#Petrify wood plus
#Petrify wood series

Wood (or other plant parts) must first be covered with such agents as ash from erupting volcanos, by volcanic mud flows, sediments in lakes and swamps or material washed in by violent floods - by any means, which would exclude oxygen and thus prevent decay. In spite of many attempts, man has not been able to duplicate this process in the laboratory. I'd ask a dendrologist what might cause this kind of delamination without removing the bark.The process of petrification of wood is still not well understood by scientists. I've also seen trees with a scar along the trunk where a strip of bark was damaged, with one dead branch and the rest of the tree still alive and growing. I once saw a large oak tree that had been killed by lightning-the tree still had all of the leaves attached (dried out and dangling), and the trunk had several vertical splits with chips of wood sticking out! The lightning had traveled down the center of the tree and killed it instantly with a steam explosion. Lightning can also have odd effects on a tree, but that would leave other marks. I know that a hard impact can cause wood to delaminate, but I'd expect that to strip the bark off first. I wonder if there was a point of damage elsewhere on the tree that allowed a fungal infection to colonize the xylem? Usually, loose bark will separate at the cambium, so there must have been something unusual going on here to create a layer of weakness. There are a couple of tiny cracks on the edge, especially at the bottom, which are probably dessication features. Looking at your photo, I notice there is very little sign of damage to the tree.

The question of why it de-bonded within the xylem is certainly intriguing. If I'm not mistaken, some petrified wood with quartz after halite (pseudomorphs) has been found at the Sweet Home Petrified Forest, suggesting the presence of salt water (will have to look for that reference).

This allows the log to remain simply underwater for quite some time, during which the bark may have swollen, leading to its debonding (common occurrence in submerged woods, I believe), as seen in the specimen. What do you mean exactly by 'having been buried in ash'? Hot ash, Pompeii-like? If yes, could you provide a bit more detail as to how fossilisation took place? So far, I imagined the wood would have spent some time underwater, say in a lake or coastal area, before onset of fossilisation (not sure how this would yield this good a preservation though.) Then, at some point in time, volcanic ash rains out onto the body of water, changing its chemistry (by releasing ionic species from the volcanic glass), thus allowing petrification to begin. Water-born mineral infiltration after interment would have been a very slow affair, into wood which was under considerable pressure. This extraordinary preservation may be due in part to the tree having been buried in ash, which dessicated the living layer (phloem) and inhibited bacterial action at the same time. In my opinion, your analysis is readily supported by the visible features: spot on. (micrograph made as follows) Edited Octoby paleoflor

#Petrify wood plus

Does my interpretation make sense? Is this really wood (secondary xylem) plus the bark? I would also like to know why the last growth ring(s) of secondary xylem would stick to the bark? I can imagine the latter swelling up and becoming loose as the wood (waterlogged) was underwater for some time, but why not de-bond at the cambium then? Below the photo is an annotated micrograph of the region indicated in the overview. Though dependent on your definition of the term, this would mean part of the bark is preserved (quite rare, in my experience). I really liked the specimen because it shows a structure that I would interpret as the phloem (see this and this website).

#Petrify wood series

According to Gregory ( 1968), the petrified wood is derived from some Miocene age subunit of the Little Butte Volcanic Series (details not entirely clear to me). The broader area, well known for its petrified wood, is often referred to as 'Sweet Home', or the Sweet Home Petrified Forest. It comes from the Holleywood Ranch in Linn County, Oregon. Recently, I acquired the petrified wood specimen (probably maple, Acer sp.) below at a local mineral show.