Accidentally built some soil on asphalt, would work on rock

I left a pile of leaves over a pile of kindling wood, forgot it was under there.  It has rained for 40 days and 40 nights this year. Woodlice, millipedes, so much life under there!  This was on the driveway which slopes a bit and doesnt have any appreciable puddles even. So, if I were trying to build soil (like on the lab) I might just do this even without adding dirt to the mound since there is so little.  It gets a toehold, and you could come back in a few years and have dirt.  (Maybe would need to be in a puddle spot or something for climates drier than mine has been these past 2 or so months).  

I didnt leave it there to try to actually build soil but the wood was wet and buggy! The leaves over it, though not even a lot (just twigs with leaves still on them, maybe a layer about 1' thick at most), I didnt even have fallen leaves piled up.  In fact the twigs probably worked better because they hold the leaves still on them.

This might not work as well with conifers, but if you have some branches fall down in storm from deciduous this might work to build soil with minimal effort and raw material.