Mid-Caenozoic Calcareous Nannoplankton from Western North America

Abstract

CALCAREOUS nannoplankton provide sound bases for interregional correlation of Caenozoic marine strata, and are potentially equally useful for inferring oceanographic conditions at various times in the past. Recent debate^1–6 concerning correlation of the mid-Caenozoic benthonic microfaunal stages of western North America with plank-tonic foraminiferal biostratigraphic zones of low latitudes, and with the European stages has prompted this study of the calcareous nannoplankton. The fossils were studied by optical and electron microscopic techniques. This communication records the stratigraphic distribution (Table 1) of the principal species and discusses their significance for interregional correlation. A complete report will be presented elsewhere. Localities mentioned were described by Kleinpell⁷ unless otherwise noted.