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David in Japan

The mystery of the non-fossiliferous formation

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David in Japan

Hi TFF friends,

 

how are you?

 

I walked a little bit today to one of my favorite geological formation here in Japan called the Himenoura formation.

The himenoura formation is a late cretaceous (santonian) marine formation. It is divided in three levesl called the lower formation, the middle formation and upper formation (really surprising I guess) and the formation is made of mud stone from the bottom to the upper part of it.

 

Fossil hunter mainly search the lower formation because it is the richest part in fossils of this formation.

 

 The lower part is very rich in bivalves, ammonites and vertebrates fossils (sharks [13 species], sea turtles and bony fishes) .

The middle formation is less rich in fossils but you can still find some inoceramus, bivalves, few ammonites and some shark tooth ( 2 species).

the upper formation has no fossils.

 

I was wondering why the upper formation do not contain fossils.

What woud be the cause of this fossil rarefication? Does it mean that all life in this part of ocean gradually vanished or is there another explication?

Did evolutionnists lack time when they burried fossils in this formation?

 

 

Cheers,

 

David

 

 

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WhodamanHD

Environments change over time, the upper layers I assume had changed in environment, topography, water depth, and type of sediment. In Maryland we have a series of cyclical layers in something called the Purslane Formation, which represent the ocean coming in (sandstone, rarely has fossils) and it retreating and forming a river environment (fossiliferous shale).

likely there was one of these changes in this formation, someone more familiar may be able to tell you exactly.

Picture from the internet of the notable exposure of the Purslane, Sideling Hill 

3AEF55A0-442E-45BA-B653-BAC19330B217.jpeg

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digit

Very observant--and a good question.

 

I have no satisfactory answer for you other than to propose some possibilities. If the formations are a shale/mudstone then the original environment would have been (not surprisingly) mud. It is possible that the mud was being accumulated in the upper part of this formation in a way that was not suitable for (macroscopic) life. If this was an inhospitable environment then you would not expect there would be anything that could end up in the fossil record. Fossil preservation actually depends on conditions being just right to retain the remains of prehistoric life. There are so many sedimentary formations (the only type that can actually preserve fossils) out there but as fossil hunters we selectively focus on the ones with the perfect conditions that enable the fossils that we seek. I'm not a geologist (nor to I play one on TV :P) so I am only speaking from my limited knowledge. I'm sure a real geologist would be able to offer more detailed theories as to why a geological formation would run "dry" as it appears the Himenoura Group has done over its span with the fossils thinning out to complete absence at the top of the formation.

 

A quick internet search turned up this paper which may be of some use:

 

https://www.sciencedirect.com/science/article/pii/S0195667108000311

 

 

Cheers.

 

-Ken

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doushantuo

The Upper part of the Himenoura is terrestrial? Easiest explanation.

I think the Himenoura was simply part of a Cretaceous shallow fore-arc basin, but I am no expert on Japanaese geology.

Basin infilling/(more or less the disappearance of marine deposits) is generally thought to take place in less than 10 million years.

U/Pb average weighted age for acidic tuffs in the Himenoura seems to be between 84 and 81 My.

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David in Japan
6 hours ago, WhodamanHD said:

Environments change over time, the upper layers I assume had changed in environment, topography, water depth, and type of sediment. In Maryland we have a series of cyclical layers in something called the Purslane Formation, which represent the ocean coming in (sandstone, rarely has fossils) and it retreating and forming a river environment (fossiliferous shale).

likely there was one of these changes in this formation, someone more familiar may be able to tell you exactly.

Picture from the internet of the notable exposure of the Purslane, Sideling Hill 

3AEF55A0-442E-45BA-B653-BAC19330B217.jpeg

Nice formation! You can clearly see changes in this formation. Some similarities with the Mifune group formation here. Unfortunately, you cannot see such changes in the Himenoura formation that is why it was such a mystery for me.

 

6 hours ago, digit said:

Very observant--and a good question.

 

I have no satisfactory answer for you other than to propose some possibilities. If the formations are a shale/mudstone then the original environment would have been (not surprisingly) mud. It is possible that the mud was being accumulated in the upper part of this formation in a way that was not suitable for (macroscopic) life. If this was an inhospitable environment then you would not expect there would be anything that could end up in the fossil record. Fossil preservation actually depends on conditions being just right to retain the remains of prehistoric life. There are so many sedimentary formations (the only type that can actually preserve fossils) out there but as fossil hunters we selectively focus on the ones with the perfect conditions that enable the fossils that we seek. I'm not a geologist (nor to I play one on TV :P) so I am only speaking from my limited knowledge. I'm sure a real geologist would be able to offer more detailed theories as to why a geological formation would run "dry" as it appears the Himenoura Group has done over its span with the fossils thinning out to complete absence at the top of the formation.

 

A quick internet search turned up this paper which may be of some use:

 

https://www.sciencedirect.com/science/article/pii/S0195667108000311

 

 

Cheers.

 

-Ken

I am no geologist too and my knowledge is even more limited. Trying to fill my lack of knowledge everyday but it is just like trying to fill a bottomless hole.

When I thought about it, i had some hypothesis like the bad condition at the time for fossil conservation (could be related to environment chages), vanishing of all life (maybe the stupidest hypothesis) or environmental changes ( the one I prefered because you can see a progressive shift in fossil species).

But as I wasn't able to see any change in formation, for exemple a shift between shale to sandstone,  it was intriguing.

 

Thank you for the link, I've found this paper too, but I still need to find a way to download it.

 

 

6 hours ago, doushantuo said:

The Upper part of the Himenoura is terrestrial? Easiest explanation.

I think the Himenoura was simply part of a Cretaceous shallow fore-arc basin, but I am no expert on Japanaese geology.

Basin infilling/(more or less the disappearance of marine deposits) is generally thought to take place in less than 10 million years.

U/Pb average weighted age for acidic tuffs in the Himenoura seems to be between 84 and 81 My.

 

 

Thank you Doushantuo, It's been a while. Hope you're doing good.

Just another question about the terrestrial thing.

If the upper part was terrestrial, wasn't the shale supposed to turn red due to oxydation? 

 

 

thank you all for your answers.

 

 

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David in Japan

Ok, I managed to get the paper and read it. It is really answering to a lot of question I had and even further. Thank you very much.

 

I thought I know really well this formation, going so much time there but in fact I knew too little. It is very exciting, next time I will go there I will look at it more thoroughfully.

 

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