Geological Strata and Fossils in the Area
Tokyo Hotate (Mizuhopecten tokyoensis) Fossils
The Tokyo hotate is an extinct bivalve mollusk with a shape and size similar to that of the common scallop. Many fossilized specimens dating to over 44,000 years ago have been discovered mixed in with the fossils of mammals such as Palaeoloxodon naumanni (the extinct Naumann’s elephant) in and around the Naruto Strait. Fossilized Tokyo hotate are sometimes also found in hauls from trawler fishing boats after being dredged up from the seabed by the fierce currents of the strait.
Izumi Group Stone
A zebra-striped pattern is sometimes visible in exposed rock on the surface of the rugged earth in Naruto. This is the Izumi Group, a narrow stratum lying along the northern side of the Median Tectonic Line (Japan’s longest fault line, responsible for many earthquakes). Dating to the Late Cretaceous period around 70 million years ago, the Izumi Group is often visible alongside roads and at the seashore. The white-colored element is made up of sandstone, while the blackish sunken part is formed by mudstone. Very occasionally, fossils such as ammonites and bivalves may be found in these stripes. As this patterned sandstone is easily mined and processed to produce sheets of stone, it is commonly used for tombstones.
