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aquadementia

New Zealand Glen Afric crab trip - first try!

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aquadementia

Hey there! I'm back again, and again I'm on another continent :) 

 

I moved to New Zealand at the beginning of the year, and in between the incredible fishing and birding I forced myself to head out to Glen Afric (2 hour drive) for a stab at some crabs.

 

The day started out with a couple belemnites, quite long and skinny. The concretions were various shades of khaki to black, some of them still more clay than rock. There were various shells encrusted in them. I kept my eyes peeled for a 'crab' shaped concretion, however this was easier said than done. After a full lap (about 400m) I was nearly back where I started when I picked up a rock, turned it over and holy moly it had legs!

 

Please tell me they're crab legs and not belemnites trolling me haha!! 

 

If it's a crab, would an air scribe be safe in the hands of an amateur? 

 

Anyway I had to go, but I'll be back!  

 

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aquadementia

some other bits and pieces, including a particularly spherical concretion

20180805_162412-10.jpg

20180805_162223-9.jpg

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KimTexan

It does not look like crab to me, but let other more experienced people weigh in. @RJB

 

New Zealand. I love New Zealand. I fell in love with the South Island when I was there. Although the North Island has a lot of cool stuff to see and things to do too. 

 

That is a beautiful remote looking place. The waters off the cost are such a uniques and beautiful color. Seeing it from a plane gives you a much better idea of the unique color.

 

You mentioned belemnites. Do you have pics?

 

Is that a little fish in that one concretion or an I imagining shapes? It looks like there is something else in there too.

 

 

3 pics from last on the right what is that? I am not familiar with that. May we have a closer up pic of it? The shells are cool.

 

Is that gastropod a fossil? Whether it is or not it’s pretty cool find. Not something you can easily find on beaches.

 

That 1.5 m long slab is way cool! It looks like a concretion, but I have never seen one  with a pattern quite like that. The sections running horizontal run the whole length of it. Whereas the sections around the top and bottom edges are a bit different. Very curious. I’ve seen concretions develop the turtle shell appearance, but the sections are reasonably uniform in shape and size and these seem to have 2 patterns at work.

I collect concretions. I’d love to have one like that, but that one is huge.

 

That is cool stuff. It looks like it may have been a bit heavy carrying those stones out of there.

 

A few months ago on here, I think it was that location that someone mentioned they had found a penguin in one of those concretions and something else very cool.

 

I look forward to hearing others comments.

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FossilDAWG

If the site yields belemnites it is Mesozoic, and I think the New Zealand crabs I am familiar with are all younger than that.  Do you know the actual geological formation and age?  Is the site definitely known to produce crab fossils? At any rate the "crab legs" you show do look more like belemnites in cross section to me.  Can you show a photo of the "long skinny" belemnites you found?

 

That is a beautiful site, and it does seem to produce interesting fossils.  That snail in one of the photos is especially attractive.

 

Don

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Auspex
7 hours ago, aquadementia said:

Please tell me they're crab legs and not belemnites trolling me haha!! 

They are likely oblique sections through crab appendages.
The site is Miocene, so there should be no belemnites present.

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Nimravis

Great finds and I love the pic of the coastline.

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aquadementia

Cool thanks guys! Mmmm perhaps the 'belemnites' were other crab legs hahaha.... I should have taken pics!! snarge :-/ 

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RJB

If your 3rd picture of the concretion is dorsal?  Then you have a left carpus and propodus showing?   Just the fact that part of that concretion is flatter on one side tells me that that is the front of the crab and the rounder part is the back of the crab.   A nice find, but a tuff prep with lots and lots and lots of hours.  looks like some really hard rock too.  I can only wish for you that it is not covered in calcite.  I would love to see this when its finished. 

 

RB

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aquadementia
On 07/08/2018 at 11:07 AM, RJB said:

If your 3rd picture of the concretion is dorsal?  Then you have a left carpus and propodus showing?   Just the fact that part of that concretion is flatter on one side tells me that that is the front of the crab and the rounder part is the back of the crab.   A nice find, but a tuff prep with lots and lots and lots of hours.  looks like some really hard rock too.  I can only wish for you that it is not covered in calcite.  I would love to see this when its finished. 

 

RB

It is soooo hard! But I just take that as a challenge :-) 

 

 

Here is another 'belemnite' from glen afric that a fellow fossil collector found there

20180808_164755.jpg

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crabfossilsteve

I'm guessing that your "belemnite" is actually a tusk shell since as discussed above belemnites went extinct during the Cretaceous Period.

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Oxytropidoceras

It is the Miocene Mt Brown Formation. Go see:

 

Rodney M. Feldmann , Carrie E. Schweitzer & Don McLauchlan (2006) 

Additions to the records for decapod Crustacea from Motunau and 

Glenafric Beaches, North Canterbury, New Zealand, New Zealand

 Journal of Geology and Geophysics, 49:4, pp. 417-427

https://doi.org/10.1080/00288306.2006.9515178

https://www.tandfonline.com/doi/pdf/10.1080/00288306.1993.9514568

 

and

 

Rodney M. Feldmann (1998) Paralomis debodeorum, a new species 

of decapod crustacean from the Miocene of New Zealand: First

notice of the Lithodidae in the fossil record, New Zealand Journal of 

Geology and Geophysics, 41:1, 35-38, DOI: 10.1080/00288306.1998.9514788

https://doi.org/10.1080/00288306.1998.9514788

https://www.tandfonline.com/doi/pdf/10.1080/00288306.1998.9514788

 

Feldmann et al. (2006) states:

 

"Because the cliffs are extremely steep and unstable, most of the 

concretions are collected from material on the beach that has 

been brought down by landsliding and subsequently winnowed 

out by wave activity. In fact, examination of the cliff faces from 

beach level rarely reveals exposed concretions."

 

The age is discussed by:

 

R. M. Feldmann (1992) Systematic and stratigraphic review with 

catalogue and locality index of the Mesozoic and Cenozoic 

decapod Crustacea of New Zealand, New Zealand Geological

Survey Record, vol. 45, 1-73.

 

According to Feldmann (1992), Mt Brown Formation is middle-late

Miocene, so a range of 5.33-15.97 Ma is estimated for it.

 

Yours,

 

Paul H.

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aquadementia

Thanks for your help! 

 

So I got myself a new tool today. This took about 3 hours

Screenshot_20180811-171104_Gallery.jpg

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KimTexan
On 8/11/2018 at 1:11 AM, aquadementia said:

Thanks for your help! 

 

So I got myself a new tool today. This took about 3 hours

Screenshot_20180811-171104_Gallery.jpg

It looks like it works reasonably well. I have a rotary Dremel I use with diamond tips, because that is what it takes to work with rock. I’ve considered buying that Dremel for certain types of prep.

I am inpatient. I’m not sure I could do 3 hrs and only get that far. Depends on how excited I was about the find. In my impatience I take a diamond tip circular blade and cut notches vertically and horizontally into the matrix a little ways, maybe 1/2 cm and then use a chisel blade to pop off the chunks by sliding it into the notch I created and then twist the chisel. It doesn’t work with all material.

 

I’m working on a concretion now and the method is working pretty well with the matrix. It doesn’t work well with limestone matrix. Even the notching is pretty slow going.a

 

This is my concretion. It has mollusks in it.  Clam and possibly some form of rudist. I’m not terribly fond of mollusks, but it is covered with beautiful iridescent nacre. So I think it’s worth the effort to try to prep it. I can’t use the Dremel or I ruin the delicate nacre. So I came up with the cut and pop off method.

This is maybe a foot or so long.

71E15C36-D7B9-4349-A2C6-EC3C43186BC4.thumb.jpeg.14dac5f54cf0746e876cbe40954ff03a.jpeg  C66DC103-CDC1-42AD-990C-5888EE4F3B3B.thumb.jpeg.88080c25fade690c63c2566d2ce68303.jpeg

 

Keep us updated on your progress.

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Doctor Mud

Any updates @aquadementia ?

 

I missed this original post.

The piece you are working on looks very interesting! The piece from your first photos and with the engraver.

 

Looks like bone in Miocene siltstone. Texture of the bone looks interesting and reminds me of an odontocete tooth dentine (bone).

@Boesse  

 

They look quite large, too large for the Kentriodonts “dolphins” that have been found there?

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Boesse

@Doctor Mud I think those could be sperm whale teeth owing to their size. I think vinegar might be very useful in dissolving these concretions; my PhD adviser Ewan Fordyce successfully prepped out some important dolphin skulls from these localities with acid.

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Doctor Mud
On 13/01/2020 at 3:05 AM, Boesse said:

@Doctor Mud I think those could be sperm whale teeth owing to their size. I think vinegar might be very useful in dissolving these concretions; my PhD adviser Ewan Fordyce successfully prepped out some important dolphin skulls from these localities with acid.

Quite an important find!

 

currently Canterbury museum is using mechanical prep. Which I can see has its disadvantages. The rock is very hard and doesn’t tend to flake off the bone nicely. Al Mannering does an amazing job, Ive watched him work and he let me try using a scribe on an odontocete skull. You almost have to “carve” out the bone with the stylus edge rather than exposing a nice bone face with the tip.lots of detail could be lost though.

 

Ive tried experimenting with acetic acid and it works really well. I think Paul Scofield from the museum now realises that acid prep is the way to go. So much detail can be lost with mechanical prep, even if you are a magician like Al.

 

Is there a paper you recommend that outlines the acid protocol? I have a few papers and the routine seems to be protect exposed bone, acid treat, rinse, dry, protect, repeat. 

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Ruger9a

Wow.....  Please post more photos of your snarge prep stages.  I love to see the process and outcome.  Thanks for sharing.

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Dave (POM) Allen

i agree nice teeth

 

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