Periglacial Conditions Research Articles

THE INFLUENCE OF GEOLOGIC-GEOMORPHOLOGIC CONDITIONS ON THE FORMATION AND SPATIAL DISTRIBUTION OF BEDLOAD SEDIMENTS OF THE EASTERN-EUROPE'S RIVERS

The map of channel-forming bedload sediments of the Eastern Europe rivers compiled by the author shows the two main patterns. Firstly, difference in the bedload grain size is associated with the different geomorphic and orographic provinces drained be the rivers. Secondly, on the lowland rivers there is a prominent negative trend of bedload grain size from the north to the south. First tendency emphasizes strong control which geological and geomorphic structure, mainly bedrock lithology and surface gradient, have over bedload grain size. The second trend can be explained by the distribution of Pleistocene glacial and fluvio-glacial deposits over the East European Plain. Rivers with gravel or sand-gravel channels are widespread in its western and northern parts where valleys are cut into the Middle and Late Pleistocene glacial deposits rich in coarse particles up to boulders. Widespread occurrence of silty and sandy-silty bedload in the rivers of the southern regions is associated with fluvial reworking of loessy loams accumulated under periglacial conditions and clayey marine deposits left by transgressions of the Black and Caspian seas. The rivers of central and eastern parts of the East-European plain commonly have sandy bed-load sediment. Fluvio-glacial deposits of the outwash plains are the main source of sandy particles as well as older alluvial sands left from the ancient rivers of the East-European plain.

Chronology and palaeoenvironmental implications of the ice‐wedge pseudomorphs and composite‐wedge casts on the Magdalen Islands (eastern Canada)

The Magdalen Islands are a valuable terrestrial record, evidencing the complex glacial and periglacial history of the Gulf of St. Lawrence. Thirteen structures interpreted as ice‐wedge pseudomorphs or composite‐wedge casts were observed at four sites on the southern Magdalen Islands and testify to the former presence of permafrost under periglacial conditions. These features truncate Carboniferous sandstone or Last Glacial Maximum (LGM) glacial and glaciomarine diamicts, both overlain by subtidal or coastal units. Six optically stimulated luminescence (OSL) and four radiocarbon ages were obtained from both host and infilled sedimentary units. These ages provide the first absolute chronological data on these structures, shedding new light on the relationships between glacial and periglacial phases. Our chronostratigraphic data suggest that, after the deglaciation and the emersion of the archipelago, thermal contraction cracks grew during the cold period of the Younger Dryas (11–10 ka; 12.9–11.5 cal. ka BP). The Younger Dryas, which is well documented in the Maritime Provinces of Canada, occurred after a pedogenesis phase associated with the Allerød warm period evidenced by the well‐developed palaeopodzol ubiquitous on the Magdalen Islands.

Factors controlling sedimentation in the Toruń-Eberswalde ice-marginal valley during the Pomeranian phase of the Weichselian glaciation: an overview

Abstract During the Pleistocene the Scandinavian ice sheet drained huge quantities of sediment-laden meltwaters. These meltwaters supplied ice-marginal valleys that formed parallel to the front of the ice sheet. Not without significance was the supply of ice-marginal valleys from extraglacial rivers in the south. Moreover, periglacial conditions during and after sedimentation in ice-marginal valleys, the morphology of valley bedrocks, and erosion of older sediments played important roles in the depositional scenarios, and in the mineralogical composition of the sediments. The mechanisms that controlled the supply and deposition in ice-marginal valleys were analysed on the basis of a Pleistocene ice-marginal valley that was supplied by northern and southern source areas in the immediate vicinity. Investigations were conducted in one of the largest ice-marginal valleys of the Polish-German lowlands, i.e., the Toruń-Eberswalde ice-marginal valley, in sandurs (Drawa and Gwda) supplied sediments and waters from the north into this valley, and on extraglacial river terraces (pre-Noteć and pre-Warta rivers), formed simultaneously with the sandurs and ice-marginal valley (Pomeranian phase of Weichselian glaciation) supplied sediments and waters from the south into this valley. A much debated question is how similar, or different, depositional processes and sediments were that contributed to the formation of the Toruń-Eberswalde ice-marginal valley, and whether or not it is possible to differentiate mostly rapidly aggraded sandur sediments from ice-marginal valley sediments. Another question addresses the contribution of extraglacial feeding of the Toruń-Eberswalde ice-marginal valley. These matters were addressed by a wide range of analyses: sediment texture and structure, architectural elements of sediments, frequency of sedimentary successions, heavy-mineral analysis (both transparent and opaque heavy minerals), analysis of rounding and frosting of quartz grains, and palaeohydrological calculations. Additionally, a statistical analysis was used. The specific depositional conditions of distribution of sediments in ice-marginal valley allow to distinguish new environment of ice-marginal valley braided river. The spectrum of depositional conditions in the Toruń-Eberswalde ice-marginal valley and their specific palaeohydraulic parameters allow to distinguish three coexisting zones in the ice-marginal valley braided-river system: (1) deep gravel-bed braided channel zone with extensive scours, (2) deep sand-bed braided channel zone with transverse bars, and (3) marginal sand-bed and gravel-bed braided channel zone with diamicton and breccia deposition, which were characterised in detail. Some of the results have been published previously, which is why they are discussed in the present paper within the context of new data

Rimmed depression of the lake Krasnoye in the Moscow Region – ancient degraded pingo

The lake Krasnoye lies on the 3d terrace of the Moscow River in the periglacial region of the Moscow and Valdai glaciations. It has rounded conical shape 300 m in diameter and 9 m in depth, and is surrounded by a gentle rim 2-6 m in height and 100-150 m in width. Deposits of the rim (sand and sandy-loam) have lumpy, practically non layered structure which is similar to gravitational deposits of the slope foot. Authors suggest that these deposits might be formed at the foot of the large ancient pingo existed here in the periglacial conditions, from the slopes of which unconsolidated sediments crept and were washed down. The impact origin of this rimmed depression should by reject because of the complete absence of the deep rocks ejecta.

What was an interglacial river like? Sedimentological investigation of Holsteinian fluvial deposits in eastern Poland

Holsteinian fluvial deposits in the Samica River valley in eastern Poland have been studied, in an approximately 12-m-thick succession filling palaeochannels and comprising sandy channel facies succeeded by a package of gyttja, peat and silt deposited in oxbow. Channel belts including palaeochannel fills cut into outwash sands and are overlain by diamictic sands reworked by solifluction under periglacial conditions. Sedimentological and palynological investigations in combination allowed the recognition of glacial and interglacial deposits. The channel belt was formed by a typical sand-bed, meandering river with deposition controlled by abundant point bars. The sedimentary evolution of the Samica valley is interpreted in the context of the glacial-interglacial cycle. Valley-scale erosion and change of river style from braided to meandering occurred coevally with the decay of an ice sheet (deglaciation) and the main phase of meandering river sedimentation is attributed to latest Elsterian and early Holsteinian. The next part of the interglacial, from pioneer stage to established temperate conditions, is recorded in a biogenic oxbow-lake fill. The succession studied has been compared with published data on the European fluvial deposits of Middle Pleistocene interglacials. It is pointed out here that river channel patterns in western and eastern Europe differed. Based on this observation, some general hypotheses regarding the continental-scale climatic distinctness are put forward.

A large and active debris-rockslide in the Central Andes of Argentina (30.26°S): Morphometry and triggering mechanisms

A large (>0.1 km2) and complex mass movement in the Central Andes of Argentina (final portion of Cordillera de Olivares, Frontal Cordillera), was studied to identify the triggering factors and understand their relationship with geomorphic, cryogenic and climatic dynamics. This debris-rockslide is composed of clast supported blocks of Permian–Triassic volcanic breccias. In order to characterize this feature, high resolution satellite imagery interpretation was carried out, together with the study of the landslide detachment zones and landslide bodies. These debris-rockslide events could have originated as a consequence of the combination of internal slow deformation and fragmentation under periglacial conditions, followed by a sudden collapse of the rock mass. Pre- and post-slide digital elevation models (DEMs) were created from topographical data with the help of a Geographic Information System (GIS) tool. Approximately 14.89 M m3 of rock and debris travelled nearly 2 km from an elevation of 5023 m–4325 m asl. Although usually the origin of such catastrophic movements is related to seismically active areas with earthquakes whose magnitude frequently exceed Ms 6, our hypothesis is that this debris-rockslide event has a climatic origin caused by large snow accumulations during winters and subsequent fast meltdown processes during spring, which would have facilitated the sliding. The paper outlines the important role that snowmelt can play in the genesis and evolution of rock displacements and the importance of meteorological data, seismic catalogues, historical aerial photography and satellite images in geomorphological back-analysis.

Lithological discontinuities in Podzols developed from sandstone cover beds in the Stolowe Mountains (Poland)

Podzols developed within so-called cover beds were examined on a slope built of Cretaceous sandstones in SW-Poland. Their typical feature is an easily recognizable stratification of regolith, evidenced in the dichotomy of soil texture and dense subsoil. Heterogeneity of soil profiles is manifested in vertically differentiated sequence: (1) dense, skeletal and massive layer, comprising usually Bs and BC horizons, sometimes Bhs/Bh horizons with strong platy structure is overlain by (2) the uppermost, relatively young layer, consisting of loose sandy material, bearing single coarse fragments of a less weathered sandstone, hosting AE, E and partially Bh horizons. This remarkable layering of slope sediments caused a distinctive lithological discontinuity at the boundary of E and B horizons, evidenced by the differences in: (i) rock fragments' content, (ii) degree of rock clast weathering, (iii) distribution of highly resistant minerals, and (iv) fluctuation of silt and sand fractions within profiles. Lithological discontinuity influences both the lateral podzolization, and the thickness and depth of albic and spodic horizons along the slope catena. Regarding the temporal order, the lowermost layer was influenced by periglacial conditions at before the Boreal; presumably as the surface layer (high score of pollen grains). The age of surficial sandy layer (based on pollen record) could be established at Subatlantic and correlated with forest cutting and intensive surface erosion (charcoal dating: 960+/−30calBP). Neither layers that originated from the eolian processes were distinguished nor any admixture of allochthonous material was found, therefore “typical” middle and upper periglacial cover-beds are not present in this sequence. In any case, Podzols that were formed from the slope sediments in the Stolowe Mountains are polygenetic and of the Holocene age.

THE GEOGRAPHICAL BACKGROUND TO THE ARRIVAL OF MAN IN AUSTRALIA AND TASMANIA

A USTRALIA and the Americas were both colonized for the first time during ?' the last Ice Age by a physically modern man, employing advanced Palaeolithic technologies. In both cases, man entered a new continent, adapting his own culture to deal with unfamiliar country, animals and plants, and conversely subjecting the environment to the ecological pressures of his own technology to which it had never before been exposed. The colonization may be seen as part of a general geographical expansion carried out by late Palaeolithic man, the move into Australia predating that into the Americas by at least 10,000 years. Their completion left the polar ice caps, and some islands of the Pacific and elsewhere, as the only significant areas of land still to be claimed. To get to America, the first colonists derived from the Gravettoid cultures of northern Eurasia, would have had to negotiate glacial or periglacial conditions, but their journey could have been carried out overland, and many of the plants and animals in the new region would have been familiar to them. Australia, however, could only have been reached by sea, the several water barriers of Wallacea (Darlington 1957 : 462) providing the shortest crossings, and the continent beyond, isolated since the early Tertiary, contained a largely endemic and highly distinctive flora and fauna. Most of the early Australian stone industries are characterized by flat convex edge, steep concave edge and high domed scrapers , with considerable regional variation. Their closest analogues are found in the late Palaeolithic Middle Stone Age industries of sub-Saharan Africa and India from which they were probably derived. The paucity of information about the Palaeolithic succession in the Asiatic neighbours of Australia does not yet permit closer comparison.

Late-glacial to Holocene aeolian deposition in northeastern Europe – The timing of sedimentation at the Iisaku site (NE Estonia)

The Late-glacial and Holocene aeolian inland dune complex at Iisaku (NE Estonia) has been investigated using an accurate and detailed compilation of the sedimentary properties and chronological framework. The quartz grains forming the dunes are very variable, reflecting aeolian, weathering, and periglacial conditions, both prior and after deposition. Although the morphological forms and the sedimentary record point to a dune-like environment, the transport record reflects either a short transport time or/and distance, and a contribution from neighbouring sedimentary environments.Dune development in the area was strongly controlled by the formation of the Baltic Ice Lake (BIL) in front of the retreating glacier. Luminescence ages from the aeolian complex suggest continuous deposition between 13.3 ± 1.2 to 10.5 ± 0.7 ka. However, the chronology of sand deposition also suggests phases in this aeolian activity: (1) at 13.3 ± 1.2 ka and onwards, possibly correlated with the existence of an island separating the BIL and Peipsi Lake, (2) between 12.7 ± 0.8 – 12.5 ± 0.8 ka representing the Younger Dryas cold reversal, (3) between 11.5 ± 0.7 – 10.9 ± 0.8 ka indicating that aeolian deposition continued over the Younger Dryas/Holocene boundary, and (4) early Holocene sand–drift at 10.5 ± 0.7 ka.

Current transition from glacial to periglacial processes in the Dolomites (South-Eastern Alps)

A close relationship between glacial and periglacial landforms is frequently observed in alpine environments, where a transition from glacial to periglacial processes often took place after the end of the Little Ice Age (LIA). Understanding the origin of these landforms is challenging, and assessing the current spatial domain of glacial and periglacial processes may be a difficult task in high-relief areas, where thick and widespread debris cover often characterize rapidly decaying glaciers. Here we present a comprehensive study of a composite landform located in the Dolomites (South-Eastern Alps), combining geomorphological, geophysical and topographic surveys with ground surface temperature measurements. Results indicate that a debris-covered glacier persists in the upper part, rather large compared to the LIA extent, but currently inactive and rapidly losing mass. An active rock glacier exists in the lower part, surrounded by discontinuous permafrost. A frozen body about 10m thick was detected in the rock glacier and geomorphological evidence suggests that this ice mass is completely detached from the debris-covered glacier. Our findings suggest that the lower part of the composite landform is probably a remnant of the ancient glacier tongue and is currently evolving under periglacial conditions. Periglacial processes are therefore replacing glacial processes which dominated in this site during the LIA.

Late Pleistocene stratigraphy and sedimentary environments of the Severnaya Dvina‐Vychegda region in northwestern Russia

The Late Pleistocene stratigraphy from the Severnaya Dvina‐Vychegda region of northwestern Russia is revised based on investigations of new localities, revisiting earlier localities, introduction of about 110 new OSL dates and burial depth corrections of earlier published OSL dates, in addition to six new radiocarbon dates. Most of the OSL samples studied here are from fluvial and subaquaeous sediments, which we found to be well bleached. Six chronostratigraphical units and their sedimentary environment are described, with the oldest unit consisting of pre‐Eemian glacial beds. For the first time, Early Weichselian sediments are documented from the region and a fluvial environment with some vegetation and permafrost conditions is suggested to have persisted from the end of the Eemian until at least about 92 ka ago. The period in which a Middle Weichselian White Sea Lake could have existed is constrained to 67−62 ka, but as the lake level never reached the thresholds of the drainage basin, the lake probably existed only for a short interval within this time‐span. Blocking and reversal of fluvial drainage started again around 21−20 ka ago when the Fennoscandian Ice Sheet advanced into the area, reaching its maximum 17−15 ka ago. At that time, an ice‐dammed lake reached its maximum water level, which was around 135 m above present sea level. Drainage of the lake started shortly after 15 ka ago, and the lake was emptied within 700 years. Severe periglacial conditions, with permafrost and aeolian activity, prevailed in the area until about 10.7 ka.

Soils and landforms from Fildes Peninsula and Ardley Island, Maritime Antarctica

Fildes Peninsula (F.P.) and Ardley Island (A.I.) are among the first ice-free areas in Maritime Antarctica. Since the last glacial retreat in this part of Antarctica (8000 to 5000yearsBP), the landscape in these areas evolved under paraglacial to periglacial conditions, with pedogenesis marked by cryogenic processes. We carried out a detailed soil and geomorphology survey, with full morphological and analytical description for both areas; forty-eight soil profiles representing different landforms were sampled, analyzed and classified according to the U.S. Soil Taxonomy and the World Reference Base for Soil Resources (WRB).Soils are mostly turbic, moderately developed, with podzolization and strong phosphatization (chemical weathering of rock minerals and formation of amorphous Al and Fe minerals) in former ornithogenic sites while in areas with poor vegetation show typical features of cryogenic weathering. Nivation, solifluction, cryoturbation, frost weathering, ablation and surface erosion are widespread. The most represented landform system by surface in Fildes Peninsula is the periglacial one, and 15 different periglacial landforms types have been identified and mapped. These features occupy about 30% of the land surface, in which patterned ground and stone fields are the most common landforms. Other significant landforms as protalus lobes, rock glaciers or debris lobes indicate the extensive presence of permafrost. Soil variability was high, in terms of morphological, physical and chemical properties, due to varying lithic contributions and mixing of different rocks, as well as to different degrees of faunal influence.Three soil taxonomy orders were identified, whereas thirty four individual pedons were differentiated. Fildes Peninsula experiences a south–north gradient from periglacial to paraglacial conditions, and apparently younger soils and landforms are located close to the Collins Glacier. Arenosols/Entisols and Cryosols/Gelisols (frequently cryoturbic) are the most important soil classes; Leptosols/Entisols, Gleysols/Aquents and Cambisols/Inceptisols also occur, all with gelic properties, and with varying faunal influences. Both soil classification systems are adequate to distinguish the local pedogenesis processes. The WRB system is broader, since it was designed to be applied in all Polar Regions; the family classes adopted by the ST were effective in separating soils with important differences with regard to texture and gravel content, all important attributes accounting for the ecological succession and periglacial processes. An altitudinal organization of landforms and processes can be recognized from geomorphological mapping. Periglacial features are dominant above 50ma.s.l. although are present at lower altitude.

EemianWeichselian Pleniglacial fluvial deposits in S Poland (an example of the Vistula River valley in Kraków)

A fragment of the middle terrace in the VistulaRivervalley, nearby the railway station in Kraków, is formed by fluvial channel and overbank deposits of the PrądnikRiver, which bear a record of various environments affected by changing climatic conditions. The sedimentary succession includes two complexes that differ in lithofacies. The older complex comprises fining-upward deposits (channel sand and gravelly sand with medium- and large-scale trough cross-stratification) and, less frequently, sand with planar cross-stratification overlain by silt with intercalations of biogenic deposits of abandoned channels. Vegetation accompanying the deposition of biogenic layers was typical of boreal coniferous forests, dominated by Pinus sylvestris with a small admixture of Larix, Pinus cembra, Picea, Betula, and Populus . Periodically, the landscape passed into open areas overgrown by woody tundra. The complex developed as a result of activity of a meandering river under conditions of a moderately cool climate. The younger complex includes the sand lithofacies with horizontal stratification and low-angle cross-stratification, overlain by alternating sands and silts. The topmost part is represented by sands with large- and medium scale planar cross stratification. Lack of biogenic deposits and considerable amount of frosted quartz grains in alluvial sediments indicate aeolian processes of greater intensity, periglacial conditions and evolution towards a braided or transitional river. Pollen successions, absolute dating and studies of structural and textural features of the sediment suggest that the time of its deposition may be estimated at a range between the close of the Eemian Interglacial and the Weichselian Middle Pleniglacial (OIS 5e–OIS 3).

Age and Origin of Blockfields on Scottish Mountains

Numerous researchers have proposed that blockfields on mid-latitude plateaux are frost-modified relicts formed initially by chemical weathering under warm, humid pre-Quaternary (Neogene) conditions. Others contend that they formed mainly by frost action during the Quaternary. We test these competing hypotheses for blockfields on three mountains in NW Scotland: a matrix-supported diamict blockfield (sandstone), clast-supported diamict blockfield (quartzite) and an openwork blockfield (schist). Clay concentrations in the fine fraction are low (0–6.8%) and both clay:silt ratios and secondary clay minerals (illite, kaolinite and gibbsite) are consistent with prolonged chemical weathering under periglacial conditions. There is negligible depletion of labile elements in the fine fraction relative to the parent rock. Conversely, evidence for surface and near-surface granular disaggregation, an increase in clast angularity with depth, dominantly angular sand grains, in situ detached clasts and fractured clasts above rockhead favour formation by frost weathering under Pleistocene stadial conditions. There is no convincing evidence for blockfield inheritance from Neogene regolith. As the blockfields were buried under cold-based glacier ice during the last glacial maximum, they pre-date ice-sheet build-up at ∼35–30 ka. Measured rates of plateau surface lowering suggest that present blockfield regolith is probably of Late Pleistocene (<135 ka) age.

Petrography of alluvial sands as a past and present environmental indicator: Case of the Loire River (France)

Four sample sets of the Upper and Middle Loire river sands were analyzed in order to study the impact of natural and anthropogenic factors on their petrographic composition in space (on an 800 km stretch) and time. Composition was determined by modal analysis of three sand-size fractions using a polarizing optical microscope and calculated for each sample (“standard sand” = Sst). The watershed is composed mainly of endogenic (Massif Central) and sedimentary (southern Parisian Basin) rocks. B-set sands collected in channels for different water flows in 1996 show that Sst compositions vary by only 5 %. Present-day sands in the Upper Loire and Middle Loire have very high petrographic immaturity comparing to others worldwide fluvial sands, although bio-climatic conditions favor sand maturation by source-rock weathering in the watershed. This shows the strong impact of the Massif Central on sediment yield due to relief rejuvenation as a consequence of the formation of the Alps during the Quaternary. Fluvial sands stored during the Weichselian and the Holocene in the Middle Loire floodplain, although partly weathered since their deposition, show higher inputs from the endogenic rocks of the Massif Central than present-day deposits. This can be explained by Weichselian periglacial conditions and the development of crop farming since the Neolithic, which favored mechanical erosion, particularly in the Massif Central which is characterized by a cold, humid climate and steep slopes. The upstream-downstream change in the composition of presently deposited sand is low in the diked area. It shows however that basalt and some heavy mineral grains are vulnerable to abrasion during transport and indicates a marked sediment yield from ancient sediment stored in the floodplain. This is in line with the high incision of the river bed over the last 150 years partly due to dam construction and aggregate mining.

Paleo-pedological record of the Rocourt pedosequence at Veldwezelt–Hezerwater (Belgian Pleistocene loess belt): Part 2 — Soil formation

As the environment influences soil formation, Quaternary loess–paleosols provide an important, yet complex source on former climate and vegetation conditions. This study revises the paleopedological record of the Rocourt-complex, the pedostratigraphic marker for the Eemian and early Weichselian in the Belgian loess belt. Depth functions were established from an exceptionally well-preserved, in-situ sequence. Based on soil micromorphological features, total element contents, iron fractions and carbon content a reconstruction was made of the polygenetic formation of the Rocourt soil. Results indicate that only by combining multiple soil features, consistent information could be obtained. Furthermore, this study shows that cryogenic processes, transport of colloids, iron dynamics, redox-conditions, organic matter formation and biological activity were major soil forming processes. The hypothesis of six major stages of soil formation under varying climatic conditions was most supported by the data. During the warm to temperate oceanic climate of the Eemian, a strongly weathered argic horizon was formed. This horizon was later disrupted by reticulate ice segregation and stagnogley during the severe and prolonged cold conditions of the first cold stadial following the Eemian. Weak soil formation, during the relatively short continental St. Germain I interstadial, subsequently formed cambic soil properties and a humiferous horizon in a mixture of local and new sediments. These soils were disrupted by fragipan Formation, with its associated cryogenic structure, banded eluviation and redoxfront, during the succeeding stadial with periglacial conditions. During the St. Germain II, another A horizon formed in new, calcareous material during more stable climatic conditions, allowing organic matter build-up, eluviation of smectite and formation of pedogenetic iron. During the evolution from this warmer climate with forest or forested steppe to eventually periglacial open tundra, an accretionary humiferous soil concluded the last episode of soil formation before the onset of pleniglacial Weichselian conditions.

La secuencia de terrazas cuaternarias del río Alcanadre (provincia de Huesca): caracterización y consideraciones medioambientales

A very extensive sequence of Quaternary fluvial terraces composed of nine strath levels (from Qt1 to Qt9) has been recognized in the Alcanadre River valley (Ebro basin, Huesca province). New mapping, altimetric, stratigraphic, pedogenic and chronological data have been supplied. A braided fluvial sedimentary environment is deduced. The confinement of the fluvial system increases as a response to drainage incision. Pedogenic carbonate morphology reaches highest development (stage VI) with the age. Palaeomagnetic data indicate that, tentatively, the age of Qt1 is near 1000 ky and the age of Qt2 is around 780 ky. In addition, numerical ages of Qt5, Qt6 and Qt7 are 44 ± 2 ky, 19 ± 2 ky and 10 ± 1 ky respectively by using Optically Stimulated Luminescence (OSL). This Upper Pleistocene chronology matches well with the regional fluvial chronostratigraphy recorded in non-glaciated river valleys. It is correlated to cold periods MIS3, LGM and YD at global scale. In a palaeoenvironmental scenario dominated by periglacial conditions, fluvial aggradation is enhanced by high sediment supply from slopes and a seasonal behaviour of rainfalls.

El glaciar rocoso de Cerro Krund, Tierra del Fuego, Argentina

In the Sierra of Alvear, Tierra del Fuego, the Cerro Krund is located overhead the ski Cerro CastorArea. In the South slope of the Cerro Krund, to 900 m a.s.l., an active rockglacier is siting as they attest the presence of interstitial ice and of cracks in track slope that crosses it. The area is subjected to morfoclimatic periglacial conditions that have substituted to the glaciers from the initiate deglaciation 10-9 ka. BP aproximately. The periglacial dynamic and some favorable morfo-estructural conditions (fragmentation of the rock, extensive outcrop when the glacier ice has disappeared) and tectonics (regional high seismic character) they are the factors that have favored the rockglacier genesis.

Heavy and light minerals as a tool for reconstructing depositional environments: an example from the Jałówka site (northern Podlasie region, NE Poland)

Abstract Part of northern Podlasie (NE Poland), shaped during the Wartanian stadial of the Odranian glaciation (Saalian), was situated in the periglacial zone during the Vistulian (Weichselian) glaciation. Both landforms and sediments were affected by the periglacial conditions. This is recorded at the Jałówka site, at the floor of a dry valley, where mineral deposits of 4.13 m thick, overlying organic deposits from the Eemian interglacial, were examined. These mineral deposits form four units, from bottom to top: a fluvial unit (I), a loess-like unit (II), a solifluction unit (III), and an aeolian unit with ice wedges (IV) on top of unit III. The heavy and light minerals were analysed, as well as the geochemistry, in order to find out about the parent material and to reconstruct the climatic conditions during deposition. The mineral analysis indicates that the Saalian till was predominantly derived from shallow-marine deposits; erosion accompanied by sorting of the heavy minerals took place on the basis of their mass and grain size. The original material of the till seems therefore to be sedimentary rocks from the eastern Central Baltic Basin. This material became strongly weathered under the periglacial conditions, resulting in the destruction of the quartz grains, as well as in leaching, leading to complete decalcification of the deposits. Aeolian activity resulted in infilling of ice wedges and the creation of thin layers. The intensity and the duration of these processes was limited, so that the effects of the aeolian abrasion are insignificant. Neither resulted the aeolian activity in significant reshaping of the landscape.

Heavy–mineral assemblages from fluvial Pleniglacial deposits of the Piotrków Plateau and the Holy Cross Mountains – a comparative study

Abstract The heavy-mineral assemblages of Pleniglacial fluvial sediments were analysed for two river valleys, viz. the Luciąża River (at Kłudzice Nowe) and the Belnianka River (at Słopiec). These sites, on the Piotrków Plateau and in the Holy Cross Mountains respectively, are located in different morphogenetic zones of Poland that were affected to different degrees by the Middle Polish ice sheets. The study was aimed at determining the kind of processes that modified the heavy-mineral assemblages in the two fluvial sediments, at reconstructing the conditions under which these processes took place, and in how far these processes caused changes in the assemblages. The heavy-mineral associations of the parent material was taken as a starting point; this parent material were the sediments left by the Odranian glaciation (Warta stadial = Late Saalian). It was found that heavy-mineral assemblages in the Luciąża valley deposits are varied, particularly if compared with other fluvioglacial Quaternary deposits from the Polish lowlands, with a dominance of garnet. In the fluvial deposits of the Belnianka valley, zircon, staurolite and tourmaline dominate, with minor amounts of amphibole, pyroxene, biotite and garnet. This suggests that the deposits were subject to intensive and/or persistent chemical weathering and underwent several sedimentation/erosion cycles under periglacial conditions. In both valleys chemical weathering and aeolian processes were the main factors that modified the assemblages of the transparent heavy minerals; these processes were largely controlled by the climatic changes during the Pleistocene.