A preliminary zonation based on Radiolaria and diatoms from well cores has been constructed for Tertiary deep-sea sediments in high southern latitudes of the Western Hemisphere. Of 75 cores raised from the Falkland platform and southern Argentine continental slope at latitude 35°S., 31 penetrate Tertiary sediments. Early Tertiary sediments contained in eight cores raised from depths between 500-1,000 fathoms consist of diatom ooze and clayey silt. Middle and late Tertiary sediments are encountered at a variety of depths ranging from less than 1,000 fathoms to greater than 1,500 fathoms and show no correlation with isobaths. These sediments are primarily red clay and commonly contain manganese nodules. However, four cores of this age on the easternmost part of the Fal land platform are either silicoflagellate ooze, coccolith ooze, or diatom ooze. The lithologic characteristics of Tertiary sediments are in striking contrast to those of Pleistocene sediments, which consist of Foraminifera-rich sand and lutite.

Diatoms representing sub-tropical and temperate-water forms predominate in early Tertiary sediments, whereas middle and upper Tertiary sediments contain mostly temperate-water species. Pleistocene sediments are characterized by sub-Antarctic diatoms which appear to indicate a cooling of this part of the world since early Tertiary time.

The occurrence of Tertiary sediments within a few tens of centimeters of the sediment-water interface on the Falkland platform is similar to that found on the Blake plateau. The Falkland platform, like the Blake plateau, underlies a fast surface current, and erosion by bottom scour may explain distribution of the Tertiary outcrops.

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