Holey Devonian Dolomite!

[Mediospirifer]

I was checking out a local creekbed with my husband, and he spotted this interesting rock:

I'm wondering if the voids in the rock were originally a calcified coral fossil that weathered away? The rock could be shale, or possibly dolomite. I'm not sure which although shale is far more common around here.

Here's a few close-ups of the interior of the voids:

This one shows a texture that may have been left by the original organism.

Here's a couple where the void is still filled, and the structure of the original organism can be seen.

This one has the interior organism in the process of weathering away.

Several of the holes go all the way through, some also branch. Others go at least an inch into the rock. That's a bit harder to get a good photo of!

Anyone recognize this? Thanks!

[squalicorax]

Looks like some Thalassinoides burrows

[pinkpantherbeekeeper]

From my limited knowledge I would guess burrows. The pieces of hash with coral worn away typically don't leave deep holes, from what I have found in dolostone/limestone. Also there always seems to be a small piece left in the matrix somewhere. I will interject though, i have seen water wear some neat holes and patterns into rocks however.

[Herb]

I would say trace fossils also.

[Mediospirifer]

Thanks, guys! I looked at some images online, and that does resemble my rock. Mine has holes while most seem to have casts, but the pattern is very similar. I'll label it as Thalassinoides (trace fossil), at least for now.

pinkpantherbeekeper, my last three pictures are of some of the pieces left in the holes. Also, while the burrows go into the rock for a significant distance, they do so at a very shallow angle. I've never found anything quite like it!

I do notice that some of the online pictures mention a bed of Thalassinoides in Ottowa. I'm wondering if this is a glacial erratic!

I found a few other interesting fossils in the same creekbed, I'll post pictures when I have a chance to photograph them by daylight.

[pinkpantherbeekeeper]

Sorry about that Mediospirifer. I was unable to see the last three pictures in full detail. I see what you are saying now! So is that fill material or part of a coral? Cool find and congrats!

[Mediospirifer]

So is that fill material or part of a coral? Cool find and congrats!

Thanks! I don't really know what it is. The first of the three pictures does show what might be coral structure, although it could be mineral crystal. The last has an interesting wear zone.

If I could positively identify it, I'd have posted it under "Discussions". I thought it was weird and worth posting, regardless of what it is.

[fossilcrazy]

Looks like branching Bryozoans that were dissolved out of the encasing rock. The fossils made of Calcite Carbonate are prone to dissolve before the Sandstone or as you say Dolostone.

Bryozoans would have a pore resembling structure. The form looks like Cladopora or Thamnopora but your pictures show a smaller scale structure. Interesting rock to be sure.

[Mediospirifer]

Looks like branching Bryozoans that were dissolved out of the encasing rock. The fossils made of Calcite Carbonate are prone to dissolve before the Sandstone or as you say Dolostone.

Bryozoans would have a pore resembling structure. The form looks like Cladopora or Thamnopora but your pictures show a smaller scale structure. Interesting rock to be sure.

That reminds me that I forgot to include the scale! Sorry about that.

The whole rock is 13 1/4" x 6" (34 x 15 cm). The tracks on the surface are around 1 cm wide. The semicircular feature in the 2nd micrograph is 11 mm diameter. The pores are indeed tiny!

My one serious complaint about my microscope is that the light source is built-in and can't be controlled. I'd love to be able to side-light these features to more accurately show the relief.

Thanks for the observations!