Everything about petrified wood. Part 4.

Teredo-bored peanut wood from Australia, Tempskya tree fern, wood from Sweet Home, Oregon.
More videos about petrified wood (play list):
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Hi! Today we will continue our journey to the world of petrified wood with a bunch of new specimens to examine. Exhibit number one is an easily recognizable type of petrified wood often called teredo-bored wood. Large oval structures represent cross sections of burrows. The creatures that made the burrows are wood-eating salt-water clams called teredo worms.
These are actually bivalve mollusks that have elongated, soft bodies resembling worms. In the process of devouring underwater logs they create tunnels inside of the wood. The tunnels eventually become filled a with fine-grained sediment. In the case of this rock, it was a mix of radiolarian shells made of silica. The light color of the sediment, shape and size of oval structures bring about visual association with peanuts. Hence the name, peanut wood, applied to the petrified wood found in Western Australia. The peanut wood comes from Windalia Raiolarite formation of Lower Cretaceous period, estimated 122 to 112 million years old. This type of petrified wood is a jewelry-grade lapidary material, and it is often made into cabochons with original patterns. Kennedy Range is a well-known mining location and a probable origin for this specimen.

The peanut wood could be attributed to different trees. Our best guess is conifer, perhaps from genus Podocarpus. With smooth, creamy-white edges, this rock looks and feels like a piece of turron, a nougat confection filled with roasted almonds. Shall we call it candy rock?

Anyway, let’s move on to another fossil – Tempskya fern from Northern America. It has been established that Tempskya ferns grew in the forests of Early Cretaceous period. Although radiometric dating suggest that the specimens from Cedar Mountain formation, for example, are 97 million years old, which extends the timeline to Cenomanian age, an early part of Late Cretaceous. Even unpolished, the slab produced interesting fluorescence images with a variety of patterns. The cut is quite thin and light can be seen shining through what used to be plant vessels, currently filled with semitransparent silica minerals.

Here is another Tempskya specimen. Different color, which depends on the mineral composition of surrounding sediments. Based on the coloration, this piece is probably coming from Green Horn Mountain, Oregon, while previous, darker, piece looks like those found near Blanding, Utah. The false trunks of these tree ferns consist of several hundreds of intertwined stems and petioles. The diameter of the trunks (up to half a meter) suggests that the plants might reach heights of 6 meters. Although, considering how the morphology resembles the one of the palm trees, I think, the Tempskya ferns could be much taller. The size of petioles is tiny, implying that the fronds sticking out the false trunks were kind of small. There are several species described for the Tempskya family, but they may represent different developmental stages or various level of the same trunk. In Paleobotany, it’s a rather common situation due to the fragmented nature of the fossil record.

This next specimen represents a locality known as Sweet Home Petrified forest and was found in a driftwood deposit on a private ranch. Here we can clearly see growth rings. Sweet Home Petrified Forest in Linn County is part of scattered Ter-tiary deposits discovered at the eastern side of Willamente Valley in the state of Oregon. Around Oligocene period till to late Miocene, let’s say roughly 30 to 10 million years ago, the place was much closer to the ocean coast at that time and likely had warmer climate. Regular fallouts of volcanic ash contributed to the creation of the petrified wood in this area. Over 50 species of trees have been identified among fossils found in the area, more specifically Marker ranch, were some limited private digs happen and may still be possible by appointment. The microscopic structure of our piece corresponds to hardwood but it’s difficult to be more precise. It looks like it could be willow, buckeye or even persimmon. In my opinion, it’s the variety of species that are not commonly found in other localities that makes the Sweet Home Petrified Forest a special place. We have one more piece from the same area. Even though the microscopic structure is preserved only in few spots, the growth rings are clearly visible.
By the way, we ended up spraying the unpolished Tempskya fossil with a clear acrylic sealer made to protect paintings. It was a bit of a desperate measure, but it did work to some extent.
Thanks for watching!
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