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Fossil hunting in the Geistthal-formation (Santonian - lower Campanian), Gosau basin of Kainach, Styria, Austria


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FranzBernhard

Fossil hunting in the Santonian - lower Campanian Geistthal-formation of the Gosau basin of Kainach, Eastern Alps (Styria, Austria)

 

As a whole, the Gosau basin of Kainach - St. Bartholomä is not very fossiliferous. In contrast to the St. Bartholomä-formation with its rudists etc., the other, much more extensive formations, especially the very extensive, somewhat tubititic Afling-formation, are generally very poor in fossils. Some are known, eg. ammonites, but their occurrences are rather elusive.

 

One exception - or at least in part - are Trochactaeon snails. They are known since the beginning of geological documentation of the area (around 1850), but only as loose pieces. It took until about the 1960ies for the first finds of this snails in outcrops. However, only a few sentences were (repeatedly) published since then, only a list of the species is given (without any description), and also no detailed description of the occurrences and their exact locations. That´s the sad side.

 

The good side is: There is at least one (permanent) occurrence of this snails in an outcrop at a major road! This occurrence is at the red X...

Geologie.thumb.jpg.856769e6e22e303cd370bb397b7d6531.jpg

Part of Geofast-map (left, squares are 2x2 km) and geological overview from Ebner (2000) (right). There seems to be not much correspondence between these maps. For orientation, see village Geistthal in upper part of both maps.

 

...and it is featured in an excursion guide from 2015 (from Hubmann & Gross, 2015):

Auszug_Hubmann_2015.thumb.jpg.6f5e88fc44daa7bfaaa0d9dbd58142d0.jpg

 

The snails are located in the upper part of the Geistthal-formation, a succession of gray conglomerates, sandstones and siltstones with very occasional thin coal layers and thin beds of calcareous onkoids. The lower part of the Geistthal-formation is a coarse-grained, red conglomerate; its the basal formation of the Gosau basin of Kainach.

 

I have visited this outcrop in December 2015, and yes, the snails are still there.

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FranzBernhard

How to find "new" Trochactaeon occurrences?

 

I decided to prospect the "Hasibach" south of Geistthal - the red line on the map in the previous post - at 04/09/2019. It turned out to be a very, very nice creek with some water, lots of loose stones and many outcrops. But sorry, no pics, I forgot my camera... :(.

 

Rocks were as expected: Grey conglomerates, sandstones, siltstones - loose in gravel bars and as alternating layers in various outcrops. I explored the creek for about 1 km. To make it short: Not a trace of a Trochactaeon was found.

 

But I didn´t came home totally empty handed: A specimen from a gravel bar, already split, contained an impression of a plant part. What could it be? It has some 3D-appearance to it. Is it more likely a seed than a leaf?

Pflanze_kompr.thumb.jpg.a61734d8e414990cafafe351d0fe587a.jpg

 

The second specimen is from an outcrop of a hard, dark grey siltstone. This rock does not break platy, but conchoidal, and looks, feels and behaves more like a basalt than a sedimentary rock. Several cracks run through the outcrop, the first piece I took (no tools necessary) contained this (upper specimen): Some small impression of bivalves, one of them rather complete (A). Unfortunately, it was dirty due to the preexisting crack. I took also the opposing part of this specimen with me and found another nice bivalve at home (B). The specimens contain more bivalve impression, but only incomplete ones. B looks like a tellinid bivalve, don´t know, what A could be.

Muscheln_kompr.thumb.jpg.36b17f2538ca21b1bae8a0726b049e51.jpg

 

In conclusion, a nice nature experience, no big snails, but still some fossils!

Thanks for looking!
Franz Bernhard

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Tidgy's Dad

Indeed.

Still some nice fossils.:)

Very interesting thread, thanks for sharing your experience and knowledge with us. 

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12 hours ago, FranzBernhard said:

 

Muscheln_kompr.thumb.jpg.36b17f2538ca21b1bae8a0726b049e51.jpg

 

:wub:

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I love your style of posting and way of doing your field work/research. Thanks for sharing :)

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Those are a couple of very pretty bivalves, Franz - congrats!  (even if you didn't find any new snail outcrops)

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FranzBernhard
On 10.4.2019 at 4:23 PM, Tidgy's Dad said:

thanks for sharing your experience and knowledge with us

You are welcome, and thanks for your appreciation.

 

19 hours ago, Peat Burns said:

:wub:

Can not believe someone likes them ;). Thanks!

 

13 hours ago, Al Tahan said:

I love your style of posting and way of doing your field work/research.

Thanks for your appreciation! Btw, I am waiting for your next rip report :D.

 

6 hours ago, Monica said:

Those are a couple of very pretty bivalves, Franz - congrats!  (even if you didn't find any new snail outcrops)

Oh, you like them also ;)! Thanks!

Maybe next time I will find a snail outcrop, maybe not - vast stretches of land (for Austrian standards) still to explore, so many small creeks and at least hundred kilometers of forest roads and small tracks, not to mention all the natural outcrops in the area.

 

Btw, what could the plant part be? Any hints? @Plantguy, @nala

 

Thanks you for all your interest and appreciation and help!

Franz Bernhard

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Nice fossils and I especially like the maps/geologic/site details included.  I dont recognize it and not well versed in plant frutifications so I'm not sure what that is. My first impression was a partial leaf folded upon itself with a petiole/stem and the midrib running along the top and veins radiating downward.  But it almost looks like there are very faint horizontal ribbing/lines where I've circled which might indicate that it is indeed some type of pod structure.  

5cb1f9c53c2f7_unknowncretaceousplantfragment.jpg.1555e852929df01502a2ecf94eb39c21.jpg

Kind of cool but I sure dont know. Maybe someone else recognizes it. @piranha @paleoflor

Regards, Chris 

Edited by Plantguy
left off photo---uggh!
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FranzBernhard

@Plantguy, thank you very much for your help and your opinion and also for your appreciation.

I have tried another pic of this fossil, with more oblique lightning. The somewhat 3D-appearance is now better visible. And it seems, that the fossil consists of two parts: To the right the larger part with three segments, to the left the smaller part with two segments (white line as separator):

Blatt_2_kompr.thumb.jpg.c9ab9f3e14e6705ac7fc50abeee9cb9a.jpg

On 13.4.2019 at 4:57 PM, Plantguy said:

faint horizontal ribbing/lines where I've circled

This area has a thin coating of calcium carbonate; I can not see any horizontal lines there. The closer I look at the specimen, the uglier it is... ;). Preservation is really, really poor, unfortunately.

Thanks again!
Franz Bernhard

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What a great closeup photo..I dont think its ugly at all! Maybe its just the impression of a partial leaf fragment but I'm not smart enough--maybe a paleobotanist seeing it and/or examining it in hand or one of the other members knows...

Thanks for the additional shot!

Regards, Chris  

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