Long-chain methyl and ethyl alkenones (C-37-C-40) containing two to fo
ur double bonds have been detected in sediments from Qinghai Lake, Chi
na. This is the first report of the alkenones in lake sediments, depos
ited under a variety of salinity conditions, where the lake has not en
countered any marine incursions. The presence of the alkenones suggest
s the presence of Prymnesiophyceae in the lake which may have reached
the lake via eolian transportation or seabirds. Sediment samples from
the more saline areas of the lake contained higher concentrations of t
he more highly unsaturated compounds. Widespread use of these compound
s as paleotemperature indicators in marine sediments introduces the po
ssibility of extrapolating this approach to lacustrine environments if
appropriate calibrations can be undertaken.