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Went back to extract a 35 cm long piece of silicified root out of the Miocene Chalk Canyon Formation near Black Canyon City north of Phoenix. Had to work around the couple of heavy low elevation snow storms this year which have helped to greatly lessen a multi year drought. A geological hammer and a large star point chisel helped get the root out of the tuffaceous sandstone. I did not expect to get it out it one piece; I had to glue it together. After extracting the root, I looked in the surrounding basalt for agates and druzy amigdules. The prize was a 4 cm high manganese-rich crystallized dendrite growing in and amongst small quartz crystals in an amigdule. See other quartz druzies.
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I found lots of petrified wood in the lower part of the Miocene Chalk Canyon Formation north of Phoenix. The layer is mostly sandy and pumaceous. Does anyone know what the siliceous 1mm long elongated spheres are or how they formed? Could they be fecal pellets, fungi or other fossils. I have seen similar structures associated with California Miocene palm wood. @paleoflor Penny is 19 mm across.
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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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Here are some more lake wetland Miocene plant fossils from NE of Phoenix. I found large outcrops of silicified reeds in growth position. I found several pieces of palm: a first for this area. Photos 1 & 2: palm. Photos 3 & 4: top and bottom of reeds. Photos 5 & 6: more reeds.
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I found these in a Miocene lake bed formation northeast of Phoenix, Arizona. The lake beds are deposited along with volcanic rocks and are probably part of the Chalk Canyon Formation. The lake beds have pieces of agatized plant material. Any ideas of what the plants might be? I am especially interested in the molds of a jointed plant shown in the first three photos. @paleoflor Photo about 6cm high. Detail of first photo. Filled center of plant stem ~0.7mm. Depressed mold of stem ~ 3mm across. Height of photo ~2.5cm. Detail of first photo. Center of stem ~ 1mm. Mold of stem ~3mm across. Length of stem ~5.5cm. Bunch of stems average of 5mm across. Cross section of above photo. Typical stems each about 2 - 4mm across. Possible stromatolite/algae structure.
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