. The Earth beneath the sea : History . "x " X xe »m xE xM > d Fig. 11. Tertiary and Quaternary micro fossils in surface sediments of the Pacific floor. X marks sample positions, and if not accompanied by another letter the microfossil assemblage is believed to be purely Quaternary. E, M and L indicate admixture of early, middle and late Tertiary microfossils respectively: capitals if Tertiary forms are estimated to constitute more than 20% of the microfossil assemblage, lower case if the Tertiary admixture is estimated to constitute less than 20% of the assemblage. Non-fossilifer


. The Earth beneath the sea : History . "x " X xe »m xE xM > d Fig. 11. Tertiary and Quaternary micro fossils in surface sediments of the Pacific floor. X marks sample positions, and if not accompanied by another letter the microfossil assemblage is believed to be purely Quaternary. E, M and L indicate admixture of early, middle and late Tertiary microfossils respectively: capitals if Tertiary forms are estimated to constitute more than 20% of the microfossil assemblage, lower case if the Tertiary admixture is estimated to constitute less than 20% of the assemblage. Non-fossiliferous samples and those of doubtful age are not plotted; some available data are omitted in areas of high sampling density. Some of the age assignments on this and the next figure were made by M. X. Bramlette on the basis of coccolitho- phorids. For a number of samples from the and Pacific, we are indebted to the Academy of Sciences' Institute of Oceanography, the Japanese Hydro- graphic Department and the British Museum (Natural History) {Challenger samples]. movements which keep the outcrop swept free of Quaternary deposits. Reworked microfossils occurring at many localities in the deep Pacific indicate that this type of disturbance is rather widespread (Fig. 11). 7. Pre-Quaternary Paleoceanography Sediment cores collected from the deep-sea floor occasionally sample Tertiary strata. The cores at present obtainable are usually not long enough to penetrate a continuous sequence of fossiliferous sediments from the Recent through the Pleistocene and Pliocene to the Miocene or Oligocene: most of the Tertiary


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