A 37-meter record of paleoclimatological events from stable isotope data on continental molluscs in Valle di Castiglione, near Rome, Italy

New stable isotope analyses on molluscan shells from a long core drilled in the crater lake of Valle di Castiglione, near Rome, extended the investiga ted portion of the core to 37 m. The succession of delta(18)O parts per tho usand values in the core interval 37-2.3 m ranges from -2.8 to +6.9 parts p er thousand with only six samples below 0 parts per thousand((PDB)). These results point to arid climatic phases coupled with the high measured delta( 18)O values of the biogenic carbonate. In contrast, depleted O-18 samples c orrespond to wet climatic periods, in agreement with a strong evaporative c ontrol on the lake water isotopic composition. The C-13 content of the shel ls shows sharp changes controlled by the dissolved inorganic carbon isotope budget. Isotopic data suggest that the whole body of water behaved as a cl osed system, thus resembling lacustrine systems located in arid and semiari d regions where hydrological control dominates the geochemical parameters. (C) 1999 University of Washington.