Eerie shapes athwart microbial layer
stacks - (4)
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 cherts since
it "feels"
the texture 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
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