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Showing results for tags 'microbialites'.
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...also oncolites, thrombolites, microbialites, related things can be included. We can also include BIFs (Banded Iron Formations) and suchlike, being indirectly created by early life, but there will be a preference for biogenic stuff. I don't think this topic has been started already (I would have thought it has), so it falls to me. If one already exists, maybe this can be merged with it and I'll edit accordingly. Some of us have been showing each other our stromatolite finds/acquisitions in other topics and it seemed like a good idea to make a central depot. Links to preexisting posts are welcome, if you don't want to make duplicate posts here. I'll start it off with some of mine. I did a photographing blitz and then finally got done editing them. Some of the slices have not yet been polished, so I had to photo them wet, though some wouldn't hold the water so I gave up and photo'd them dry. First, my Australian examples... Apparently this one is (mid?) Cambrian, from the Barkly Tableland of the Northern Territory, west of Camooweal, Queensland. I like that it has some of the natural eroded surface as well as the sliced (and thankfully polished) surface: I wish this piece were bigger. It must have at one time passed through the hands of that dealer in England who chops everything up into small pieces to maximize profit, but I don't know. Earaheedia kuleliensis, Paleoproterozoic/Statherian (~1.75 b.y.), Kalele (Kulele?) Limestone, Wiluna, Nabberu Basin, Western Australia: I doubt this one is technically a stromatolite or microbialite - just layers (varves?) of BIF sediment, but it did exist at a time when there was single-celled life on Earth, pumping oxygen into the seawater, turning iron suspended therein into iron oxide which precipitated out to form the Banded Iron formations. And anyway it's too cool to not include. The rockhounds refer to this stuff as 'Snakeskin jasper'. 2.45 b.y. (Paleoproterozoic/Siderian), Weeli Wolli Fm (Hamersley Group), Turee Creek Station, SW of Newman, WA. (Pilbara Region) A couple more BIF pieces from Australia, just because it's so interesting and indirectly biogenic... Rockhounds refer to this stuff as Tiger Iron (ie. Tiger-eye in Banded Iron). I understand there are 2 different locations: the Ord Ranges/Port Hedland location (Cleaverville/Nimingarra Iron Fm, Mesoarchean 3.02-3.1by) and the Marra Mamba/Brockman location (Marra Mamba Fm, Neoarchean 2.6by), both in the Pilbara Region of Western Aus, but I'm not sure how to tell which one this might be from. I lean toward the former as the latter is apparently less common. If anyone has more expertise on this I would appreciate a tip. The Tigereye is a pseudomorph (replacement in silica) of selenite growths in the sediment after deposition, if I'm not mistaken? I need to check that to be more confident. ( wet ^ --- dry v )
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We may Finally know what life on Earth breathed before there was oxygen By Carly Cassella, ScienceAlert The open access paper is: Visscher, Pieter T., Kimberley L. Gallagher, Anthony Bouton, Maria E. Farias, Daniel Kurth, Maria Sancho-Tomás, Pascal Philippot et al. "Modern arsenotrophic microbial mats provide an analogue for life in the anoxic Archean." Communications Earth & Environment 1, no. 1 (2020): 1-10. Yours, Paul H.