Tr0xy Posted June 18, 2022 Share Posted June 18, 2022 (edited) Hello. I found this fossil matrix in my teens in an area of Northern California that's part of the Chico Formation. The surrounding sea shell fossils were in a layer of hard dark grey shale in a cliff face. I found this loose piece halfway down the hill up against a tree. I was told at the time that it's a concretion. I've never seen a concretion in person but they always look almost spherical in photos online. It weighs 5lb or 2.26kg Shaped like a sectioned log. layer of fossils running horizontal throughout what I've decided is the bottom. Sediment layers in various colors are ring shape above fossil layer, stay consistent from one flat end to the other. Any thoughts on if this was formed as a concretion and maybe how it got its shape? Thanks for looking! Edited June 18, 2022 by Tr0xy Link to comment Share on other sites More sharing options...
Lone Hunter Posted June 19, 2022 Share Posted June 19, 2022 Kinda looks like a large infilled burrow? 1 1 Link to comment Share on other sites More sharing options...
Tr0xy Posted June 19, 2022 Author Share Posted June 19, 2022 1 hour ago, Lone Hunter said: Kinda looks like a large infilled burrow? That's an interesting idea. The Chico Formation is, I think 85 million year old ocean floor. So maybe something burrowed above the layer of marine fossils layer and sediment infilled it? The cliff face I mentioned was eroded by a creek so there has probably always been water there even after it was no longer ocean floor. Link to comment Share on other sites More sharing options...
Lone Hunter Posted June 19, 2022 Share Posted June 19, 2022 I could be wrong but I would think the fossils were in sediment that filled it in, hopefully someone more knowledgeable will chime in. Link to comment Share on other sites More sharing options...
Plantguy Posted June 19, 2022 Share Posted June 19, 2022 I dont believe its a burrow. I believe you just have a section of the concretion---like having the middle section of a loaf of bread where the ends have been removed/cut off. Occasionally they just fracture and you can find them in place--you can remove them out of the shale in multiple individual pieces/sections just like what you have or they erode out of the bank and tumble down the slope. Some are more round but many are elongated and egg shaped... Cool find!....Excellent place to go back and revisit look for the other sections and other concretions....Not sure what the current permissions are needed/collecting laws are now. If one concretion is fossiliferous thats a very good sign that there will be others. Since you are dealing with Mesozoic sediments....all kinds of dinosaur aged critters could be within... Regards, Chris 2 Link to comment Share on other sites More sharing options...
RJB Posted June 19, 2022 Share Posted June 19, 2022 Ive always thought of concretions as round, or somewhat round. I would call this concreted material. I could be wrong. I was calling Aturia Arturia for over 20 years. Anyways, maybe try splitting it along that shell line? Good luck RB 1 Link to comment Share on other sites More sharing options...
FossilDAWG Posted June 19, 2022 Share Posted June 19, 2022 Concretions can often form around burrows, and so be quite elongated. Also shell material may be deposited in the floor of burrows such as crab burrows. The object in question is certainly a piece of an elongated concretion. 1 Link to comment Share on other sites More sharing options...
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