High-resolution palynological analysis in Lake Sapanca as a tool to detect recent earthquakes on the North Anatolian Fault

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High-resolution palynological analysis in Lake Sapanca as a tool to detectrecent earthquakes on the North Anatolian Fault

Suzanne A.G. Leroy a,*, Sonay Boyraz b, Alper Gurbuz b

a Institute for the Environment, Brunel University, Uxbridge UB8 3PH, West London, UKb Ankara Universitesi, Muhendislik Fakultesi, Jeoloji Muhendisligi Bolumu, 06100 Tandogan, Ankara, Turkey

a r t i c l e i n f o

Article history:Received 12 February 2008Received in revised form19 May 2009Accepted 22 May 2009

a b s t r a c t

High-resolution palynological analysis of a 38-cm long core collected from Lake Sapanca, northwestTurkey, reveals large earthquakes that occurred during the second half of the 20th century along theNorth Anatolian Fault Zone. Four events have disturbed the lacustrine sedimentary sequence. Three ofthe four events are historical earthquakes in 1999 in Izmit, 1967 in Mudurnu and 1957 in Abant. Theseevents are recorded in the core by turbiditic deposits and reworked sediment and by low overall paly-nomorph concentrations but high values of thick-exined pollen, fern spores and fungal spores. Paly-nomorphs in the event beds have been grouped based on their associations in modern moss, river andlake samples. The inferred mechanisms of transport and sources for the palynomorphs are: 1- lakesediment displaced by slump, 2- collapsed shoreline sediment owing to seiche, waves and sudden lakelevel changes, 3- subsidence of deltas and 4- river-transported soil and sediment from upland areas. The1999 Izmit earthquake is only weakly recorded by palynomorphs, probably due to recent engineeringcontrol on the rivers. The 1967 Mudurnu earthquake had the strongest effect on the lake, introducingsuccessive packages of sediment to the centre of the lake from underwater slopes, the lakeshore andrivers.

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1. Introduction

Palaeoseismology traditionally relies on geomorphology, trenchdata, stratigraphy and radiocarbon dating to reconstruct ancientearthquakes and to infer their magnitude and recurrence times(Kurçer et al., 2008; Pantosti et al., 2008; Vandenberghe et al.,2009). Recent research has focused on palaeoseismic records fromlacustrine settings, an approach still hardly mentioned in reviewsof methodologies used in earthquake geology (Caputo and Helly,2008; Caputo and Pavlides, 2008). Lakes offer a more continuousrecord of sedimentation than trenches, which often are in alluvial/colluvial settings with coarse sediment and hiati. Magneticsusceptibility, sedimentary structures, geochemistry and particlesize analyses are the preferred tools for identifying earthquakes inlake sediments sequences (Doig, 1986; Becker et al., 2005). The newfield of earthquake limnology however is rapidly developing.

Palynological analysis is not commonly used in palae-oseismological investigations. When it is used, it is as a chrono-logical and palaeoecological tool. Coseismic uplift or subsidence

may alter vegetation, which in turn may be registered in pollenassemblages and concentrations within sediments (Mathewes andClague, 1994; Mirecki, 1996; Hughes et al., 2002). Exposure of newland following an earthquake can also be indicated in pollendiagrams by the presence of pioneer plants (Cowan and McGlone,1991). Coseismically triggered landslides may introduce largequantities of reworked sediment into lakes and seas, producingbeds with distinctive microfossil assemblages such as foraminifera.Syvitski and Schafer (1996), in a basin-wide failure of the SaguenayFjord, used several biological tracers to identify local and distalsediment sources. A crude Pinus/Picea ratio is used to indicatesediment reworking.

Turkey is seismically active with a 35–70% probability thatIstanbul, its megalopolis, will be struck by a large earthquake in thenext 30 years (Parsons, 2004). Thus studies that provide a betterunderstanding of the seismicity of the country are of considerableinterest. In this paper, we report the results of a study of cores takenin Lake Sapanca, which is about 90 km east of Istanbul and withinthe Marmara region, one of the most industrialized parts ofnorthwestern Turkey. This region has one-third of the industry andone-fourth of the population of Turkey (Union of Municipalities ofthe Marmara Region). The North Anatolian Fault Zone (NAFZ)(Fig. 1a and b), which extends through Lake Sapanca, is a strike-slip

* Corresponding author. Tel.: þ44 1895 266087; fax: þ44 1895 269761.E-mail address: [email protected] (S.A.G. Leroy).

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Quaternary Science Reviews 28 (2009) 2616–2632

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fault that has generated several disastrous earthquakes in the pastcentury (Straub et al., 1997).

Corroded pollen and spores can be used as indicators ofchanging lake sediment sources and catchment disturbance, as hasbeen done in palynological studies of some New Zealand lakesowing to major disturbance in the lake catchment, such as volca-nism, fire and deforestation (Wilmshurst and McGlone, 2005a).Pollen concentrations may reflect dilution of the lake sediment byinput of soil by erosion (Beaudoin and Reasoner, 1992). The iden-tification and the use of fungal spores and a range of non-pollenpalynomorphs (NPP) are still developed; but some of these paly-nomorphs have already been established as excellent indicators ofsoil erosion (Mudie et al., in press).

Palynology is here explored as a taphonomic indicator ofearthquakes. Special attention is given to pollen and NPP sources,preservation and concentration modifications in a cored sedimentsequence. We distinguish palynomorph assemblages derived fromvegetation in the hills and mountains surrounding the lake fromthose derived from a variety of sedimentary deposits in lowlandsbordering the lake. The steep slopes bordering the lake and withinthe lake ensures that the lacustrine depocentre is exposed tosediment derived from soil erosion and slope wash.

2. Physical setting and background information

2.1. Lake Sapanca

Lake Sapanca (40�430N, 30�150E) has a volume of about 109 m3

and a surface area of 49 km2, which is nearly five times smaller than

the catchment area, which is 250 km2 (Morkoç et al., 1998) (Figs. 1b,2 and 3). The lake surface is 31 m above sea level (asl) and itsmaximum depth is 55 m. Lake levels, which have been monitoredsince October 1955, fluctuate between w30 and w32.5 m asl. Ingeneral, the lake is lowest in October and highest in April (Elektrik_Isleri Etud _Idaresi, 2002). The lake is warm, monomictic and hol-omictic (Morkoç et al., 1998). Surface waters cool to 6.5 �C by latewinter and then warm steadily to 26 �C in late summer. Deep-watertemperatures range from 6.5 to 10.0 �C throughout the year(Morkoç et al., 1998).

Fifteen rivers, many of them ephemeral, feed the lake with thelargest inflows from the south. The rivers flow in incised, steep-walled valleys, across alluvial fans and delta plains into the lake(Gurbuz and Gurer, 2008b; Gurbuz and Leroy, in press). Somegroundwater inflow has also been noted (Erturk, 1994; Gurbuz andGurer, 2008a). Dams were constructed on the rivers in the 1970s toprevent coarse sediment from reaching the lake and graduallyfilling it, which would reduce the supply of water to the nearbytown of Adapazarı (Devlet Su _Isleri, 1984; Gurbuz and Gurer,2008a). Lake Sapanca discharges via the Çark River on the north-east shore into Sakarya River. A dam was built at the lake outlet in1979 to regulate the water level (Akkoyunlu and _Ileri, 2003; Gur-buz and Gurer, 2008a). The Sakarya River outflows into the lakeduring periods of high discharge via the marshy floodplain thatseparates the two (Russell, 1954; Dogan, 2004; Gurbuz and Leroy,in press).

The margins of the lake mostly consist of coalesced alluvial fans,terraces, Holocene beaches and prograding delta fans at the mouthsof the rivers (Rathje et al., 2004). Nearshore lake sediments are

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Fig. 1. a) Location of Lake Sapanca in NW Turkey. MS¼Marmara Sea, NAFZ¼North Anatolian Fault Zone. Black dot in dashed box¼ Lake Sapanca. b) Active faults near Lake Sapanca(modified from Lettis et al., 2000). LS¼ Lake Sapanca.

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sand, whereas sediments in the deepest part of the lake are mainlysilt (Gurbuz and Gurer, 2008a). Clayey sediment is restricted to thenortheast part of the lake. Gurbuz and Gurer (2008a) suggest thatthe deposition of the fine sediment in shallow water at thenortheast end of the lake results from regulation of the outflow.Another possible explanation is that the fine sediment is depositedwhen the Sakarya River flows into the lake. Gurbuz and Gurer(2008a) have also shown that more sediment is deposited off thesouth shore of the lake than the north shore, due to the larger

catchment sizes and steeper slopes in the hills and mountains tothe south (Fig. 3).

The Samanlı Mountains, which have a maximum elevation of1602 m at Kelltepe, lie south of the lake (Fig. 3). Gentle hillsborder the lake on the north (Gurbuz and Gurer, 2008b; Gurbuz,2009).

Lake Sapanca occupies a pull-apart basin created by a step-overalong the NAFZ (Barka et al., 2000; Lettis et al., 2000; Rathje et al.,2004; Gurbuz and Gurer, 2008a,c, 2009). The basin is bordered on

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Fig. 2. Sample sites in and around Lake Sapanca. Sample numbers correspond to those in Table 1. Symbols: white conifer trees¼moss samples, bold X¼ lake core tops, blackflowers¼ river samples. Core SA03K7.1 is located in the lake centre at coring station 7, under the cross numbered 7.

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Fig. 3. Map of vegetation around Lake Sapanca (modified from Ceylan, 1990).

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the north by the Sapanca fault segment of the NAFZ and on thesouth by a diffuse zone of normal faults (Lettis et al., 2002). It lies atthe intersection of the Kocaeli fault which ruptured on 17 August1999 (Mw 7.4) and the southern branch of the NAF, which mostrecently slipped during the 22 July 1967 (Mw 7.0) Mudurnu Valleyearthquake (Lettis et al., 2002; Gurbuz and Gurer, 2008b) (Fig. 1b).The May 1957 Abant earthquake (Mw 6.8) had an epicentre a fewkilometres east of the lake (Muller et al., 2003). The 20 June 1943Hendek earthquake (magnitude of Mw 6.4) occurred along the sameportion of the fault as the 1999 earthquake (Barka, 1999) andcaused much damage at Adapazarı (also called Sakarya), Hendek,Akyazı and Arifiye, just east of Lake Sapanca (Sahin and Tarı, 2000).

Earthquakes on the NAFZ are dominantly strike-slip events, butlocally have small components of normal displacement. Largeearthquakes on the Sakarya fault segment, east of the lake, produceright-lateral displacements of 2–5 m and vertical displacements of0.25–0.5 m (Rathje et al., 2004). Normal fault displacements havealso occurred during the 1967 Mudurnu valley earthquake(Ambraseys and Zatopek, 1969; Rathje et al., 2004; Gurbuz andGurer, 2008b).

Subsidence observed along the margins of Lake Sapanca duringthe 1999 Kocaeli earthquake was mainly due to failure of deltafronts. The most significant failure occurred on the south coast atHotel Sapanca (Çetin et al., 2002); a smaller failure happened on thenorth coast at Esme (Rathje et al., 2004). The earthquake alsoproduced liquefaction, sand boils and riverbank collapse, all ofwhich introduced large amounts of sediment to the lake (Bardetet al., 2000; Çetin et al., 2002).

It is likely that some soil and sediment were introduced intoLake Sapanca during the construction of the national road north ofthe lake in the 1950s, a railway in 1975 and a motorway along thesouth shore in the 1980s (Yalçın and Sevinç, 2001). Besides earth-quakes and construction, run-off from heavy rainfall can deliverlarge amounts of sediment to the lake.

2.2. Climate and vegetation

Mean annual precipitation and temperature at Adapazarı overthe past 30 years are 830 mm and 13 �C respectively (DevletMeteoroloji _Isleri Genel Mudurlugu, General Directorate of StateMeteorological Works). Storms with more than 80 mm of rainfallper day occurred on 3 July 1981 (88.1 mm), 30 July 1984 (82.3 mm),26 June 1999 (127.7 mm) and 24 July 2002 (93.7 mm). The moun-tains south of Lake Sapanca receive much higher precipitation thanAdapazarı and snow in winter.

Vegetation in the Lake Sapanca catchment is part of the Euxi-nian domain (Quezel and Barbero, 1985). The catchment is 55%forests and meadows, 33% agricultural land and 9% urban andindustrial land; 3% of the land is used for other purposes (Baykalet al., 1996). Most of the land directly bordering the lake is agri-cultural (Fig. 3). Some open spaces are occupied by macchia,a Mediterranean scrubland (Ceylan, 1990; Yılmaz, 2000). Thenorthern hills support a formation with various species of Quercusand are generally drier and more open than the southern hills andmountains. South of the lake, the Quercus formation is succeededupward by several altitudinal zones: Carpinus betulus – Castaneasativa – Quercus; C. sativa – C. betulus; Fagus orientalis forest withRhododendron ponticus; and F. orientalis with Pinus (Fig. 3). Abiesbornmulleriana and nordmaniana are present on the highest peaks.Soils around Lake Sapanca have a pH between 6.5 and 7.5 (M. Kibar,personal communication, 2005).

Aquatic plants grow in shallow waters along the south and westshores of Lake Sapanca and adjacent to marshland at the east end ofthe lake. Phragmites australis, Potamogeton pectinatus, Myriophyllumsp., Najas marina and Ceratophyllum sp. dominate on the south shore

(Albay and Akçaalan, 2008). Waters along the north side of the lakeare too deep to support significant macrophytic communities.

2.3. Pollen transport, preservation and concentration

The processes responsible for deposition of pollen and spores inlake sediment are airborne and water transports and, to a lesserextent, sediment redeposition (Pennington, 1979; Birks and Birks,1980). Pollen assemblages in river sediments and other high-energy deposits are different from assemblages in lake sediments(Birks and Birks, 1980; Leroy, 1992). The former commonly havemore spores, bisaccate pollen such as Pinus and heavy grains suchas the tetrads of Ericaceae. In a study of a lake in southern France,Andrieu et al. (1997) found higher Pinus percentages, but loweroverall pollen concentrations, in slumped sediments than in over-lying and underlying ‘‘normal’’ lacustrine sediment. Pollen trans-ported by rivers is derived from direct pollen rain, bank erosion andsurface run-off. De Busk (1997) found that surface samplescollected near the mouths of rivers in Lake Malawi had a higherratio of spores to pollen, consistent with derivation of paly-nomorphs from soils and bank erosion.

Pollen is generally not well preserved in soils unless the soil pHis less than 5.5 (Pennington, 1979; Birks and Birks, 1980; Wilm-shurst and McGlone, 2005a). Pollen and spores with resistantexines, however, can be preferentially preserved together withbiologically or chemically corroded palynomorphs (Schofield et al.,2007). During periods of soil erosion, these corroded grains canbecome incorporated into lake sediments (Wilmshurst andMcGlone, 2005b).

In general, changes in pollen and spore concentrations inlacustrine sediments reflect changes in vegetation cover and sedi-ment delivery to the lake. The vegetation cover around LakeSapanca has changed little in the past 50 years, apart from theintroduction of some invasive species and a slight reduction inforest cover due to construction of holiday homes, holiday resortsand timber exploitation.

2.4. Chronology and detection of earthquakes

A 6-cm diameter Kajak gravity corer was used to retrieve 14 coresup to 45-cm long during the summer of 2003. The cores werecollected along two transects across a strand of the NAFZ and in thedeep central basin, south of the fault (Fig. 2). In order to avoidinfluence from building activities along the lakeshore and to havethe most continuous records, the investigations focussed on corestaken in the lake centre. Details of sedimentological and geochem-ical studies of a 38.5-cm long core from the central transect(SA03K7.1, 40�4300500N; 30�1600500E) and some other deep cores arereported in Schwab et al. (2009) and are briefly summarised here.

Five cores, including core SA03K7.2 (taken close to SA03K7.1),were dated using 137Cs and 210Pb radionuclides. All cores showa similar chronology. The exponential 210Pb decay curve is inter-rupted by intervals with anomalous low values, which correspondto sedimentary disturbance events identified in sediment thinsections and from geochemical data. Background sedimentationrates were determined by subtracting event beds from the totalcore thickness. Peaks in 137Cs curves correspond to the peak inPacific nuclear weapon testing around 1964 and the Chernobylaccident in 1986 (Schwab et al., 2009).

Based on their study of the short gravity cores, Schwab et al.(2009) inferred four anomalous sedimentary events that inter-rupted the normal background sedimentation in Lake Sapanca.m-XRF geochemistry showed that the event beds contained higherconcentrations of elements derived from clastic sources. The most

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recent event (event 1) is marked by a turbidite (T1) and dates to the1999 Izmit earthquake. Event 2 is a homogenite (H) but only foundin a single location. It seems to be unrelated to an earthquake andprobably is the result of a local disturbance in the lake sedimen-tation (Fig. 2). Event 3 consists of both reworked material (R1 andR2) and turbidites (T2 and T3). It has been associated to the 1967Mudurnu earthquake on the basis of its age. Event 4 is a turbidite(T4) and reworked material that may be attributed to the Abantearthquake in 1957.

The sedimentation mode in the lake progressively changes, asseen at around 14.5 cm depth in core K7 (Schwab et al., 2009): frommore minerogenic to more organic (higher total carbon), from highvalues for many elements, such as Si, to lower ones, from high to

low magnetic susceptibility, from low to high water content, fromhigh to low bulk density, and from absence of diatoms to abundantdiatoms. Altogether these proxies suggest a high input ofallochthonous clastic material in the older sediments. According tothe chronology the sediments below 14.5 cm were laid downbefore w1985 (14.5 cm).

3. Material and methods

3.1. Modern samples and core sub-sampling

Modern mud and moss samples (1–8 ml of sediment) werecollected around Lake Sapanca, including the area between the

Table 1List of samples, including barren samples and those with too few pollen to be included in Fig. 4.

Sample numberin Fig. 2

Location Geographical coordinates Altitude in m or water depthin m (core depth in cm)

Sample name Sample type Details of rejected samples

1 N 40 45 868 030 14 449 177 Esme-Ahmediye moss2 N 40 44 013 030 13 126 44 Kuru River moss3 N 40 43 190 030 10 026 36 Chicken farm moss4 N 40 46 395 030 10 531 385 Quercus moss5 N 40 44 557 030 10 267 187 Fındık upstream moss7 S 40 38 441 030 13 830 354 Dagtarla Hill moss11 S 40 39 773 030 14 024 425 Pinus moss15 S 40 40 617 030 08 584 600 Keltepe Rd 600 moss14 S 40 39 613 030 08 757 800 Keltepe Rd 800 moss10 S 40 38 084 030 12 323 1039 Carpinus moss9 S 40 36 764 030 11 051 1097 Picea moss8 S 40 37 330 030 11 468 1120 Abies 1120 moss12 S 40 38 087 030 05 973 1460 Keltepe 1460 moss6 E 40 38 118 030 20 267 80 Bogaz/Sakarya moss

5 N 40 45 653 030 14 237 100 Kum Tepe river mud6 N 40 44 013 030 13 126 44 Kuru river gravelly mud9 N 40 43 190 030 10 026 36 Chicken farm river mud12 S 40 39 383 030 14 332 250 Balkaya (_Istanbul R) river mud13 S 40 40 866 030 15010 86 Guldibi (_Istanbul R) river mud17 S 40 42 131 030 14 923 41 Mahmudiye Delta river mud18 S 40 42 310 030 11 927 32 Kurtkoy Delta river mud19 S 40 42 722 030 10 497 67 Karaçay River river mud20 W 40 43 010 030 08 512 30 Musmula River river mud21 E 40 43 768 030 20 305 28 Regulator river mud22 E 40 43 020 030 19 636 31 Tennis Club marsh23 E 40 42 706 030 20 904 w30 Atmaca Street canal mud26 R 40 41 616 030 22 759 30 E. of Nehirkent canal mud27 R 40 40 268 030 22 760 34 Adliye Bridge river mud29 R 40 38 05 030 19 529 55 Dogançay river mud

C 40:43:55 030:15:10 29.5 (3) K1.2 lake mudC 40:43:40 030:15:10 31.5 (0–1) K2.1 lake mudC 40:43:05 030:15:30 52 (0–1) K6.1 lake mudC 40:43:05 030:16:05 54 (0–0.25) K7.1 lake mudW 40:42:53.4 030:10:27.1 15.2 (0–1) KA.2 lake mudW 40:42:55.7 030:09:56.0 11 (2) KB.2 lake mudW 40:42:54.7 030:09:41.3 4.5 (0–1) KC.2 lake mudW 40:42:53.0 030:10:54.9 21.7 (0–1) KD.1 lake mudW 40:43:35.5 030:12:12.0 25 (0–1) KE.2 lake mud

13 S 40 38 558 030 06 039 1600 Keltepe top moss no palynomorphs1 N 40 44 374 030 18 398 31 Esentepe sandy mud no palynomorphs2 N 40 44 186 030 16 026 37 Harmanlar delta river mud too poor & fungi3 N 40 44 232 030 14 604 32 Kocadere sandy mud fungi only4 N 40 43 706 030 13 997 39 Maden delta river mud too poor, resistant

palynomorphs & fungi7 N 40 44 011 030 12 220 37 Degirmen river river mud fungi only8 N 40 43 925 030 11 589 39 Fındık river river mud too poor & Pinus10 N 40 44 557 030 10 267 187 Fındık upstream river mud Pinus & fungi11 S 40 38 441 030 13 830 354 Dagtarla Hill river mud Alnus only14 S 40 41 557 030 16 750 39 Sarp river delta river mud too poor15 S 40 41 566 030 16 597 34 Keçi river delta sandy mud no palynomorphs16 S 40 41 912 030 15 859 42 _Istanbul river delta river mud fungi only24 R 40 42 457 030 23 185 41 Downed bridge river mud too poor & Pinus25 R 40 41 565 030 22 121 w30 Nehirkent canal mud Typha & fungi28 R 40 38 838 030 21 488 33 Bogazkoy sandy mud too poor & Pinus

Location: N¼ north, S¼ south, W¼west, E¼ east, C¼ lake centre, R¼ Sakarya River and surroundings.

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lake and the Sakarya River, in July 2005 to determine the sourcesof sediment and palynomorphs reaching the lake (Fig. 2; Table 1).The mud fraction of all rivers flowing into the lake and the out-flowing river was sampled at 29 locations, generally at lakeshore.Fifteen moss samples were collected from single polsters at the

lakeshore, the mountains south of the lake and in the hills to thenorth. The tops of nine Kajak cores were also analysed (Fig. 2;Table 1).

Sixty-nine samples of sediment from core K7.1 were analysedfor pollen, diatoms, lithology, total inorganic carbon, and total

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xc.−t.

0

•

F. orn

us

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Ligustrum

0

•

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•

••

•

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•••

•

Ole

a

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Phillyre

a

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••••

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tanus

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s

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nus

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us

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Salix

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Tilia

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us−Zelko

va

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sus

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Vitis

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Apiaceae

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••

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Artem

isia

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ure

a

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ure

a c

yanus

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ops

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••

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•••

••

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•

A. Liguliflorae

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Boraginaceae

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tropiu

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panula

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tus

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nth

em

um

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Caryophylla

ceae

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••

Ste

llaria

N

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R

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C

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MO

SSR

IVERLAKE

Esme−AhmediyeKuru RiverChicken FarmQuercusFindik UpstreamDagtarla HillPinusKeltepeRd 600KeltepeRd 800CarpinusPiceaAbies 1120Keltepe 1460Bogaz/SakaryaKum TepeKuru RiverChickenFarmMudBalkayaGuldibiMahmudiye DeltaKurtkoy DeltaKaracay RiverMusmula RiverRegulatorTennis ClubAtmaca StreetE. of NehirkentAdliye BridgeDogancayK1.2K2.1K6.1K7.1KA.2KB.2KC.2KD.1KE.2

%

a

b

Fig. 4. Percentage palynological diagram for modern samples collected in and around Lake Sapanca. Black dots are values less than 0.075%. N¼ north, S¼ south, W¼west, E¼ east,C¼ lake centre, R¼ Sakarya River and surroundings.

S.A.G. Leroy et al. / Quaternary Science Reviews 28 (2009) 2616–2632 2621

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organic carbon. To allow for a well-coordinated multiproxy-anal-ysis, small volumes and thicknesses, 0.4–1 ml of sediment between0.25 and 1 cm thick, had to be used for the pollen samples.Contiguous 0.25-cm thick samples were taken between the coretop and 10.25 cm depth and below this depth 0.25-cm thicksamples were taken and analysed at 1-cm spacing. Estimates ofinter-event sedimentation rates range from 0.18 to 0.33 cm yr�1

indicating that each sample represents a few months to one year oftime (Schwab et al., 2009).

3.2. Treatment and identifications

Palynological extractions were undertaken at Brunel Universityand at the University of Wales in Bangor (UK). All samples were

0

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Convolv

ulu

s

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is

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urialis

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lium

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niu

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Liliaceae

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Onagraceae

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nta

go

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nceola

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ajo

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Poaceae

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Poaceae 37μm

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Zea m

ais

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gonum

sp

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Poly

g. avic

.−bis

t. t.

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icaria

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ex

sp.

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R. aceto

sa

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ex a

ceto

sella

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Ranunculaceae

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Rosaceae

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inor

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Rubiaceae

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Solanaceae

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Thely

gonum

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Urticaceae−Morac

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Valerianaceae

306321425330339354380346377417302182488327140143203306125340273312334324322303133212417404419330437299333397323303

Sum

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Alis

ma

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Menyanth

es

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Myrioph. altern

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Myr. v

ertic

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Nym

phaea

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mogeto

n

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Ranunc. acris−t.

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Typha−S

parg

aniu

m

Esme−AhmediyeKuru RiverChicken FarmQuercusFindik UpstreamDagtarla HillPinusKeltepeRd 600KeltepeRd 800CarpinusPiceaAbies 1120Keltepe 1460Bogaz/SakaryaKum TepeKuru RiverChickenFarmMudBalkayaGuldibiMahmudiye DeltaKurtkoy DeltaKaracay RiverMusmula RiverRegulatorTennis ClubAtmaca StreetE. of NehirkentAdliye BridgeDogancayK1.2K2.1K6.1K7.1KA.2KB.2KC.2KD.1KE.2

N

S

R

N

S

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MO

SSR

IVERLAKE

%

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T. tetrad

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Monoletes psila

te

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M. non psil.

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Asple

niu

m

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Dry

opt. f.−m.

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Poly

p. vulg

are

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Thely

pte

ris p

al.

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••

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Triletes p

silate

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Tril. non psil.

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Ophio

glo

ssum

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•••

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Pte

ridiu

m a

quil.

−t.

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Anth

ocero

s

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Ric

cia

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••

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Indeterminated

0 20

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Indeterminable

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•

Reworked

38282425

44632589125385172

333593144517181296546555700431582349419207226864158038142272123031737014961

Concentration

0

•

Spirogyra

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Zygnem

a

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Glo

eotric

hia

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Oedogoniu

m

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Botryococcus

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••

••

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Pedia

strum

bor.

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Concentric

yste

s

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Dino thecae

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Brigante

din

ium

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Spin

iferite

s c

rucif.

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Spin

iferite

s rew

ork

ed

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Radio

sperm

a

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Fungal spores/1

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Glo

mus/10

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a

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Thecaphora

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Moss leaf

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Salv

inia

−Azolla

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Cera

tophyllu

m

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Stomata

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Filinia

Esme−AhmediyeKuru RiverChicken FarmQuercusFindik UpstreamDagtarla HillPinusKeltepeRd 600KeltepeRd 800CarpinusPiceaAbies 1120Keltepe 1460Bogaz/SakaryaKum TepeKuru RiverChickenFarmMudBalkayaGuldibiMahmudiye DeltaKurtkoy DeltaKaracay RiverMusmula RiverRegulatorTennis ClubAtmaca StreetE. of NehirkentAdliye BridgeDogancayK1.2K2.1K6.1K7.1KA.2KB.2KC.2KD.1KE.2

N

S

R

N

S

W

E

R

C

W

MO

SSR

IVERLAKE

% Analyses: S. Leroy

c

d

Fig. 4. (continued).

S.A.G. Leroy et al. / Quaternary Science Reviews 28 (2009) 2616–26322622

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Author's personal copy

successfully treated with Na4P2O7, HCl, HF and HCl, and sievedthrough 125 and 10 mm screens, with no acetolysis, except for mosssamples. Lycopodium tablets of known concentrations were addedto all samples, except mosses, to determine concentrations ofmicrofossils per millilitre of wet sediment. Pollen residues weremounted on glass slides with glycerol. Palynomorphs were countedunder a light microscope at a magnification of 400� routinely andat 1000� for special identifications. An attempt was made toidentify a minimum of 300 grains in each sample; smaller numberswere counted in samples with rare palynomorphs.

Pollen grains and spores were identified using the referencecollection at Brunel University and the pollen atlas of Reille (1992,1995, 1998). NPP include dinoflagellate cysts, which were identifiedusing data from the Caspian Sea reported by Marret et al. (2004).Radiosperma, which is present in the Baltic and Aral seas, isgenerally considered a brackish and marine organism (Sorrel et al.,2006). It is rare in the Black Sea (P. Mudie, personal communication,2008; Mudie et al., in press), but is present in the Caspian Sea (Leroyet al., 2007). Lake Sapanca sediments contain a diverse group offungal spores. In addition to the spores shown in the pollendiagrams (Figs. 4 and 5), Mycrothyrium, Tilletia and Sporormiellawere observed and are included in the ‘‘fungal spores’’ curve.

Pollen preservation differs considerably in the modern samples.Of the 53 modern samples (Table 1), only 38 contained pollen andspores in sufficient numbers to be statistically meaningful: 14 out of15 moss samples, 15 out of 29 river samples, and all 9 lake core tops.

3.3. Palynological diagrams and statistical analyses

Palynological diagrams were plotted using the software psim-poll4.10 (Bennett, 2007). All terrestrial and aquatic pollen grainsand spores were included in the concentration values, whereasspore and non-pollen palynomorphs, which are mostly planktonand benthos, were excluded. All terrestrial pollen grains in thepercentage diagram add up to 100% (i.e. the ‘‘sum’’ curve in thediagram, which is typically around 300). Aquatic plants and othermicrofossil remains are thus excluded from the sum and calculatedas a percentage of the 100% terrestrial sum.

Statistical analysis was performed using psimpoll4.10 (Bennett,2007). The zonation with CONISS after square-root transformationwas made based on the taxa included in the sum, as well as theaquatics, spores, NPP and indeterminable and reworked grains.Detrended component analysis (DCA) was done on the same suiteof palynomorphs (terrestrial, non-terrestrial and NPP) to identifythose that best reflect the changes in the diagram (Bennett, 2007)(Fig. 6). After plotting the taxa eigenvectors on the first two axes,the taxa with the highest values on axes 1 and 2 were selected,along with Castanea, which is an excellent altitudinal indicator.Dinoflagellate thecae, Convolvulus, Sagina, non-psilate trilete sporesand ostracod mandibles were not used. The distribution of thedinoflagellates differs according to preservation and the other fourmicrofossils are too scarce to be statistically significant. A newdiagram with the selected taxa was then plotted, focussed on thedisturbance events (Fig. 7a and b). A diagram of selected taxarepresenting the vegetation on the slopes around the lake andexcluding three of the four sedimentary events has been preparedto show the general trend in vegetation through the period span-ned by the core (Fig. 8).

4. Results

4.1. Taxa list and vegetation

The dominant arboreal pollen (AP) in surface samples are Pinus,deciduous Quercus, Fagus, Alnus, Cupressaceae, C. betulus and

Corylus; and non-arboreal pollen (NAP) are mainly Poaceae,Amaranthaceae–Chenopodiaceae and Tubuliflorae (Fig. 4). Juglans,Pistacia, Castanea, evergreen Quercus, Oleaceae, Fraxinus excelsior,Platanus and Salix are consistently present. Pollen grains of recentlyintroduced species such as Ailanthus altissima and Phacelia tana-cetifolia occur in some samples.

Taxa characteristic of brackish and marine environments arealso present, including Radiosperma, Spiniferites cruciformis, Brig-antedinium and Impagidinium caspienense. These organisms mayhave entered Lake Sapanca when it was connected to the Black andthe Marmara seas (Pfannenstiel, 1944), or alternatively may be theresult of a recent reintroduction of fish (Innal and Erkakan, 2006).In either case, they appear to have developed a tolerance tofreshwater.

Concentricystes is a palynomorph of unknown origin that maylive in soil and is commonly associated with soil inwash (B. vanGeel, personal communication, 1998). It also may live in lakes(Grenfell, 1995). Large quantities of fungal spores are interpreted tobe inwash of soil material. Glomus (type 207) is particularly usefulas it forms a symbiotic relationship with plant roots and is inter-preted to be an indicator of erosion (Van Geel, 2003).

4.2. Modern samples

Five moss samples are from the hills and shores north of LakeSapanca; eight samples are from the mountains and shores, southof the lake; and one sample was collected in a gorge near RiverSakarya (Figs. 3 and 4; Table 1). Northern samples contain higheramounts of Quercus, Cistus, Amaranthaceae–Chenopodiaceae,Poaceae and Cerealia-type (t.) than in the southern samples. Somemosses above 1000 m asl in the southern mountains contain psilatemonolete spores and Dryopteris filix-mas-t. spores. Altitudinalgradients are evident in the peaks of Juglans–Corylus–Alnus at354 m asl, Pinus at 425 m asl, Carpinus at 800 m asl, Castanea at1039 m asl, Rhododendron at 1000–1100 m asl, Fagus at 1460 m asl,and the highest values of Abies pollen above 1000 m asl (Figs. 2 and4; Table 1).

Southern mosses and mud samples are richer in C. betulus-t.,Fagus, Rhododendron and Castanea than northern samples. The fivesouthern delta samples have high values of Juglans. Liguliflorae andBrassicaceae are high in some northern mud samples and in thethree samples from the floodplain between Lake Sapanca and theSakarya River. Cyperaceae and Typhaceae percentages are partic-ularly high in the samples from the floodplain between the lake andthe Sakarya River. Fern spores are common only in mud samplesfrom deltas on the south shore. Green algae and cyanobacteriaoccur in samples east of the lake. Concentricystes is present in onlytwo samples: one along the Sakarya River and the other along theIstanbul River near the village of Guldibi. The three samples fromthe Sakarya River have relatively high values of Pinus and Salix.

Many of the lake delta and Sakarya River samples are sterile orcontain few palynomorphs other than fungal spores (Table 1).Reworked pollen and spores are mostly found in the delta samplesand in samples from the floodplain between Lake Sapanca and theSakarya River. The impoverished nature of these assemblages isexplained by the high soil content of the samples, the high energyof the depositional environment, and the oxygen-rich environ-ments to which the palynomorphs are exposed.

Four sediment samples were taken from the centre of the lakeand five samples were collected from the shallow western end ofthe lake. All lake sediment samples contain NPP and dinocysts andare the samples with the best palynomorph preservation. Thesamples from the west end of the lake are richer in Pinus, Cyper-aceae, aquatic vegetation and fern spores than those from the lakecentre.

S.A.G. Leroy et al. / Quaternary Science Reviews 28 (2009) 2616–2632 2623

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Author's personal copy

Lake Sapanca, core SA03K7.1, percentages Analyses: S. Leroy

5

10

15

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35

Depthcm

%

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Abie

s

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aya−t.

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Cedru

s

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Pic

ea

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Pin

us

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P. hapl.

0 10

Cupressaceae

0

Ephedra

dis

t.

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Ephedra

fra

gilis

0

•

Taxus

0

•

Acer

0

•

•

Pis

tacia

0

Rhus

0

Ilex

0

•

Hedera

0

Aln

us

0

•

•

••

•

Betu

la

0

Carp

inus b

etu

lus−t.

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•

••

•

C. orienta

lis/O

strya

0

Cory

lus

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Buxus

0

•

Hum

ulu

s

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•

Sam

bucus racem

osa

0

•

•

•

Vib

urn

um

0

Corn

us s

anguin

ea

0

Hip

pophae

0

Casta

nea

0

Fagus

0 10

Querc

us dec.

0

Q. se

mperv.

0

Jugla

ns

0

•

•

Pte

rocary

a

0

Myrica

0

•

•

Oleaceae

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Fra

xin

us e

xc.−t.

K10

K9

K8

K7

K6

K5

K4

K3

K2 K1

Lake Sapanca, core SA03K7.1, percentages Analyses: S. Leroy

5

10

15

20

25

30

35

Depthcm

%0

F. orn

us

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•

Lig

ustrum

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Ole

a

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Phillyre

a

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Pla

tanus

0

Populu

s

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•

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nus

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•

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Aila

nth

us

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Tam

arix

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Salix

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Tilia

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Celtis

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••

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Ulm

us−Zelk

ova

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sus

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Vitis

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Amarant.−Chenop.

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Apiaceae

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rae

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isia

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ure

a c

yanus

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C. ja

cea

0 10

••

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Ast. Liguliflo

rae

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Boraginaceae

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Echiu

m

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phytu

m

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Brassicaceae

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panula

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Cannabaceae

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tus

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ranth

us

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llaria

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ne

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ulu

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sa

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Ericaceae

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n

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Euphorb

ia

K10

K9

K8

K7

K6

K5

K4

K3

K2 K1

b

a

Fig. 5. Percentage palynological diagram of core SA03K7.1. Black dots are for values less than 0.25%. Horizontal exaggeration is 10�.

Page 11

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Lake Sapanca, core SA03K7.1, percentages Analyses: S. Leroy

5

10

15

20

25

30

35

Depthcm

%0

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urialis

annua

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Fabaceae

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Trifo

lium

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Phacelia

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••

Lamiaceae

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ium

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Liliaceae

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Lyth

rum

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Pla

nta

go

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P. la

nceola

ta

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P. m

ajo

r

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•

P. m

edia

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P. sem

perv

irens

0 10

Poaceae

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Poaceae 37μm

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Secale

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Zea m

ais

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moniu

m

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Calligonum

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Poly

gonum

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P. avic

ula

re−bis

t.−t.

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P. pers

icariaa

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•

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Rum

ex

0

•

•

•

R. aceto

sa

0

•

•

•

Rum

ex a

ceto

sella

0

•

•

•

Ranunculaceae

0

Thalic

trum

0

•

•

•

Rosaceae

0

•

Filipendula

0

Pote

ntilla

0

•

•

••

Sang. m

inor

0

S. offic

inalis

0

•

Rubiaceae

0

Sola

num

0

Daphne

0

•

•

Urticaceae−Morac

437 331305 316443 334310 359402 366338 297371 319350 260350 308380 358352 287320 412385 357340 409405 425386 367394 328376 374454 324307 355388323

417383

395281

303140

314142

181315

172223

437446

405429

342367

327370

319355

316156

10473

431

Sum

0

Cla

diu

m

0

Em

ex

0

Menyanth

es

0

Myrioph.a

ltern

.

K10

K9

K8

K7

K6

K5

K4

K3

K2 K1

Lake Sapanca, core SA03K7.1, percentages Analyses: S. Leroy

5

10

15

20

25

30

35

Depthcm

%0

Myr. v

ertic

.

0

•

•

Pota

mogeto

n

0

•

•

•

Ranunc. acris−t.

0

•

Typha−Sparg

aniu

m

0

T. te

trad

0 10 20

•

•

Monoletes psila

te

0

•M. non psil.

0

•

Asple

niu

m

0

•

•

Dry

opte

ris f.−

m.

0

•

•

Equis

etu

m

0

Isoete

s

0

•

•

Poly

p. vulg

are

0

•

Thely

pte

ris p

al.

0

••

•

Triletes p

silate

0

Tril. non psil.

0

Ophio

glo

ssum

0

•

•

•

Pte

ridiu

m a

quil.−t.

0

Anth

ocero

s

0

Ric

cia

0

Sphagnum

0

•

Indeterminated

0

Indeterminable

0

•

•

•

Reworked

0

Spirogyra

0

Zygnem

a

0

•

•

•

Glo

eotric

hia

0

•

•

Oedogoniu

m

0

•

Botryococcus

0

•

•

Tetraedro

n

0

Coela

strum

0

•

•

•

Pedia

strum

bor.

0

•

•

Concentric

yste

s

0

•Dinof. th

ecae

0

•

Brigante

din

ium

0

Impagid

. casp.

0

Spin

iferite

s c

rucif.

0

Radio

sperm

a

K10

K9

K8

K7

K6

K5

K4

K3

K2 K1

c

d

Fig. 5. (continued).

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4.3. Palynomorph assemblages in core K7.1

Despite the high temporal resolution of sampling, intra-annualfluctuations in pollen production and successive flower bloomingtimes cannot be seen in the data. It is likely that bioturbation ismixing the sediment at least at the annual scale (Fig. 5). Howeverthis bioturbation does not seem significant enough to blur theboundaries of event horizons, which in thin sections are welldefined (Schwab et al., 2009).

Ten palynological zones (pz) reflect changes in palynomorphassemblages through time in core K7 (Fig. 5). The main changeoccurs at around 16.6 cm depth.

Pollen concentrations range from 2900 to 44,000 grains per mland preservation is excellent, with very few damaged pollen andspores. From 38 to 16.4 cm, pollen concentrations are less than20,000 grains per ml. The lowest concentrations are at 37–35 and23–17 cm. Above 16.6 cm, pollen concentrations are mainly>20,000 grains per ml. Within this upper part of the core, relativelylow concentrations occur around 9.1 cm and 6.1–1.9 cm.

The pollen diagram shows relatively constant backgroundvalues of Alnus, Carpinus, Fagus, Corylus, deciduous Quercus, Juglansand Poaceae that may be considered normal for the lake sediment(pz K1, 4, 7–8 and 10) (Figs. 5 and 8). Superimposed on this back-ground are major variations in Pinus, Liguliflorae, fern spores,fungal spores and concentrations.

DCA on the samples shows the distribution of the ten palyno-logical zones in relation to the first two axes (Fig. 6b). Axis one

allows separation of the sequence into two parts – samples aboveand below about 15.5 cm. Pz K1–K6 plot on the right side of thediagram. Palynological samples associated with normal sedimen-tation in the lake are located near the centre of the plot. Pz K2–3, K6and K9 lie at the positive end of axis 2.

Pz K2 and K3 (37.6–34.5 cm) display a continuous curve ofRhododendron (Figs. 5 and 7a). The two zones have high values offern spores, indeterminable grains and reworked elements, espe-cially the base of pz K2. Fungal spores and Glomus are dominant inthe two zones. Pollen concentrations are the lowest among the coresamples.

Pz K5 (23.6–19.6 cm) has high values of Pinus (up to 45%) andLiguliflorae (up to 21%). Psilate trilete spores and Concentricystes arealso present. The concentration diagram (Fig. 7b), however, doesnot show the pine increase. Pz K6 (19.6–16.6 cm) has highpercentages of fern spores and reworked elements. Fungal sporesand especially Glomus are abundant in pz K5–6. Both zones havelow pollen concentrations.

Pz K9 (6.25–2 cm) contains common Rhododendron pollengrains. Fern spores are also present, but in low amounts. Concen-trations vary considerably through this pollen zone, with some lowvalues.

4.4. Interpretation of palynological zones

The palynological diagram with the disturbance taxa (Fig. 7) canbe interpreted using modern samples and statistical results (DCA

Lake Sapanca, core SA03K7.1, percentages Analyses: S. Leroy

5

10

15

20

25

30

35

Depthcm

%

0 10 20 30 40 50 60 70 80 90 100

Fungal spores/1

0

0 10

•••

•••••••••••

•

•

•

Glo

mus/10

0

•

Tetraplo

a

0

•

Thecaphora

0

•

•

•

Moss leaf

0

Salv

inia

−Azolla

0

•

Cera

tophyllu

m

0

•

Stomata

0

•

•

•

Filinia

0

•

Tin

tinopsis

0

•

•

Ostracod mandib.

K10

K9

K8

K7

K6

K5

K4

K3

K2 K1

Total dispersion

0 1 2 3 4 5 6 7 8

e

Fig. 5. (continued).

S.A.G. Leroy et al. / Quaternary Science Reviews 28 (2009) 2616–26322626

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on taxa (not shown) and zonation). We identify five groups of taxa;the taxa in each group display similar trend and have similar modesof transport to the lake (Figs. 4 and 6). The first group includesthe ‘normal’ lake sediment palynomorphs (see below Section 5.4).The other four groups comprise disturbance indicators. Theassemblages associated with disturbance events reflect dilution of

the background sediment deposited in the lake by large inputs ofsoil and river-transported sediment, which contain little pollen.

Group 2 consists of Liguliflorae, Lamiaceae, Concentricystes andGlomus. These palynomorphs are resistant to chemical corrosionand their presence is the result of differential preservation. Glomusand Concentricystes are indicators of soil erosion. This group is

group 2 3 4 5

K10

K9

K8

K7

K6

K5

K4

K3 K2 K1

T1

H

R1

R2

T2

T4

T3

polle

n zon

e

sedim

entar

y

even

t

19991967

1957

earth

quak

e

5

10

15

20

25

30

35

Depthcm

%

0 20 40

Pin

us

0

Ast. Liguliflo

rae

0

Lamiaceae

0

Concentric

yste

s

0

Glo

mus/10

0

Triletes p

silate

0

Pte

ridiu

m a

quil.−

t.

0

Indeterminable

0

Reworked

0 20 40 60 80 100

Fungal spores/1

0

0 20

Monoletes psila

te

0

Asple

niu

m

0

Dry

operis filix−m

.

.

0

Anth

ocero

s

0

Abie

s

0

Casta

nea

0

Rhododendro

n

0

Monoletes non psila

te

.

× 105

0 10 20 30 40

Concentration

% microfossils per ml

Fig. 7. Palynological diagram of selected disturbance indicators in core SA03K7.1. (a) Percentages, and (b) Concentrations.

-

-0.4

-0.3

-0.2

-0.1

0.1

0.2

0.3

0.4

0.5 0.7 0.9 1.1

-

-0.4

-0.3

-0.2

-0.1

0.1

0.2

0.3

0.4

0.5 0.7 0.9 1.1

b c

T1

T2

T4

R1

R2

H

K2-3

K6

K9

K5

K10

K9

K8

K7

K6

K5

K4

K2

T1

H

R1

R2

T2

T4

T3

polle

n zon

e

sedim

entar

y

even

t

1999

1967

1957

earth

quak

e

even

t 1ev

ent 3

even

t 4ev

ent 2

a

Fig. 6. Results of detrended component analysis for samples from core SA03K7.1 on axis one (horizontal) and axis two (vertical). Relations between (a) pollen zones, events andearthquakes; (b) pollen zones; and (c) sedimentary events.

S.A.G. Leroy et al. / Quaternary Science Reviews 28 (2009) 2616–2632 2627

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attributed to inwash of soil from shorelines or nearshore openareas, but away from deltas because of the lack of indicators of rivertransport. The dominance of group 2 coincides with low concen-trations of palynomorphs (Fig. 7a and b).

Group 3 consists of reworked and indeterminable grains, psilatetrilete spores, Pteridium aquilinum and fungal spores. It is anintermediate between groups 2 and 4. Its taxa are common in soilsand river sediment. The concentration diagram (Fig. 7b) indicates

that their contribution to the lake has been fairly constant over theperiod of record. High percentage values at times of the disturbanceevents are caused by relative decreases in the concentrations ofmost of the other taxa.

Group 4 consists of psilate monolete spores, Asplenium, D. filix-mas-t. and Anthoceros spores. High frequencies of these fern andmoss spores indicate derivation from soils in humid areas, such asalong rivers.

5

10

15

20

25

30

35

Depthcm

× 104

0 20

Carp

inus b

etu

lus−t.

× 104

0 20

Fagus

× 104

0 20

Cory

lus

× 104

0 40

Querc

us

dec.

× 105

0 8

Pin

us

× 103

0 40

Ast. Liguliflo

rae

× 103

0 8

Concentric

yste

s

× 103

0 20

Glo

mus/10

× 103

0 20 40

Triletes p

silate

× 103

0 20

Pte

ridiu

m a

quil.−

t.

× 104

0 8

Indeterminable

× 104

0 20

Fungal spores/1

0

× 103

0 40

Monoletes psila

te

× 103

0 8

Asple

niu

m

× 103

0 20

Dry

opte

ris filix−m

.

.

× 102

0 20 40

Anth

ocero

s

× 103

0 20

Abie

s

× 104

0 20

Casta

nea

× 103

0 8 16

Rhododendro

n

× 103

0 20

Monolet non psilate

K10

K9

K8

K7

K6

K5

K4

K3

K2 K1

T1

H

R1

R2

T2

T4

T3

pollen zone

sedimentary

event

19991967

1957

earthquake

group 2 3 4 51

microfossilsper ml

Fig. 7. (continued).

Lake Sapanca, core SA03K7.1, trend on selected taxawithout earthquakes events Analysis: S. Leroy

2

4

6

8

10

12

14

16

Depthcm

%0 10 20

Pin

us

Cupressaceae

Aln

us

Carp

inus b

etu

lus−t.

Cory

lus

Fagus

0 10

Querc

us dec.

Q. se

mperv.

Jugla

ns

Pla

tanus

Salix

Amarant.−Chenop.

0 10

Poaceae

K10

K7-8

K4

K1

Pollen zones

Fig. 8. Pollen diagram for selected taxa with the sediment related to earthquake removed. Horizontal exaggeration is 10�.

S.A.G. Leroy et al. / Quaternary Science Reviews 28 (2009) 2616–26322628

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Group 5 consists of Abies, Castanea and Rhododendron. Pollengrains of these taxa are derived from plants growing in themountains south of the lake. This group also includes non-psilatemonolete spores whose values change coincidentally with those ofAbies, Castanea and Rhododendron (Fig. 6). Accordingly all thesetaxa are taken to indicate pollen and spore input from soils at highaltitudes, south of Lake Sapanca.

The four groups of disturbance indicators are distributed throughthe core as follows (Fig. 7). Pz K2 and K6 contain groups 3, 4 and 5,and thus record inputs of soil material by rivers, including elementsderived from the southern mountains. Pz K5 has a strong signatureof group 2, clearly differentiating this zone from all others in thediagram. This zone records a significant input of soil materials nearthe lake shoreline, probably through mechanisms such as bankcollapse. River transport is quasi excluded for this zone. Smallincreases of groups 4 and 5 in pz K9 record river transport from highelevations with no evidence of pollen derived from the shores of thelake. Pz K3 is a transition zone comprising only a single sample.

In brief, the palynological events are clearly caused by dilutionof the lake sediment by various types of soils and river sediment,which are respectively barren or poor in pollen.

5. Discussion

The discussion starts with the main shift in the middle of thecore as it affects how the events are expressed in the sediment andthe palynomorph assemblages. Then the discussion focuses on theevents and the sources of palynomorphs. It finished by looking atthe general trend in the evolution of vegetation in the area, outsideof any event.

5.1. Shift to a cleaner lake at 17–14 cm

The shift from relatively low pollen concentrations to relativelyhigh ones at c. 16.6 cm depth, and the main change in the dendro-gram between pz K6 and K7 (Figs. 5 and 6), correspond to changesseen in the study by Schwab et al. (2009) – a decrease of detritalelements such as Si, Al, K and Ti at c. 14.5 cm and a the generalincrease in carbon above 15 cm. These changes are evidence ofa decrease in the delivery of clastic sediment to the lake. The shiftoccurs before the 1986 Chernobyl event. Possible causes includechanges in land-clearing practices, the end of the main constructionworks around the lake and damming of rivers flowing into the lake.The last possibility is considered the most likely.

5.2. Sedimentary and palynological events

Comparison of events detected by thin sections and geochem-ical analyses (Schwab et al., 2009) and those inferred from pollenanalyses reveal synchroneity of some events and other events thatare seen only in sedimentology. The three turbidites, T1, T2 and T4(the small T3 was not sampled for palynological analysis because itis too thin) lie at the positive end of axis 2 of the DCA plot (Fig. 6c).The two reworked zones (R1 and R2) plot at the lower right side ofthe diagram, and the homogenite (H) plots at the lower left. Normallake sediment plots near the centre of the diagram. The pollenzones relate in the following way to the inferred sedimentologicalchanges (Fig. 7).

Event 4, which deposited the T4 turbidite, is attributed to the1957 Abant earthquake. Pollen zones K2–3 correspond to the T4turbidite, except that pz K3 ends 2 cm earlier, below the top of theturbidite layer. It is likely that the upper part of the turbiditic layer(T4) comprises lake sediment displaced from slopes higher in thelake, thus making it indiscernible by palynology. So this event isa succession of distinctive sediment packages: river-transported

soils with altitudinal soils from the south mountains, topped bysome lake sediment.

Event 3 is responsible two reworked layers (R2, and R1) and twoturbidite layers (T3 and T2). It is attributed to the 1967 Mudurnuearthquake. Although a distinctive sediment layer, the signature ofR2 cannot be seen in the pollen diagram. The pollen spectra andconcentration are similar to those one might expect in ‘normal’ lakesediment. In contrast, R1 coincides with pz K5, which is attributedto sediment derived from exposed lakeshore. T2 correspondsexactly to pz K6. So this event consists of sediment delivery firstfrom the nearest to the core site and later from mountain water-sheds far away. Lake sediment (R2), soil (R1) and finally a mix ofriver and montane soils (T2) are successively observed. The rupturezone of the Mudurnu earthquake, therefore, appears to have hada strong effect on Lake Sapanca. The rupture occurred along whatMuller et al. (2003) and Gurbuz and Gurer (2008b) call the activemountain-front fault located along the foot of Samanlı Mountains(Figs. 1b and 2). The level of Lake Sapanca fell 24 cm during theearthquake and remained at that level for 24 h (Ceylan, 1990).

Event 2 (H), which is recorded by a homogenite layer (H) in onlytwo cores at station K7, is attributed to an unknown local event,possibly anthropogenic in origin. Homogenite H, which spans theend of pz K7 and the beginning of pz K8, is very poorly expressed inthe pollen diagram, only by a drop in concentrations and a smallpeak of Liguliflorae at 9.6–8.9 cm depth. The sedimentary homog-enite, therefore, is not homogenous in its pollen content.

Event 1 (T1) produced turbidite layer T1 and is attributed to the1999 Kocaeli earthquake. T1 corresponds to Pz K9. The sediment isstrongly influenced by inwash of soil and sediment from themountains to the south of Lake Sapanca. The smaller impact of the1999 earthquake relative to the 1957 and 1967 events is largelyattributed to the construction of dams in the 1970s on riversflowing into Lake Sapanca and the resulting interruption of thesediment supply. These engineering works were successful inreducing sediment delivery to the lake, although the 1999 earth-quake caused more damage than the previous two.

5.3. Sediment delivery mechanisms

The flux of sediment and soils to Lake Sapanca increases duringand following earthquakes. This palynological study providesevidence for four main sediment and soil sources (Fig. 9).

Firstly slumps and turbidity currents from steep slopes withinthe lake deliver sediment to the centre of the lake from both northand south sides of the basin. Gurbuz and Gurer (2008a) showedthat most of the terrigenous sediment carried into Lake Sapancatoday accumulates on the southern shore of the lake. This sedimentis unstable and available for transport and redeposition in the deepcentral part of the lake following disturbances such as earthquakesor storms. Resuspension and redeposition deliver palynomorphs ofgroup 1 and, to a lesser extent, all other groups to the lake centre.

Secondly, seiches, waves or a sudden change in lake level maydestabilise the shallow areas of the lake and erode the shoreline. Asmall seiche was reported in Lake Sapanca near Esme after the 1999earthquake (A. Gurbuz, field observations), but no seiches have beenreported during other historic earthquakes. More importantly,landslides and turbidites can produce internal and surface waves thatcan erode, respectively, underwater slopes and the shore. Coseismiclandslides during the 1999 earthquake were mapped at three placesby Lettis et al. (2002): one near Esme and at two places near SapancaTown. Landslides may be indicated by the presence of palynomorphgroups 1 and 2, but the influence of other groups can also be felt.

Thirdly, onshore liquefaction and subsidence of deltas happenedat the Sapanca Hotel during the earthquakes in 1967 and 1999(Ambraseys and Zatopek, 1969; Bardet et al., 2000; Çetin et al.,

S.A.G. Leroy et al. / Quaternary Science Reviews 28 (2009) 2616–2632 2629

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2002). Palynomorphs of groups 1 and 4, and to a lesser extent ofgroups 3 and 5, are well represented in the sediments resultingfrom these historic earthquakes.

Fourthly, erosion entrains soil and sediment along river coursesfrom their headwaters to the river mouths at Lake Sapanca.Photographs taken by the United States Geological Survey after the1999 earthquake show turbid plumes of water in Lake Sapanca andat the mouths of nearby rivers (http://gees.usc.edu/GEER/Kocaeli/Sapanca%20Lake.htm and http://gees.usc.edu/GEER/Kocaeli/Aerial%20Survey.htm). Palynomorphs of groups 4 and 5 would beintroduced by bank collapse and erosion. Group 3 palynomorphswould progressively be added along the lower reaches of rivers.After an earthquake, rain and aftershocks continue to deliverdestabilised sediment to the lake, which may explain the presenceof altitudinal pollen grains (group 5) in disturbance layers in LakeSapanca.

5.4. Trend in vegetation changes

A long-term trend diagram has been prepared by eliminatingfrom the sequence the following disturbance zones: (1) pz K2, pzK3 and the lower part of pz K4 which are products of event T4; (2)the top part of pz K4, pz K5 and pz K6 to record event R2; and (3) pzK9 (Fig. 8). The reduced 18-cm long sequence shows that Corylusand Fraxinus ornus percentages slightly increase towards the top ofthe core. In the lake, Gloeotrichia, S. cruciformis, the other dinofla-gellates and Tetraedron show increased percentages. Fagus andAmaranthaceae–Chenopodiaceae slightly decrease upwards (Figs.5 and 8). Zea mais is replaced upward by Secale. Therefore in thesecond half of the 20th century, human activities and climaticchange have had minimal effects on the pollen record whencompared with seismic events 4, 3 and 1.

6. Conclusions

Changes in concentration and assemblages of palynomorphs inthe uppermost sediments in Lake Sapanca are related, in part, tolarge 20th century earthquakes. The provenance of palynomorphsin sedimentary layers attributed to the earthquakes was

determined by comparison with the pollen assemblages of modernsediment samples. Palynology provides a clear signal of differentsediment and soil provenances and delivery mechanisms, includingsubaqueous slumps and turbidity currents, liquefaction and failureof shoreline sediments, and collapse and erosion of river banks inthe mountains south of the lake. The location of Lake Sapanca in anarea of high relief enhances some of these phenomena.

Lower-than-normal pollen concentrations reflect periods ofanomalous delivery of soil and sediment to Lake Sapanca, fromsource sediments that are impoverished in pollen. A survey ofmodern soil and sediments around the lake, including deltas andmoss polsters, indicated that the soils and sediments reworkedduring earthquakes have little pollen. Lake sediments derived fromthese materials are proportionally richer in spores and in pollengrains with resistant exines than sediments derived from othersources.

Of the four disturbance events identified by Schwab et al.(2009), three are recorded in the palynomorph assemblages of coreSA03K7.1: historical earthquakes in the 1999 (Izmit), 1967(Mudurnu) and 1957 (Abant). The 1999 earthquake is the leastevident in the pollen, probably because dams constructed on riversflowing into Lake Sapanca intercepted most of the sedimentproduced by the earthquake. The 1967 Mudurnu earthquake is thebest expressed in the core, because of the proximity of the epi-centre to the lake.

The 38.5-cm long core described here contains as much dis-placed sediment as ‘normal’ lacustrine sediment. Researchersshould consider such disproportionate representation of sedimentproduced by disturbance events when carrying out palaeoclimaticresearch on lake sediments in seismic areas.

The methods used in this study are novel and offer promise inpalaeoseismic investigations in seismically active regions. They are,however, time-consuming if applied to longer cores at the samelevel of detail as used in this study.

Acknowledgements

We are grateful to Fatih Uysal (Ankara University) and Sebas-tien Bertrand (Brunel University) for help in collecting the

Delta s

ubsidence

Seiche/waves

Palynomorph group 1 lake2 lake shore 4 river bank 5 altitudinal forest Mountain

Shore collapse

1

1 & 2

1 & 4

4

5

2

1

Fig. 9. Schematic representation of palynomorph sources by groups.

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modern samples and for providing the data on the region. Wecollected the short cores with the support M. Albay of the Facultyof Fisheries of Istanbul University. The core chronology is basedon data from E. McGee (University College Dublin, Ireland) andwas established with the help of P. Werner and M. Schwab(Brunel University). Multiproxy analysis of the Kayak cores wasdone by a group of researchers and students from BrunelUniversity. The study was funded by the European Union as partof the EC Project RELIEF (EVG1-CT-2002-00069). M. Turner(Brunel University), John Clague (Simon Fraser University) andOliver Korup (Swiss Federal Research Institutes) helped improvedthe English of the manuscript. This paper is a contribution to IGCPProject 490, the ICSU Dark Nature project and the INQUA TERPROCommission.

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