and to appreciate this section in particular, this picture helps with the visual of what it was like. jayarcherdavid.com/ ... ness
The birth of the Bisti and De-Na-Zin was at the western shores of the North America Inland Sea which was thick with strange and swampy conifer forests. The trees grew to enormous size and piled across each other as they fell crisscrossed to be entombed in layers of compacting deep mud, forming the ideal conditions for preservation by petrifaction.