Pathologies (knots) in Petrified Wood

In the Early Pleistocene, about two million years ago, these twigs and bits of trunk were driftwood in the paleo Santa Fe River. The waterlogged twigs sank to the bottom in a basin in the river channel. They became buried in a highly organic mud during seasonal flooding.

This anaerobic, low-energy burial preserved fine details such as bark and even insect borings. The wood is thoroughly mineralized with apatite (not "silicified" as labelled) -- it 'clanks' when two pieces are tapped together. 

This wood is dated biochronologically by the vertebrate fossils also found in the mud, notably Holmesina floridana, a giant armadillo. Fossils of the beavers Castor and Castoroides, muskrats, grebes, cormorants, ducks, and large fish suggest that this was a backwater pool in the river.