Evidence for Complex Early Holocene Climate Variability in the Northern Mediterranean Region from Stalagmite SV1, Savi Cave (ne Italy)

Early Holocene climate variability is more complex than previously thought, and it is becoming clearer that several abrupt short-term climate reversals occurred after the Younger Dryas (YD). The 8.2 ka cold reversal is the most documented event but there is evidence for other post-YD events. These have been linked to the Pre-Boreal Oscillation (PBO), firstly recognised in the '60s in lake sediments in central Europe. Here we present the revised, high resolution stalagmite SV1 record from Savi Cave (Italy) in the southeaster region of the European Alps. The cave is located close to the shallow Adriatic Sea, in a region characterized by a strong katabatic and hydraulic wind (Bora). At the end of the Late Glacial and the Early Holocene, the Bora could have been influenced by the presence of the still-contracting Alpine glaciers. Stalagmite SV1 appears to record the history of soil development above the cave following the cold and dry climate conditions of the Last Glacial Maximum. Interestingly, the stalagmite shows that the YD was not the last major climate reversal before more stable climate conditions of the Holocene were reached. According to the new age model based on U/Th ages and laminae counting, an event centred on 10.4 ka and lasting ~800 years is represented by changes in carbon and oxygen isotopic ratios and trace elements concentrations. A dramatic reduction in both lamina thickness and P concentration suggests a return to cold/dry climate conditions, with short periods when calcite deposited and diminished soil bioactivity. Positive covariance between carbon and oxygen stable isotope ratios and their shift towards more positive values suggests reduced infiltration and enhanced degassing en route to the cave. A short-term increase in ⁸⁷Sr/⁸⁶Sr indicates a greater contribution from a more radiogenic source in the soil (probably Aeolian dust) with respect to the (less radiogenic) limestone host rock. In the stable isotope SV1 record there is no apparent shift during the 8.2 ka event. The fact that the 10.4 ka reversal was recorded suggests it was a fairly significant event in the region. This climate anomaly was superseded in severity only by the YD.