Abstract

The ratio of planktonic forammiferans to radiolarians has proven to be an effective and easily determined parameter for the establishment of deep-sea faunal stratigraphy in the northeastern Pacific off Oregon and Washington. The Pleistocene-Holocenc boundary, dated at 12,500 years B.P., is marked by a change from a dominance of planktonic foramimferans below to a dominance of radiolarians above. Three less-well-defined intervals of increased radiolarian abundance occurred from 16,000 to 18,000, 25,000 to 28,000, and greater than 31,000 or 30,000 years B.P. These suggest slight warming periods during the late Pleistocene.

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