下北半島東部の新第三系∿第四系の層序と珪藻化石

概要

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The Neogene to Quaternary formations distributed in the eastern Shimokita Peninsula are divided into the Early Miocene Sarugamori and Tomari Formations, the early Middle to early Late Miocene Gamanosawa Formation, the Late Pliocene Sunagomata Formation, the Middle Pleistocene Hamada Formation and the post-middle Pleistocene Tanabu Formation in ascending order. The Gamanosawa Formation is subdivided into the Basal, the Lower, the Middle, the Upper and the Uppermost Members based on the lithostratigraphy. The Lower Member belongs to the Denticulopsis lauta Zone to the D. hyalina Zone, the Middle Member belongs to the upper D. hyalina Zone to the D. praedimorpha Zone, the Upper Member belongs to the D. praedimorpha Zone, the Uppermost Member belongs to the D. praedimorpha Zone to the Thalassiosira yabei Zone. Species composition of the fossil diatoms changed in the middle Gamanosawa Formation. This floral change is inferred to correspond to the cooling of the global climatic change.
国立科学博物館の論文