Studia Quaternaria, vol. 30, no. 1 (2013): 5–17. DOI: 10.2478/squa-2013-0001

LATE GLA CIAL AND HO LO CENE MOL LUS CAN AS SEM BLAGESIN DE POS ITS FILL ING PALAEOLAKES IN NORTH ERN PO LAND

Witold Pawe³ Alexandrowicz

AGH Uni ver sity of Sci ence and Tech nol ogy, Fac ulty of Ge ol ogy, Geo phys ics and En vi ron ment Pro tec tion,Chair of Ge ol ogy and Geoturism, Al Mickiewicza 30, 30-059 Cra cow; e.mail: wpalex@geol.agh.edu.pl

Ab stractLate Gla cial and Ho lo cene car bon ate lac us trine de pos its de vel oped as lac us trine chalk and cal car e ous gyttja are fairlywide spread across north ern Po land. They form fill ings of palaeolakes which de vel oped dur ing the deglaciation. Thesefor ma tions are usu ally cov ered by peat. Rich and di ver si fied malacofauna has been found in the afore men tioned sed i -ments. The pro files from 154 sites de scribed and pub lished by var i ous au thors were sub jected to malacological anal y -sis. In the whole ma te rial, 18 mol lus can as sem blages were dis tin guished, rep re sent ing three types of hab i tats: terres-trial, of tem po rary wa ter bod ies, and of per ma nent wa ter bod ies. The com po si tion and struc ture of these as sem blagesal lows char ac ter iz ing cli mate and dif fer en ti at ing hab i tats. The time-se quences of malacological as sem blages pro vided pos si bil ity to de fine three types of malacological se quences. On the ba sis of these suc ces sions, a scheme of the lakewa ter bod ies evo lu tion dur ing Late Gla cial and in north ern Po land was elab o rated.

Key words: lac us trine chalk, cal car e ous gyttja, palaeolakes, mol lus can as sem blages, Late Gla cial, Ho lo cene, north ernPo land

IN TRO DUC TION

The lac us trine chalk and cal car e ous gyttja form the fill -ings of palaeolakes which de vel oped in high num bers dur ingthe deglaciation. These may also be found on the coasts ofpres ent-day lakes where they mark their pre vi ous wider ex -tents. The ac cu mu la tion of these lake sed i ments oc curredchiefly dur ing tran si tional pe ri ods be tween cold gla cial pha-ses and warm interglacials when dead ice blocks, trappedear lier in mo raine or glaciofluvial sed i ments have melted.Drain age-less de pres sions of var i ous sizes, depths and shapeswere formed, and be came stag nant bod ies of freshwaters, sub -jected to com plex evo lu tion dur ing the Late Gla cial and Ho -lo cene. Some of them trans formed into per ma nent lakes,oth ers were filled with de pos its and be came peat bogs, and fi -nally, ter res trial hab i tats with var i ous mois ture lev els. Thecourse of sed i ment-fill ing and dis ap pear ance of these de -pres sions was re con structed and de scribed by nu mer ous au -thors. The age of great ma jor ity of the sites with car bon ate ormin eral de pos its fill ing palaeolakes is linked to de clin ingphase of the last gla ci ation and with the Ho lo cene. Alsoknown are the oc cur rences of these sed i ments of the ear lierinterglacials, mainly Eemian and Mazovian (Holsteinian)(e.g. Skompski, 1996; S. W. Alexandrowicz and W. P.Alexandrowicz, 2010).

Palaeolakes are filled with var i ous types of sed i ments.Com mon, and the most im por tant from the view point ofmalacological stud ies, are lac us trine chalk and cal car e ousgyttja.

Lac us trine chalk is a car bon ate sed i ment oc cur ring as are sult of pre cip i ta tion of CaCO3 in wa ter. This pro cess is par -

tic u larly in ten sive in the wa ter bod ies with abun dant veg e ta -tion which can be as so ci ated with up take of car bon di ox ideby plants dur ing pho to syn the sis. The cal cium car bon ate con -tent ex ceeds 80%. The sed i ments are white, grey, some timesyel low ish or brown ish. Some of them con tain small lumps ofcal cium car bon ate, and some times oolith or stromatolith-type struc tures (e.g. Rzepecki, 1983; Rutkowski et al., 2002;Freytet and Verrecchia, 2002). Very of ten, the lac us trinechalk con tain rem nants of molluscs and ostracods.

The name of cal car e ous gyttja is given to these lake sed i -ments that con tain from 50 to 80% of cal cium car bon ate. De-pend ing on the pro por tions of other com po nents e.g.: min eralor or ganic sub stances, or or ganic de tri tus, a num ber of typesare dis tin guished among cal car e ous gyttja. The clas si fi ca tionof the ses sed i ments were taken up by many stud ies (e.g. Mar-kowski, 1980; Rzepecki, 1983; Freytet and Verrecchia, 2002).

The car bon ate de pos its are ac com pa nied by min eral de -pos its: sands and silts, and more rarely – grav els. Among thegrav els, cob bles of Scan di na vian rocks are rep re sented mostof ten by gran ites, gneiss es or por phy ries. In terms of their or -i gin these are ei ther mo raine or glaciofluvial for ma tions. Inmany sites these de pos its oc cur at the bot tom of palaeolakese quences.

Peats are of es sen tial im por tance. They are as so ci atedwith boggy en vi ron ments and usu ally de velop in the fi nalstage of evo lu tion of lake wa ter bod ies. They there fore oc curat the top of depositional se quences and tes tify to over grow -ing of lakes and their trans for ma tion into moist ter res trial en -vi ron ments. Thin interlayers or lenticles of peats are some-times found also within the lake sed i ments. Their pres enceproves tem po rary shallowing of the lakes.

The in ter nal struc tures of the palaeolake fill ings is of tenvery com pli cated due to vary ing pro por tions and mu tual re la -tion ships be tween the afore men tioned prin ci pal ge netictypes of sed i ments. A to tal thick ness of for ma tions of thepalaeolakes is from 0.5 to over 10 m.

Lac us trine chalk and cal car e ous gyttja of ten abound inshells of snails and bi valves. It is prin ci pally caused by highcon tent of CaCO3 in the sed i ments. Rem nants of mol luskshells, usu ally less pre served and of ten bear ing the traces ofchem i cal dis so lu tion may some times ap pear also withinpeats that ac com pany the car bon ate sed i ments. Pres ence ofmol lus can shells in the lake sed i ments of Late Gla cial and innorth ern Po land was re corded as early as in the 19th cen turyand the early 20th by Ger man ge ol o gists (e.g. Keilhack, 1888; Menzel, 1911). More de tailed anal y ses of mol lus can fauna in lac us trine chalk were un der taken by Dembiñska (1924) dur -ing inter-war pe riod. Af ter WWII, a great prog ress was madein re search of car bon ate lake sed i ments. Dur ing the wide-range map ping and de posit doc u men ta tion works, more thanten thou sand sites with lac us trine chalk and cal car e ous gyttjawere lo cated and cat a logued. Some of them be came the top -ics of de tailed and in ter dis ci plin ary stud ies, but huge ma jor -ity still awaits a more elab o rated re search. De spite the factthat shells of snails and bi valves com monly oc cur in lac us -trine chalk and cal car e ous gyttja, the state of rec og ni tion ofmalacocoenoses is far for be ing suf fi cient. In vo lu mi nousref er ences there are many men tions on pres ence of malaco-fauna but with out spe cies iden ti fi ca tion. One can even as -sume that in many cases the shells of molluscs have beenomit ted or gone com pletely un no ticed. The stud ies list ingfau nas, some times with num ber of in di vid u als of par tic u larspe cies are rare, and only ex cep tion ally a full malacologicalanal y sis has been done, ac com pa nied by palaeo eco logi cal

and palaeo geo graphi cal re con struc tion based on such data.There are rather few more gen eral stud ies na ture, pre sent ingchanges and evo lu tion of mol lus can as sem blages over largerar eas (S. W. Alexandrowicz, 1989; W. P. Alexandrowicz,1999, 2007).

MA TE RIAL AND METHOD

In or der to de scribe the prop er ties of changes in se -quences of mol lus can as sem blages and to carry out re con -struc tion of the evo lu tion of sed i men tary in lake car bon atesed i ments, 91 sites were se lected. Ad di tion ally, the data from 32 sites with frag men tary malacological data were used aswell as those from 31 sites de scribed in the early 20th cen turyby Ger man ge ol o gists. This last group of sites can be treatedas a sup ple ment only, as they con tain very gen eral data, andlo ca tions of most of these sites can not be prac ti cally iden ti -fied at pres ent. Ow ing to this large num ber of sites, how ever,it was pos si ble to char ac ter ise par tic u lar types of as sem -blages of the fauna as well as their com po si tions and struc -tures. Re sults of these stud ies were pub lished in a num ber ofsci en tific ar ti cles (e.g. S. W. Alexandrowicz, 1989; W. P.Alexandrowicz, 1999, 2007). The study pre sented here rep -re sents an at tempt to gen er al ise re sults of stud ies com pletedat var i ous sites and to pres ent char ac ter is tics of main fau-nistic as sem blages and their re la tion ship with cli mate chan-ges and evo lu tion of wa ter bod ies dur ing Late Gla cial andHo lo cene. The most im por tant sites which pro vided the ba sisfor the pre sented anal y sis are com piled (Ta ble 1, Fig. 1).

On the sites of lac us trine chalk and cal car e ous gyttja(Ta ble 1), rich and di ver si fied malacofauna was iden ti fied.The hab i tat and cli ma tic re quire ments of par tic u lar spe cieswere dis cussed in de tail in many pub li ca tions. Sev eral pa pers

6 W. P. ALEXANDROWICZ

Fig. 1. Lo cal iza tion of mol lusc-bear ing cal car e ous lake sed i ments in North ern Po land. For ex pla na tions of num bers of lo cal i ties (1–91)see Ta ble 1.

LATE GLA CIAL AND HO LO CENE MOL LUS CAN AS SEM BLAGES 7

No Lo cal ity Ref er ences

1 NiechorzeKopczyñska-Lamparska et al. (1984);S.W. Alexandrowicz (1989)

2 D¹bki S.W. Alexandrowicz (1991)

3 UstkaBrodniewicz (1979); S.W. Alexandrowicz et al. (1989, 1990); S.W. Alexandrowicz(1998); Wojciechowski (2012)

4 Podd¹bieKrzyszkowski et al. (1998); S.W.Alexandrowicz (1999b)

5 Kluki Wojciechowski (1995, 2011); S.W.Alexandrowicz (1999b)6 Jezioro £ebsko

7 Karwia S.W. Alexandrowicz (1999b)

8 Skowarcz W.P. Alexandrowicz (1999, 2002, 2005)

9 Chojna Czepiec (1998)

10 Brzesko Kowalkowski and Berger (1966)

11 P³oñ S.W. Alexandrowicz (1989)

12 OkrzeszyceKowalkowski and Berger (1971/72)

13 ¯abów

14 ZelewoS.W. Alexandrowicz (1989)

15 Lubiatowo

16 Osiek S.W. Alexandrowicz (1980, 1989)

17 ProstyniaS.W. Alexandrowicz (1980); S.W.Alexandrowicz and Tchórzewska (1981)

18 ZdbiceS.W. Alexandrowicz and Tchórzewska(1981)

19 Zacisze S.W. Alexandrowicz (1989)

20 MarcelinS.W. Alexandrowicz and Tchórzewska(1981)

21 Jezioro Du¿e G³uche

Nowaczyk et al. (1999); Nowaczyk andS.W. Alexandrowicz (2008)

22 Jezioro Ma³e G³uche

23 Jezioro Charzykowskie

24 Jezioro Ostrowite

25 Grabowo

S.W. Alexandrowicz and Tchórzewska(1981); Filonowicz and Krzymiñska(1989); S.W. Alexandrowicz (1995b,1999b)

26 S³upsk S³owiañska

S.W. Alexandrowicz et al. (1989, 1990)

27 S³upsk Rac³awicka

28 S³upsk Po³udnie

29 Sto¿ek GlaŸny

30 Dêbica Kaszubska

31 Ga³êŸnia Ma³a

32 BorzytuchomS.W. Alexandrowicz and Tchórzewska(1981)

33 Jezioro Jasieñ

Florek et al. (1999)34 Kozin

35 Zawiaty

36 Orle S.W. Alexandrowicz (1988, 1999b)

37 Dol ina Wierzycy B³aszkiewicz and Krzymiñska (1992)

38 Nowe Polaszki S.W. Alexandrowicz (1989)

39 SulêczynoS.W. Alexandrowicz, Tchórzewska(1981)

40 Siwia³ka S.W. Alexandrowicz (1989)

41 £ubianaS.W. Alexandrowicz, Tchórzewska(1981)

42 Fordon Skompski (1961)

43 Lubicz Urbañski (1952)

44 MalinowoS.W. Alexandrowicz (1989)

45 Florczaki

46 ¯uchowo Urbañski (1957)

47 Kurzêtnik Brodniewicz (1966)

48 WorytyD¹browski ed. (1981);W.P. Alexandrowicz (1999)

49 T³okowo W.P. Alexandrowicz (1999)

50 Bez³awki Œwierczyñski (1958)

51 Szestno Skompski (1996)

52 RudkowoS.W. Alexandrowicz (1989)

53 So³dany

54 Kruklin Stasiak (1963); Czepiec (1997)

55 Kulwasy ¯urek and Dziêczkowski (1971)

56 Jezioro G³êbokie W.P. Alexandrowicz (1999)

57 Jezioro Wigry W.P. Alexandrowicz (2000, 2009)

58 Jezioro Gajlik W.P. Alexandrowicz and ¯urek (2010)

59 Kurowo S.W. Alexandrowicz and ¯urek (2005)

60 Zaczopki W.P. Alexandrowicz and Kusznerczuk(2012)61 Woroblin

62 Radzików Dobrowolski et al. (2012)

63 Olszewickie B³oto S.W. Alexandrowicz (1983b)

64 CisoweS.W. Alexandrowicz and ¯urek (1998)

65 ZamoϾ

66 G³owina Brykczyñski and Skompski (1979)

67 Os³onkiS.W. Alexandrowicz (2005, 2008)

68 Zabór

69 PomorskoS.W. Alexandrowicz (1980); S.W.Alexandrowicz and Nowaczyk (1982)

70 Szumi¹caS.W. Alexandrowicz (1980)

71 Zacisze

72 Kie³kowo S.W. Alexandrowicz and ¯urek (1991)

73 Niepruszewo-Cieœle Apolinarska and Ciszewska (2006)

74 Bogdanowo Skompski (1994)

75 Miêtkowo Kasprzak and Berger (1978)

76 Oz BudzyñskiDziêczkowski (1982)

77 Smuszewo

78 Jezioro BninWojciechowski (1999, 2000)

79 Jezioro Jeziory Wielkie

80 Jezioro KurnickieWojciechowski (1999, 2000)

81 Jezioro Raczyñskie

82 Imio³kiApolinarska and Ciszewska (2006)

83 Rybitwy

84 JóŸwin Ciszewska (1996)

85 Krucz

Dembiñska (1924)

86 Chodzie¿

87 Strzelce

88 Byszkowice

89 Szarlej

90 Bytyñ

91 Bo¿ejowice Makohonienko et al. (1998)

Ta ble 1Main lo cal i ties of mol lusc-bear ing cal car e ous lake sed i ments in North ern Po land.

For lo ca tion of par tic u lar pro files see Fig. 1

were used for this re view of bi valves (Piechocki and Dy-duch-Falniowska, 1993), aquatic (Piechocki, 1979) and ter -res trial snails (Wiktor, 2004). The spe cies were clas si fiedinto eco log i cal groups de fined and de scribed in de tail byLozek (1964), S. W. Alexandrowicz (1987), and S. W. Ale-xandrowicz and W. P. Alexandrowicz (2011). The last of thecited pa pers gave also the ba sic prin ci ples for group ing spe -cies and de fin ing as sem blages. Strati graphic set ting of par -tic u lar as sem blages was de ter mined on the ba sis of theirlo ca tion in the sec tions, re sults of other pub lished stud ies and anal y ses (palynological, diatomological, and ra dio car bondat ing) as well as strati graphic char ac ter is tics of in di vid ualtaxa of molluscs (Lozek, 1964; S. W. Alexandrowicz, 1987;W. P. Alexandrowicz, 2004). In dex spe cies for par tic u lar as -sem blages rep re sent ei ther the most typ i cal forms (char ac ter -is tic of cer tain types of hab i tats or cer tain cli ma tic phases) orthe taxa oc cur ring in the high est num bers. This method for

dis tin guish ing the as sem blages was de scribed by W. P. Ale-xandrowicz (2004) and S. W. Alexandrowicz and W. P.Alexandrowicz (2011).

RE SULTS

Ow ing to the abun dant ma te rial it has been pos si ble todis tin guish faunistic as sem blages. Their struc ture and com -po si tion closely match the con di tions un der which the de po -si tion of sed i ments fill ing the palaeolakes oc curred. Itshould, nev er the less, be stressed that the malacological as so -ci a tions de fined be low can be much di ver si fied. This di ver si -fi ca tion is caused by spe cific re gional con di tions as well asby var i ous lo cal fac tors. The as sem blages of molluscs iden ti -fied in Late Gla cial and Ho lo cene lake car bon ate sed i mentscan be al lo cated to one of three groups: as sem blages withpre dom i nant ter res trial spe cies, as sem blages with pre dom i -

8 W. P. ALEXANDROWICZ

Fig. 2. Eco log i cal struc ture of mol lus can as sem blages. TI . Ter res trial hab i tats: SL – shady en vi ron ments, OP – open en vi ron ments, HG –moist en vi ron ments: TII. Tem po rary bod ies of wa ter: TR – ter res trial en vi ron ments, TM – tem po rary bod ies of wa ter, LA – per ma nent bod ies of wa ter, TIII. Per ma nent bod ies of wa ter (lakes): TM – tem po rary bod ies of wa ter, LA – per ma nent bod ies of wa ter (lakes), RE – flow ing wa -ter; ex pla na tions of sym bols mol lusc as sem blages in text.

nant spe cies typ i cal of tem po rary or over grow ing wa ter bod -ies, and as sem blages with pre dom i nant spe cies typ i cal ofper ma nent, open wa ter bod ies.

As sem blages with pre dom i nant ter res trial spe cies(TR)

They are char ac ter ised by great di ver sity in both struc -ture and com po si tion. In the fill ings of palaeolakes these as -sem blages are of lit tle im por tance. They ap pear rarely andwere re corded only in some sites. Usu ally, they oc cur in thebot tom or at the top of se quences, in di cat ing the pre lim i naryor fi nal phases of lake evo lu tion.

The as sem blage with shade-lov ing spe cies (Sl) is char -ac ter ised by great spe cies di ver sity. The dom i nant group iscom posed of shade-lov ing forms, among them both for esttaxa: Dis cus ruderatus (Fér.), Cochlodina laminata (Mont.),and snails pre fer ring slightly more open hab i tats (open for -ests, brush zones) – Cepaea hortensis (Müll.), Bradybaenafruticum (Müll.). A pro por tion of forms of shaded hab i tatsusu ally reaches up to 50%. The sup ple ment ing el e ments in -clude taxa with wide eco log i cal tol er ance: Cochlicopa lub-

rica (Müll.), Euconulus fulvus (Müll.). Other eco log i calgroups usu ally oc cur in mi nor pro por tions (Fig. 2TI). Themen tioned as so ci a tion has been found in few sites only andoc curs within the sed i ments above the lake se quence, thus in -di cat ing a fi nal phase of fill ing of lake bas ins. This as so ci a -tion can be cor re lated with the pe riod from a de cline ofBo real Phase untill the pres ent (Fig. 3).

The as sem blage with Pupilla loessica (Pl) is a fauna ofvery poor spe cies com po si tion. The nom i nal taxon, Pupillamuscorum (L.) are ac com pa nied by Vallonia tenuilabris(Brown) and oc ca sion ally, by the oligothermic bi valve spe -cies of Pisidium hibernicum (West.). Such fau nas are typ i calfor a very cold gla cial cli mate and hab i tats of a po lar steppetype with many small and shal low wa ter bod ies (Fig. 2TI).Sim i lar malacocenoses are com monly re corded in loess for -ma tions wide spread through out Cen tral Eu rope (S. W. Ale-xandrowicz, 1995a; W. P. Alexandrowicz et al., 2002). Innorth ern Po land, this as sem blage was found at Kurzêtnik(Brodniewicz, 1966; W. P. Alexandrowicz, 1999, 2007), and in sed i ments un der ly ing lake for ma tions only. The as so ci a -tion with Pupilla loessica rep re sents a de clin ing part ofPleniglacial and the ear li est part of Late Gla cial (Fig. 3).

LATE GLA CIAL AND HO LO CENE MOL LUS CAN AS SEM BLAGES 9

Fig. 3. Strati graphic range of mol lus can as sem blages from cal car e ous lake sed i ments. ST. stra tig ra phy: PL – Pleniglacial, BL+OD –Older Dryas and Brlling AL – Alleröd, YD – Youn ger Dryas, PB – Preboreal Phase, BO – Bo real Phase, AT – At lan tic Phase, SB – Subboreal Phase, SA – Subatlantic Phase (sub di vi sion of Ho lo cene based on Starkel (1977)); AS. mol lus can as sem blages, TR – ter res trial hab i tats, TM– tem po rary bod ies of wa ter, LA – per ma nent bod ies of wa ter (lakes).

The as sem blage with Vallonia pulchella (Vpu) is mar-ked by a pre dom i nant pro por tion of snails of open grass landhab i tats with vari able mois ture con tents: Vallonia pulchella(Müll.), Vallonia costata (Müll.), and Pupilla muscorum (L.) (Fig. 2TI). They are sup ple mented by mesophilous taxa:Cochlicopa lubrica (Müll.), Euconulus fulvus (Müll.), andhygrophilous taxa: Succinea putris (L.), Carychium min i -mum (Müll.). At some sites, an es sen tial com po nent of theafore men tioned as so ci a tion is formed by aquatic molluscsliv ing in small and tem po rarily dis ap pear ing wa ter bod ies:Planorbis planorbis (L.), Galba truncatula (Müll.). Theshade-lov ing spe cies are prac ti cally ab sent. At many sites,the fauna with Vallonia pulchella ap pears at the top of lakede pos its, in di cat ing the phases of dis ap pear ance of wa terbod ies and their trans for ma tion into moist grass lands. Thismalacocoenosis is char ac ter is tic for mid-and late Ho lo cene(Fig. 3).

The as sem blage with mesophilous spe cies (Me) is mar-ked by pres ence of all eco log i cal groups, al though the for estand brush spe cies, and aquatic forms are of sec ond ary im por -tance (Fig. 2TI). The most im por tant, how ever, are meso-philous forms: Cochlicopa lubrica (Müll.), Euconulus fulvus(Müll.), Nesovitrea hammonis (Ström), and Ver tigo angu-stior (Jeffr.). These are sup ple mented by taxa of open: Vallo-nia pulchella (Müll.), Vallonia costata (Müll.), and of moisten vi ron ments: Succinea putris (L.). The fauna hereby de -scribed rep re sents the phases of dis ap pear ance of wa ter bod -ies and is typ i cal for the whole Ho lo cene, and it oc curspar tic u larly of ten dur ing Bo real and At lan tic Phases of theHo lo cene (Fig. 3).

The as sem blage with Ver tigo parcedentata (Vpa) is avery rare malacocoenosis, marked by pres ence of oligother-mic hygrophilous spe cies: nom i nal taxon, Ver tigo genesii(Gredl.), and mesophilous spe cies: Columella columella (G.Mart.). Also pres ent are aquatic spe cies with wide ther mal tol -er ance – Gyraulus laevis (Ald.) (Fig. 2TI). The taxa of openand shaded en vi ron ments are ab sent. This fauna rep re sents thetun dra with moist sub strate, very cold, po lar cli mate and is cor -re lated with the Pleniglacial and early Late Gla cial (Fig. 3).

The as sem blage with Perforatella bidentata (Pb) is amalacocoenosis poor in terms of spe cies com po si tion, mar-ked by pre dom i nance of nom i nal spe cies. Perforatella bi-dentata (Gmel.) is a shade-lov ing taxon, in hab it ing for ests ofal der swamp type, grow ing on wa ter logged sites (Fig. 2TI).Be sides the nom i nal spe cies, hygrophilous forms: Succineaputris (L.), Zonitoides nitidus (Müll.), and aquatic molluscsliv ing in tem po rary wa ter bod ies: Galba truncatula (Müll.),Anisus leucostomus (Mill.) are also im por tant. Re main ingeco log i cal groups are rep re sented spo rad i cally only. The as -sem blage with Perforatella bidentata is typ i cal for early Ho -lo cene, and par tic u larly for Bo real Phase (Fig. 3). Thisas so ci a tion de vel oped most of ten on shores of ma jor lakesdur ing low wa ter level pe ri ods, in sed i ments that form in sertsin gyttja and lac us trine chalk.

The as sem blage with Ver tigo genesii (Vg) is com monand, at the same time, one of the most char ac ter is tic. The spe -cies pre fer ring moist, some times wa ter logged biotopes, de -vel op ing un der cold con ti nen tal cli mate: Ver tigo genesii(Gredl.), Ver tigo geyeri (Lindh.), Columella columella (G.Mart.) and Ver tigo parcedentata (Braun.) are of pri mary im -

por tance (Fig. 2TI). The sec ond es sen tial com po nent in -cludes euryecological mesophilous forms: Euconulus fulvus(Müll.) and Nesovitrea hammonis (Ström). The as sem blagecan be sup ple mented by oligothermic taxa char ac ter is tic forshaded hab i tats: Semilimax kotulae (West.) and Arianta ar-bustorum (L.). Oc cur rence of aquatic molluscs such as:Gyraulus laevis (Ald.), Pisidium obtusale lapponicum(Cless.) and Galba truncatula (Müll.) in di cates pres ence ofsmall, much over grown or tem po rary wa ter bod ies. Themalacocoenosis with Ver tigo genesii is in dic a tive of cold cli -mate and dom i na tion of moist, usu ally open hab i tats of tun -dra type, and is char ac ter is tic for Late Gla cial, and par-ticularly the Youn ger Dryas. The up per limit of its oc cur -rence is marked by the phase of rapid warm ing, man i fested in the Preboreal Phase of the Ho lo cene (Fig. 3).

The as so ci a tions of sim i lar com po si tions were de scribed in many sec tions of ge net i cally di verse sed i ments through out Eu rope (e.g. Lozek, 1964; S. W. Alexandrowicz, 1987;Limondin-Lozouet, 1992; Krolopp and Sümegi, 1993; S. W.Alexandrowicz and W. P. Alexandrowicz, 1995; W. P.Alexandrowicz, 1997, 1999, 2004).

As sem blages with pre dom i nant spe cies typ i cal fortem po rary or over grow ing wa ter bod ies (TM)

The as sem blage with Valvata cristata (Vcr) is a rich anddi ver si fied malacocoenosis in which two groups of aquaticmolluscs pre dom i nate. The first, and usu ally more nu mer ousgroup con sists of spe cies that are typ i cal for shal low, smalland much over grown wa ter bod ies: Valvata cristata (Müll.),Valvata macrostoma (Mörch), Acroloxus lacustris (L.), andother spe cies. The sec ond group in cludes forms char ac ter is -tic for tem po rarily dis ap pear ing wa ter bod ies: Galba trunca-tula (Müll.) and Anisus leucostomus (Mill.). There are of tenalso euryecological aquatic molluscs: Pisidium casertanum(Poli.), Ra dix baltica (L.), and even rheophilous taxa asPisidium amnicum (Müll.). The ad mix ture of ter res trial spe -cies, chiefly hygrophilous, is usu ally fairly sig nif i cant. Moreopen biotopes are in di cated by oc cur rence of Succinea putris(L.) and Zonitoides nitidus (Müll.) while in more shaded hab -i tats, mesophilous spe cies are com mon: Ver tigo angustior(Jeffr.) and Ver tigo substriata (Jeffr.) along with forms typ i -cal of wa ter logged woods as Perforatella bidentata (Gmel.)(Fig. 2TII). The pre sented malacocoenosis is typ i cal for abiotope with a small, shal low wa ter body, grad u ally filledwith sed i ments. The char ac ter is tic fea ture of such small lakeis an abun dant de vel op ment of veg e ta tion, com posed mostlyof im mersed plants. The com po si tion of ter res trial fauna ac -com pa ny ing the aquatic spe cies de pends closely on fea turesof the en vi ron ment sur round ing the wa ter body. The malaco-coenosis is com posed of spe cies with great ther mal tol er anceand can appear in various climatic stages of the Holocene,and even in the Late Glacial sediments (Fig. 3).

The as sem blage with Pisidium stewarti (Pst) is in di cated by dom i nance of bi valves. Along with the nom i nal spe cies,there are also: Pisidium lilljeborgii (Cless.), Pisidium obtu-sale lapponicum (Cless.), and some times Pisidium hiber-nicum (West.). Snails are rep re sented by oligothermic aqua-tic forms as Gyraulus laevis (Ald.) as well as by hygrophilous spe cies: Ver tigo genesii (Gredl.) and Ver tigo geyeri (Lindh.).

10 W. P. ALEXANDROWICZ

This fauna de vel oped in shal low and in ten sively over grown,per ma nent lakes (Fig. 2TII). It is char ac ter is tic of cold cli mate andcorresponds to the Late Glacial (Fig. 3).

The as sem blage with Pisidium obtusale lapponicum(Pol) is a malacocoenosis poor in spe cies com po si tion, con -sist ing chiefly of aquatic spe cies, among which the forms liv -ing in small, very shal low, in ten sively over grown and tem-porarily dis ap pear ing wa ter bod ies, typ i cal for a cold cli mate. Apart from the nom i nal taxon, there are also oligothermicforms: Pisidium lilljeborgii (Cless.) and Pisidium stewarti(Pat.) as well as spe cies of wide ther mal tol er ance: Galbatruncatula (Müll.) and Ra dix baltica (L.). Ter res trial spe ciesare few and they are most of ten rep re sented by hygrophilousand oligothermic snails as Ver tigo genesii (Gredl.) (Fig.2TII). This malacocoenosis is typ i cal of Late Gla cial, par tic u -larly of the Youn ger Dryas. It also oc curs rarely at the be gin -ning of the Ho lo cene. It does not ap pear in its ypunger part,starting from the Boreal Phase (Fig. 3).

The as sem blage with Gyraulus laevis (Gl) is char ac ter -ised for its abun dant oc cur rence of oligothermic aquaticsnails. Apart from the most char ac ter is tic nom i nal taxon,there are also Pisidium obtusale lapponicum (Cless.) as wellas other spe cies of wide ther mal tol er ance such as: Ra dixbalthica (L.), Galba truncatula (Müll.) and oth ers. The ter -res trial fauna with prev a lence of oligothermic spe cies: Ver -tigo genesii (Gredl.), Ver tigo geyeri (Lindh.) and mesophi-lous spe cies usu ally ap pears as ad mix ture, al though even upto 40% (Fig. 2TII). This as sem blage is char ac ter is tic forsmall, shal low but not dry ing lakes of a cold cli mate. The as -sem blage with Gyraulus laevis is char ac ter is tic for warmerphases of the Late Gla cial or the be gin ning of the Ho lo cene.In the up per part of the Ho lo cene, the nom i nal species occursextraordinarily rarely (Fig. 3).

As sem blages with pre dom i nant of spe cies typ i calfor per ma nent open wa ter bod ies (LA)

The as sem blage with Lymneaidae (Ly) is a rich and di -ver si fied malacocoenosis, con sist ing chiefly of aquatic spe -cies of wide eco log i cal tol er ance, in hab it ing per ma nentwa ter bod ies: Ra dix baltica (L.), Stagnicola turricula (Held), Stagnicola palustris (Müll.), Pisidium casertanum (Poli.),and many other spe cies. Forms typ i cal of small wa ter bod ies:Acroloxus lacustris (L.), Gyraulus albus (Müll.), and some -times even forms typ i cal for tem po rarily dry ing zones: Galba truncatula (Müll.) ap pear as ad mix ture. Ter res trial spe ciesare ei ther ab sent or ap pear only as sin gle shells (Fig. 2TIII).The com po si tion and struc ture of this as so ci a tion are veryvari able and de pend closely on na ture of the wa ter body. Theas sem blage with Lymnaeidae de vel ops dur ing the whole Ho -lo cene, both in small, shal low and in ten sively over grownlakes and in larger lakes of different trophism (Fig. 3).

The as sem blage with Bithynia tentaculata (Bt) is one ofthe most char ac ter is tic and most com monly oc cur ring as so ci -a tions in lake car bon ate sed i ments. In this malacocoenosis,the most im por tant spe cies is Bithynia tentaculata (L.) whichis some times ac com pa nied by nu mer ous forms char ac ter is tic for per ma nent wa ter bod ies (Fig. 2TIII). The fauna withBithynia tentaculata is typ i cal for semi-open lakes, partlyover grown with reeds. There are 2 types of it. The first one is

char ac ter ized by pre dom i nance of opercula over shells and isin dic a tive of pres ence of com pact reeds. The sec ond type in -di cates prev a lence of shell over opercula and cor re sponds tothe lit to ral zone of the lake (Steenberg, 1917; S. W. Alexan-drowicz, 1999a). The ad mix ture of ter res trial fauna is usu ally mi nor. This as sem blage is of ten found in early and mid-Ho -lo cene de pos its. It occurs only occasionally in the LateGlacial formations (Fig. 3).

The as sem blage with Valvata piscinalis (Vpi) has a poorcom po si tion in di cated by pre dom i nance of nom i nal spe cies,ac com pa nied by euryecological bi valves: Pisidium caserta-num (Poli.), Pisidium subtruncatum (Malm), and snails –Bithynia tentaculata (L.) (both shells and opercula). Ter res -trial spe cies are prac ti cally ab sent (Fig. 2TIII). This as so ci a -tion usu ally de vel ops in deeper parts of the lakes, on a muddybot tom with out rooted veg e ta tion. The fauna with Valvatapiscinalis oc curs both in Late Gla cial and Ho lo cene sed i -ments. In the lat ter case, it is usu ally more di ver si fied in itsspecies composition (Fig. 3).

The as sem blage with Pisidium milium (Pm) is pre dom i -nated by bi valves of the Sphaeridae fam ily. Apart from thenom i nal taxon, the most fre quently are: Pisidium casertanum(Poli.), Pisidium subtruncatum (Malm), and Sphaerium cor-neum (L.) as well as Pisidium henslowanum (Shep.) andPisidium supinum (A. Schmidt). Warmer phases are in di -cated by pres ence of Pisidium moitessierianum (Pal.). Aqua-tic snails are more rare and are rep re sented by lake forms:Bithynia tentaculata (L.) and Stagnicola turricula (Held),while ter res trial spe cies are ab sent (Fig. 2TIII). This as sem -blage is typ i cal of open lake wa ter bod ies where it lives in thezones char ac ter ized by poor veg e ta tion, both above the wa tersur face and im mersed. The malacocoenosis with Pisidiummilium oc curs ex clu sively in the Ho lo cene sed i ments (Fig. 3).

The as sem blage with Pisidium nitidum (Pn) is in di catedby ma jor pro por tion of bi valves among which a ma jor role isplayed by Pisidium nitidum (Jen.), Pisidium amnicum(Müll.), Pisidium casertanum (Poli.) and Pisidium subtrun-catum (Malm). Aquatic snails are rare while the ad mix ture ofter res trial forms does not ex ceed 20% (Fig. 2TIII). Thismalacocoenosis is dis tinct for its large con tents of spe ciesthat re quire run ning wa ter. Such fauna de vel ops in low landrivers with slow cur rent, or in bot tom parts of large lakes, inthe zones in which the cur rents oc cur. The as sem blage withPisidium nitidum was found in the sed i ments al lo cated toLate Gla cial, and to early and mid-Holocene (Fig. 3).

The as sem blage with Dreissena polymorpha (Dp) is pre -dom i nated by the nom i nal spe cies up to 95%. This as sem -blage oc curs in lakes, char ac ter is tic for its dif fer ent na tureand tro phy. The nom i nal spe cies is re mark ably euryecolo-gical, but it pre fers par tic u larly to colo nise hard sur facezones (cob bles, shells of large bi valves as Unio or Anodontagen era, anthropogenic hydrotechnical struc tures) where itde vel ops huge pop u la tions (Stañczykowska, 1977) (Fig.2TIII). Pres ence of Dreissena polymorpha (Pall.) in the sed i -ments in di cates their young age. This form was in tro ducedac ci den tally into Po land and has been re corded there sincethe be gin ning of the 19th cen tury (W.P. Alexandrowicz andS.W. Alexandrowicz, 2010) (Fig. 3).

The as sem blage with Potamopyrgus antipodarum (Pa)forms a poor as so ci a tion, pre dom i nated by the nom i nal spe -

LATE GLA CIAL AND HO LO CENE MOL LUS CAN AS SEM BLAGES 11

cies, ac com pa nied by other aquatic forms typ i cal for lakes:Ra dix baltica (L.), Stagnicola turricula (Held), Bithyniatentaculata (L.), as well as spe cies typ i cal for tem po rarilydried-up zones as Galba truncatula (Müll.) (Fig. 2TIII).Potamopyrgus antipodarum (Gray) is a young im mi grant,re corded in Po land since 1933 (W.P. Alexandrowicz andS.W. Alexandrowicz, 2010) and it is there fore a good ageindicator (Fig. 3).

DIS CUS SION

The mol lusc as sem blages de velop in def i nite hab i tats.Their na ture de pends on two prin ci pal fac tors. The first one is cli mate which de ter mines geo log i cal pro cesses and liv ingcon di tions in a re gional scale. Within the most re cent 15 000years, two pe ri ods, ut terly dif fer ent from the view point of cli -ma tic con di tions, can be dis tin guished. The older pe riod cov -ers a ter mi na tion of the last gla ci ation i.e. the Late Gla cial. Itwas a cold phase with two warmer fluc tu a tions (BÝlling andAlleröd) which were only very weakly in di cated in malaco-log i cal suc ces sions of car bon ate lake sed i ments. This pe riodwas as so ci ated with pro gress ing deglaciation, when mas sivemelt ing of dead ice blocks led to the emer gence of lakes andswamps. The youn ger pe riod cor re sponds with the Ho lo cenewhen sev eral colder stages are oc curred, sep a rated by war-mer fluc tu a tions. The Ho lo cene is not only rep re sented byde vel op ing lakes but, in many cases, also by their over grow -ing, shallowing and grad ual dis ap pear ance (e.g. Starkel,1977; Ralska-Jasiewiczowa and Starkel, 1988; Ralska-Jasiewiczowa, 1989; Birks and Birks, 1989).

Lo cal con di tions are the sec ond prin ci pal fac tor that de -ter mines de vel op ment and vari abil ity of malacocoenoses.Great di ver sity of hab i tats can re sult in oc cur rence of ut terlydif fer ent faunistic as sem blages in sed i ments of the same age.The Late Gla cial is as so ci ated with oc cur rence of rel a tivelypoor malacoenoses. These are char ac ter ised by sig nif i cantpro por tion of oligothermic spe cies and forms of wide eco -log i cal tol er ance as well as with oc cur rence of high num bersof molluscs liv ing in shal low wa ter bod ies, boggy zones andopen ter res trial hab i tats. The fau nas of the Ho lo cene are usu -ally more di ver si fied and in clude also spe cies with high eco -log i cal re quire ments. The taxa as so ci ated with large waterbodies and shaded terrestrial habitats are also common.

It is pos si ble to dis tin guish three types of malacologicalsuc ces sions in the ana lysed ma te rial, in di cat ing di ver si fi ca -tion of hab i tats and strati graphic se quences of fauna as sem -blages. These anal y ses of such se quences were at temptedonly rarely (S. W. Alexandrowicz, 1983a; W. P. Alexan-drowicz, 1997, 2004), al though they pro vide am ple groundsfor in ter pre ta tions and re con struc tions of palaeoenviron-ments as well as their changes in time.

Type A is in di cated by dom i na tion of as sem blages withma jor pro por tion of ter res trial molluscs. They are rare unlake de pos its, but much more of ten in cal car e ous tufas innorth ern Po land (Skompski, 1961; Brykczyñski and Skomp-ski, 1979) as well as in the south (W. P. Alexandrowicz,2004). The se quence starts with a malacocoenosis pre dom i -nated by oligothermic ter res trial spe cies pre fer ring open hab -i tats (as sem blage with Pupilla loessica). In the fi nal part ofthe Late Gla cial, the hygrophilous as sem blages (chiefly the

fauna with Ver tigo genesii) be came in creas ingly im por tantas well as as so ci a tions typ i cal for small, shal low and denselyover grown wa ter bod ies (as sem blage with Pisidium stewartiand with Pisidium obtusale lapponicum). Start ing from theearly Ho lo cene, the pro por tion of aquatic and swamp taxade clines grad u ally and shadow-lov ing, open-country andmesophilous snails take over (Fig. 4).

The afore men tioned se quence is a re cord of evo lu tion ofsmall wa ter bod ies which emerged at the end of the Late Gla -cial as an ef fect of melt ing of small dead ice blocks. Smalland shal low lakes were rap idly filled with sed i ments andtrans formed into swamps. Such trans for ma tion took placedur ing the Youn ger Dryas or dur ing the early Ho lo cene.From the be gin ning of the At lan tic Phase, pro gres sive dry ing and re place ment of moist swampy hab i tats by drier grass land and/or forest habitats occurred (Fig. 4).

Type B is the most fre quent one of the malacofauna as -sem blage in car bon ate lake sed i ments (W.P. Alexandrowicz, 1999, 2007). This se quence be gins with a phase pre dom i -nated by open ter res trial hab i tats of tun dra type. Char ac ter is -tic fea tures of this in ter val in clude oc cur rence of oligother-mic as sem blages with Pupilla loessica (on drier sites) or with Ver tigo parcedentata (moist and wa ter logged biotopes). Inyoun ger Late Gla cial, a phase of peat bog de vel op ment iscom monly ob served. Pres ence of char ac ter is tic malacoco-enosis with Ver tigo genesii is linked to this pe riod. In wa ter -logged ar eas, there were small, shal low and much over grown melt-out lakes, in hab ited by as so ci a tions with Pisidium ste-warti and Pisidium obtusale lapponicum. Pro gres sive melt -ing of large dead ice blocks dur ing the Youn ger Dryas and atthe be gin ning of the Ho lo cene led to trans for ma tion of thesehab i tats into ma jor lakes. This stage is as so ci ated with oc cur -rence of rich as sem blages of aquatic molluscs, par tic u larlywith Bithynia tentaculata. It is also a stage of in ten sive ac cu -mu la tion of car bon ate sed i ments, a thick ness of which mayeven ex ceed 10 m. Lac us trine chalk and cal car e ous gyttjagrad u ally filled lake bas ins, lead ing to their dis ap pear ance.The fi nal stage of fill ing of the lakes re sulted in their trans for -ma tion into peat bogs. This is con firmed by pres ence of peatlay ers over ly ing the car bon ate sed i ments. The mol lus cancom mu ni ties show also ev i dent changes. The as sem blageswith prev a lence of spe cies typ i cal of lakes are re placed by as -so ci a tions dom i nated by taxa of shal low and in ten sivelyover grown, some times even ep i sodic wa ter bod ies (as sem -blage with Valvata cristata). In the late Ho lo cene, these wa -ter logged zones were trans formed into ter res trial hab i tats,ei ther open (as sem blage with Vallonia pulchella) or shaded(assemblage with shadow-loving species) (Fig. 4).

Type C suc ces sion is char ac ter is tic for large lakes. These wa ter bod ies de vel oped from ex ten sive cave-in lakes, re sult -ing from melt ing dead ice blocks and formed as late as in theLate Gla cial. This stage is as so ci ated with oc cur rence of as -sem blages with mi nor pro por tion of ter res trial spe cies e.g.fauna with Valvata piscinalis. A dom i na tion of aquatic mol-luscs main tains through out the whole Ho lo cene. The chan-ges of wa ter level in lakes (Ralska-Jasiewiczowa and Starkel, 1988; Wojciechowski, 1999, 2000) were marked by pe ri odicoc cur rence of as sem blages with greater pro por tions of taxatyp i cal of shal low wa ter bod ies (as sem blage with Valvatacristata) or even wa ter logged ter res trial hab i tats (as sem -

12 W. P. ALEXANDROWICZ

blage with Perforatella bidentata). In the top part of the se -quence of lake sed i ments, the as sem blages with Potamo-pyrgus antipodarum and with Dreissena polymorpha occurand indicate a human impact (Fig. 4).

CON CLU SIONS

On the ba sis of the anal y sis of fea tures and se quencesper tain ing to mol lus can as sem blages oc cur ring in lac us trinechalk and calcarous gyttja, it was pos si ble to com pile thescheme of evo lu tion of lake wa ter bod ies. The old est mol lus -can as sem blages doc u ment the pre-lac us trine ter res trialphase, cor re spond ing to the end of Pleniglacial, and withearly Late Gla cial. The malacoenoses in di cate pres ence ofopen hab i tats with vary ing mois ture lev els, from dry Arc tic

steppe-like hab i tats to moist and wa ter logged tun dra bio-topes. The first stage of lake de vel op ment is con nected with a warm ing of the Alleröd Interphase. Mas sive melt ing of deadice blocks led to emer gence of nu mer ous melt-out lakes (e.g.W. P. Alexandrowicz, 1999, 2007; Wojciechowski, 1999,2000). Thus ex ten sive but shal low and in ten sively over -grow ing wa ter bod ies were in hab ited by rel a tively poor mol -lus can as sem blages with pre dom i nant oligothermic spe cies.Dur ing the Youn ger Dryas, many of these wa ter bod ies werecom pletely filled with sed i ments and trans formed into peatbogs. A char ac ter is tic as sem blage with Ver tigo genesii re -garded as in di ca tor of the afore men tioned phase is as so ci ated with these hab i tats (Lozek, 1964; S. W. Alexandrowicz,1987; Limondin-Lozouet, 1992; Krolopp and Sümegi, 1993;S. W. Alexandrowicz and W. P. Alexandrowicz, 1995; W. P.

LATE GLA CIAL AND HO LO CENE MOL LUS CAN AS SEM BLAGES 13

Fig. 4. Suc ces sions of mol lus can as sem blages from lake sed i ments in North Po land. A-type, B-type, C-type – suc ces sions of as sem blagesde scribed in text: PL – Pleniglacial, LG – Late Gla cial, EH – Early Ho lo cene, MH – Mid dle Ho lo cene, LH – Late Ho lo cene, TR – ter res trialen vi ron ments, HG – moist en vi ron ments, TM – tem po rary bod ies of wa ter, LA – per ma nent bod ies of wa ter (lakes).

Alexandrowicz, 1997, 1999, 2004). On the other hand, how -ever, the de clin ing pe riod of the Late Gla cial was in di catedby ris ing wa ter lev els in lakes. This phe nom e non, ob servedin al most en tire north ern Po land (Wojciechowski, 1999,2000) can be con nected with grad u ally moister cli mate. Ow -ing to that, many melt-out lakes were trans formed into largerand deeper lakes, in which car bon ate de po si tion was ini ti -

ated. A be gin ning of the Ho lo cene was in di cated by rapidwarm ing that de ter mined a sub se quent stage of lake wa terbod ies. De creas ing pre cip i ta tion re sulted in a drop of wa terlevel in lakes (Ralska-Jasiewiczowa and Starkel, 1988; Woj-ciechowski, 1999, 2000). This fact, in com bi na tion withgrad ual fill ings of lake bas ins with sed i ments re sulted in dis -ap pear ance of many shal low lakes and in peat bogs emerg ing

14 W. P. ALEXANDROWICZ

Fig. 5. Fig. 5. Late Gla cial and Ho lo cene en vi ron men tal changes in North Po land in the light of malacological anal y sis of cal car e ous lakesed i ments. ST. stra tig ra phy: BL+OD – Older Dryas and Brlling AL – Alleröd, YD – Youn ger Dryas, PB – Preboreal Phase, BO – Bo realPhase, AT – At lan tic Phase, SB – Subboreal Phase, SA – Subatlantic Phase (sub di vi sion of Ho lo cene based on Starkel (1977)); W –high-level wa ter pe ri ods (af ter: Wojciechowski, 1999, 2000), N – low-level wa ter (af ter: Wojciechowski, 1999, 2000).

in their places. Dur ing mid- and late Ho lo cene these peatbogs were trans formed into grass land and for est biotopes.The afore men tioned drop of wa ter level were much less pro -nounced in large lakes, in which de po si tion of lac us trinechalk and cal car e ous gyttja with rich and di verse mol lus canas sem blages has been con tin ued through out early and mid-Ho lo cene. Dur ing late Ho lo cene, a re mark able slow ingdown and in many cases, dis ap pear ance of car bon ate sed i -men ta tion oc curred. Cli mate changes re flected in chang ingwa ter lev els in lakes are also com mon dur ing this pe riod(Ralska-Jasiewiczowa and Starkel, 1988; Wojciechowski,1999, 2000). Dur ing the last one hun dred years, hu man im -pact has be come more and more no tice able in the en vi ron -ment. It is marked in malacocoenoses n lake sediments eitherby impoverishment of species composition resulting fromprogressive eutrophication or by occurrence of expansivespecies alien to Polish fauna that indicate anthropogenicmigrations (Fig. 5).

Changes in mol lus can as sem blages en able dis tin guish -ing of sev eral ep i sodes of peat bog de vel op ment and dis ap -pear ance of lake wa ter bod ies. These oc curred in the decli-ning part of the Youn ger Dryas, be gin ning of the At lan ticPhase and in the Subatlantic Phase (Fig. 5). These ep i sodesev i dently co in cide with phases of lower wa ter lev els in lakes(e.g. Starkel, 1977; Ralska-Jasiewiczowa and Starkel, 1988;Wojciechowski, 1999, 2000).

Re con struc tion of the evo lu tion of lake wa ter bod ies innorth ern Po land, based on anal y sis of mol lus can as sem -blages, sup ple ments sim i lar re con struc tions and pat terns de -fined un der dif fer ent meth ods and pub lished in nu mer ousstud ies, both in Po land (e.g. Goslar et al., 1993; Starkel et al.,1996; ̄ urek and Pazdur, 1999; Wojciechowski, 1999, 2000)and in north ern Eu rope (e.g. Ma nia, 1973; Ma nia and Toe-pfer, 1973; Sunderlau, 1975; Griffiths et al., 1994; Magnyand Ruffaldi, 1995).

Ac knowl edg ments

This study has been spon sored by the AGH Uni ver sity of Sci -ence and Tech nol ogy through the Uni ver sity grant no. 11.11.140.173.

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