Sedimentological, Geochemical and Diatom

Sedimentological, Geochemical and Diatom lnvestigations on Sediments of Lake WonieśćSediments in the Context of Climate Changes and Main Stages of the Middle Obra River Settlement lwona Hildebrandt-Radke, Waldemar Spychalski & Monika LuĘńska, Poznań

lntroduction

cies towards environmental change are ob-

with using fire by humans, alterations in composition of pollen spectrum or complexes of macro- and microfossils caused by processes of cultural eutrophication, modificaLions in geochemical composition of deposits (higher percentage of trace elements and phosphorus), changes in warer level and so on (MaroHoNlENKo/NALEpKA 2007; zCŁoB|CKl zoo8).

tained thanks to many-sided research into the lacustrine sediments cores. Most often

ment in Bruszczewo (central Greater Po-

Nothing can replace lacustrine sediments as a natural archive. They enable to follow the record of environmental change and their cause on local and regional scale (Gost"ĄR 1998, GosLAR et al. 1999, WoJclEcHoWsKI 2000, Błrece et aL 2ooz, RALSKA-JASIEWICZOWA

et al, 2003, BoRóWKA

2007). Conclusions about diverse tenden-

the studies are 1ithological/sedimento-

logical, geochemical as well as palaeoecological, eg. palynological or diatom ones

(RALSKA-JASIEwlcZown et al. l998, B,łtEn et aI. 2004, TYLMAN 2005; LolTERMosER et al. ]997, TYLMAN et al. 2007, 2011). The vicinity of lakes oI, more generally,

sedimentary basins is used also by archaeology. lnvesri3arions on lacustrine or mire sediments in the surroundings ofor not far from archaeological sites prove anthro-

pogenic modifications of natural environment in various periods ofthe Holocene eg. Biskupin (NllwIARoWSKI et al. 1995), Gościąż(RALsG-JAsIEwlczowA et al. 1998), Kałdus (CHuozaK et al.2004), Woryty (CIEśLA1981, DĄBRoWSKI 1981). Such traces may occur in several configurations and with changeable intensity, de

The research on the Early Bronze settle-

land region) has been conducted since the mid 1990s. It constitutes another proof of diverse environmental effects of settlement and economic activity of people of the Ónćtice (Early Bronze) and Lusatian (Middle and Late Bronze Age) cultures as well as of the Middle Ages. Levels ofdeforestation related to earlier

mentioned settlement phases are clearly visible in local pollen diagrams taken from rhe mire, which fills the samica river

trough and surrounds the archaeological site in Bruszczewo. They show a decrease in alder, hornbeam or oak as well as an increase in indices of herbaceous plants: cereals, ruderal species and high percentage of charcoa] (HAAs,/WAHLMULLER 2004, 2010).

pending on the degree of anthropopression, forms of human activity and location of sedimentary basins towards

In the archaeological site and adjacent areas, colluvial carbon dated covers were recorded. They signify prehistoric transformations of the relief resulting from use of

economically used areas. In biogenic and lacustrine sediments it is expressed for in-

(HILDEBRANDT-RADKE 2010).

stance by an increase in the percentage of mineral components (which originate from erosion and denudation processes), higher percentages of burnt fragments connected

land for the purpose of

agriculture

Analyses of materials from the Polish Archaeological Record constitute another proof of search for settlement in this area. The scttlement maps indicare quiLe inten-

t. Hildehran(Jl Radka/W. Dtrlflc I. Czebresztlklj. Mt)ller (eds.) Anńropogcrłj PrcsJurc in the an.lLhc l3ronzc Agc on lhe Celiral Elrropedt) LUW/dnó 5A(r5Pt) s, r,.zllal) Bónn2a11,

Neo/ilhi.

79

sive population of Równina Kościńska (KościanPlain) since the Neolithic Period (JłstewIcz,/HILlesRANDT-RADKE 2009; JAsIE,

wlcz,/HII-oEsRĄNor-Rłlxr in this volume). The aim of furthet research was to determine r,t hethcr łhe anthropogenization processes ofthe Kościan Plain, observed in local palynological diagrams (eg. in the archaeological sitc in Bruszczewo) and on the setdement maps from the Polish Ar-

chaeological Record, are noticeable also on regional scale, in sediments of the biggest

water body within the examined area, which is situated 15 km to the east from BIuszczewo (CzEBRESzuK,/MULLER 2004; HAAS/WA]iLMULLER 2004; CZEBRE'ZUK/ MUu,ln 2005: CzegpBzur,/Hl],oEnnłNor RADKE 2007; Hałs,/Włrłu,łulmł20l0; H]LDEBRANfi .RADKE/SPYCHALsK],4ANCZAK-

KosTEcKA in this volume).

Research area

A. lar as

me.oregional divi"ion is con cerned, the investigated area includes, besides Dolina Środkowej Obry (Middle Obra River Valley which is a fragment of pradolina warciańsko-obrzańska Warta-Odra lce-Marginal Valley), Pojezierze Sławskie (Sławskie Lakeland), Pojezie rze Krz}łvińskie (Krzywiń Lakeland) and the lakeless kościan plain (these three units make up Pojezierze Leszczyńskie Leszno Lakeland), as rveli as a section of Wysoczyzna Leszczyńska (Leszno Upland) in its southern part (KoNonłcrt 2002) (Fig.1).

Fit], 1 Loc.ltion oi the lesearch nred with thc

formed

l97z). Rivers flowing in troughs calry theil

(KRYGoWsKl 7961,

watels to the biggest lowering in the north,

which is the Obra fragment of Pradolina Warszawsko-Berlińska (Warsaw-Berlin lceMarginal Valley), running from northern easr ło .ourhern west, This lowering is Vast, lon8itudinal with substantial width fluctuations. It originated as a westward runoff of fluvioglacial waters in the Poznań phase ofthe last glaciation. Within the analysed section, the depicted part of the icemarginal streamway is called the Middle Lake wonieść,which thc cores were rakęn lrom, is aI prcsent a §lorage rcservoir builr in period lq74 l98Z. fhę reservoir

physi.o gco8raphlca| rcglons

ńc

marginal zone was bcing

Obra River Valley.

diV]s]on ]nto (]n

into being in the course of subglacial waters activity, when the hinterland ofLeszno

hypscjmetli(: n]dP

elabor.rleLl on thc lr.rsi§ of Vm.]p LcVc12,

was created on rhe basis of 5 natural lakes,

including Lake Wonieskie, which surface area amounls to l22 ha, and the maximum depth is 14.5 m. Two cores, 20- and

,

-- -

jr, ,:..

,,]§""

surface features of the studicd area are related to the Leszno (Branderburg) phase of the Vistulian glaciation. Described area is characteristic of morainic plateaux stretching in forms of isolated uplands cut through with Val]eys as a result of the flow offluvioglacial waters during the last glaciation. Absolute elcvations vary from 60 to 135 m above s.l. (Fig. 1). Lakes ofthe Leszno Lakeland, including

Wonieść,are of gutter origin. They came

80

23-metreJong, were prepared for the study from the south-eastern part of the lake. They were taken from a drilling platform under direction ofW Dórfler's, PhD. The 23-metre long core went thlough the bottom ofthe lake, in the bed of which

the rcwashed coarse- and

mediumgrained sand deposits were found. Up till thc halfofthe profile, till the depth of8-9 m, the SedimentS are represented predom, inantly by o1ive,brown gyttias, which then

conStitute laminated deposits

(also gyttja-likc ones) with variously developed lamination; they are enriched with organic material in place 7 cxclusively occurin8 at pH > 7 no apparent optimum

(V^N D^M et al. -l99,1)

1 2 3 4

Classcs Oli8osaprobou5 Beta mesosaprobous Alpha mesosaprobous

(V^N D^M

tolcratc a Very sli8ht orsanic po|lution tolerate a mcdium organic pol|Ution

ci al, 1994)

TIophi.

Classes

.] 4 5 6

clean Water

Alpha mesoplllysaprobous heavily pollutcd

(V^N D^^1

1 2

Saprobity

o|itjotraphentic oli8o mesotraphentic Mcsotraphcntic

sLa

te

low productivity 8reater than oli8otlophic lakes, but less than mesoeutrophic lakes

moderately prodUctiVe

Meso-eutraphentic

8reater than mesotrophic lakcs, but less than eutrophic lakcs

Eutraphentic

enriched trophic statc, vcry productive

Hypereutraphentic

Vcry nutrient rich |akes characterized by lrequent and scvcre nuisance algal blooms and low transparcncy

ci al. ]994)

Sediments dating Chronological scope of the taken cores is ing the sequence ofvaryes, with occur with defined by 10 AMS ''C dates gained in intervals below 16 m to the core bottom Leibnitz Labor fi.ir Altersbestimmung und (DóRFLER, in this volume). Isotopenforschung Christian-Albrechts- An important criterion determining Universitet in Kiel on the basis of plant some chronostratigraphic framework of macroremnants found in the profiles. the Holocene was the pollen diagram comAchieved dates served to elaborate a de- position chaIacteristic of individual peritailed time model with the help of OXCAL ods (thus the division between Pre-Boreal,/ programme(BRoNKRAMsEy2008). Boreal, Sub-Borea1,/Sub-Atlantic periods The time-depth model was additionally was set) (DóRFLER, in this volume). supplemented with information concern-

Record of natural and anth]opogenic environmental transformations in the an issue of research results spatial interpretation lacustrine sediments

-

Diverse research methods concerning the It raises a question about the spatial scope same core ofsediments have been applied. ofresults interpretation.

82

t. Hildabrandl-Raclke, W. spychalski & M- LlJtyńska

Fi8. 2 Topographical water borders of drainage area:

A

direct draina8e area of Lake Wonieść, indirect drainage area of Lake Wonieść,C, D, E, dlainage areas of the samica rive. sections, includin8 draina8e area of the fos§il lake located

B

D

in a neishbourhood

ol the archeologica| excavation site in Bruszcżewo, Draina8e basins Werc appointed on the basis ofthe digita| hi8h-altitude model DETD Level 2 With MFD method in the r-steam module of the ploglamme crass cls (JAslEW|CZ

2011j l^SlEWlCZ /

MEIZ 2o11).

In case of palynological investigation, record of both regional and local environmental transformations is reflected in the pollen diagrams. Sporomorphs transported from greater distances are likely to be intercepted by huge, open water bodies. Knowledge of maximum range of scattering pol-

lens by separare plant species

is

an

important aspect of this kind ofresearch. In sedimentological, geochemical and diatom studies, interpretation of results is based on processes occurring in the lake's drainage area. The catchment is an area of the matter and element cycle, measurable outcome of which is the record in the deposit, in the water body. Another spot like that is the lake itself and the bio- and geochemical processes, that take place affecting the organic world and also are reflected

in the sediment,

The map analysis shows that direct

drainage basin of Lake Wonieśćwith the surface area of 43.47 k:n'stretches a.long

two sides of ńe lake (Fig. 2). However, its

much bigger section is situated on the

western part of the lake (closer to the archaeological site in Bruszczewo). More-

oveĘ processes occurring in

Lake

Wonieskie were affected by indirect drainage basin of the lake with the surface area of 191.ż3 km'. Lake Wonieść and lakes located souńward belong to the system of open lakes and therefore influence the sed-

imenLary and geochemical processes in Lake wonieskie. Their common surface area iS considerable enough to offer more general then local sca.le of interpretation as

far as conclusions regarding geochemical

and diatom analyses are

concerned.

Whereas, the results of sedimentological studies reflect changes observed in ńe direct drainage area and connected with natural or althropogenic rransformarions in plant cover as well as with processes ofwater and wind erosion, and ofthe catchment denudation.

Sedimentological investigation The lithological analyses, which were carried out. indicate quiLe high homogeneiry of the material taken from the lake. principally, the lacustrine sediments are made up ofsilt and clay fractions. Bedrock ofthe lac_ ustrine deposits consists ofsands and grav-

els; lithologically, they differ distinctly from the lacustrine sediments (Fig. 3). Bigger admixtures of coarse-grained

silts and fine-grained sands in the lacustrine sediments correspond with these levels of the profile which were recorded

sedimentolo9ical, Ceochemical and Diatom lnvestiiations on sediments ol Lake wonieść

crain flaćlion p.rcnlaqe (!m)

Fig, 3 llesults of 1ilh()k)gic.rl irnalysis carried out lor thc Lake Wonicśćscdimcnts,

with high indices of settlement and may prove the deforestation of the drainage

50

area. Such changes are accompanied, and sometimes anticipated by a growth in the organic matter content (increased indices

100 150

2ao

25o

300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000 ] 050

of the loss on ignition). This tendency is noticeable from ca. 750 cm up till the top

of the profile (Fig. 4). Whereas from the floor up till the half

of the profile the reverse tendency

marked i.e. lower Mz values are accompanied by an increase in LOI index. This relation might in turn be a result of a bigger role of processes happening in the lake itself. The near-bottom zone is the only ex-

1100

ception where both increase in average grain diameter and in loss on ignition indi-

1]50 12oo 125o

]300

cator were recorded. The highesr indices ofthe organic matter percentage (about 20 o/o) are characteristic of the Early Middle Ages and of the

1350 1400 1450 1500 ,l550 1600 1650

Middle Ages. These periods are known from historical sources (HtłovrowIcz 793ż), and also from palynological dia-

17oD

1750 1800

,1850

Fig, 4 corrclati(rn5 .lmolr8 .rvcrasc particle size, loss on lgnition and C.lCo, contcnt in thc invesl]gated proflle,

grams of intensive deforestation in the re-

1900 1950 2o00 2050 21oo

gion of Greater Poland

2150 2250 Mz

(HAAs

/

WAHLMULLER ż004, 201,0: DóRFLER in this

22oo

-

is

(Pm)

-Loss

on ignition

(%)

-

caco3

(%)

volume), Similar indices o[ the organic matter content, exceeding ż0 Eo, are characteristic of near bottom zone of the lake,

l. Hildebrandl Radkc,

W

Spycha/ski & M. LULyńska

Depth (cm)

,§ o"§ §

o.§ oo§ u.§ -§ §, §,

ęo^de'

§

t\,

Ir

F

l

I

§"§ \,

("§

ę§ \,

§,

H

F

|..

-l L

'L_] Fr ]r

! i. F]| ł

L] !

l 132a

I t

f-,T,T-n

GWoN4

l

although in this case, natural causes of increased mineral and organic supply should be taken into consideration. Howevel, the content of CaCO] in the analysed profile shows obvious connection neither with lithological composition ofthe lacustrine sedjments nor with Lhe organic matter content. In the vertical profile, quite even characteristics of CaCO, can be ob-

serued, which maintain high 1evel of 40 50% (Fig. 5). Dismnce from the surface till the depń ofabout 11 m (chronologically up till circa 2000 cal. BC) is characteristic of higher changeability of calcium carbonate (Fig. 3), while fiom that zone down to the bottom ofthe profile this index is observed as more stable. Apparent decline in the calcium carbonate content is visible only on the bottom ofthe lake. The source ofCaCO. in ńe lacuslrine sedimenls may be its precipiLation as a result of assimilation, irs accumulation from shells of biva.lves, snails and ostracods, or physico- chemical processes (RlnrowsKl 2007). However, Ca keeps first place in the migration row ofelemenrs what might indicare that jts source is

related to ground feeding from the lałe drainage area (BoRówM 2007). SedimentoIogical investigaLion, in com-

parison with others, was conducted with

J!

L

ł Pl;}]

fi,,*-..H

the highest distribution, (every 4 cm). Therefore, the demiled sedimentological levels (SWON) were distinguished on the basis of prime grain size parameters, loss on ignition and content of CaCO.. swoN 1 (2300-2260 cm) (< 8600-8500 BC, be, fore the Pre-Borea1 period) is a level connected with the bedrock of the lałe. This is the level, where thc lakc trough is cut out. Main fractions making up thc deposit falJ into the range of 63 1000pm,Thesearc sands ftom coarse, to fine-graincd oncs, With fine-

and medium-grajned sand as a dominant fraction

(125 500pm). The conlent ofolganic mattcl and cal, cium carbonatc was not recorded within this ]evel. swoN 2 (2260 2180 cm) (8500 8300 Bc, Pre-Boreal pcriod) includes ncar-bottom zonc of thc lake. Beginning with this level, the gyttjass occuf, up till the rool Sedjmentological ]evels Were dis n, guishcd on thc basis of mincral admjxturcs. In this case these are fine-grajned sands and coarse-graincd silt. Hi8h percentage oforganic matter as well as low contcnt of carbonates in deposits iśanotbcr charactcristic feature ofthis ]evel.

sWoN 3

Pre-Boreal

(2180 2025 cm) (8300 7400 Bc, ald Boreal periods) this level is charac-

terislic of

a

decline

in the

supply

of

morc

coalsc-grained mineral fraction and organic maller as weilas ofa significant growth in content ofcalbonates ifl sediments. High contcntofcaco. (ofcirca 50 70) is charactcristic of substantial par! of the profile. sWoN 4 (2025 1780 cm) (7400-5200 BC, Boreal and Adantic periods) a growth jn the supply of sand and silt fraction was again recorded in the fourth level; in comparison to other parts ofthe profi]e, low values ofloss on ignition as we]l as stability ofCacor were observed.

sedimentoloiical, Leochemical and Diatom /nvest8ations on sedimentJ oftake Wonle.\ć

Fill, 5 Rc§Lllt§ of geochcmical analysis of the Lakc Wonieść sediments,

sWoN

(1780 l580 cm) (5200 3700 BC, Adan,

5

Neolithic)

is typi, cal ofa dcclinc in the suPply orminera] fraclion; in thc low, I pJll or lh. lp\el. low conlent orolBa-'. lTżll, l is maintained with lhe tcndcncy to grow in the second part of thc lcvcl and With smal] flucluation ofcaco, (!iny decrcasc in the index in the lowcr part of thc Lic

period,

ahe

Mesolitbicand the

lcvcl).

sWoN 6 (1580 1475 cm) (3700-3100 Bc,

Sub Boreal period, thc Ncolithic) thc sixth level is chaIacleIistic ofan incrcasc in thć supP]y ofsand and §ill mdll. iJl: di.llncl l U.ll J1,on of lne lo.. on l8n' lion indicator and stabiliiy ofCaco. With a small lendency

Lo

grow are markcd,

SWON

7

(l475 1360 cm) (3100-2600BC, od, lhc Nco|ilhi.) ir.on pJri.or lo

SUb Borenl pPr the former, a decline in thc supPly of mineral malrcr was noticcd in this ]cvcl as Wcll as conslant instability ofthe loss on ignition Valucs accomPanicd by stability of the carbonates contcnt index. (1360 1255 cm) (2600 2000 BC, SWON Sub,Borea1 period, thc Ncolithic) thc cighth lcvcl is rypicalofi mosr lolal lack ofminefalsupply, whclcas thc pcrcenLage of organjc matter incrcascs in this 1evel, despite its considcrab]c fluctuation; contcnt of caco, maintains its stability.

8

swoN 9

(1255 1060 cm) (2000 t050 BC,

Sub,Borcal pcriod, thc Nco]ithic, thc

BronzeA8e)

a

growth in the supPly of mineral mattcr is markcd twice in the ninth levcl and divided by the period of dcclinc; tcndcncics to stablć thc organic matter as well as much higher changeability of CaCo, with an increasing lendency lo thc loofare manifested hcre. sWoN l0 (1060 940 cm) (l050 800 BC, Sub-Boreal pcriod, the Bfonze Age, Hallstatt) is characleristic ofa decline in the supply ofmineral mattcr, stability of loss on ignjtion valucs and high bur gainin8 stability jndjces ofCaCo,. SWoN l1 (940 830 cm) (800 400 BC, sub,Borcal and Sub,Atlantic Pcriods, ] Iallslalr) ,- downward

tcndencies of calcium carbona!c contćnt accompanied by hi8h lluctuation ofthis indcx, poor supply ofsand dnd du.l i., l ion, d. Wcl' d. "l.blllly orol!,d n i( m"l.er conlent ale marked in thc clcvcnth ]cvcl. SWoN 12 (830 680 cnr) (400 BC 0, sub-Atlantic period, thc La '1'ćnc Pcriod) is typical of a gradual in

crcasc in the supply of mincral matter, of a growth in loss on isnition content and of downward tendcncics

ofCacor sWoN

13 (680, 510cm) (0 450 AD, sub-Atlantic pcriod, thc Roman Iron Age and partia]ly rhe Migration Period) is charactcrizcd by instabilily in thc suP ply ofmineral mattcr (fa]l, growth and anothcrdcclinc jn thc indcx); lluctualion of loss on jgnition and upWard tendencics ofcaco. also occur sWoN 14 (5l0 4l5 cm) (450 600 AD, sub-At]antic pcriod, the Migration Period) is markcd by lack ofthe sUpply ofmjncral matter, low indices ofLhe supply ofor8anic mattcr and a dcc]ine in the caco, con

tcnt,

SWON t5 (4I5 265cm) (600-1200 AD, sub,At-

lanr'c perlod. lhe E.ll,V Middlc Ątc.j i. chaldCleri"lic ofhi8h and Llnstable growth ofmineral supply to thc ldłP, LlPWJrd le ,J.-Cic. ol lh. .Upplv ololEanic -n"l tel as well as considerable fluctuation or Lhe caco,

SWoN ]6 (265 0 cm) (1200 2001 AD, Sub-Atlantic period, from the Middle Agcs to thc conLempo rary substantial mineral supply i§ maintained

cra)

with downward lcndcncics to thc roo| which is accompanied by high index ofloss on ignition and high changcability of CaCo, (increasc, decrease, and another 8rowth in thc contcnt ofcarbonatcs in sedimenl to the roo0.

In the whole analysed profile, the high, est pelcentage of mineral deposits is characteristicof SWON levels: ż, 4,b,7,9, l2, 13, 15 and 16. From the Hallstatt, that is from the beginning of the Sub-Atlantic pe,

riod, levels with increased mineral supply (SWoN levels 12 16) correlate with settlement levels and with levels ofhigher indices of loss on ignidon, This correspondence is not so distinct in case of older leve]s what might signify stronger influence of climate condition on denudation in the calchment area and sedimentation in the Water body.

Ceochemical investigation Geochemical analysis of representative and

trace clements was another

applied

method. Substantial diversification of elements is connected with the increased supply of organic matteĘ with enlichment in analysed elements of ground Waters, and, in addition, with changing chemical conditioning in the water body. These conditions

may favour the precipitation of trace elements in the form of sparingly soluble compounds (Fi8. 5). 9 local geochemical levels (GWON) were distinguished.

CWoN

l

(l552 1490cn) (3800

3200 BC, thc this lcvel is typicai ofhigh conLent olMn, Fe, Cr, Ni, and Na as Wcll as ofincrcasjng

Middle Neolithic) valucs of Ca,

GWoN2

(]490 1220cm) (3200 2000Bc,.hc

Middle

Neolithic)

growth

ofca culvc

the decliIc ofCr, stability ofthe Ni culvc, downward Lendencic§ of Fe and Mn, qltitc high percentage of P as wcll as decreasc rnd rhen

GWON3

can be obscrvcd in this ]eve].

(1220 1030cm) (2000 1000BC,lhe Middle Neolilhic, thc Latc Neolithic, the Early and Middle Bronzc

Age)

is charactcriued by high index

ofCr, stability of Ni, hi8h and stablc

va]Llcs

ofMn and

dcclinc in Ę and towards lhe cnd increasc in Ca, GWON 4 (1030 780 cm) (1000 300 BC, the LaLc Bronze Age and Hallstatt) Zinc appcars in lhc leve]. the valucs ofcr arc maintained with lhc downward Lendency towards thc cnd of the distinguished Fe,

1, HildabrandL-Radkc, W. spycha/ski &

M, Lrrty/jsła

1 , Statistical characleristics of results of the Lake Wonieśćsedimcnt analyses and geochemical background (n 5D - standard deviation).

Table

cU (m,r/kg)

Zn Cr Cd co Ni Pb Mn (mg/kg) (mg/kg) (m/kg) (m8/k&) (mglkg) (m/kg) (m/kg)

,l9:,

n

Arithmetic

11

mean

ccomcthric mean

]

9.]

193

,źt:i 2B.B7 10.33

6.6tj

.4o 2.44

17,22

193 0.23

,l93

o.I]7

-

,10,14

4.94

14,53

0-00

0.06

3.04

0.10

21.60

53.86

22-oo

0.50

0,63

1.59

7.17

0.00

lntcrvai

20.97

52.27

14.B3

0,50

1,50 1.18 4.91 0.00 4.91

ceochemical

2.10-

0.05 0-45

0.49 4-41

Mcdian

1

sD max min

background

1B.B7

(10 90%)

]

5.23

47.05

1.4B

13,35

lcvcl, the values of Ni, Mn and Fe are sustaincd- A

8rowth oltwo lattef elements was rccorded, also Na incleases, wheIeas Ca slightly falls. (780 530 cm) (300 BC 500 AD, the GWoN La Tćne pe.iod and the Roman lron Age, the Mi8ration Period) thc lcvel is characteristic ofhigh indices ofCr and Ni, the values ofMn, Fc and P decrease, K appears, Na increases and high values are reached by Ca. (530 365cm) (500 1000 AD, the GWoN Ear]y Middle A8es) the level is typical ofhigh val ucs of Cr, stab]c pcrccnragc of Ni, low pcrccntage ol Mn, Fe and Ę as well as high values ofNa and Ca (365-185 cm) (1000 1600 AD, thc GWoN Midd]c Agcs and thc Fcudal in the seventh 1evel cu and zn occur, cI decreases and then in creases, Co appear, there is agrowń of Ni, Pb, Mn, Fe, Ę and Na, and Ca somcwhat falls.

5

6

-

7

Agc)

GWON8 (l85 55cm) (l600 1990AD,theln, - this level is characterized by an increasc in Va]ucs oftracc c]cmcnts ]ikc Cu, Zn, cd, dustrial Revolution)

Co, Pb as We]l as Cr and Ni, by sli8ht decrease ofMn conlenl, wiń high index ofFe and poussium; values of Na also grow in scdimcnt whcrcas thc pcrcenlagc of ca lowers. (55 0 cm) (1990-2001 AD, the presGWoN ent day) further grow of trace elemcnts i s obscrvcd in the ninth lcvcl, va]uesofMn, Fe, P and K somewhat fall, there is a 8rowth ol Na content and a slight decline in Lhe percentage ofCa.

9

First records of microelements appeaf in the GWON 4 level, however ńeir percentage is Small. Considerable contents of tlace components, above statistical geochemical background, are observed not earlier than in the Middle Ages the GWON 7 level (Table 1, Fig. 5). Namely during the Middle Ages the settlement in the Middle Obra River region moved to the

193

1g:]

4..]5

,r

1.52

193

PKNa

(mj]/kg) 193

number of samplcs,

(g/kd 193

Ca G/kg)

F/kg)

193

193

].5,1 56].79 5507.44 732.28 o,)9

0,46

2oB.73

,

o.22

0.45

206.7B

o.14

o.24

277.65

0.]ti

0.o7

.17.70

4.2o 3.05

193

Fe

(mdk8)

-

56]-79

54D7.25 730.15

0,00 553.49 4465.69 934.38 5,06 79.49 -l030.91 157.04 .IJ2

7a1 .53

7.a71.26,1469.,13

1.t]5

0,69

o.oo

416.70

2671.77 5P,3.22

0.05

0.59 0.17

8.7 6

27.02

364.83

4699.49 BB5.91

1.79

o.42

0.BB 7.BB

24..]1

2.7o-

]6,4?,_ 328-35

4229.54

469.95 88,59 0,18 797.32 1.61

0,04 0 .]7

9.45

27

plateaux; uplands were deforested, what influenced the acceleration of element cy-

cle, which was marked in geochemical composition of the lacustrine sediments

0ASiEWICZ/HILDEBRANDT-RADKE 2009; JASIEWICZ,/HLDEBRANDT_RADKE in this volume).

The correlation matlix analysis proved that trace elements zn, cu and pb show significant correlations (Table 2). Increased content and mutuaJ right relation5 may indicate their anthropogenic origin. Another conclusion that can be drawn from the correlation marTix is a substarrtjal connection

between the microelements mentioned above and k and Na, which are alkaline envilonmental components. Mutual essential relations might confirm their human-made source aS the occurrence ofpotasSium and sodium can be an indicator of intensified soil erosion in the drainage area, wheleas in the present day it may also be an indica, tor of soil fertilization. calcium however, which is dominanL in geochemical composition, shows no colrelation to other elements. As it was emphasized earlier, very high content of calcium carbonates was recorded in the Whole profile. So it may prove that calcium originated in the lake drainage area as a result ofpro-

sedi ments. Nevertheless, carbonates must cesses ofleaching caJbonate morainic have origina ted in phyroplankton.

scdimenLob+ical, Ceochcmjcal and DiaLom /nvest]8alions on sediments ofLake Wonlesc

.

39-],34 1{}0,26

)11 .o7 21.1,| 1

l]9

.97

Tablc 2 Spearmnn correlation cocfficicnts amon8 gcochemi(]al componcnt5 in the Lake Wonicśćscdimcnts (si8nificance levelrr = 0.05).

Cu

7n

Cr

cd

Co

Ni

1'K

PbMnFc

NaCd

CU Zn

Cr Cd Co Ni Pb

Mn Fc P K

Na

Ca

0.7t}

0,09 0.56 0-47 0,43 o.72 0.32 0.3B 0-30 0,1]0 0,52 0,14

0.07

o.4I] 0.,ł5 0- ]źJ 0.67 0,:J3 0,.]1 0.32 o.73 0.51 {].46

()-25 0.2tJ

0.3 B

o.22 0.09 0,{]2 0.49 0.12 0.2B 0.04 0.05 o.21 o.42 0.45 o.49 0.51 0.-] t] o.29 -0.29

0,12 0,,]

0

D.2B

0.03 a.12

0,04 0.12 0.01

0.34 o.44

0,:J9

0,15 0.51 o.2., 0.03 0.67 o.21J 0.61 o-29 ()44 o2\

0.59

0,04 0.47 0.37 o.o7

,0.0-]

0.34 0.2B o-04

0-28 0.05

0.20

0,.5 B

-0.34

0,-]

9

Diatom investigation Diatoms are very well preserved in the sediments of Lake wonieśćas it was demonstrated by diatom flora analysis. Generally, ]82 diatom ta,\a were identified in the examined material, including 158 belonging to Pennales and, ż4 ro Centrales (Fi.g. 6).

Fis, 6 DistribUtion of diatonr ccoIo8ica] gr{)up§ in lho Lakc

Wonicśćplorile.

On the basis of mutations in species composition, the core was divided into 10 local diatom levets (WON). The following indicarive paramełeIs were raken into account: habitat, halobic preferences, domi-

nant taxa, preference as fal as pH and trophy are concerned (Fig. 7). WoN I (2072 2012 cm) (7800 7500 Bc,

Borćal

period). This dcposit is domjnatcd by planktic taxa (Cyclotella comens{,

C- ocellata, Puncticalata

rddiosa\.

of thc group consisted of bcnthic taxa. Thking halobi. qyslem inlo a,(oUnl. lrcshrłaLer spccies a, wcll as freshwater-brackish oncs, which correspond to