Black fossil wood aspect caused by fire or water ?
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wood gap The present discussions on climate changes often refer to charcoal from wildfires [1] as evidence of occasional dry seasons while land plants flourished. This has misled some less careful palaeobotanists to see  charcoal where there is only black wood.
To differentiate between fossil charcoal and fossil black wood may require careful investigation with advanced equipment [1,2] but there are fossils, like the ones shown here, where charcoal can be excluded by visual inspection and simple reasoning.
Soon after the recovery of these chert samples at Wilmsdorf in the Döhlen Basin, the mainly black coniferous-type wood fragments well preserved therein were mistaken by professional
s for fossil charcoal, as dicussed in Fossil Wood News 9 . Apparently they did not notice small details contradicting the charcoal interpretation: patches of tissue with brown cell walls instead of black ones, and large plastic deformations in some places (Figs.1, 2).
Subsequent contributions (
Fossil Wood News 9,
  35, 37, 38.) have helped to raise the awareness concerning erroneus charcoal claims.

Fig.1: Cavity resultung from fracture and slip of the nearly but not quite solid silicified wood, one column thereof leaning to the left before final solidification. Image width 2.8mm.

Fig.2: Coniferous-type wood torn into pieces while softened after lying in water; with rolled-up cell files between two touching pieces. Image width 3.5mm.
wood roll
The wood had lain in bog water for some time, where it had lost its mechanical strength, possibly under the influence of microbes, and had got a black stain. It easily disintegrated into pieces of various sizes and shapes floating in the bog water, suggesting an interpretation as crushed charcoal (Fig.2). After continuing supply of silicic acid from leached volcanic ash (?), everything turned into silica gel and finally into chalcedony.
The tiny details indicating inelastic deformations in Figs.1,2 could not have formed in brittle charcoal. They must have formed while the wood was still flexible. A subsequent
wildfire would have destroyed the delicate structures. Hence, there was no such, and this is no charcoal.
This contribution is to show that by looking at details one may see whether black fossil wood has got its aspect by fire or water.

Samples W/55, W/33 found in 1992 during the preparation of the golf course at Wilmsdorf, Doehlen Basin near Dresden, stored in the own collection.

H.-J. Weiss     2021  

[1] A.Jasper, D. Uhl et al.: Evidence of wildfires in the Late Permian …,
      Current Science 110 No3 Feb.2016, 419-423.

[2] D. Uhl, A.Jasper: Und es brannte doch! Fossile Holzkohle als Nachweis von Bränden in Perm und Trias - ein Gelehrtenstreit? (Jan. 2011)

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