Highlights Stable isotope compositions of a last interglacial (LIG) stalagmite, Central Europe  A sequence of climate change events during the LIG for European speleothems  Hydrogen isotope data of inclusion water reveal a major event at about 125 ± 2 ka  Temperature and winter precipitation changes around the Mediterranean at 125 ± 2 ka ABSTRACT Studies on the last interglacial (LIG) can provide information on how our environment behaved in a period of slightly higher global temperatures at about 125 ± 4 ka, even if it is not the best analogue for the Holocene. The available LIG climate proxy records are usually better preserved and can be studied at a higher resolution than those of the preceding interglacials, allowing detailed comparisons. This paper presents complex stable hydrogen, carbon and oxygen isotope records obtained for carbonate (δ 13 Baradla data indicate enhanced aridity and seasonality for a part of GS26, with the relative dominance of summer precipitation and Mediterranean moisture contribution. Following the GS26 event, the effect of long-term global cooling becomes dominant in the Baradla isotope records and leads to glacial inception at about 109 ka.

The issue of diagenetic alteration of carbonate deposits in caves (speleothems) has gained increasing importance in recent years, as this process has serious consequences for speleothembased paleoclimate studies. In this study stable hydrogen and oxygen isotope data of water trapped in fluid inclusions were collected for recently forming stalagmites and flowstones in order to determine how dripwater compositions are reflected and preserved in the inclusion water compositions. Hydrogen isotope compositions were found to reflect dripwater values, whereas the oxygen isotope data were increasingly shifted from the local dripwater compositions with the time elapsed after deposition. The δ 18 O data are correlated with X-Ray diffraction full width at half maximum values (related to crystal domain size and lattice strain),suggesting that the oxygen isotope shift is related to recrystallization of calcite. Transmission electron microscope analyses detected the presence of nanocrystalline (<50 nm) calcite, whose crystallization to coarser-grained calcite crystals (>200 nm) may have induced re-equilibration between the carbonate and the trapped inclusion water. The Ostwald ripening process provides an explanation for unexpectedly low oxygen isotope compositions in the inclusion water. The detected diagenetic alteration and its isotopic effects should be taken into consideration during sampling strategies and data evaluation as speleothems containing nanocrystalline calcite during their deposition are prone to late-stage oxygen isotope water-carbonate re-equilibration, which may shift the oxygen isotope composition of the inclusion water to more depleted values while the hydrogen isotope composition remains intact.