New data on the age of Lepidocyclina in California

Abstract

During the 1930's and early 1940's, controversy about the age of Lepidocyclina californica and faunas associated with it led to unreconcilable differences of opinion in the attempt to provide a standard stratigraphic framework for Cenozoic rocks of western North America. Two standards with significantly different series age assignments were provided, one based largelyon benthic foraminifers and the other on mollusks and echinoderms. Although both standards have more recently converged in regard to correlating faunas of the Pacific Coast with those in Europe, and although the age of Lepidocyclina has been more firmly established in various countries, the age of the California Lepidocyclina remains in doubt. We report here, for the first time, planktic foraminifers and calcareous nannoplankton associated with the Lepidocyclina . These floras and faunas correlate with the Helicosphaera ampliaperta Zone of Bukrv and Zone N 7 of Blow and indicate that Lepidocyclina californica is probably early Miocene. This revised age removes the basis for the significantly different series age assignments for the Pacific Coast standards.