PRESERVATION OF THE ALKENONE PALEOTEMPERATURE PROXY IN UPLIFTED MARINE SEQUENCES: A TEST FROM THE VRICA OUTCROP, CROTONE, ITALY

The alkenone organic paleotemperature proxy has been used with great success to generate sea surface temperature (SST) records from diverse areas of the world ocean and for a wide range of timescales. To date, however, this methodology has been applied only to marine sediments; the fidelity of alkenone preservation in lithified, uplifted marine sequences exposed on land has not been explored. Such sedimentary sequences have experienced burial depths of hundreds of meters to kilometers before uplift, as well as exposure to oxic pore fluids upon ascent to the surface, either of which may cause alteration of biomarker compounds. We have extracted alkenones from the Plio-Pleistocene aged marine marls of the Vrica land section in Crotone, Italy. We compare alkenone SST estimates from the Vrica section with alkenone SST estimates derived from coeval marine sediments (burial depth ~50 m) retrieved at Ocean Drilling Program Site 964, which lies ~150 km offshore of the Vrica location. We find that SST records from the land and marine sections are well correlated, showing similar mean values, cyclicity, and amplitudes. A small (~1.0°C) offset toward higher temperatures in the Vrica record may reflect a slight bias in alkenone preservation in the land section, or could record true climatic differences between the two locations. We conclude that alkenone preservation at the Vrica section allows reliable SST reconstruction. Although results from different pelagic and hemipelagic sequences might depend on the uplift and weathering histories of individual outcrops, this study suggests the possibility of reconstructing a long, continuous temperature history of the Mediterranean Sea using other land sections exposed throughout the region.