The staining is probably not the bitumen but damp. The moisture has been trapped underneath. There is probably no way to bring it back to life

It might be damp right through the block if so nothing can be done will smell bad
My suggestion spend half hour on small patch 1ft x1ft of floor with hand sander see if u like the result if u do go hire more powerful sander from hire shop will take forever with diy sander

The only thing you can do is to paint the wood. Any oil base paint will keep the worst back. Bring him back to a new state it's not possible and will cost loads of money

It is difficult to make an exact prognosis without seeing the floor. It could be as suggested damp causing the staining and this would be mould pores which would show up as black specs and surface staining. However it also could be the Bitumen which would not necessarily cover all of the parquet but would be mostly around the gaps along the blocks. This would appear to be a denser black sticky staining.
To test this you could try some solvent thinners to see if the stain starts to soften and come off. Try Acetone or cellulose thinners but please wear a mask and gloves and use in well ventilated area. If this removes the staining then the floor could be sanded. In which case a good continuous belt sander or powerful orbital sander could be used best to hire these. Plenty of elbow grease and a strong back and determination will be required.