Pliocene—pleistocene boundary in the Kleszczów Graben at Belchatów, central Poland

Abstract

AbstractThe Pliocene‐Pleistocene boundary, defined using pollen analysis, has been recorded in sections at the Belchatów outcrop, Kleszczów Graben, central Poland. The boundary is located at the top of the green clay subunit of the Tertiary Clayey‐sandy unit. A pollen flora of Reuverian C type, dominated by pine, 10–20% of ‘Reuverian elements’ and scarce thermophilous Tertiary trees, was found directly below this subunit. Cold stage floras of Praetiglian type were, in turn, recorded in the Łekińsko Formation, lying directly on the green clays. The Pliocene—Pleistocene transition at Belchatów demonstrates the characteristic features of this boundary in western Europe, that is, the disappearance of Tertiary thermophilous tree pollen taxa, followed by a cooling to open‐forest or forest‐steppe conditions. Both pollen analysis and geological data suggest continuous sedimentation at least from the Upper Pliocene to the Prae‐Tiglian, with no change of sediment sources and no marked hiatuses. The fluvial deposits of the Praetiglian Łekińsko Formation, although Pleistocene in age, mark a final period in the Tertiary evolution of the Kleszczów Graben. Later, there is a hiatus to the deposition of the first glacigenic sediments in the region possibly of Elsterian age.