Mire Development and Disappearance due to River Capture as Hydrogeological and Geomorphological Consequences of LGM Ice-Marginal Valley Evolution at the Vistula-Neman Watershed

Abstract

The advances and retreats of ice sheets during Pleistocene significantly changed high- and mid-latitude landscapes and hydrological systems, albeit differently, in North America and Europe. On the southern margin of the Last Glacial Maximum (LGM) in the Baltic Sea basin, a specific type of valley has developed between glacial margins and upland or mountain slopes. We studied new geological data (boreholes, electrical resistivity imaging (ERI) from this geomorphic setting in Northeast Poland to understand: (1) how the landscape and river network evolved to eventually produce peat mires during the Holocene, and (2) the nature of groundwater recharge to fens in the upper Biebrza Valley. We present the results on a geological cross-section with hydrogeological interpretation. We also discuss regional geomorphology. In addition, we present the LGM extent derived from a spatial distribution of Vistulian (Weichselian) terminal moraines. These end moraines are also interpreted as Saalian kames. Thus, we additionally present another method of LGM extent delineation from a physicogeographical division. We link the steep slopes of the studied valley walls (kame terrace fronts) with thermokarst erosion in the periglacial zone. We then document the hydrogeological window (DISCONTINUITY in the till layer over the confined aquifer), which enables the outflow of groundwater into the peat bog. Although minerotrophic fen mire development in the study area is likely to be sustained in the near future through sufficient groundwater supply, the projected capture of the Biebrza River by the Neman River will not allow for sustaining peatland development.

Rivers Try Harder. Reversed “Differential Erosion” as Geological Control of Flood in the Large Fluvial Systems in Poland

“…Bedrock protrusion can serve in such a case as the limit of an incision. Many large river valleys in Poland are landforms inherited from the ice-marginal valleys [70], which were impacted by fluvial and glaciofluvial deposition during the last (Vistulian; from German also: Weichselian) glaciation. This deposition formed the upper terraces that reworked the fluvial setting in the river valley and enabled the later floodplain formation in Holocene [30].…”

The role of the river in the functioning of marginal fen: a case study from the Biebrza Wetlands

“… Stratigraphy and genetic type of deposits: 1—Saalian (Odra) fluvioglacial sediments; 2—Saalian (Odra) glacial sediments 3—Saalian (Warta) fluvioglacial sediments; 4—Saalian (Warta) glacial sediments; 5—Vistulian (pre-LGM) fluvioglacial sediments; 6—Vistulian (post-LGM) kame terrace; 7—Holocene peat ( Wierzbicki et al, 2020 , modified). …”

Environmental Context of the Early Mediaeval Settlements Complex Near Grodzisk (Ne Poland) in the View of Interdisciplinary Research

“…The Biebrza catchment, location in Poland, and general topographic features [6] The last stage of its evolution occurred in the Holocene. This is when the high saturation of the superficial layers of valley sediments coupled with the favorable climate allowed for the development of mires [17]. Unique hydrogeological features and suspected hydrogeological windows are responsible for supplying the Upper Basin of the Biebrza Valley with mineral rich groundwater [18,124,19].…”

“…Unique hydrogeological features and suspected hydrogeological windows are responsible for supplying the Upper Basin of the Biebrza Valley with mineral rich groundwater [18,124,19]. However, due to the architectural complexity of fluvioglacial sediments, these hydrogeological windows that supply distantly recharged groundwater to topographic depressions are seldom documented [17]. In this period controlling factors of the evolution were climate and vegetation changes [15,17].…”

“…However, due to the architectural complexity of fluvioglacial sediments, these hydrogeological windows that supply distantly recharged groundwater to topographic depressions are seldom documented [17]. In this period controlling factors of the evolution were climate and vegetation changes [15,17].…”