A narrow column of sediments taken by drilling into the sea‐bed with a piston‐corer. Such cores can provide a more or less complete record of climatic changes through the Quaternary. The superimposed layers of detritus include sediments and the fossil skeletons of sea creatures. In some cases these remains alone can provide indicators of climate and water salinity on the basis of their preferred habitats. They also store information about water chemistry that can be obtained using, for example, oxygen isotope analysis.