Tertiary sediment cores and microfossils from the Pacific Ocean floor

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Abstract
Tighty-five cores containing either Tertiary sediment or abundant reworked Tertiary micro-fossils have been selected for description from approximately 900 Pacific deep-sea cores collected by the Scripps Institution of Oceanography between 1950 and early 1961. The area covered by the 85 cores extends from about 45° n to 45° s , and from 151° e to 73° w , although most were collected within the tropics. A brief lithological and micropalaeontological description is given for each core; wherever possible, a photograph of the core and a profile of the adjacent topography are provided. The Radiolaria, planktonic Foraminifera, and calcareous nannoplankton were investigated. Stratigraphical interpretations are based on all three groups and supported by lists of species of Radiolaria and Foraminifera. The ages range from Eocene to Pliocene, with reworked Cretaceous at one locality. Tentative interpretations are put forward regarding the distribution of pelagic sediments and water masses in the Pacific during the Tertiary. Miocene and Pliocene sediments are similar at most localities to near-by Quaternary deposits, and it is concluded that near-surface currents and water masses were generally similar to those of the present day. The only apparent exceptions are a displacement of the northern boundary of the Equatorial Current System to a location about 5° north of its present position at 139°w, and possibly a 5° southward displacement of the southern boundary of the Subarctic Current at 173°w. During the Oligocene, the northern boundary of the Equatorial Current System was apparently 7° north of its present position at 137°w. At 130–50°w, the southern boundary of that current system and the northern edge of the West Wind Drift appear to have been situated near their present positions. Eocene occurrences show greater departures from the pattern of Quaternary sediment types. The northern boundary of the Equatorial Current System appears to have been situated about 9° north of its present position, at 135–65°w. The few occurrences of this age south of the Equator cannot readily be interpreted in terms of a pattern of water masses similar to that of the present day. The evidence from the cores does not indicate any substantial lowering of the calcium carbonate compensation depth during the Tertiary, with the exception that in low latitudes in the north-east Pacific it may have been depressed to 5100m during the Oligocene. No systematic relationship between topography and the localities of Tertiary sediments cropping out or shallowly buried has so far been worked out.