OSLO Posted September 18 Share Posted September 18 Hi all, I found this in far northern Minnesota near a river. The circle is on both sides of the 2" thick rock, so I am assuming that a cylinder extends through it. After looking at images online, I am thinking that it might be a fossilized tubeworm, but none of the photos that I've seen quite match. Northern Minnesota has obviously had a lot of glacial activity in the past (possibly Blackduck Formation in the location found), and this area has Neoarchean bedrock. Thank you for any information that you can provide! Link to post Share on other sites
Tidgy's Dad Posted September 18 Share Posted September 18 Section of a rugose coral, perhaps? Link to post Share on other sites
Ludwigia Posted September 18 Share Posted September 18 It would help if you were able to remove the object from the matrix in order to study the sides. Link to post Share on other sites
DPS Ammonite Posted September 18 Share Posted September 18 Structure is too fine to be coral with septa. Looks similar to a needle-like growth of mineral such as calcite grown in open space. Put some acid on it to see if it fizzes. Notice concentric growth rings. The center looks like it was hollow once. I wonder if this is not a stalagmite/cave formation that was broken off and incorporated into another rock. Link to post Share on other sites
FossilDAWG Posted September 18 Share Posted September 18 This very much reminds me of a section through the siphuncle of a nautiloid such as Narthecoceras. If that is correct it would be Upper Ordovician in age. Don 2 Link to post Share on other sites
DPS Ammonite Posted September 18 Share Posted September 18 24 minutes ago, FossilDAWG said: This very much reminds me of a section through the siphuncle of a nautiloid such as Narthecoceras. If that is correct it would be Upper Ordovician in age. Don That could be too. They are both a layered structure grown from calcite that show growth rings. Link to post Share on other sites
FossilDAWG Posted September 18 Share Posted September 18 Note the cross section in the top center: Image source: Robert C. Frey 1981. Narthecoceras (Cephalopoda) from the Upper Ordovician (Richmondian) of Southwest Ohio. Journal of Paleontology , Nov., 1981, Vol. 55, No. 6 (Nov., 1981), pp. 1217-1224 4 Link to post Share on other sites
OSLO Posted September 18 Author Share Posted September 18 On 9/18/2023 at 3:49 PM, FossilDAWG said: Note the cross section in the top center: Image source: Robert C. Frey 1981. Narthecoceras (Cephalopoda) from the Upper Ordovician (Richmondian) of Southwest Ohio. Journal of Paleontology , Nov., 1981, Vol. 55, No. 6 (Nov., 1981), pp. 1217-1224 Wow, that appears to be it! Looks like Narthecoceras fossils have been found in Manitoba too--so not too far away. Thank you! Link to post Share on other sites
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