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Here we present the first record of Marine Isotope Stage (MIS) 7 from Sardinia, based on a U-Th-dated speleothem from Crovassa Azzurra cave, which also grew during MIS 5. Carbonate precipitation was continuous during MIS 7, while two multi-millennial hiatuses interrupted growth during MIS 5. These hiatuses occurred during times of unstable climate, but local karst-specific conditions are considered to have played an important role as well. delta C-13 values mostly reflect soil bioproductivity and vegetation density. During less humid periods these values reflect bedrock delta C-13 values, because of a semi-closed system and/or sulphuric acid-driven bedrock dissolution. delta O-18 changes were governed by the interplay of rainfall amount and moisture source. Disentangling these two effects was possible by comparing delta C-13 and delta O-18 values, whereby both isotopes co-vary during periods when delta O-18 was dominated by the amount effect. Changes in the relative proportion of Atlantic and Mediterranean moisture sources was the main control on delta O-18 at times when delta O-18 was decoupled from delta C-13.

delta O-18 variations during MIS 5 are synchronous with Greenland stadials (GS) and interstadials (GI) GS 26, GI 25, GI-GS 22, GI-GS 21. With the exception of GS 22, these climate oscillations did not affect soil bioproductivity, and delta O-18 mirrors the relative proportion of Atlantic and Mediterranean moisture sources. GS 22 was a prominent arid period in Sardinia, in accordance with other regional palaeoclimate archives. High soil bioproductivity is indicated by delta C-13 values for MIS 7e and MIS 7c-a; the latter interval was characterized by a 30 kyr-long time span of warm and humid conditions in Sardinia. Soil bioproductivity decreased markedly during MIS 7d and the climate became drier. The latter period, also constrained by delta O-18 data, lasted significantly shorter in Sardinia than in central Europe.

As indicated by changes in delta C-13 and delta O-18 relationships, variations in moisture source are also recorded for MIS 7, with Mediterranean-dominated rainfall during MIS 7e and 7c followed by a shift toward Atlantic-dominated rainfall. (C) 2019 Elsevier Ltd. All rights reserved.