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Showing results for tags 'geisingen'.
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Most of the shell on this specimen is intact. Phragmocone.
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The subgenus Ludwigella is a collective term for what are believed to be microconches for the genus Graphoceras.
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Calcite mold of the phragmocone.
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Calcite mold. This extremely variable species was newly erected in 2014 by Dietze etal. Literature: V.Dietze etal, Aalenian (Middle Jurassic) ammonites and stratigraphy of the Geisingen clay pit (SW Germany), Palaeodiversity 7: 61–127; Stuttgart 30 December 2014.
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Calcite mold showing the suture lines of the phragmocone.
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Calcite mold. Phragmocone and a small part of the body chamber.
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Limestone mold. Index fossil for the polygratus subzone.
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Aptychi mostly existed as bilaterally symmetrical pairs and were part of the anatomy of many ammonites. They are believed to have been either a two-valved closing hatch at the aperture or else a double-plate jaw piece. This particular one is associated with the ammonite genus Taramelliceras.
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I had a bit of time on hand on Sunday; actually the whole day. I felt like getting out, but I didn't particularly feel like doing a lot of hammering, prying and clambering about, so I decided to head out to the fields, since this is the time when the farmers plow up a lot of them. I've discovered a "collection" of fields over a few years of sleuthing around the Geisingen and Blumberg areas, so I figured I'd do the tour again. The only thing which is a little strenuous about this kind of activity is bending over and standing up again. Crisscrossing fields in a grid pattern can get a bit boring too by the end of the day, but the air is fresh, the birds are singing and the cats are on the prowl. I covered 8 fields over a stretch of about 7 hours - they lay quite far apart and I have to drive from one to the next - and 5 of them had a few things worth taking. The thing about field finds is that a lot of the fossils laying there are pretty weathered, so a lot gets left behind, but there are almost always a few thing which could do with a closer look in the workshop. Here's what I took home with me. The ones in the first 2 crates come from a pile of blocks which were stacked at the edge of a field near Geisingen. They had obviously been recently cleared off by the farmer. I whacked open a lot of them, thereby discovering some ammonites within a few, as illustrated in the second photo. The stone is pretty hard, lots to remove, and there's some puzzle work to do, so I'll probably save these until last. I'm not even sure if they'll survive the treatment. I started rummaging through the finds today and decided to begin with the ones at the bottom right, since the matrix is relatively soft and easier to work. I chose the one in 2 pieces where you can see the chambers to begin with. First I removed the matrix from the smaller piece and then glued the two pieces together Then I worked a bit more with the air pen, decided to remove the rest of the matrix surrounding the fossil and had a go at it with the air abrader in order to see what shape the shell was in. So far so good...the rest of the work was done rocking back and forth between pen and abrader. I find it's pretty good for a field find, although I still have a few gaps to fill in with stone meal. I'm also not sure about the species, but I'll figure that out later. I'll post this again once it's finished and also the others as I get them done.
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Well preserved shell on one side; up to the end of the phragmocone on the other.
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Found on a plowed field. Calcite mold of part of the phragmocone.
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Found on a plowed field. The shell on the phragmocone is preserved. Index fossil for the romani subzone.
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This microconch is the index fossil for the perayense horizon. The lappet is clearly visible on the limestone mold.
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This is just part of the phragmocone, so it would have been quite large in real life.
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Not the best specimen due to the missing section of whorl, but still the best I have.
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Partially calcified limestone mold. Mostly phragmocone with a bit of body chamber.
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Bigotites (Prorsisphinctes) pseudomartinsi (Siemiradszki 1899)
Ludwigia posted a fossil in Ammonoids
This specimen was found on a plowed field. It is practically complete with well-preserved shell. A small portion of the venter on the outer whorl between 1 & 3 o'clock was missing and was restored with modelling clay and touched up with water colors. Tube worms and oysters settle on the inner whorls of the reverse side, probably after death and deposition, which indicates which side was up on the ocean floor. -
Limestone mold. with most of the body chamber preserved.
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This specimen has retained most of the shell on the body chamber and is practically complete, with the exception of the small missing section of whorl which I replaced with stone meal. This was left intentionally so that one can see the repair. It has a calcified internal mold.
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Calcite mold.
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Limestone mold of the phragmocone. Old German Chronostratigraphy: Malm (Weissjura) gamma 1
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Limestone mold. Old German Chronostratigraphy: Malm (Weissjura) gamma 1
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Leptosphinctes (Cleistosphintes) ex. gr. althoffi (Wetzel)
Ludwigia posted a gallery image in Member Collections
From the album: Middle Jurassic Ammonites from Southern Germany
8cm. in diameter. Found on a plowed field near Geisingen. Tetragona subzone, garantiana zone, Bajocian. -
Found in a discarded block at the edge of a plowed field. Index fossil for the tetragona subzone.
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This is the index fossil of the concavum zone. Most of the shell is preserved, as is a small portion of the body chamber. These ammonites could reach a good size, as shown by the sample in the last 2 photos, which has a circumference of 21cm. Lithography: Geisingen-Oolith The Geisingen-Oolith is a horizon which was built and reworked over a long stretch of time at the coastal fringe of an arm of the Tethys ocean. Fauna from both the concavum and the bradfordensis zones are to be found in it. Old German Chronostratigraphy: Dogger (Braunjura) beta Literature: Dietze et al (2014): Aalenian (Middle Jurassic) ammonites and stratigraphy of the Geisingen clay pit (SW Germany). Palaeodiversity 7: 61-127
