Palaeogeographical significance of the Eemian biogenic sediments at Bór site (Warta River valley, Central Poland)

Joanna Petera-Zganiacz, Ryszard K. Borówka, Jacek Forysiak, Grażyna Miotk-Szpiganowicz, Dominik Pawłowski

Abstract


An investigated area is located in the middle reach of the WartaRiver valley. During drillings in the Bór site organic deposits such as detritous calcareous gyttja and calcareous detritous gyttja has been documented in a depth between 14,9 and 16,6 m. The organic deposits are covered by mineral, mostly sandy deposits. The accumulation took place in the small lake formed as an abandoned channel. Palynological analysis led to conclusion that biogenic accumulation began at the end of Wartanian and took place at least to the Eemian Interglacial optimum. Results of palynological, Cladocera and geochemical analysis inform about water level changes and increasing of trophy status of the reservoir. Presence of Mesozoic substratum very close to the palaeolake bottom influenced significantly chemical features of the organic deposits. As Eemian organic deposits are uncommon in the Warta River valley, the Bór site seems important for palaeogeographical reconstructions of the Warta River valley during Eemian Interglacial.           


Keywords


gyttja; palynology; Cladocera; geochemistry;Warta River valley deposits

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