1987 Fiscal Year Final Research Report Summary

Diatom Biostratigraphy of the Neogene in Hokkaido

Research Project

Project/Area Number	61540572
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	Stratigraphy/Paleontology
Research Institution	Osaka University
Principal Investigator	ITARU Koizumi Asociate Professor College of General Education, Osaka University, 教養部, 助教授 (20029721)
Project Period (FY)	1986 – 1987
Keywords	Diatom Biostratigraphy / Diatom Frustule / Opal-CT / Datum Level / 前-中期中新世 / 温暖性種
Research Abstract	About 350 samples were taken from the Neogene strata in the western and eastern Hokkaido for diatom biostratigraphic study. The dissolution of diatom frustules were usually recognized in the samples from the central part of sedimentary basin, because the opaline silica of diatom frustules converted to cristobalite (Opal-CT) under pressure and heat in the sediments that have been deeply buried. Therefore, the suitable samples for the diatom biostratigarphic study came from the marginal zone of the sedimentary basin and the uplift area. Four early to early middle Miocene diatom zones such as Dentivulopsis praelauta Zone, Denticulopsis lauta Zone, Denticulopsis hustedtii Zone, and Crucidenticula nicobarica Zone were missing in those samples taken from the Neogene of Hokkaido. It is considered that the abundance of warm water diatom species is reduced in the northern area and several first and last appearances of these species are usually diachroneith in higher latitudes.

(2 results)