Tyrrhenian Holocene palaeoclimate trends from spelean serpulids

In tropical regions, changes in sea level and sea surface temperature (SST) can be obtained from coral reefs. In temperate seas, such as the Mediterranean, where there are neither fossil nor actively growing coral reefs, palaeoclimatic, trends and associated sea level rise can be reconstructed through radiocarbon ages and the geochemical properties of serpulid calcite tubes from colonies that dwell in submerged caves. In the present work, we reconstructed Holocene palaeoclimate trends for the Tyrrhenian Sea, through the oxygen isotopic composition of marine Polychaete serpulids that colonised continental speleothems. when the sea invaded the caves which open along the Italian coast. The long term delta O-18 trend extracted from multiple serpulid skeletons of similar to0.7 per mil increase over the last 8 kyr can be interpreted in terms of temperature change, but could also be due to long-term changes in the salinity balance of the Mediterranean. If the delta O-18 trends recorded by serpulid calcite reflected changes in Mediterranean SST starting at 8200 cal yr BP, it would coincide with the cooling trend recorded in the tropics and in Greenland ice cores. Spelean serpulids radiocarbon ages allowed us to reconstruct a Tyrrhenian sea level curve comparable to that recorded along the French Mediterranean coast. Spelean serpulid calcite, therefore, can be used as a useful tool to reconstruct paleoclimate and sea-level changes in temperate coastal karst regions. (C) 2001 Elsevier Science Ltd. All rights reserved.