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A rangeomorph holdfast trace fossil from the Ediacara formation, Rawnsley quartzite of the Flinders Range, South Australia. This specimen is Medusina mawsoni, so called because it was until recently thought to be a jellyfish, but is now believed to be the attachment point of a fractal rangeomorph as Charniodiscus is the point of anchorage for Charnia sp. This one may have been the holdfast point for some species of Rangea. The diameter of the outer circle is 1.5 cm and the fossil is estimated to be 555 million years old.
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Just a note that James Cullison's 1944 monograph on the rocks and fauna of the upper Lower Ordovician of Missouri and Arkansas is now freely available for download or perusal at https://archive.org/details/paper-cullison-1944-the-stratigraphy-of-some-lower-ordovician-formations-of-the This publication has always been devilishly tough to get a hold of. A nice systematic paleontology section deals with the many gastropods and other mollusks as well as the less diverse brachiopods, trilobites, and sponges. The monograph covers the following formations as currently accepted in Missouri: • Smithville Formation • Powell Formation • Cotter Formation • Jefferson City Formation Enjoy and share as you like. Full citation: J. S. Cullison, 1944: "The Stratigraphy Of Some Lower Ordovician Formations Of The Ozark Uplift." The University of Missouri School of Mines and Metallurgy Bulletin Technical Series, Vol. 15, No. 2, 112 pp + 35 pl.
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Precambrian Slowdown in Earth’s Rotation Could Have Affected the Oxygen Content of the Atmosphere
Oxytropidoceras posted a topic in Fossil News
A Slowdown in Earth’s Rotation Could Have Affected the Oxygen Content of the Atmosphere Max Planck Institute, August 2, 2021 The open access paper is: Klatt, J.M., Chennu, A., Arbic, B.K. et al., 2021 Possible link between Earth’s rotation rate and oxygenation. 2 August 2021, Nature Geoscience. DOI: 10.1038/s41561-021-00784-3 A fascinating talk about variations in tides and non-uniform rates of change in Earth's rotation is: A journey through tides in Earth's History Mattias Green, Seds Online, Oct 22, 2000 and Blackledge, B.W., Green, J.A.M., Barnes, R. and Way, M.J., 2020. Tides on Other Earths: Implications for Exoplanet and Palaeo‐Tidal Simulations. Geophysical Research Letters, 47(12), p.e2019GL085746. Yours, Paul H.-
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Hello guys! Please advise if this is a geological formation, or if there is any organic activity - cyanobacteria? Thanks! N.1 N.2 N.3
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This silicified lacustrine Miocene stromatolite is a trace fossil made by a gram-negative photosynthetic blue-green bacteria. The originally limestone stromatolite was formed as a bacterial mat trapped sediment and precipitated limestone as it grew from the lake floor towards the sun. It shows classic convex layering towards the top. The stromatolites occur in tuffaceous and lime rich lake sediments that might be part of the Chalk Canyon Formation that is bounded on the bottom by basaltic lava and volcanic rich conglomerate and sandstone on the top. Locally numerous silicified casts and molds of reed like plants, their roots, and palm wood occur in the lacustrine sediments. Since the area is under possible scientific investigation I will not give a more specific locality. The Arizona Museum of Natural History has fossils from the site per my showing them the site. The taxonomy is very unsettled as is the author of Cyanobacteria. Taxonomy per International Registry of Marine and Nonmarine Genera: https://www.irmng.org/aphia.php?p=taxdetails&id=110 See also: https://link.springer.com/article/10.1007/s10750-014-1971-9 “The cyanobacteria are named under Botanical and Bacteriological Codes, and the usage of both systems at the same time causes considerable confusion as the rules of the Botanical Code are quite different from those of the Bacteriological one.” Photo 1: detail of photo 2. Photo 2: 9” wide polished cross section cut and polished courtesy of Stan Celestian. Photo 3: 6” wide polished cross section of another side. Photo 4: top of colony. Photo 5: bottom of colony. Fossil Cyanobacteria & stromatolite overview: https://ucmp.berkeley.edu/bacteria/cyanofr.html Interesting paper that suggest Cyanobacteria created calcified structures because of interactions with viruses: White, R. A., 3rd, Visscher, P. T., & Burns, B. P. (2021). Between a Rock and a Soft Place: The Role of Viruses in Lithification of Modern Microbial Mats. Trends in microbiology, 29(3), 204–213. https://doi.org/10.1016/j.tim.2020.06.004 https://newsroom.unsw.edu.au/news/science-tech/stromatolites-–-fossils-earliest-life-earth-–-may-owe-existence-viruses
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Would anyone be interested in trading for high quality unpolished Ordovician STROMATOLITES of various sizes from a few ounces to up to ten pounds in weight? Fossils have been collected in Wisconsin USA (from the Oneota Formation). I have a large number of every size from a few ounces to ten pounds. Most all contain classic stromatolite features including concave (dome-like) tops, concave bottoms and multiple apical laminae (visible from side-view). I am attaching representative photos of a few specimens. Many more are available based on what you may desire. Additional photos can be sent. Let me know if you' are interested. I would be willing to consider almost any kind of fossil in trade to expand my collection. Crinoids, trilobites, blastoids, brachiopods, plant or animal fossils, and especially maclurites are examples. THANKS. ,
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