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At least I found a nice bivalve


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A friend of mine told me last week that they'd started construction on a bypass around a small town in the Wutach area in the fall. They won't be really going at it until the springtime, but he visited the site last week and managed to find a couple of nice Hettangian ammonites on the scree pile, which was free of snow, since the temps are rising at the moment. So, since I was suffering from cabin fever, I figured I'd get out for some fresh air and give it a go. Well, there was lots of evidence of ammonites with a number of large body chamber pieces lying around, but it was obvious after a couple of hours of investigation, also directly at the exposure, that I had arrived quite a bit later than all the local collectors. I did however manage to find a well-preserved Plagiostoma gigantea, or giganteum (depending on which author you prefer) bivalve, which saved the day. I'll have to keep an eye on this site when they start working again anyway. Actually, it was just nice to get out a do some rummaging around.

 

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That is a nice one, too bad about the lack of good ammonites.

Glad You could get out.

Tony

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That is a beautiful bivalve Roger. I am not familiar with this species, is it from the Jurassic? 

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Peace river rat
Just now, Peace river rat said:

Even a bad day fossil hunting, beats a lot of other, good days!

That's a cool find, also.

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Thanks for your sympathy, guys. I sure would have liked to have found a good Schlotheimia ammonite, but at least this bivalve is worth its salt.

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Peace river rat
2 minutes ago, Ludwigia said:

Thanks for your sympathy, guys. I sure would have liked to have found a good Schlotheimia ammonite, but at least this bivalve is worth its salt.

Here in the Peace river, in Fl. I find fossils, but very few bivalves, the only ones I have found are inside cast.

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17 minutes ago, sixgill pete said:

That is a beautiful bivalve Roger. I am not familiar with this species, is it from the Jurassic? 

Yup. Hettangian is the earliest of early Jurassic. This genus occured from the mid triassic up to the late cretaceous and is extremely variable in form and sculpture.

 

9 minutes ago, Coco said:

Hi,

 

Plagiostoma ?

 

Coco

Oui. This species is very abundant in a particular horizon. It ranges from here up to Great Britain.

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1 minute ago, Peace river rat said:

Here in the Peace river, in Fl. I find fossils, but very few bivalves, the only ones I have found are inside cast.

It sure is nice to find them with the shell still intact.

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Peace river rat
7 minutes ago, Ludwigia said:

It sure is nice to find them with the shell still intact.

And kinda rare!

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3 minutes ago, Peace river rat said:

And kinda rare!

Actually over here not so. At least in most Jurassic layers the shells on a lot of bivalves are better preserved than the ammonites since they are mostly thicker and were originally calcite whereas most ammonites were aragonitic, which needed to be converted.

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I'll take back my last statement about calcite vs. aragonite. I was just stating something I thought I had read somewhere, but it got me thinking, so I did a bit of research and noticed pretty quickly that it's not as simple as that. Apparently almost all molluscs originally developed aragonitic shells, which, although less stable than calcite, provided better protection from predators since it is harder. Some combine both polymorphs with aragonite inside and calcite outside, since it doesn't dissolve as readily as the latter and apparently magnesium plays a role here as well. My observations in the field have however indicated to me that at least in the Jurassic layers I am familiar with it is often the case that in any given layer, bivalves and brachiopod shells are as a whole much better and more often preserved than those of the ammonites.

I do know that at over some stretch in geological history, the aragonite was converted in most cases to the more stable calcite. Perhaps bivalves and brachiopods had thicker shells or a different shell structure to those of the ammonites, which in turn were more susceptible to dissolution before they could be completely converted? It sure would interest me if anyone else could educate me on this subject.

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Glad to hear you got out, Roger. A good bivalve fossil can be a trip maker for me. Luv the preservation of that one. Thanks for the information about mollusk preservation. Most cephalopod fossils I find in the Devonian of New York are crushed which I was told was because of the aragonite composition not holding up as well as calcite when the shell was buried. Of course there are exceptions.

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Great find !

I have many smaller ones from the " Arietenkalk" in the area of Balingen and also some form Frick ...

But this is a huge one ! Congrats :D

 

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7 hours ago, Jeffrey P said:

Glad to hear you got out, Roger. A good bivalve fossil can be a trip maker for me. Luv the preservation of that one. Thanks for the information about mollusk preservation. Most cephalopod fossils I find in the Devonian of New York are crushed which I was told was because of the aragonite composition not holding up as well as calcite when the shell was buried. Of course there are exceptions.

 

It's an interesting subject. Maybe I'll open up a new thread on it for discussion.

 

1 hour ago, belemniten said:

Great find !

I have many smaller ones from the " Arietenkalk" in the area of Balingen and also some form Frick ...

But this is a huge one ! Congrats :D

 

 

This layer is somewhat older and lies in a hard red clay-limestone bank underneath the zone with Schlotheimia. Lias alpha 2.

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@Ludwigia

 

That's a nice bivalve for sure Roger. Clearly not what I expected when starting to read the report, knowing the usual fare you provide us.

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18 minutes ago, Ptychodus04 said:

@Ludwigia

 

That's a nice bivalve for sure Roger. Clearly not what I expected when starting to read the report, knowing the usual fare you provide us.

 

Thanks Kris. It's also not what I was expecting to find when I set off to visit this site.

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2 hours ago, Ludwigia said:

 

Thanks Kris. It's also not what I was expecting to find when I set off to visit this site.

 

We will let it go this time, but don't let it happen again or there will be consequences.:P

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19 hours ago, Ptychodus04 said:

 

We will let it go this time, but don't let it happen again or there will be consequences.:P

Uhoh B)

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  • 3 weeks later...

On my way up to the Callovian site in the Wutach yesterday I decided to stop into the construction site again. This time I discovered a scree pile which I hadn't noticed before due to the foggy weather at the time. It was obviously already picked through by a horde of collectors before me, so ammonites were no go. But at least I found another nice Plagiostoma gigantea, this time 13cm. long. Hard to believe sometimes that these shells are 200 million years old.

 

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L317c.2.thumb.jpg.3476cd50ec4f22ca12994e1e91228923.jpg

 

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Beautiful bivalve fossil.  Thanks for posting it.

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I sure do like these guys. It's amazing how well preserved they are.

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That is a nice clam!

Too bad You only collect ammonites-- You should send it to Me so it will have a good home!

 

Tony

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Wow..those are nice! And huge!

Do you have a lot of competition over there?

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