Barbara Woronko

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.

Climate evolution during the Pleniglacial and Late Glacial as recorded in quartz grain morphoscopy of fluvial to aeolian successions of the European Sand Belt

Abstract We present results of research into fluvial to aeolian successions at four sites in the foreland of the Last Glacial Maximum, i.e., the central part of the “European Sand Belt”. These sites include dune fields on higher-lying river terraces and alluvial fans. Sediments were subjected to detailed lithofacies analyses and sampling for morphoscopic assessment of quartz grains. Based on these results, three units were identified in the sedimentary succession: fluvial, fluvio-aeolian and aeolian. Material with traces of aeolian origin predominate in these sediments and this enabled conclusions on the activity of aeolian processes during the Pleniglacial and Late Glacial, and the source of sediment supply to be drawn. Aeolian processes played a major role in the deposition of the lower portions of the fluvial and fluvio-aeolian units. Aeolian material in the fluvial unit stems from aeolian accumulation of fluvial sediments within the valley as well as particles transported by wind from beyond the valley. The fluvio-aeolian unit is composed mainly of fluvial sediments that were subject to multiple redeposition, and long-term, intensive processing in an aeolian environment. In spite of the asynchronous onset of deposition of the fluvio-aeolian unit, it is characterised by the greatest homogeneity of structural and textural characteristics. Although the aeolian unit was laid down simultaneously, it is typified by the widest range of variation in quartz morphoscopic traits. It reflects local factors, mainly the origin of the source material, rather than climate. The duration of dune-formation processes was too short to be reflected in the morphoscopy of quartz grains.

Age and sedimentological features of fluvial series in the Toruń Basin and the Drwęca Valley (Poland)

The deposits of the Toruń Basin are dominated by a few-metre thick sand series which fill up buried valley-like depressions. In many cases they underlie the Weichselian till which builds up the ice marginal streamway (pradolina) terraces or they are exposed at the basin slopes. As the results of the geological and sedimentological studies, as well as of the dating of the deposits at the sites in the Toruń Basin indicate, the deposits include two fluvial series accumulated before the advancement of the Leszno Phase ice sheet, i.e. in Middle Weichselian and at the beginning of Late Weichselian. The oldest fluvial series connected with the Saalian Glaciation was found at the mouth section of the Drwęca Valley. The fluvial system of the Toruń Basin during Middle Weichselian and at the beginning of Late Weichselian developed in two phases of the sand-bed braided river. During the first one the river channel were dominated by large mid-riverbed sandbars, while during the second phase the water flow was smaller and, as a result, low transverse sandbars and two-dimensional dunes developed. Other active river channel also showed low-energy flows, more intensive meandering than in the case of the braided rivers, as well as sandy side-bars. Analysis of the rounding and frosting of the quartz grains indicate that the studied series of the Weichselian sandy deposits represent alluvia of a river which were fed from two diverse sources. The first one might have represented the alluvia of a warm river which transformed its load, while the other one might have mainly carried the underlying Quaternary deposits.

Depositional environment of a fan delta in a Vistulian proglacial lake (Skaliska Basin, north-eastern Poland)

ABSTRACT The study reconstructed the environment of a fan delta filling the vast end depression of the Skaliska Basin, and its overlying aeolian deposits. The formation of the large fan delta is associated with the presence of an ice-dammed lake functioning during the retreat of the Vistulian Glaciation (MIS 2). The examined material was collected from five boreholes. Sediments were analysed for their granulometric composition and subjected to analyses of frosting and rounding of quartz grains. Grain size analysis showed that the fan delta deposits are built of sand sediments of very low lateral and vertical variability. The fan delta was supplied with fluvioglacial sediments. Accumulation of sediments occurred in shallow water with a very low-gradient slope. The exposed fan delta became a site conducive to aeolian processes after the lake waters fell and the Skaliska Basin depression dried. Dune deposits overlying the fan were affected by short-distance transport so they did not acquire features typical for aeolian deposits.

Changes of natural environment in Kraków downtown - its chronology and directions. Case geoarchaeological studies of Krupnicza street site

Changes of Natural Environment in Kraków Downtown - Its Chronology and Directions. Case Geoarchaeological Studies of Krupnicza Street Site Sediments exposed in a construction excavation form a sequence: alluvial deposits > black soil > made ground. Peat-like deposits, organic muds and occasionally sand occur between the soil and the made ground. High aeolization of alluvial sediments allows relating their age to the Late Vistulian. The sediments were eroded and in the washout at first organic muds were deposited and subsequently sands. The lowest layer, radiocarbon-dated at 4510±60 uncal. years BP (Gd-12724), can be probably linked to climate moistening at the transition between the Holocene Atlantic and the Subboreal period. Pollen grains found in muds, black soil and peat-like deposits reflect the changes of local plant cover from dominated by pine woodlands (at the transition between the Atlantic and the Subboreal period) to strongly deforested with single trees, meadows, small crop fields and gardens in the Medieval period. Palynological results describing the character of vegetation might have been influenced also by direct human activity on site, e.g. by storage of wood and branches (then used as construction material or fuel), crops, fodder or waste. Microartefacts found in soil suggest metal processing in the vicinity during the Bronze Age. In the made ground, which has been accumulating since the 14th century, quartz, clay minerals and micas were identified together with fragments of bricks, concrete, ceramics, bones, slag, charcoal, organic matter, limestone fragments and metals. Horizons enriched in slag fragments are also high in metals: Fe, Mn and Pb, which reveal a twofold increase in metal processing activity.

Depositional conditions on an alluvial fan at the turn of the Weichselian to the Holocene – a case study in the Żmigród Basin, southwest Poland

Abstract Presented are the results of research into the fluvio-aeolian sedimentary succession at the site of Postolin in the Żmigród Basin, southwest Poland. Based on lithofacies analysis, textural analysis, Thermoluminescence and Infrared-Optical Stimulated Luminescence dating and GIS analysis, three lithofacies units were recognised and their stratigraphic succession identified: 1) the lower unit was deposited during the Pleni-Weichselian within a sand-bed braided river functioning under permafrost conditions within the central part of the alluvial fan; 2) the middle unit is the result of aeolian deposition and fluvial redeposition on the surface of the fan during long-term permafrost and progressive decrease of humidity of the climate at the turn of the Pleni- to the Late Weichselian; 3) the upper unit accumulated following the development of longitudinal dunes at the turn of the Late Weichselian to the Holocene; the development of dunes was interrupted twice by the form being stabilised by vegetation and soil development.

Sorting of heavy minerals in sediments deposited at a high accumulation rate, with examples from sandurs and an ice-marginal valley in NW Poland

Density differences among the various heavy-mineral species appear to be the main factor responsible for their sorting in glaciofluvial and fluvial environments. Sediments from two sandurs (stretching perpendicular to the Weichselian ice-sheet front) and a terrace of the Toruń-Eberswalde ice-marginal valley (extending parallel to the Weichselian ice-sheet front) in NW Poland support this idea clearly. The deposits investigated were formed during the Pomeranian phase of the Weichselian glaciation. Heavy-mineral and sedimentological analyses of these sediments indicate that most changes in the proportion of the various heavy-mineral species in gravelly and sandy sediments can be ascribed to changes in the flow regime, which is, in turn, related to the density of the various heavy-mineral species. In addition, the turbulence of the current and the bedform played a role in the sorting. The sedimentation rate also affected the heavy-mineral composition of the sandur and ice-marginal valley sediments. Furthermore, the proportions of some heavy minerals depend on the transport distance, which is well expressed by differences that occur over the investigated distance of 90 km of the ice-marginal valley. It appears that some heavy-mineral species are good tools for reconstructing sorting processes. Heavy minerals deposited by streams with a fast-changing discharge and a high accumulation rate (which is common for glaciofluvial streams) can, by combining data about the composition of the assemblages with data about the characteristics (size, rounding, colour, etc.), help in reconstructing palaeo-flow regimes and in estimating the turbulence, transport distance and mode of sediment transport in the streams.

Reconstruction of sediment provenance and transport processes from the surface textures of quartz grains from Late Pleistocene sandurs and an ice-marginal valley in NW Poland

Abstract During the Pomeranian phase of the Weichselian glaciation (~17-16 ka), the Toruń-Eberswalde ice-marginal valley (NW Poland and easternmost Germany) drained water from the Pomeranian ice sheet, while intensive aeolian processes took place across Europe in the foreland of the Scandinavian ice sheet (‘European Sand Belt’). The micromorphology of the quartz grains in the Toruń-Eberswalde ice-marginal valley shows no traces of these aeolian processes, or only vague signs of aeolian abrasion. This is unique among the aeolian sediments in other Pleistocene ice-marginal valleys in this part of Europe. The study of the surfaces of the quartz grains shows that the supply of grains by streams from the south was minimal, which must be ascribed to the climate deterioration during the Last Glacial Maximum, which resulted in a decrease of the discharge of these extraglacial rivers to the ice-marginal valley.

Spectral method as a tool to examine microtextures of quartz sand-sized grains

Well-rounded grains extracted from aeolian and subaqueous environments were analysed to determine a quantitative parameter describing the microtopographic surface properties of sand-sized quartz grains, expressed as a degree of smoothness or as an inverse roughness. To this end, the spectral method was used to calculate their fractal dimension values. Fractal characteristics and spectral fractal dimension (DS) were determined for a scanning electron microscope (SEM) image (560 × 560 pixels) obtained for each study grain. This parameter, (DS), describes the complexity of objects, which means that the higher its value, the more complicated the analysed grains are in terms of exterior roughness and surface microirregularities. The obtained results indicate that values of the parameter (DS) were higher for all aeolian grains compared to grains from either low- or high-energy subaqueous environments. This difference in results is attributed to the presence of microirregularities on the surface of aeolian grains, microtextures forms such as mechanically upturned. This parameter value increases as the energy of the aeolian environment increases. Values of (DS) for subaqueous environments grains correlated with the frequency of microtextures that resulted from high-energy grain-to-grain collisions (e.g., V-shaped percussion cracks), or from the chemical etching of the grain surface (e.g., solution pits, solution crevasses)-the higher the frequency of either collision or chemical-etching microtextures, the higher the value of the fractal dimension (DS). Thus, it has been demonstrated that fractal analysis can serve as a useful tool to discriminate between the analysed sedimentary environments, to assess a depositional systems kinetic energy, and to compare the intensity of chemical weathering.

ICE-SHEET DYNAMICS OF WARTA GLACIATION (SAALE) IN THE MARGINAL ZONE OF KNYSZEWICZE AREA, NORTHEASTERN POLAND

Abstract The paper presents a research on a marginal zone near Knyszewicze in the southern part of Sokółka Hills (northeastern Poland). Terminal moraine hills are arranged amphitheatrically in a lobal pattern. Dynamics of the Knyszewicze frontal ice-sheet lobe during the Saale Glaciation and successive stages of the marginal zone near the village of Knyszewicze were reconstructed based on sedimentary and geomorphological analysis, using a digital elevation model and morpholineaments. Three main phases of the Knyszewicze glacial-lobe activity were identified including accumulation of glaciofluvial deposits, advances of the ice margin and ice-lobe retreat. Moraine hills developed at a stable ice-lobe terminus, initially as short end-moraine fans with the following sequence of lithofacies Gh⇒SGh⇒Sh or Gm⇒Gh⇒Sh. Such a sequence indicates cyclic sheet-floods. During a small but dynamic advance of the ice sheet terminus, these deposits were moved forward and monoclinally folded, then furrowed with sloping faults due to horizontal pressure. Typical thrust-block push moraines developed in this way. Ice sheet advance took place when permafrost was present in the substratum and very high water pressure occurred at glacial terminus. Inside a lobal configuration of moraines, there is a rich inventory of glacial forms with a classic terminal depression in the central part. Based on this landform pattern, their shape, rhythm and glaciotectonic disturbances, the land relief may be referred to as a hill-hole pair. The structure of Horczaki Knoll, deposited on the sub-Quaternary tectonic structure, significantly contributed to a development of this marginal zone.