New Members Bill J Posted January 29 New Members Share Posted January 29 I was gifted a rock specimen from the estate of a professional geologist. I was immediately attracted to it as a tall, columnar structure very coral like. It has been cleanly sawn at the base and it layered, laminae structure immediately indicated stromatolite. It is about 15 inches tall and 5.5 inches at the base; it weighs about 7 pounds. At first I thought it was a fossil but these three things stand out contrary to that. First, it has air voids in it; it is not completely mineralized through. Second, the external layer is cleanly exposed. If it was a fossil, the surrounding matrix must have been highly erodible as the fine detail of the outside layer (visible exterior) is remarkable. Third, consistent with #1 and #2 the "rock" has not been metamorphosed. We have fossil stromatolites here in Minnesota and they are embedded structure in Mary Ellen Jasper, which is a beautiful rock. Unfortunately, I have no idea where this came from. The dad of my friend who gave it to me lived in South Dakota and was in the Pacific Theatre in WWII, but was not known to be much of a traveler otherwise. Based on my 3 reasons above, I think this may be a specimen of a modern, extant stromatolite that somehow ended up with the geologist. I know there are living modern stromatolites with columnar structure at Pavilion Lake BC, and at Lago los Centas in Porvenir, Tierra del Fuego, Chile. Certainly there are fossil examples of columns too in the record. Really just looking to see if anyone on this forum has seen anything like this before? It is beautiful in its own way. Thanks in advance. Bill J. 1 Link to comment Share on other sites More sharing options...
Tidgy's Dad Posted January 29 Share Posted January 29 I think it is maybe a speleotherm/ stalactite/ stalagmite. 1 1 5 Life's Good! Tortoise Friend. Link to comment Share on other sites More sharing options...
FranzBernhard Posted January 29 Share Posted January 29 Or some kind of tufa? Speleothemes are not that porous, usually? Anyways, not a stromatolithe. Franz Bernhard 1 1 Link to comment Share on other sites More sharing options...
New Members Bill J Posted January 29 Author New Members Share Posted January 29 These are stromatolites in Tierra del Fuego. There is a morphological similarity, especially the "bends" that appear to match my speciment...plus the exterior "crust-like" surface... Link to comment Share on other sites More sharing options...
New Members Bill J Posted January 29 Author New Members Share Posted January 29 Here's another more close-up. Credit to Jason Frels as the photographer. This is at a national biological munument in Chile. Link to comment Share on other sites More sharing options...
FranzBernhard Posted January 29 Share Posted January 29 So we all got it wrong... Link to comment Share on other sites More sharing options...
marguy Posted January 29 Share Posted January 29 these images of stromatolites are superb, but I still stick to the idea of tufa put forward by Franz. 1 Link to comment Share on other sites More sharing options...
DPS Ammonite Posted January 29 Share Posted January 29 15 hours ago, Bill J said: I think this may be a specimen of a modern, extant stromatolite that somehow ended up with the geologist. I know there are living modern stromatolites with columnar structure at Pavilion Lake BC, and at Lago los Centas in Porvenir, Tierra del Fuego, Chile Can you find a paper about those stromatolites in Chile that show a cross section of one? My goal is to leave no stone or fossil unturned. See my Arizona Paleontology Guide link The best single resource for Arizona paleontology anywhere. Link to comment Share on other sites More sharing options...
westcoast Posted January 29 Share Posted January 29 A longitudinal section might show the irregular convex to horizontal layers typical of stromatolites. Without any other information we are only guessing. 1 Link to comment Share on other sites More sharing options...
Yoda Posted January 29 Share Posted January 29 26 minutes ago, westcoast said: A longitudinal section might show the irregular convex to horizontal layers typical of stromatolites. Without any other information we are only guessing. I am not an expert. But to me, the layers look like they are vertical. Are they horizontal as well ??? MotM August 2023 - Eclectic Collector Link to comment Share on other sites More sharing options...
New Members Bill J Posted January 30 Author New Members Share Posted January 30 Thanks all. Really good thoughts here. Certainly the pictures of tufa structures are in the running. Apparently there is new research indicating the presence of a biofilm for at least some types of these to form. I've not found a picture of a lateral cross-section but would expect it to be layered. Speaking of cross-sections... The only cross-section of my specimen is that showing at the base cut. The "top" is uncut and looks very similar to the base cut, however the laminae are much closer together with minimal voids. I'll try to get a picture for that. As for a vertical cross-section, that will not be happening with my specimen but it is fully understood how valuable having that would be. As best I can tell it appears to be layered vertically all the way through so I agree with WestCoast this is just guessing. So my response to Yoda is no, they do not appear horizontal BUT... When you look at the bottom off-left of the cross-section you see a hole that might be a tube going up into the structure. I measured into the hole and its 1 cm going in at most but who knows how long it might have been going the other direction. Back to the tufa hypothesis this certainly is more realistic as these are found here in the US without having to go down to Patagonia. I may actually have access to some limited lab analysis and that could go a long way on the tufa vs stromatolite front. There is a researcher in Chile that I can reach out to for a possible cross-section image from the other pics shown above. Finally, I'm not sure how a "geologic" process would produce the asymmetrical layer structure that essentially starts at the bottom center and progressively "radiates" the layering up the image. What I mean is that although this thing is columnar its growth is only on one side. I attributed that to more of biological process from the cyanobacteria doing their thing that what my occur from progressive wetting/drying cycles in a mineral laden water environment. Thanks again from a newbie. Bill J. Link to comment Share on other sites More sharing options...
New Members Bill J Posted January 30 Author New Members Share Posted January 30 9 hours ago, DPS Ammonite said: Can you find a paper about those stromatolites in Chile that show a cross section of one? I'll see what I can come up with. Thanks for asking. Link to comment Share on other sites More sharing options...
Lone Hunter Posted January 30 Share Posted January 30 3 1 Link to comment Share on other sites More sharing options...
MarcoSr Posted January 30 Share Posted January 30 Below are figures from "Marco Campos-Venuti 2022 Biominerals microbial life in Agates and other Minerals" showing tufa from Lake Van, Turkey and Mono Lake and Pyramid Lake, Nevada. Tufa Lake Van, Turkey: Tufa Mono Lake and Pyramid Lake, Nevada: Marco Sr. 2 1 "Any day that you can fossil hunt is a great day." My family fossil website Some Of My Shark, Ray, Fish And Other Micros My Extant Shark Jaw Collection Link to comment Share on other sites More sharing options...
DPS Ammonite Posted January 30 Share Posted January 30 45 minutes ago, MarcoSr said: Below are figures from "Marco Campos-Venuti 2022 Biominerals microbial life in Agates and other Minerals" showing tufa from Lake Van, Turkey and Mono Lake and Pyramid Lake, Nevada. Tufa Lake Van, Turkey: Looks like best possibility of ones noted. 1 My goal is to leave no stone or fossil unturned. See my Arizona Paleontology Guide link The best single resource for Arizona paleontology anywhere. Link to comment Share on other sites More sharing options...
New Members Bill J Posted January 30 Author New Members Share Posted January 30 17 minutes ago, MarcoSr said: Below are figures from "Marco Campos-Venuti 2022 Biominerals microbial life in Agates and other Minerals" showing tufa from Lake Van, Turkey and Mono Lake and Pyramid Lake, Nevada. Tufa Lake Van, Turkey: Tufa Mono Lake and Pyramid Lake, Nevada: Marco Sr. Thanks Marco. This is great stuff. At least for the Figure 2.10, the drawing and cross-sections are identified as microbialites, of which stromatolites fall into that category. Tufa structures apparently have a unique origin story with different biogeochemistry than stromatolites. Now my question is how to characterize my specimen? I don't think it qualifies as a fossil, but it's more than just a rock. Again, thanks. Bill J. Link to comment Share on other sites More sharing options...
Fossildude19 Posted January 30 Share Posted January 30 I'd classify it as a sedimentary or geologic structure. 1 Tim - VETERAN SHALE SPLITTER VFOTM --- APRIL - 2015 IPFOTM -- MAY - 2024 _________________________________________________________________________________ "In every walk with nature one receives far more than he seeks." John Muir ~ ~ ~ ~ ><))))( *> About Me Link to comment Share on other sites More sharing options...
FranzBernhard Posted January 30 Share Posted January 30 This is also not so bad, with many very nice pics: Handbook for the study and description of microbialites (dmp.wa.gov.au) free pdf Franz Bernhard 1 1 Link to comment Share on other sites More sharing options...
MarcoSr Posted January 30 Share Posted January 30 5 hours ago, Bill J said: Now my question is how to characterize my specimen? a columnar microbialite or a microbialitic column Marco Sr. 1 1 "Any day that you can fossil hunt is a great day." My family fossil website Some Of My Shark, Ray, Fish And Other Micros My Extant Shark Jaw Collection Link to comment Share on other sites More sharing options...
New Members Bill J Posted January 31 Author New Members Share Posted January 31 On 1/29/2024 at 9:54 AM, DPS Ammonite said: Can you find a paper about those stromatolites in Chile that show a cross section of one? Hello DPS. As best I can tell Dr. Jorge Rabassa out of Chile is the "expert" among several researchers on the Lago los Cisnes stromatolites. Here is one of his papers: https://www.academia.edu/79895667/Living_and_fossil_microbialites_in_Laguna_de_Los_Cisnes_Southernmost_Chile_A_duel_between_biotic_and_abiotic_processes I've not seen any cross-sections and would not have seen anything at all if not for Jason Frels taking a vacation trip to Tierra del Fuego and having a day trip out to the "stromatolite park." I have communicated with him and he's not a fossil or rock person, just a very good photographer. In my quest to understand my specimen, I've come to realize that the very hostile conditions in many parts of Chile provide a microbialite laboratory. I had no idea. Finally, in case you don't know a little closer to home here's what growing in Pavilion Lake BC: This was the site of a NASA exobiology research project in the late 2000s. Pavilion Lake occurs in karst bedrock with high calcium/mineral water quality. I originally thought this might be where my columnar microbialite came from. Back to Dr. Rabassa, he is the head of the major scientific research institute in Chile. I'm sure he's open to contact with anyone interested in microbialites. Bill J. Link to comment Share on other sites More sharing options...
New Members Bill J Posted February 3 Author New Members Share Posted February 3 On 1/30/2024 at 2:16 PM, MarcoSr said: a columnar microbialite or a microbialitic column Marco Sr. Thanks again Marco for your feedback. I see from this and other posts you have a strong interest in stromatolites. Below is a link with some pictures of fossil formations here in Northern Minnesota related to mining of iron formations that's been underway for over 100 years. The webpage is some notes from a field trip back in 2012 at the former LTV Mine Site now owned by PolyMet. This is all private property but I myself hope to visit it someday. What's very cool is that it was of course the cyanobacteria-stromatolites that created the oxygen that precipitated out the dissolved iron in the ancient seas in the first place That's what the geology of this area is all about. Here's the link: earthscienceguy: Minnesota Geology Monday - Stromatolites (mnearthscienceguy.blogspot.com) I pulled a couple of pictures: Again, thanks. Bill J. 2 Link to comment Share on other sites More sharing options...
Wrangellian Posted May 7 Share Posted May 7 (edited) On 2/3/2024 at 9:57 AM, Bill J said: Thanks again Marco for your feedback. I see from this and other posts you have a strong interest in stromatolites. Below is a link with some pictures of fossil formations here in Northern Minnesota related to mining of iron formations that's been underway for over 100 years. The webpage is some notes from a field trip back in 2012 at the former LTV Mine Site now owned by PolyMet. This is all private property but I myself hope to visit it someday. What's very cool is that it was of course the cyanobacteria-stromatolites that created the oxygen that precipitated out the dissolved iron in the ancient seas in the first place That's what the geology of this area is all about. Here's the link: earthscienceguy: Minnesota Geology Monday - Stromatolites (mnearthscienceguy.blogspot.com) I pulled a couple of pictures: Again, thanks. Bill J. Tiny pictures! Glad you provided the link where they are much bigger, thanks for the info. Edited May 7 by Wrangellian Link to comment Share on other sites More sharing options...
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