A big Psaronius from Döhlen basin, Saxony      
deutsche Version

Chert layer fragments with parts of a Lower Permian vegetation were found in considerable numbers in the small Döhlen basin in the 1990s after this type of fossils from the scientifically important site had been neglected by palaeobotanists, in the absence of new finds, for about a century. The renewed interest was brought about by Gert Müller, whose purposeful search on and around the small area named "Kleinnaundorf fields" in old palaeobotany texts yielded cherts with foliage of the tree fern Scolecopteris ( = Maggot fern, see Permian Chert News 2) and with parts of squeezed stems of this fern, known as Psaronius, from 1985 on.
Own activities in fossil collecting in the Döhlen basin got a boost by contact with M. Barthel [1] und W. Reichel [2]. A useful hint by Herbert Wossilat concerning construction pits in chert-bearing sediments led to the recovery of lots of fossiliferous chert and petrified wood samples and to the discovery of the biggest Psaronius hitherto found in the Döhlen basin.

Cross-section of biggest Psaronius from Döhlen basinImage: Cross-section of the largest Psaronius found hitherto in the Lower Permian Döhlen basin, unevenly compressed before silicification, width 36.5cm, width of the picture 29.5cm.

Parts of tree ferns trunks are found in the Döhlen Basin usually as components of silicified peat or swamp matter, more or less squeezed flat, with estimated stem diameters seldom exceeding 20cm. Thus they never make a sight as magnificient as those found at Chemnitz [3] which apparently became quickly silicified whilst buried in volcanic ash without being compressed. Separate Psaronius samples, like the big chunks of petrified wood not embedded in chert and less deformed, as the one shown here, are rare exceptions in the Döhlen basin. (See also
 Permian Chert News 6.)
The present sample is thoroughly silicified but was already slightly damaged before. Some details are enigmatic. The 10cm wide roughly circular area set off by colour on the left is an artifact of silicification, possibly controlled by some kind of rot, propagating outward from the anatomic centre, whose remnants are vaguely seen inside. (Remember that any Psaronius stem, except for the uppermost part, consists of a more or less broad centre with sclerenchyma strands surrounded by a more or less thick mantle of aerial roots.) Asymmetric growth is a common phenomenon, also known with Psaronius from Chemnitz [3].
The presence of the nearly circular ring beside flattened aerial roots seems to indicate that low pH due to decay induced early silicification within the circular area so that it kept its form while the vicinity became squeezed. This process must have been a complex one, judging from the different deformation of the aerial roots, which are either flattened or compressed and kinked lengthwise.

This specimen of 30kg was found in 1995 at Freital-Burgk, Bernhardts Weg 25, along with numerous samples of fossiliferous chert and petrified wood with weight ranging from 27g to 47kg. It had been cut into 8 parts. One slab had been acquired by the Museum für Naturkunde Chemnitz in exchange for a Psaronius slab from Chemnitz, and is pictured in [3], Fig.195. The slab pictured above is kept in the own collection, labelled Bu4/52.4.  Part Bu4/52.1 is owned by Frank + Uta Lippert, whose cooperation was helpful in recovering the finds on their property.

H.-J. Weiss     2012

[1]  M. Barthel: Der Madenstein aus dem Rotliegenden des Windberges.
     in: H. Prescher u.a.: Zeugnisse der Erdgeschichte Sachsens, Leipzig 1987, S.121.
[2]  K. Thalheim, W. Reichel, Th. Witzke: Die Minerale des Döhlener Beckens.  Schriften Staatl. Mus. Geol. Mineral. Dresden 3(1991), S.53.

[3]  R. Rößler: Der versteinerte Wald von Chemnitz. Naturkunde-Museum Chemnitz, 2001.
Scolecopteris pinnule cross-section, Sardinia Permian Chert News 9

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