I wouldn't be surprised if these would be remnants of forging weapons or building bricks. That would my guess about their presence.Alternatively, it's because we're filling the entire world with microplastics.
Umm howfrom contamination by our industries
from contamination by our industries
The microplastics themselves are not ancient. There are concerns they may change the soil chemistry and cause decay of organics that were once believed best preserved by remaining in situ
Apparently with how archeological sites are preserved. This particular one was started in the 1980s so it had decades of a contamination window.