Jforce91 Posted January 30, 2019 Share Posted January 30, 2019 Hey guys. In NZ we have quite a few volcanoes, and luckily for me living in christchurch, the most recent eruption in the south island was about 20 mya. On the "vanished world" trail, there is a preserved basaltic volcanic dyke/sill that has been injected into the strata beneath an ancient lagoon. While I'm aware that these magmatic intrusions don't break the surface, there is a broad fossil horizon not far from the top most termination of the sill, with beautiful small spirulla (?) (Some kind of elongate fossil snail) preserved in the rock. I was wondering, that as I mentioned before that this fossil horizon is not too far from the intrusion, just how much heat or mineral replacement does it take for igneous rocks the the associated hydrothermal minerals to completely destroy/deform/disfigure fossils in these kinds of geologic environments? I have included a rough sketch. Like all great geologic exposures, it occurs at a public road cutting, to provide context. Link to comment Share on other sites More sharing options...
DeepTimeIsotopes Posted January 30, 2019 Share Posted January 30, 2019 I’d say this is highly dependent on the type of rock the fossils are in and the type of preservation the fossils are, and proximity to the sill. Pyrite itself can handle up to ~1194°C before melting while carbon films can only handle a couple hundred and if oxygen is present for either they’re pretty much toast. Any hydrothermal water flow has some serious potential to mess up any fossils nearby. Of course, if they’re aragonitic they could be altered to calcite. Calcite also recrystallizes with heat and pressure applied. Just burial heat was enough to severely recrystallize my cephalopod here. But there are numerous cases of metamorphism not completely destroying fossils. In fact, also in New Zealand are some blueschist facies that underwent high pressure, low temperature (200-500°C) metamorphism where the plant fossils inside turned to graphite (due to the pressure) galvez2012.pdf Here’s another where the original shale turned into a greenschist at a low temperature (300-500°C) and low pressure. It had changed the composition of the rock and removed a lot of the carbon content.Greenschist-facies_metamorphism_of_the_B.pdf I personally have found calcitic fossils in limestone near a pluton 100m away much like that sill where they had not undergone a lot of change except that a lot of talc had been depositited in the matrix. So I guess it depends on the proximity to the sill, the type of matrix, the type of rock, and any hydrothermal flow. Basically the only way to know is to collect the rock at the top of the sill and see what happened. 5 Each dot is 50,000,000 years: Hadean............Archean..............................Proterozoic.......................................Phanerozoic........... Paleo......Meso....Ceno.. Ꞓ.OSD.C.P.Tr.J.K..Pg.NgQ< You are here Doesn't time just fly by? Link to comment Share on other sites More sharing options...
ynot Posted January 31, 2019 Share Posted January 31, 2019 There is always the possibility that the dyke predates the lagoon and was almost exposed by erosion before the fossils were laid down. 1 Darwin said: " Man sprang from monkeys." Will Rogers said: " Some of them didn't spring far enough." My Fossil collection - My Mineral collection My favorite thread on TFF. Link to comment Share on other sites More sharing options...
piranha Posted January 31, 2019 Share Posted January 31, 2019 Chappell, W.M., Durham, J.W., Savage, D.E. 1951 Mold of a rhinoceros in basalt, Lower Grand Coulee, Washington. Geological Society of America Bulletin, 62(8):907-918 WEB LINK Antoine, P.O., Orliac, M.J., Atici, G., Ulusoy, I., Sen, E., Çubukçu, H.E., Albayrak, E., Oyal, N., Aydar, E., Sen, S. 2012 A rhinocerotid skull cooked-to-death in a 9.2 Ma-old ignimbrite flow of Turkey. PloS ONE, 7(11):e49997 PDF LINK Iurino, D.A., Bellucci, L., Schreve, D., Sardella, R. 2014 Exceptional soft tissue fossilization of a Pleistocene vulture (Gyps fulvus): new evidence for emplacement temperatures of pyroclastic flow deposits. Quaternary Science Reviews, 96:180-187 PDF LINK 4 Link to comment Share on other sites More sharing options...
DeepTimeIsotopes Posted January 31, 2019 Share Posted January 31, 2019 1 hour ago, piranha said: Chappell, W.M., Durham, J.W., Savage, D.E. 1951 Mold of a rhinoceros in basalt, Lower Grand Coulee, Washington. Geological Society of America Bulletin, 62(8):907-918 WEB LINK Antoine, P.O., Orliac, M.J., Atici, G., Ulusoy, I., Sen, E., Çubukçu, H.E., Albayrak, E., Oyal, N., Aydar, E., Sen, S. 2012 A rhinocerotid skull cooked-to-death in a 9.2 Ma-old ignimbrite flow of Turkey. PloS ONE, 7(11):e49997 PDF LINK Iurino, D.A., Bellucci, L., Schreve, D., Sardella, R. 2014 Exceptional soft tissue fossilization of a Pleistocene vulture (Gyps fulvus): new evidence for emplacement temperatures of pyroclastic flow deposits. Quaternary Science Reviews, 96:180-187 PDF LINK Thanks for adding these. These are great examples of extrusive volcanics in contact with the organisms. One day, I’ll own a fossil in igneous rock. Maybe I should add that to my bucket list.Mine were alterations of the fossilized organisms in the matrix after they were fossilized which is a big difference for you non-geologists reading. Each dot is 50,000,000 years: Hadean............Archean..............................Proterozoic.......................................Phanerozoic........... Paleo......Meso....Ceno.. Ꞓ.OSD.C.P.Tr.J.K..Pg.NgQ< You are here Doesn't time just fly by? Link to comment Share on other sites More sharing options...
DeepTimeIsotopes Posted January 31, 2019 Share Posted January 31, 2019 2 hours ago, ynot said: There is always the possibility that the dyke predates the lagoon and was almost exposed by erosion before the fossils were laid down. If there is no alteration in the fossils and no contact metamorphism, then I agree with this statement. Each dot is 50,000,000 years: Hadean............Archean..............................Proterozoic.......................................Phanerozoic........... Paleo......Meso....Ceno.. Ꞓ.OSD.C.P.Tr.J.K..Pg.NgQ< You are here Doesn't time just fly by? Link to comment Share on other sites More sharing options...
ynot Posted January 31, 2019 Share Posted January 31, 2019 33 minutes ago, UtahFossilHunter said: . One day, I’ll own a fossil in igneous rock. When I was 12, I discovered a bunch of leaf fossils in a tertiary lahar on the crest of the sierra nevada mountains. 1 Darwin said: " Man sprang from monkeys." Will Rogers said: " Some of them didn't spring far enough." My Fossil collection - My Mineral collection My favorite thread on TFF. Link to comment Share on other sites More sharing options...
DeepTimeIsotopes Posted January 31, 2019 Share Posted January 31, 2019 6 minutes ago, ynot said: When I was 12, I discovered a bunch of leaf fossils in a tertiary lahar on the crest of the sierra nevada mountains. Dang, that would be cool to see. It’s been a goal of mine to get a fossil in each rock type. Of course, I’ve got fossils in sedimentary rock, and I’ve got fossils in metamorphic rock but none in igneous rock. Did you collect any? 1 Each dot is 50,000,000 years: Hadean............Archean..............................Proterozoic.......................................Phanerozoic........... Paleo......Meso....Ceno.. Ꞓ.OSD.C.P.Tr.J.K..Pg.NgQ< You are here Doesn't time just fly by? Link to comment Share on other sites More sharing options...
Jforce91 Posted January 31, 2019 Author Share Posted January 31, 2019 Thanks for the info guys. as far as I'm aware, a lot of NZ's mesozoic limestones and sandstones contain a lot of volcanoclastic material thanks to some stupid disagreement we had with the Australian plate (Aka the opening of the tasman sea) I'm a bit fuzzier on the Cenozoic stuff, and I'm big into volcanoes and igneous processes so that's why i thought i'd ask around. 1 Link to comment Share on other sites More sharing options...
ynot Posted January 31, 2019 Share Posted January 31, 2019 6 minutes ago, UtahFossilHunter said: . Did you collect any? We went camping at Silver lake, in the Sierra Nevada mountains when I was 12. I made My brother take a hike to the pyroclastic formations east of the lake. At the base of the formation there are several places where trees had piled up during the event. These acted as a filter that allowed leaf impressions to be preserved. I collected several, none of which I could identify. My Dad worked for the Calif board of education, and set up a meeting with the head of the paleontology department at the university of california- Davis. This man Identified the leafs as willow, oak, birch and avocado. He was so excited about My discovery (no fossils had been previously reported from this volcanic formation!) that My dad had to take us up to the site the next weekend. When I next returned in My 20's there was a well defined path straight to the site. This was My first contribution to science, because the Paleontologist kept My leaf fossils. I also found My first petrified wood in this area. willow leaf avocado leaf Petrified wood.. Excerpt from ... 4 Darwin said: " Man sprang from monkeys." Will Rogers said: " Some of them didn't spring far enough." My Fossil collection - My Mineral collection My favorite thread on TFF. Link to comment Share on other sites More sharing options...
DeepTimeIsotopes Posted January 31, 2019 Share Posted January 31, 2019 12 minutes ago, ynot said: We went camping at Silver lake, in the Sierra Nevada mountains when I was 12. I made My brother take a hike to the pyroclastic formations east of the lake. At the base of the formation there are several places where trees had piled up during the event. These acted as a filter that allowed leaf impressions to be preserved. I collected several, none of which I could identify. My Dad worked for the Calif board of education, and set up a meeting with the head of the paleontology department at the university of california- Davis. This man Identified the leafs as willow, oak, birch and avocado. He was so excited about My discovery (no fossils had been previously reported from this volcanic formation!) that My dad had to take us up to the site the next weekend. When I next returned in My 20's there was a well defined path straight to the site. This was My first contribution to science, because the Paleontologist kept My leaf fossils. I also found My first petrified wood in this area. willow leaf avocado leaf Petrified wood.. Excerpt from ... Great story. That’s awesome! You were a paleontologist at 12 and didn’t even know it. The best leaf fossils I’ve found so far were in the concrete in my driveway. Each dot is 50,000,000 years: Hadean............Archean..............................Proterozoic.......................................Phanerozoic........... Paleo......Meso....Ceno.. Ꞓ.OSD.C.P.Tr.J.K..Pg.NgQ< You are here Doesn't time just fly by? Link to comment Share on other sites More sharing options...
ynot Posted January 31, 2019 Share Posted January 31, 2019 23 minutes ago, UtahFossilHunter said: You were a paleontologist at 12 and didn’t even know it. Oh, I knew it. 1 Darwin said: " Man sprang from monkeys." Will Rogers said: " Some of them didn't spring far enough." My Fossil collection - My Mineral collection My favorite thread on TFF. Link to comment Share on other sites More sharing options...
DPS Ammonite Posted January 31, 2019 Share Posted January 31, 2019 1 hour ago, ynot said: When I was 12, I discovered a bunch of leaf fossils in a tertiary lahar on the crest of the sierra nevada mountains. What are the details of the formation/age that the flora came from and was a paper published? Was Dan Axlerod the UC Davis professor that kept the fossils? 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...
ynot Posted January 31, 2019 Share Posted January 31, 2019 17 minutes ago, DPS Ammonite said: What are the details of the formation/age that the flora came from and was a paper published? Was Dan Axlerod the UC Davis professor that kept the fossils? Virgilian replied with this... "If your paleobotanical finds came between 1967 and the first half of 1998, that "head of the paleontology department at the university of california- Davis" would have been none other than the famed paleobotanist Daniel I. Axelrod (born July 16, 1910; passed away June 2, 1998), a name one will surely encounter sooner or later if one investigates the Cenozoic fossil leaves of California and Nevada, in particular." Since this happened in 1969 it was Prof. Axelrod. I do not know if any papers were written on this site. Darwin said: " Man sprang from monkeys." Will Rogers said: " Some of them didn't spring far enough." My Fossil collection - My Mineral collection My favorite thread on TFF. Link to comment Share on other sites More sharing options...
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