Alaskan Upper Miocene Marine Glacial Deposits and the Turborotalia pachyderma Datum Plane

Abstract
Ln southeastern Alaska the first marine evidence of widespread glaciation occurs in Miocene sections near the base of the Yakataga Formation. An associated temperature decrease of about 10°C is indicated by the influx of an upper Miocene cold-water planktontic foraminifer, Turborotalia pachyderma, an event that occurred about 13 million years ago.