Oceanic sediments

Oceanic sediments are found on the deep ocean floor (generally below 3 km depth) hundreds of kilometers seaward of the continental margins and cover more of the earth's surface (55 percent) than the continents (29 percent). Within this vast realm there is an array of distinctive sediments, Globigerina ooze, red clay, hemipelagic muds, manganese nodules that occur nowhere else on earth. These sediments are largely generated within the ocean although detritus from the continents can also be important, especially at the margins of the ocean basins. Ocean drilling reveals that the oldest deep-sea sediments are Jurassic (ca. 140 Ma) and that the type and distribution of oceanic sediments has changed with time. Ocean waters filling the ocean basins today are cold and well oxygenated but 50 million years ago were warmer and less well oxygenated. Pelagic clays are accumulating where once calcareous-rich sediments were deposited. As climate and the ocean environment have evolved, the suites of sediments that cover the modern seafloor have changed. …