The alternative interpretation of chronology of flood events in the mid-Warta River valley: Record of Early Holocene alluviation in the Koło Basin (central Poland)

The detailed research of organic deposits with remains of riparian forest dated to the Allerød – Younger Dryas transition undertaken at the Koźmin Las site enables the discussion of the evolution of river system and flood events in the Koło Basin (central Poland). Results of former studies showed the intense accumulation of silty-sandy overbank deposits during the Younger Dryas. Results of recent research in the Koźmin Las site, including results of 14C dating of organic deposits, indicate significant increase of flooding in the Early Holocene. In consequence, this interpretation indicates the existence of a meandering river pattern during Allerød and Younger Dryas, and the development of a multichannel river system in the Early Holocene in the Koło Basin, including the mid-Warta River.