Differences in the Regional Stratigraphy of NE Poland Caused by Vertical Movements Due to Glacioisostasy

Wo j c i e c h Mo r aw s k i

Geologos, 2009, 15 (3–4): 235–250 doi: 10.2478/v10118-009-0006-x

Differences in the regional stratigraphy of NE Poland caused by vertical movements due to glacioisostasy

Wo j c i e c h Mo r aw s k i

Polish Geological Institute, Rakowiecka 4, 00-975 Warsaw, Poland; e-mail: [email protected]

Abstract

Geological mapping in combination with geophysical investigations and borehole analyses show differences of the Pleistocene between the Warmia and Mazury palaeogeographic provinces in NE Poland. The (more western) Warmia province has a crystalline basement that is covered by a folded sedimentary succession of 2–4 km thick. The (more eastern) Mazury province (eastern) has a basement that forms part of the rigid East European crystalline craton, which is covered by a sedimentary cover of only 1–1.5 km thick. Cyclic loading by the Pleistocene ice sheets in this area induced glacioisostatic processes of different intensities, resulting in changing palaeogeographic conditions. The changes were increased by intense neotectonic activity that was induced by the ice sheets in the intermediate zone between the two provinces, stretching along the western slope of the crystalline craton. Significant part of intermediate zone forms a belt of crevasse-infill landforms deposited between the Warmia and Mazury lobes of the last glaciation. Studied deposits reveal a cyclic reactivation of the interlobe zone during the successive Pleistocene glaciations. Considerable variations of the relief of the top-Neogene, vertical discontinuities cutting the Pleistocene and Neogene, stratigraphic gaps within the Pleistocene succession, and thick glaciolacustrine successions result from the vertical neotectonic movements in the intermediate area between the two provinces.

Keywords: neotectonics, Poland, Pleistocene, stratigraphy, palaeogeography, glacioisostasy

Introduction variations. The western area is characterized by both a deep-seated crystalline basement NE Poland is not a uniform region in terms and a considerable westward-increasing thick- of Pleistocene stratigraphy and palaeogeog- ness of the tectonically disturbed sedimentary raphy. Both geological maps and regional cover of 2–4 km thick. The eastern area has field studies indicate differences between the a crystalline craton covered by a tectonically Warmia region in the West and the Mazury undisturbed sedimentary succession of 1–1.5 region in the East. These differences were the km thick (Książkiewicz et al., 1974; Tyski, basis for distinguishing two Pleistocene pal- 1974). The boundary between these structural aeogeographic provinces: the (more western) units follows the western slope of the crystal- Warmia and the more eastern Mazury prov- line craton and the adjoining marginal trough ince (Morawski, 2005a). (Kotański, 1977). This boundary, which ap- The crystalline basement in NE Poland and proximately coincides with the trend of the in- its pre-Cenozoic sedimentary cover show also termediate zone between the two Pleistocene Differences in the regional stratigraphy of NE Poland caused by vertical movements due to glacioisostasy 236 Wojciech Morawski palaeogeographic provinces (Fig. 1), has geo- Petecki). They were used in particular for the physically and geologically been shown to construction of geological cross-sections, main- represent a zone of neotectonic mobility that ly for the identification and location of discon- is related to Pleistocene vertical glacioisostat- tinuity zones and the sub-Neogene surface ic movements. The vertical movements were relief. Geoelectrical sonar profiles (T. Okrasa, much larger in the western area than in the unpublished; B. Jagodzińska & R. Kalitiuk, un- east, resulting in a different palaeogeography published) were run over a distance of about characterizing these provinces (Morawski, 50 km (cross-sections E-F and I-J in Figs. 3 and 2009d-this issue). 4). A 12-km long high-resolution reflection- seismics profile (A. Opak, unpublished) was acquired along cross-section I-J (Fig. 4). Objective Complete cores were obtained for analysis from six boreholes, viz. at (1) Żardeniki (153 The purpose of the present contribution is to m deep), (2) Wilimy (267 m) (Mańkowska & document the geomorphological, lithological, Słowański, 1968, 1980), (3) Biskupiec (248 m), stratigraphic and palaeoenvironmental varia- (4) Klucznik (303 m), (5) Nerwik (140 m) and bility within the Warmia and Mazury geologi- (6) Sąpłaty (300 m). Boreholes 1,2 and 4 are local/geomorphological provinces and the zone cated in the Warmia province, borehole 6 in the in between. The resulting reconstruction of the Mazury province, and boreholes 3 and 5 in the processes that operated during the Pleistocene centre of the intermediate zone (Figs. 1, 3–5). within the intermediate zone thus will explain All boreholes provided complete Pleistocene the factors determining differences between cores. Boreholes 2,4 and 6 represent almost these two provinces. the complete Cenozoic. The cores were sam- pled and analysed for lithology, petrography, palynology and micropalaeontology. The li- Methods thology and petrography of 31 till successions were determined in the laboratory. Data of Detailed mapping, in combination with lithological analyses (by J. Rzechowski & B. geophysical investigations, borehole analyses Sobczuk, unpublished; K. Kenig, unpublished; and laboratory analyses, was performed in or- B. Marcinkowski & M. Wyszomierski, unpub- der to establish the geological structure of the lished) were used too. The results were corre- study area and to reconstruct the processes that lated with similar data from adjacent areas and modelled the intermediate zone between the hence their stratigraphy was established (Figs. Warmia and Mazury provinces. The investiga- 4, 5). tions focused on an area of approx. 600 km2 in Laboratory analyses covered also glacioflu- the middle part of the intermediate zone, more vial, glaciolacustrine and mire deposits that precisely in the Pasym-Dźwierzuty-Biskupiec- separate till complexes. Sands were analysed Jeziorany-Kolno region (Figs. 2, 3), where the for grain size, roundness, and morphoscopy. intermediate zone is best recognizable in the Till analyses included grain-size analysis, iden- present-day topography. tification of heavy minerals, carbonate content, Geological maps were prepared at a 1:50,000 and petrography of 5–10 mm gravel. scale (Morawski, 2009a,b,c). About 4500 shal- The stratigraphy was established on the low (up to 4 m) and 210 deeper boreholes (up basis of both regional correlations and the till to 30 m) were drilled. Data from archives re- lithostratigraphy as characterized by petro- garding approx. 300 boreholes were interpret- graphic coefficients, which are based on the ra- ed and compared with the new-made ones. The tio of Scandinavian to Baltic rocks: O/K, K/W maps of the local gravity anomaly were pro- and A/B (in which O = sedimentary rocks; K duced on the base of two unpublished gravi- = crystalline rocks and quartz; W = carbonate metric maps (sheet Dźwierzuty by Z. Petecki rocks; A = rocks non-resistant to weathering; B & J. Twarogowski and sheet Biskupiec by Z. = resistant to weathering). The values of pet- Differences in the regional stratigraphy of NE Poland caused by vertical movements due to glacioisostasy 237

Fig. 1. Location of intermediate (interlobe) zone and positions of ice-sheet margin during the Vistulian Glaciation. 238 Wojciech Morawski rographic coefficients have been published in monly of local extent. Another common fea- Kenig (1998) and Lisicki (2003). ture are sedimentary hiatuses that may span Palynological and macrofaunal investiga- even few glaciations. Interglacial deposits are tions were carried out on the Neogene and almost absent. These features prove intensive Palaeogene deposits for boreholes 4 and 6, activity of cyclic erosional processes. allowing to establish a detailed stratigraphic subdivision (Słodkowska, 2009-this issue). The local and regional ice-movement di- The Mazury province rections during the last glaciation within both ice lobes was reconstructed by analysis of lin- The Pleistocene of the Mazury province ear glacial landforms (morpholineaments) commonly shows a considerable thickness (lo- (Morawski, 2003c, 2005b, 2009d-this issue). cally more than 250 m) and laterally continuous lithostratigraphic units containing many tills interbedded between organic interglacial Geographical and geological deposits. Organic successions allowed paly- setting nological dating of the interglacials and in- terstadials The entire succession comprises 15 till units. They were assigned to individual The study area is situated in the western glaciations and stadials based on regional cor- part of the Mazury Lakeland, NE Poland. Its relations and laboratory analyses of their pe- western part belongs to the Olsztyn Lakeland, trography and lithology (Lisicki, 2003). The till and the eastern flank is located within the horizons are attributed to the following glacia- Mrągowo Lakeland. tions: two stadials of Narewian (Menapian); two stadials of Nidanian (Cromerian Complex – Glacial A); two stadials of Sanian 1 (Elsterian The Warmia province 1); two stadials of Sanian 2 (Elsterian 2); Liwie- cian (Fuchne); two stadials of Odranian (Dren- The Warmia province is characterised by thian); two stadials of Wartanian (Warthian); discontinuous till horizons at various alti- and two stadials of Vistulian (Weichselian). tudes. The tills have commonly been eroded away completely, so that only residual boulder layers are left. Early Pleistocene till complexes The intermediate zone of considerable thickness occur at a local scale only in deep erosional scours and depressions Geomorphological and geological investiga- formed by glacial erosion. The only area where tions show that the Warmia and Mazury prov- till form continuous, locally thick horizons is inces coincide with the extent of two ice lobes the northern part of the province. In a single of the last (Vistulian) glaciation ice sheet, the borehole, even 8–9 till horizons can occur su- Warmia and the Mazury lobes (Fig. 1). The inter- perimposition: two till horizons of the Nidani- lobe zone coincides with the intermediate zone an glaciation (Cromerian complex – glacial A), between the two provinces. Structural studies the Sanian 1 (Elsterian 1) and Sanian 2 (Elste- suggest that tectonic mobility of the intermedi- rian 2), the Odranian (Drenthian), and two till ate zone, induced by glacioisostatic movements, horizons from both the Wartanian (Warthian) resulted in the formation of interlobe zones of and the Vistulian (Weichselian). similar location during the successive Pleis- In the South of the province, the Pleistocene tocene glaciations (Morawski, 2009d-this issue). is dominated by glaciofluvial and glaciolacus- In the topography and near-surface geo- trine deposits that commonly form thick com- logical structure, the intermediate zone is plexes. Glaciofluvial successions fill channels manifested in the form of a narrow, NNE-SSW that are often deeply incised into each other. trending belt of crevasse-fill landforms com- Thick glaciolacustrine successions are composed of sand/gravel deposits. It stretches Differences in the regional stratigraphy of NE Poland caused by vertical movements due to glacioisostasy 239

Fig. 2. Digital model of the studied area. over approx. 80 km from the Omulew Lake in ence in elevation between the lowest and high- the South trough Pasym and Biskupiec and est points is nearly 150 m. Numerous kame further towards the NE to Reszel in the North hills, extensive kame plateaus, kame terraces (Fig. 1). Its width varies from a few hundred and glaciolacustrine plains exist there. metres to some kilometres. The zone is best ex- The area is cut by deep, NNE-SSW trend- pressed in the middle sector of the study area ing subglacial tunnel valleys that are often (Pasym-Biskupiec-Kolno) (Figs. 2, 3). filled with lakes. The valleys are commonly narrow and very deeply incised (up to 100 m). The maximum lake depth is about 40 m. Broad, Geomorphology flat-bottomed valleys are also present. In the northern part of the area abundant dead-ice The present-day topography of the area moraines occur. The drainage network of the came into existence during the retreat of the ice area, with numerous kettle holes, is poorly de- sheet of the last stadial of the Vistulian glacia- veloped. tion from the area between the Mazury and Analysis of the orientation of linear glacial Warmia lobes. landforms (glacial morpholineaments) indicates differences in their arrangement. In the North, four major sets of directions are present The Warmia province (Fig. 6). The dominant N-S direction is con- nected with the subordinate W-E direction. The western part of the study area devel- The remaining linear landforms show less well oped as a result of deglaciation of the Warmia developed preferred orientations, but two sets, lobe and now forms the Olsztyn Upland. This running perpendicular to each other in NNW- region is topographically diverse; the differ- SSE and NNE-SSW directions can be distin- 240 Wojciech Morawski guished. In the central part of this western Biskupiec, the zone changes its direction (to area, most of the linear landforms are oriented N-S) and geomorphologic character too. Slight- NW-SE and NNW-SSE, together with subordi- ly undulating belt of the glaciofluvial upland nate direction NE-SW (Fig. 6). In the South, the is dominated by elongated depressions and morpholineament orientations are poorly de- small isometric dead-ice moraines. The ridges veloped, but it is possible to identify four sets consisting of sediments deposited in ice-sheet forming two conjugate systems oriented like crevasses are present further northwards. An those in the northern part (Fig. 6). important element determining the relief of the zone is the presence of narrow valleys deeper than 60 m. The Mazury province

The topography of the eastern part of the Lithology, stratigraphy study area was shaped during deglaciation of and palaeogeography the Mazury ice lobe. The hummocky Szczytno Upland (Figs. 2, 3) was then formed. It is composed of tills with small landforms of dead-ice moraines and kettle holes. The upland lies at The Pre-Pleistocene a higher altitude than the western area of the Olsztyn Upland. The relief shows height dif- In the Warmia province, the Early Palaeo- ferences of several metres only. The drainage zoic deposits were folded during the Caledo- network is poorly developed. The easternmost nian orogeny before the Arenigian (Middle periphery of the area is occupied by an out- Ordovician). The Lower Palaeozoic is uncon- wash plain extending towards the East. In the formably overlain by the Arenigian, which is, central part, in the Rasząg-Botowo-Labuszewo in turn, covered by Late Palaeozoic and Mes- region (Fig. 2), the belt of endmoraines marks ozoic formations. The eastern periphery of the extent of the Pomeranian Phase of Weich- the area coincides with the crystalline craton selian (Fig. 1). slope and the Napiwoda-Purda-Ryn-Garbowo The orientation of linear landforms, in the marginal trough. The trough is pre-Arenigian south-eastern part of this area shows a pre- tectonic palaeostructure (Kotański, 1977). In dominant NW-SE direction (Fig. 6). To the east, the Mazury province, the western end of the the dominant NNW-SSE direction is typical of East European craton forms the hypothetical the Mazury lobe of last glaciation (Morawski, Giżycko-Szczytno-Różan elevation. The sedi- 2005b). mentary cover is poorly developed here; the Palaeozoic is absent, but the Mesozoic deposits form a continuous, undeformed succession. The intermediate zone Complete Neogene and almost complete Palaeogene successions were encountered in Between the areas described above, a hum- boreholes on both sides of the intermediate mocky belt, being a glaciofluvial upland is zone. The thicknesses of the corresponding present. It is covered with landforms built by lithostratigraphic units are comparable both of the infilling of crevasses and subglacial chan- the Warmia and the Mazury province, and the nels. This NNE-SSW trending belt is identified sedimentary conditions during the Neogene with an interlobe zone (Figs. 2, 3). and Palaeogene were identical (Słodkowska, The landforms constituted by crevasse in- 2009-this issue). fillings occur as linear ramparts stretching in The top-Neogene surface relief is illustrat- NNE-SSW direction. They are a few hundred ed in six cross-sections through the marginal metres to about 2 km long and several tens to parts of the Mazury and Warmia provinces a few hundreds of metres wide. Their relative (Fig. 4). On the eastern (Mazurian) side, the height is from several to 20 metres. North of top-Neogene surface is relatively flat; it lies Differences in the regional stratigraphy of NE Poland caused by vertical movements due to glacioisostasy 241

Fig. 3. Geomorphology of the studied area. 242 Wojciech Morawski at an altitude of approx. 40–60 m a.s.l. On the extensive area. These deposits were probably western (Warmian) side, it is situated at about accumulated during retreat of the Narewian 0–20 m a.s.l. Seismic data (see Fig. 3 in Moraw- ice sheet. ski, 2009d-this issue) and the lithology in bore- Only one Narewian till, a few metres thick, holes indicate that several vertical discontinui- is present in the intermediate zone (Figs. 4, 5). ties exist within the intermediate zone. They The till contains detached fragments of Neo- can be considered as fault zones running ap- gene clays, thin concretions of ferruginous proximately from NNE to SSW. The depth of clay, fragments of wood and local rocks, and the top-Neogene changes in this area, ranging occasional Scandinavian crystalline erratics. from about 90 m a.s.l. to 90 m b.s.l. (Fig. 4). The composition of the heavy minerals sug- The pre-Pleistocene basement is composed gests that the till consists mainly of reworked of Mio-Pliocene and Miocene deposits; clay Neogene deposits. interbedded with silt and fine-grained sand, The overlying sands, which are 5–15 m occasionally with thin lignite layers. thick, are separated from the till by a boulder layer. The sands derived from redeposition of Neogene substratum together with the oldest Pleistocene deposits. The good rounding, The Pre-Vistulian Pleistocene very good sorting and the assemblage of the heavy minerals indicate long fluvial transport. The lithological and stratigraphical termi- The deposits represent a reach of N-S trend- nology of the Pleistocene units, used in the ing river valley, coinciding with the direction present contribution follows that applied for of the intermediate zone. This might be due to NE Poland, complemented by equivalents downward movements in this zone. The differ- from western Europe, mainly Germany (Ber, ences in elevation of the Narewian till on both 2006). sides of the intermediate zone (cross-section I-J The thickness of the Pleistocene deposits on in Fig. 4; Fig. 5) are worth mentioning in this the Warmian side (Fig. 5) varies from 113 to 165 context. In the Warmia province, the till is sit- m. Geophysical investigations indicate, how- uated about 30 m lower than in the Mazury ever, that the maximum thickness can reach province. 200 m. On the Mazurian side, the thickness of the Pleistocene deposits is 80–140 m (Fig. 4). In the intermediate zone, the thickness of the The Nidanian glaciation Pleistocene (Fig. 5) changes from 135 to 243 m. (Cromerian Complex – Glacial A) The thickness can be locally reduced by glaciotectonic deformation or/and vertical movements of tectonic blocks, with relative changes Three successive Nidanian deposits occur in height up to approx. 40 m (cross-section I-J to the East of the intermediate zone: glaciola- in Fig. 4). custrine deposits deposited during ice-sheet advance, a till complex and glaciofluvial sediments deposited in front of the retreating ice The Narewian glaciation margin (see borehole 6 and cross-section I-J in (Menapian) Fig. 4). On the western side, a complex with two tills is situated approx. 50 m lower than the till at the eastern side. Two Narewian tills corresponding to two No tills have been preserved in the central stadials occur in the Mazury province (Lisicki, southern part of the intermediate zone (bore- 2003). In the Warmia province, tills that may hole 5 in Figs. 4 and 5). In the northern part represent this oldest glaciation occur sporadi- of the intermediate zone (borehole 3 and cross- cally only in the northern part. Glaciofluvial section E-F in Fig. 4), two thin till units interca- deposits directly overlie the Neogene over an Differences in the regional stratigraphy of NE Poland caused by vertical movements due to glacioisostasy 243

Fig. 4. Geological cross- sections across inter- madiate zone. For location see Figs. 1, 3. 244 Wojciech Morawski lated with sand occur; they are more than 150 The Great Interglacial m lower in altitude than in the eastern area. (Holsteinian) (?)

The Sanian 1 glaciation (Elsterian 1) Deposits which age is interpreted as the Great Interglacial have been encountered in In the Mazury region, the Sanian 1 till the central part of the intermediate zone (bore- (Kasprzak & Lisicki, 1999) is several metres hole 5 in Fig. 5). They are represented by a suc- thick; its position is at an altitude of approx. cession of fine- and medium-grained sand with 80 m a.s.l. (see cross-section G-H in Fig. 4). In intercalations of mud and containing dispersed the Warmia province, the till is over 30 m thick organic matter. Winter (2005) mentioned and occurs at an altitude of about 25 m a.s.l., a predominance of coniferous tree pollen and (Morawski, 2001, 2003a) i.e. approx. 55 m lower a small amount of deciduous trees. The paly- than in the Mazury region (see cross-section E-F nological spectrum reflects a pine forest with in Fig. 4). Also on the western side, but closer to spruce, larch, birch and alder of wetland areas. the intermediate zone (cross-sections C-D and The sedimentation took place during the warm E-F in Fig. 4; borehole 2 in Fig. 5), the two till period. Similar sand and mud series with plant horizons occur at an altitude of about 17 m b.s.l., detritus occurs in the central part of the inter- i.e. almost 100 m lower than in the East. mediate zone (borehole 3 in Fig. 5). The upper part of succession contains the boulder layers which suggest fluvial accumulation followed The Sanian 2 glaciation (Elsterian 2) by erosional phases. Mentioned succession pre- sumably represent alluvial deposits of a valley The Sanian 2 sedimentary succession starts stretching in the intermediate zone. from thick clay and mud series (borehole 3 in Fig. 5), which was deposited in an ice-dammed lake, probably during ice advance. The lake had The Odranian glaciation formed in a deep depression extending along (Drenthian) the axis of the intermediate zone, indicating local strong subsidence (Morawski, 2009d-this issue). Two horizons of Sanian 2 till occur in The Odranian deposits form two till hori- the Warmia province. They are overlain by gla- zons and probably represent two stadials. The ciofluvial deposits representing the recessional lower till is underlain by clays, muds and sands stage (boreholes 1 and 2 in Fig. 5; see cross- deposited in small ice-dammed lakes that de- section E-F in Fig. 4). On the Mazurian side, veloped during ice-sheet advance. They occur a similar succession occurs at a 40–50 m higher mainly in the central and southern parts of the altitude, interpreted from geophysical investi- study area. In the southern part of the Warmia gations. In the central part of the intermediate province (borehole 4 in Figs. 4, 5), thick Odrani- zone (borehole 3 in Fig. 5; see cross-section E-F an succession (including a till complex of 46 m) in Fig. 4), the base of the Sanian 2 till lies almost occurs. Such a thick till complex was also found 50 m lower than on the Warmian side and some in the other boreholes located on Mazurian side 100 m lower than in the Mazurian side. Gla- of the intermediate zone (see cross-section G-H ciofluvial sands and gravels deposited during in Fig. 4). In the Mazury province, the Odranian ice-sheet retreat in the eastern region are situ- till complex occurs almost 50 m higher than in ated 50 m higher than in the western region. the Warmia region (borehole 6 in Figs. 4, 5). Differences in the regional stratigraphy of NE Poland caused by vertical movements due to glacioisostasy 245 Borehole data after Mańkowska after data Borehole Petrographic cofficients after K. Kenig (unpublished), B. Marcinkowski & M. Wyszomierski (unpublished). Stratigraphy Stratigraphic correlation of the Pleistocene profiles from the Warmia and Mazury provinces. See Figs. 1, 3 for borehole location. borehole for 3 1, Figs. See provinces. Mazury and Warmia the from profiles Pleistocene the of correlation Stratigraphic & Słowański (1980), Morawski (2009a, b). after Ber (2006). Fig. 5. Fig. 246 Wojciech Morawski

The Wartanian glaciation ince (cross-section A-B in Fig. 4). Locally, the (Warthian) thickness of this unit increases to over 50 m. Till is the marker glacial unit in this area; it covers the glacial upland of the southern part In the southern part of the study area, War- of Mazury province. In the central and north- tanian deposits are absent or preserved only ern parts of the study area, it occurs on both fragmentarily. In the North, a Wartanian till sides of the intermediate zone. The till forms occurs as a thin layer in both the Warmia and a laterally continuous horizon of several me- the Mazury provinces. Locally, the till forms tres thick (locally up to 50 m). a complex of two horizons. In the intermediate The glaciofluvial and glaciolacustrine units zone, there is usually only a horizon of clayey that were formed during ice retreat, dominate pavement. A number of laterally discontinuous in the Warmia region. They built the landforms successions of ice-dammed lake deposits were such as outwash plains, kame terraces, kame accumulated during ice advance, whereas gla- plateaus and ice-dammed lake plains. ciofluvial deposits are interpreted as sedimen- The intermediate zone is a belt of glacioflu- tary record of ice retreat. vial upland, which represents an area built by sediments that were deposited in interlobe area. Deposition took place at the contact with The Eemian(?) interglacial dead–ice masses. In this way derived the sands and gravels, commonly very poorly sorted, of- The Eemian interglacial is represented by ten with large boulders and intercalations of lacustrine deposits containing some Miocene muds. They contain lenses of diamictic debris- and Oligocene redeposited material. They oc- flow deposits occasionally. Such deglaciation- cur in the central part of the intermediate zone derived facies, deposited close to dead-ice, (borehole 3 in Fig. 5; cross-section E-F in Fig. was defined by Morawski (1984, 1985, 1989) as 4). Poorly preserved Pleistocene and Neogene ‘watermorainic deposits’. In the central part of pollen specimens occur. Lacustrine deposits the interlobe zone, the series can be over 35 m indicates local subsidence of this part of the thick, as in borehole 5 (cross-section I-J, Fig. 4). intermediate zone. Redeposition of Miocene The Mazury province forms a hummocky and Oligocene deposits suggests the presence glacial upland. The morphology of Warmia of locally uplifted parts of the intermediate province is more complicated due to complex zone. One of such Neogene blocks was drilled deglaciation. In the southern part of this region, at 60–70 m a.s.l. at Najdymowo, west of Bisku- high kame hills, kame plateaus, kame terraces piec (see cross-section E-F in Fig. 4). and local ice-dammed lake plains developed. Moreover, deep glacial channels were partly filled with lakes. The northern part isa till- Vistulian glaciation (Weichselian) plain and local outwashes (Fig. 2).

Four units compose the Vistulian sedimentary succession: two lower ones deposited dur- Discussion and conclusions ing ice-sheet advance (glaciolacustrine and glaciofluvial units), the main unit of glacial till The study area lies within a zone occupied and the upper unit of glaciofluvial and glaci- by the last Scandinavian ice sheet. North- olacustrine deposits formed during ice retreat. eastern Poland was covered by ice stream, The glaciofluvial sands and gravels deposit- which moved from the NNW towards the SSE ed during ice-sheet advance occur as a laterally (Punkari, 1997; Boulton et al., 2001; Stokes & continuous, few to more than 20 m thick unit, Clark, 2001; Houmark-Nielsen & Kjoer, 2003), both in the southern part of the Mazury prov- referred to in the Polish literature as the ‘Maz- ince (cross-sections G-H, I-J and K-L in Fig. 4) ury ice lobe’. To the West, another ice stream and in the northern part of the Warmia prov- occurred, called the ‘Vistula ice lobe’ (Roman, Differences in the regional stratigraphy of NE Poland caused by vertical movements due to glacioisostasy 247

Fig. 6. Directions of ice-sheet advance on E Warmia and W Mazury areas. LGM – last glacial ice-sheet margin.

2008; Wysota et al., 2009). The reconstruction In the immediate neighbourhood of the inter- of ice-movement directions, through analysis mediate zone, the directions show local vari- of the orientation of linear glacial landforms ability (Fig. 6). (Morawski, 2003c, 2005b), shows that the dom- It can thus be hypothesized that an inter- inant direction in the Mazury region is from lobe zone was formed when the Warmia lobe NNW to SSE (Fig. 6). became isolated from the Mazury lobe. Ini- Geomorphological analysis revealed a lin- tially, the Warmia lobe was triangle in shape ear zone of several kilometres wide with NNE- and joined the Vistula ice lobe in the West (Fig. SSW trending ridges derived from ice-crevasse 1). The process of isolation of the Warmia lobe infilling. The zone is expressed in the topog- was accompanied by a change in the ice-move- raphy along a distance of some 60 km. The ment direction more to the South, and proba- maximum ice-sheet extent of the Mazury lobe bly by acceleration of the movement, resulting runs approx. 20 km south of the study area. In in a farther southward extent than the Mazury the West the maximum ice-sheet margin was lobe (Fig. 7). An extensive glacial upland de- extended about 8 km more towards the South veloped in the Mazury area. It is composed of (Figs. 1 and 6). tills with an outwash plain in the eastern part. To the west of mentioned zone, the ice In the Warmia area, kames, ice-dammed lake moved mainly N-S, typical of the Warmia area. plains, glacial channels developed. They de- 248 Wojciech Morawski

gion (cf Morawski, 2009d-this issue). The subsidence resulted in a downward movement of the ice-sheet substratum towards the west along the intermediate zone, causing acceleration of the ice flow in the western area, i.e. the Warmia lobe (see ice-sheet extent in Fig. 1). Downward movements of the substratum towards the west during the deglaciation resulted in both a subdivision of the Warmia lobe into individual ice blocks and deposition in crevasses and ice-dammed lakes. In the central part of the study area, a zone in which the ice-sheet margin stagnated (Po- meranian Phase of Vistulian) is expressed by a well-developed belt of frontal moraines (Figs. 1 and 3). In the West, in the Warmia area, frontal-moraine belt lies in more southward position than in the East (the Mazury area) (Fig. 1). When the activity of the Vistulian ice sheet increased during the Pomeranian Phase, the Warmia lobe advanced again approx. 15 km farther southwards along the interlobe zone than the Mazury lobe. Two Pleistocene palaeogeographic provinces (Warmia and Mazury) can be distinguished. They are divided by intermediate zone. The Mazury (eastern) province is characterised by a continuous succession of Pleistocene deposits, in particular tills that mark several phases of advance of the Scandinavian ice sheet. These Pleistocene marker horizons exist on the con- Fig. 7. Development of interlobe zone. LGM – last glacial stant altitudes. In the Warmia (western) prov- ice-sheet margin. ince considerable stratigraphic gaps occur. The tills occur as lenses and do not form continu- rived in local depressions and tensional cre- ous horizons. They are separated by thick gla- vasses which were formed on/in the ice sheet. ciofluvial and glaciolacustrine deposits. The linear, NNE-SSW trending zone of The Pleistocene successions in the Warmia landforms built by sediments accumulated in and Mazury provinces represent different ar- ice-sheet crevasses is well expressed in the to- rangement of Pleistocene sedimentary succes- pography. This was an interlobe zone, along sion, indicating different palaeogeographical which the Mazury lobe became divided from processes during deglaciation of Warmia and the Warmia lobe, and which moved some 8 km Mazury ice-sheet lobes. NNS-SSW trending farther southwards than the Mazury lobe dur- boundary between the provinces coincides ing the Main Stadial of Vistulian. with the interlobe zone. After interlobe zone formation the ice-sheet The question arises of what were the rea- direction of Warmia lobe was changed from sons for the palaeogeographical differences NNW-SSE to N-S (Fig. 7). between the two provinces and for the for- The formation of two lobes together with mation and location of the intermediate zone. interlobe zone probably was a result of strong Other questions are about the relationship of glacioisostatic subsidence of the Warmia re- the boundaries between these zones and the Differences in the regional stratigraphy of NE Poland caused by vertical movements due to glacioisostasy 249 interlobe zone that developed during the last intermediate zone. They were induced prob- glaciation, and about the cause of the change in ably by cyclic glacioisostasy. the direction of the iceflow and of the accelera- Detailed investigations of the palynology tion on the western Warmian side. and microfauna of the Neogene and Palaeo- The Pleistocene successions of the Warmia gene succession, performed on both sides of province occur at much lower altitudes than the intermediate zone (boreholes 4 and 6 in their equivalents on the eastern Mazury area. cross-section I-J Fig. 4), prove the similarity of Significant lateral variations within the whole both sedimentary conditions and thickness of Pleistocene architecture occur in the interme- the individual stratigraphic units (Słodkowska, diate zone. They suggest vertical neotectonic 2009-this issue). Palaeogeographical differenc- mobility of the substratum and hence local es between the Warmia and Mazury provinces differentiation of sedimentary and erosional refer only to the Pleistocene, which makes it conditions. The Pleistocene successions are lo- likely that this results from a different response cally reduced in thickness and are composed of the basement in the two areas to the advanc- almost exclusively of unsorted and very poorly es and retreats of the successive ice sheets. washed sands, gravels and boulders. Consid- Cyclic loading by the Pleistocene ice sheets erable stratigraphic gaps suggest strong ero- caused vertical glacioisostatic movements of sional processes that occurred throughout the the basement. The Warmia area underwent Pleistocene. The Neogene substratum is locally relatively much subsidence. Cyclic loading by situated several tens of metres higher than in the ice sheets resulted in unequal compaction the adjoining areas (see cross-section I-J in Fig. of the sedimentary succession. The compac- 4). These facts seem to indicate that vertical up- tion was stronger on the western side due to ward movements dominated in the southern the thicker sedimentary cover. As a result, the part of the intermediate zone. In the northern individual Pleistocene successions on the west- region, the top-Neogene is situated in some ern side are situated at lower altitudes. areas about 100 m lower than the average for Ice-sheet retreat caused relatively much ver- the adjoining areas. The Pleistocene succes- tical glacioisostatic uplift on the western side. sion includes there thick glaciolacustrine and This gave rise to intense erosion and resulting lacustrine series that are absent in other areas stratigraphic gaps in the Warmia province. (cross-section E-F in Fig. 4). The upper depos- The intermediate zone was subjected to sig- its contain reworked Miocene and Oligocene nificant vertical movements, indicating strong material, indicating strong erosion of the sub- neotectonic activity at the boundaries of struc- stratum that occurs nearby at high altitudes. tural units in the basement. The movements Subsidence thus dominated in the north of the were induced by cyclic advances and retreats intermediate zone, although there was locally of the Pleistocene ice sheets. a simultaneous strong uplift of the substratum. Geophysical investigations and borehole References data prove the occurrence of numerous vertical discontinuities in the intermediate zone Ber, A., 2000. Pleistocene of north-eastern Poland and neighbouring areas against crystalline and (Morawski, 2009d-this issue). They most likely sedimentary basement. Prace Państwowego Instytutu follow the orientation of intermediate zone Geologicznego 170, 89 pp. axis. Vertical (stepwise) tectonic movements Ber, A., 2006. Peistocene interglacials and glaciations of of blocks occurred along the discontinuities. northeastern Poland compared to neighbouring areas. Strike-slip movements cannot be precluded, Quaternary International, 149, 12–23. Boulton, G.S., Dolgenmans, P., Punkari, M., Broadgate, either. Tectonically active intermediate zone M., 2001. Palaeoglaciology of an ice sheet through probably existed in the same position through- a glacial cycle: the European ice sheet through the out the whole Pleistocene; it was repeatedly Weichselian. Quaternary Science Revievs 20, 591–625. reactivated during successive glaciations. Ver- Gagel, C., Müller, G., 1897. Die Entwickelung der Ost- preussischen Endmoränen in den Kreisen Ortelsburg tical movements of blocks occurred within the 250 Wojciech Morawski

und Neidenburg. Separatabdruck aus dem Jahrdbuch landforms and glaciotectonic deformations near der Königl. Preuss. Geologischen Landesanstalt für Kronowo (western Mazury, Poland). Geological 1897. Berlin. Quarterly 47/4, 339–356. Houmark-Nielsen, M., Kjoer, K.H., 2003. Southwest Morawski, W., 2005a. Warmińska prowincja paleoge- Scandinavia, 40–15 kyr BP: palaeogeography and ograficzna plejstocenu (południowo-wschodnia Pol- environmental change. Journal of Quaternary Science ska) (The Warmia palaeogeographic province of the 18, 769–786. Pleistocene, north-eastern Poland). Przegląd Geologic- Kasprzak, L., Lisicki, S., 1999. Szczegółowa mapa geolog- zny 53, (6), 477–488. iczna Polski w skali 1:50 000 arkusz Kobułty (Detailed Morawski, W., 2005b. Reconstruction of ice sheet movement Geological Map of Poland, 1:50,000, sheet Kobułty). from the orientation of glacial morpholineaments Państwowy Instytut Geologiczny. (crevasse landforms): an example from northeastern Kenig, K., 1998. Petrogaficzne podstawy stratygrafii Poland. Geological Quarterly 49/4, 403–416. glin morenowych Polski północno-wschodniej Morawski, W., 2009a. Szczegółowa mapa geologiczna (Petrographic foundations of till stratigraphy of Polski w skali 1:50 000 ark. Biskupiec (Detailed northeastern Poland). Biuletyn Państwowego Instytutu Geological Map of Poland, 1:50,000, sheet Biskupiec). Geologicznego 380, 1–99. Polish Geological Institute. Kotański, Z., 1977. Rozwój paleotektoniczny wyniesionej Morawski, W., 2009b. Szczegółowa mapa geologiczna części starej platformy w Polsce w wałdaju i w Polski w skali 1:50 000 ark. Dźwierzuty. (Detailed kambrze. (Palaeotectonic development of the uplifted Geological Map of Poland, 1:50,000, sheet Dźwierzuty). part of the old East European platform in Poland, Polish Geological Institute. during the Valdaian and the Cambrian) Biuletyn Morawski, W., 2009c. Objaśnienia do Szczegółowej mapy Instytutu Geologicznego 303, 15 – 40. geologicznej Polski w skali 1:50 000 ark. Dźwierzuty Książkiewicz, M., Oberc, J., Pożarski, W., 1974. Mapa (Explanations to Detailed Geological Map of Poland, tektoniczna Polski (Tectonic Map of Poland), 1:50,000, sheet Dźwierzuty). Polish Geological Wydawnictwa Geologiczne. Institute. Lisicki, S., 2003. Litotypy i litostratygrafia glin Morawski, W., 2009d. Neotectonics induced by ice-sheet lodowcowych plejstocenu dorzecza Wisły (Lithotypes advances in NE Poland. Geologos, 15, 199–217 (this and lithostratigraphy of tills of the Pleistocene issue). in the Vistula drainage basin area, Poland). Prace Morawski, W., 2009e. A reconstruction of the Vistula ice Państwowego Instytutu Geologicznego 177, 1–105. stream during the last glaciation. Geological Quarterly Mańkowska, A., Słowański, W., 1968. Mapa Geologiczna 53/3, Polski 1:200 000, arkusz Olsztyn (Geological Map of Punkari, M., 1997. Glacial and glaciofluvial deposits in Poland, 1:200,000, sheet Olsztyn), Polish Geological the interlobate areas of the Scandinavian Ice Sheet. Institute. Warszawa. Quaternary Science Revievs 16, 741–753. Mańkowska, A., Słowański, W., 1980. Objaśnienia do Roman, M., 2008). Rekonstrukcja kierunku ruchu lądolodu Mapy Geologicznej Polski 1:200 000, arkusz Olsztyn lobu Wisły w obszarze Pojezierza Kujawskiego (Explanations to Geological Map of Poland, 1:200,000, i Kotliny Płockiej (Reconstruction of ice flow directions sheet Olsztyn) Polish Geological Institute, Warszawa. of the Vistula ice sheet lobe in the Kujawy Lakeland Morawski, W., 1984. Osady wodnomorenowe (Watermo- and the Płock Basin area). Acta Geographica Lodziensia rainic sediments). Prace Instytutu Geologicznego 58, 74 93, 67–85. pp. Warszawa. Słodkowska, B., 2009. Palynology of the Palaeogene and Morawski, W., 1985. Pleistocene glacigenic sediments of Neogene from the Warmia and Mazury areas (NE the watermorainic facies. Quaternary Studies in Poland Poland). Geologos, 15, 219–234 (this issue). 6, 99–116. Stokes, C.R, Clark, C.D., 2001. Palaeo-ice streams. Morawski, W., 1989. Watermorainic sediments: Origin Quaternary Science Reviews 20, 1437–1457. and classification. [In:] R.P. Goldthwait, C.L. Matsch Tyski, S., 1974. Obszar wyniesiony platformy wschodnio (Eds): Genetic Classification of Glacigenic Deposits 143– europejskiej. [In:] W. Pożaryski (Ed.) Budowa 144. Balkema. Rotterdam/Brookfield. geologiczna Polski. Tektonika, 1. Niż Polski. Wydawnictwa Morawski, W., 2001. Szczegółowa mapa geologiczna Geologiczne, Warszawa. Polski w skali 1:50 000 ark. Jeziorany (Detailed Wysota, W., Molewski, P., Sokołowski, R.J., 2009. Record Geological Map of Poland, 1:50,000, sheet Jeziorany). of the Vistula ice lobe advances in the Late Weichselian Polish Geological Institute. glacial sequence in north-central Poland. Quaternary Morawski, W., 2003a. Objaśnienia do Szczegółowej mapy International 30, 1–16. geologicznej Polski w skali 1:50 000 ark. Jeziorany (Explanations to Detailed Geological Map of Poland, 1:50,000, sheet Jeziorany). Polish Geological Institute. Manuscript received 15 September 2008; Morawski, W., 2003c. Reconstruction of ice-sheet movement from the orientation of linear glacial revision accepted 21 October 2009.