Published online by Cambridge University Press: 20 January 2017
Previously undescribed plant and animal fossils from the Whidbey Formation represent two environments. An upper sand unit contains predominantly terrestrial molluscs (4 taxa), insects, and a vole (cf. Phenacomys), whereas a lower clay unit contains ostracodes (9 taxa), freshwater molluscs (6 taxa), insects (9 taxa), freshwater plant seeds (6 taxa), and fish (cf. Gasterosteus : stickleback). These taxa are compatible with interglacial climatic conditions on a coastal plain environment. The inferred freshwater and terrestrial environments of the Whidbey Formation imply local tectonic subsidence of the regional since the last interglaciation.