Ricostruzione climatica degli ultimi 17.000 anni da una stalagmite della Grotta Savi (Trieste, Italia)

Grotta Savi, which opens on the flanks of Monte Stena in Rosandra Valley (Carso Triestino, Italy), consists in a network of sub-horizontal galleries developed from 300 to 350 meters a.s.l., and a total extension of >4 km. SV1 stalagmite, which comes from the inner part of the cave, is the first European speleothem that spans continuously the last 17 ka. Eighteen MC-ICPMS U/Th method datings were obtained from the 27 cm tall stalagmite, and 345 stable isotope analyses were carried out along its growth axis (mean resolution: 50±43 yrs). The stalagmite began to growth at 16.8±0.51 ka, and the axial growth rate was very low (below 10 µm/yr) until the end of the Younger Dryas From ~10.67 to ~7.59 ka a faster axial growth rate was recorded (30 to 44 µm/yr). The δ18O record reflects the amount of water that fed the stalagmite, which depends on mean annual rainfall amount and by the evapotranspiration at the surface. The δ18O record is positively correlated with the same record from Soreq Cave in Israel (BAR-MATTHEWS ET AL., 1997), and inversely with the 18O record of GISP2 ice core (GROOTES ET AL., 1993). For the more recent part of SV1, we observed a positive correlation between δ18O-calcite and the reconstructed mean annual temperature for the last 500 years in the Alps (LUTERBACHER ET AL. 2004). The strong temperature increase between 1800 AD and today is replicated by the positive δ18O trend in SV1.