ES 331/767 Lecture 14

James S. Aber

Table of Contents
Introduction SW Poland
Northern Poland Estonia
Ice dynamics References

Introduction to Poland

Poland and adjacent Baltic states occupy the geographic center of Europe. This region is situated entirely within the outer zone of glacial landscapes, extending from the southern Baltic basin southward to the Sudeten and Carpathian Mountains--see Fig. 14-1. The central and northern portions of Poland are underlain mainly with soft Tertiary strata resting on Cretaceous rocks. Better consolidated bedrock, ranging in age from Paleozoic to Cenozoic, is found in mountains and uplands of southern Poland. The southern mountains were deformed and uplifted by the Alpine orogeny during the early Cenozoic, and minor tectonic movements are continuing. Sedimentary basins adjacent to mountains have accumulated thick young sediment, including salt beds.

Clay mine at Jaroszów, southwestern Poland. Tertiary clay (gray) is overlain by glacial sediments (brown). Such geology is typical throughout much of central Europe between the Baltic Sea and alpine mountains. Photos ©; by J.S. Aber.
Tatra Mountains, near Zakopane, southern Poland. The Tatra Mts. are part of the Carpathian Mountain system of central Europe. The Tatras supported many small alpine glaciers during the Pleistocene, but were not reached by any advances of the Scandinavian ice sheets.

Poland was glaciated repeatedly by continental ice sheets during the Pleistocene, and small alpine glaciers existed in the Carpathian Mountains. North-flowing river systems were blocked during glaciations. Rivers and melt-water runoff were diverted to the west--North Sea, south--Black Sea and east--Caspian Sea--see Fig. 14-2. During interglacial and interstadial intervals, environmental conditions ranged from periglacial, to temperate, to subtropical.

Topography of Poland.
Wieliczka salt mine.
Tatra Mountains, Slovakia and Poland.

As a result of this complex history, Poland is almost completely mantled by Quaternary sediments of variable age, thickness, and genesis: glacial, fluvial, lacustrine, marine, and aeolian. These strata have a complicated stratigraphic arrangement. The total number of glaciations and interglaciations is not known with certainty, and there is considerable disagreement about ages and correlations of certain units.

Southwestern Poland

Southwestern Poland was glaciated by at least four major ice advances, two Esterian and two Saalian--see Fig. 14-3. The older glaciations crossed the Odra valley and terminated on the northern flank of the Sudeten Mountains. These ice advances were regionally derived from the northwest, with the exception of the Odranian which apparently came from the northeast. Local ice movement directions were much more variable. Large ice-shoved hills of the Silesian Rampart are among the most conspicuous glacial features of the region.

These hills rise >100 m above lowlands to the north and south. They are composed of deformed Tertiary strata and older glacial sediments. Trzebnica Hills, for example, are a well-known ice-pushed ridge--see Fig. 14-4. The hills rise about 100 m above the lowland to the south and around 150 m above the lowland to the north. They consist of deformed Pleistocene sediment, Pliocene gravel, and clayey strata of the Miocene Poznan Formation. These strata are thrust into a composite structure above a horst in underlying hard Triassic bedrock. Deformation of Trzebnica Hills and other ice-shoved hills of the Silesian Rampart is traditionally ascribed to the Wartanian phase of Saalian Glaciation (Aber et al. 1995). However, some geologists attribute primary deformation of the hills to older glaciations.

View over glacial foreland south of Trzebnica Hills, which are visible as the higher ridge on horizon. The hills rise about 100 m above the foreground terrain. These and similar ice-shoved hills mark the Silesian rampart in southwestern Poland.
Deformed glacial sediment within Trzebnica Hills. Laminated clay is disrupted into a breccia of broken fragments. Thrust blocks of deformed Miocene clay (Poznan Fm.) are also found within Trzebnica Hills at other sites. Photos © by J.S. Aber.

The Silesian Rampart is associated with the Odra fault zone, which continues into eastern Germany as the Fläming Rampart. The Odra faults form a complex of horsts and grabens in hard Paleozoic and Triassic bedrock below softer Tertiary strata. Ice-pushing of soft sediments took place above these buried bedrock obstacles. The Silesian and Fläming Ramparts are parts of a glaciotectonic belt that extends westward across Germany and the Netherlands, and reaches onto the North Sea floor. Ice-shoved hills of this belt vary greatly in age and genesis, but most are associated with buried hard-rock structures (Aber et al. 1995). This situation demonstrates an important principle--buried bedrock features may strongly influence Quaternary geology and geomorphology.

Northern Poland

The Vistula delta and Gdansk Bay region is a classic area for research on Eemian deposits and environments in northern Poland. Much of the modern Vistula delta and Zalew Wislany were submerged in a shallow sea or lakes during the Eemian--see Fig. 14-5. Thick marine, lacustrine, and fluvial deposits accumulated, and fossils suggest that climatic conditions were subtropical during the Eemian. During glacial advances, Gdansk Bay and the Vistula delta were often submerged by proglacial lakes.

Uplands adjacent to the delta/bay display various evidences for glaciotectonism--see Fig. 14-6. The eastern flank of the Pomeranian upland has numerous bedrock rafts, small ice-shoved hills, and dislocations of Quaternary strata. Much of the ice-shoved material was presumably derived from Gdansk Bay. The great depth of Gdansk Bay is a result of combined strong glacial erosion and glaciotectonism by major ice streams or lobes during repeated glaciations.

High bluffs along the Baltic coast northwest of Gdansk Bay. These hills are underlain by thick glaciolacustrine strata, which indicate that proglacial lakes once existed within the Gdansk Bay lowland and adjacent Baltic basin. Unconsolidated Miocene sand and silt are also present at the base of the cliffs.
Orlowo cliff, on the western side of Gdansk Bay, near Sopot, Poland. This cliff reveals strongly deformed Quaternary and Tertiary strata shoved out of the Gdansk depression.
Closeup view at Orlowo cliff showing massive till (upper right) thrust over sand and gravel that stand in vertical position (left center) beneath the thrust. Photos © by J.S. Aber.

Elblag Upland is a complex glaciotectonic feature that consists almost entirely of deformed Pleistocene sediments. The upland stands nearly 200 m above surrounding lowlands--see Fig. 14-7. The upland covers approximately 390 km², which makes it the largest single ice-shoved landform in Poland or anywhere else in the southern Baltic region. Within the upland, many deformed strata are anomalously thick and situated high above their normal levels. For example, Eemian marine and lacustrine strata are locally >100 m thick within the hill and occur at elevations up to 80 m above present sea level. Equivalent strata are only 10-20 m thick with their tops located 10-30 m below sea level, where undisturbed beneath the adjacent delta plain and estuary.

View westward from Frombork, the home of Copernicus. Elblag Upland is the large hill visible through low clouds on the horizon. The water body is Zalew Wislany, the coastal lagoon. The upland rises to nearly 200 m above sea level.
Large block of Elblag Clay (dark gray) shoved into vertical position along with glacial sand/gravel (tan). This exposure reaches about 75 m elevation; the Elblag Clay was presumably thrust up from near or below sea level by ice pushing. The clay mine is located at Kadyny on the northern margin of Elblag Upland.
Closeup view of Elblag Clay in the mine at Kadyny. The clay is strongly fractured and brecciated. Photos © by J.S. Aber.
Landscape in the central portion of Elblag Upland, near Majewo. Elongated hill on the horizon is an ice-shoved ridge that was later overridden and slightly smoothed. This ridge is part of the eastern arcuate morphologic belt of Elblag Upland.

Two morphologic patterns are well defined in the upland: (1) eastern arcuate belt, concave toward the northeast, and (2) western arcuate belt, concave to the west. These two sets converge near the center of the upland, in the vicinity of several small lakes, including Lake Stare. The greatest amount of deformation is documented in the zone of convergence, where strata stand in vertical position, and in which reworked Tertiary strata are found at elevations up to 130 m. The morphologic trends of Elblag Upland suggest two directions of local ice movement: (1) eastern section deformed by ice advance from the northeast, and (2) western portion pushed from the west. Structural evidence confirms dominant ice pushing from the northeast, and drumlins indicate final ice overriding from the NNW.

Elblag Upland represents a very large cupola hill that was formed by local ice movements from the northeast, west, and NNW (Aber and Ruszczynska-Szenajch 1997). All these ice advances took place during the late Vistulian glaciation. It is possible that Elblag Upland was created in an interlobate position, as local ice-lobes surged into a proglacial lake dammed in the Gdansk Bay basin--one ice lobe was situated to the east in the till-plain lowland, and another to the west in Vistula delta/lagoon depression.

Kite aerial photographs
of Polish lowlands.

Glaciation of Estonia

Estonia is located in north-central Europe, near the eastern end of the Baltic Sea. It represents a transition zone in the continental pattern of glaciation. To the north and west, Finland and Sweden were subjected to strong glacial erosion that stripped away soft sedimentary strata to expose the Fennoscandian Shield. To the south and east, thick glacial sediments accumulated in Latvia, Lithuania, Russia, Byelorussia, and Poland. This transition is reflected in the glacial sediments of Estonia. The northern half of the country has generally less than 5 m of glacial cover, while glacial sediments more than 100 m thick are found in the southeast (Raukas and Kajak 1999).

Map of Estonia and surrounding countries.
Taken from Estonia in the Baltics.

The northern half of the country is underlain by relatively well-consolidated limestone and dolostone of Ordovician and Silurian ages, and a narrow zone of Cambrian clay and sandstone outcrops on the northern coast along the Gulf of Finland. Southern Estonian bedrock consists of poorly consolidated Devonian sandstone and siltstone. The composition of till closely reflects the nature of underlying bedrock (Raukas and Kajak 1999). Gray, calcareous tills are common in the north, whereas red, sandy tills are found in the south. Various crystalline erratics were derived from sources in Finland, Sweden, and the Åland Islands (between Finland and Sweden). These indicator erratics are important for till stratigraphy and for reconstructing movement directions of individual glaciations.

Crystalline erratic boulders on the beach on the island of Vormsi, northwestern Estonia. Such boulders are useful to establish sources and directions of ice movement. Photo © J.S. Aber.

Digital elevation model for Estonia and surrounding areas. The islands and western mainland of the country are generally less than 30 m above sea level. Uplands (>100 m high) are found in the north-central and southern portions of Estonia, and Lake Peipsi occupies a large depression along the eastern edge of the country. Elevation data obtained from GLOBE. Raw DEM data resampled into UTM grid. Click on the small image to see a larger (55 kb) version. Image processing by J.S. Aber ©.

Most of Estonia is less than 100 m above sea level. Higher uplands are found in the north-central (Pandivere), south (Sakala), and southeast (Otepää and Haanja) portions of the country--see Figure 14-8. The Pandivere and Sakala uplands are composed primarily of bedrock. Pandivere was an area dominated by glacial erosion, and its sediment cover is often less than 5 m. Sakala has an average 20 m cover of glacial sediment. In contrast, the Otepää and Haanja uplands are composed of thick (>100 m) Quaternary sediments representing several episodes of glaciation. These sediments were strongly deformed by ice pushing in interlobate positions and may be considered as large glaciotectonic massifs (Rattas and Kalm 1999).

Left: view over Haanja Upland terrain taken from an observation tower at Suur Munamägi, the highest point in Estonia (318 m). Right: view from the top of the ski jump at the Olympic training center in the Otepää Upland. Photos © J.S. Aber.

Major ice lobes flowed through lowlands across western and easternmost Estonia, and ice flow diverted around the uplands to form local ice lobes. This led to complicated patterns of ice flow directions--see Figure 14-9. The northern coastal cliff, formed in Ordovician limestone underlain by soft Cambrian clay, was subjected to widespread glaciotectonic deformation--see Figure 14-10. Conspicuous drumlin fields are found in lowlands of central Estonia. These drumlin fields record both southeasterly and southwesterly directions of ice movement. Most of the drumlins consist of older Quaternary sediments that were deformed and molded into streamlined hills during the last glaciation (Rattas and Kalm 1999).

Saadjärv drumlin field, east-central Estonia--see Figure 14-11. Lake Saadjärv (left) occupies an elongated trough, and a long, smooth drumlin extends into the distance on right. Another lake, Soitsjärv, can be seen at extreme upper right. Kite aerial photograph © J.S. & S.W. Aber.

At least five distinct till beds have been identified along with associated stratified drift, although intervening nonglacial strata are scarce--see Table 14-1. Considerable information is available for the last glaciation--Võrtsjärve, as its deposits are widely preserved in the modern landscape of Estonia--see Table 14-2. Five phases during the general retreat of the last ice sheet have been identified along with lesser glacial limits. These phases represent either stillstands or readvances of the ice margin.

Table 14-1. Pleistocene stratigraphy of Estonia and correlation with
Russia and western Europe. Based on Raukas and Kajak (1999).
Formation Genesis Russian W. European
Järve: Võrtsjärve
Järve: Savala
Järve: Valgjärve
Järve: Kelnase
Glacial till
Periglacial vegetation
Glacial till
Periglacial vegetation
Valdaian Weichselian
Prangli Forest vegetation
Marine sediment
Mikulinan Eemian
Ugandi: upper
Ugandi: middle
Ugandi: lower
Glacial till
Periglacial vegetation
Glacial till
Middle Russian Saalian
Karuküla Forest vegetation Likhvinan Holsteinian
Sangaste Glacial till Oka Elsterian

Table 14-2. Phases of the Võrtsjärve (late Weichselian) glaciation of Estonia. Based on Raukas and Kajak (1999).
Phase Extent Direction Age*
Palivere Northwestern Estonia SE 11,200
Pandivere Northern Estonia S-SW 12,000
Sakala Central Estonia SE 12,250
Otepää Southern Estonia SE 12,600
Haanja Nearly whole Estonia SE 13,000

* Approx. age in uncorrected radiocarbon years.

The ice margin was distinctly lobate during the Võrtsjärve glaciation--ice lobes followed topographic depressions, such as Lake Peipsi, Pärnu Bay, and Väinameri (see figs. 14-8 & 9). The latter two phases of glaciation--Pandivere and Palivere--were marked by considerable meltwater discharge, which is demonstrated by numerous eskers, kame-moraine complexes, and erosional channels. In the case of the Palivere phase, eskers are preserved on land and on the shallow seafloor of northwestern Estonia--see Figure 14-12.

Views along the esker at Rumpo, southern Vormsi. Left: the road follows the crest of the esker, which bends to the east in the distance. This esker extends several km across the seafloor to the southeast. Right: looking inland toward the northwest. The road follows the crest of the esker across the island interior. Villages and agricultural fields are located on the higher, better drained esker ridge. Kite aerial photographs © S.W. & J.S. Aber.

The eskers of Vormsi and surroundings demonstrate a regular pattern in their distribution, which represents the preserved portions of a subglacial drainage network that was essentially braided in character. The esker network is located along the central pathway of the Väinameri ice lobe, and the overall direction of drainage was toward the Palivere glacial limit. Similar esker systems have been identified on the Baltic Sea floor between Estonia and Sweden--see Fig. 14-13.

Landsat image of Vormsi and the Väinameri region, northwestern Estonia. Compare with Figure 14-12 for positions of eskers and the Palivere glacial limit. Blue colors of the Väinameri reflect variations in water depth (1 to 10 m). Image acquisition date 7/86; image processing by J.S. Aber ©.

Along and south of the Palivere ice limit, an extensive proglacial lake was developed, which represents an early phase of the Baltic Ice Lake (Raukas 1993). The existence of a proglacial water body is documented further by the water-laid nature of the upper portion of the Palivere diamicton on the western Estonian islands (Kadastik and Kalm 1998). The Palivere phase has been interpreted as a significant readvance of the ice sheet following complete deglaciation of Estonia after the Pandivere stade (Karukäpp and Raukas 1997). The Palivere readvance may have taken place as a local ice-lobe surge into a proglacial lake and during which a substantial volume of subglacial meltwater was released.

As a consequence of glaciation, the crust of the eastern Baltic region was depressed substantially. During late glacial and early Holocene times, large areas were submerged beneath the Baltic Ice Lake and early phases of the Baltic Sea--see Table 14-3. Marine and coastal deposits of the Litorina Sea and Limnea Sea are widespread on the western Estonian mainland and islands. Since deglaciation, western and northern Estonia has experience significant uplift, whereas southeastern Estonia has subsided. At present, western and northern Estonia is rising at rates that exceed 2 mm per year in places, while southeastern Estonia is sinking at < 1 mm per year. A hingeline of no change crosses through Võrtsjärv and Lake Peipsi. Recent crustal movement has markedly affected river drainage and lakes. For example, the southern end of Lake Peipsi is sinking at rates up to 0.8 mm per year (Hang and Miidel 1999). Medieval churches and villages on lake islands are now submerged.

Beach gravel of the Limnea Sea, about 4000 years old. This old beach ridge is now several meters above sea level on the Rumpo Peninsula, island of Vormsi, northwestern Estonia. Photo © J.S. Aber.

Table 14-3. Main stages of lake and sea development in the eastern Baltic region. Based on Raukas (1997).
Lake/Sea Phase Age *
Baltic Ice Lake Alleröd, early Younger Dryas 10,500
Yoldia Sea late Younger Dryas, early Pre-Boreal 10,000
Ancylus Lake late Pre-Boreal, Boreal 9000
Litorina Sea Atlantic, early Sub-Boreal 7000
Limnea Sea Sub-Boreal, Sub-Atlantic 4000

* Date of maximum transgression in uncorrected radiocarbon years.

Kite aerial photographs of Estonia--Estonian KAP.

Dynamics of European Ice Sheets

The northern European Ice Sheet consisted of several distinct sectors--see Fig. 14-14. These individual ice sheets united to form a single ice mass stretching from the British Isles to northwestern Asia during Pleistocene glaciations. However, the areal distribution and chronology of glaciation are subject to considerable debate and uncertainty in the Arctic continental shelf region and northern Russia. The Scandinavian sector is best understood. More than 150 years of intensive ground observations, combined with dating of Quaternary deposits and satellite remote sensing, have led to regional synthesis for dynamics of the Scandinavian Ice Sheet (Punkari 1996).

Last glaciation of Europe (lecture 13).

During the last glaciation, the Scandinavian Ice Sheet contained several major and many minor, fast-moving ice streams, which extended as fan-shaped lobes at the ice margin--see Fig. 14-15. These ice streams/lobes were separated by interlobate zones in which ice movement was relatively slow. The locations of these dynamic features were controlled primarily by bedrock topography and secondarily by positions of ice domes and ice-marginal calving bays within lakes or seas. Ice-stream zones are marked by streamlined landforms that consist mainly of till or eroded bedrock. Interlobate zones are marked by accumulations of stratified melt-water deposits.

The dynamics of individual ice streams/lobes varied as the ice sheet waxed and waned, so that some streams were more active and expanded at times, and at other times different ones became dominant. In this way, time-transgressive and overlapping patterns of ice flow took place in many areas. Two patterns of ice flow record the last major glaciation.

  1. Older ice flow that emanated from large ice domes in northernmost Fennoscandia, the Barents Sea shelf, and possibly from the Kara Sea shelf.

  2. Younger ice flow derived from several smaller ice domes within the Scandinavian mountains. This phase was more strongly influenced by local topographic features.

The most important ice streams were ones that fed into major topographic depressions that contained proglacial lakes or seas--Baltic, Skagerrak, White, etc. These ice streams flowed vigorously, calving into the water bodies. Fast ice flow would have raised the basal temperature, which in turn contributed to subglacial melting and more rapid ice movement. Meanwhile, interlobate zones had sluggish flow or were stagnant. This explains the general tendency for interlobate zones to become areas of net sediment deposition.

Large ice-shoved hills are a characteristic part of the southern Baltic coastal landscape in northern Poland, northern Germany and southern Denmark. These hills are mainly products of Vistulian glaciation; in many cases deformation resulted from relatively late readvances. The ice-shoved hills of the southern Baltic are mostly associated with embayments or estuaries, in which ice lobes were active during deglaciation. Certain hills suffered multiple or changing directions of ice movement: Høje Møn (from ENE and S), Rügen (from NE and SE), and Elblag (from NE, W and NNW). Many of these hills may have formed in interlobate settings (Jensen 1993), although some dispute this interpretation.

Scale model of Møns Klint and the eastern part of the island of Møn, southeastern Denmark. View is toward west; maximum elevation is about 140 m. Notice the arcuate, ridged landscape formed by inland continuation of chalk masses that are exposed in the cliff. The northern (right) portion was deformed by ice advance from the northeast; southern (left) part was created by ice pushing from the south. These ice advances may have been separate events (Pedersen 2000), or glaciotectonic deformation may have occurred in an interlobate setting (Jensen 1993). Model displayed at the Geological Museum, Copenhagen, Denmark.
Space-shuttle photograph of northeastern Germany. Near-vertical view of the German island, Rügen (right-center) and mainland (lower portion); part of the Danish island of Møn is visible in upper left corner. Rügen and Møn were subjected to strong glaciotectonic deformation by ice advances from multiple directions. NASA Johnson Space Center, Imagery Services, STS045-152-156, 3/92.

During late Vistulian deglaciation, major readvances took place within the western Baltic region--the Young Baltic advances. The advances are traditionally ascribed to ice streams that originated in the central Baltic region to the east and terminated in the Kattegat Sea to the northwest--see Fig. 14-16. These advances may have been major surges that effected the entire southern Baltic ice stream, which in turn triggered surges by local ice lobes and tongues in the embayments of the southern, western, and eastern Baltic region. Many of the large glaciotectonic hills may have formed during surges by Young Baltic ice lobes (Aber and Ruszczynska-Szenajch 1997).

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ES 331/767 © J.S. Aber (2015).