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Jurassic Slate, Tuolumne County, California


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Richard Beale

I've been living in Chinese Camp, California for five years.  I wouldn't have moved here except that I took my wife and two children looking for ammonite fossils.  We found none that day, but we ended seeing an old country store for sale (only business in the abandoned town) and eventually bought it and live on the property.

The fossils around here are all late Jurassic, but because of the forces that created the Sierra Nevada mountains, the fossils are very rare and in poor shape.  Finding a whole ammonite, no matter small is a cause for great celebration, but this doesn't dampen my enjoyment at all.  For several years we found some ammonites and a few Buccia (Jurassic brachiopod) but on rare occasions we found something long and tapered.  I founds parts of these and they were segmented so I suspected  belemnites.  They are never (never ever) found alongside (in the same layers) ammonites, but they are in the same general formation (Mariposa Formation).  Here are the fist ones I found, when I wasn't too sure what they were:

belemnite 3.jpg

belemnite 5.jpg

belemnite 6.jpg

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Richard Beale

Continue from above.  I wasn't too sure of what I was finding with the above fossils, but my wife and I found these last two recently and now I am sure they are belemnites.

One shoes a phragmacone clearly with the faint outline of the rostrum.  The other shows both the side view and then the cross section  (one belemnite broken to show both views, or parts of two different belemnites).

I believe these are the same types of fossils as the long tapered fossils shown above, but these last two are a lot shorter and not so thin, so I might have two different types of fossils.  Now, every Monday before work, my wife and I go out every Monday to a creek 7 miles from home and look for fossils (I look for fossils, she looks for Mariposite, a green mica,  and anything else pretty).

I hope to find enough fossils to write a mini paper on the topic.  Some of the belemnites (if that's what the thin types are) look to have rostrums up to 30cm or more which makes them unusual.  It is nice to have a mystery to solve.  I you are going to be in Tuolumne County (Location of Yosemite) on a weekend, you are welcome to stop by and I can show you (or draw a map if pressed for time) to places to look for Jurassic fossils.

 

Richard

belemnite 4.jpg

belemnite 2.jpg

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Ludwigia

You are correct in your assumption. You definitely do have belemnites there. Good luck on your research on them. Perhaps @TqB might be interested in your discovery.

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Posted (edited)

They're interesting, especially the long thin ones. A 30+cm rostrum would be exceptional for a late Jurassic belemnite (from Europe anyway!). Cylindroteuthids can have the right proportions but 25cm or so is the maximum. The largest belemnites known are Middle Jurassic Megateuthis but I don't think they made it past then.

Edited by TqB
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Richard Beale

Ludwgia, TqB, Thanks for your very informed replies.  I will keep collecting these until I can say something with justified confidence.  The long, very thing fossils may well be something different than the few more-obvious-looking belemnites.  I have found broken examples of the long tapered type that make me think that whole, they exceed 30 cm, but it would (of course) be nice to find a complete and well-preserved one.

Richard

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Posted (edited)
On 5/21/2022 at 12:39 AM, Richard Beale said:

I

 

belemnite 5.jpg

 

@Richard Beale I look forward to seeing more! Do you have a higher resolution shot of this one?

Edited by TqB
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