Magnitude of Middle Miocene warming in North Pacific high latitudes: stable isotope evidence from Kaneharaia (Bivalvia, Dosiniinae)

This manuscript is a version of an article published in Bulletin of the Geological Survey of Japan v. 59, no. 7-8, (2008) p. 339-353 http://www.gsj.jp/Pub/Bull_new/vol_59/59_07/59_07_06.pdf ; The Middle Miocene Climatic Optimum (MMCO) at ~ 16 Ma was the warmest interval during the Neogene. The peak of the MMCO in the North Pacific is marked by the appearance of the bivalve genus Kaneharaia (Bivalvia, Dosiniinae) in the high-latitude regions of Kamchatka and Alaska (55 –65°N). Specimens of Kaneharaia sp. were collected from two early middle Miocene high-latitude localities in the North Pacific – the Sea urchin Horizon of northwestern Kamchatka and the Narrow Cape Formation of Alaska. Middle Miocene Kaneharaia specimens were incrementally sampled for oxygen and carbon stable isotope records of seasonality. Results were compared with stable isotope profiles constructed for two Recent species of Dosinia from subtropical waters. ; Department of Geosciences Charles E. Schmidt College of Science