... chert from Boertewitz near Leisnig ...

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In 2001, during excavations at Boertewitz supervised by Landesamt fuer Umwelt und Geologie and Bergakademie Freiberg, a big lengthy chert pod was found in-situ between layers of Rotliegend lake sediments of partly volcanic origin (Oschatz formation) with a rich fossil fauna. The fossil content of the mainly red chert is sparse and restricted to poorly preserved wood and a few ostracods. The chert is rather crystalline but contains some small agates, too.

Doubts arise concerning its interpreatation as a mere chert pod. The fragment shown at the 4th Chert Meeting in 2005, representing a cross-section of the pod, reveals a small wooden axis with central pith and peculiar concentic zonation. These features are also seen on other sections of the lengthy pod. Such structure suggests the idea that it might be a big squeezed lycophyte trunk. Remember that lycophyte trunks are made up of a small amounts of pith and wood (about 10% each) while the rest is cortex. So the larger part of the red chert could be cortex, much decayed before silicification. A few ostracods are seen therein. Did they possibly live in the decaying cortex ? As an alternative interpretation, a comparatively small wooden (gymnosperm?) axis could be beset with thick algal growth. The length of the pod is 2 to 3 meters at least, which makes the interpretation as a trunk a probable one. Unfortunately, the preservation of the tissue is so poor that the problem cannot be settled now. Investigations by P.TSCHERNAY and C.BRACHMANN (BAF) are still going on and hopefully will yield more information.

 
 

excavation Boertewitz 2001 by LfUG and BAF

chert from Boertewitz

chert with ostracods

P323Ho, chert with trunk and ostracods

chert pod, shown at the Chert Meeting 2005

     

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