Engrave leaves sign 58ft need an advice yamashita treassure hunter

[Ririn]

 

[HuntinDog]

Don't think they are engraved, but pressed into soft clay or stone and hardened.
When you say 58ft what do you mean?
Are these excavated in the ground 58ft deep? or under the water?

 

[GoDeep]

That's what's left of a leaf that got incased in the dirt/mud, well on it's way to becoming a fossil.