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The impact of postglacial palaeoenvironmental changes on the properties of sediments in the kettle hole at Jurki (NE Poland)

Karasiewicz T. M., Hulisz P., Noryśkiewicz A. M., Stachowicz-Rybka R., Michalski A., Dąbrowski M., Gamrat W. W.

Geological Quarterly

2017

Vol. 61, No. 2

319--333

This research is focused on a small kettle hole located within the Morąg moraines (Iława Lake District, NE Poland). The study objective was to determine the impact of palaeoenvironmental changes in sedimentation and properties of sediments filling the bottom of the kettle hole. Sedimentological, geochemical, and palaeobotanical studies enabled us to distinguish several development phases of the kettle hole, and cluster analysis performed on physicochemical data yielded seven local geochemical zones (JuI/I to JuI/VII). The beginning of biogenic sedimentation in the conditions of a small water body, functioning in the Late Glacial period (4.20–4.10 m), was determined on the basis of palaeobotanical research. Sediments deposited in the lake during its further evolution were rich in microelements such as Ca, Na, Mg, and K, and to a smaller extent – Fe and Mn (JuI/I–III local geochemical zones). The Late Glacial lacustrine period ended with the accumulation of very silty, pollen-free gyttja, with a stratigraphic hiatus (JuI/IV, 3.40–3.20 m). The sediments were enriched with SiO2ter, which indicates an increased rate of slope erosion, and concretions of Fe-Mn occurring below this layer (JuIII) provide evidence for lowering of the water level and even desiccation. In the Holocene, the lacustrine period ended with the accumulation of coarse detrital gyttja (3.20–2.60 m). Palaeobotanical data indicate that the next group of sediments were deposited in the Late Subboreal and Subatlantic periods (2.60–0.0 cm, JuI/V–VII; sedge peat). Their properties were varied and related to hydrologic conditions, limited denudation, and vegetation succession. There was also a significant change in the trophic conditions of the water and consequently in the sediments of the kettle hole, which changed during the lacustrine period from basic to acid, and strongly acid in the surface layer. This reaction may be related to a change in the water regime as well as to human impact in the environment, which led to the colonization of the peat bog by Sphagnum moss.

Late Saalian (Wartanian) glacial palaeogeography and formation of end moraines at the northern slope of Silesian Rampart, Southwestern Poland

Krzyszkowski D., Łabno A.

Annales Societatis Geologorum Poloniae

2002

Vol. 72, No 1

67-87

There is evidence, hitherto often denied, for the ice marginal features, including the end moraine hills along the Silesian Rampart, SW Poland. These end moraines are attributed to the regional advance of the Wartanian ice sheet into its maximum position, which is also marked by subglacial till bed. The end moraine hills are located on the northern slopes of the Silesian Rampart and they are very rare, partly due to subsequent erosion, but mainly due to conditions not favourable for a remarkable proglacial accumulation. The Wartanian end moraines of southwestern Poland possess several features that suggest that they are end moraines with dominant waterlain, stratified sediments. They are interpreted as alluvial fans, where the ice margin is represented by a 'scarp'. They have semi-conical form, often plano-convex geometry and an average distal slope of 2-25°. These fans are equivalent to sheetflow-dominated or 'humid' alluvial fans in non-glacial environments. Sedimentary sequences of the end moraines consist mainly of coarse-grained material, with boulders up to 1.8 m in diameter, with typical sediments of 'proximal fan' with a highly pulsatory water discharge. The formation of the end moraine followed the formation of a proglacial lake and strong erosion after its drainage. The end moraine was formed during oscillation of the ice margin that resulted in local glaciotectonic deformation of the end moraine fan sediments (push) and a set of parallel hills, with successive younger alluvial fans (retreat).