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Author Topic:   Mammals rebound
caffeine
Member (Idle past 393 days)
Posts: 1800
From: Prague, Czech Republic
Joined: 10-22-2008


(1)
Message 16 of 20 (865848)
11-01-2019 10:50 AM
Reply to: Message 12 by Faith
11-01-2019 8:01 AM


Re: Mammals not fossilized in the usual way?
So in this case instead of the bones getting fossilized by the replacement of bone material with a fossilizing mineral this mineral collected AROUND the bones instead and built up a rounded casing for them? So inside these concretions are unfossilized bones? Why the different process?
AbE watched it again. There's one point where they say the bones were ALSO fossilzed so I guess that answers my question. Why they also formed this ball of mineral within the rock is still a question though.
There was interesting research on this question recently too. Bunch of researchers from Japan argue that it's due to the release of calcium from bones interacting with clay of certain chemical compositions; and that these calcite concretions probably only take a few years to form.
Full article in Nature here (open access).
Summary in Forbes magazine here

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 Message 12 by Faith, posted 11-01-2019 8:01 AM Faith has replied

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RAZD
Member (Idle past 774 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 17 of 20 (865865)
11-01-2019 12:43 PM
Reply to: Message 16 by caffeine
11-01-2019 10:50 AM


Re: Mammals not fossilized in the usual way?
There was interesting research on this question recently too. Bunch of researchers from Japan argue that it's due to the release of calcium from bones interacting with clay of certain chemical compositions; and that these calcite concretions probably only take a few years to form.
Full article in Nature here (open access).
Interesting that the calcite concretions did not cover the shell of the Yatsuo tusk-shell.
I would think it was made from calcium carbonate. Presumably the calcium was already bonded as calcium carbonate and not free calcium from the bones?
Also, I note these are marine deposits, whereas I was under the impression that the mammal fossils were terrestrial. How would this process occur under terrestrial conditions?
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Coragyps
Member (Idle past 103 days)
Posts: 5553
From: Snyder, Texas, USA
Joined: 11-12-2002


(1)
Message 18 of 20 (865874)
11-01-2019 1:16 PM
Reply to: Message 17 by RAZD
11-01-2019 12:43 PM


Re: Mammals not fossilized in the usual way?
The paper that was posted posits that the carbonate in the concretions came from rotting organic matter in the critters that were buried, not from bones. The bones (or shells, etc.) would be left to fossilize by other means. And though the paper is on marine fossils, I can’t see any necessity for seawater in the process- any water with decent calcium content would work the same.
The concretions in my house’s water heater show that.
Edited by Coragyps, : No reason given.

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Faith 
Suspended Member (Idle past 813 days)
Posts: 35298
From: Nevada, USA
Joined: 10-06-2001


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Message 19 of 20 (865865)
11-01-2019 6:04 PM
Reply to: Message 16 by caffeine
11-01-2019 10:50 AM


Apatite not calcite
In the video that AZ posted the concretions were not calcite (or carbonate) but apatite.

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Coragyps
Member (Idle past 103 days)
Posts: 5553
From: Snyder, Texas, USA
Joined: 11-12-2002


Message 20 of 20 (865884)
11-01-2019 9:08 PM
Reply to: Message 19 by Faith
11-01-2019 6:04 PM


Re: Apatite not calcite
That’s different, and out of my limited expertise. Apparently it was a surprise to the researchers as well. But they did say that it was fossils inside the concretions - I claim ignorance of how calcium phosphate concretions form, unless it’s the apatite of bones dissolving and recrystallizing as the concretion. Weird.

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