Answer:
The layer of soil that is most likely newly formed is top soil.
The top layers of soil are constantly getting blown around and moved by many forces such as wind, rain, or even humans. If you go outside and look at the top layer of soil, that soil has probably only been there for a year, maybe more, maybe less.
Them you have the next layer of soil which is 'sub soil'. Pretty much the only way this soil can get moved is from forces of the Earth slowly pusing it around, or something digging a hole and relocating it.
Lastly, you have 'parent rock' and 'bedrock'. These aren't really soil at this point, more or less just stone and other rock. Again however, pretty much the only way this soils can get moved and become "newly formed" is by seismic activity. But unlike the sub soil, it's hard to dig a hole down to parent rock/bedrock layer, so humans and other hole digging forces don't affect this layer too much.
Hope this helps :)