GEOCHRONOMETRIA Vol. 18, pp 35-40,2000 - Journal on Methods and Applications ot Absolute Chrof/ology AGE OF GLACIOTECTONIC STRUCTURES ON THE WOLIN ISLAND IN THE LIGHT OF LITHOSTRATIGRAPHIC DATA AND RADIOCARBON DATING 2 RYSZARD K. BORÓWKA l, TOMASZ GOSLAR2 and ANNA PAZDUR 'Deparlmenl ofGeolog::; and Palaeogeography, Ins/iW/e of Manne Sciences, Szczecin Universi/y, Felczaka 3a, PL-71-41 2 Szczecin, Poland (e -mail: [email protected]) 2 Department of RadioisalOpes, Institule of Physics, Silesian University of Technology, Krzywoustego 2, PL-44-100 Gliwice, Poland (e -mail: [email protected][email protected]) Abstract. On the basis of Iithostratigraphie analysis of deposi ts forming lhe Wolin End Moraine as well as radioearbon dating of the intercalations of organie maner found amongst su eh deposils, the age of glaeioteetonie struetures existing in the area of morainie hills was determined. It is claimed that both th e glacioteetonie defor­ mations and the end moraine itself were formed during regression of the last gla­ eiation_ l. INTRODUCnON In this work the authors attempted to determine the age of the Wolin End Moraine and the glaciotectonie The age determination of glaeiotectonic structures deformations existing in its area by referring to some can be achieved up to date with either lithostratigraphic new litho- and biostratigraphical observations. These or morphostratigraphic method (Rotnicki, 1998). In the were also confronted with the results of radiocarbon first one, marked by a greater universality, the age of dating obtained for selected intercalations of organie glaciotectonic structures is derived indirectly by consi­ matter found in the sandy and silty-sandy exposures in dering the age of the you ngest deposits containing these the northern and central regions of the Wolin hills. structures and the age of the oldest deposits covering the perturbed formation_ The seeond one, most com­ 2. GEOMORPHOLOCY monly applied to young glacial areas, puts in relation the glaciotectonie perturbations with the correspond­ One of the most characteristic relief features of the ing marginal zon es which mark the ensuing glaciation Wolin Island are the so called Wolin hills (also known ar deglaciation stages of these areas. The accuracy of as the Wolin End Moraine), reaching the average sueh dating methods is usually not high and does not height of 60 m above sea level with the max.imum height even allow relating the glaciotectonic perturbation of 115 m. They stretch from the environs of Świ ę to u ść zones to given glacial periods. However, the accuracy to the north eastern part of the island, in the direction improves whenever there is a way of absolute dating of Międzyzdroje, to the south western part in the direc­ both the glacioteetonieally di sturbed deposits and for­ tion of Lubin (Fig. 1)_ Geological structure of these hills mations covering these deformations (Rotnieki, 1998). is in certain parts perfectly exposed in the cliffs devel­ Sueh a situation is eharacteristic of the Wolin Island, oped in the northern parts of the hills, on the coast of for whieh as early as in the beginning of this century Pomrneranian Bay, and in their southern parts towards the rafts of Mesozoic rocks were described and identi­ the Szczecin Transgression. The relief of these hills fied amongst the Quartenary deposits together with proves to be particularly interesting. It is composcd of a number of structures disturbing normallayout of bed more and less elongated and elosed depressions havi ng exposures in cliffs (Deecke, 1907). These structures the relative heights of a few tens of metres. The analys is classified by C. Heberman (1913), W. Hartnack (1926) of the Wolin hills relief carried out with a topographi­ and K. Keilhack (1930) as belonging to a group of cal map with scal ing of 1:10,000 allowed discovering glaciotectonic deformations were considered in rclation a elear orientation of these secondary forms (Michalak, with transgression of the last ice sheet (Karczewski, 1997)_ It was also 'concluded that in the northern part 1968) as well as older glaciations (Krygowska and of the island the axes of the forms are oricnted along Krygowski , 1965). the run directions of principal overthrusts_ The Wolin Age o[ glacioleClOnic slructures on [he Wolin !s/and .. BALTlC SEA SZCZECIN BAY G§' 1'1- ~. E1J5 0 8 i::::;::;:;:;: 7 t·;.:-:-:18 1··:::::::::::1"0" :':0]13 WrWl.. ('.ela" R'j.. o 11 Fig. 1. Geomorphological map of Wolin Island (after a manuscript by A. Karczewski, 1968): 1 - morainic plateau, 2 - eskers, 3 - end moraines, 4 - kames, 5 - melt-out depresions, 6 - scarps, 7 - outwash plains; 8, 9, 10, 11 - terraces o( Lower Odra Valley. 12 - erosional-denudative valleys, 13 - ice marginal valleys; 14, 15 - inland and coastal dunes, 16 - lakes and streams, 17 - research sites, 18 - location of Wolin Island. hills together with their numerous glaciotectonic struc­ glaciotectonic structures covered by f1uvioglacial depos­ tures constitute one of th e youngest marginal zones of its, which form the so called karne plateau, exist here the last glaciation period in Poland. They were usually (Krygowska and Krygowski, 1965; Krygowski, 1967; beLieved to originate from the Wolin-Gardno Phase Matkowska et al., 1977; Ruszał a et al., 1979). The second during which the ice margin is supposed to have run view is difficult to uphold in the light of recent geologi­ along the contemporary coast \ine (Galon, 1968; eaL research which shows that sa ndy series covering the Roszkówna, 1968; Boulton et al. , 1985). More recent re­ glaciotectonieally perturbed deposits is a eover of Late search of the marginal zones of north western Poland Glacial aeoli an sands intercal ated hy Alleród fossil soil seems to cóntrast this view (Lagerlund et al. , 1995; (Borówka et al., 1982, 1986) and that con tradiets the Kozarski, 1995; Mojski, 1995; Rotnicki and Borówka earlier belief which assumed a cover of f1uvioglacial 1995 a,b). The present view suggests that the marginal karne deposits. zone related to the Wolin hills was formed between 15,500 and 14,200 BP. The lower age limit of this mar­ 3. LITHOSTRATIGRAPHY ginaL zone is determined by the oldest swampy-Iacll s­ tfine deposits found at the bottom of the Pommeranian Thanks to the geological researcb and observations Bay and their radiocarbon dating falls in the range be­ carried out between 1996 on th e seaside cliff in the en­ tween 14,060±220 ahd 13,100±300 BP (Kramarska and virons of Grodno and Świętouść it was stated that the Jurowska, 1991). The upper age limit of the Wolin mar­ glacioteetonie exposures inc\ude the fo llowing deposit ginal zone is harder to determine, however it should not series (Fig. 2 and 3): go beyond 16,200 BP, that is the estimated age of the - Cretaceous marls (embedded as gla ciotectonic Pommeranian marginal zone (Pommeranian StadiaL) scales and rafts amongst Quaternary fo rmations); whieb in tum was calculated on the basis of the aver­ - glacial grey till, in some parts also brown; age rate of deglaciation of the last continental glacier - sandy series amongst which appears the marine start ing from its maxi mum reach (Kozarski, 1995). malacofauna characteri stic of Eemian sea (Borówka However, the genesis of the Wolin hills is open to et al., 1999); question. Some authors consider them as Moraine hills - sandy-silty series whieh sporadically feature interca­ thrust by glaciotectonic process (Hartnack, 1926; lations of organie matter and very rarely the lumps Ży nd a, 1962; Bryi, 1972; Borówka et al. , 1982) whereas of gravel with sparse boulders. others share the opinion that only old Pre-Vistulian -36 - R. K. B OrlT<JJka et al. The głac iot ec t onica U y pcrturbed formations might ous slructures charactcristic of dynamie contact with reach n ca rły up to the very hilltops, in partiClJ!ar in their lower Iying deposits are observed. elevation zones. In such locations they are oflen cove­ A series of glacioteclonically pcrturbed formations red by a thin łayer of brown gladal liII with a thickness and the youngest layer of glacial till are usually signifi­ of strata up to a few metres. In the underclay numer- cantly eroded (Fig. 2 and 3). Above this di scontinuity area the following might appear: Grodno - Gosań 1 Depositlonal Stratigraphy Lithology I environment lłI ....,.... lIIn Gl ~ C Bo o eeoł l an :x:: ....lIIn . toi ....lIIn g~ lluYiogIacill ftUYlał (1) C . .. ~ aJ 1----- 25 GOO. 300 BP (G,H20S1)r- / 27 100 •. ,3400... BP (Gd-~) - - - > ~ 30 100.600 BP (Gd-12063) lllcualrine 31 ~. 2000 BP (Gd-10622) tIuv.1 !lO > 25 GOO BP (Gd-9933) morine (1) ~ > 26 100 BP (Gd-9948) > 29300 BP (Gd-11376) > 30 \ 700 BP (Gd-9927) ~-----1 > 35 -400 BP (Gd-1 1378) gl..,;gone ~--- Fig. 2. Generalized Iithostratigraphic log (rom Wolin End Moraine-Grodno Site. -37 - Age olgłaciol ee LOnie SlnlClUres on l ite Wolin Island ... - covers of slope deposits; et al., 19R2). Taking into account the li tostratigraphic - deflational pavement; data it is safe to say that the perturbations described - trisectional cover of aeolian sands within which the formed between the Eemian Interglacial and the intercalations of two fossil soils commonly appear; Late Vistulian interglacial. The marine malacofaUlJa thc oldcr one has the features of poorly developed found in perturbed sandy series near Świ n oujści e tundra soi l of Usselo type and originates from (Borówka, Makowska and Cedro, 1999) dates from AlIerod period, whereas the yo unger one was al­ the Eemian Interglacial, whereas the oldest cover of ready forming during Holocene period (Borówka aeoli an deposits dates from the Late Glacial and more accurately from the Pre-Allerod period. ŚWIĘTOUŚĆ Depositional 1·C Age Stratigraphy lithology environment soWeeoIlen aeollan • 1880:65 BP -1OiLIbOg (Gd.1062) aeolian .11590:270BP lOiI/DOII (GcI-e31> eeoIian ~ ~ f----- c: lU ::J nuvial II) GNdzi'Idz ....ii) VI ~ ~ Iacuotrine """;n8(1) &.