Equifinality and preservation potential of complex eskers

Eskers are useful for reconstructing meltwater drainage systems of glaciers and ice sheets. However, our process understanding of eskers suffers from a disconnect between sporadic detailed morpho‐sedimentary investigations of abundant large‐scale ancient esker systems, and a small number of modern analogues where esker formation has been observed. This paper presents the results of detailed field and high‐resolution remote sensing studies into two esker systems that have recently emerged at Hørbyebreen, Svalbard, and one at Breiðamerkurjökull, Iceland. Despite the different glaciological settings (polythermal valley glacier vs. active temperate piedmont lobe), in all cases a distinctive planform morphology has developed, where ridges are orientated in two dominant directions corresponding to the direction of ice flow and the shape of the ice margin. These two orientations in combination form a cross‐cutting and locally rectilinear pattern. One set of ridges at Hørbyebreen is a hybrid of eskers and geometric ridges formed during a surge and/or jökulhlaup event. The other sets of ridges are eskers formed time‐transgressively at a retreating ice margin. The similar morphology of esker complexes formed in different ways on both glacier forelands implies equifinality, meaning that care should be taken when interpreting Quaternary esker patterns. The eskers at Hørbyebreen contain substantial ice‐cores with a high ice:sediment ratio, suggesting that they would be unlikely to survive after ice melt. The Breiðamerkurjökull eskers emerged from terrain characterized by buried ice that has melted out. Our observations lead us to conclude that eskers may reflect a wide range of processes at dynamic ice margins, including significant paraglacial adjustments. This work, as well as previous studies, confirms that constraints on esker morphology include: topographic setting (e.g. confined valley or broad plain); sediment and meltwater availability (including surges and jökulhlaups); position of formation (supraglacial, englacial or subglacial); and ice‐marginal dynamics such as channel abandonment, the formation of outwash heads or the burial and/or exhumation of dead ice

Statistical analysis of radiocarbon dates as a tool for reconstruction of the environmental changes

Statistical analysis of large sets of 14C dates may be a source of information on global or regional environmental changes. Since the nineteen seventies, an analysis of the frequency distribution on a time scale of 14C-dated samples has been carried out for several selected geographic regions. This paper presents basics of the applied method and examples of cumulative probability density functions constructed for 14C dates of peat from territory of Poland. It is emphasised that preferential sampling plays an important role in such a type of analysis. The problem of absolute age determination has been discussed, too

The first geological record of a palaeotsunami on the southern coast of the Baltic Sea, Poland

Tsunami deposits were unknown along the southern coast of the Baltic Sea for a long time. The results of present research provided evidence of high-energy event layers. They occur on the bottom of two hemispherical hollows that are cut into glaciolimnic silt and glaciofluvial sand and gravel from the Late Weichselian Age. The event deposits are represented by poorly sorted marine sand with admixtures of pebbles and allochthonous detritus of biogenic origin: marine, brackish and occasionally freshwater shells and shell debris of molluscs and snails, plant macrofossils from the marine nearshore zone, shreds and lumps of peaty material, gyttja and organogenic silt, lumps of charcoal, wood pieces and tree branches and trunks. All these features are commonly considered indicative of tsunamis. The age of the biogenic detritus found in the tsunami layer ranges from 10 390 to 6 630 cal. yr BP, whereas the oldest gyttja covering the event layers is 6 600 cal. yr BP old. This means that the tsunami occurred between 6 630 and 6 600 cal. yr BP. Various causes of tsunami event have been taken into consideration, including the impact of meteorites within the coastal plain and the littoral zone of the southern Baltic Sea

Stages of the formation of the Łeba barrier-lagoon system on the basis of the geological cross-section near Rąbka (Southern Baltic Coast, Poland)

The ar ti cle pres ents the re sults of a de tailed study of the geo log i cal struc ture of the £eba Bar rier in the R¹bka crosssec tion (South ern Bal tic, Po land). The bar rier sep a rates Lake £ebsko from the Bal tic. Five sed i men tary com plexes were dis tin guished there (M2–M6). The spa tial vari abil ity of the grain-size dis tri bu tion was ex am ined and suc ces sion stages of the mol lusc fauna oc cur ring in the in di vid ual sed i men tary com plexes were dis tin guished. Ra dio car bon dating was used to es tab lish the age of the most im por tant events dur ing the pro cess of for ma tion of the bar rier, which took place in the course of sev eral rel a tive sea-level changes. The first sed i men tary com plex (M2) at R¹bka is connected with the sec ond ingression (i2) of the Bal tic Sea (ca. 6,700–6,000 14C years BP), sea-level sta bi li za tion (6,000–5,500 14C years BP), and at last sea-level low er ing (5,500–5,000 14C years BP) in the re gion of the Gardno-£eba Coastal Plain. The sed i men tary com plex M3 de vel oped in a la goonal en vi ron ment when the bar rier was sit u ated north of its pres ent po si tion (5,000–3,000 14C BP). The next low er ing of the sea-level made the la goon shal lower and caused the emer gence of small but al ready subaerial stretches of bar rier land with a fresh wa ter fauna in the north (4,880±40 14C BP). With the next ingression stage (i3), which took place be tween 4,500 and 3,000 BP, the bar rier shifted to its pres ent-day po si tion and the la goon changed into a fresh wa ter lake. From 3,000 to 1,700 14C BP fos sil soil and peats de vel oped on the bar rier sur face as a re sult of an other sea-level low er ing. The last ingression stages (i4 and i5), youn - ger than 1,700 BP, built up the bar rier, prac ti cally in its to day’s lo ca tion (sed i men tary com plexes M4 and M5). The youn gest sed i men tary com plex (M-6) is rep re sented by pres ent-day beach sands

Geology, stratigraphy and palaeoenvironmental evolution of the Stephanorhinus kirchbergensis

The sedimentary succession exposed in the Gorzów Wielkopolski area includes Eemian Interglacial (MIS 5e) or Early Weichselian (MIS 5d–e) deposits. The sedimentary sequence has been the object of intense interdisciplinary study, which has resulted in the identification of at least two palaeolake horizons. Both yielded fossil remains of large mammals, alongside pollen and plant macrofossils. All these proxies have been used to reconstruct the environmental conditions prevailing at the time of deposition, as well as to define the geological context and the biochronological position of the fauna. Optically stimulated luminescence dating of the glaciofluvial layers of the GS3 succession to 123.6 ± 10.1 (below the lower palaeolake) and 72.0 ± 5.2 ka (above the upper palaeolake) indicate that the site formed during the Middle–Late Pleistocene (MIS 6 – MIS 5). Radiocarbon-dating of the lacustrine organic matter revealed a tight cluster of Middle Pleniglacial Period (MIS 3) ages in the range of ~41–32 ka cal bp (Hengelo – Denekamp Interstadials). Holocene organic layers have also been found, with C ages within a range of 4330–4280 cal bp (Neolithic). Pollen and plant macrofossil records, together with sedimentological and geochemical data, confirm the dating to the Eemian Interglacial.This research was supported by grant 0201/2048/18 ‘Life and death of extinctrhino (Stephanorhinus sp.) from Western Poland: a multiproxy palaeoenvironmental approach’ financed by the National Science Centre, Poland. LiDAR DTM data presented in this study were used under academic licences DIO.DFT.DSI.7211.1619.2015_PL_N and DIO.DFT.7211.9874. 2015_PL_N awarded to the Faculty of Earth Sciences and the Environmental Management University of Wrocław, in accordance with the Polish legal regulations of the administration of the Head Office of Land Surveying and Cartography