What is my floor made from?

[Fellview]

Not sure what my floor is made from exactly. I took down a stud wall and under the frame there was a gap through the solid floor. There was some synthetic material, presumably damp proofing, and under that earth.
I also need to repair the edges which have cracked and possibly level it to prepare for laminate flooring. I have linked to pics as the forum isn't letting me upload them here:

https://ibb.co/kFnycd
https://ibb.co/cLA6Vy

Any ideas what it is and what I should use to fill gaps in it, or put over it to level it?
And do I need any damp proofing before putting it on the bare earth?

Thanks

 

[blup]

Whatever you use to "fill the gap" the new damp proof membrane will need to overlap with the adjoining membrane to avoid the damp bridging up and over into the adjoining floor - assuming that it is already appropriately protected.

I once replaced a broken tile on a floor where the screed was protected underneath by cling film - and no damp had got through. Not suggesting that though.

Cheers,

Blup