This 9 September 2019 video says about itself:
Some of the world’s most exquisite fossil beds were formed millions of years ago during time periods when the Earth’s oceans were largely without oxygen. That association has led paleontologists to believe that the world’s best-preserved fossil collections come from choked oceans. But research led by The University of Texas at Austin has found that while low oxygen environments set the stage, it takes a breath of air to catalyze the fossilization process. “The traditional thinking about these exceptionally preserved fossil sites is wrong,” said lead author Drew Muscente. “It is not the absence of oxygen that allows them to be preserved and fossilized. It is the presence of oxygen under the right circumstances”: here.