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Rudist hunting in St. Bartholomä, Styria, Austria - 13/07/2018


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FranzBernhard

Heavy rains in Styria, Austria, have overturned many creek beds. So this is a good time for fossil hunting, e.g. for rudists in St. Bartholomä:

View of the hunting area from Pleschkogel mountain (1063 m) toward St. Bartholomä with Kreuzegg and Kalchberg, distance about 8 km. Note the conspicuous church of St. Bartholomä, just below Kreuzegg. View is nearly southward, in the far background the Pohorje mountains in Slovenia. Photo taken 07/07/2018.

 

 

 

Uebersicht_07072018_Beschriftung.jpg

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FranzBernhard

Rudists are located in the St. Bartholomä Formation of the Gosau basin of Kainach - St. Bartholomä. The formation is to large on this map, it covers actually only about 3 km2.

 

 

Karte_Kainach_EbnerRantitsch_2000.jpg

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FranzBernhard

Areal distribution of the Upper Creataceous (Campanian) St. Bartholomä formation according to an actual geological map - yellow shading with blue waves. To the west is the unterlying Afling Formation (probably also Campanian), to the north are palaeozoic rocks, ligth blue are limnic-fluviatil miocene sediments.

 

Geologie_GeoFast.jpg

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FranzBernhard

Geographic map (www.amap.at) of the area, the St. Bartholomä Formation has a yellow shading. We will visit a small creek west of the "K" of "Kalchberg".

MapWithGeology_StBartholomae.jpg

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FranzBernhard

Topographic relief of a part of the area (ALS, lidar, from www.gis.steiermark.at). For orientation, you can use the road in the northwestern corner. The arrow points to the creek that will be hunted...

About 10 quarries are visible on this relief. From ca. 1880 to 1927, hydraulic marl was mined in the St. Bartholomä Formation. In open quarrys, but mostly in unterground workings extending from the quarries. Only a few layers of the marl to marly limestone, the major rock of this formation, were suitable for portland cement fabrication, so these layers were followed underground.

Calcareous sandstone was also mined in some quarries, eg. for building the church of St. Bartholomä.

Relief.jpg

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FranzBernhard

View from above of the middle part of the creek. Difficult ligthing conditions and a bad camera results in so-so photos... Sorry!

 

13072018_Uebersicht_kompr.jpg

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FranzBernhard

In situ-photo of the first rudist of this hunt, just as lying in the gravel (right of the pocke knife).

20_Mittel_kompr.jpg

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FranzBernhard

Detailed in-situ photo of this rudist.

20_Detail_kompr.jpg

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FranzBernhard

Overturned and cleaned. Adpical view, the pillars are already visible. At ca. 00:30 the P1-pillar, at about 10:00 the P2-pillar. Already indentified as Hippurites nabresinensis in the field. Diameter ca. 6 cm.

20_vonoben_kompr.jpg

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FranzBernhard

Same specimen, cut and polished. It turned out quite nice! Apical view, P1 at ca. 3:00, P2 at ca. 5:00. This species has no L-pillar, it would be at 00:00. However, the position of both teeths sockets (at about 11:00 and 1:00 and the position of the posteriore muscle at about 2:00 are visible (compare with the specimen in collections). Greatest diabmeter 67 mm.

AN_HippuritesNabresinensis_AN4040_Breite60mm.jpg

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FranzBernhard

Next rudist, just a few meters away, in the gravel at the lower right corner.

20_b_Uebersicht_kompr.jpg

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FranzBernhard

Here it is, in situ, a nice, small radiolitid rudist with coarse rips.

20_b_Detail_kompr.jpg

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FranzBernhard

View of the creek with gravel bars. One rudist fragment was found on the surface of this bar. No digging during this hunt, just surface collecting.

20c_Uebersicht_kompr.jpg

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FranzBernhard

Next rudist, at the upper end of the already dry creek. Can you spot it? Its just below the middle of the photo.

Oben_Uebersicht_kompr.jpg

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FranzBernhard

Rudist in-situ and in detail. It turned out to be Vaccinites vesiculosus. It is crushed on one side, but after cleaning at home, pillars were already visible.

Oben_Detail_kompr.jpg

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FranzBernhard

Have you noticed the trash in some of the photos? Here is more! Farmes have dumped their trash in creeks before there was organized trash collecting. But - there is also a rudist, just left of the pocket knife!

Ganzoben_Uebersicht_kompr.jpg

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FranzBernhard

Here it is, in-situ. Not much to see, only some folded rips, its a radiolitid rudist.

Thats the end of the creek and the end of the finds of this day, a total of four rudists. Hope you have enjoyed the trip to an obscure area, despite the rather poor photos.

 

Btw, the rudists are coming from the "Knödelbrekzie", a coarse conglomerate or breccia composed only of clast of fossiliferous limestone, intercalated beween the marls, and about 1-2 m thick (second photo). Some of the clasts contain rudists, but not very many. The rudists weather out, are a little bit transported and can then be found in the creeks,  on fields or just at the surface in the forests. But also in-situ directly within the "Knödelbrekzie", but very rarely. Third photo shows a Vaccinites vesiculosus in-situ within the exposed "Knödelbrekzie" in one of the old quarries in St. Bartholomä. Its the lying, cracked cylinder in the middle of the photo, below the "Knödelbrekzie" marl and calcareous sandstone is exposed.

 

Thanks for watching!

Ganzoben_Detail_kompr.jpg

25_Knoedelbrekzie_16072017_konpr.jpg

25_KnoedelbrekzieüberMergel_16072017_kompr.jpg

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Nice report (and finds), thanks for sharing.

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Thanks for this very informative post.

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Very interesting post, especially because I recently received my very first rudist pieces care of Sophie @fifbrindacier :)

 

I was just wondering what the "pillars" are?  Are they specialized structures that are thought to have performed particular functions when the rudist was alive?  And do they differ between rudist species?

 

Thanks!

Monica

 

PS - The cut and polished specimen is beautiful! :wub:

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fifbrindacier

Thank you for your post. You seem to know a lot about rudists.

I have some i collected in my collection : Diceras arietinum, a maybe Radiolitid, Polyconites (or so i think), Ichtyosarcolites triangularis, Sphaerulites foliaceus.

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FranzBernhard
10 hours ago, ynot said:

Nice report (and finds), thanks for sharing.

 

8 hours ago, Ludwigia said:

Thanks for this very informative post.

 

8 hours ago, Monica said:

Very interesting post

 

7 hours ago, fifbrindacier said:

Thank you for your post.

Thanks for your interest!

 

8 hours ago, Monica said:

I was just wondering what the "pillars" are?  Are they specialized structures that are thought to have performed particular functions when the rudist was alive?  And do they differ between rudist species?

The L-pillar is the place for the infolded ligament, which is lost in most species and even the pillar itself is lost in some species. The other pillars may have do to something with water circulation, but I am not sure.

Attached is a rather old paper from an authority with some nice figures (3.4 MB).

Yes, there are very large differences, and the pillars are the main feature to distinguish the different species (several hundred) within the family Hippuritidae. Another important feature is the structure of the flat upper valve, but this is rarely preserved.

Here you can see the five(?) different Hippuritid species from St. Bartholomä I have encountered so far:

https://franzbernhard.lima-city.de/Hippurites.html

https://franzbernhard.lima-city.de/Vaccinites.html

https://franzbernhard.lima-city.de/Hippuritidae_2018.html

 

8 hours ago, Monica said:

The cut and polished specimen is beautiful!

I like it, too. Nice contrast and warm color. Thanks!

 

8 hours ago, fifbrindacier said:

I have some i collected in my collection : Diceras arietinum, a maybe Radiolitid, Polyconites (or so i think), Ichtyosarcolites triangularis, Sphaerulites foliaceus.

Nice collection, but I don´t see a Hippuritid ;). Are you hunting in an older formation than Campanian?

 

Franz Bernhard

 

 

 

Rudisten_Skelton_1976.pdf

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fifbrindacier
10 hours ago, FranzBernhard said:

 

 

 

Thanks for your interest!

 

The L-pillar is the place for the infolded ligament, which is lost in most species and even the pillar itself is lost in some species. The other pillars may have do to something with water circulation, but I am not sure.

Attached is a rather old paper from an authority with some nice figures (3.4 MB).

Yes, there are very large differences, and the pillars are the main feature to distinguish the different species (several hundred) within the family Hippuritidae. Another important feature is the structure of the flat upper valve, but this is rarely preserved.

Here you can see the five(?) different Hippuritid species from St. Bartholomä I have encountered so far:

https://franzbernhard.lima-city.de/Hippurites.html

https://franzbernhard.lima-city.de/Vaccinites.html

https://franzbernhard.lima-city.de/Hippuritidae_2018.html

 

I like it, too. Nice contrast and warm color. Thanks!

 

Nice collection, but I don´t see a Hippuritid ;). Are you hunting in an older formation than Campanian?

 

Franz Bernhard

 

 

 

Rudisten_Skelton_1976.pdf

I got most of them in a cenomanian formation where you also can find Hippurites. And the Diceras and the Radiolitid in a Kimmeridgian formation.

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On 7/16/2018 at 9:49 AM, FranzBernhard said:

 

AN_HippuritesNabresinensis_AN4040_Breite60mm.jpg

:wub::envy:

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