Both sedimentary layers are baked at their contact with the volcanic rock and fragments of both sedimentary layers are incorporated into the volcanic layer.
(Both sedimentary layers; are baked; at their contact with the volcanic rock and fragments of both sedimentary layers) (Both sedimentary layers; are incorporated; into the volcanic layer)
Both sedimentary layers Both sedimentary layers
are baked are incorporated
at their contact with the volcanic rock and fragments of both sedimentary layers
into the volcanic layer