Over a century ago, when sedimentologists began studying deep-sea sediments, they could grab only small samples of mud from the seafloor. To study the evolution of sedimentation with time, it became imperative to add a vertical dimension and the first long-piston cores opened an entirely new field. When the seafloor-spreading and plate-tectonic hypotheses were developed, it was clear that the best test was to add the time dimension to the models. This combination of interests made the Deep Sea Drilling Project a logical step.

At first, the project aimed at verification and time-calibration of plate tectonics, but it soon became clear that oceanic sediments contain a wealth of information regarding the paleo-oceanographic evolution of the world ocean. One striking result of drilling is that, although the evolution of the oceanic crust appears rather continuous, oceanographic conditions have undergone abrupt changes that may reflect variations in the geometry of the ocean basins. Thus, the sediment record of the past 200 m.y. is both more diversified and more discontinuous than anticipated. For the first time, vertical sequences of cores allow a study of diagenesis of

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pelagic sediments from the incipient stage to the mature stage.

Oceanographic events, diagenetic effects, and lithologic boundaries related to the geodynamic evolution of the crust all affect large areas of the seafloor. Their imprints in the physical properties of the sediments can be recorded on seismic profiles over long distances between drill sites. Thus, for the first time, we can reconstruct the evolution of entire ocean basins from almost their time of creation and can separate basin-wide or even worldwide events from those that are only local in origin.

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