Monday, February 10, 2014

Fossil branch from the Mahantango

Being that the Mahantango formation is Devonian in age, more specifically Givetian stage, it is not uncommon to find pieces of pyritized branches. Sometimes they can be a bit difficult to ID as fossil wood because they are thin and often could be confused with worm burrows. On a recent trip to Deer Lake, PA I found a piece with what I believe is unmistakably a fossil branch. On the specimen below you can see the brown-orange staining from the breakdown of the pyrite which is the first clue.

Next is this closeup which shows a branching structure that could be the remains of a rachis (central vein to which the pinnules of leaflets were attached in tree ferns).
Lastly is the patten of the preserved structure which is entirely different from the surrounding rock. It looks striated and rough where as the rock is smooth and homogenous.
I could still be wrong and this is actually a worm burrow. There are no other preserved "rachis" which should be regularly spaced along a main branch. On the other hand the fossil is very straight with no obvious undulations that might be the result of the worm moving through the sediment.

No matter what this is an interesting specimen and makes one think about the paleoenvironment that it was deposited in.

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