 One group examined carbon-14 dates for charcoal particles that showed wildfires occurred well after the proposed impact date, and the glass-like carbon was produced by wildfires and no lonsdaleite was found.Scientists have asserted that the carbon spherules originated as fungal structures and/or insect fecal pellets, and contained modern contaminants and that the claimed nanodiamonds are actually misidentified graphene and graphene/graphane oxide aggregates.An analysis of a similar Younger Dryas boundary layer in Belgium yielded carbon crystalline structures such as nanodiamonds, but the authors concluded that they also did not show unique evidence for a bolide impact.