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ABSTRACT

In this study, we present a composite δ18O and δ13C record obtained from four speleothems from the Grotta Grande del Vento Cave, located within the Frasassi karst system, northeastern Apennines of central Italy. The ages were determined by U-series analysis, employing thermal ionization mass spectrometry (TIMS), and the composite isotopic profile covers most of the time period from ca. 95,000 yr B.P. until ca. 10,000 yr B.P., including the last part of marine isotope stage (MIS) 5, most of the last glacial (MIS 4–2), and the earliest Holocene (MIS 1), with a hiatus lasting from ca. 65,000 to ca. 55,000 yr B.P. We compared this record with other speleothem records from the Eastern Mediterranean, with caves from western Portugal, with two marine records from the Eastern Mediterranean and the Aegean Sea, and with the North Greenland Ice Core Project (NGRIP) ice-core record. The Frasassi speleothem record provides further insight for a wider regional understanding of the paleoclimate record through the discrepancies and similarities between the northeastern Apennines of central Italy and the Western, Eastern, and northeastern Mediterranean regions.

The time interval between ca. 86,000 and 83,000 yr B.P. shows low δ18O values in the Western and Eastern Mediterranean speleothems and the marine records. This period coincides with sapropel (S3) and is associated with increased hydrological activity and warming. On the other hand, Frasassi speleothem δ18O data do not show a similar low trend, suggesting that increased hydrological activity either did not reach the Frasassi region and/or the region received rainfall from other sources and/or the proportion of winter-summer rainfall was different.

Another interval in which different conditions prevailed in the Frasassi region is during the transition from MIS 5 to glacial MIS 4, from ca. 83,000 to 65,000 yr B.P., when Frasassi speleothem δ18O values decreased, whereas all other records show a clear increase in δ18O. Comparison with the NGRIP record suggests that Northern Hemisphere temperature changes are reflected in Frasassi speleothem δ18O fluctuations during this interval.

A major pronounced isotopic event associated with warming and pluvial conditions during the last glacial evident in the entire Mediterranean region between ca. 54,500 and 52,500 yr B.P. is recorded also in the Frasassi speleothem isotopic profile. This event is followed by a transition from wet and warm climatic conditions to cold conditions. The end of the last glacial is associated with climate instability, evident mainly from the very large oscillations in the Frasassi δ13C record. The transition from the last glacial to early Holocene is characterized by a decreasing trend in δ18O and a sharp increase in δ13C values.

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