2018 年 27 巻 p. 26-46
The geographical distribution and geological occurrence of diatom ooze and diatomite–diatomaceous sediments were reviewed in and around the middle-high latitude of the North Pacific Ocean including the Bering and Japan seas. Diatoms are the most abundant microfossils found in the bottom sediments of the northern North Pacific Ocean, and the marginal Bering, Okhotsk and Japan seas. The marginal basins in the middle-high latitude of the North Pacific Ocean were formed by tectonic and volcanic activities in the late Oligocene–early Miocene. The early middle Miocene diatomite intercalated with siliceous sandstone to siltstone was deposited in shallow basins. The middle-late Miocene diatomite and diatomaceous mudstone was formed by global cooling and increased primary productivity under anoxic bottom-water conditions at bathyal depths. The late Miocene to early Pliocene diatomite and diatomaceous siltstone formed under oxic bottom-water conditions is widely distributed. During the late Pliocene-Pleistocene, turbidity sands and/or silts capped and diluted the diatomaceous sediment. The timing of these changes in sedimentary facies is simultaneous in the North Pacific region.