Eerie shapes athwart microbial layer stacks - (4)
deutsche Version
shapes across layer stack
Silicification phenomena in red cherts from the Döhlen basin apparently defying any explanation have been discussed in Permian Chert News 18 , 27 , 28 . Another impressive one of the structures awaiting explanation is shown here.
 
Fig.1: Stack of microbial sheets stained with yellowish iron ore deposited as a result of oxygen production, later superposed by hematite of unknown origin arranged in fancy shapes. Image width 3.5mm.


The
enigmatic process which had been at work here has not only provided the large shapes resembling an Art Nouveau decoration but has partially stained several layers in the stack which are seen in cross-section as thin red lines. This means that this process of eery shape formation is largely but not completely insensitive to pre-existing structures in the chert since it "feels" the layered structure of what had been a stack of sheets.
Some of the "eerie shapes", like those in
Permian Chert News 18, might mislead the observer to the assumption that they had grown from cracks. This is excluded by thin layers seen traversing alleged cracks without being interrupted, as in this picture. 
Unfortunately, these observations do not contribute to an explanation of the
"eerie shapes". Maybe more pictures of similar shapes will do.
(revised version)  

Sample:  H/278.2, old fragment (1kg) of a Lower Permian chert layer, found in 2000 among glacial river deposits at Hänichen, Döhlen basin, Freital near Dresden, Saxony.

H.-J. Weiss      2022

Scolecopteris pinnule cross-section, Sardinia Permian Chert News36
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