Late Pleistocene and Holocene environmental evolution of the Wkra River Valley near Bielawy Gołuskie (central Poland) recorded in palaeo-oxbow lake deposits

Abstract

Late Pleis to cene and Ho lo cene en vi ron men tal evo lu tion of the Wkra River Val ley near Bielawy Go³uskie (cen tral Po land) re corded in palaeo-ox bow lake de pos its Monika This study aimed to re con struct en vi ron men tal changes in the Wkra River Val ley near Bielawy Go³uskie (cen tral Po land) based on geo chem i cal, palynological and subfossil Cladocera anal y sis of de pos its fill ing a palaeo-ox bow lake. Two sed iment bore holes col lected from the palaeochannel bend (BG-1) and neck (BG-2) in clude full se quences of or ganic de pos its ly ing on clastic de pos its. The lower part of the BG-1 bore hole con tains gyttja that ac cu mu lated dur ing the Youn ger Dryas and the Preboreal, which is cov ered by reed peat of Preboreal and Bo real age. On top of this is al der peat that ac cu mu lated during the At lan tic. The ages of the gyttja and peat were con firmed by both ra dio car bon dat ing and palynological anal y sis. The peats are char ac ter ized by a sig nif i cant con tent of or ganic mat ter, which is rel a tively sta ble over time. This in di cates a low inten sity of me chan i cal de nu da tion in the catch ment, which is sup ported by low con cen tra tions of alu mi num and po tas sium. Cal cium val ues greatly ex ceed these el e ments, sug gest ing that the lake was mainly fed by ground wa ter. Vari a tion in trophic con di tions over time is in di cated by a ver ti cal vari abil ity in the con tent of ni tro gen, as well as by the Cladocera pop u la tion. The strong de com po si tion of peat in the top layer of the mire, and in creased con cen tra tions of phos pho rus and heavy met als, testify to in creas ing hu man ac tiv ity dur ing the most re cent time pe ri ods.

Changes in habitat conditions in a Late Glacial fluviogenic lake in response to climatic fluctuations (Warta River valley, central Poland)

“…This is cor rob o rated also by el e vated con cen tra tions of Fe, Cr and Ni. The lack of cor re la tion be tween the Fe/Mn and Cu/Zn ra tios in the de pos its, how ever, pre cludes an in ter pre ta tion of their changes in the con text of re dox con di tions, as pre vi ously per formed for other sec tions rep re sent ing small river val leys, and of fer ing an archive of the Late Weichselian in cen tral Po land (Niska et al, 2017;Okupny and Paw³owski, 2021;P³óciennik et al, 2021).…”

“…In cen tral Po land, fen peatlands be gan to ap pear mostly in the BÝlling or in AllerÝd, tes ti fy ing to the stabili sa tion of val ley bot toms and the main te nance of a rel a tively con stant base-level po si tion, as man i fested in the ac tiv ity of the me an der ing chan nel sys tem. Sev eral peatlands and palaeolakes that func tioned in ac tive river val leys have been al ready stud ied in the re gion: the Ner (Forysiak et al, 2010;Forysiak, 2012), OEwiêtojanka (Balwierz and GoŸdzik, 1997), Widawka (Paw³owski, 2012), Wkra (Niska et al, 2017), Grabia (Paw³owski et al, 2014), Luci¹¿a (P³óciennik et al, 2021;Antczak-Orlewska et al, 2023) and Warta (Forysiak, 2012). How ever, biogenic sed i ments de pos ited in an area of ac tive flu vial pro cesses are of ten ex posed to the in flu ence of river or flood wa ters, which may sig nif i cantly dis turb the orig i nal sed imen tary pat tern, and con trib ute to the ac cu mu la tion of allochthonous ma te rial (¯urek, 1993;Rydelek, 2005;Paw³owski et al, 2015;Forysiak et al, 2021).…”