Mollusks, Fossil--Arctic Ocean

Biostratigraphically and chronostratigraphically important diatoms from the Milky River Formation, Alaska Peninsula, southwestern Alaska, imply an age range of 5.4-5.5 Ma for the oldest North Pacific Cenozoic occurrence of the marine bivalve mollusk Astarte, which migrated from the Arctic Ocean into the North Pacific when Bering Strait first flooded. The data presented here are a refinement of the age range of 4.8-5.5 Ma reported earlier and imply that Bering Strait first opened very near the end of the Miocene at 5.32 Ma.