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Kato

Trace fossil? Bivalve borings?

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Kato

Okay, I had originally just thought this specimen was a 'mother nature playing games' kind of rock when I was out exploring on a day that turned out to be filled with lots of trace fossils.

 

After some online research for Ordovician trace fossils I came across some Flickr photos for Petroxestes pera, bivalve borings, that were once called 'turkey tracks'. The particular photo panel labeled, Petroxestes pera bivalve borings on limestone hardground (Turkey Track Layer, Waynesville Formation, Upper Ordovician; Flat Fork Arm of Caesar Creek Lake, Warren County, Ohio, USA) , looks quite similar to the strange marks I found in this upper Ordovician formation here in southern NM. 

 

Any trace fossil turkey track experts willing to comment? 

 

image.thumb.png.b867634d0783ab90858f809fd2b626ab.png

 

Thank you in advance, Kato

 

 

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Plantguy

What size are these? Need a scale for reference. Do you happen to know the formation name?

 

Some appear to have a 3d raised relief to them but that could just be the camera angle/photo...and at first I thought they were grains like large forams...they are all channels/grooves/depressions correct?

Regards, Chris 

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Plantguy

Was just looking around as I wasnt familiar with Petroxestes...

 

Petroxestes pera

It is a bioerosional ichnotaxon, occurring within lithic substrates, and is characterized by a shallow to deep elongate outline, broadly parallel sides, and a rounded bottom in longitudinal and transverse section (Pickerill et al. 2001)

 

Seems to have the general description described above...some of the traces do look like they have squared off ends....Is that really the case?

Regards, Chris 

 

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Kato
2 minutes ago, Plantguy said:

Was just looking around as I wasnt familiar with Petroxestes...

 

Petroxestes pera

It is a bioerosional ichnotaxon, occurring within lithic substrates, and is characterized by a shallow to deep elongate outline, broadly parallel sides, and a rounded bottom in longitudinal and transverse section (Pickerill et al. 2001)

 

Seems to have the general description described above...some of the traces do look like they have squared off ends....Is that really the case?

Regards, Chris 

 

Hi, it is alleged to be Ordovician Montoya. I only took a single shot and only a portion of the overall exposed panel.

 

More info:

 

(1) Thickness of this tan-colored specimen layer is about 25-40mm and it overlays a lighter colored limestone.

(2) To the left side of the panel a very dark colored layer begins to overlay the tan colored specimen panel and appears to be the in-fill for the ones not open. The farther left you would go (out of pic) the thicker the dark colored material (richer blacker mud?).

(3) Estimate a 50/50 split overall between open or filled grooves with the dark colored material being the in-fill. The shot I took seems to be more in-filled by percentage

(4) Most of the open ones have a rounded, tapering appearance. Some are more squared off.

(5) Most are in the 25mm range for length. Some longer, some shorter.

 

I may try to stumble back that way with some wider narrower chisels to obtain a sample. It may be possible to separate some sections from the underlying limestone.

 

In the following...from a source about bivalve boring grooves, lengths vary with some 'appearing' to be less rounded than others. The less rounded ones appear to be deeper set borings.

 

image.png.00a038b3a482311a48b8af3c7ce96b6d.png

 

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Kato

From another location with some in-fill material and showing some with more or less rounded impressions

Petroxestes111212.jpg

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Plantguy
1 hour ago, Kato said:

From another location with some in-fill material and showing some with more or less rounded impressions

Petroxestes111212.jpg

Great info...I'll dig around a bit more...I'm not an ichno person but this additional info makes me believe you might have the right ballpark/genus but I defer to those more familiar with them. I'm wondering if anyone else knows for sure...Lori has done alot of awesome ichno research on the forum and I'm wondering if he's run across them already. I did a quick ff search and dont see that ichnogenus showing up/being discussed before...

@abyssunder

 

Regards, Chris 

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abyssunder

A far as I can see, your traces are positive epireliefs rather, than negative epireliefs which are usually visible on bedding plane with Petroxestes borings, as you exemplified in the pictures from the internet. I suppose, the overlaying dark sediment had the borings. Your specimen may have the infills of the borings from the overlaying stratum, or I don't reed correctly the features of your picture, Kato.

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