Vnaz50 Posted December 21, 2020 Share Posted December 21, 2020 Vince San Antonio, Tx Unsure of this one. Luckily it stood up for. Good pic Link to comment Share on other sites More sharing options...
Mahnmut Posted December 21, 2020 Share Posted December 21, 2020 Hello Vince, What exactly is it that caught your eye on this one? The shape or the small "inclusions"? I do not know anything about the geology of San Antonio, but looking at the rocks you find I think you must have a karst region there. Most often this means limestone, so fossils are possible. The finer structures in your rocks may well be fossil invertebrate life. The overall shapes that look so bone-like are typical karst weathering. I know that combination from the mediterranean, where I lived as a kid. Finding a gastropod shell inside what looked like a strange femur is a giveaway, but finding a sponge there may make it look more bone-like on first and second look. I would try to find out from what time your limestone comes, it will most probably be marine. Then you know what to look for in fossils. Big vertebrates at least will be as rare as on any beach, even if they existed when your limestone formed. keep the eyes open for the little critters. Best Regards, J 3 Try to learn something about everything and everything about something Thomas Henry Huxley Link to comment Share on other sites More sharing options...
Vnaz50 Posted December 21, 2020 Author Share Posted December 21, 2020 3 hours ago, Mahnmut said: Hello Vince, What exactly is it that caught your eye on this one? The shape or the small "inclusions"? I do not know anything about the geology of San Antonio, but looking at the rocks you find I think you must have a karst region there. Most often this means limestone, so fossils are possible. The finer structures in your rocks may well be fossil invertebrate life. The overall shapes that look so bone-like are typical karst weathering. I know that combination from the mediterranean, where I lived as a kid. Finding a gastropod shell inside what looked like a strange femur is a giveaway, but finding a sponge there may make it look more bone-like on first and second look. I would try to find out from what time your limestone comes, it will most probably be marine. Then you know what to look for in fossils. Big vertebrates at least will be as rare as on any beach, even if they existed when your limestone formed. keep the eyes open for the little critters. Best Regards, J There are so many different consistencies in these items. I do know San Antonio was underwater at one point. So all of the small curved shells I have make sense. However the flat pieces like in the first pic, looks like hardened football leather after it’s cleaned and the edges are extremely sharp. Link to comment Share on other sites More sharing options...
digit Posted December 21, 2020 Share Posted December 21, 2020 4 minutes ago, Vnaz50 said: There are so many different consistencies in these items. I do know San Antonio was underwater at one point. So all of the small curved shells I have make sense. However the flat pieces like in the first pic, looks like hardened football leather after it’s cleaned and the edges are extremely sharp. Are you saying that you have found a number of 'consistent' rocks in your backyard? If so, this makes sense as they all look like pieces of sedimentary rock--likely limestone. I do not know the geology of Texas very well to know the formations but it appears you have uncovered a layer of associated limestone chunks. The mollusk shells you are finding are the first actual fossils that you've posted. They remind me of Gryphaea (aka 'Devils Toenails') but the Cretaceous mollusks of Texas are well beyond my normal comfort zone of fossil knowledge. I'll rely upon @JohnJ or others familiar with Texas invertebrates to make a better ID on those. Not sure what the possible resemblance to 'hardened football leather' indicates to you? They are sedimentary rocks (possibly containing marine fossils). They are not 'fossilized leather' if your thought process is taking you there. Sharp edges on a rock are usually an indication that the rock is dense and contains higher amounts of silica which causes sharper fractures. There is a reason that Native Americans sought out high-silica materials (cherts and the like) for fashioning stone points, knives and scrapers. High-silica stones tend to look glassy and can produce razor sharp edges. So 'leathery' surfaces and sharp edges may tell you something about the composition of the rocks you are finding but neither characteristic indicates anything about them being fossils. Cheers. -Ken 1 Link to comment Share on other sites More sharing options...
jpc Posted December 21, 2020 Share Posted December 21, 2020 I think your initial rock is indeed a chunk of limestone, as Mahnmut suggested. little curved shells are a Cretceous oyster called Gryphaea. (TX folks, feel free to correct me), and the longer snail looks modern, that is it died last month. 2 Link to comment Share on other sites More sharing options...
digit Posted December 21, 2020 Share Posted December 21, 2020 10 minutes ago, jpc said: and the longer snail looks modern, that is it died last month. Yes. The longer pearly white translucent one appears to be the shell of a modern tree snail. We have similar ones in Florida. Cheers. -Ken 2 Link to comment Share on other sites More sharing options...
Vnaz50 Posted December 21, 2020 Author Share Posted December 21, 2020 20 minutes ago, digit said: Are you saying that you have found a number of 'consistent' rocks in your backyard? If so, this makes sense as they all look like pieces of sedimentary rock--likely limestone. I do not know the geology of Texas very well to know the formations but it appears you have uncovered a layer of associated limestone chunks. The mollusk shells you are finding are the first actual fossils that you've posted. They remind me of Gryphaea (aka 'Devils Toenails') but the Cretaceous mollusks of Texas are well beyond my normal comfort zone of fossil knowledge. I'll rely upon @JohnJ or others familiar with Texas invertebrates to make a better ID on those. Not sure what the possible resemblance to 'hardened football leather' indicates to you? They are sedimentary rocks (possibly containing marine fossils). They are not 'fossilized leather' if your thought process is taking you there. Sharp edges on a rock are usually an indication that the rock is dense and contains higher amounts of silica which causes sharper fractures. There is a reason that Native Americans sought out high-silica materials (cherts and the like) for fashioning stone points, knives and scrapers. High-silica stones tend to look glassy and can produce razor sharp edges. So 'leathery' surfaces and sharp edges may tell you something about the composition of the rocks you are finding but neither characteristic indicates anything about them being fossils. Cheers. -Ken I understand that I only have a bunch of different types deposits but after brushing them, they come out to really odd shapes. Link to comment Share on other sites More sharing options...
digit Posted December 21, 2020 Share Posted December 21, 2020 The coloration does appear to be limestone which would make sense if you are finding some marine mollusk shells. It looks like some of that limestone is slowly picking up more silica (likely from silica rich sands) as the smooth surfaces and sharp edges are indicative of harder material that is more brittle and fractures with these clean surfaces. The rocks posted above do have a variety of shapes but none that I'd consider truly 'odd'. I guess when you've hunted for fossils in areas that are covered with rocks that look exactly like this they cease to become odd or interesting. To me they look like the shapes I'd expect of silicified limestone chunks. If they are pleasing to you then feel free to keep and display them. Most fossil collectors are also rock hounds and pleasing rocks that are not fossils often find their way into our collections. Just keep in mind that none of these show any signs of being fossils. Cheers. -Ken 2 Link to comment Share on other sites More sharing options...
Thomas.Dodson Posted December 21, 2020 Share Posted December 21, 2020 (edited) I'd say Ilymatogyra arietina over Gryphaea for the oysters. Determining a specific formation would help. This PDF has a generalized geological formation map of Texas to start with. There is a dot that says San Antonio but I'm not sure of the city boundary. http://custom.cengage.com/regional_geology.bak/data/Texas.pdf Edited December 21, 2020 by Thomas.Dodson Forgot to add link 5 Link to comment Share on other sites More sharing options...
digit Posted December 21, 2020 Share Posted December 21, 2020 Yup. Just looked up these 'Horn Oysters' and that seems a really good match. They are more curled to the side than the standard 'Devils toe'. http://homepage.physics.uiowa.edu/~cnewsom/fossils/Oysters/ilymatogyra/index.html Cheers. -Ken 1 Link to comment Share on other sites More sharing options...
Vnaz50 Posted December 21, 2020 Author Share Posted December 21, 2020 39 minutes ago, digit said: The coloration does appear to be limestone which would make sense if you are finding some marine mollusk shells. It looks like some of that limestone is slowly picking up more silica (likely from silica rich sands) as the smooth surfaces and sharp edges are indicative of harder material that is more brittle and fractures with these clean surfaces. The rocks posted above do have a variety of shapes but none that I'd consider truly 'odd'. I guess when you've hunted for fossils in areas that are covered with rocks that look exactly like this they cease to become odd or interesting. To me they look like the shapes I'd expect of silicified limestone chunks. If they are pleasing to you then feel free to keep and display them. Most fossil collectors are also rock hounds and pleasing rocks that are not fossils often find their way into our collections. Just keep in mind that none of these show any signs of being fossils. Cheers. -Ken The one on the far right is the same rock as my post on Link to comment Share on other sites More sharing options...
Vnaz50 Posted December 21, 2020 Author Share Posted December 21, 2020 Thank you for being so helpful and informative. You all have been great. Link to comment Share on other sites More sharing options...
digit Posted December 21, 2020 Share Posted December 21, 2020 We enjoy fossils and sharing our knowledge of them. Unlike most social media we're actually sociable. The suggestion that was made in one of your topics to join the Paleontological Society of Austin was a great idea. They are still holding virtual meetings but hopefully that will change sometime in 2021. No better place to learn about the local fossils than from a local fossil society. https://www.austinpaleo.org/ Cheers. -Ken 2 Link to comment Share on other sites More sharing options...
Mahnmut Posted December 21, 2020 Share Posted December 21, 2020 In my experience "karst" and "odd shapes" is nearly synonymous. Just ask the internet for "karst rock" and you will see. So probably almost any structure bigger than an oyster will be Karst shapes, although I can not rule out bigger fossils completely. J 2 Try to learn something about everything and everything about something Thomas Henry Huxley Link to comment Share on other sites More sharing options...
jpc Posted December 21, 2020 Share Posted December 21, 2020 1 hour ago, Vnaz50 said: I understand that I only have a bunch of different types deposits but after brushing them, they come out to really odd shapes. yup. lImestone will do that. 1 Link to comment Share on other sites More sharing options...
Vnaz50 Posted December 21, 2020 Author Share Posted December 21, 2020 2 hours ago, digit said: We enjoy fossils and sharing our knowledge of them. Unlike most social media we're actually sociable. The suggestion that was made in one of your topics to join the Paleontological Society of Austin was a great idea. They are still holding virtual meetings but hopefully that will change sometime in 2021. No better place to learn about the local fossils than from a local fossil society. https://www.austinpaleo.org/ Cheers. -Ken I have done that and will be in more communications with them. Thank you. 1 Link to comment Share on other sites More sharing options...
digit Posted December 21, 2020 Share Posted December 21, 2020 They should be an excellent source for great fossil information for your area. Cheers. -Ken Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now