New Zealand: Found in a Cretaceous area - reminds me of a tree fern

[mamlambo]

I found this in a stream bed in a place that I think is a Cretaceous area. At first I thought it could be the trunk of a tree fern or similar, but I have no idea. It's about 20cm long, 15cm wide and 11 cm high with a circular pattern. Please help

 

 

[FranzBernhard]

Very interesting, thanks for sharing!
I have fiddled a little bit with your pics. Still don´t know, what it is. But would also like to know... .

Franz Bernhard

[mamlambo]

Thanks Franz! That does look much better!

[Rockwood]

Interesting. Individually one might think of them as concretions. Why this configuration is a good question though.  

[Plantguy]

That is a pretty cool rock! Not sure what you have. Could you possibly wet the surfaces with water and retake some sharp closeups if possible?..looking to see the finer grain/structure details within the concentric areas and around them.

I'm wondering if not fern, concretionary, maybe even stromatolitic or something else? The recurring pattern is really interesting and there are some very irregular/angular shapes in between some of the concentric forms that are intriguing..

 

Maybe closeups will help narrow it down...

Regards, Chris 

[ynot]

This piece looks like it was fractured when in bed and water percolating through the cracks has leached minerals from the contact.

 

Not seeing a fossil here.

[Rockwood]

41 minutes ago, ynot said:

This piece looks like it was fractured when in bed and water percolating through the cracks has leached minerals from the contact.

 

Not seeing a fossil here.

Septarian uncretion. 

[Plantguy]

40 minutes ago, ynot said:

This piece looks like it was fractured when in bed and water percolating through the cracks has leached minerals from the contact.

 

Not seeing a fossil here.

Hey Tony, I agree it could be fracturing/weathering as well. I just want to see it up close-

Regards, Chris 

[abyssunder]

I don't know what it may be, but the concentric features are aligned almost perfectly in longitudinal and transverse rows.
Very interesting! 

[mamlambo]

Here is another photo of the edge, wetted with water:

 

 

[mamlambo]

And another of the top, also wetted with water

[mamlambo]

@Plantguy I added some more photos of it wet. Would it help if I cut through a section of it to see if there is any structure to it? Also, I was looking at cycads - there looks to be a slight resemblance to some photos I see online.

[Rockwood]

1 hour ago, mamlambo said:

Also, I was looking at cycads - there looks to be a slight resemblance to some photos I see online.

A fossilized cycad blossom would be something.

Ya s'pose it could be ? 

[mamlambo]

7 minutes ago, Rockwood said:

A fossilized cycad blossom would be something.

Ya s'pose it could be ? 

I can always hope! I'm at a bit of a loss as to what it could be, quite possibly it's not even anything fossilised and is just some mineral. It's very symmetrical though.

[Notidanodon]

Cooled magma looks similar in shape

[Plantguy]

7 hours ago, mamlambo said:

@Plantguy I added some more photos of it wet. Would it help if I cut through a section of it to see if there is any structure to it? Also, I was looking at cycads - there looks to be a slight resemblance to some photos I see online.

Hey Mamlambo--Thanks for the additional photos..they are very good. I still dont know what you have. LOL. I was hoping it would be obvious but I think I'm out of my league with providing an answer. I dont recognize the microstructures or the macroviews. We need some experts to review your photos either here on the forum or elsewhere to hopefully come to a consensus. I am curious to see some of the new ID suggestions and not discounting the old ones. Let me copy Tim and Scott and see if they have any ideas and/or similar examples so that we might be able to rule in/out the plant possibility. 

@paleoflor, @piranha Tim/Scott do either of you recognize this unknown??

@ynot Tony, do the newer photos change anything for you??

 

I've gone ahead and also sent a msg to some folks down your way in New Zealand in hopes of getting some local feedback and expertise. I'll let you know if I get anything. 

 

It might be interesting what a cut& polished section thru that beast would produce but lets wait to see if we can get a couple more folks to look--I kind of like it uncut for its uniqueness alone..

Regards, Chris  

 

[ynot]

I am still of the same opinion on this.

[Plantguy]

6 hours ago, ynot said:

I am still of the same opinion on this.

Thanks Tony! I respect that. The apparent 3D symmetry of the larger concentric shapes doesnt make sense to me as a plant and I dont know what I'm seeing in the fine semi polygonal shapes which seem to have differing internal structure....very well could be just geologic/weathering--mother nature has its way of creating some pretty neat stuff one way or the other.

Regards, Chris 

[Plax]

I think that a fellow New Zealander would have a better shot at identifying this. The radial symmetry makes me think plant but can't say with any conviction.

[mamlambo]

So I sent the photos to the Paleontology department of our local university and someone got back to me within 15min! They suggested it could be a Eocene-Oligocene era coralline red algae called Rhodolith which are found here in New Zealand.

 

Anyone ever found any Rhodolith?

[FranzBernhard]

Interesting twist on this one, @mamlambo!

25 minutes ago, mamlambo said:

They suggested it could be a Eocene-Oligocene era coralline red algae called Rhodolith

https://en.wikipedia.org/wiki/Rhodolith

 

26 minutes ago, mamlambo said:

Anyone ever found any Rhodolith?

Yes, rhodolithic limestones are abundant around me in the miocene Styrian Basin of Austria.

Specimen size ca. 12 cm, polished slab, Weißenegg-Formation, Styria, Austria (Miocene, ca. 15 Ma):

But someone else may have better specimens... 

Franz Bernhard

[Rockwood]

1 hour ago, mamlambo said:

Anyone ever found any Rhodolith?

I suspect the number that have may exceed the number who realize it. 

[mamlambo]

@FranzBernhard That is a stunning piece! What still gets me is the symmetry in the piece I found. Apparently, if I put some HCL on it, it should fizz which is a good indicator for it being the correct type of rock.

[FranzBernhard]

1 hour ago, mamlambo said:

What still gets me is the symmetry in the piece I found.

Indeed! Still unexplained. But I don´t know what could happen with the rhodoliths in such limestones. Another problem is, they appear to be all of similar size??

 

Another thing is the internal structure of the round objects. Do you see any kind of (concentric) banding, lamination etc. within the round objects?

 

1 hour ago, mamlambo said:

if I put some HCL on it, it should fizz which is a good indicator for it being the correct type of rock.

We all assumed that it is "limestone", I think . So a test with HCl is in order!
Franz Bernhard

[Plantguy]

Fantastic that you've gotten an answer! Sorry I've been working and not heard back from the local inquiry I put out but I'm very glad you heard something. 

I've not run into those personally in the fossil record but they seem to be fairly common. I'll have to go looking around in the literature for any Florida fossil examples and I see quite a few pubs written about NZ ones....that pattern still intrigues me alot. Congrats!. 

Regards, Chris 

 

Added this image 

From:

Distribution of Carbonate Reservoirs Controlled by Volcanism in the Canterbury Basin, New Zealand* Kari N. Bassett1 , Nicholas K. Thompson2 , and Catherine M. Reid3 Search and Discovery Article #30520 (2017)** Posted October 9, 2017

 http://www.searchanddiscovery.com/documents/2017/30520bassett/ndx_bassett.pdf

Edited June 28, 2019 by Plantguy
Added photo