HIGH-RESOLUTION palaeoclimate records based on oxygen isotope data have provided important insights into climate variability and rates of natural climate change on about a thousand-year timescale1-3. Little is known4, however, about the variation of climate and of palaeoceanographic conditions throughout the Quaternary on timescales of less than 1,000 years (at frequencies far greater than those of the Milankovitch orbital cycles). Here we show that such high time resolution is possible from molecular stratigraphic studies based on 'biomarker' organic molecules (alkenones). We have sampled alkenone stratigraphic records at 70- to 200-yr intervals across glacial terminations I, II and IV in sediment cores from OOP site 658, off northwest Africa5. Sea surface temperatures (SSTs) derived from the alkenone (Uk37) index6-8vary rapidly beyond the range of analytical noise by up to 2.5°C in 300 yr, showing hitherto unknown cycles with about 600-yr periodicities. Some of the changes parallel similar events in the oxygen isotope stratigraphy. SST oscillations may be linked, in part, to abrupt breakdowns in Atlantic deep-water ventilation resulting from meltwater events of Quaternary glacial terminations3,9,10. © 1992 Nature Publishing Group.