Robert Mahorney Posted May 14, 2021 Share Posted May 14, 2021 What kind of layers are these in East Tennessee very fine paper thin black stone, lots of natural right angles and mixed egg shapes and ovals seem to be found in them. 20 feet Above these layers are thicker gray limestone with corals and crinoids Does anyone know the story of these layers Link to comment Share on other sites More sharing options...
Fossildude19 Posted May 14, 2021 Share Posted May 14, 2021 What county is this in? The egg shaped items are concretions - discernable by the concentric layering. The shale looks like a paper shale. Knowing what county this is in could help us narrow down the Formation. 1 Tim - VETERAN SHALE SPLITTER VFOTM --- APRIL - 2015 __________________________________________________ "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...
Robert Mahorney Posted May 14, 2021 Author Share Posted May 14, 2021 Jackson Overton county boarder. See photo Link to comment Share on other sites More sharing options...
JohnGrills Posted May 14, 2021 Share Posted May 14, 2021 I have found similar layers around Kingsport very brittle Link to comment Share on other sites More sharing options...
Plantguy Posted May 15, 2021 Share Posted May 15, 2021 Geologic Maps of the area show surface outcrops of Mfp (Fort Payne formation and the Chattanooga Shale) as well as MSW (St Louis and Warsaw Limestones) in the area. I'm wondering if the dark shale Flaky 'fissile" shale you are seeing might be the Chattanooga Shale? The Fort Payne formation above it in the section has crinoidal lenses.... Hoping someone local can confirm these guesses. Continued hunting success! Regards, Chris Screen shot from NGDB online of the geology of the area showing the light blue (Mfp) areas--Fort Payne Formation and Chattanooga Shale. Also shows light blue with diagonal lines (Msw) of the St Louis & Warsaw limestones. ... https://ngmdb.usgs.gov/Prodesc/proddesc_68531.htm NGDB legend Geologic Units Descriptions in Jackson County from the USGS site https://mrdata.usgs.gov/geology/state/fips-unit.php?code=f47087 2 Link to comment Share on other sites More sharing options...
Robert Mahorney Posted May 15, 2021 Author Share Posted May 15, 2021 Wow this is great information. I learn so much from everyone's input. Love this forum. Thank u so much. Link to comment Share on other sites More sharing options...
ClearLake Posted May 15, 2021 Share Posted May 15, 2021 Now that you know the formation, one can look it up to tell you the exact story, but in general these changes in the rocks reflect a changing sea level and sediment source over time. The thin dark colored rocks are shales that we’re probably deposited in deeper, quieter waters. The sediment that fell out of the water was fine grained muds which accumulated in fine layers probably relatively slowly. The egg shaped objects are concretions, as mentioned, that formed within the sediments after they were deposited, usually by some interaction of fluids moving through the rocks and interacting with the different minerals over time. You can google “concretion” to get more on that story. The limestones reflect a change change in sea level (most likely to shallower water) and also reflect times of relatively little sediment input, in other words, there were no significant rivers dumping mud and sand into the ocean in that area. The carbonates that form the limestones precipitate from the seawater which was probably relatively warm (think of a tropical ocean). Of course there are sands and/or muds mixed in which just show that there were changes in the sediment input over time. There are lots of different processes that can happen to confuse the interpretation, but that is generally what is going on in these Paleozoic rocks. I should have started with: a sea covered your area for millions of years during the time theses rocks were deposited, but maybe that was already obvious to you. 4 Link to comment Share on other sites More sharing options...
Robert Mahorney Posted May 15, 2021 Author Share Posted May 15, 2021 Yes tennes sea lol but I love the info and the details you provide to illuminate the history of how these layers form. Learning so much. You guys "rock" Link to comment Share on other sites More sharing options...
ClearLake Posted May 15, 2021 Share Posted May 15, 2021 2 minutes ago, Robert Mahorney said: Yes tennes sea Haha, good one! Link to comment Share on other sites More sharing options...
EMP Posted May 15, 2021 Share Posted May 15, 2021 14 hours ago, Plantguy said: Geologic Maps of the area show surface outcrops of Mfp (Fort Payne formation and the Chattanooga Shale) as well as MSW (St Louis and Warsaw Limestones) in the area. I'm wondering if the dark shale Flaky 'fissile" shale you are seeing might be the Chattanooga Shale? The Fort Payne formation above it in the section has crinoidal lenses.... Hoping someone local can confirm these guesses. Continued hunting success! Regards, Chris Screen shot from NGDB online of the geology of the area showing the light blue (Mfp) areas--Fort Payne Formation and Chattanooga Shale. Also shows light blue with diagonal lines (Msw) of the St Louis & Warsaw limestones. ... https://ngmdb.usgs.gov/Prodesc/proddesc_68531.htm NGDB legend Geologic Units Descriptions in Jackson County from the USGS site https://mrdata.usgs.gov/geology/state/fips-unit.php?code=f47087 I'd agree with that. OP's photos appear to show an outcrop of the Chattanooga underlying the Fort Payne. The Chattanooga Shale likely represents an anoxic marine environment towards the end of Devonian time, around 360 million years ago. Although the anoxic conditions on the sea floor meant little to no life lived in it, the dark color is the result of out washing of carbon rich, organic matter into the sea, from what I've read likely as a result of increased erosion during the Acadian orogeny. Eventually the Acadian Mountains were weathered away, leading to the deposition of coarser sediments in the Price and Pocono Formations in Appalachia and the deposition of the Fort Payne Limestone in the Kentucky-Tennessee-Georgia area. Limestone often forms in shallower water or when a locality loses it's clastic input. I must say, it's a pretty good looking outcrop! Reminds me of the stuff from northern Ohio. 1 Link to comment Share on other sites More sharing options...
Tetradium Posted May 15, 2021 Share Posted May 15, 2021 18 hours ago, Plantguy said: Geologic Maps of the area show surface outcrops of Mfp (Fort Payne formation and the Chattanooga Shale) as well as MSW (St Louis and Warsaw Limestones) in the area. I'm wondering if the dark shale Flaky 'fissile" shale you are seeing might be the Chattanooga Shale? The Fort Payne formation above it in the section has crinoidal lenses.... Hoping someone local can confirm these guesses. Continued hunting success! Regards, Chris Screen shot from NGDB online of the geology of the area showing the light blue (Mfp) areas--Fort Payne Formation and Chattanooga Shale. Also shows light blue with diagonal lines (Msw) of the St Louis & Warsaw limestones. ... https://ngmdb.usgs.gov/Prodesc/proddesc_68531.htm NGDB legend Geologic Units Descriptions in Jackson County from the USGS site https://mrdata.usgs.gov/geology/state/fips-unit.php?code=f47087 I noticed this mention that it is rich in carbon. After all clay which made up shales can have very different properties of chemicals which can makes for different shapes and properties of shales. Sounds like quite a lot of dead planktons made up a big chuck of this shale which can means moderate deep waters. But in some weird way this is similar to Ordovician Minnesota formation with all the weird rapid changes from sandstone to limestone to shale to limestone. I hadn't found any resources explaining why all this wild changes in sediments or why sea levels changed so much. Sandstone is usually shallower waters but form in underwater canyons as sand drops out first then clay for deeper or calmer waters. Link to comment Share on other sites More sharing options...
Tetradium Posted May 15, 2021 Share Posted May 15, 2021 17 hours ago, ClearLake said: Now that you know the formation, one can look it up to tell you the exact story, but in general these changes in the rocks reflect a changing sea level and sediment source over time. The thin dark colored rocks are shales that we’re probably deposited in deeper, quieter waters. The sediment that fell out of the water was fine grained muds which accumulated in fine layers probably relatively slowly. The egg shaped objects are concretions, as mentioned, that formed within the sediments after they were deposited, usually by some interaction of fluids moving through the rocks and interacting with the different minerals over time. You can google “concretion” to get more on that story. The limestones reflect a change change in sea level (most likely to shallower water) and also reflect times of relatively little sediment input, in other words, there were no significant rivers dumping mud and sand into the ocean in that area. The carbonates that form the limestones precipitate from the seawater which was probably relatively warm (think of a tropical ocean). Of course there are sands and/or muds mixed in which just show that there were changes in the sediment input over time. There are lots of different processes that can happen to confuse the interpretation, but that is generally what is going on in these Paleozoic rocks. I should have started with: a sea covered your area for millions of years during the time theses rocks were deposited, but maybe that was already obvious to you. The only thing I dont understand myself is why was ordovician period so crazy. Sandstone then Limestone then Shale then Limestone again. Such wild variability in sea levels and sedimentary deposits. What changed? What cause so much clay/silt to washed into the sea for a period of time then sudden cut off, leaving behind lime. But you also realize there's a second type of limestone, one that forms from lime created by the decomposition of calcium carbonate bearing dead sea animals. That's why its often called coquina type limestone. Link to comment Share on other sites More sharing options...
Robert Mahorney Posted May 15, 2021 Author Share Posted May 15, 2021 1 Link to comment Share on other sites More sharing options...
Plantguy Posted May 16, 2021 Share Posted May 16, 2021 Awesome outcrops/rock photos! Looks like a great place to poke around in but be very very safe...outcrops with those types of faces/overhangs are/can be very unstable. Regards, Chris Link to comment Share on other sites More sharing options...
Plantguy Posted May 16, 2021 Share Posted May 16, 2021 (edited) 8 hours ago, Tetradium said: The only thing I dont understand myself is why was ordovician period so crazy. Sandstone then Limestone then Shale then Limestone again. Such wild variability in sea levels and sedimentary deposits. What changed? What cause so much clay/silt to washed into the sea for a period of time then sudden cut off, leaving behind lime. But you also realize there's a second type of limestone, one that forms from lime created by the decomposition of calcium carbonate bearing dead sea animals. That's why its often called coquina type limestone. I'm not up on my Paleozoic US geology but I seem to recall there were some substantial Paleozoic glaciation events that occurred causing incredible sea level changes in the Mississippian and Ordovician. I'm sure there was some tectonic things going on as well that may have thrown in some uplifts regionally/with plate movements and general climatic changes as well. Google Mississippian period and Ordovician period geology and youll get to read about how dynamic our planet has been during those periods and over the eons....its mind blowing the scale of change. The Smithsonian Magazine folks referenced a link that is pretty cool that allows you to key in your location on the planet and a time period and you can see the planet and where the continents are and see what parts are submerged during the given time period. Here's that article: https://www.smithsonianmag.com/smart-news/map-lets-you-plug-your-address-see-how-neighborhood-has-changed-over-past-750-million-years-180971507/ Here's the direct link to the interactive map of the globe/planet at dinosaurpictures.org https://dinosaurpictures.org/ancient-earth#0 Regards, Chris Edited May 16, 2021 by Plantguy 1 Link to comment Share on other sites More sharing options...
Tetradium Posted May 16, 2021 Share Posted May 16, 2021 7 hours ago, Plantguy said: I'm not up on my Paleozoic US geology but I seem to recall there were some substantial Paleozoic glaciation events that occurred causing incredible sea level changes in the Mississippian and Ordovician. I'm sure there was some tectonic things going on as well that may have thrown in some uplifts regionally/with plate movements and general climatic changes as well. Google Mississippian period and Ordovician period geology and youll get to read about how dynamic our planet has been during those periods and over the eons....its mind blowing the scale of change. The Smithsonian Magazine folks referenced a link that is pretty cool that allows you to key in your location on the planet and a time period and you can see the planet and where the continents are and see what parts are submerged during the given time period. Here's that article: https://www.smithsonianmag.com/smart-news/map-lets-you-plug-your-address-see-how-neighborhood-has-changed-over-past-750-million-years-180971507/ Here's the direct link to the interactive map of the globe/planet at dinosaurpictures.org https://dinosaurpictures.org/ancient-earth#0 Regards, Chris Ah that's good information. Thanks. I'm always curious. That could explains why for my area sandstone was 1st because of glaciations in the early Ordovician which seem to have less fossils associates with it, usually up in Canada. Then as glaciers melted the sea level rises and diversity explosive given rise to Platteville limestone which was in calmer tropical waters. Then something happened, maybe increase in rainfalls caused by gases from volcano eruptions that increases river runoffs rich in clay and silt created Decorah formation. That also explains why in parts of southern Minnesota parts of Decorah formation transition into galena formation which is limestone because it was further away from the volcanic arcs that arise in central Minnesota from plates activity by then. Interesting to know! 7 hours ago, Plantguy said: Awesome outcrops/rock photos! Looks like a great place to poke around in but be very very safe...outcrops with those types of faces/overhangs are/can be very unstable. Regards, Chris my area can be unsafe. One death in the past from a big block of harden shaly limestone overhang. I suspects the death of the children in that park was due to landslides created by sands - theres hundred of feet of sand overlying the rock formations that constantly erosions. I try to keep to the edges plus I had seen huge glacial boulders embedded in sand fall down when I was absent. Link to comment Share on other sites More sharing options...
ClearLake Posted May 16, 2021 Share Posted May 16, 2021 17 hours ago, Tetradium said: The only thing I dont understand myself is why was ordovician period so crazy. Sandstone then Limestone then Shale then Limestone again. Such wild variability in sea levels and sedimentary deposits. What changed? What cause so much clay/silt to washed into the sea for a period of time then sudden cut off, leaving behind lime. One thing you always have to keep in mind is time, a lot of it. The Ordovician period lasted for about 40 million years. That is plenty of time for multiple significant sea level changes, significant erosion or mountain building, etc. Just consider that during the most recent ice age sea levels rose and fell by several hundred feet multiple times in only a couple million year period. The “rapid” changes one often sees in the rock record may reflect long periods of no deposition or even erosion. One can spend a lifetime learning about what is going on in the rock record and only scratch the surface, it is indeed fascinating. 1 Link to comment Share on other sites More sharing options...
Plax Posted May 17, 2021 Share Posted May 17, 2021 Google "sequence stratigraphy". This subset of geology explains events like the changing rock types. 2 Link to comment Share on other sites More sharing options...
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