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Trace Fossil?


Daniel Frew

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Came across this today on a short hike in Norther Pope County Arkansas. Guessing its a trace fossil.

post-21158-0-20520200-1467157690_thumb.jpg

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My first thought was bore holes (i.e. agree with trace fossil), but the holes being so uniform in size and distribution gave me pause.

But in the side shot, the holes are not very straight so I'm thinking "wormy".

Then, when I look closely at the top view of the holes, a lot of them look to be lined which might be from lubricating secretions.

See what the experts say.

  • I found this Informative 1

Info: Craig Hyatt, retired software/electrical engineer

Experience: Beginner, fossil hunting less than a year

Location: Eagle Pass, TX USA on the border with Mexico, hot dry desert

Formation: Escondido, Marine, Upper Cretaceous

Materials: Sandstone, Mudstone, Shale, Chert, Chalk

Typical: Thalassinoides, Sphenodiscus, Exogyra, Inoceramus

Reference: http://txfossils.com/Txfossils.html

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I'm not the expert to evaluate this piece. In fact it's rare to see an assignment of trace to maker. I have read that the concept Craig mentions is quite valid though. Mucus does facilitate fossilization.

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I think it is a trace, but maybe not a fossil. I think the holes are fairly modern tubeworm holes.

http://www.google.com/search?q=rock+boring+tubeworm&btnG=Search&hl=en&gbv=1&tbm=isch

So the tubeworms bored the holes after the rock was formed. That would explain why they are not infilled and have what seems like fresh activity to them.

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Opps! Better put your hat back on! I think I might be half wrong.

I forgot that this is coming from Arkansas, and it looks like marine tubeworms, so that would make it a fossil!

The fact that the holes are still clear seems odd, if this is many millions of years old. Seems like some sediment would have settled and solidified in there.

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all the tubes are orientated more or less the same way,and of more or less equal thickness.Would anyone qualify the holes as being "equidistant"?

Edited by doushantuo

 

 

 

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all the tubes are orientated more or less the same way,and of more or less equal thickness.Would anyone qualify the holes as being "equidistant"?

No, not mathematically equidistant. They are not totally random spaced either, they are spread out to give each other space, but not with an order to it.

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all the tubes are orientated more or less the same way,and of more or less equal thickness.Would anyone qualify the holes as being "equidistant"?

I'd say "uniformly distributed". In my own field of computer science there are algorithms for "random tiling", "random fill", "circle packing", etc. designed to create random, but uniform patterns as seen on this fossil.

There are biological mechanisms to achieve this as described in "Endless Forms Most Beautiful" by Sean Carrol.

There are chemical analogs like the BZ reaction: https://en.m.wikipedia.org/wiki/BelousovZhabotinsky_reaction

post-20989-0-06288800-1467206933_thumb.jpeg

Edited by CraigHyatt

Info: Craig Hyatt, retired software/electrical engineer

Experience: Beginner, fossil hunting less than a year

Location: Eagle Pass, TX USA on the border with Mexico, hot dry desert

Formation: Escondido, Marine, Upper Cretaceous

Materials: Sandstone, Mudstone, Shale, Chert, Chalk

Typical: Thalassinoides, Sphenodiscus, Exogyra, Inoceramus

Reference: http://txfossils.com/Txfossils.html

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