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Toothhound
Saitama · Japan

Chichibu Miocene exposures (Saitama, Japan)

Guided / club only📚 Compiled from public sources

The Chichibu basin west of Tokyo exposes the middle-Miocene Chichibumachi Formation, the most accessible Asian site for shark teeth — including occasional megalodon. Best engaged via the Saitama Museum of Natural History and its public field walks; private quarry access is not allowed.

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Geology
FormationsChichibumachi Formation, Akahira Formation
EpochsMiocene
Age~16-15 million years
Star speciesOtodus megalodon (rare), Carcharodon hastalis, Hemipristis serra
Technique

Join a Saitama Museum-led field workshop, or visit the museum's reference exhibit before walking the public outcrops along the Arakawa River. Surface finds only; report significant material.

Access

~2 hr by train from central Tokyo (Seibu-Chichibu line). The Saitama Museum of Natural History in Nagatoro is the visitor base.

Legality & ethics

Japan protects significant fossils as regional cultural property. Surface collecting on public land is generally tolerated; quarry access requires owner permission.

Hazards
  • Arakawa River currents after rain
  • Steep gorge sections (Nagatoro)
  • Bear sightings in upper reaches
Insider tips
  • Combine with a Nagatoro Gorge boat ride — same outcrops from the river
  • Spring (cherry blossom) and autumn are the comfortable seasons
  • Museum bilingual signage; English tours by request
References & further reading

Shark teeth findable here

Trophy = headline find · Rare = real score · Uncommon = some trips · Common = most trips.

Also findable here

The beachcomber's bonus round — what else the geology gives up.

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