karstic Posted August 14, 2022 Share Posted August 14, 2022 (edited) An acquaintance of mine found this material in a river bed here in Dane County, Wisconsin. Most of the locality bedrock is Ordovician or Cambrian limestone, sandstone or dolomite. This area is also glaciated, although you don't see a lot of till or erratics right around here. Any suggestions what this might be? It was initially suspected as fossilized wood, although that seems unlikely. Edited August 14, 2022 by karstic Link to comment Share on other sites More sharing options...
FranzBernhard Posted August 14, 2022 Share Posted August 14, 2022 Welcome to TFF from Austria! Is this rock greenish or green? If so, it could be greenschist or serpentinite with slickensides (link to wikipedia), very vaguely mimicking macro wood texture. Franz Bernhard 1 2 Link to comment Share on other sites More sharing options...
Rockwood Posted August 14, 2022 Share Posted August 14, 2022 It does look like the structure seen in slickensides. Link to comment Share on other sites More sharing options...
Mark Kmiecik Posted August 14, 2022 Share Posted August 14, 2022 1 hour ago, Rockwood said: It does look like the structure seen in slickensides. It may be glacial striation. The area has experienced glaciation after all. Mark. Fossil hunting is easy -- they don't run away when you shoot at them! Link to comment Share on other sites More sharing options...
Rockwood Posted August 14, 2022 Share Posted August 14, 2022 1 minute ago, Mark Kmiecik said: It may be glacial striation. The area has experienced glaciation after all. With as many layers as this ? Link to comment Share on other sites More sharing options...
Mark Kmiecik Posted August 14, 2022 Share Posted August 14, 2022 Just now, Rockwood said: With as many layers as this ? Nope. You're right. Not likely. That first photo also whacks my hypothesis. Mark. Fossil hunting is easy -- they don't run away when you shoot at them! Link to comment Share on other sites More sharing options...
karstic Posted August 14, 2022 Author Share Posted August 14, 2022 (edited) 9 hours ago, FranzBernhard said: Welcome to TFF from Austria! Is this rock greenish or green? If so, it could be greenschist or serpentinite with slickensides (link to wikipedia), very vaguely mimicking macro wood texture. Franz Bernhard Thanks very much. This rock is tan or grey in color. The green in the second and third photos is algae from the river. Thanks for that link. I was unfamiliar with slickenslides. That explanation, however, seems unlikely. You don't see much evidence of metamorphosis, orogeny etc. in the rocks here. I think it is most likely some kind of sedimentary rock feature or marine fossil. Given the location, a man-made building material or industrial waste my also be possible. Edited August 14, 2022 by karstic 1 Link to comment Share on other sites More sharing options...
Rockwood Posted August 14, 2022 Share Posted August 14, 2022 9 hours ago, karstic said: This area is also glaciated, You can't really rule it out on a 'supposed to be there' then. Link to comment Share on other sites More sharing options...
karstic Posted August 14, 2022 Author Share Posted August 14, 2022 (edited) Well it looks like slickenslides might be a possibility in the bedrock right around here and areas nearby. Apparently their formation doesn't necessarily require such active or deep conditions and they can form right in Silurian dolomite. See page 5... https://wgnhs.wisc.edu/pubshare/GS12.pdf County bedrock map... https://wgnhs.wisc.edu/catalog/publication/000913/resource/wofr201301plate01 Edited August 14, 2022 by karstic Link to comment Share on other sites More sharing options...
FranzBernhard Posted August 15, 2022 Share Posted August 15, 2022 11 hours ago, karstic said: sedimentary rock feature Ok, its not green, so more probably a sedimentary rock. Limestone or sandstone? If limestone, stylolites (link to wikipedia) are also a possibility. Franz Bernhard Link to comment Share on other sites More sharing options...
karstic Posted August 15, 2022 Author Share Posted August 15, 2022 3 hours ago, FranzBernhard said: Ok, its not green, so more probably a sedimentary rock. Limestone or sandstone? If limestone, stylolites (link to wikipedia) are also a possibility. Franz Bernhard It seems like it's most likely slilckenslides. Slickenslides is is described for dolomite bedrock not very far from this area and the photographs look just like it. Link to comment Share on other sites More sharing options...
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