Alkenones in sediments of Middle Valley, Leg 139 : application as thermal sensors

The shallow sections of most holes drilled during Ocean Drilling Program Leg 139 contain alkenones derived from prymnesiophyte\ud algae. The alkenones indicate a paleotemperature of the photic zone in the upper ocean during primary carbon fixation\ud of 7°-15°C, with an average of 10.7°C. Based on laboratory hydrous pyrolyses these alkenones are altered to unknown products\ud around 200°C and are thus useful as thermal probes. The disappearance of the alkenones occurs at various depths below seafloor\ud in accordance with observed heat flows