New occurrences of Fortipecten hallae (Dall, 1921) (Mollusca, Bivalvia) in the Pliocene of the North Pacific

The large North Pacific bivalve mollusk index-fossil Fortipecten hallae (Dall, 1921) is present in a well-dated stratigraphic section of the Milky River Formation, Alaska Peninsula, southwestern Alaska. Co-occurring marine diatoms belong to the upper part of the subzone B of the Neodenticula kamtschatica diatom zone of the North Pacific diatom chronostratigraphy, with an age range of 4.8-5.1 Ma (early Pliocene). Based on coeval occurrences in northeastern Kamchatka, Russia, and synchronous changes in the two molluscan assemblages, F. hallae is a useful indicator of early Pliocene climatic warming along the high-latitude North Pacific margin.