dates considered as ageedepth points within the ageedepth model.

An ageedepth model was calculated with the Oxcal 4.1 software(Bronk Ramsey, 2001, 2008, 2009a). The P-Sequencemodel togetherwith general outlier model (Bronk Ramsey, 2009b) of Oxcal 4.1 wasapplied to the data, assuming deposition to be random. A k-value of100, equivalent to 10 mm calculation increments, was chosen. Toplot the proxy data of the core discussed hereafter, the ageedepthpolygon modelled in 10-mm-increments was exported from Oxcaland interpolated to 1 mm increments utilizing MATLAB (Trauth,2010). Calibrated years are denoted as cal BP (before AD 1950).

4. Results and environmental inference

4.1. Sedimentology: facies types and lake level variations

Logged parameters distinguished six sediment units (No. 51e57of the entire STY-1 sequence) within the core section discussed


here, of which two are subdivided. A detailed description of thelithostratigraphy is given in Fig. 2. All sediment units are dominatedby clay and silt which vary in content. An exception is unit 55bwithaminor intercalation of fine sand (3.54%) in addition to clay and silt.Clay content gradually increases from unit 52 (13.4%) towards unit56 (39.5%), while the silt fraction decreases within the same interval(from 86.4% to 60.4%). Unit 57a shows an increase of the silt fraction(80.2%) followed by a drop to 73.4% within unit 57b. Clay contentvaries accordingly and shifts from19 to 25.8%. Gastropod shells/shellfragments are a dominant component within the sequence,although abundance varies. Gastropods are absent within unit 52.Gravel- to coarse sand-sized carbonate detritus (lithic fragments) area major component in the basal units 52, 53 and occur as accessorycomponent again within unit 57b. Sediment structures are onlyvisible within unit 56, where interbedded layers of black and gray

clay are disturbed and show mottling due to bioturbation. Munsell(2000) colour changes over the discussed core section from paleolive (unit 52: 392e355 cm; 16.8e14.6 ka cal BP) to greyish brown(topmost unit 57a/b: 268e215 cm; 7.3e4.2 ka cal BP) with variousshades of grey to black in between. Unit boundaries are all grada-tional. There are no sedimentological indicators of a hiatus, a timeperiod of non-deposition, such as sharp or erosive unit boundaries.

Two facies types were distinguished. Sediment characteristics ofunits 52e55a/b (15.7e8.5 ka cal BP) and 57a/b (7.3e4.2 ka cal BP)indicate deposition in a (1) shallow littoral environment underopen water and/or oxygenated lake conditions (cf. Cohen, 2003)with typical mineral clay and carbonate lithology, clay silt grain sizewith a low fine sand fraction, thick beds, olive, grey and browncolours, carbonate detritus and gastropods as components.Changing wave influence and therefore changes in wind stress areindicated by intact gastropod shells, in-situ deposition below wave


2 4 6 8 10%Organic Matter

10 20 30 40%Carbonate

components

P_Sequence STY-1 [Amodel:10]

Boundary Unit 50/51

R_Date KIA 45958 [A:107]

R_Date KIA 45957? [P:91]

R_Date BETA 324350? [P:0]

R_Date KIA 47449? [P:0]

R_Date KIA 45956 [A:102] R_Date BETA 324349? [P:100]

R_Date KIA 42913? [P:100]

R_Date KIA 45955 [A:95]

R_Date KIA 44006 [P:0]R_Date KIA 44006 [A:101]

R_Date KIA 44005? [P:0]

R_Date KIA 44005 [A:9]

R_Date KIA 42912? [P:0]

R_Date KIA 42912 [A:48]

R_Date KIA 44004 [A:13]

R_Date KIA 47446? [P:0]

R_Combine KIA 47446 [A:79]

R_Date KIA 45954 [A:18]

R_Date KIA 44003? [P:0]

Boundary Coretop [A:100]

05101520Modelled Age (cal ka BP)

0

100

200

300

400

Dep

th [c

m]

OxCal v4.1.7 Bronk Ramsey (2010); r:5 Atmospheric data from Reimer et al (2009);

215

225

235

245

255

265

275

285

295

305

315

325

335

345

355

365

375

385

395

405

415

423

Dep

th [c

m]

cla

ys

ilt

57b

57a

56

55b

54

53

52

51

un

it/f

ac

ies

lith

olo

gy

/

tex

ture

Unit 57b (249.5-240.3//215 cm): grayish brown silty

clay with common gastropod shells/shell fragments,

and carbonatic, gravel-sized lithic fragment.

Silt and shell fragments decrease to the top.

Upper boundary gradational (UB=g).

Munsell (2000) colour code (MCC)=10YR 5/2.

Unit 57a (268-249.5 cm): grayish brown silty clay

with common gastropod shells/shell fragments. Shell

fragments decrease to the top. UB=g. MCC=10YR 5/2.

Unit 56 (286-268 cm): Gray to black, mottled clay

with rare gastropod shell fragments. UB=g.

MCC=5Y 5/1 to 5Y 2.5/1.

Unit 55b (302.5-286 cm): Gray clayey silt with fine sand.

Gastropod shells are common. UB=g. MCC=5Y 5/1.

Unit 55a (307-302.5 cm): Gray clayey silt with common

gastropod shells. Clay decreases to the top. UB=g.

MCC=5Y 5/1.

Unit 54 (335.5-307 cm): Very dark gray clay with

some silt. Gastropod shells/shell fragments are

common. Silt increases to the top, while shells/shell

fragments decrease. UB=g. MCC=5Y 3/1.

Unit 53 (355-335.5 cm): Dark gray clay with some

silt. Abundant carbonatic, gravel- and coarse sand-

sized lithic fragments. Gastropod shell fragments are

rare (only upper part of unit). UB=g. MCC=5Y 4/1.

Unit 52 (392//362-355 cm): Pale olive clayey silt

with some fine sand. Carbonatic, gravel- and coarse

sand-sized lithic fragments are common.

UB=g. MCC=5Y 6/3.

Unit 51 (423-392 cm): Yellowish brown clay with

gravel-and coarse sand sized lithic fragments.

UB=g. MCC=10YR 5/6.

lithic fragmentgastropod shell/shell fragmentorganic debris

clayclay siltmottled

shallow littoraldeep littoral

Leg

en

d

2]2]2]2]2]2]2]2]2]2]2]]]

Fig. 2. STY-1 composite core log for the depth interval 215e423 cm, organic matter and carbonate content from LOI, and unit description. The Oxcal (version 4.1) ageedepth model depicts the upper 423 cm of core STY-1, while thestudied depthetime interval is shown in the shaded gray area. Radiocarbon dates are from alkali residue (black), humic acid and bulk organic (green) fraction. KIA440037 is an alkali residue outlier due to bioturbation (red), whileKIA429137 is most probably a root remain (blue). The blue lines in the diagram to the right show the ranges for 1s (68.2%, outer) and 2s (95.4%, inner). Sedimentation rates are also given. (For interpretation of the references to colour inthis figure legend, the reader is referred to the web version of this article.)

C.Heym

annet

al./Quaternary

Internationalxxx

(2013)1e19

6Pleasecite

thisarticle

inpress

as:Heym

ann,C.,etal.,LateGlacialto

mid-H

olocenepalaeoclim

atedevelopm

entofSouthernGreece

inferredfrom

thesedim

entsequence

ofLake

Stymphalia

(NE-Peloponnese),Q

uaternaryInternational(2013),http://dx.doi.org/10.1016/j.quaint.2013.02.014


base, and gastropod shell fragments which indicate reworking ofsediments above wave base and/or lateral transport. The charac-teristics of unit 56 (8.5e7.3 ka cal BP) with black, organic rich layers(cf. Section 4.2), and rare gastropod shell fragments which indicatetransport, point to a deposition on a meromictic lake floor within a(2) deep littoral environment (cf. Cohen, 2003). Grey clay layersreflect occasional re-oxygenation of the lake bottom. Mottling iscaused by bioturbation when oxygen levels in bottom waters arehigher again.

Sedimentation rates of the discussed core section calculatedbetween depths with an assigned radiocarbon date are in the rangeof 0.11e0.18 mm y�1 (Fig. 2). At 14 ka cal BP the sedimentation ratedecreases from previously 0.16 to 0.11 mm y�1 (within unit 52).Then the sedimentation rate increases at 8 ka cal BP to 0.18 mmy�1

(within unit 56). After 7.2 ka cal BP the sedimentation rate de-creases again to 0.12 mm y�1 (within unit 57a).

Lowor starved sedimentation (condensed sections) often occursduring lake level rise, when the depositional centre of the lakemigrates in a more marginal direction (cf. Nichols, 2009). In addi-tion, in case of Lake Stymphalia it can also be assumed that duringlake level highstand, the doline in the SW corner of the polje isreached and some of the sediment in suspension is transportedaway rather than deposited. An increase in depositional energywithin units 52 and 53 is reflected in carbonate detritus (lithicfragments) content. This increase in depositional energy is mostlikely due to activation of torrential river systems during highprecipitation events and therefore intense physical weatheringwithin the catchment area. Calmer conditions prevail from unit 54upward through unit 56.

4.2. Loss on ignition and magnetic susceptibility

Organic carbon is below 10% throughout the sediment sequence(Fig. 2). In units 52 to 54, organic carbon content is low to modest(<5.6%). Values start to decline around 11.6 ka cal BP and reach aminimum in organic carbon content (3.8%) within unit 55a at10.2 ka cal BP. Then, organic carbon content increases in unit 55b,reaching maximum values of up to 9.8% (sapropelic) at 7.7 ka cal BPin unit 56 and decline again within unit 57a/b. Carbonate content isbelow 45% throughout the sediment sequence (Fig. 2). In units 52and 53, carbonate content is not higher than 35.2%, dropping tovalues as low as 11.6%. Within unit 54 the carbonate fraction rises tovalues above 40% with highest carbonate content reached withinunit 55a (43.9%) at 10.2 ka cal BP. Carbonate content sharply declinesfrom unit 55b towards 56, followed by a modest rise in unit 57.

Magnetic susceptibility is lowwithin units 52, 53 and 54, excepta peak around 13.4 ka cal BP (unit 53). k remains low throughoutunits 55a/b to 57, except distinct peaks around 10 ka cal BP (unit55b), 7.9 ka cal BP, and 7.6 ka cal BP (both unit 56).

Low magnetic susceptibility values can indicate decreasederosion in the catchment and therefore a decreased input ofterrigenous material into the lake (Nowaczyk et al., 2002). Peakareas in magnetic susceptibility reflect times of enhanced input ofmagnetic minerals such as magnetite (Fe3O4) from the catchmentand hence, times of increased catchment erosion. However, duringepisodes of lake and/or pore water anoxia together with enhanceddeposition of organic matter, selective dissolution of magnetite canoccur (Nowaczyk et al., 2002). The susceptibility record of STY-1 isshown in Fig. 4a and is further discussed in the context of Section 5.

4.3. XRF

Normalized elements of the Lake Stymphalia sedimentarysequence can be divided into a siliciclastic group composed of clayand clastic minerals which are derived from the lake catchment and


are a proxy for winter precipitation in the catchment area, hencefluvial input (or surface run-off) to the lake, and a carbonate groupwhich are predominantly carbonate minerals precipitated withinthe lake during summer when evaporation is highest.

Rubidium (Rb), titanium (Ti) and potassium (K) are often asso-ciated with clay mineral assemblages (e.g., Koinig et al., 2003).However, Rb can also be a substitute for K in K-feldspars (Kylanderet al., 2011). As the most abundant zinc-containing mineral,sphalerite (ZnS), is unstable under oxidizing conditions in sedi-ments (Luther et al., 1996), Zn is predominantly associated withphyllosilicates as secondary mineral in soils (Manceau et al., 2004).Zirconium (Zr) is associated with heavyminerals such as zircon andnormally enriched in medium to coarse silts (Kylander et al., 2011).Silicon (Si) is abundant in aluminosilicate minerals, alkali feldspars(Kylander et al., 2011), but also an important component withindiatom frustules and therefore connected to in-lake diatom pro-ductivity (Peinerud, 2000; Peinerud et al., 2001). Si is generallylinked to coarser silt and sand size fractions.

The Zr/Rb-ratio can be regarded as proxy for grain size changeswith ahigh ratio representing coarser grain sizes, and lowratios beingindicative for finer grain sizes (Dypvik and Harris, 2001; Kylanderet al., 2011). This relationship is not valid, when there is a signifi-cant contribution of Rb from K-feldspars within the coarser silt andsand size fraction. Sand content is below 4%over thewhole profile. Zris linked to the silt-sized fraction. But most strikingly, Rb is stronglylinked to the clay mineral assemblage suggesting no K-feldsparsource. Main drivers of the variations in Zr/Rb are therefore differ-ences insilt vs. claycontent. Theminor representationof coarser grainsizes (larger than silt) also indicates that chemical weathering isdominant in the catchment rather than physical weathering.

Calcium (Ca) is mainly associatedwith themineral CaCO3 withinlake sediments (Cohen, 2003). It has either an allogenic source fromcarbonate weathering in the catchment, or authigenic sources, thatare in-lake biogenic and/or chemical precipitation. Strontium (Sr) isa substitute for Ca in carbonate minerals (e.g., aragonite) and co-precipitates within lakes (Cohen, 2003; Kylander et al., 2011). Pre-cipitation of SrCO3 is caused by evaporative concentration until lakewaters are saturated with respect to carbonate, a process which isoften accompanied by a lowering of lake level. Another Sr-sourceare plagioclase feldspars associated with catchment input of sili-cates to the lake (Kylander et al., 2011).

Lake redox conditions are assessed from manganese (Mn) andiron (Fe). Abundance of Mn and Fe as allogenic clastics, authigenicoxides, carbonates, and organic complexes is determined by in-lakeand catchment conditions (Engstrom andWright, 1984). Mn and Feplay a dominant role in redox processes within a lake (Davison,1993). Amorphous Fe can form authigenic minerals under oxiclake water conditions while Fe that is bound to clay minerals isdeposited without any reaction. Under reducing conditions, Fe isreleased from the sediment into the water column. Manganesewithin the mineral lattice of an allogenic mineral is retained withinthe sediment under oxic conditions, as well as manganese oxideswhich are highly insoluble in an oxic environment. Under anoxiclake water conditions, Mn is slower reduced than Fe but also notretained in the sediment. The ratio of Mn/Fe is therefore a proxy ofredox conditions within a lake (Wersin et al., 1991). Changes inoxygen level within a lake can be caused by changes in the venti-lation of the water column due to lake level variation and/or vari-ation in wind stress, or by increased biological activity ofphotosynthetic organisms (Davison, 1993). Moreno et al. (2007)linked changes in Mn to lake-level variations.

Pearson’s correlation coefficients for each unit are given inTable 2. The elements Ti, Rb, and Zn are displayed in Fig. 3, while Zr,Si, and K together with the Zr/Rb-ratio are shown in Fig. 4. Fig. 5shows the elements Ca and Sr together with the Mn/Fe-ratio.


Table 2Pearson’s correlation coefficients.

Unit 52 Si K Ca Ti Mn Fe Zn Rb Sr Zr

Si 1,00 0,81 0,93 0,74 0,69 0,82 0,66 0,65 0,87 0,80

K 0,81 1,00 0,72 0,62 0,52 0,66 0,50 0,47 0,63 0,60

Ca 0,93 0,72 1,00 0,72 0,66 0,81 0,69 0,66 0,92 0,82

Ti 0,74 0,62 0,72 1,00 0,69 0,91 0,77 0,72 0,77 0,86

Mn 0,69 0,52 0,66 0,69 1,00 0,73 0,62 0,64 0,75 0,73

Fe 0,82 0,66 0,81 0,91 0,73 1,00 0,81 0,82 0,87 0,91

Zn 0,66 0,50 0,69 0,77 0,62 0,81 1,00 0,76 0,75 0,81

Rb 0,65 0,47 0,66 0,72 0,64 0,82 0,76 1,00 0,77 0,83

Sr 0,87 0,63 0,92 0,77 0,75 0,87 0,75 0,77 1,00 0,90

Zr 0,80 0,60 0,82 0,86 0,73 0,91 0,81 0,83 0,90 1,00


Si 1,00 0,45 0,84 0,00 0,46 0,06 0,24 -0,06 0,94 0,52

K 0,45 1,00 0,27 0,78 0,30 0,59 0,81 0,75 0,38 0,84

Ca 0,84 0,27 1,00 -0,26 0,78 0,30 0,16 -0,12 0,95 0,33

Ti 0,00 0,78 -0,26 1,00 -0,13 0,43 0,79 0,85 -0,11 0,74

Mn 0,46 0,30 0,78 -0,13 1,00 0,69 0,24 0,10 0,63 0,26

Fe 0,06 0,59 0,30 0,43 0,69 1,00 0,62 0,66 0,20 0,46

Zn 0,24 0,81 0,16 0,79 0,24 0,62 1,00 0,85 0,25 0,82

Rb -0,06 0,75 -0,12 0,85 0,10 0,66 0,85 1,00 -0,04 0,74

Sr 0,94 0,38 0,95 -0,11 0,63 0,20 0,25 -0,04 1,00 0,49

Zr 0,52 0,84 0,33 0,74 0,26 0,46 0,82 0,74 0,49 1,00


Si 1,00 -0,79 0,39 0,43 -0,47 -0,17 0,26 -0,29 -0,22 0,81

K -0,79 1,00 -0,07 -0,55 0,54 0,14 -0,19 0,33 0,55 -0,87

Ca 0,39 -0,07 1,00 -0,59 -0,15 -0,76 -0,15 -0,64 0,75 -0,05

Ti 0,43 -0,55 -0,59 1,00 -0,19 0,65 0,45 0,43 -0,84 0,73

Mn -0,47 0,54 -0,15 -0,19 1,00 0,31 -0,06 0,25 0,21 -0,50

Fe -0,17 0,14 -0,76 0,65 0,31 1,00 0,38 0,81 -0,57 0,12

Zn 0,26 -0,19 -0,15 0,45 -0,06 0,38 1,00 0,33 -0,27 0,39

Rb -0,29 0,33 -0,64 0,43 0,25 0,81 0,33 1,00 -0,38 -0,02

Sr -0,22 0,55 0,75 -0,84 0,21 -0,57 -0,27 -0,38 1,00 -0,60

Zr 0,81 -0,87 -0,05 0,73 -0,50 0,12 0,39 -0,02 -0,60 1,00

Unit 55a/b Si K Ca Ti Mn Fe Zn Rb Sr Zr

Si 1,00 0,77 0,55 0,49 0,37 0,79 0,31 0,32 0,01 0,05

K 0,77 1,00 0,40 0,57 0,01 0,74 0,28 0,35 0,05 0,07

Ca 0,55 0,40 1,00 -0,07 0,29 0,19 0,23 -0,13 0,68 0,17

Ti 0,49 0,57 -0,07 1,00 -0,08 0,77 0,29 0,45 -0,15 0,18

Mn 0,37 0,01 0,29 -0,08 1,00 0,21 0,09 0,20 -0,05 0,01

Fe 0,79 0,74 0,19 0,77 0,21 1,00 0,38 0,52 -0,24 0,10

Zn 0,31 0,28 0,23 0,29 0,09 0,38 1,00 0,18 0,16 0,18

Rb 0,32 0,35 -0,13 0,45 0,20 0,52 0,18 1,00 -0,33 0,15

Sr 0,01 0,05 0,68 -0,15 -0,05 -0,24 0,16 -0,33 1,00 0,34

Zr 0,05 0,07 0,17 0,18 0,01 0,10 0,18 0,15 0,34 1,00


Si 1,00 0,14 0,27 -0,02 -0,17 -0,25 -0,29 -0,29 0,27 0,22

K 0,14 1,00 0,61 -0,84 0,29 -0,68 -0,56 0,29 0,64 -0,84

Ca 0,27 0,61 1,00 -0,87 -0,09 -0,91 -0,81 -0,47 0,97 -0,65

Ti -0,02 -0,84 -0,87 1,00 -0,10 0,90 0,79 0,16 -0,89 0,89

Mn -0,17 0,29 -0,09 -0,10 1,00 0,15 0,11 0,45 -0,14 -0,24

Fe -0,25 -0,68 -0,91 0,90 0,15 1,00 0,90 0,45 -0,96 0,70

Zn -0,29 -0,56 -0,81 0,79 0,11 0,90 1,00 0,52 -0,86 0,59

Rb -0,29 0,29 -0,47 0,16 0,45 0,45 0,52 1,00 -0,50 -0,13

Sr 0,27 0,64 0,97 -0,89 -0,14 -0,96 -0,86 -0,50 1,00 -0,66

Zr 0,22 -0,84 -0,65 0,89 -0,24 0,70 0,59 -0,13 -0,66 1,00

Unit 57a Si K Ca Ti Mn Fe Zn Rb Sr Zr

Si 1,00 0,90 0,62 0,01 0,18 -0,36 -0,16 -0,14 -0,27 0,77

K 0,90 1,00 0,41 0,13 0,22 -0,37 -0,22 -0,06 -0,54 0,91

Ca 0,62 0,41 1,00 -0,64 -0,16 -0,39 -0,31 -0,56 0,47 0,22

Ti 0,01 0,13 -0,64 1,00 0,46 0,45 0,32 0,53 -0,59 0,23

Mn 0,18 0,22 -0,16 0,46 1,00 0,34 0,11 0,06 -0,37 0,28

Fe -0,36 -0,37 -0,39 0,45 0,34 1,00 0,21 0,18 0,12 -0,39

Zn -0,16 -0,22 -0,31 0,32 0,11 0,21 1,00 0,34 -0,05 -0,13

Rb -0,14 -0,06 -0,56 0,53 0,06 0,18 0,34 1,00 -0,33 0,05

Sr -0,27 -0,54 0,47 -0,59 -0,37 0,12 -0,05 -0,33 1,00 -0,70

Zr 0,77 0,91 0,22 0,23 0,28 -0,39 -0,13 0,05 -0,70 1,00

Unit 57b Si K Ca Ti Mn Fe Zn Rb Sr Zr

Si 1,00 0,45 0,04 0,31 0,37 0,35 0,15 0,27 0,11 0,01

K 0,45 1,00 -0,63 0,83 0,30 0,48 -0,18 0,65 -0,61 0,06

Ca 0,04 -0,63 1,00 -0,82 -0,29 -0,46 0,60 -0,59 0,91 0,38

Ti 0,31 0,83 -0,82 1,00 0,47 0,66 -0,37 0,67 -0,72 -0,24

Mn 0,37 0,30 -0,29 0,47 1,00 0,83 -0,27 0,26 -0,17 -0,46

Fe 0,35 0,48 -0,46 0,66 0,83 1,00 -0,32 0,29 -0,37 -0,42

Zn 0,15 -0,18 0,60 -0,37 -0,27 -0,32 1,00 -0,16 0,56 0,40

Rb 0,27 0,65 -0,59 0,67 0,26 0,29 -0,16 1,00 -0,40 -0,08

Sr 0,11 -0,61 0,91 -0,72 -0,17 -0,37 0,56 -0,40 1,00 0,12

Zr 0,01 0,06 0,38 -0,24 -0,46 -0,42 0,40 -0,08 0,12 1,00

Table 2 (continued)



4.3.1. Unit 52 (15e14.6 ka cal BP)Ti, Rb, and Zn, as well as Zr decrease towards 14.7 ka cal BP,

then reach a maximum at 14.6 ka cal BP at the transition to unit53. Si and Zr/Rb both decrease towards 14.6 ka cal BP, while Kdisplays no clear trend. Ca and Sr decrease towards 14.8 ka cal BP,then reach a maximum at 14.6 ka cal BP. Mn/Fe displays no cleartrend. All elements are correlated. Between 15 and 14.7 ka cal BP,clay mineral (Ti, Rb, Zn) and clastic (Zr) input to the lake decreasesindicating drying winter conditions in the catchment during thistime period. That Ca and Sr follow the decreasing trend of the claymineral and clastic assemblage might be due to the presence ofcarbonate detritus which is co-transported to the lake from thecatchment assumingly during winter and/or due to decreasedavailability of carbonate ions for chemical precipitation. At14.6 ka cal BP, wet winter conditions in the catchment prevail.Evaporation-driven, in-lake carbonate mineral precipitation be-tween 15 and 14.6 ka cal BP is not important, thereby indicatingdry summers.

R-values in red, italic are insignificant (p-value is >0.05).


56789101112131415

0

0.1

0.2

0.3

0.4

Age [cal ka BP]

Log(

Ti/A

l)

−1

−0.8

−0.6

Log(

Rb/

Al)

−1.6

−1.4

−1.2

−1

Log(

Zn/A

l)

567891011121314150

100

200

300

Age [cal ka BP]

κ [1

0-6]

ub u

53

ub u

52

ub u

54

ub u

55a

ub u

55b

ub u

56

ub u

57a

Prec

ipita

tion

(Win

ter)

low

high

surfa

ce ru

n-of

f

low

high

179177175173171169167165

Inso

latio

n (D

ecem

ber,

37°N

)[W

m-2

]

Ho

lo

cen

e

Fig. 3. XRF measurements of the elements Ti, Rb, and Zn log-normalized to Al, as well as magnetic susceptibility, from Lake Stymphalia core STY-1, as well as winter insolationplotted against age (ka cal BP). All elements indicate torrential river input and are associated with the clay mineral assemblage. Magnetic susceptibility indicates erosion in thecatchment and surface run-off to the lake. Winter insolation was calculated for 37�N according to Laskar et al. (2004). Dashed vertical lines represent gradational unit boundaries.Dashed horizontal lines depict mean values for the Late Glacial and Holocene time interval.


4.3.2. Unit 53 (14.6e13.1 ka cal BP)Ti, Rb, and Zn, as well as Zr increase towards 13.9 ka cal BP with

peaks at 14.4, 14.2, and 13.9 ka cal BP, then decrease towards13.4 ka cal BP. Minor peaks in Rb, Zn and Zr are centred between13.4 and 13.2 ka cal BP. Si continues its decreasing trend from unit52 towards 13.9 ka cal BP with minor peaks at 14.4, 13.9 and be-tween 13.4 and 13.2 ka cal BP. K displays no clear trend, only minorpeaks at 14.4, 13.9, and between 13.4 and 13.2 ka cal BP. Zr/Rbdisplays a decreasing trend from 14.6 to 13.1 ka cal BP. Ca and Srdecrease towards 13.7 ka cal BP, then start to increase. Major peaksare centred at 14.4, 14.2, 13.9, and 13.4e13.2 ka cal BP. Mn/Fe dis-plays a decreasing trend towards 13.5 ka cal BP indicating moreanoxic/low alkaline lake water conditions. A major peak and returntomore oxic/alkaline conditions is centred around 13.4 ka cal BP. Ti,Rb and Zn, as well as Zr, Si, and K are coupled. A strong linkagebetween Ca and Sr, as well as to Si exists. Mn and Fe are coupled,while Mn is more linked to Ca, and Fe to K.

Wet winter conditions in the catchment between 14.6 and13.9 ka cal BP are indicated by the clay mineral and clastic assem-blage, and supported by the carbonate minerals that indicate wetsummer conditions until 13.7 ka cal BP. High precipitation events inthe catchment occur at 14.4, 14.2, 13.9, and 13.4e13.2 ka cal BP. Thelatter is situated within a drier period between 13.9 and 13.7 and13.2 ka cal BP. Ca and Sr indicate dry summer episodes at 14.4, 14.2,13.9, and 13.4e13.2 ka cal BP because they are decoupled from the


clay/clastic mineral assemblage. Mn/Fe indicates higher lake levelsand/or decreased wind stress and mixing of the water column to-wards 13.5 ka cal BP. Lower lake levels and/or increased wind stressand mixing of the water column is suggested by Mn/Fe around13.4 ka cal BP.

4.3.3. Unit 54 (13.1e10.5 ka cal BP)While Rb displays no clear trend, Ti and Zn, as well as Zr and Si

decrease towards 10.5 ka cal BP. Minor peaks in Ti and Rb arecentred between 11.1 and 11 ka cal BP. K is increasing towards10.5 ka cal BP. Zr/Rb decreases towards 10.5 ka cal BP with a majorshift to lower values around 12.1 ka cal BP. Ca and Sr increase to-wards 12.1 ka cal BP, and then decrease towards 11 ka cal BP. Minorpeaks in Ca and Sr are centred at 10.8e10.7 ka cal BP. Mn/Fe in-crease towards 10.5 ka cal BP with peaks at 11.9 and 10.8 ka cal BPindicating more oxic/alkaline lake water conditions.

Ti, Rb, and Zn are coupled. Ti is also linked to Zr, Si, and Fe. Ca iscoupled to Sr. Both elements are anti-correlated to Rb, Ti, and Fe,while Sr is also anti-correlated with Zr. K is anti-correlated to Si andZr, but linked to Sr and Mn. Mn and Fe are correlated.

Dry winter/summer conditions in the catchment prevail. At12.1 ka cal BP, driest summer conditions occur as indicated byCa and Sr which are now clearly linked to in-lake carbonate pre-cipitation. An increase in winter/summer humidity is centred at11 ka cal BP as indicated by Ti, Rb, Ca and Sr. The drying trend


56789101112131415

−0.8

−0.6

−0.4

−0.2

0

Age [cal ka BP]

Log(

Zr/

Al)

0.8

0.9

1

1.1

Log(

Si/A

l)

0.3

0.4

0.5

0.6

0.7

Log(

K/A

l)

56789101112131415

0.2

0.4

0.6

0.8

Age [cal ka BP]

Log(

Zr/

Rb)

ub u

52

ub u

53

ub u

54

ub u

55a

ub u

55b

ub u

56

ub u

57a

surfa

ce ru

n-of

f

low

high

grai

n si

ze

clay

silt

Fig. 4. XRF measurements of the elements Zr, Si, and K log-normalized to Al, and Zr/Rb-ratio from Lake Stymphalia core STY-1 plotted against age (ka cal BP). All elements indicatetorrential river input and are associated either with the clastic mineral and/or clay mineral assemblage. Zr/Rb indicates grain size changes, mainly silt versus clay content. Dashedvertical lines represent gradational unit boundaries. Dashed horizontal lines depict mean values for the Late Glacial and Holocene time interval.


continues until 10.5 ka cal BP. Mn/Fe suggests low lake levels and/orincreased wind stress and mixing of the water column.

4.3.4. Unit 55a/b (10.5e8.5 ka cal BP)Ti, Si, and K decrease towards 8.5 ka cal BP, while Rb, Zn, and Zr

display no clear trend. A minor peak in Ti is centred at 9.8 ka cal BP,in Zr and Zn at 8.7 ka cal BP. Zr/Rb displays no clear trend withminor peaks centred at 10.1 and 8.7 ka cal BP. At 10.5 ka cal BP Caand Sr markedly increase. Major peaks in both elements centre at9.5, 9.3, and 8.7 ka cal BP. After 8.7 ka cal BP both elements display adecreasing trend towards 8.5 ka cal BP. Mn/Fe sharply increase atthe onset of unit 55a at 10.5 ka cal BP indicating more oxic/alkalineconditions, then decrease towards 9.2 ka cal BP with a shift to moreanoxic/low alkaline lake water conditions. A marked increase inMn/Fe peaks around 9 ka cal BP. After 9 ka cal BP Mn/Fe decreasetowards 8.5 ka cal BP.

Ti, Rb, and Zn are correlated and linked to Si and K which areboth coupled. Si and K are also linked to Fe and Ca. Ca and Sr arecoupled. Sr is correlated with Zr, but anti-correlatedwith Fe and Rb.Mn and Fe are correlated, but Fe exhibits a stronger linkage to Rband Ti. Mn is also correlated to Si, Ca, and Rb.

Dry conditions prevail in the catchment between 10.5 and8.7 ka cal BP. At 10.5 ka cal BP, a marked increase in summer aridity


is indicated by Ca and Sr. Minor high precipitation events (winter)in the catchment are centred at 10.1, 9.8, and 8.7 ka cal BP, while drysummer episodes are centred at 9.5, 9.3, and 8.7 ka cal BP. After8.7 ka cal BP, summer conditions in the catchment become wetter.Mn/Fe suggests low lake levels and/or increased wind stress andmixing of the water column at 10.5 ka cal BP, and 9 ka cal BP. Be-tween 10.5 and 9.2 ka cal BP, and 9 and 8.5 ka cal BP, Mn/Fe suggestshigher lake levels and/or reduced wind induced mixing of thewater column.

4.3.5. Unit 56 (8.5e7.3 ka cal BP)Ti, Rb, and Zn increase towards 7.3 ka cal BP. Ti sharply increases

at 8 ka cal BP with a pronounced peak at 7.7 ka cal BP. Zn also startsto increase at 8 ka cal BP. A major peak in Rb is centred at7.5 ka cal BP. Zr and Zr/Rb increase towards 7.7 ka cal BP which isalso marked by major peaks. After 7.7 ka cal BP, Zr and Zr/Rbdecrease towards 7.3 ka cal BP. Si decreases towards 7.3 ka cal BP,with a major peak centred at 7.7 ka cal BP. K sharply decreases after8.2 ka cal BP reaching lowest values at 7.8 ka cal BP. A major peak inK is centred at 7.6 ka cal BP. Ca and Sr decrease towards 7.5 ka cal BP.A sharp decrease after 8.1 ka cal BP reaches is lowest values at7.5 ka cal BP, then Ca and Sr rise again. A major peak in both ele-ments is centred between 7.7 and 7.6 ka cal BP. Mn/Fe decreases


56789101112131415

1

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2.5

Age [cal ka BP]

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Log(

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l)

56789101112131415−2.2

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Age [cal ka BP]

Log(

Mn/

Fe)

Evap

orat

ion

(Sum

mer

)

low

high

Oxi

c St

ate

(Alk

alin

ity)

anoxic(low)

oxic(high)

ub u

52

ub u

53

ub u

54

ub u

55a

ub u

55b

ub u

56

ub u

57a

Inso

latio

n (J

une,

37°

N)

[Wm

-2]

520

515

510

505

500

495

490

485

480

Ho

lo

ce

ne

Fig. 5. XRF measurements of the elements Ca and Sr log-normalized to Al, and Mn/Fe-ratio from Lake Stymphalia STY-1 sequence, as well as summer insolation plotted against age(ka cal BP). Ca and Sr are linked to in-lake carbonate precipitation. Mn/Fe indicates the oxic/alkalinity state of the lake and indirectly points to lake level status. Summer insolationwas calculated for 37�N according to Laskar et al. (2004). Dashed vertical lines represent gradational unit boundaries. Dashed horizontal lines depict mean values for the Late Glacialand Holocene time interval.


towards 7.5 ka cal BP with a major peak at 8.2 ka cal BP indicatinganoxic/low alkaline lake water conditions. After 7.5 ka cal BP, Mn/Feincreases pointing to more oxic/alkaline lake water conditions.

Ti, Rb, and Zn are correlated. Rb, Zn, and Ti are linked to Fe, whileZn and Ti are also coupled to Zr. Ti, Rb, and Zn are anti-correlatedwith Ca and Sr. Si is correlated to Zr, Ca and Sr, and anti-correlated to Rb, Zn and Fe. K is anti-correlated with Zr, Ti, Zn,and Fe. Ca and Sr are coupled. Both elements are correlated to K, butanti-correlated to Fe and Zr. Mn is correlated to Rb and K.

Between 8.5 and 7.3 ka cal BP, wet winter/summer conditionsprevail within the lake catchment with a marked increase in hu-midity at 8 ka cal BP. Wettest winter conditions occur at7.7 ka cal BP with a dry summer episode centred between 7.7 and7.6 ka cal BP. Mn/Fe suggest high lake levels and/or reduced windinduced mixing of the water column until 7.5 ka cal BP. After7.5 ka cal BP lake levels become lower and/or wind stress increasesleading to mixing of the water column.

4.3.6. Unit 57a/b (7.3e5 ka cal BP)Ti, Rb, and Zn display no clear trend. Zr, Zr/Rb, Si, and K increase

towards 5 ka cal BP. Ca and Sr continue the rising trend from unit56, but start to decline after 7 ka cal BP. Around 6.1 ka cal BP, both


elements start to increase again towards 5 ka cal BP. Mn/Fe in-creases towards 6.1 ka cal BP indicating oxic/alkaline lake waterconditions, then sharply declines to an anoxic/low alkaline lakewater status. After 6 ka cal BP Mn/Fe increases towards 5 ka cal BP.

Ti, Rb, and Zn are correlated. Ti is also linked to Zr, Fe, Mn, andanti-correlated to Ca and Sr. Si is linked to Zr, K, Mn and Ca, andanti-correlated to Sr and Fe. Zr and K are coupled. K is correlatedwith Ca, but anti-correlated with Sr. Ca and Sr are correlated, butanti-correlated to Rb. Mn and Fe are linked, while Mn is alsocoupled to Zr and anti-correlated with Sr.

Wet winter conditions exist between 7.3 and 5 ka cal BP, but theclimate is less humid than in the previous time period. Clear trendsare only present in summer conditions. Until 7 ka cal BP summeraridity increases, but starts to decline afterwards. After 6.1 ka cal BPsummer aridity increases again. Mn/Fe suggests low lake levelsand/or increased wind stress and mixing of the water column be-tween 7.3 and 5 ka cal BP with a high lake level and/or wind stressinduced mixing of water column episode around 6.1 ka cal BP.

4.3.7. Time slicesSedimentary units were combined in time slices for Late Glacial,

Early Holocene, and Mid-Holocene in order to study elemental



behaviour during these time periods. Fig. 6 shows correlograms (i.e.matrices of Pearson’s correlation coefficients) for thewhole data set(6a) and the three selected time slices (6be6d). The observed cor-relations in the Late Glacial time slice (Fig. 6b) resemble predomi-nantly the elemental behaviour within the lower part of unit 54,while elemental relationships of units 52 and 53 are of minorimportance. The correlation of carbonate and clay/clastic minerals,for instance, indicates co-transport of carbonate detritus to thelake, when considering the larger time span. Here, strong correla-tions between Ca and Sr, as well between Ti, Rb, Zn, and Zr exist.The clay/clastic mineral groups, especially Ti and Rb, are anti-correlated or not significantly correlated to the carbonates. Si, K,Mn, and Fe play an intermediate role due to their affinity to allgroups. The Early Holocene (Fig. 6c) is reflected in the elementalbehaviour as seen in units 54 (upper part), 55a/b, and 56 (lowerpart). Strong correlations between Ca and Sr, as well as between Ti,

Fig. 6. Pearson correlation matrices of elemental pairs for selected time slices of the Lake SElements are log-normalized to Al. Strong positive correlations of elemental pairs are indicaintervals for correlation coefficients are given in brackets. (For interpretation of the reference


Rb, Zn, and Zr exist. Anti-correlations between the carbonate groupand the clay/clastic groups are more pronounced than in the LateGlacial time period. Si, K, Mn, and Fe are associated with the car-bonate and clay/clastic groups. The mid-Holocene time slice(Fig. 6d) as reflected in the elemental behaviour of units 56 (upperpart) and 57a/b shows only minor changes in comparison to theEarly Holocene. Time slice correlation matrices confirm the twomajor processes that steer the chemical composition of LakeStymphalia sediments: catchment precipitation and hence fluvialinput/surface run-off to the lake during winter, and in-lake car-bonate precipitation during summer.

4.4. Rb/Sr-ratio as a hydroclimate proxy

Rb/Sr can be used as proxy for chemical weathering in thecatchment and pedogenesis (Jin et al., 2001, 2006a). High Rb/Sr

tymphalia sequence. (n refers to the number of data points for the given time interval.)ted by dark bluish colors, while strong anti-correlations are depicted in red. Confidences to colour in this figure legend, the reader is referred to the web version of this article.)



values in lake sediments correspond to reduced catchmentweathering with a low flux of Sr to the basin. Enrichment in Srwithin lake sediments and hence low Rb/Sr values reflect enhancedchemical weathering in the catchment. Sr is preferentially leachedfrom soils under wet conditions.

In Lake Stymphalia, different processes were at work. Rb islinked to the clay mineral assemblage and transported to the lakeby torrential rivers in times of enhanced precipitation in thecatchment. The present day subtropical moisture regime in theEastern Mediterranean is governed by winter precipitation due to asouthward migration (weakening) of the subtropical highs andenhanced influence of mid-latitude westerlies/cyclones (Lauer andBendix, 2006). Cullen and deMenocal (2000) showed that theSoutheastern Mediterranean precipitation regime is influenced bythe North Atlantic Oscillation (NAO) which in its negative modewould cause enhanced precipitation in the Eastern Mediterranean.In terms of atmospheric circulation patterns, Feidas et al. (2007)relate high precipitation over Greece in winter accompanied bywarmer temperatures to a southern meridional flow and a troughextending to the central Mediterranean. In a positive winter NAOmode, Greece becomes cooler and drier due to a northerly air flowwhich brings cool and dry continental air to the Eastern Mediter-ranean (Feidas et al., 2007). Changes in the NAO are linked to solaractivity which is high (low) when the NAO is in its negative

1010.51111.51212.51313.51414.515

60

40

20

0

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-60

Age [ka

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Cre

sidu

al [‰

]

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LC21

, Sou

th A

egea

n Se

aw

arm

spe

cies

[%]

LC21 chronologytuned to GISP2 chronology

Bølling-Allerød Younger Dryas

Hum

idity

(“P/E

-ratio

“)

low

high

Hyd

rolo

gy

arid

humid

ub u

52

ub u

53

ub u

54

ub u

55a

No

te

in

ve

rte

d a

xis

Fig. 7. Rb/Sr from Lake Stymphalia sequence in relation to the warm species record of core LCthe stable oxygen-isotope record of speleothems from Soreq Cave, Israel (Bar-Matthews et al., 1solar activity. Dashed vertical lines represent gradational unit boundaries in core STY-1. TheYounger Dryas cold period and Holocene time periods of rapid climate change (RCC) accordingare due to the fact that the LC21 core chronology is based on AMS 14C dates and synchronizatiUeTh ages. For further discussion see text. (For interpretation of the references to colour in


(positive) mode (e.g Ineson et al., 2011; Georgieva et al., 2012).Therefore, an increase (decrease) in Rb indicates a wet/mild (dry/cool) winter climate corresponding to high (low) solar activity atleast during the Holocene. Sr on the other hand is linked to Ca andin-lake precipitation of carbonates, preferentially during the sum-mer season when air temperatures are generally higher. TheEastern Mediterranean temperature regime during warm summersis related to atmospheric blocking conditions, subsidence, andstability (Xoplaki et al., 2003) that correspond to a negative sum-mer NAO mode (Feidas et al., 2007). Feidas et al. (2007) showed asignificant correlation of summer NAO with the precipitation/temperature regime over Greece. In a positive summer NAO mode,the Azores high pressure system is strengthened and extends tocentral and northern Europe while climatic conditions in theMediterranean become unstable and precipitation is enhanced.Thus an increase (decrease) in Sr reflects time periods of high (low)evaporation met under a drier/warmer (wetter/cooler) summerclimate corresponding to low (high) solar activity at least duringthe Holocene. Hydrochemical analysis of karst springs and lakewaters suggest that Sr is directly derived from dissolution of car-bonate rocks rather than from leaching of soils (Morfis and Zojer,1986). Therefore, a high Rb/Sr-ratio reflects wetter climatic condi-tions corresponding to high solar activity and lowRb/Sr values drierclimatic conditions corresponding to low solar activity (Fig. 7).

55.566.577.588.599.5BP]

55.566.577.588.599.5

−7

−6

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−4

P]

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−1

−0.5

0

Lake

Sty

mpa

hlia

Log(

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q C

ave,

Isra

elδ18

Osp

eleo

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te

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RCC 6-5 ka BP

Sola

r Act

ivity

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high

Sea

Surfa

ce

Tem

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ture

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warm

ub u

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ub u

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8.2

even

tRCC 9-8 ka BP

21 from the Southern Aegean Sea (Rohling et al., 2002) indicating temperature changes,999) indicating humidity changes, and the d14C record (Stuiver et al., 1998) which depictsshaded yellow interval indicates the BøllingeAllerød. Shaded blue intervals indicate theto Mayewski et al. (2004). Offsets in ages between LC21, Soreq Cave and Lake Stymphaliaon to Greenland ice core records, and the Soreq Cave speleothem chronology is based onthis figure legend, the reader is referred to the web version of this article.)



Between 15 and 14.6 ka cal BP dry conditions prevail (low Rb/Sr).After 14.6 ka cal BP, Rb/Sr values increase sharply towards wetterconditions that might represent the BøllingeAllerød. Wettestclimate is marked by highest Rb/Sr-ratio between 13.8 and13.7 ka cal BP. A drop in Rb/Srwith aminimum around 13.2 ka cal BPmost likely represents the onset of the Younger Dryas. From ca. 13.2to 12.1 ka cal BP, the Rb/Sr-ratio declines, indicating a shift to drierclimatic conditions. This time period might represent the YoungerDryas. After 12.1 ka cal BP Rb/Sr increases, probably marking theonset of the Holocene in this record. A transition to wetter climateoccurs with peak conditions reached around 11 ka cal BP. At10.8 ka cal BP a decrease in Rb/Sr and a shift to a drier climate occurs.Low values in Rb/Sr, dry conditions prevail until 8.5 ka cal BP, fol-lowed by a steep rise in Rb/Sr indicating a transition to a wetterclimate.Wettest conditions are established around 7.6e7.5 ka cal BP.After 7.5 ka cal BP Rb/Sr starts to decline, reaching a minimum and afully return to drier conditions between 7.1 and 7 ka cal BP. A returnto wetter conditions after 5.8 ka cal BP is marked by a rise in Rb/Sr.A wet climate prevailed until ca. 5 ka cal BP.

4.5. Spectral analysis

Spectral analysis was performed on the Rb/Sr record from LakeStymphalia using REDFIT (Schulz andMudelsee, 2002). Fig. 8 showsfour different time series, equivalent to the periods discussed inChapter 4.3.7 in the context of the correlograms. Statistically sig-nificant periodicities are reported at the 90% confidence level. Theentire data set (15e5 ka cal BP, the Late Glacial to mid-Holocenerecord) shows periodicities at 870, 238, 182, 118, 90, 77, 67, 53,40, 20, and 18 y (Fig. 8a). The Late Glacial (15e11.7 ka cal BP) shows

Fig. 8. Spectral analysis results for the Rb/Sr time series of Lake Stymphalia composite corefrom 15 to 5 ka cal BP, (b) the Late Glacial time period from 15 to 11.7 ka cal BP, (c) the early8 to 5 ka cal BP.


periodicities at 213, 167, 88, 40, 34, 30, and 21 y with a time reso-lution of 6e9 y (Fig. 8b). The early Holocene (11.7e8 ka cal BP)shows periodicities at 417, 238, 175, 110, 87, 80, 29, and 22 y witha time resolution of 9 y (Fig. 8c). The mid-Holocene (8e5 ka cal BP)shows periodicities at 233, 196, 158, 116, and 19 y with a timeresolution of 5e8 y (Fig. 8d).

5. Discussion

Are the recorded environmental variations in Lake Stymphaliamerely local events or a reflection of regional climate change? Chenet al. (1999) matched the Rb/Sr variations recorded in a loess-paleosol sequence from central China to marine d18O data fromthe region indicating a strong linkage to major changes in the EastAsian monsoon. Variations in the Rb/Sr-ratio of Lake Stymphaliarecord climate change over the Eastern Mediterranean region. TheRb/Sr-ratio is clearly matched to the foraminiferal record of marinecore LC21 from the Southern Aegean (Rohling et al., 2002; Marinoet al., 2009) and the d18Ospeleothem record of Soreq Cave, Israel(Bar-Matthews et al., 1999), as well as the d13C record of solar ac-tivity by Stuiver et al. (1998; Fig. 7). The following section assessesthe linkage of Lake Stymphalia to LC21, Soreq Cave, and otherpalaeoclimate data from the region and evaluates it against themajor climatic development of the Eastern Mediterranean duringthe Late Glacial to mid-Holocene.

5.1. Late Glacial (15e11.7 ka BP)

Dry climatic conditions as indicated by the elemental proxiesprevail until 14.7 ka cal BP and most likely represent the Oldest

section STY-1. Four different time intervals were analyzed: (a) the whole time intervalHolocene interval from 11.7 to 8 ka cal BP, and (d) the mid-Holocene time period from



Dryas. Winter precipitation within the catchment is low, whilesummers are also dry. Between 14.8 and 14.7 ka cal BP summersbecome wet. There is no evidence of glaciers after 15 ka BP in themountainous regions of the Peloponnese (Hughes et al., 2006),including Mt. Kyllini, thus changes in catchment hydrology reflectchanges in precipitation and not in meltwater input. Pollen-basedquantitative precipitation reconstructions of core SL152 from theAegean Sea also indicate dry (winter) conditions of the NorthernAegean borderlands (Dormoy et al., 2009). Dry climatic conditionsare also evident in the pollen records of Lake Maliq, Albania(Bordon et al., 2009) and Tenaghi Philippon, Greece (Wijmstra,1969), and the speleothem stable isotope record of Soreq Cave,Israel (e.g., Bar-Matthews et al., 2003). A shift to humid conditionsoccurs around 14.7 to 14.6 ka cal BP. Winter precipitation increases,while summers are dry. After 14.6 ka cal BP, precipitation in sum-mer also increases. Organic matter content is low to modest in theLate Glacial indicating low to moderate productivity or enhanceddecomposition of organic matter. More anoxic (low alkaline) lakewater conditions which would preserve organic matter and whichmost probably reflect a higher lake level within the shallow littoralfacies zone prevail at least between 14.6 and 13.5 ka cal BP. Thus,organic matter content might represent a productivity signal. Thisperiod corresponds roughly to the BøllingeAllerød interval inhigher latitudes. Moist conditions in the Northern Aegean border-lands during the BøllingeAllerød are also evident in the pollen-based climate reconstructions of core SL152 (Dormoy et al.,2009). In contrast to the Western Mediterranean, a Mediterra-nean type rainfall regime with hot, dry summers and cool, wetwinters (Dormoy et al., 2009) is less marked in the Aegean Sea andis only indicated from 14.7 to 14.6 ka cal BP, and 13.4 to13.2 ka cal BP at Lake Stymphalia. The d18Ospeleothem record of Soreqcave, Israel indicates humid conditions during the BøllingeAllerødin the Levant (Bar-Matthews et al., 1999).

After 13.9 ka cal BP, climatic conditions as indicated by theelemental proxies of the Lake Stymphalia sequence become drier.From 13.9 to 13.4 ka cal BP, winter and summer precipitation is low.At 13.4 ka cal BP humid conditions in winter with dry summersreoccur and last until 13.2 ka cal BP. The return to moisture con-ditions around 13.4 ka cal BP is also supported by a rise in magneticsusceptibility indicating enhanced erosion in the catchment. Lakewater conditions are oxic (alkaline) suggesting increased windinduced mixing of the water column.

At 13.2 ka cal BP a shift to a drier climate with low winter pre-cipitation but humid summers marks the onset of the YoungerDryas at Lake Stymphalia. This period lasts until 12.1 ka cal BP atLake Stymphalia. Lake water conditions are oxic (alkaline) indi-cating most likely a lower lake level, rather than increased windstress. A reduction in winter precipitation enhances the probabilityof hiati in the sediment sequence of Lake Stymphalia. That is, if drywinters are accompanied by dry summers and the lake level is lowenough, evaporative processes can diminish the water column bythe end of the summer/early fall season. But dry periods seem to benot long enough, not longer than a couple of years, to actually erodematerial away and/or that no material is deposited at all leavingphysical evidence in the sediment in terms of a sharp sedimentboundary. A decrease in precipitation (winter and annual) is alsoobserved in core SL152 for the Northern Aegean borderlands(Dormoy et al., 2009). Dormoy et al. (2009) reconstructed wettersummer conditions for the North Aegean Sea. Bordon et al. (2009)depicted arid winter conditions and wetter summer conditionsfrom the pollen sequence of Lake Maliq, Albania. Low sea surfacetemperatures for the Younger Dryas are reconstructed from fora-minifera of core LC21 in the South Aegean sea (Rohling et al., 2002).The d18Ospeleothem record of Soreq Cave, Israel indicates arid con-ditions during the Younger Dryas in the Levant (Bar-Matthews


et al., 1999). This is in agreement with the current interpretationof the Younger Dryas event (Renssen et al., 2001).

5.2. Early Holocene (11.7e8 ka BP)

The Late Glacial to Early Holocene transition is marked by a shiftin Rb/Sr to a wet climate around 12.1 ka cal BP at Lake Stymphalia.These conditions prevailed until 10.8 ka cal BP. Increasing carbonateprecipitation suggests drier summers until 11.1 ka cal BP. This trendis reversed until 10.9 ka cal BP. The precipitation regime inwinter issomehow different. Here, the influence of vegetation cover in thecatchment might be of importance. A dense vegetation cover undera humid climate would decrease erosion in the catchment by sta-bilizing the soils and thus transport of clastic/clay material to thelake, leading to a decreasing signal in the respective elements whenconsidering absolute concentrations. Lake Stymphalia would onlyreceive water from the karst springs which are contact springs(Morfis and Zojer, 1986) and not from (torrential) rivers. All theclay/clastic proxies with the exception of Rb and K suggestdecreasing precipitation in the catchment until 10.5 ka cal BP. HighK values indicate increasing clastic supply to the lake, while Rbpoints to stable clay mineral input. From 10.5 to 8.5 ka cal BP, Ti, Si,and K indicate decreasing minerogenic input to the lake, and thusdry winter conditions, while Rb, Zn, and Zr suggest stable clastic/clay input. A climatic shift to drier conditions around 10.8 ka cal BPis indicated by Rb/Sr and these dry conditions prevail until8.5 ka cal BP, although short-term humid winter conditions arecentred around 9.8 and 8.7 ka cal BP. Between 10.5 and 8.7 ka cal BP,summers are also dry. This is also indicated by the carbonate con-tent which is highest around 10.2 ka cal BP. A shift to more humidsummers occurs around 8.7 ka cal BP and these summer conditionsprevail until 8.5 ka cal BP. Mn/Fe indicates anoxic lake conditions,and thus a higher lake level and/or decreased wind stress around10.5e9.2, and 9e8.5 ka cal BP. Lake levels are low and/or windstress and thus mixing of the water column is increased between12.1 and 10.5, and 9.2e9 ka cal BP, respectively. Organic mattercontent is lowest around 11.6 ka cal BP, but Mn/Fe indicatesenhanced decomposition of organic matter in an oxic lake envi-ronment around this time.

The Rb/Sr-record of Lake Stymphalia shows a slight age offset ofa couple of hundred years when correlated to core LC21 (Rohlinget al., 2002) and Soreq cave (Bar-Matthews et al., 1999). The ageedepth model of LC21 is based on AMS 14C dates, but synchronizedto Greenland GISP2 ice cores (Marino et al., 2009), while the ageedepth model of Soreq cave is based on U-/Th-ages (Fig. 7). The AMS14C ages of core STY-1 in the mid-Holocene to Late Glacial part arenot corrected for any reservoir effect. Thus Lake Stymphalia agesseem to appear a couple of hundred years (�600 yrs) older. Pitfallsexist when correlating different palaeoclimatic proxy time seriesbased on independent chronologies (Blaauw et al., 2010; Blaauw,2012).

The wet climatic conditions at Lake Stymphalia between 12.1and 10.8 ka cal BP inferred from Rb/Sr are in agreement with coreLC21 and d18Ospeleothem of Soreq cave. In case of core LC21, a tem-perature increase from the Younger Dryas to the early Holocene isrecorded, while the d18Ospeleothem of Soreq Cave indicates shift tohumid conditions during the same time period. Increasing tem-peratures correspond to an increase in precipitation due toenhanced cyclogenesis over the Eastern Mediterranean region.

Dry conditions at Lake Stymphalia as indicated by Rb/Sr be-tween 10.9 and 8.5 ka cal BP are in possible contradiction withmarine core LC21 from the Southern Aegean, and d18Ospeleothemof Soreq cave, Israel. Supportive evidence for the climate re-constructions of Lake Stymphalia comes from Tzedakis (2007) whoinfers from palynological, lake level, and lake isotopic data an



increase in summer aridity in contrast to enhanced precipitationin the northern borderlands of the Eastern Mediterranean duringtimes of marine sapropel deposition. According to Jalut et al.(2009), various regional climates prevailed in the circum-Mediterranean during the early Holocene. Peyron et al. (2011)doubt moist conditions prevailed everywhere in the Mediterra-nean prior to 8 ka cal BP.

Between 10.7 and 9.7 ka BP, core LC21 records a �1.3& shift ind18Oseawater which reflects a shift to fresher sea surface water con-ditions in the South Aegean Sea in response to increased freshwaterdischarge along the North African margin (Marino et al., 2009)which is caused by orbitally driven fluctuations in the Africanmonsoon system (Rossignol-Strick et al., 1982; Rohling and Hilgen,1991; Rohling et al., 2004, 2009; Marino et al., 2007). This isaccompanied by a similar shift in d18Ospeleothem of Soreq cave, Israelwhich indicates moist conditions in the Levant during this timeperiod (Bar-Matthews et al., 1999, 2000) or changes in the isotopiccomposition of the Aegean-Levantine moisture source (Marinoet al., 2009). An intensification of the African monsoon systemand a northward shift of the Intertropical Convergence Zone (ITCZ)in Northern Hemisphere summer would also shift the descendingbranch of the Hadley cell further north leading to increased sum-mer aridity over Southern Greece. Peyron et al. (2011) summarizethe climate reconstructions for the early Holocene, especially thetime period between 9.5 and 7.8 ka cal BP often referred to as“Holocene optimum”. The northern rim of the Eastern Mediterra-nean as reconstructed from the pollen record of Tenaghi Philipponis characterized by wet winters and dry summers with a highdegree of seasonality (Peyron et al., 2011). Recent precipitationdata from Greece suggests a WesteEast/NortheSouth trend ofdecreasing winter precipitation (Tolika and Maheras, 2005;Hatzianastassiou et al., 2008). If such a gradient also existed duringthe early Holocene, this is an explanationwhy at Tenaghi Philipponin Northern Greece winters are very wet and warm, and summersdry and warm, while at Lake Stymphalia in Southern Greece win-ters and summers are dry.

After 8.5 ka cal BP, Rb/Sr indicates a shift to a more humidclimate with peak conditions around 7.5 ka cal BP, although dryreversals are normal. This trend is in agreement with LC21recording a shift to warmer temperatures after the 8.2 ka BP event,and Soreq cave d18Ospeleothem indicating moist conditions after8 ka BP.

5.2.1. The 8.2 ka eventA short-lived shift to drier conditions can be seen in the Rb/Sr

record at Lake Stymphalia centred at 8.3 ka cal BP (Fig. 7). Bothwinter and summer conditions are dry. An increase in Mn/Fe cen-tred at 8.2 ka cal BP indicates oxic/alkaline lake water conditionsand points to a low lake level. This might correspond to a regionalexpression of the 8.2 ka event (Alley et al., 1997). The 8.2 ka event isalso evident in other records from the Mediterranean region(Magny et al., 2003, 2006, 2007; Davis and Stevenson, 2007;Kotthoff et al., 2008a,b; Pross et al., 2009). The Northern hemi-sphere cooling event at 8.2 ka BP is a temperature anomaly incentral Greenland ice cores which is caused by a meltwater outflowinto the North Atlantic ocean thereby slowing down the NorthAtlantic Deep Water formation (Rohling and Palike, 2005). Rohlingand Palike (2005) state that this event is superimposed on a longterm cooling trend which started around 8.5 ka BP due to solarvariability. At Lake Stymphalia, peak dry conditions occur around8.7 ka cal BP as indicated by Rb/Sr (Fig. 7) and correspond to a shiftto cooler temperatures in core LC21 (Southern Aegean), drier con-ditions in the Levant (Soreq cave, Israel), and low solar activity(d14C). Marino et al. (2009) linked a cooling event centred around8.2 ka BP in the central Aegean to Greenland d18Oice thereby


supporting the model of a reduction in the early Holocene AtlanticMeridional Overturning Circulation (AMOC) in response to fresh-water release(s) from the retreating Laurentide ice sheet. Trans-mission of the 8.2 ka event must have been of atmospheric nature(Marino et al., 2009).

In direct comparison of Lake Stymphalia to the SouthernAegean, core LC21 indicates a shift to cooler sea surface tempera-tures at 8.2 ka cal BP (Rohling et al., 2002). The d18O record of Soreqcave, Israel indicates dry conditions around 8.2 ka BP in the Levant(Bar-Matthews et al., 1999). A precipitation decrease in the Levantand Eastern Mediterranean is also supported by the d13C record ofSoreq Cave, Israel (Bar-Matthews et al., 1999).

5.3. Mid-Holocene (8e5 ka BP)

The elemental proxies indicate wet winter and summer condi-tions from 8 to 7.5 ka cal BP. This is supported by a facies changeindicating a higher lake level accompanied by lake anoxia andpreservation of organic matter or enhanced productivity due to anincrease in solar activity. Increases in magnetic susceptibilityindicate humid conditions in the catchment. Summer conditionschange after 7.5 ka cal BP to increasing dryness that lasts until7 ka cal BP. A general shift to a dry climate is also indicated by Rb/Srwith peak dry conditions around 7 ka cal BP. Then after 7 ka cal BP,summers become wetter. Around 6.1 ka cal BP climatic conditionsin winter become drier, but Rb/Sr indicates a general shift to awetter climate around 5.8 ka cal BP.

Core LC21 indicates a shift to cool temperatures that is estab-lished around 7 ka cal BP (independent LC21 chronology). In theLevant, d18Ospeleothem of Soreq cave suggests a shift to arid condi-tions around this time. This coincides with peak dry conditions atLake Stymphalia. After 7 ka cal BP, core LC21 shows an oppositetrend to cooler temperatures in contrast to Lake Stymphalia, whiled18Ospeleothem of Soreq cave indicates a return to humid conditionsafter 6.5 ka BP in agreement with Lake Stymphalia. Rohling et al.(2002) connect the cool events as recorded in core LC21 in theSouthern Aegean to winter-time northerly air outbreaks over long-term periods (multi-decadal) of increased intensity, duration, and/or frequency that occur today inmuch smaller scale in the NorthernAegean. These cool polar air outbreaks during winter-time implydry conditions at least in the Aegean borderlands. The oppositetrend after 7 ka cal BP in LC21 compared to Lake Stymphalia impliesthat this cool northerly polar air flow extended into the SouthernAegean, but not over the Peleponnese.

Climate conditions in the Eastern Mediterranean region becamemore similar to the present day after 7 ka cal BP (Bar-Matthewset al., 1999). A mid-Holocene humid event around 5 ka BP asdescribed by Robinson et al. (2006) is not present in the LakeStymphalia record. However, wet conditions between 5.8 and5 ka cal BP inferred from Lake Stymphalia are also evident in otherrecords from the EasternMediterranean (Finné et al., 2011). Humanimpact on sediment dynamics in Lake Stymphalia and hence thevariations in the elemental suite is first of importance after 5 ka BPduring the Bronze age (Dusar et al., 2012).

5.4. Natural cyclicity in the Rb/Sr record

The Rb/Sr record from Lake Stymphalia documents significantLate Glacial and Holocene climate variability at (multi-)centennialto interdecadal scales. However, the spectral analysis of the Rb/Srrecord does not show significant power at millennial frequenciesfor the time period 15e5 ka cal BP. Despite this absence, the recordcan be linked to the proxy record of core LC21 which in turn iscorrelated to the Greenland ice core record. Mid- to high-latitudeatmospheric circulation patterns in winter and low-latitude



patterns which are determined by processes in the North AtlanticOcean, such as the thermohaline circulation (THC), AMOC, AtlanticMultidecadal Oscillation (AMO), and NAO, govern the precipitationregime in Southern Greece and the Eastern Mediterranean (e.g.,Rohling et al., 2002; Marino et al., 2009). Solar variability is aplausible mechanism forcing these changes in the North Atlanticand in the Mediterranean (e.g., Bond et al., 2001; Braun et al.,2005; Debret et al., 2007).

There are significant periodicities at 18e22 y in all time sliceswhich can be ascribed to the Hale cycle (e.g., Scafetta, 2010). Theseperiodicities are similar to the cycle of 24 y that has been found forthe North Atlantic Oscillation (Cook et al., 1998). The periodicities at77e90 yrs in all time slices can be attributed to the Gleissberg cyclewhich is an amplitude modulation of the 11 y Schwabe cycle (e.g.,Scafetta, 2010). The Suess or de Vries cycle (w210 yrs) might berepresented by the periodicities at 196e238 yrs in all time slices(e.g., Damon and Sonnett, 1991; Braun et al., 2005). The sets of 29e34 y, 53e67 y and 158e175 y are close to astronomical (solar/planetary) 30 y, 60 y, and 172 y cycles (Scafetta, 2010). The origin ofthe 417 y periodicity in the early Holocene time slice, and the 870 yperiodicity found in the whole data set are also linked to solarvariability (e.g., Damon and Sonnett, 1991; Stuiver and Braziunas,1993). The sets of periodicities centred at 110e118, and 40 ymight also be of solar origin and related to the Schwabe and theGleissberg cycles, respectively. These findings are closely matchedto the periodicities in d14C (Stuiver and Braziunas, 1993).

6. Conclusions

The record from Lake Stymphalia shows that significant varia-tions in palaeoclimate occurred during the Late Glacial to mid-Holocene. The geochemical and sedimentological data lead to afirst understanding of hydrological changes in the catchment,sediment influx from the catchment, and dominant in-lake pro-cesses. The elemental variations are not only signals of local envi-ronmental/climatic changes but reflect regional climate change.Major results are:

1. Facies analysis revealed two types of depositional environ-ment: a shallow littoral with open/oxygenated water condi-tions around 15.7e8.5 ka cal BP and 7.3e5 ka cal BP and a deeplittoral with an occasionally meromictic lake floor between 8.5and 7.3 ka cal BP.

2. Pearson correlation matrices showed that there is a coupling/decoupling of elements over time. Some elements are clustereddue to their sources: Ti, Rb, Zn represent the clay mineralassemblage, while Zr is linked to heavy minerals in coarsergrain size classes. K and Si display an intermediate behaviourdue to different sources. All these elements capture thetorrential river input/catchment precipitation over most of therecord. Mn and Fe clearly reflect lake redox conditions. Ca andSr are mainly linked to in-lake carbonate precipitation.

3. Hydrological conditions in the catchment and the fluctuation ofthe lake level during the Late Glacial and mid-Holocene areconsistent with humidity trends in the Eastern Mediterranean.Ti as a proxy for torrential river input/catchment precipitationis linked to winter insolation, while in-lake carbonate precip-itation is driven by summer evaporation (insolation). Mn/Fereflects the oxic state of lake waters and most likely captureslake level changes.

4. Rb/Sr as a proxy for wet/dry conditions was linked to the seasurface temperature record of core LC21 from the SouthernAegean Sea, to the d18O record of speleothems from Soreq Cave(Israel) reflecting humidity changes, and to solar activity.Accordingly, major climate periods and events such as the


BøllingeAllerød, the Younger Dryas, and the 8.2 cold eventwere identified in the Lake Stymphalia sedimentary sequence.Climate development on the Peloponnese is therefore mainlyinfluenced by variations in the North Atlantic Ocean circulation(e.g., THC, AMOC, AMO, NAO) and corresponding atmosphericcirculation patterns, as well as solar variability.

Acknowledgements

The research was funded by the German research foundation(DFG) through the Graduate School “Human Development inLandscapes” at Kiel University. We kindly thank Kimon Christanis(University of Patras), Mathias Bahns, Marcus Schütz, SophiaDazert, and Jürgen Zahrer (all Kiel University) for their invaluablesupport in the field and in the lab. We thank Görkim Oskay, GiorgosSavalas, Giorgos Floros, and Stavros Vrachliotis (all University ofPatras) who were of great assistance during our field work. Wewould like to thank two anonymous reviewers for their encour-aging comments on the presented paper.

Appendix A. Supplementary data

Supplementary data related to this article can be found at http://dx.doi.org/10.1016/j.quaint.2013.02.014.

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Late Glacial to mid-Holocene palaeoclimate development of Southern Greece inferred from the sediment...

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