Evaporation cools the interiorvfor quite a while and the pyroclastic stream is just one trainload of heat and death for maybe half an hour. So the marrow aint c

Evaporation cools the interiorvfor quite a while and the pyroclastic stream is just one trainload of heat and death for maybe half an hour. So the marrow aint cooked, its fresh and all the bacteria is denatured, the environment is a ashy cement tomb, so all liquid evaporating from the dna shards is take up by the surrounding ash-cement capsule. Not an expert ,just an enthusiastic guesser.