“…. Wilfried Latz from Anröchte sent these thin section photographs of its "Sauerlaender Achate" with inclusions of fossil fungi to me … The agates are crack fillings in the stromatolitic iron flint. Because the stromatolithic iron flint is mentioned being developed in the Tertiary period, the agate must be younger… Mr. Latz found his specimens in the Limestone Quarry Liet in the eastern wall….You can find a scientific text about to the fossil inclusions in these agates at Springerlink ”
As pers.report of A. Kittelmann.
In the following the abstract of the article ( the complete article is here):
“...Fossil iron stromatolites, formed by fungi, have been found near Warstein, W. Germany. The stromatolitic and massive ferruginous quartzes are always confined to karstic hollow molds of the Devonian “Massenkalk”. The few autochthonous occurrences show that these are chalcedony-quartz-silicifations of mainly ac-oriented, corrosively widened cracks. A mineralization temperature of about 120°C was found by microthermometrical measurements. Druses in ferruginous quartz sometimes carry clear, prismatic to pseudocubic quartzes embedding fungal mycelia. The fungal filaments are generally encrusted with goethite and appear in stromatolitic, massive and patch-like forms. The fungi can be referred to the order Mucorales and the genera Chaetomium, Preussia, and Papulaspora. An Oligocene/Miocene age is presumed according to the development of the karst, the mineral paragenesis, and microthermometrical measurements. The fungal mycelia grew on cracks and other hollow molds of the Devonian “Massenkalk” (massive reef limestones) in the vadose zone. Percolating water transported organic C originating from the soil-/sedimentary cover as a substratum for the fungi as well as chelated and free Fe2+ and colloidal Fe3+. Iron was precipitated on the cell walls of the fungal filaments, and thus further precipitation was initiated. Repending from the Eh—pH-values, rhythmic, hydrolytically precipitated, colloidal, and iron-rich layers formed. Gradual dehydration finally led to the formation of goethite. Gel splits and settling structures have often been observed in these regions. The silicification starting within this phase conserved the partially rather fragile structures.
The iron stromatolites of Warstein are probably the first examples of fossil biogenic, non-photosynthetic laminites. These biogenic structures within the iron-quartz squences caused by microbial action show amazing parallels to rocks of the Precambrian cherty banded-iron formation (BIF)....”
from the article of Manfred Kretzschmar