Origin and age of the large-scale glaciotectonic structures in central and eastern Poland

A N N A L E S S O C I E T A T I S G E O L O G O R U M P O L O N I A E R O C Z N I K P O L S K I E G O T O W A R Z Y S T W A G E O L O G I C Z N E G O

55/3 - 4 : 3 0 7 - 332 K ra k ó w 1985

H a n n a Ru s z c z y ń s k a- Sz e n a j c h

ORIGIN A N D AGE OF THE LARGE-SCALE GLACIOTECTONIC STRUCTURES

IN CENTRAL A N D EASTERN POLAND

Geneza i wiek wielkoskalowych struktur glacitektonicznych w środkowej i wschodniej Polsce

Hanna R u s z c z y ń s k a - S z e n a j c h : Origin and age of the large-scale glaciotectonic structures in central and eastern Poland. Ann. Soc. Geol. Poloniae, 55/3 — 4: 3 0 7 -3 3 2 , 1985 Kraków.

A b s t r a c t : The dominating genetic kind of the large-scale glaciotectonic features in central and eastern Poland is represented by squeezed-up end moraines which are mainly composed of local substratum material and are often accompanied in their proximal sides by corresponding depressions being source zones of the squeezed-up sediments. The push-forward end moraines and other features pushed frontally by glacial ice, which do not contain material from beneath, are much scarcer in the area discussed. The glaciotectonic features occur in all the successive glaciogenic horizons. The di­

mensions of deformations - in areas characterized by the occurrence of thick soft substratum - point to the thickness of corresponding disturbing ice, while their directional features give evidence concern­

ing the direction of the ice flow. However, the latter data show also the dependence on the buried hard bedrock which influenced the geometry of the deformations.

K e y w o r d s : glacial tectonics, glaciotectonic structures, glaciotectonic processes, glaciotec­

tonic transport, Pleistocene, Poland.

H anna R u s z c z y ń s k a - S z e n a j c h : Department o f Geology, Warsaw University, al. Żwir­

ki i Wigury 93, 02-089 Warszawa (Poland).

manuscript received: March, 1984 accepted: September, 1984

IN TR O D U CTIO N

D uring the X IN Q U A Congress in England (1977) an idea arose — initiated by a group o f geologists working in areas reached by Pleistocene Scandinavian ice sheets and from the British Isles — to gather evidence and ideas concerning glaciotectonic features in these countries, which would facilitate some paleo-gla- ciological reconstructions.

The glaciotectonic features, however — recording the mechanical action of glacial ice upon its substratum (Ruszczyńska-Szenajch, 1983) — are very com m on in glaciated areas and show very different dimensions. So, the writer selected for the present review the conspicuous structures building separate landforms (e.g.

glaciotectonic end moraines), m arked in recent surface or buried, which she called

large-scale structures because in glaciotectonic scale they belong to the largest features. There also are considered some features (e.g. diapirs) which do not form separate landform s but they penetrate the whole or almost whole horizons o f glacial deposition. N o exact metric limit was taken to select the stuctures discussed, but their dimensions may be vaguely defined as being usually o f hundreds or tens of metres.

The following paper gives a general characteristics o f the regional distribution of large-scale glaciotectonic features in eastern and central Poland, and the dis­

cussion concerning the origin and age o f particular structures — based on published evidence (usually in the Polish language) and the au th o r’s own work.

The w riter’s intention also was to recognize the m ain genetic kinds o f the glacio­

tectonic deform ations in the area studied — with reference to her form er views based on detailed studies — and to draw preliminary paleogeographical pictures for some regions, including general suppositions concerning the movement and thickness o f the corresponding ice sheets.

The main genetic units (genetic subdivision), to which the au th o r refers in this discussion, are those recently defined by her (Ruszczyńska-Szenajch, 1979, 1983).

T he Q uaternary stratigraphic units and nom enclature are used mainly according to Różycki (1972) (to assist correlation with older publications), and in the last chapter they are correlated with newer stratigraphic subdivision (Różycki, 1978).

T he oldest link o f the Q uaternary, representing possibly the youngest Tertiary, is called in a traditional way Preglacial, and the series of the undoubted youngest Tertiary on the territory discussed, represented by variegated clays and associated deposits, is called (as in m ajority o f the publications discussed here) Pliocene, though there is now some discussion suggesting that a p art o f this series may belong to Miocene.

REGIONA L DISTRIBU TIO N A N D GENETIC CHARACTER O F GLACIOTECTO NIC FEATURES

Fo r a long time there has existed in Poland a widely accepted view that the most intense glaciotectonic deform ations were concentrated mainly in the western part o f the country, whereas in the eastern p art such features were rather scarce. How e­

ver, new exposures and m ore num erous boring data have considerably changed this opinion. The writer characterizes glaciotectonic features from this “ non- -glaciotectonic” p art of the country, which also shows distinctly m arked zones o f different-age glacial relief: from a comparatively m ature landscape in the south, corresponding to the C racovian (M indel) G laciation, to increasingly younger in northw ard direction — through zones o f the Middle Polish (Riss) units to the Vistulian (W urm) zone (Fig. 1).

F rom the area reached only by the C racovian ice sheet (Fig. 1) there are not reported conspicuous glaciotectonic deform ations examined in detail, although this ice sheet caused num erous large-scale deform ations stated in more northern sites, which are covered by younger series and will be described later.

In the area reached by the Middle Polish ice sheet during the maximal “ stadial” ,

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Fig. 1. Maximum extent of successive ice sheets in central and eastern Poland (after Różycki, 1972). C — Cracovian, MP — Middle Polish, W - W artanian, V - Vi- stulian. Localities mentioned in the text:

A - Anielinek, B — Błędowo, D - D o­

brzyń, G — Garwolin, Go — Gowarczów, Gd — Gdańsk — Gdynia, G r — G óra Kal­

waria, J - Julianka, K - Kock, Ł - Łódź, Ło - Łosice, Łu - Łuków, M - Mielnik, Mi — Mińsk Mazowiecki, Mo — Mochty, O — Osieck, P — Piączyn, Pa — Pawłów, R - Rozwady, Ry - Ryki, S - Siedlce, St — Stoczek, Su - Suwałki, Sz — Szym­

bark, T — Tczew, Wa — Warszawa (W ar­

saw), W1 - Wólka Mlądzka, Wł - Wło­

cławek, Wy — Wyszogród

Jah n (1956) describes some glaciotectonic deform ations in the Lublin U pland which is characterized by the occurrence o f Cretaceous bedrock built o f limy rocks a n d covered in places by T ertiary sediments. The most conspicuous deform ations described in detail occur in Pawłów Basin (Fig. 2) — in a zone o f maximal extent o f the mentioned ice sheet. Jah n characterizes these deform ations as consisting o f two parts. The “ external” (distal) p a rt is represented by hills built o f disturbed Pleistocene and T ertiary deposits piled up at the to p of a buried slope o f consoli­

d ated Cretaceous rocks and situated in the southern rim o f the Pawłów Basin.

D ow n the slope (inclined to the north) the “ internal” (proximal) p art o f the de­

form ations occurs, represented by a belt o f disturbed morainic deposits contain­

ing squeezed-in Tertiary sediments. At the b ottom o f the Basin the Tertiary sedi­

m ents do not occur at all. According to Ja h n ’s interpretation, they were removed from there by glaciotectonic action and displaced to the south — up the Cretace­

ous slope. T hough the mechanism o f the displacement is not described in the work discussed, the characteristics o f the material and o f the geological situation in the area in question is so clear that the present au th o r would not hesitate to call these features the squeezed end moraines, which are accompanied (at their proximal side) by the glaciotectonic source zone, from where the Tertiary material had been squeezed out.

A quite different kind o f deform ation is described by Jahn in the northern part o f the Lublin U pland (Fig. 3). The disturbed series, several metres thick, is re­

presented here only by fluvioglacial deposits (containing some inclusions o f till) and covered in places by coarse residual material. Jahn interprets the deform a­

c s s R

tions as having been caused by local oscillation of the ice front during the general retreat period o f the ice sheet. T he present au th o r would add to this interpreta­

tion that the deform ations were probably formed by the pushing-forward action of the ice, resulting from its movement only, without any squeezing-out process (they do not contain substratum material). So thay may represent push-forward

Fig. 2. Glaciotectonic structures of a hill southward of Pawłów (after Jahn, 1956). I - Cretaceous, 2 — deformed Tertiary clays, 3 - till, 4 — fluvioglacial sands. The south is to the right

Fig. 3. Profile Majdan Krasieniński — Krasienin (after Jahn, 1956). 1 - stratified dusty sands, la - dusty deposits corresponding to bed “ 1” , 2 — weathered gravels and boulders (residual material), 3 —

folded fluvioglacial gravel and sand with till layers, 4 — till

moraines — according to the genetic term inology mentioned in the introduc­

tion. However, the possibility cannot be excluded th at they represent deform a­

tions originating from the melting o f glacial ice underneath the fluvioglacial de­

posits — during the process o f sedimentation or ju st after the accumulation. If this were the case they would not represent glaciotectonic features at all.

The area o f Holy Cross M ountains, stretching to the west o f the Lublin Upland, was also reached by the m axim um extent o f the Middle Polish ice sheet and was closely surrounded by the ice from the N E and N W sides (Lindner, 1971). The widespread occurrence o f consolidated rocks showing differentiated relief and covered in some zones by soft sediments a few to some tens o f metres thick, created (in these zones) good conditions for glaciotectonic activity affecting the deform ­ able substratum . The conspicuous feature o f this kind has been found SE o f G o ­ warczów; it is described by Lindner as “ push m oraine” .

Just recently a paper was published by Różycki (1982), giving a general cha­

racteristics o f glaciotectonic zones — characterized by disturbed Cretaceous deposits together with Pleistocene sediments — occurring in the region o f maximum extent o f the Middle Polish ice sheet SW o f Holy Cross M ountains. It contains a detailed description of exposure at Julianka (Fig. 1), showing deformed Albian and C enom anian sands and sandstones overlying Pleistocene sediments (loess), however the mechanism o f deform ation is not discussed in detail.

In the Łódź region, to the north-west o f Holy Cross M ountains, Dylik (1961) and K latkow a (1972) describe zones o f distinctly m arked glaciotectonic deform a­

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tions involving Tertiary and Q uaternary sediments, and corresponding to the m a­

ximal extent o f W arta ice sheet. Dylik (1961) interprets these structures as represent­

ing: a) folds formed subglacially (because they contain *till of the deforming ice sheet) o f unfrozen m aterial, and b) m onoclinal structures formed o f rigid frozen m aterial by lateral pressure. Since in m any cases these two kinds o f structures occur together, Dylik suggests an existence o f time intervals (connected with ice oscilla­

tions) separating the form ation o f the structures. The interesting descriptions of exposures, showing substratum m aterial m uch elevated above its prim ary beds, incline the present writer to interprete m ost o f these deform ations as squeezed end moraines. It seems probable th at each separate unit o f these moraines may involve different geometric elements i.e. scales (“ monoclinal structures” ) and folds, and the m entioned presence o f till o f the deforming glacier does not ne­

cessarily prove a “ subglacial” origin o f glaciotectonic structures (Ruszczyriska- -Szenajch, 1981).

K latkow a (1972) also distinguishes two kinds o f deform ations: 1) “ fold struc­

tures” , which she identifies with diapirs, and 2) “ monoclinal structures” , includ­

ing scales. The form er were exposed in fragments only (e.g. Fig. 4), so their geo­

metry may be a point o f discussion, as well as their diapiric origin. The “ m ono­

clinal structures” are characterized in the discussed work as the m ost widespread in the area discussed, striking generally N W —SE. They usually show up in frag­

ments, though one exposure offers a perfect view o f the whole scales superposed upon substratum , which is only slightly deform ed at the contact with the scales (PI. I: 1). K latkow a draws attention to the fact th at the strikes o f particular scales occurring together within a separate m onoclinal assemblage are differently oriented,

0 40 80 120 160m

Fig. 4. Exposure at Dąbrówka - Strumiany (after Klatkowa, 1972). 1 - brown coal, 2 - gray silts and clays, 3 — silty-and-clayey series, 4 — silty-and-sandy series, 5 — cross bedded, deformed sands, 6 — horizontal bed of sands interbedded with silts, 7 - unstructural sands with “ pavement” at the

bottom, 8 — humus layer

and that the direction of ice m ovement was not the only factor resulting in the orientation o f glaciotectonic structures. So, the orientation alone cannot be treated as a p ro o f o f particular direction o f ice advance. K latkow a does not characterize the mechanism o f form ation o f “ m onoclinal structures” , but the evidence she gives, and her interesting rem arks concerning the arrangem ent o f these structures allow one to suppose th at they represent squeezed end m oraines (compare the discussion in Ruszczyńska-Szenajch, in print), possibly some o f them slightly, remodelled by continued ice advance. K latkow a also m entions the possibility o f superposi­

tion o f scales onto large diapiric structures, b ut this statement — analogically to that concerning the existence o f large diapiric structures in the area discussed — needs m ore evidence (exposures) undoubtedly showing the interpreted geological situation.

In mid-eastern Poland, situated to the north o f the Lublin U pland, reached by the maximum stadial and (in the northern part) by the W arta stadial o f the Middle Polish Glaciation, the average thickness o f soft Tertiary sediments — mainly clays, silts and sands - overlying hard Cretaceous bedrock is some tens o f metres. The thickness increases to the no rth to one hundred metres and more.

Several glaciotectonic generations have been described from this area by Rusz­

czyńska-Szenajch (1976a). Com paratively dense boring data combined with sur­

face exposures allowed the au th o r to discover there and characterize a close ge­

netic relation o f squeezed-up end moraines, built o f disturbed Tertiary and Plei­

stocene sediments, to glaciotectonic source-depressions occurring behind these moraines and also filled with disturbed (squeezed-down) Tertiary and Pleistocene series (Ruszczyńska-Szenajch, 1976a: Figs. 6, 13, 27).

Older glaciotectonic generations in this area (covered by younger glacial de­

posits) are mainly represented by glaciotectonic depressions. T he largest o f them — several tens o f metres deep and some tens o f kilometres long — occur in a zone Mińsk Mazowiecki — Siedlce — Łosice (they were formed by the ice sheet o f the oldest, Podlasian, Giinz Glaciation), and in the regions o f G arw olin and Kock (formed during the Cracovian, Mindel Glaciation). The squeezed end m oraines corresponding to these depressions have usually been largely destroyed by suc­

cessive ice sheets, but the clearly m arked remains o f them are represented by large glacial rafts built o f Tertiary material and occurring m ost abundantly in the im ­ mediate forelands o f the depressions. In the region o f Stoczek the younger (?) glacio­

tectonic generation in the area (of M iddle Polish, Riss Glaciation?) has been as­

certained. The squeezed end moraines o f this age occur at the recent surface (PI. II).

The squeezed end m oraines accompanied by glaciotectonic source-depressions constitute the m ajority o f known glaciotectonic features in m id-eastern Poland.

In most cases the disturbed material o f the substratum has lost its contact with prim ary beds, and occurs now as glacial rafts. Hence, the au th o r concludes th at some large glacial rafts found in separate borings may suggest (though not prove) the existence of buried glaciotectonic features. This subject will be also discussed later.

N ear the eastern periphery o f Poland, in the Łosice region, N ow ak (1977)

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described a zone of “ pushed” moraines, characterized by clearly m arked topogra­

phic expression, corresponding to the W arta stadial. She also describes older glaciotectonic deform ations in this region — formed during the Cracovian Glacia­

tion and during maximal stadial o f the M iddle Polish Glaciation — which are now represented by the buried glacial rafts. The mentioned author does not explain the process o f form ation o f the “ pushed” m oraines, but their geological structure — represented mainly by disturbed Tertiary and soft Cretaceous deposits — strongly suggests their origin as squeezed end moraines. The geological sections enclosed in the paper discussed (e.g. Fig. 5) m ay also suggest the occurrence o f glaciotec­

tonic depression there. Such depression has already been stated previously (Rusz-

Fig. 5. Geological section in Łosice region (after Nowak, 1977). K - soft Cretaceous deposits, Ol + E - Eocene and Oligocene sands and silts, M - Miocene sands and silts, Q — Quaternary tills, sands and

silts

czyńska-Szenajch, 1976a) and confirmed by new investigations (Michalski, 1980).

Besides the large ice-marginal features, N ow ak also describes in the Łosice region the occurrence o f “ esker-like” and “ kame-like” hills, and she interpretes them as having been formed due to the squeezing o f soft substratum into crevasses within the ice.

In the region o f the lower Bug River, Straszewska (1968) mentions some glacio­

tectonic deform ations, usually buried and corresponding to Middle Polish Glacia­

tion, but she gives no detailed characteristics o f them.

Interesting d ata have been published by Riihle and Zwierz (1961) from the re­

gion of Mielnik on the Bug River. The authors analysed boring data, and they find (on a distance o f some kilometres) 3 — 4 “ protrusions” built of soft Cretace­

ous deposits and “ piercing” through more than 100 m o f Q uaternary series. The authors interpreted those features at th at time (1961) as originated from fluvial erosion, but this interpretation m et considerable discussion and the present au th o r w ould rather consider the features as representing the results o f glaciotectonic squeezing-up processes.

In the north-eastern part o f Poland, i.e. in Suwałki Lake District reached by the Vistulian (Wiirm) Glaciation, Ber (1974) describes num erous hills of glaciotectonic origin formed during the Pom eranian stage o f this glaciation. The mentioned au th o r — dealing mainly with stratigraphic questions — calls the hills pushed moraines and squeezed m oraines but he gives no criteria of such differentiation and he does not discuss in detail either the structure or the origin o f these features.

Probably the best known buried glaciotectonic structures docum ented by a lot

o f borings, occur in the area o f W arsaw. They are the subject o f most controversial views (cited below). The m ain part o f these structures occurs underneath an al­

most flat-lying till left by the W arta ice sheet, the youngest in this area. It is re­

presented by the “ elevation” (piling-up) o f Pliocene clays forming a buried ridge several km long, 1 — 2 km wide, and running generally in a N N W — SSE direction.

The ridge was already recognized by Lewiński and Różycki (1929), who gave its detailed characteristics and defined it as having been a result o f glacial tectonics, i.e. o f ice-pressure and ice-movement. The glaciotectonic origin o f the ridge was confirmed and docum ented by increasingly ab u d an t evidence in the next works (Sujkowski & Różycki, 1937; Mojski & Dom osławska-Baraniecka, 1965), though the mechanism o f form ation o f the ridge was not discussed in detail in these publica­

tions. In 1972 Różycki denied the glaciotectonic origin o f the ridge, and inter­

preted it as a fold-structure having originated from the plastic flow o f clayey masses due to upw ard m ovement o f the Kujawy anticlinorium during the G reat Inter- glacial. However, Brykczyńska and Brykczyński (1974) gave new evidence (Fig. 6) and thorough discussion concerning the ridge in question. They proved its glacio­

tectonic origin and attributed it to the so-called valley-side glaciotectonics, i.e.

to the form ation by an “ ice tongue filling the river valley and stretching onto the neighbouring upland (and) exerting a strong pressure on the valley escarpm ent”

(Brykczyńska & Brykczyński, 1974: 218). Though the glaciotectonic origin o f the ridge is nowadays widely accepted, its valley-side tectonics aspect is a point o f intense discussion because there is no satisfactory evidence o f a valley having existed here in the time o f the form ation of the ridge. The time o f the glaciotectonic form a­

tion o f the ridge is attributed by m ost o f the authors mentioned, to the m aximum stadial (preceding the W arta stadial) o f the Middle Polish Glaciation.

The other glaciotectonic structures in W arsaw occur to the north-east o f the described ridge, and are covered by fluvial series o f the recent Vistula valley. These forms are represented mainly by elongated and comparatively narrow depressions formed within Pliocene series, stretching generally N N W —SSE, whose average depts are several tens o f metres. The deepest and longest (some kilometers) de- pressional form has been defined formerly as a fluvial valley (Samsonowicz, 1927) and such a view is held m ore recently by D om osławska-Baraniecka and G ad o m ­ ska (1965). In other works this form is characterized as a kind o f syncline being either o f tectonic (Lewiński, 1929; Różycki, 1972) or glaciotectonic origin (Suj­

kowski & Różycki, 1937; Brykczyńska & Brykczyński, 1974). The geological d o ­ cum entation for the area o f W arsaw given by Dom osławska-Baraniecka and G a ­ dom ska (1965: PI. 1 2 - 1 6 ) does not show characteristic fluvial infill o f any p art o f this depressional form, and it shows infills mostly o f glaciogenic and cold- -lacustrine type. It also does not show the characteristic “ synkline” structure of the depression because o f the very irregular occurrence o f deposits o f different

age and origin forming the infill. However, the docum entation m entioned gives (for the discussed depressional form) some perfect examples o f infills o f glacio­

tectonic source-depressions. Besides this largest depressional form there exist others which are either shallower or shorter and which are defined by Domosław-

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ska-Baraniecka and G adom ska (1965) as having originated from glaciotectonic processes, though the authors do not discuss the mechanism o f form a­

tion o f these features.

Summarizing the above account o f d ata and opinions concerning the Tertiary “ elevation” and large depressions in the area o f W arsaw, it seems m ost probable — in the present a u th o r’s opinion - th a t the form er represents buried squeezed end- -morainic ridge, and the latter (at least in some parts) are glaciotectonic source depressions from which the m aterial o f this ridge has been squeezed-out.

Depressions filled with lacustrine series are o f rather different origin.

The age o f the glaciotectonic features, ap art from their different genetic interpretations, is m ost often defined by the cited authors as corresponding to the m axim um stadial o f the M iddle Polish G lacia­

tion. However, the docum entation by Domoslawska- -Baraniecka and G adom ska (1965) provides evidence for discussion o f this question. These authors define a till horizon occurring a t the south-western foreland o f the ridge and another one occurring at its north- -eastern hinterland (and directly covering the de­

pressions) as one stratigraphic unit left by the m en­

tioned stadial o f the Middle Polish Glaciation. The tills are underlain in places by waterlaid deposits defined by the authors as the equivalent o f the time interval immediately preceding this stadial. But the difference o f altitude o f occurrence o f those tills, and especially o f the to p o f underlying water- laid deposits, is abo u t 30 m in a distance no t exceed­

ing a few kilometers. So it seems probable that the till occurring much lower and covering the depressions at the hinterland o f the ridge belongs to the older, i.e. Cracovian (Mindel) Glaciation.

In such a case the main squeezing process would have been connected with an oscillation o f ice front during the retreat period o f the ice sheet o f the C ra­

covian G laciation, and the ice did not override its squeezed m oraines (no Tertiary rafts within the C ra­

covian till at the foreland o f the ridge). The next ice sheet, o f the m axim um stadial o f Middle Polish Glaciation, overrode the well expressed ridge and

produced ab u d an t Tertiary rafts o f smaller dimensions occurring within the till o f this age at the foreland o f the ridge (as illustrated by the docum entation m en­

tioned).

In the south-eastern environs o f W arsaw, glaciotectonic deform ations have also been found, m ost o f them covered by till (or tills) o f Middle Polish Glaciation.

A known locality is W ólka M lądzka, where Pliocene clays and “ Preglacial” series are considerably elevated and disturbed. They are described by Browkin-M ar- kulis (1967), and interpreted by this au th o r as representing glaciotectonic deform a­

tions formed by the ice sheet during the Middle Polish Glaciation. Baraniecka (1975) interprets these same deform ations (and the W arsaw Pliocene ridge as well) as having been caused by other tectonic (not glacio-tectonic) processes. N ever­

theless, close resemblance o f these structures to the nearby buried squeezed m oraines in south-eastern M asovia (Ruszczyńska-Szenajch, 1976a) as well as their geological position make the opinion o f Browkin-M arkulis m ore probable.

O ther glaciotectonic sites in the south-eastern environs o f W arsaw, where disturbed series often form ing glacial rafts have been exposed, are those at G ó ra K alw aria and Osieck, described by Sarnacka (1965). This au th o r gives interesting examples o f deform ations, whose age she ascribes to the Middle Polish Glaciation (to the m aximum stage and the W arta stadial), bu t she does not pay m uch atten ­ tion to the interpretation o f the m echanism o f form ation o f these features. In the present writer’s opinion, these deform ations — especially those at Osieck, cha­

racterized by the occurrence of elevated large masses o f Tertiary m aterial covered by till — may represent squeezed m oraines overridden by ice. When covered by the ice sheet, the flattened and attenuated squeezed moraines m ay have been subjected to additional deform ations and secondary detachm ent o f their m aterial, what have resulted in the form ation o f frequent glacial rafts o f smaller dimensions.

Nevertheless the genetic interpretation is difficult here, because o f the lack o f ge­

neral geological section showing the relation o f disturbed series to their substratum and to the surrounding strata, and — as pointed out already by Sarnacka — be­

cause o f the lack of exposures cutting the features discussed; in a direction parallel to the previous ice movement.

Perhaps the m ost conspicuous deform ations o f Q uaternary and Tertiary de­

posits in central Poland (described in m any works) are those exposed along the northern steep escarpm ent o f the Vistula valley. The best known localities are:

Mochty, Wyszogród, and the region o f D obrzyń — Włocławek.

The deform ations at M ochty are exposed on a segment about 2 km long. They are mainly within the “ M ochty till” horizon, several metres thick (truncated by younger series), described in a detailed way by Różycki (1970). Różycki interprets these deform ations as having been formed underneath the moving ice sheet during the accum ulation o f the till correlated by him with Cracovian (Mindel) horizon.

He calls the deform ations dynamic structures, not glaciotectonic ones. T he cited paper was one o f the first works in Poland drawing attention to m any aspects of structural features o f tills, and to processes responsible for the form ation o f these features. In the period o f m ore than ten years which has elapsed since the publica­

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tion o f this paper, a lot o f new evidence and ideas concerning tills and glacial tec­

tonics has been published. According to these new works many details o f the M ochty profile m ay be interpreted in a way different from th at o f 1970, but the main idea o f Różycki - the form ation o f the discussed horizon underneath m oving ice — still remains valid. The present writer would n ot hesitate today to call the struc-

Fig. 7. Deformation of the younger till at Wyszogród. The section, within the Vistula escarpment, is about 20 m high (after Rusz-

czyńska-Szenajch, 1976b)

tures at M ochty, glaciotectonic deform ations — produced, as already explained by Różycki, underneath a moving ice sheet and synchronous with the accum ula­

tion o f deformed till.

A t W yszogród two till horizons build the escarpm ent 20 — 30 m high, and they are well exposed over a distance o f abo u t 2 km, showing different kinds of deform ations (Fig. 7). According to the latest interpretation given by the writer (Ruszczyńska-Szenajch, 1976b) the escarpm ent cuts here - unfortunately not in a transverse way — a glaciotectonic source depression filled partly with older till b ut mainly with lodgement till o f the younger horizon (Fig. 8; PI. III). So, the deform ations had m ost probably been form ed beneath the frontal p art o f advanc­

ing ice sheet. They are, in general, o f the same age as the younger till, i.e. they cor­

respond to the W arta stadial o f the Middle Polish Glaciation.

The exposures o f the Vistula escarpm ent at D obrzyń and westward o f W ło­

cławek — in the area reached already by the youngest glaciation — show deform a­

tions o f large dimensions (tens o f metres) o f the Tertiary and old-Pleistocene series, which are covered by younger Pleistocene glacial deposits. The deform ations are often called folds, b ut in some cases they m ay represent large scales (thrust sheets) often dipping (generally) to the n o rth (e.g. Figs. 9, 10).

Fig. 8. Geological section transverse to the Vistula river escarpment (esc.) at Wyszogrod, showing two tills separeted with waterlain sands and silts. The younger till in the vicinity of escarpment is composed of two genetic horizons, i.e. deformed lodgement till covered by melt-out (and flow) till - shown also

on PI. I ll (after Ruszczynska-Szenajch, 1976b)

The origin o f these structures was attributed to tectonic processes by some authors (Lewiński, 1924; Ber, 1960; Różycki, 1972) but in w orks based on exam ina­

tion o f the whole neighbouring territory (Skompski, 1969) or upon detailed struc­

tural analysis (Jaroszewski, 1963; Brykczyński, 1982) they are interpreted as glacio- tectonic structures. Jaroszewski (1963) attributes them to end-morainic zone, formed most probably by the ice sheet of Cracovian Glaciation. In agreement with th at view,

Fig. 9. Glaciotectonic scales (“ łuski” ) com­

posed of Miocene (M) and Pliocene (PI) sediments in Dobrzyń region (after Skompski,

1969'

and in accordance with the term inology accepted in this paper, the writer would call the D obrzyń — Włocławek structures squeezed end m oraines (buried), because the disturbed Tertiary masses are situated much higher than the parent Tertiary series occurring in situ. A different interpretation o f these structures was recently given by Brykczyński (1982), who considers them to be a result o f valley-side glacial tectonics (referring to B anham , 1975), i.e. caused by a glacial “ tongue” advancing to the east along a paleo-valley o f large river, regarded by Brykczyński as paleo- -Vistula. M ain objections against such view, discussed during the meetings of the Polish Geological Society in 1980 and 1981, are: 1) the Tertiary masses derive from horizons deeper than those cut by the buried valley escarpm ents in that p art o f the country (Ruszczyńska-Szenajch), 2) a lack o f corresponding (in age) sediments o f large river in the area in question (Skompski), 3) the orienta­

tion o f the glaciotectonic structures in some parts o f the exposures may point to the glaciotectonic impact from N E, i.e. from the direction opposite to th at inter­

preted by Brykczyński (Skompski). By now, the problem rem ains open, though the m ajority of Q uaternary geologists, cannot accept the idea o f a comparatively narrow glacial tongue in lowland area, where known paleogeographic data deny such possibility.

In the area stretching north o f the parallel segment o f the Vistula valley, the push-forward end moraines have been stated at Piączyn (Rusz­

czyńska-Szenajch, 1979, 1981). They are mainly built of ice-marginal fluvioglacial series, and do

Fig. !0. D istu rb e d Miocene sediments, exposed in the Vistula river escarpem ent at D obrzyń. A d ra w in g from p h o to g r a p h

— 319 —

not show any trace o f material squeezed out from beneath. They correspond to the W kra stadial — the one following the W arta stadial o f Middle Polish Glacia­

tion.

M uch older, usually buried, glaciotectonic structures have been described in the region o f N orthern M asovia by M ichalska (1967). The au th o r mentioned does not characterize the features in detail n or does she analyse the mechanism o f their form ation, but she m entions squeezing as a process responsible for the existence o f some “ elevations” o f Tertiary series. Michalska attributes the age o f these deform ations to the Podlasian (Giinz) and the Cracovian Glaciation.

Interesting evidence concerning glaciotectonic features is reported from the central part o f northern Poland, i.e. from the region adjacent to the lower Vistula valley, which was reached by the youngest glaciation. M uch o f this evidence is published by G alon (1961) and co-authors, who describe glaciotectonic “ push”

(or “ th rust” ) m oraines corresponding to the mentioned glaciation, e.g. at Bl?- dowo, Szymbark and Tczew (PI. I: 2). The cited book includes also numerous

Fig. 11. G eology o f G d a n s k region, w ith o u t the Q u a te r n a r y f o r m u i o n s (after Mojski, 1979). / - M i o ­ cene, 2 ^— Eocene (?) and Oligocene, 3 ^— Paleocene, 4 — C a m p a n ia n , 5 — c o n to u r lines o f the sub- -Q u a te rn a ry surface, 6 ^- e scarp m en ts o f different origin, 7 - glacial rafts o f the s u b s tra tu m sedi­

ments, within the Pleistocene deposits

descriptions o f large glacial rafts composed o f the Pliocene, Miocene, Oligocene and even Cretaceous deposits. Some o f these rafts are connected with glaciotec­

tonic end m oraines (e.g. Oligocene raft at Bytów), indicating their squeezed-up origin, and others are usually vaguely referred to glaciotectonic action, though the m echanism itself is not discussed in this publication.

Very interesting features were described by M ojski (1979) from the G dańsk region. This au th o r found there a buried escarpment, abo u t 100 m high, built mainly o f soft Miocene deposits and in places “ dissected” by “ valleys” filled with till containing num erous T ertiary rafts. T he escarpm ent (situated in a zone o f the Holocene Baltic Sea cliff) represents a very steep eastern and north-eastern slope o f a narrow chain o f buried M iocene elevations with their top-surface si­

tuated about 40 m higher th an the adjacent (to S and W) top-surface o f Miocene series in the surrounding area (Fig. 11). All these features are docum ented by hun d ­ reds o f borings and also by some exposures. However, the reader is in a somewhat difficult situation, because M ojski uses different expressions for the same fea­

tures (o f buried escarpm ent) in different p arts o f the work, interpreting them as

“ glaciotectonic” or “ glacio-erosional” (Mojski, 1979: pp. 17 — 21), and he does not differentiate clearly between these two groups o f processes. So, the subject provokes a discussion.

In the w riter’s opinion the narrow chain o f the highest Miocene elevations in G dańsk region (Fig. 11) represents buried squeezed moraines. The Miocene sediments were squeezed ou t from N E an d superposed on the undisturbed M io­

cene series at the front o f the ice sheet. As the squeezed sediments are alm ost iden­

tical from a lithological p oint o f view with those occurring in situ, they seem rfow to form a continuous series, and their differentiation on the basis o f boring d ata is really a very difficult task. Nevertheless, the com parison o f this elevated chain with detailed characteristics given by M ojski for successive Miocene horizons, concerning their thickness an d height, strongly suggests a secondary superposi­

tion o f the “ elevations” . O f course, paleobotanic o r another detailed stratigraphic analysis is urgently needed in such a case. However, other published examples in the area discussed show large masses o f Miocene deposits thrust also over Q u a­

ternary series or “ interbedded” with them (Pazdro, 1960), and thus represent­

ing large glacial rafts produced m ost probably by squeezing processes. T he a b u n ­ dance o f Tertiary (mainly Miocene) rafts in the zone discussed has also been stressed by Mojski.

The writer’s brief excursion to the cliff exposure in G dynia-O rłowo adds also new d ata to the above discussion. The exposure (PI. IV) reflects, in the w riter’s opinion, the squeezing-up process of the Miocene and Pleistocene sands (“ layer”

1), and partly o f the (most probably) subglacial lodgement till (“ layer” 2a), from under the frontal part o f the ice. These processes are recorded here in form o f m elt-out till with well preserved basal debris bands up-turned during the squeez­

ing process (“ layer” 2b). The interpretation o f the process is based on a very close analogy o f the exposure in question to the exposure at Kazimierz, north o f G dy­

nia, examined in m ore detail (Ruszczyńska-Szenajch, 1981). The stratigraphic

— 321 —

position of the till exposed in the part of Orłowo cliff illustrated by PI. IV is m ost probably o f M iddle Polish (Riss) age — according to Mojski (1979; Fig. 4). So, this was the time o f the (most?) intense glaciotectonic action here.

T he quoted evidence supports the above opinion concerning the squeezing-up o f the redeposited Miocene masses in the discussed area, and the adjacent G ulf o f G dańsk represents the m ain possible source zone from which the Tertiary sedi­

m ents have been squeezed-out by dynam ic pressure o f the advancing ice front.

So, the G u lf is primarily a glaciotectonic depression — o f probably younger Plei­

stocene age — which then underw ent changes caused by other processes.

In some geological publications concerning Polish Lowlands glaciotectonic questions are discussed in an interesting but very general way, e.g. Liszkowski (1975), Michalski (1979). There are also very num erous works dealing mainly with other Q uaternary subjects, and discussing only some glaciotectonic examples e.g. Baraniecka (1975, 1979), Różycki (1972) and many, m any others. In other words — there hardly exists any publication on regional o r stratigraphic Plei­

stocene problems in the Polish Lowlands which does not present some glacio­

tectonic examples. The conclusion is th at glaciotectonic deform ations are very widespread in Poland — both in surface features and in older, buried glacio- genic series. Those buried features are m ost comm only described as glacial rafts, some o f them tens o f meters thick. M any authors do not attribute the origin o f such rafts to glaciotectonic processes, usually n ot discussing their origin at all, bu t some o f the authors — as already m entioned before — point this relation in a general way. A m ore thorough study o f both glacial rafts and glaciotectonic structures (Ruszczyńska-Szenajch, 1976a) reveals close genetic connection between some o f these features, and this undoubtedly adds considerable num ber of sites characterized by (or at least suspected of) the occurrence o f glaciotectonic struc­

tures.

SUCCESSIVE STRATIGRAPH IC G EN ERATION S OF GLACIOTECTONIC DEFORM A TION S, A N D SOME PROBABLE DY N A M IC FEATURES

OF TH E C O R R ESPO N D IN G ICE SHEETS

Glaciotectonic features occurring at the surface in the area discussed usually correspond to the latest ice sheets in particular zones. Hence, in general, the age o f these surface features may be read from the m ap showing the m axim um extent o f successive ice sheets. However, new geological evidence shows an increasingly com m on occurrence o f buried glaciotectonic deformations. Quite numerous regions exist (e.g. M asovia and Podlasie) where two o r m ore glaciotectonic h o ­ rizons occur within geological profiles, and they are separated from one another by undisturbed series. The buried glaciotectonic features are often shown in ex­

posures but a lot o f them are found only in borings. The latter present most diffi­

cult problems, when determining their age as well as their genetic character, be­

cause the structural and glacio-sedimentological studies are very restricted in such cases, and the stratigraphy itself m ay be also examined only in a general frame.

Besides the difficulties m entioned above in defining the age o f some glacio­

tectonic deform ations, there also exists a serious difficulty in the stratigraphic correlation o f particular surface and subsurface features which have been studied by different authors and at different times. The writer has tried to group the deform a­

tions — basing on the existing literature and her own works — into m ain strati­

graphic horizons corresponding to the m ain glacial periods in central and eastern Poland, but the resultant sequence must be treated as a very approxim ate picture.

It m ust also be stressed th at one cannot yet be sure that particular glacial units described from southern, middle and northern Poland correspond to one another w ithout any doubt. The names o f the main glacial units (glaciations and stadials) are mainly used after Różycki (1972) and they are supplemented with the terms according to Różycki (1978).

The oldest generation o f glaciotectonic deform ations is connected with the oldest series o f lowland glaciations corresponding to the Podlasian i.e. Narevian Glaciation (Giinz), whose ice sheet in m id-eastern Poland extented roughly to the parallel of Warsaw. The deform ations (and the whole glacial series o f this age) occur at a considerable depth o f several tens o f metres; they are covered every­

where by younger deposits and are docum ented by borings. The largest deformed zones o f this age are represented by depressions elongated in a general E —W direction in the region o f M ińsk Mazowiecki — Siedlce - Łosice (Fig. 1). They are interpreted by the writer as glaciotectonic source depressions of the squeezed end moraines, formed in the frontal zone o f the oldest advancing ice sheet (Rusz- czyńska-Szenajch, 1976a). The depressions and their fillings are preserved very well, while the corresponding squeezed moraines are largely destroyed and are represented only by scarce Tertiary rafts occurring within the glacial series dis­

cussed. The subsurface deform ations attributed to the glaciation in question were also reported from N o rth ern Masovia by Michalska (1967).

The dimensions of the deform ations o f Podlasian Glaciation, especially glacio­

tectonic source depressions several tens o f metres deep, point to a comparatively

“ strong” — thick and fast moving — ice sheet, even in the zone very close to its maximum extent i.e. in the zone M ińsk M azo w ieck i-Ł o sice. The direction of E — W elongated source depressions may suggest the ice advance (almost) straight from the north in this region (com pare Ruszczyńska-Szenajch in print).

The next (younger) glacial horizon in Poland has usually been attributed to the Cracovian Glaciation (Mindel) also called the South Polish Glaciation. This horizon shows clear bipartition, especially in southern Poland, which is inter­

preted as having resulted from glacial accum ulations corresponding to the two stadials, or even two separate glaciations, within the period mentioned (Różycki, 1972, 1978). These two units have recently been called N idian (the older unit) and Sanian (the younger unit).

Glacial series of the older unit (Nidian) contains in M asovia and Podlasie fillings o f depressional source zones, occurring behind glaciotectonic end moraines, which (moraines) are represented by large Tertiary rafts in the regions o f G a r­

wolin, Łuków, and south-west o f K ock (Ruszczyńska-Szenajch, 1976a, 1978).

3 2 3 -

Both glaciotectonic features are known from borings only. The largest depression, near G arwolin, is m ore than 100 m deep and stretches in a N E —SW and N N E — SSW direction (Ruszczyńska-Szenajch. 1976a: Fig. 26). The depth points to com ­ paratively thick and active ice, and the direction (together with the location of the glacial rafts) may suggest an ice flow directed to SE and ESE. However, the direction o f the G arwolin depression m ay have been strongly controlled by the configuration o f Cretaceous m arls underlying soft Tertiary sediments subjected to squeezing processes. This control m ay be deduced from the very close p ro­

ximity of the whole depression to the buried Cretaceous slope facing N W and W N W (Ruszczyńska-Szenajch, 1976a: Fig. 25). In this situation the ice advanc­

ing in an alm ost straight line to the south may have formed the feature o f very similar shape.

A southward, and even south-westward, direction o f the ice flow is also sug­

gested by the stretching o f a source depression at Łuków and its relation to the squeezed-up T ertiary rafts (Ruszczyńska-Szenajch, 1973).

The depressions situated south-west o f Kock (documented by a few borings only) are shallower ( 2 0 - 4 0 m) and much smaller than th at at Garwolin. They stretch approxim ately E — W (Fig. 12), and show a close relationship to the squeezed T ertiary rafts occurring immediately south o f them (Ruszczyńska-Szenajch, 1978).

So the ice m ovem ent was directed here m ost probably from the no rth to the south, and the ice sheet was probably m uch weaker than in the more northern Garwolin region.

Small and shallow (several metres) glaciotectonic depressions, connected m ost probably with the older series o f the Cracovian Glaciation, have also been found at Ryki (Ruszczyńska-Szenajch, 1978; Fig. 12). The N W —SE direction o f their axes, and the occurrence of squeezed-up Tertiary material immediately to SW of them, may point to a south-western movement of the ice in this place.

It is probable th at glaciotectonic features occurring south-west o f Kock and at Ryki have been formed by a large ice lobe moving south-ward; and the Ryki re­

gion was situated in the south-western flank o f the lobe. Both regions occur quite near to the line o f m axim um extent o f the ice sheet in question. It seems most probable th at this ice sheet has been rather weak in its frontal p art during the time o f m axim um reach in the area discussed.

The “ older stadial” age o f the C racovian Glaciation is also attributed to the D obrzyń — Włocławek deform ations (Skompski, 1969). The m ovem ent o f the disturbing ice has been defined by this au th o r as directed there from N E to SW (Fig. 9). Both questions (the age, and the direction o f ice flow) have recently been strongly argued by Brykczyński (1982), who attributes the deform ations — as already discussed above — to valley-side glacial tectonics caused by a younger

“ ice tongue” moving down the form er Vistula valley. The D obrzyń — Włocławek structures represent large (tens o f metres) glaciotectonic features, and they are comparatively well exposed (Fig. 10) along the northern escarpm ent o f the recent Vistula valley, which is roughly parallel to the strike o f the structures. In spite of thorough stratigraphic works and geological m apping o f the surrounding ter-

ritory (Skompski) and a detailed structural exam ination o f the deform ations (Bryk­

czyński) opinions differ as to the direction and age o f this really strong ice respons­

ible for the deform ation.

The younger glacial unit (Sanian) o f the Cracovian Glaciation m ost probably corresponds to the m axim um ice extent in Poland. It involves also, in mid-eastern Poland, clearly m arked zones o f glaciotectonic deform ations. They are know n from borings, and are represented mainly by the fillings o f glaciotectonic source depressions, which are well preserved and comparatively well docum ented (Rusz­

czyńska-Szenajch, 1976a, 1978). T he deepest (60 —80 m) depressions occur in the region o f Garwolin, immediately north-west o f the older depression described above (Ruszczyńska-Szenajch, 1976a: Fig. 26), and in the north-western p art o f the K ock region (Fig. 12, except the small and older depressions at Ryki). All o f them show a general N E —SW stretch and point to the m ost probable north- -westerly flow o f the strong ice sheet, though the dependence o f the stretch on the configuration o f buried bedrock cannot be excluded (compare e.g. Figs. 12 and 13). M uch shallower (not exceeding 20 m) depressions, showing E —W orienta­

tion o f their axes and also corresponding to the glacial horizon in question, have been found north-east o f Kock. However, their small depth and their directions m ust have strongly depended in this area on the shallow occurrence o f top surface o f the consolidated Cretaceous rocks underlying thin Tertiary sediments — as is shown on the m aps o f top surfaces o f the Cretaceous and Tertiary series (Figs.

12 and 13).

In the previous section the writer suggests th at the age o f the main glaciotec­

tonic deform ation in W arsaw area corresponds also to the Cracovian Glaciation (younger unit) — in spite o f a generally accepted view th at it is already connected with younger glaciation. If the w riter’s interpretation o f this deform ation is cor­

rect, the fillings of source depressions several tens of metres deep and the con­

spicuous ridge o f the squeezed-up Tertiary sediments at the foreland o f the de­

pressions — both features stretching N N W —SSE — point to SW o r even W SW as being the m ost probably direction o f m ovem ent o f very strong ice. T he ice p ro b ­ ably corresponded to an oscillation during the general retreat o f the Cracovian (younger unit) ice sheet.

Besides the sites described, corresponding to the younger and older unit of the discussed glaciation, there are also reported deform ations attributed in a ge­

neral way to the Cracovian G laciation, e.g. in eastern Podlasie (N ow ak, 1977) or n o rthern M asovia (M ichalska, 1967), and they are no t discussed in this chapter.

It m ust also be stressed — once again — th a t one cannot be sure th at the older and younger units in southern, middle, and northern Poland correspond to each other w ithout any doubt. The same is true o f the units o f the younger glaciations.

The next glacial series in the territories discussed is connected with the M iddle Polish (Riss) Glaciation. It also shows two m ajor units — formerly regarded by m any researchers as stadials, and called the m axim um (or R adom ka) stadial and the W arta stadial (Różycki, 1972) — and now believed by some researchers (RÓ-

Fig. 12. Top surface of Tertiary deposits in Kock region (after Ruszczyńska-Szenajch, 1978). 7 — documentation of the top of Tertiary (and older) deposits, 2 — documentation of the top of Tertiary deposits, whose age is defined with considerable probability, 3 — documentation of the top surface of Tertiary deposits lowered by posterior processes, 4 - not reached top of Tertiary deposits by comparatively deep boring, 5 - zones of occurrence of buried squeezed

moraines, p — Pliocene, m — Miocene, ol — Oligocene, k — Cretaceous

(additional) every 5 m

- 3 2 5 -

życki, 1978, and others) to be separate glaciations, called the O dranian and W ar- tanian Glaciations respectively.

The older unit (O dranian) o f the glaciation discussed was connected with the m axim um extent o f the ice sheet at this period (Fig. 1). The ice reached the Lublin U pland, H oly Cross M ountains, and farther south-western areas. Its action there was also m arked by glaciotectonic deform ation e.g. in Pawłów Basin (Jahn, 1956;

Fig. 2), Gowarczów (Lindner, 1971) and Julianka (Różycki, 1982). In the two form er cases the ice m ovem ent was generally from the north-west to the south- -east, with m ore northerly com ponent in the Pawłów region (Jahn, 1956), and m ore westerly one at Gow arczów (Lindner, 1971). In Julianka region the ice flowed alm ost from the north-east (Różycki, 1982). However, the soft deform able sedi­

m ents form in these regions only a thin cover upon the hard bedrock whose relief m ust have strongly controlled the local directions o f the ice flow (com pare R ó ­ życki, 1982: Fig. 1). The am plitude o f the deform ed (squeezed-out?) features does no t exceed here 30 — 40 m. This is rather small in com parison with some o f the older deform ations described above, but again the shallow occurrence o f hard bedrock m akes estim ation o f ice thickness (based on the depth o f ice pressure penetra­

tion) difficult because even very thick ice could have squeezed the soft sediments only to their (shallow) bedrock.

The retreating ice sheet o f the O dranian unit o f Middle Polish G laciation showed clearly m arked oscillations which in places caused glaciotectonic deform ation, e.g. in the northern p art o f the Lublin U pland (Jahn, 1956; Fig. 3). The ice-flow here — according to the cited au th o r — was directly from n o rth to south, but a general estim ation o f the thickness o f the ice is rather difficult, because the de­

form ation — as discussed in the previous chapter — m ost probably results from a pushing-forward process and does no t show traces o f squeezing from beneath.

So it provides evidence o f an obvious forw ard movement o f the ice front during the general retreat period, bu t it tells little ab o u t the ice pressure depending on its thickness.

The ice sheet corresponding to the next, W artanian, unit o f the M iddle Polish G laciation has been known for a long time for its vigorous glaciotectonic activity in the zone o f m axim um extent, especially in western Poland. It is now clear that its behaviour in central and eastern parts o f the country has been very similar.

However, the largest deform ations o f this age in those areas are usually situated several kilometers behind the m axim um extent o f the ice, e.g. the deform ations exposed within surface features in Ł ódź region and near Łosice — discussed in previous chapter. This may point to an oscillation o f a comparatively strong ice front, following the m axim um reach o f the probably weaker ice. On the other hand, one cannot exclude the probability o f the different perm afrost conditions during the first invasion o f the ice and during its retreat period, and their influence up o n the effectiveness o f glaciotectonic processes.

The deform ations in the Ł ódź region (Fig. 4 and PI. I: 1) point to an ice m ove­

m ent from north-east to south-west (K latkow a, 1972), while near Łosice (Now ak, 1977) from north-w est to south-east. These directions are closely related to the lobe-

-shape o f the m axim um extent o f the W artanian ice (Fig. 1). This also draw s atten ­ tion to the fact that some older (buried) structures, which were formed in frontal zones, may show differentiation o f directions reflecting form er lobes o f advanc­

ing ice sheets (as previously m entioned — in connection with the older “ stadial”

o f the Cracovian Glaciation).

M ore realiable indicators o f a general direction o f m ovem ent o f larger ice masses seem to be supplied by the subglacial deform ation, often represented by syndepositional deform ation o f lodgement till. This kind o f structures has been reported e.g. from Anielinek, SE o f W arsaw, where there is evidence o f south- -eastward m ovem ent o f W artanian ice (Ruszczyńska-Szenajch, 1976a, b). H ow e­

ver, in the w riter’s opinion, the deform ations form ed underneath the m ain ice body usually are — on the contrary to the features originated in frontal zone — considerably smaller and rarely attain large-scale dimensions, and thus (in spite of their essential importance for the question discussed) they are only m entioned in this paper.

The retreating W artanian ice had shown in northern M asovia at least two m ajor advances of substage order (Różycki, 1972). The older one caused some glacio­

tectonic deform ation (after reaching its m axim um extent), e.g. pushed-forward end m oraine at Piączyn (Ruszczyńska-Szenajch, 1979). Sedimentological analysis o f the glaciogenic deposits accom panying the pushed sediments at Piączyn revealed the occurrence there o f the fossil glaciodynamic features which had been formed within the frontal p art o f the ice due to compressive flow (Ruszczyńska-Szenajch, 1981). Both glaciotectonic and glaciodynamic structures point to the south-west­

ward direction o f ice m ovem ent in th at place. In the writer’s opinion the process o f pushing-forward at Piączyn did not need a considerable thickness o f ice. This is also confirmed by a comparatively short segment o f occurrence, within a longer morainic chain, o f glaciotectonic frontal features, pointing to a very local readvance of the ice front.

A part from the glaciotectonic sites described, corresponding to the W artanian and O dranian stages, there also are deform ations, reported from central Poland, which generally are attributed to the M iddle Polish G laciation, e.g. at G ó ra K al­

waria (Sarnacka, 1956) o r W ólka M lądzka (Browkin-M arkulis, 1967). There also exists a conspicuous glaciotectonic deform ation in G dańsk is northern Po­

land — discussed in the previous section — which is attributed (Mojski, 1979) to this glaciation, and which points to the south-westward movement o f very strong ice. However, correlation between the M iddle Polish glacial units in northern and in central Poland is as yet a difficult and risky task (Mojski, 1979).

Glaciotectonic structures in the northern, p art o f central and eastern Poland are m ostly known from surface forms corresponding to the last, Vistulian G lacia­

tion, and especially to the Pom eranian stadial o f this glaciation, e.g. in Suwałki region (Ber, 1974) or in the area adjacent to the lower Vistula valley (G alon, 1961).

U nfortunately, the directional and genetic features o f the structures are seldom discussed in a systematic way in the works mentioned. This m akes estim ation of