Age and origin of Cretaceous planktonic foraminifers from limestone of the Franciscan Complex near Laytonville, California

Detailed planktonic foraminiferal biostratigraphy from eight measured sections of Cretaceous limestone near Laytonville, California, indicates a composite sequence that extends in age from late Albian to early Turonian. The sequence contains seven biozones and two subzones. Unequivocal biostratigraphic facing directions show four sections are right side up and four are reversed, and confirm the stratigraphic polarity employed in the paleomagnetic studies of Alvarez et al. (1980) and Tarduno et al. (1986). We propose that this complex of biogenic and lithogenic patterns records transit via oceanic plate motion from a depositional site in the southern part of the paleoequatorial zone of high productivity to the central part of the equatorial zone dominated by biogenic calcite deposition. -from Authors