Palaeogeography Palaeoclimatology Palaeoecology 220 (2005) 311ndash332

wwwelseviercomlocatepalaeo

Short-term climate changes in the southern Aegean Sea

over the last 48000 years

Maria Geragaa Stella Tsaila-Monopolisb Chrysanthi Ioakimc

George Papatheodoroua George FerentinosaTaLaboratory of Marine Geology and Physical Oceanography Department of Geology University of Patras Patra Greece

bLaboratory of Paleontology Department of Geology University of Patras Patra GreececInstitute of Geology and Mineral Exploration (IGME) 70 Messogion Str Athens Greece

Received 4 June 2003 received in revised form 29 November 2004 accepted 28 January 2005

Abstract

High-resolution palaeoenvironmental changes corresponding to a mean time interval of 450 years covering the last 48000

years were examined in a core from the Cretan Basin in the southern Aegean Sea The intensity and duration of the climatic and

oceanographic events were determined by examining the compositional changes in the planktonic foraminifera and pollen

assemblages along with the y18O signal of Globigerinoides ruber A reconstruction of sea-surface temperatures was attempted

using the Modern Analogue Technique (MAT) In total 10 stadials and 6 interstadials occurred over the last 48000 years These

fluctuations in climatic conditions coincide with fluctuations documented in the western and central Mediterranean and seem to

be associated with DansgaardndashOeschger events Some of these climatic fluctuations are correlated with changes in the

vegetation in the surrounding land

Between 48 and 10 cal kyr BP the most pronounced stadials occurred at 41 cal kyr BP (C69-ST10) and at 13 cal kyr BP

(C69-ST4) These events are characterized by (i) high positive y18O values of Globigerinoides ruber (ii) drops in SST and (iii)

increases in aridity These events may be correlated with the Heinrich H4 event and the Younger Dryas event respectively Two

other stadials at 23 cal kyr BP (C69-ST6) and at 16 cal kyr BP (C69-ST5) which are characterized by increases in the abundance

of the cold plaktonic foraminifera species and increases in aridity may be correlated with the H2 and H1 events respectively

The dominant planktonic foraminiferal species during the stadials witch are correlated with the Heinrich events were

Turborotalita quinqueloba and Globorotalia scitula The most pronounced interstadials occurred between 395 and 385 cal kyr

BP (C69-IST6) and between 25 and 24 cal kyr BP (C69-IST3) and are characterized by depletion in y18O values increases in

SST and increases in humidity The former event coincides with the formation of the sapropelitic layer S2

In the Holocene the most pronounced stadial occurred between 8 and 65 cal kyr BP (C69-ST2) during the interruption of

S1 and is characterized by a reduction in SST and an increase in aridity The most pronounced interstadials of Holocene

occurred during the formation of S1a and S1b between 9 and 8 cal kyr BP (C69-IST1) and between 65 and 55 cal kyr BP

0031-0182$ - s

doi101016jpa

T Correspondi

E-mail addr

ee front matter D 2005 Elsevier BV All rights reserved

laeo200501010

ng author Tel +30 2610997646 fax +30 2610996275

ess gferenupatrasgr (G Ferentinos)

M Geraga et al Palaeogeography Palaeoclimatology Palaeoecology 220 (2005) 311ndash332312

(C69-IST2) respectively These events are characterized by depletion in y18O values increased SST and an increase in humidity

as is indicated by the expansion of temperate evergreen and Mediterranean taxa in the pollen record

D 2005 Elsevier BV All rights reserved

Keywords Late Quaternary Eastern Mediterranean Climatic variability Planktonic foraminifera Pollen Sapropel

1 Introduction

The documentation of climatic variability at millen-

nium scale in the northern Atlantic during the Late

Quaternary referred to as DansgaardndashOeschger cli-

matic cycles (Dansgaard et al 1993 Bond and Lotti

1995 Bond et al 1997) recently led scientists to

investigate the presence of similar events in the

Mediterranean Sea For this reason high-resolution

palaeoclimatic studies have recently been carried out

on marine sediments of the western (Cacho et al 1999

2000 2002) and easternMediterranean Sea (Rohling et

al 1997 De Rijk et al 1999 Geraga et al 2000) and

on terrestrial sediments in the Middle-East (Bar-

Matthews et al 1999 Gvirtzman and Wieder 2001)

The purpose of the present study is to further

extend our knowledge of the climatic variability over

the last 48000 years in the Cretan Basin in the

southern Aegean Sea Furthermore within the frame-

work of this work the microfauna assemblages are

compared with those of the central and the western

Mediterranean Sea (Hayes et al 1999 Sbaffi et al

2001 Perez-Folgado et al 2003) and the formation of

sapropels S1 and S2 is discussed

2 Material and methods

The present paper is based on the sedimentological

micropalaeontological and palynological examination

of a 2 m long core C69 collected from the Cretan

Basin in the southern Aegean Sea (Fig 1) The core

was collected at a water depth of 632 m at Longitude

36832769E and Latitude 24812782NNinety-four samples were used for foram analysis

and 76 samples for pollen analysis The mean

sampling interval for the faunal analyses was 2 cm

Each sample covered approximately a 1 cm thick

interval in the core

For the foraminiferal studies the samples were

disintegrated by hydrogen peroxide and were then

sieved through a 150 Am mesh The dry and weighed

samples were split into separate aliquots

The organic carbon content (Corg) was determined

by the K2Cr2O7ndashFe(NH4)26(H2O) titration method

according to Gaudette et al (1974)

For the palynological analyses the samples were

treated with HCl and HF and ultrasonic sieving (10

Am) Samples were stored and mounted in glycerin In

the diagrams of the total palynomorphs the dino-

flagellate cysts observed in the samples were

excluded The pollen count was between 210 and

930 grains per sample For the construction of the

pollen diagrams selected taxa from the pollen

percentage data were plotted against age together

with the total amount of Arboreal and Non Arboreal

Pollen (AP and NAP) concentration The percentages

of the selected data were based on the total of the

pollen assemblage

A total number of 52 samples along the core were

analyzed for the determination of the oxygen isotopes

on the tests of the planktonic foraminifera Globiger-

inoides ruber (N125 Am) The analyses were carried

out at the SOCFAC Laboratory of Southampton

University and at the Laboratory of Geology and

Geophysics in Edinburgh University

Sea-surface palaeotemperatures in C69 were esti-

mated using the Modern Analogue Technique (MAT

Hutson 1980 Overpeck et al 1985) The MAT

method is based on a database of modern samples

from the north Atlantic and the Mediterranean Sea and

by selecting those whose faunal composition is most

similar to a given fossil sample the sea-surface

palaeotemperature is thus determined The database

used in the present study for the MAT method

comprises the CLIMAP database and the database

of Kallel et al (1997) The former database gives the

sea-surface temperature (SST) for summer (SSTs) and

winter (SSTw) The latter database is based on

samples selected mainly from the Mediterranean Sea

and gives SST on a seasonal basis For the estimation

of the SSTcool (SSTc) in the present study the SSTw

M Geraga et al Palaeogeography Palaeoclimatology Palaeoecology 220 (2005) 311ndash332312

(C69-IST2) respectively These events are characterized by depletion in y18O values increased SST and an increase in humidity

as is indicated by the expansion of temperate evergreen and Mediterranean taxa in the pollen record

D 2005 Elsevier BV All rights reserved

Keywords Late Quaternary Eastern Mediterranean Climatic variability Planktonic foraminifera Pollen Sapropel

1 Introduction

The documentation of climatic variability at millen-

nium scale in the northern Atlantic during the Late

Quaternary referred to as DansgaardndashOeschger cli-

matic cycles (Dansgaard et al 1993 Bond and Lotti

1995 Bond et al 1997) recently led scientists to

investigate the presence of similar events in the

Mediterranean Sea For this reason high-resolution

palaeoclimatic studies have recently been carried out

on marine sediments of the western (Cacho et al 1999

2000 2002) and easternMediterranean Sea (Rohling et

al 1997 De Rijk et al 1999 Geraga et al 2000) and

on terrestrial sediments in the Middle-East (Bar-

Matthews et al 1999 Gvirtzman and Wieder 2001)

The purpose of the present study is to further

extend our knowledge of the climatic variability over

the last 48000 years in the Cretan Basin in the

southern Aegean Sea Furthermore within the frame-

work of this work the microfauna assemblages are

compared with those of the central and the western

Mediterranean Sea (Hayes et al 1999 Sbaffi et al

2001 Perez-Folgado et al 2003) and the formation of

sapropels S1 and S2 is discussed

2 Material and methods

The present paper is based on the sedimentological

micropalaeontological and palynological examination

of a 2 m long core C69 collected from the Cretan

Basin in the southern Aegean Sea (Fig 1) The core

was collected at a water depth of 632 m at Longitude

36832769E and Latitude 24812782NNinety-four samples were used for foram analysis

and 76 samples for pollen analysis The mean

sampling interval for the faunal analyses was 2 cm

Each sample covered approximately a 1 cm thick

interval in the core

For the foraminiferal studies the samples were

disintegrated by hydrogen peroxide and were then

sieved through a 150 Am mesh The dry and weighed

samples were split into separate aliquots

The organic carbon content (Corg) was determined

by the K2Cr2O7ndashFe(NH4)26(H2O) titration method

according to Gaudette et al (1974)

For the palynological analyses the samples were

treated with HCl and HF and ultrasonic sieving (10

Am) Samples were stored and mounted in glycerin In

the diagrams of the total palynomorphs the dino-

flagellate cysts observed in the samples were

excluded The pollen count was between 210 and

930 grains per sample For the construction of the

pollen diagrams selected taxa from the pollen

percentage data were plotted against age together

with the total amount of Arboreal and Non Arboreal

Pollen (AP and NAP) concentration The percentages

of the selected data were based on the total of the

pollen assemblage

A total number of 52 samples along the core were

analyzed for the determination of the oxygen isotopes

on the tests of the planktonic foraminifera Globiger-

inoides ruber (N125 Am) The analyses were carried

out at the SOCFAC Laboratory of Southampton

University and at the Laboratory of Geology and

Geophysics in Edinburgh University

Sea-surface palaeotemperatures in C69 were esti-

mated using the Modern Analogue Technique (MAT

Hutson 1980 Overpeck et al 1985) The MAT

method is based on a database of modern samples

from the north Atlantic and the Mediterranean Sea and

by selecting those whose faunal composition is most

similar to a given fossil sample the sea-surface

palaeotemperature is thus determined The database

used in the present study for the MAT method

comprises the CLIMAP database and the database

of Kallel et al (1997) The former database gives the

sea-surface temperature (SST) for summer (SSTs) and

winter (SSTw) The latter database is based on

samples selected mainly from the Mediterranean Sea

and gives SST on a seasonal basis For the estimation

of the SSTcool (SSTc) in the present study the SSTw

Fig 1 Location map of the study area (CB) in the Aegean Sea showing (a) the present day coastline (thick line) and bathymetry (b) the Last

Glacial Maximum coastline (thin line) according to Van Andel and Lianos (1984) (c) the major rivers and torrents and (d) the location of the

studied core (C69) MB Myrtoon Basin NAT North Aegean Trough SkB Skopelos Basin NSB North Skyros Basin SSB South Skyros

Basin NIB North Ikaria Basin SIB South Ikaria Basin and CB Cretan Basin

M Geraga et al Palaeogeography Palaeoclimatology Palaeoecology 220 (2005) 311ndash332 313

by CLIMAP database and the SST of February by

Kallel were combined For the SSTwarm (SSTw) the

SSTs by CLIMAP and the SST of August by Kallel

were combined

Seven Accelerator Mass Spectrometry (AMS)

datings on specimens of Globigerinoides ruber were

carried out at the laboratories of Beta Analytic (USA)

(Table 1)

3 Data presentation

31 Sediments

Six lithological units have been identified at core

C69 (Fig 2a) on the basis of colour grain size

organic carbon content and sedimentary structures

The first unit A (0ndash23 cm) consists of yellowish

brown structureless mud with a small proportion of

sand Volcanic ash has been observed at about 15 cm

below surface but does not form a discrete tephra

layer This horizon most probably corresponds to the

most recent ash-layer in the Aegean Sea Z2 Santorini

which has a calibrated age of 3570 yr BP (Ramsey et

al 2004)

The second unit B (23ndash44 cm) represents a

sapropel sequence (Kidd et al 1978 Anastasakis

and Stanley 1984) with the Corg content ranging

between 05 and 21 (Figs 2a and 3b) Based on

the AMS dating (Table 1) this sapropel sequence

corresponds to the S1 sapropel which was deposited

in the Aegean Sea and in the eastern Mediterranean

sometime between 6 and 12 14C kyr BP (Cita et al

1977 Rossignol-Strick et al 1982 Fontugne et al

Table 1

AMS dates and dated control points used in core C69

Depth (cm) AMS laboratory

code or source

Uncorrected

AMS 14C

(yr BP)

Calibrated

(yr BP)

150 Z2 Santorini

ash layer

3570a

280 Beta-166995 5810F40 5964ndash6269b

400 Beta-142621 8750F70 8919ndash9458b

600 Beta-190861 14470F70 16164ndash17173b

64 Boundary BZ67 18100c

84 Boundary BZ78a 24200c

930 Beta-168207 29120F270 Turbidited

990 Beta-166996 37900F1200 Turbidited

111 Boundary BZ89 32100c

1520 Beta-133928 36070F300 39855e

1890 Beta-166997 44300F2000 47126e

a Ramsey et al (2004)b Converted into calendar age using the program bcalib 44Q

(Stuiver and Reimer 1993) DR=88F54 (Reimer 2000)c From the study by Sbaffi et al (2001) and Capotondi et al

(1999)d These dates were not used in the construction of the age model

curve in Fig 2e Converted into calendar age with the polynomial provided by

Bard et al (2004)

M Geraga et al Palaeogeography Palaeoclimatology Palaeoecology 220 (2005) 311ndash332314

1994 Aksu et al 1995) Based on the fluctuations of

Corg content (Fig 3) the sapropel sequence can be

divided into three zones a lower and an upper zone

which are characterized by a maximum Corg content

of 21 and 16 respectively and a middle zone

separating the two others with a minimum Corg

content of 11 The lower (40ndash35 cm) and the upper

(30ndash26 cm) zones of high Corg content will hereforth

be referred to as S1a and S1b respectively Previous

studies on the formation of S1 have also described an

interruption in the deposition of the sapropel sedi-

ments (Rossignol-Strick et al 1982 Rohling et al

1997 Geraga et al 2000)

The third unit C (44ndash87 cm) consists of brownish

structureless mud with rare shell fragments The

fourth unit D (87ndash132 cm) is similar to unit C but

is grayish in colour Two layers of structureless silt

appear between 93 and 105 cm The lower boundary

of this interval at 105 cm is sharp and the upper one at

93 cm appears gradational The boundary between the

two layers is indistinct and occurs at approximately 97

cm The two layers correspond to two different

turbidites according to their sedimentological charac-

teristics The lower turbidite layer between 105 and 97

cm consists of material dated at 37900 14C kyr BP

(Table 1) and the upper between 97 and 93 cm

consists of material dated at 29120 14C kyr BP (Table

1) suggesting that the supplying source of each

turbidite was situated at two different locations

The fifth unit E (132ndash153 cm) represents a

sapropelitic sequence (Kidd et al 1978 Anastasakis

and Stanley 1984) Within this sequence the max-

imum Corg content (05ndash154) occurs between 153

and 143 cm This sapropelic layer consists of olive

coloured structureless mud During the interval that

follows between 143 and 132 cm the Corg content

declines from 05 to 03 Based on the AMS

dating (Table 1) the age of this sapropelitic sequence

is 355ndash335 14C kyr BP and seems to correspond to

the S2 sapropel The rare appearance of sapropel S2

often called the bghost sapropelQ in the sediments of

the eastern Mediterranean has led to approximate

estimations of its age (Ryan 1972 Vergnaud-Grazzini

et al 1977)

The sixth unit F (153ndash195 cm) consists of

brownish mud

The sediments of units C D and E contain sand

and silt sized volcanic ash almost everywhere but no

discrete ash layers The highest concentration of the

ash was obtained between 97 and 125 cm

32 Age assessment

The chronological framework of the present study

is based on the five AMS dates (Table 1) The

turbidite layers have not been taken into consideration

in the construction of the age model curve for the

estimation of the sedimentation rate

The first three dates (b24 kyr BP) were converted

into calendar years using the program bcalib 44Q(Stuiver and Reimer 1993 Reimer 2000) while the

other two were converted using the polynomials

provided by Bard et al (2004) (Table 1)

In addition four dated control points were used for

the age assessment (Table 1) The upper dating point

is based on the age (357 cal kyr BP) (Ramsey et al

2004) of the ash layer at 15 cm which is considered to

be the Z2 Santorini ash layer The other three are

based on the biostratigraphic study by Sbaffi et al

(2001) That study has revealed 9 biozones over the

last 34 kyr based on changes in the planktonic

foraminifera and coccolithophores assemblages in the

Fig 2 (a) Lithology of core C69 Ages displayed to the left of the core are AMS 14Cnc dates (b) Age model curve for the estimation of the mean

sedimentation rate The diagram is based on five calibrated AMS 14C ages (arrows) and four dating points (in cal yr BP) based on (i) the

Santorini Z2 ash layer (Ramsey et al 2004) (square) and (ii) the estimated age for upper and lower boundaries of biozone 7 and upper boundary

of biozone 9 by Sbaffi et al (2001) (circles) The turbidite layers have not been taken into consideration in the construction of the age model

curve for the estimation of the sedimentation rate Thus the older dating points (at 47126 cal kyr BP 39855 cal kyr BP and 32100 cal kyr BP)

appear in shallower depths in the age model curve than in the core

M Geraga et al Palaeogeography Palaeoclimatology Palaeoecology 220 (2005) 311ndash332 315

central Mediterranean dated in calendar years BP

These biozones are comparable with the ecozones

proposed by Capotondi et al (1999) and are detect-

able throughout the central Mediterranean and as far

as the southern Adriatic Sea (Giunta et al 2003

Principato et al 2003) In our study the lower and the

upper boundaries (in calendar years BP) of the

biozone 7 and the upper boundary of biozone 9 were

used The former which corresponds to the ecozone 9

includes the Last Glacial Maximum interval and is

well identified in our records by the planktonic

assemblages and the isotopic signal The isotopic

Fig 3 Downcore variation of (a) y18O values (x) and (b) Corg content () versus age in cal kyr BP

M Geraga et al Palaeogeography Palaeoclimatology Palaeoecology 220 (2005) 311ndash332316

record for this interval is also consistent with the

isotopic record in the study of Siani et al (2001) in the

southern Adriatic Sea suggesting a realistic age

control Biozone 9 represents a warm interval

corresponding to interstadial 5 (Cacho et al 1999)

In our data biozone 9 is well identified by the

planktonic assemblages and the depletions of the

isotope values

Based on the above age model curve the mean

sedimentation rate in core C69 is 38 cmkyr (Fig 2)

The mean time resolution of planktonic and MAT

records is 450 years while that of oxygen isotopes

and pollen is 850 yr and 550 yr respectively

33 Oxygen isotopes

The downcore variation of the y18O values in core

C69 seen in Fig 3 reveals that in the isotopic stage

ST3 (48ndash24 cal kyr BP) the y18O data exhibits

relatively lower values between 40 and 38 cal kyr BP

(~00x) and around 34 cal kyr BP (06x) The

former corresponds to the deposition of the S2

sapropel and the latter corresponds to the Interstadial

5 (Ist5) which has been also identified in cores from

the central and western Mediterranean (Cacho et al

1999 Sbaffi et al 2001 Perez-Folgado et al 2003)

The small decrease in y18O values (19x) around 24

cal kyr BP may correspond to the isotopic event 31

(Martinson et al 1987) High y18O values occur at

time intervals from 415 to 405 cal kyr BP (18ndash

19x) 355ndash345 cal kyr BP (15ndash13x) and 29ndash27

cal kyr BP (27x) The first and the third time

intervals are around the ages of the Heinrich 4 (39 cal

kyr BP) and Heinrich 3 (30 cal kyr BP) events

respectively (Bond et al 1992)

In the isotopic stage ST2 (24ndash11 cal kyr BP) the

strongest enrichment of y18O values (28ndash25x) occur

between 215 and 195 cal kyr BP suggesting the Last

M Geraga et al Palaeogeography Palaeoclimatology Palaeoecology 220 (2005) 311ndash332 317

Glacial Maximum High positive values ranging from

3x to 48x have been observed for the same interval

in the eastern Mediterranean (Vergnaud-Grazzini et

al 1977 1986 Thunell and Williams 1989)

Towards the end of the ST2 the gradual depletion of

the y18O values from 24x to 12x indicates the

onset of deglaciation during the Late Glacial period

(Vergnaud-Grazzini et al 1986 Thunell and Wil-

liams 1989) The rapid and temporal enrichment of

y18O at 13 cal kyr BP (26x) may correspond to the

Younger Dryas event which has also been identified

in cores from the central Mediterranean (Vergnaud-

Grazzini et al 1977 1986)

During the Holocene (ST1) the most depleted

values of y18O occur during the sapropel sequence S1

(12x) High negative values of y18O ranging

between 00x and 20x are documented in all

palaeoceanographic records of the eastern Mediterra-

nean indicating the presence of warm climate

accompanied by the establishment of a low salinity

surface layer during that interval (Cita et al 1977

Williams et al 1978 Aksu et al 1995) The

depletion of y18O between the full glacial and the

Holocene conditions is estimated at around 43x in

the eastern Mediterranean Sea (Thunell and Williams

1989) Before the deposition of S1 a short and rapid

shift to higher value of y18O (10x) occurs at 10 cal

kyr BP and probably corresponds to the first Holocene

stadial (Bond et al 1997) Just after the deposition of

S1 the y18O values appear to increase to 0x

34 Planktonic foraminifera biostratigraphy

Planktonic foraminifera are abundant throughout

the core and the downcore variations of their

abundance are shown in Figs 4 and 5

341 Globigerinoides ruber (white and pink

varieties)

This species which is considered as indicative of

warm and oligotrophic surface waters (Thunell 1978

Pujol and Vergnaud Grazzini 1995) is present

throughout the core covering between 2 and 41

of the total planktonic fauna (Fig 4A)

The Globigerinoides ruber abundance between 48

and 42 cal kyr BP ranges between 21 and 28 Its

abundance between 42 and 14 cal kyr BP is low less

than 15 Towards the end of the Glacial period

between 14 and 10 cal kyr BP G ruber increases

gradually from 10 to 20 A sharp decrease of G

ruber at ~12 cal kyr BP (8) (Fig 4A) is just after the

enrichment of y18O at 13 cal kyr BP and may

therefore be attributed to the Younger Dryas event

A similar decrease in the abundance of G ruber

between 135 and 125 cal kyr BP has been recorded

in core C40 in the vicinity of the study area in the

Myrtoon Basin (Geraga et al 2000)

During the Holocene the presence of Globiger-

inoides ruber is dominant (N20) and appears in

maximum percentages between 95 and 8 cal kyr BP

(35ndash42) between 65 and 6 cal kyr BP (26ndash36)

and between 4 and 25 cal kyr BP (27ndash33) The

former two intervals almost coincide with the for-

mation of the two sapropelic layers S1a and S1b

respectively Increase of G ruber during the deposi-

tion of S1 have been observed throughout all of the

eastern Mediterranean (Casford et al 2002 Princi-

pato et al 2003) Temporal decreases in the abun-

dance of G ruber occur at 10 cal kyr BP 8ndash65 cal

kyr BP and 55 cal kyr BP The first coincides with

enrichment of values of y18O and is related to the first

Holocene stadial The other two coincide with the

interruption and the end of S1 respectively During

the Holocene a decrease in the abundance of G ruber

have also been observed in core C40 in the Myrtoon

Basin at 95 cal kyr BP 8ndash75 cal kyr BP and 7 cal

kyr BP

The high abundance of Globigerinoides ruber

during the late Glacial and Holocene periods has

been observed all throughout the Mediterranean Sea

(Buckley et al 1982 Hayes et al 1999)

342 Minor warm planktonic indicators

Other planktonic species recognized in the core

and indicative of warm surface waters are Globiger-

inoides sacculifer Globigerinoides tenellus Globi-

gerinoides trilobus Globigerinoides obliquus

Orbulina universa and Globigerinella aequilateralis

Their presence in the planktonic assemblages are

generally low (b10) and discontinuous (Fig 5) G

sacculifer is present only in the last 10 kyr and

exhibits the highest percentages (~8) between 7 and

6 cal kyr BP which almost coincides with the

formation of the sapropelic layer S1b This also

occurred in core C40 selected from the Myrtoon

Basin (Geraga et al 2000) An increase in abundance

Fig 4 Downcore variation of selected planktonic species versus age in calibrated kyr BP On the right side of each diagram are shown the intervals where the species abundance peaks

in cores from the western Mediterranean Sea according to Perez-Folgado et al 2003 (Ro to Ra2 high abundance of Globigerinoides ruber alba R1a to R1c high abundance of

Globigerinoides ruber pink Q1 to Q6 high abundance of Turborotalita quinqueloba B1 to B4 high abundance of Globigerina bulloides I0 to I5 high abundance of Globorotalia

inflata P1 to P5 high abundance of Neogloboquadrina pachyderma (d) Pm3 decrease of N pachyderma (d) SPDF Small Foraminifera Dominance Zone recorded in cores from

the western and the central Mediterranean) (Pujol and Vergnaud Grazzini 1995 Perez-Folgado et al 2003) BZ The boundaries of the planktonic biozones in the central

Mediterranean (Sbaffi et al 2001)

MGera

gaet

alPalaeogeographyPalaeoclim

atologyPalaeoeco

logy220(2005)311ndash332

318

Fig 5 Downcore variation of selected planktonic species against age in calibrated kyr BP (left axis) and radiocarbon kyr BP (right axis) BZ

The boundaries of the planktonic biozones in the central Mediterranean (Sbaffi et al 2001) Stippled bands show the zones in the sapropel

sequence with TOC contentN13

M Geraga et al Palaeogeography Palaeoclimatology Palaeoecology 220 (2005) 311ndash332 319

of G sacculifer at the top-most of S1 has been

observed in cores from the eastern Mediterranean and

has been related to the occurrence of a surface

pycnocline during that period (Principato et al

2003)

Globigerinoides trilobus is absent in the planktonic

assemblages between 47 and 18 cal kyr BP except for

two intervals between 48 and 44 cal kyr BP and

between 38 and 36 cal kyr BP where its percentage is

always b5 This species is present during the last 18

kyr but in very low percentages and shows a

maximum (4) between 75 and 55 cal kyr BP

around the formation of the S1b layer

Orbulina universa occurs only between 48 and 44

cal kyr BP between 40 and 34 cal kyr BP between 28

and 24 cal kyr BP and during the last 11 kyr Its

presence is generally low and exhibits the highest

percentages between 10 and 6 cal kyr BP (5ndash10)

Globigerinella aequilateralis is present in the core

only during the last 11 kyr but its percentages are

always lower than 5

The increases in all the aforementioned species

during the Holocene coincide with the decrease in the

y18O values suggesting a general increase in the sea

surface temperature The appearance of the above-

mentioned warm species between 16 and 11 14C kyr

BP and the following increase in abundance have

been observed in cores across the Mediterranean

(Buckley and Johnson 1988 Jorissen et al 1993

Hayes et al 1999)

343 Globigerina bulloides

This species is indicative of sub-polar water masses

highly dependent on enhanced food levels (upwelling

strong seasonal mixing or freshwater inputs (Lourens

et al 1994) Its presence is significant throughout the

core by a mean percentage of 11 (Fig 4C)

Globigerina bulloides occurs in highest abundance

between 48 and 43 cal kyr BP (10ndash23) between 35

and 32 cal kyr BP (10ndash21) between 26 and 18 cal

kyr BP (6ndash15) between 16 and 13 (5) and

between 9 and 55 cal kyr BP (7ndash30) during the

M Geraga et al Palaeogeography Palaeoclimatology Palaeoecology 220 (2005) 311ndash332320

formation of the sapropel sequence of S1 During the

interruption of S1 G bulloides appears slightly

decreased

An increase in the abundance of Globigerina

bulloides during the formation of sapropel S1 has

also been observed in most of the cores in the

eastern Mediterranean (Aksu et al 1995 Rohling

et al 1997 Geraga et al 2000) This increase has

been attributed to lower oxygen content within the

photic zone since this species can survive at the

end of phyto- and zooplankton blooms when

oxygen had been rapidly consumed (Principato et

al 2003)

344 Globigerinita glutinata

This cosmopolitan species has a mean participa-

tion in the planktonic assemblages of about 9 (Fig

5) The concentration is high during the Glacial

period between 43 and 40 cal kyr BP (6ndash18)

Globigerinita glutinata appears to increase gradually

from 9 to 37 between 28 and 95 cal kyr BP

with two declines at 19 cal kyr BP (3) and 16 cal

kyr BP (9) The maximum percentage of G

glutinata (23ndash37) occurs between 125 and 95

cal kyr BP during the transition from the Last

Glacial period to Holocene G glutinata is almost

absent during the formation of the two sapropelic

layers S1a and S1b This trend has also been

observed in the sediments of cores throughout the

Aegean Sea (Casford et al 2002)

345 Globorotalia truncatulinoides

The abundance of this species in the Mediterranean

seems to be controlled mainly by the winter con-

vection and vertical mixing (Pujol and Vergnaud

Grazzini 1995) In C69 it is mainly absent except

between 40 and 34 cal kyr BP and between 18 and 9

cal kyr BP when it never exceeds 4 in the planktonic

assemblages (Fig 5)

346 Globorotalia inflata

This species in the Mediterranean is associated

with cool and deep mixed waters (Thunell 1978

Pujol and Vergnaud Grazzini 1995) In C69 (Fig 4D)

it participates with a low mean percentage (3) in the

planktonic fauna Globorotalia inflata appears to

increase slightly between 43 and 40 cal kyr BP (2ndash

8) between 36 and 33 cal kyr BP (5ndash12) between

26 and 23 cal kyr BP (2ndash5) and between 155 and

12 cal kyr BP (2ndash3)

During the Holocene it appears in low percen-

tages except for the interruption of S1 at 8 cal kyr

BP and immediately after the end of S1 at 5 cal kyr

BP when its percentages are 1ndash4 and 5ndash13

respectively The rapid and temporal increase of

Globorotalia inflata after the end of the sapropel S1

is documented in almost all the cores from the

eastern Mediterranean and is attributed to deep water

ventilation (De Rijk et al 1999 Geraga et al 2000

Casford et al 2002)

347 Globorotalia scitula

This species which is considered as indicative of

cool-subpolar waters (Thunell 1978 Lourens et al

1994) is absent in the last 10 kyr throughout the

Holocene and appears only during the Glacial period

(Fig 4F) Its participation in the planktonic assemb-

lages never exceeds 8 in the total fauna The

highest abundances of Globorotalia scitula are

recorded between 42 and 38 cal kyr BP (4ndash8) and

between 255 and 22 cal kyr BP (1ndash5)

348 Turborotalita quinqueloba

This species is considered as indicative of cool

waters (Thunell 1978 Lourens et al 1994) but is

also tolerant to fairly low salinity andor enhanced

fertility in surficial waters (Rohling et al 1997) In

C69 (Fig 4B) Turborotalita quinqueloba constitutes

a significant species and its mean percentage is 18

in the total fauna T quinqueloba from 46 to 42 cal

kyr BP and from 38 to 34 cal kyr BP appears in

relatively low percentages (5ndash12) A high abun-

dance of T quinqueloba occurs between 42 and 40

cal kyr BP (22ndash35) and from 32 to 26 cal kyr BP

(30ndash65) and coincides with an enrichment of y18Oin the same intervals (Fig 2) Between 26 and 10 cal

kyr BP T quinqueloba exhibits a gradual decline

from about 65 to 10 However during this

interval abrupt increases in T quinqueloba occur at

23 cal kyr BP (47) 195 cal kyr BP (35) 175ndash

165 cal kyr BP (25) and 13 cal kyr BP (18)

During these intervals the y18O data exhibits high

positive values During the last 11 kyr the abundance

of T quinqueloba ranges between 5 and 10

except for a spike (15) at 65 cal kyr BP during the

interruption of S1

M Geraga et al Palaeogeography Palaeoclimatology Palaeoecology 220 (2005) 311ndash332 321

349 Neogloboquadrina dutertrei Neogloboqua-

drina pachyderma

Neogloboquadrinid species are indicative of cool

waters and also of the eutrophicated waters associated

with the formation of a Deep Chlorophyll Maximum

(DCM) layer (Fairbanks and Wiebe 1980) Among

these species Neogloboquadrina pachyderma (s)

thrives in colder waters (Pujol and Vergnaud Grazzini

1995) In C69 N pachyderma (s) is almost absent as

only rare specimens occur during the glacial period

The presence of Neogloboquadrina dutertrei (Fig 5)

ranges between 0 and 21 that of N pachyderma

(d) (Fig 4E) between 0 and 37 and these two

species present similar trends in their downcore

variations The highest percentages of both species

though with abrupt fluctuations occur between 40 and

32 cal kyr BP and between 22 and 12 cal kyr BP

Spikes of Neogloboquadrina pachyderma occur at

40ndash33 cal kyr BP (20ndash37) (which includes the

deposition of S2) 29 cal kyr BP (14) 20ndash19 cal kyr

BP (23ndash25) and 17ndash13 cal kyr BP (28ndash22)

During the Holocene N pachyderma appears in

low percentages (b4) or is absent Slight increases

occur around 8 cal kyr BP during the interruption of

S1 (2ndash5) and around 6ndash5 cal kyr BP immediately

after the end of S1 (6ndash9)

Similar trends in the downcore variation of Neo-

globoquadrina pachyderma (d) for the Late Glacial

period and Holocene have been observed all through-

out the eastern Mediterranean (Casford et al 2002

Principato et al 2003)

35 Pollen

Pollen and spores are well preserved between 42

and 35 cal kyr BP and for the last 25 kyr and the

downcore variations of selected taxa presented in Fig

6 correspond to these intervals

The pollen spectrum ranges from semi-desert and

steppe to deciduous and coniferous forests In general

the pollen stratigraphy of the C69 core shows

fluctuations from open vegetation communities to

forest in response to glacialndashinterglacial climatic

conditions The forested periods are characterized by

the significant presence of Quercus ilexcoccifera

type followed by Corylus Carpinus Ulmus and

sometimes Fagus The steppic environment is char-

acterized by the significant presence of Gramineae

Chenopodiaceae Compositae and Artemisia The

main change in the pollen records occurs at 11 cal

kyr BP where the Mediterranean taxa appear and

afterwards remain constant suggesting the ameliora-

tion of the climate during the Holocene

For the intervals 42 to 35 cal kyr BP and 25 to 10

cal kyr BP coniferous and cool-temperate deciduous

trees were continuously present accounting for 25ndash

55 and 25ndash70 of the total palynomorphs assemb-

lages respectively (Figs 6 and 7E) The almost

continuous presence of cool-temperate trees in these

intervals is evident in all pollen records in marine ant

terrestrial sediments of Greece and the surrounding

seas and indicates relatively mild wet climatic

conditions (Tzedakis et al 2002)

Variations in APNAP values also occur in the

abovementioned intervals (Fig 7E) Between 42 and

35 cal kyr BP the NAP values exhibit three peaks at

41ndash40 cal kyr BP 375 cal kyr BP and 35 cal kyr BP

(Fig 7E) During these peaks Gramineae and Com-

positae appear together with Chenopodiaceae Arte-

misia and Polygonaceae (Figs 6 and 7EF)

suggesting the prevalence of low temperature and

low annual precipitation (Tarasov et al 1998 Peyron

et al 1998) However the co-existence of the boreal

taxa Alnus Betula and the cool-temperate elements

Fagus Corylus and Cedrus (Fig 6) indicates

sufficient precipitation and temperatures not below

that of a tundra in the uplands (Walter 1974

Rossignol-Strick et al 1992) The first of these

intervals coincides with the strong enrichment of

y18O values which is related to the period of H4

event Increased y18O values also occur at the time of

the third interval

The increase of AP values at 40 cal kyr BP and

between 37 and 36 cal kyr BP which account for 70

of the total palynomorphs with the concurrent decline

of cool steppic and semi-desertic taxa and the increase

in the warm- and cool-temperate taxa (Fig 6) suggests

an increase in humidity The peak at 40 cal kyr BP

occurs just before the deposition of S2 (39ndash385 cal

kyr BP) and coincides with a depletion of y18O values

Between 25 and 11 cal kyr BP Gramineae

Chenopodiaceae Compositae and Artemisia domi-

nate indicating the presence of a steppic environment

(Fig 6) The former exhibits constant percentage

abundance while the latter three exhibit variable

percentage abundance

Fig 6 Pollen diagrams of selected taxa The percentage occurrence values of each taxa are plotted against a calibrated radiocarbon time scale Cool-temperate summergreen taxa

include Carpinus Corylus Fagus Tilia and Ulmus Warm-temperate summergreen taxa include Platanus Ostrya and Fraxinus Mediterranean taxa include Olea Pistacia and

Phyllirea Other woody taxa include Acer Juglans and Salix Other herbaceous taxa include Ranunculus Rosaceae and Rumex Stippled bands show the zones in the sapropel

sequence with TOC content N13

MGera

gaet

alPalaeogeographyPalaeoclim

atologyPalaeoeco

logy220(2005)311ndash332

322

Fig 7 Diagrams showing the downcore variation of (A) the dissimilarity coefficient (B) the SSTc (SST cold) and SSTw (SSTwarm) as estimated by the application of MAT method

(C) the y18O values (PDB x) of Globigerinoides ruber (D) the cold planktonic fauna abundance (Turborotalita quinqueloba Globorotalia inflata Globorotalia scitula

Neogloboquadrina pachyderma (d)) (E) the pollen percentage occurrence AP Alboreal pollen (I and II) NAP non-alboreal pollen (III and IV) The pollen sums show (I) the

Mediterranean taxa (Olea Pistacia and Phyllirea) and Quercus coccifera (II) the rest of arboreal pollen assemblage (III) the semi-desertic taxa (Chenopodiaceae Artemisia and

Ephedra) and (IV) the rest of non-arboreal pollen assemblage (F) The stadials and interstadials identified in C69 and their correlations to the stadials and interstadials identified in the

western Mediterranean (Perez-Folgado et al 2003) and the North Atlantic area (Bond et al 1992)

MGera

gaet

alPalaeogeographyPalaeoclim

atologyPalaeoeco

logy220(2005)311ndash332

323

Fig 7 Diagrams showing the downcore variation of (A) the dissimilarity coefficient (B) the SSTc (SST cold) and SSTw (SSTwarm) as estimated by the application of MAT method

(C) the y18O values (PDB x) of Globigerinoides ruber (D) the cold planktonic fauna abundance (Turborotalita quinqueloba Globorotalia inflata Globorotalia scitula

Neogloboquadrina pachyderma (d)) (E) the pollen percentage occurrence AP Alboreal pollen (I and II) NAP non-alboreal pollen (III and IV) The pollen sums show (I) the

Mediterranean taxa (Olea Pistacia and Phyllirea) and Quercus coccifera (II) the rest of arboreal pollen assemblage (III) the semi-desertic taxa (Chenopodiaceae Artemisia and

Ephedra) and (IV) the rest of non-arboreal pollen assemblage (F) The stadials and interstadials identified in C69 and their correlations to the stadials and interstadials identified in the

western Mediterranean (Perez-Folgado et al 2003) and the North Atlantic area (Bond et al 1992)

MGera

gaet

alPalaeogeographyPalaeoclim

atologyPalaeoeco

logy220(2005)311ndash332

323

M Geraga et al Palaeogeography Palaeoclimatology Palaeoecology 220 (2005) 311ndash332324

Between 25 and 24 cal kyr BP the presence of

Mediterranean taxa accompanied by temperate decid-

uous taxa and Abies Cedrus Quercus coccifera and

Pinus suggests a brief climatic amelioration with

increased moisture at least in summer Soon after at

24 cal kyr BP the decline of these taxa and the

increase of Artemisia and Ephedra suggest a climatic

deterioration The above change in pollen assemb-

lages has also been recorded in Ioannina Lake (NW

Greece Galanidou et al 2000) where an amelioration

in the climate at around 25 kyr followed by a short

period of climatic deterioration around 24ndash22 kyr

(H2 event) was observed Furthermore similar

changes for the same time interval have been recorded

in central Greece (Bottema 1974 Tarasov et al

1998 Digerfeldt et al 2000 Karkanas 2001)

At 16 cal kyr BP Gramineae exhibit a slight

decline while Artemisia and Chenopodiaceae

increase suggesting a brief expansion of the semi-

desert This climatic deterioration coincides with the

age of H1 event (~16 cal kyr BP) (Bond et al 1992)

At 13 cal kyr BP the high abundance of Chenopo-

diaceae coincides with the strong enrichment of y18Ovalues (Fig 3) and suggests an increase in aridity

during the Younger Dryas event Expansions of

Chenopodiaceae at the time of the Younger Dryas

event have been documented in all the pollen records

in the eastern Mediterranean region (Rossignol-Strick

1995)

At around 11 cal kyr BP the appearance of Quercus

coccifera and other Mediterranean taxa (Pistacia

Olea and Phyllirea) and soon after at 10 cal kyr BP

the appearance of the temperate deciduous forests

mark the onset of the Holocene The above taxa along

with Quercus Corylus Ulmus Tilia Fagus indicate

a significant available moisture increase with no

drought in summer in the Mediterranean region

Similar trends have been observed by Bottema

(1974) and Rossignol-Strick (1995) in almost all the

pollen records of the eastern Mediterranean region

The populations of the deciduous and Mediterra-

nean taxa decline between 8 and 7 cal kyr BP during

the sapropel interruption between S1a and S1b at

around 8 cal kyr BP whereas an increase of Artemisia

accompanied by the presence of Hedera indicate an

increase in aridity This climatic change is in phase

with the 82 cal kyr BP global event first observed in

Greenland ice cores (Alley et al 1997) Here the

climatic optimum began in the early Holocene at 105

cal kyr BP and ended at 3 cal kyr BP This climatic

optimum resulted in the great expansion of the

temperate deciduous and Mediterranean forests

36 Application of MAT

The downcore variation of SSTc and SSTw based

on the application of the MAT is presented in Fig 7B

According to Overpeck et al (1985) and Kallel et

al (1997) estimations of SSTs by MAT are consid-

ered reliable when the dissimilarity coefficients

(bdistanceQ) is lower than 025 If it is higher than

030 it indicates that the fossil samples in this

interval have no close modern analogue samples

The dissimilarity coefficient (Euclidean) in our data

(Fig 7A) is higher than 025 between 17 and 32 cal

kyr BP indicating no reliable SSTs estimations for

this interval High dissimilarity coefficient around

this time interval has also been recorded in previous

studies in the Mediterranean Sea (Sbaffi et al 2001)

In the present data the downcore variation of the

dissimilarity coefficient seems to be linked to

variations in the abundance of Turborotalita quin-

queloba The correlation coefficient of T quinque-

loba abundance and dissimilarity coefficient is 083

along the core and increases to 093 in the interval

105ndash30 cal kyr BP

At present the SST in the southern Aegean ranges

in winter between 149 and 181 8C and in summer

between 212 and 254 8C (Levitus and Boyer 1994)

The SSTs estimated for the core-top studied sample

(selected at a depth of 5 cm below the surface) are for

winter (SSTc) 193 8C and for summer (SSTw) 228

8C This shows that core-top SSTw is within the

present day range but core-top SSTc is higher by ~15

8C in relation to the present SSTc

During the Holocene the SST is continuously high

with short intervals of rapid fluctuations The mean

SSTc is 195 8C and the mean SSTw is 249 8C Themean difference in temperature between winter and

summer (seasonality) appears slightly decreased (54

8C) in relation to present day (Levitus and Boyer

1994)

During the Holocene from 8 to 7 cal kyr BP and

from 55 to 5 cal kyr BP the SST decreases The mean

annual SST at these intervals compared to the mean

annual SST value for the Holocene (222 8C) is about

M Geraga et al Palaeogeography Palaeoclimatology Palaeoecology 220 (2005) 311ndash332 325

25 8C lower SST appears increased at 95ndash8 cal kyr

BP and 65ndash55 cal kyr BP The mean annual SST

during these intervals compared to the mean annual

SST value for the Holocene (222 8C) is about 4 8Chigher A minor decrease of SSTc of about 1 8C is

observed at 10 cal kyr BP

Between 17 and 105 cal kyr BP the estimated

SSTc and SSTw are lower compared to the Holocene

The mean SSTc is 117 8C and the mean SSTw is 152

8C The mean difference of SSTc between the

abovementioned interval and the Holocene is 78 8Cand that of SSTw is slightly higher (97 8C) Thisreveals a weaker seasonality (358C) between 17 and

10 cal kyr BP than during the Holocene (54 8C)Although absolute values differ Perez-Folgado et al

(2003) have also recorded a decrease in the seasonal

gradient (due to high drops of SSTw) in the Glacial

Period (5 8C) in relation to the Holocene (10 8C) inthe western Mediterranean Sea

Between 47 and 32 cal kyr BP the SST appears

significantly higher compared to the previous interval

(ie 17 to 135 cal kyr BP) The mean SSTc is 135 8Cand the mean SSTw is 194 8C The seasonal gradientis more pronounced in the early part of the interval

between 47 and 42 cal kyr BP (76 8C) than in the latepart (55 8C)

Between 47 and 32 cal kyr BP the SST fluctuates

rapidly for short intervals Reduction of SST occurs

between 41 and 40 cal kyr BP and at 35 cal kyr BP

The mean annual SST drops during these intervals

compared to the mean annual SST for this period

(165 8C) is 1 8C An increase in SST occurs at around

42 cal kyr BP 39ndash38 cal kyr BP and 35ndash34 cal kyr

BP The mean annual SST rises during these intervals

compared to the mean annual SST for this period

(165 8C) is 1 8C

4 Discussion

41 Stadial and interstadials

The present study of the downcore variation of (i)

SST (ii) the abundance of cold planktonic foramin-

ifera (iii) the y18O values and (iv) the pollen record

reveals a series of short-term palaeoclimatic changes

during the last 48 kyr (Fig 7) In total 10 stadials and

6 interstadials have been identified hereafter referred

to as C69-ST (1ndash10) and C69-IST (1ndash6) respectively

(Fig 7F) One stadial (C69-ST10) and four intersta-

dials (C69-IST1 C69-IST2 C69-IST3 and C69-IST6)

are evident in all four diagrams Two stadials (C69-

ST4 and C69-ST2) are evident in three diagrams Four

stadials (C69-ST5 C69-ST6 C69-ST7 and C69-ST8)

are evident in two diagrams Three stadials (C69-ST1

C69-ST3 and C69-ST9) and two interstadials (C69-

IST4 and C69-IST5) are evident in one diagram The

events that are evident in the three or four downcore

variation diagrams are considered as most pronounced

events The events that are evident in one or two

downcore variation diagrams are considered as least

pronounced events

All these climatic events are comparable with

similar events recognized in the North Atlantic

(Dansgaard et al 1993 Bond et al 1997) and the

western Mediterranean Sea (Cacho et al 1999 Perez-

Folgado et al 2003) (Fig 7G) The difference in age

of the events occurrence between the present study

and in the abovementioned studies is in the range of a

few hundreds to one millennium of years and may be

attributed to (i) the lack of direct dating of the events

in the present data (ii) microscale changes in the

sedimentation rate in core C69 between the dating

points or (iii) the calibration method of the 14C age

Between 48 and 11 cal yr BP seven stadials (C69-

ST10-4) have been observed (Fig 7F) The C69-ST10

(415ndash40 cal kyr BP) shows a drop in SST and an

increase in y18O values and in semi-desertic vegeta-

tion (Fig 7) This event can be correlated with events

of St11 (~41 cal kyr BP) or St9H4 (40ndash385 cal kyr

BP) (Fig 7G) (Dansgaard et al 1993 Cacho et al

1999 Perez-Folgado et al 2003) However the

intensity and the duration of C69-ST10 event encour-

age us to suggest that this event is most probably

correlative with the H4 The C69-ST9 (38ndash37 cal kyr

BP) is characterized only by an increase in aridity

since the y18O values although exhibiting an increas-

ing trend are still low and the SST remains

moderately high This event may be correlated with

the St8 (365ndash355 cal kyr BP) (Dansgaard et al

1993 Cacho et al 1999 Perez-Folgado et al 2003)

The C69-ST8 (35ndash345 cal kyr BP) is characterized by

a rapid decline in SST and enrichment in y18O values

(Fig 7) This event occurs at times equivalent to St7

(~345 cal kyr BP) (Dansgaard et al 1993 Cacho et

al 1999 Perez-Folgado et al 2003)

M Geraga et al Palaeogeography Palaeoclimatology Palaeoecology 220 (2005) 311ndash332326

An increase in cold fauna accompanied by enrich-

ment in y18O values characterize the C69-ST7 (29ndash27

cal kyr BP) (Fig 7) This event occurs at the same

time with St4 (29ndash28 cal kyr BP) and appears 2000 yr

later than H3 (31ndash295 cal kyr BP) (Dansgaard et al

1993 Cacho et al 1999 Perez-Folgado et al 2003)

However its intensity as identified by the very low

y18O values and the extremely high abundance of cold

species encourage us to suggest that may corresponds

to H3

The C69-ST6 (24ndash22 cal kyr BP) shows an

increase in cold planktonic fauna and aridity (Fig

7) The y18O values although exhibiting a decreasing

trend are still high (Fig 7C) This event can be

correlated to the H2 (24 cal kyr BP) identified in the

North Atlantic and western Mediterranean Sea (Dans-

gaard et al 1993 Cacho et al 1999 Perez-Folgado

et al 2003) Between 205 and 19 cal kyr BP the

increase of cold fauna accompanied with an enrich-

ment of y18O values and an increase in aridity suggest

the prevalence of Last Glacial Maximum event The

C69-ST5 (165ndash155 cal kyr BP) is characterized by

an increase in cold planktonic fauna at 155 cal kyr BP

and just after and at 165 cal kyr BP an increase in

aridity (Fig 7) The y18O values although exhibiting

a decreasing trend are still high (Fig 7C) This event

can be correlated to the H1 event (16 cal kyr BP)

identified in the North Atlantic and western Medi-

terranean Sea (Dansgaard et al 1993 Cacho et al

1999 Perez-Folgado et al 2003) The C69-ST4

(135ndash125 cal kyr BP) shows low SST increased

y18O values and an increase in semi-desertic vegeta-

tion (Fig 7) This event corresponds to Younger

Dryas event which has also been observed in the

western Mediterranean Sea (Cacho et al 1999 Perez-

Folgado et al 2003) Climatic deterioration during

the Younger Dryas with a decrease in temperature

and an increase in aridity has been documented all

over the eastern Mediterranean in the marine and

terrestrial records (Rossignol-Strick 1995)

The intervals between the abovementioned stadials

are characterized by milder climatic conditions

However within four of them the signal is enhanced

(C69-IST3ndash6) The C69-IST6 (395ndash385 cal kyr BP)

shows a strong depletion in y18O values increased

SST a decline in semi-desertic taxa and an increase of

temperate trees This event coincides with the

formation of S2 If we assume that the C69-ST10

correlates with the H4 event then the C69-IST6 may

be correlated with the Ist8 (~38ndash37 cal kyr BP)

identified in the North Atlantic and western Medi-

terranean Sea (Dansgaard et al 1993 Cacho et al

1999 Perez-Folgado et al 2003) The C69-IST5 (37ndash

35 cal kyr BP) shows an increase of temperate taxa in

the pollen record The SST is moderate and increases

rapidly at the end of the event but the y18O values are

high The C69-IST4 (34ndash33 cal kyr BP) shows only a

depletion in the y18O values The appearance of

Mediterranean and temperate tree taxa characterizes

the C69-IST3 (25ndash24 cal kyr BP) During this event

the y18O values exhibit a decreasing trend and the

abundance of cold fauna also decreases This event

can be correlated with the Ist3 (Dansgaard et al 1993

Cacho et al 1999 Perez-Folgado et al 2003)

The microfauna associations identified in the

present data during the Heinrich events differ from

those recorded in the western Mediterranean at the

same intervals (Fig 4) (Perez-Folgado et al 2003)

The planktonic assemblages during the H1ndashH4 in the

western Mediterranean display sharp increases of

Neogloboquadrina pachyderma (s) Turborotalita

quinqueloba Globorotalia scitula and Globigerina

bulloides while Globorotalia inflata Globigerinoides

ruber and N pachyderma (d) tend to decline or

disappear (Perez-Folgado et al 2003) In the Cretan

Basin T quinqueloba and G scitula dominate the

microfauna during the H1ndashH4 but without forming

peaks as strong as those present in the western

Mediterranean data The participation of N pachy-

derma (d) and G inflata in the microfauna assemb-

lages is high though appear to decline during the

Heinrich events G bulloides does not exhibit any

specific trend and N pachyderma (s) is almost absent

The presence of Turborotalita quinqueloba is in

general higher between 48 and 11 kyr BP in the

southern Aegean Sea than in the central Mediterra-

nean (Capotondi et al 1999 Sbaffi et al 2001) It

seems that this cool species replaces other cold

species such as Globorotalia scitula and Neoglobo-

quadrina pachyderma (s) The abundance of G

scitula in the planktonic assemblages appears to

decrease eastwards in the Mediterranean Sea during

the early-Late Glacial period while N pachyderma (s)

is almost absent in the eastern Mediterranean (Hayes

et al 1999) Today N pachyderma (s) thrives in

seawater where SST is below 7 8C (Reynolds and

M Geraga et al Palaeogeography Palaeoclimatology Palaeoecology 220 (2005) 311ndash332 327

Thunell 1986) This may indicate that the cooling

during the stadials was not as intense in the eastern

Mediterranean as in the western Mediterranean The

MAT SST seems to support this hypothesis as it

shows that during H4 the SSTc was 9 8C while in thesame interval in the western Mediterranean it was 7

8C (Perez-Folgado et al 2003)

Increases in aridity attributed to Heinrich events

have been recorded in Greece in speleothems at cave

sites (Theopetra Cave Central Greece Karkanas

2001) and in terrestrial pollen records in Greece

(Galanidou et al 2000 Tzedakis et al 2002) Studies

in lake Xinias (central Greece) have shown lake-level

lowering at around 41ndash40 cal kyr BP and 32ndash30 cal

kyr BP (Digerfeldt et al 2000) The former interval

coincides with the C69-ST10H4 while the latter

appear about 2 kyr earlier than C69-ST7H3 In

addition oscillations of short duration between open

and forest communities during the Glacial Period have

been recognized in terrestrial pollen records from

Greece (Wijmstra 1969 Bottema 1974 Van Andel

and Tzedakis 1996 Tzedakis et al 2002) suggesting

climatic changes of short duration on land Stable

isotopic profiles of speleothems in Soreq cave in

Israel suggest the presence of Younger Dryas (132ndash

114 cal kyr BP) H1 (165 cal kyr BP) LGM (21ndash19

cal kyr BP) H2 (25 cal kyr BP) and H5 (46 cal kyr

BP) while H3 and H4 are not reflected in the record

(Bar-Matthews et al 1999) In the same study a

warm interval at 36 cal kyr BP probably correlates

with the C69-IST6 At the Lake Lisan (Israel) water

level drops have been documented at the times of H1ndash

H5 where the signal of H4 is very strong (Bartov et

al 2003)

The cooling of the sea surface temperature during

the Heinrich events in the southern Aegean Sea could

be a direct result of climatic deterioration in the

eastern Mediterranean region or an indirect effect of

the cold Atlantic surficial water flow The increase in

aridity shown in the pollen records during the stadials

suggests synchronicity between terrestrial and marine

data in the south Aegean region in response to short-

term climatic changes (Figs 6 and 7EF) Similar

suggestions have been made for marine pollen records

from the western Mediterranean region (Sanchez Goni

et al 2002) where during stadials the pollen zones are

characterized by the dominance of steppic plants

(Artemisia Chenopodiaceae and Ephedra) and during

the interstadials by the dominance of Quercus and the

reduction of the steppes

Climatic variability is also recorded during the

Holocene where three stadials (C69-ST1ndash3) have

occurred The C69-ST3 (10 cal kyr BP) is charac-

terized by a brief increase in y18O values and a brief

reduction in the abundance of the warm species

Globigerinoides ruber (Fig 4) A brief cooling event

around the same age (103 cal kyr BP) has been

identified in the UkV37 SST records in the western

(Cacho et al 1999) and the central Mediterranean Sea

(Sbaffi et al 2001) Although the SST is rather high

in this interval it shows a slight drop during winter

The C69-ST2 (8ndash65 cal kyr BP) is the most

prominent Holocene stadial and is characterized by a

rapid increase of semi-desertic vegetation and a

decline in SST During this event the y18O values

remain low The C69-ST2 seems to correspond to the

most widespread Holocene cold event of Europe

which occurred at around 82 cal kyr BP (Alley et al

1997) This event has been also identified in the UkV37

SST records in the western (Cacho et al 1999) and

the central Mediterranean Sea (Sbaffi et al 2001)

The C69-ST1 (55 cal kyr BP) is characterized by a

brief drop in SST During this interval the y18O values

show an increasing trend A brief cooling event

around the same age (54 cal kyr BP) has been

identified in the UkV37 SST records in the western

(Cacho et al 1999) and the central Mediterranean Sea

(Sbaffi et al 2001) The C69-ST2 and C69-ST1

events coincide with the interruption and the end of

the sapropel S1 respectively

All the abovementioned Holocene events in the

Cretan Basin are related to Holocene stadials docu-

mented in cores from high latitudes (Bond et al

1997) The C69-ST1 and C69-ST2 are the most

widespread Holocene events in the marine sediments

of the eastern Mediterranean Sea correlated with the

interruption and the final end of S1 (Rohling et al

1997 De Rijk et al 1999)

Two interstadials have been observed in the

Holocene C69-IST1 (65ndash6 cal kyr BP) and C69-

IST2 (9ndash8 cal kyr BP) These events which are

characterized by increased SSTs strong depletions in

y18O values and an expansion of temperate evergreen

and Mediterranean taxa coincide with the deposition

of the sapropelic layers S1a and S1b An increase in

humidity around this time has been documented in all

M Geraga et al Palaeogeography Palaeoclimatology Palaeoecology 220 (2005) 311ndash332328

marine and terrestrial pollen records in the eastern

Mediterranean region (Rossignol-Strick 1995)

The abovementioned stadials and interstadials

coincide well with the climatic cycles of dry and

wet events observed in the coastal belt of Israel in

combination with the level fluctuations of the Dead

Sea and Lake Lisan (Gvirtzman and Wieder 2001)

The dry events E5 (65ndash50 cal kyr BP) E7 (75ndash7 cal

kyr BP) and E9 (105ndash10 cal kyr BP) of the

abovementioned study coincide rather well with the

C69-ST1ndash3 in the present study and the wet events E6

(7ndash65 cal kyr BP) and E8 (10ndash75 cal kyr BP)

coincide rather well with the C69-IST1ndash2 in the

present data The three Holocene stadials and the two

interstadials which coincide with the formation of S1a

and S1b have also been recorded in the sediments of

C40 from the Myrtoon Basin based on the fluctua-

tions of the planktonic and pollen assemblages

(Geraga et al 2000)

42 Sapropel S1 and sapropelic S2

The sapropel S1 (S1a and S1b) and the sapropelic

S2 have shown a few common characteristics The

formation of both sapropels coincides with intersta-

dials S1a and S1b with the interstadials in Holocene

(C69-IST1 and C69-IST2 respectively) and S2 with

(C69-IST6) which probably corresponds to Ist8

(Dansgaard et al 1993 Cacho et al 2002) In both

sapropels the high depletions in y18O values (Fig 3)

do not seem to be accounted for only the increases in

the SSTs but seem also to be associated with the

prevalence of a low salinity surface layer (Vergnaud-

Grazzini et al 1977 Rossignol-Strick et al 1982)

During the formation of S1 the major sources of the

low salinity surface layer are considered to be the

southern Mediterranean catchment and the fresh water

discharges from the Black Sea to the Aegean Sea

(Aksu et al 1999 Sperling et al 2003) The ages of

S1 and S2 almost coincide with peak values of the

moonsonal index indicating increased precipitation

although the moonsonal index is greater during S1

(42) than during S2 (19 at 33 14C kyr BP) (Rossignol-

Strick 1983 Rossignol-Strick and Paterne 1999)

The high level of Lake Xinias in Greece (Digerfeldt et

al 2000) and the increase in temperate deciduous

trees in the pollen records of the present study during

the formation of S1 and S2 (Fig 6) indicate an

increase in humidity over the region Furthermore

regarding the formation of S2 an increase in fresh

water discharges from the Black Sea to the Aegean

Sea could have taken place due to the retreat of the

Scandinavian ice sheet during the Alesund period

(385ndash325 14C kyr) (Baumann et al 1995)

Differences between S1 (S1a and S1b) and S2

occur in the microfauna assemblages (Figs 4 and 5)

During the formation of S1 the planktonic foramini-

feral assemblages dominated by the Globigerinoides

ruber together with other warm-water species indicate

the presence of warm surficial waters During S2 the

G ruber hardly increased while cool species such as

Globorotalia scitula are present indicating that the

SST was lower than during S1 The planktonic

assemblage is dominated by Neogloboquadrina

which indicates the development of a DCM (Deep

Chlorophyll Maximum) layer (Fairbanks and Wiebe

1980) Furthermore the presence of infauna benthic

foraminifera in core C69 (unpublished data) during S2

indicates the development of dysoxic bottom waters

conditions whereas the absence of benthic foramin-

ifera in core C69 during the S1 indicates the

prevalence of anoxic bottom waters

The abovementioned suggests that during S2 the

prevalence of lower salinity surficial waters at the

Levantine region where the LIW (Levantine Inter-

mediate Water) is forming reduced the density

gradient between the Surficial Atlantic Water and

Intermediate Water masses and caused (i) a decline in

the water mass vertical circulation and (ii) a shoaling

of the pycnocline in the euphotic zone (Rohling and

Gieskes 1989) The latter resulted in the development

of the DCM layer and caused an increase in primary

productivity as is suggested by the increase of

Neogloboquadrina The water mass circulation

although reduced never ceased as is indicated by

the presence of benthic fauna and the existence of

oxygen in the bottom waters Increases in organic

fluxes and reductions in oxygen supply increased the

preservation of the organic material on the sea floor

resulting in the formation of the sapropel S2 The

above mechanism has already been proposed for the

formation of the sapropel layers during the Glacial

Period (Rohling and Gieskes 1989)

The formation of S1 is a combination of changed

water mass circulation and increased productivity At

that time the establishment of warm and low salinity

M Geraga et al Palaeogeography Palaeoclimatology Palaeoecology 220 (2005) 311ndash332 329

surficial waters due to increased rainfall in the

surrounding area and the consequently freshwater

run-off resulted in an enhanced stratification of the

water column (Vergnaud-Grazzini et al 1977 Rossi-

gnol-Strick et al 1982 Rohling and Gieskes 1989

Aksu et al 1999) The increased productivity during

the formation of S1 is related to the increased nutrient

discharge of the Nile (Rossignol-Strick et al 1982

Aksu et al 1995) although in varying intensity

(Meier et al 2004) Furthermore early studies based

on calcareous nanofossils and chemical records

suggest the presence of a DCM layer although in a

varying duration (Principato et al 2003 Meier et al

2004) Brief deep water ventilation events are

associated with the interruption in the formation of

S1 (Casford et al 2002) In the present study the

planktonic assemblages suggest an enhanced stratifi-

cation of the water column during the deposition of

S1a and S1b and a brief water ventilation during the

interruption of S1 A shoaling of the pycnocline can

be assumed during S1b due to the increase in the

abundance of the Globigerinoides sacculifer (Princi-

pato et al 2003) while the presence of Globorotalia

inflata just after the end of S1 mark the return of the

deep water ventilation

5 Conclusions

High resolution micropaleontological and pollen

analyses in combination with y18O data in the

sediments of core C69 from the southern Aegean

Sea showed that the study area is characterized by

climatic variability at millennium scale over the last

48 kyr The climate variations seem to correspond to

cycles of stadialndashinderstadials attributed to Dans-

gaardndashOeschger events although some of them differ

slight in age

Four of the recognized stadials in the Glacial period

seem to correspond to the Younger Dryas and the

Heinrich events H1 H2 and H4 One stadial recog-

nized in the Holocene seems to correspond to the most

widespread stadial in Holocene at 8 cal kyr BP In most

of the stadials the isotopes planktonic and pollen data

show synchronicity suggesting an additional opera-

tion of atmospheric processes The climatic signal

based on planktonic assemblages appears attenuated in

comparison to the western Mediterranean during the

stadials which are correlated with the Heinrich events

in the present study During these events the planktonic

fauna is dominated by Turborotalita quinqueloba and

Globorotalia scitula

The sapropel S1 appears in two layers (S1a and

S1b) Their formations coincide with the prevalence

of interstadials The interruption and the end of S1

coincide with stadials A sapropelitic sequence

corresponding to S2 occurs between 395 and 385

cal kyr BP and coincides with the prevalence of an

interstadial

Acknowledgments

We wish to thank the anonymous reviewers and

Prof MB Cita for their suggested improvements to

the manuscript This study was funded by the Hellenic

Scholarship Foundation (IKY)

References

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Jorissen FJ Asioli A Borsetti AM Capotondi L de Visser

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Different nutrient sources forcing increased productivity during

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Rohling EJ Gieskes WWC 1989 Late Quaternary changes in

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Shackleton N 2001 Response of the pelagic environment to

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Siani G Paterne M Michel E Sulpizio R Sbrana A Arnold

M Haddad G 2001 Mediterranean Sea surface radiocarbon

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Micropaleontology 10 35ndash69

Walter W 1974 Die Vegetation Ost-Europas Nord-und Zentrala-

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Wijmstra TA 1969 Palynology of the first 30 meters of a 120 m

deep section in Northern Greece Acta Botanica Neerlandica 18

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Williams DF Thunell RC Kennett JP 1978 Periodic fresh-

water flooding and stagnation of the Eastern Mediterranean Sea

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