MEDUSA OR NO MEDUSA -
THAT IS THE QUESTION...
 

NEOPROTEROZOIC / CRYOGENIAN:
ORGANIC OR INORGANIC?

I got these pictures from Michael Szwabo. These structures were found near Kunanarra in Western Australia. Michael wrote: "They are from the Ranford formation in W.A., and they are 670 m.y. old. Some people think these are evaporites or gypsum crystals, others think they're jellyfish or some sort of metazoan." - What do YOU think?

                
 
 
Comments
 
Interesting! Ask Michael Gilmer. He is a fossil guy.
 
Metriterium Galerie probably jellyfish as i see the tale of one these specimens fossilised
Андрій Мартишин I found similar structures in layers of fossil-rich Ediacaran biota. Statistical analysis showed that these are not organic formations.
Brooke Johnson Some kind of mineralisation rather than a fossil. They look pretty cool though so still a nice find.
Thomas Kapitany I’m selling them .
Mineralogist say they are not minerals or evaporites. It is West Aust Museum that calls them evaporites. Kath Grey has only examined a couple of hand size specimens in the Geoscience collection and never visited the
site, based on early datings of 2 billion years.
Ranford formation has since be re dated to a more recent date. Tha deposit sits above the Zebra stone deposits which are also microbialites large Medusa have been found in the deposit as well as other larger organic strictures in area.
Michael Szwabo Thomas Kapitany thanks tom uwe was very interested in any info possible.
Thomas Kapitany I will update pics and info later it’s 2 am here
Brooke Johnson Interesting, so that makes them ediacaran? I have some zebra stone but my specimens are flint clay rather than microbial and the stripes are certainly diagenetic rather than primary. Thomas Kapitany how much are you selling these specimens for? I would love to get hold of some to analyse properly.
Brooke Johnson Those are lovely images, but sadly morphological similarity is not enough to be conclusive evidence of these being fossils. Especially not of a specific taxa like Porpita. To me these look like some kind of diagenetic mineral growth that has been altered, perhaps by modern weathering. An example could be radial pyrite growths that have then been oxidised, or perhaps amorphous organic matter that was diagenetically reduced and recrystalised. We has similar structures here in the Devonian on the south coast of Devon that look biological but are infact diagenetic.

In this case, I can only work from the photos here, in a few of them it looks as though the structures cross cut sedimentary features and post-compactional lamina, usually a sure sign of a diagenetic origin.

Have you checked out the episode of palaeocast that is all about fossil jellyfish etc? If not it's well worth a listen and might help you understand what you are seeing in these rocks.
Thomas Kapitany Not diagenetic
Thomas Kapitany I have lots of. Discussion with ANU in Canberra
And they are in the process of studying with material along with zebra stone
Gregory Retallack Who at ANU is studying zebrastone? I need to contact them.
 Thomas Kapitany I will get better pics later
Thomas Kapitany Driving To Munich now
Brooke Johnson Cool, what is your evidence for them not being diagenetic? I collaborate with some folks at ANU, who is it you are talking to? Have a safe drive! :)

Thomas Kapitany My question is, what evidence do you have that it is diagenetic ?
Brooke Johnson Thomas Kapitany cross cutting relationship with sedimentary fabrics particularly with post compaction lamina, and what appear to be veins. Though that is just based on the photos.
Thomas Kapitany Ripple marks
Thomas Kapitany More to the point you appear to be an academic ?
Brooke Johnson I guess so, I am finishing my PhD on the Mid-Proterozoic sediments of Northern Australia here at Oxford in the UK.
Thomas Kapitany I have some great photos
Brooke Johnson That's a nice photo! I am working on the Velkerri Formation primarily and picked up some Zebra Stone when I was in Darwin. There was a guy selling it at the beach market who had some nice bits and we had a chat with him about it. I'm not interested in the Zebra stone per se, but that style of sedimentation is common in the rocks I look at which go back to 1.4 Ga.
Thomas Kapitany Anyway ripple mark pattern is very distinct
Thomas Kapitany That’s why it’s not diagenetic
Brooke Johnson Cool! But how can you say that the ripple effect is not caused by displacement of the light layers by the red layers? Additionally, depositional compositional differences during the formation of ripples can act as a conduit for later fluid flow as well. The latter is another phenomena I have observed repeatedly over the years. I might make a thin section from my chunk of Zebra stone to see what is going on because the red stains I can see in hand specimen are definitely something late stage and not depositional.
 
Thomas Kapitany Brad Pillans
They just published on zebra stone
Thomas Kapitany Andrew Coward from Monash is doing his PhD on it
Thomas Kapitany Under Dr Anja Slim and Brad
Thomas Kapitany Mostly working in Zebra stone
Thomas Kapitany I have and will provide lots of information as I have explored extensively though out the region
Thomas Kapitany ANU screwed up badly a few years ago with their publication on Zebrastone
Thomas Kapitany The latest publication is much better but they were inconclusive with regards to its formation and patterns.
Bruce Stinchcomb Some of these specimens appear to be folded as though they were originally composed of a material which was flexible (like an organic substance). If they were crystals like selenite or some other inorganic mineral they would not do this.
Thomas Kapitany Yes . But they are definitely not selenite.
Mineralogists have varieties that.
Also they are not aware of any other mineral with that habit
Brooke Johnson Radial pyrite looks like this, as do some of the sulphate weathering features I see on my black shales. :)
Thomas Kapitany Yes they are biological also
Thomas Kapitany Sulphides in black shales are biomediated
Brooke Johnson In what what way? A lot of the sulphides I find are diagenetic, hydrothermal or even detrital.
John A. Spina Jr. I've heard them called Eoporpitia. The age seems right. There is a Medusae form to them and yet is it organic or inorganic record?

Bruce Stinchcomb Some of these specimens appear to be folded as though they were originally composed of a material which was flexible (like an organic material). If they were crystals such as selenite or some other inorganic mineral, they would not do this.

Michael Szwabo One when is the things that Bruce Stinchcomb noticed was that many of these structures un are are rolled over or Lipped. If these were crystals they would break it would require a leathery kind of Skin or dermis for them to roll up and over and that was a pretty convincing argument to me .indeed ifthey were Crystal and they would break and shatter.

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