Notes on the study of fossil diatoms

Abstract

This short paper treats the subject of fossil diatoms from the geological standpoint. If we would read the history of subsurface. it is our part to learn to decipher the records in the sediments correctly. Much of this has been done, but much also remains to be done.Micropaleontology is very largely concerned with the study and classification of foraminifera, and other microscopic fossils of value in this connection are diatoms, ostracods, radiolaria, silicoflagellata, etc.Diatoms as micro-fossil are commonly liable to neglect in Geology. But they also afford testimony as to the environment in which they lived. Every species of diatoms also have a given home or environment known as a habitat, which may be marshy land, rivers and lakes, or seas and oceans.Owing to the very great number of known species and the difficulty of obtaining sufficiently reliable data on their stratigraphic distribution, the specific determination of fossil diatoms and their stratigraphic use is a particularly difficult task which has been carried out successfully only by a limited number of specialists.Many deposits such as mudstons, fine-grained shales or tuffs have fossil diatoms, or certain combinations, of their species, peculiar to themself, these can be used in correlating the strata of a given age from place to place or even land to land. wide distribution of Pelagic diatoms make them valuable index-fossils for long range correlation such as the diatomaceous bed in the Tertiary along the coast of Japan Sea. This paper has given some examples of local correlation by means of a distribution between a marine and a non-marine diatom flora occuring in lithologically similar diatomaceous rocks encountered in well cores. Diatomaceous rocks occur in the natural gas fields of Japan and diatoms make use sufficiently in these areas for stratigraphic correlations.In the fall of 1940 a. large number of test wells where put down in many areas of Japan, for the purpose of determining the possibility of developing the natural gas supply instead of oil fuel. Some samples of these wells were collected and send to me for examination. A great many of these samples contained either foraminifera, diatoms, or other micro-fossils such as silicoflagellata, radiolvia, sponge specules, pollens, etc. Like all other fossils, some species are found ranging through several deposits, whereas others are more narrowly limited. Deposits can sometimes be recognized and distinguished by a characteristic species, or more often by a particular assemblage of species, different from the species in other associated strata.The geological reports of fossil diatoms are commonly divided into two parts. The first part deals with the distribution of diatoms in the rocks, with a discussion of their ecologic and geologic significance; the second Part gives a systematic description of the diatoms. Now, it is worthy of our notice that electron-microscope is widely used on the frustules of diatoms. Such systematic descriptions on the ground of electron-microscope make in future rapid progress for the study of both living and fossil diatoms.In conclusion, I have a word to say in regard to the future. Biologist, micropaIeontologist and geologist should work in harmony to attain the accurate and complete knowledge of many events in the past.