δ18O and δ13C isotope investigation of the Late Glacial and early Holocene biogenic carbonates from the Lake Lednica sediments, western Poland

Abstract

Stable isotope composition (δ¹⁸O and δ¹³C) of biogenic carbonates derived from the Lake Lednica sediments at Rybitwy, western Poland, was applied to obtain data on climatic changes during the Late Glacial and early Holocene. A wide range of carbonates occurring in the sediments was analysed for δ¹⁸O and δ¹³C records, including shells of several gastropod species, the bivalve genus Pisidium and carapaces of ostracods belonging to the subfamily Candoninae. The δ¹⁸O and δ¹³C records reveal changes commonly observed for the Late Glacial and early Holocene with the exception of the low oxygen isotope values of the Bölling andAlleröd Interstadials. The latter is interpreted as a consequence of ¹⁸O-depletion of the lake water resulting from gradual melting of the dead ice that still filled the deepest parts of the Lake Lednica valley during the period described. TheYounger Dryas Stadial begins with the isotopically lightest values in the sequence; however, due to the 18O-depleted values of theAlleröd Interstadial the Alleröd/Younger Dryas boundary is poorly marked. The Younger Dryas/Preboreal transition is documented by a significant shift in δ¹⁸O values of about 2–3‰, resulting from an increase in the mean annual temperature. The δ¹³C record reflects the productivity level in the lake, with ¹³C-enriched carbonates during the Bölling andAlleröd Interstadials, and the Preboreal and Boreal, when photosynthetic activity of phytoplankton and macrophytes was the most intensive. Differences in δ¹⁸O and δ¹³C values between mollusc shells and ostracod carapaces reflect the specific season and subhabitat of each carbonate secretion.