Rudist collecting at Roemaskogel hill, Kainach, Styria, Austria (Geistthal-formation, Gosau-group of Kainach, upper Santonian - lower Campanian) - 07/10/2021

[FranzBernhard]

Hello,

several weeks ago, I presented a rudist recovery "operation" from the Afling-formation of the Gosau-group of Kainach (Upper Cretaceous):

 

Well, the same day I have discovered the rudist zone featured above, I have also discovered a rudist zone about 100-200 m stratigraphically deeper. It is confined to an about 1 m thick, very dark limestone bed rich in various rudist and echinoid remains. The limestone belongs to the Geistthal-formation, considering the limestone is still located within the sequence with some red clastic rocks, suggesting strong terrestrial influence in some layers. The limestone can be traced for at least 500 m along strike; at the footwall, it develops gradually from a conglomerate, in the hangingwall it is sharply overlain by fine-grained sandstone to siltstone. Here is a schematic map of the area, including also the Trochactaeon-bearing zone. In this post, I am dealing here with the "Liegende Rudisten-Zone". 59 = Geistthal-formation; 54 = Afling-formation, squares are 2x2 km.

 

The fossils stick firmly to the limestone. But there are some impure zones (sandy-silty) within the limestone, where, with the help of some weathering, some fossils largely free of matrix can be found. Two zones of this kind are known at the moment, a natural outcrop in the forest and an outcrop at a forest road, which will be presented here. Approaching the outcrop (well, that pic was taken after the dig...):

 

The outcrop was completely overgrown at the beginning, and this was the third day of working at this outcrop. You can see the worked area and the area prepared for today. The red x are markers placed above wooden marker sticks and about 1 m apart from each other. The soft zone between the hard limestone beds is visible. Sorry for the rather poor pics, my scrappy camera had a hard time dealing with that kind of lighting (clear sky and full shadow).

 

Detail of the area to be worked today, still with vegetation:

 

Vegetation cleared, first rudist found, a fragmentary Vaccinites, below the left red x. The pen is 13.7 cm long.

 

Work in progress, "two" Vaccinites discovered. Only after some time I recognized, that this is a bouquet:

 

Work practically finished, another Vaccinites discovered (4963). Turned out to be one of the nicest so far:

 

Beside these Vaccinites, a few Plagioptychus aguilloni were also found in that area.

But what to do with the rudist bouquet? Leaving in the outcrop or recover? I decided to recover, because it was already a little bit loose and already broken in several parts. And a one of a kind find until now. Here is the recovery, P.a. denotes a Plagioptychus aguilloni, numbers indicate individual Vaccinites specimens:

The recovery ended in 8 fragments. I numbered them to help reassembling them together. This bouquet appears to be in live position, but this can also be by pure chance. Maybe closer examination with give some hints.

 

That´s the outcrops after the work of this day, with the position of the specimens featured above indicated and before their recovery:

 

If you are interested in the other days at this outcrop, have a look at this:

05/22/2021 (link to my homepage, in German, pdf, ca. 2.9 MB)

05/30/2021 (link to my homepage, in German, pdf, ca. 5.8 MB)

 

From this few meters of outcrop, I have recovered ca. 10-15 Vaccinites, 5-10 Plagioptychus aguilloni and several radiolitid rudist until now. A great surprise was one large Trochactaeon snail intermixed with all the rudists (see link to 05/30/2021 above). I don´t take all fossils with me, about half of them I am leaving at the outcrop, so only approximate numbers. In the pavement of the forest road below the outcrop, I have also dug out about 15 Vaccinites specimens. Then there is the outcrop within the forest, which yielded also at least a dozen Vaccinites, still with a lot of potential. And all the other outcrops of the rudists limestone that I have not checked out in detail yet for loose rudists. Also still a lot of potential there and still a lot to do....

 

Hope, you enjoyed !
Franz Bernhard

Edited July 11, 2021 by FranzBernhard

[Kasia]

Wow, I'm always impressed with your systematic approach to fossil hunting and Swiss precision in identifying found specimen Really pretty stoney bouquet

[FossilDAWG]

Really an outstanding presentation! Are you planning for some kind of a research publication, or are you just always this meticulous about keeping records as you collect?

 

Don

[Fossildude19]

Thank you for this in depth report. 
This is the stuff that separates us from the rest of the internet! 
Thank you again, Franz!  Wonderful report!  

[FranzBernhard]

Thanks for your appreciation!

 

50 minutes ago, FossilDAWG said:

Are you planning for some kind of a research publication,

I have put together a short article (more like a summary) for a local collector´s journal. But I have notified scientists at the museum in Graz and the NHM in Vienna. All the info are also available on my homepage for other people to use. Maybe they could be useful in the future? Specimens will be donated to the museum in Graz after the short article is published.

 

51 minutes ago, FossilDAWG said:

are you just always this meticulous about keeping records as you collect?

It depends on the circumstances. If I collect from outcrop, as in this case, I try to document as good as I can. For example, orientation of specimens in relation to the dip direction of the strata. Mostly, however, I collect from rubble and float (or, my specialty, from the pavement of forest roads), so the exact geographic location, documented on a DEM (relief map) is enough. 

In the case of the Römaskogel rudist occurrences, nothing was known until 04/11/2021. Maybe some farmers noticed something during or after forest road construction (about 15 years ago), but all the sites in these two rudist zone appeared to be totally uncollected and were already quite overgrown.

 

Franz Bernhard

[Wrangellian]

Hey, those look like rudists! And rudist colonies!

The more you hunt the better you find... Nice presentation as always.