Permian wood with uncommon details
deutsche Version

As a well-known fact, silicified wood often shows details which do not really represent the wood structure but are due to secondary phenomena like fungus activity or degradation. Often one cannot tell which process had caused a particular feature. small stem cross-section
The nearly circular area mainly consisting of a gray ring surrounded by coniferous-type wood (Fig.1) could be mistaken for a centre with pith but is no such. Closer inspection reveals that it is also coniferous-type wood but in a degraded state with the originally radial files of cells largely dissolved. This ring-shaped part of the polished face is not thoroughly silicified, judging from the lack of gloss and from the ability of soaking up water. What seems to be a definite boundary between degraded and well-preserved wood is a rather fuzzy transition zone in some places, indicating continuity of the wood before partial degradation had caused the contrast.

Fig.1: Small stem cross-section with degraded (gray) and well preserved coniferous-type wood. Width 50mm.

Fig.2: Degraded and well preserved wood, detail of Fig.1. Width 2.8mm.

degraded and normal coniferous-type wood

Most of the wood had been broken off along shrinkage cracks formed after silicification, except for the segment below right.
Fig.1 might suggest the simple idea that a concentric area of this stem had been prone to decay but reality is not as simple as that: Farther out on the right, beyond the well preserved black wood, there is another area of gray degraded wood, without any symmetry.
More unexpected details are found inside the gray concentric ring. Its inner boundary appears extremely rugged, with irregular-shaped cavities preferably pointing into radial direction (upwards in Fig.3). fossil wood centre boundary

fossil wood centre boundary

Fig.3: Rugged boundary between stem centre and decayed coniferous-type wood above, with pockets of well-preserved wood in between.
Width 4.3mm.

Fig.4: Detail of Fig.3.
Wood cells 37...60µm in files.
Width 1.4mm.

Fig.5 (below): Same as Fig.3. Additional pocket, not similar to wood or pith.
Width 2.8mm.

fossil wood centre boundaryUsually most of the central pith of coniferous-type stems had decayed before silicification. Persisting pith, if there is any, may be found most likely near the boundary between centre and wood, as seen in Fossil Wood News 27. Surprisingly, the clearly seen cells set apart from the degraded and shrunken wood in Figs.3-5 are not the expected pith but miraculously preserved pockets of wood, with non-deformed cells in straight files. Degraded and shrunken cells and files are faintly seen in some places on the left in Fig.5.
Conspicuous in Fig.5 is an enigmatic pocket clearly separated from both the preserved and the degraded wood. There is no indication in which way it could have formed. Apparently this type of formation tends to make the cavities seen in Figs.1,3,4,6.
fossil wood centre boundary
Fig.6 (left):
Peculiar inclusions inside stem centre, rugged boundary, and degraded wood above.
Width 8mm.

A faint texture of the slightly squeezed degraded wood is also seen in Fig.6. Most peculiar are the distinct gray inclusions among the odd stuff filling the centre. There are several of them (see also Fig.1), with degraded cellular structure, cell sizes about 40µm. Wood with inclusions of this kind seems to be rare. A sample with similar aspect is known from Kilianstädten [1].
Sample: found in the early 90s on the golf course
at Wilmsdorf, Doehlen Basin near Dresden, stored in the own collection under W/35.1.

H.-J. Weiss     2019

[1] R. Noll, V. Wilde: Petrified Wood from Central Germany.
     in: U. Dernbach, W.D. Tidwell: Secrets of Petrified Plants, D'ORO 2002, p.95.
quartz crystal with wood inside
Fossil Wood News  33
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