Catskill Fm. Ichnofossil or geologic?

[Misha]

Hello everyone,

I just got back from collecting some fossil sites in Pennsylvania yesterday. Among these was a Catskill Fm. site, while the fishy finds there weren't particularly plentiful, I did manage to find some other interesting stuff.

 

While there I found these rocks which have unevenly spaced lumps scattered across the surface, on the other side the position of the lumps corresponds with round impressions in the rock. I initially thought this may be something like a layer full of concretions but with the dips on the other side of the rock I was wondering if it may be some kind of ichnofossil? 

If anyone has any ideas as to what this may be, I'd love to hear it, Thank you for looking!

In the field:

A closer look at the sample I took with me:

[Fossildude19]

That is an odd one, Misha.  I would think trace fossil of some sort.

Not sure, though. Could be some sort of load casts/sedimentary structure.

[Misha]

32 minutes ago, Fossildude19 said:

That is an odd one, Misha.  I would think trace fossil of some sort.

Not sure, though. Could be some sort of load casts/sedimentary structure.

Yeah, I like unusual sedimentary structures but have never seen anything like this.

 

The load casts from here tend to be much finer grained and very smooth, here's an example from yesterday:

 

Whatever it is is odd, if it is ichnofossil I wonder what would've made them. I'll take a look at some of my PDFs if anything mentions something similar, I think I had one on the ichnofossils of the area, but I'll have to find it

[Dawson Sensenig]

Cool rocks! I would have to agree with @Fossildude19, I think they may be some sort of load casts. Maybe this figure may be able to help, it makes sense to me at least, hopefully this helped! (I could be entirely wrong though!)

 

 

[doushantuo]

load casts(and/or gutter casts) is a distinct possibility,but maybe the bottoms of Rhizocorallium could also look like that 

edit: the Ordovician of Estonia has similar structures,of the right approximate size.

Edited May 24, 2023 by doushantuo

[westcoast]

In your first image the larger rock to the right appears to have them dispersed throughout the rock, although it is quite out of focus  so maybe that is something else. If they are dispersed that would rule out load casts.

[doushantuo]

I've sort of convinced myself pix I to IV do NOT show load casts

Edited May 24, 2023 by doushantuo

[Misha]

While reading through some literature, and looking online I found this:

From: PALEOECOLOGY OF THE FRASNIAN/FAMENNIAN BOUNDARY INTERVAL (LATE DEVONIAN), TIOGA, PENNSYLVANIA

"The Famennian section is marine at its base but fully terrestrial at its top, with a transitional zone of interfingering facies in between. In this transitional zone, disarticulated fish elements are common. The ichnofossil Bergaueria (attributed to burrowing sea anemones) is also found. In some specimens, these burrows are arranged in chains, perhaps reflecting asexual reproduction."

This seems like it could be a match to me, the object was found in a Fammenian deposit, they appear very similar to the burrows described, and the block that I have they are spread out exactly as described, in an arrangement of branching chains. Here are some images of similar specimens, although I couldn't find any examples from the Fammenian in PA to compare to.

Example from the Silurian in Canada:

From the Cretaceous in India:

These ichnofossils also seems to span a great lenght of time and come in various sizes from tiny, to rather large

What do you all think?

[doushantuo]

those images are from:

General Palaeontology, Systematics and Evolution (Taphonomy and Fossilisation)Ethological and environmental significance of Bergaueria
hemispherica from the Late Cretaceous of the Bagh Group,
Western India

Apurva D. Shitole , Satish J. Patel , Jaquilin K. Joseph , Jehova L. Darngawn

C.R.Palevol/2019

 

 

Misha,love your thinking

I THINK that the size distribution (see the first pic,near the hammer) is approaching a unimodal one,which might point to a recolonization surface

 

Edited May 25, 2023 by doushantuo

[EMP]

On 5/24/2023 at 10:07 PM, Misha said:

While reading through some literature, and looking online I found this:

From: PALEOECOLOGY OF THE FRASNIAN/FAMENNIAN BOUNDARY INTERVAL (LATE DEVONIAN), TIOGA, PENNSYLVANIA

"The Famennian section is marine at its base but fully terrestrial at its top, with a transitional zone of interfingering facies in between. In this transitional zone, disarticulated fish elements are common. The ichnofossil Bergaueria (attributed to burrowing sea anemones) is also found. In some specimens, these burrows are arranged in chains, perhaps reflecting asexual reproduction."

This seems like it could be a match to me, the object was found in a Fammenian deposit, they appear very similar to the burrows described, and the block that I have they are spread out exactly as described, in an arrangement of branching chains. Here are some images of similar specimens, although I couldn't find any examples from the Fammenian in PA to compare to.

Example from the Silurian in Canada:

From the Cretaceous in India:

These ichnofossils also seems to span a great lenght of time and come in various sizes from tiny, to rather large

What do you all think?

 

Very interesting stuff. It would really come down to what member of the Catskill Formation you found this in. 

 

According to Wikipedia, that genus went extinct by the end of the Silurian: Bergaueria - Wikipedia, but like your pictures show people have apparently found them from the Cretaceous. 

 

Here's a plate from a report about Bergaueria from the Cambro-Ordovician of California and Nevada:

 

 

It seems like the distinguishing feature between these and load casts would be how the objects are positioned with respect to the country rock. The Wikipedia article on load casts is pretty clear on what they would look like:

 

 

Could you take a side view of the specimen, showing how the objects cut across the layers? The rock looks pretty uniform in sediment type which would make me lean towards trace fossil, but a side view would help confirm one way or the other.

[Misha]

16 hours ago, EMP said:

Very interesting stuff. It would really come down to what member of the Catskill Formation you found this in

Might not actually be the Catskill, I'm not too sure. I believe this was on the boundary of Catskill Fm. And the Underlying Lock Haven Formation, as not far away from these I found some Cyrtospirifer sp. brachiopods and going further along the cut I got into the Catskill fish beds.

 

16 hours ago, EMP said:

Could you take a side view of the specimen, showing how the objects cut across the layers?

It's not very easy to take a good side view of this rock, here is my first attempt, it shows a few of these burrows in side view. I will try to get a better setup to take a better picture.

Interestingly all of the bottoms of the structures are tapered but instead of coming to a point or rounding off the very bottom itself is flat

[EMP]

On 5/26/2023 at 3:49 PM, Misha said:

Might not actually be the Catskill, I'm not too sure. I believe this was on the boundary of Catskill Fm. And the Underlying Lock Haven Formation, as not far away from these I found some Cyrtospirifer sp. brachiopods and going further along the cut I got into the Catskill fish beds.

 

It's not very easy to take a good side view of this rock, here is my first attempt, it shows a few of these burrows in side view. I will try to get a better setup to take a better picture.

Interestingly all of the bottoms of the structures are tapered but instead of coming to a point or rounding off the very bottom itself is flat

 

The photo is kind of blurry, but I think the rock looks uniform enough, and the orientation of the bumps is non-congruent enough, to make me think it isn't a case of load casts. The side view seems to show some of the "bumps" are oriented in roughly the same pattern, but the first photos seem to show that some of them point in opposite directions, which doesn't appear to be typical for load casts. 

 

I'm not as familiar with the Catskill and Lock Haven Formations, but IIRC the contact between the Foreknobs Formation and the Hampshire Formation (which are pretty much stratigraphically equivalent to those two formations, albeit further south in Pennsylvania/Maryland) is at the topmost marine-fossil bearing layer. If you found these above the Cyrtospirifer sp. layer, and assuming there isn't a fault, I would think these come from the basal part of the Catskill. In that case, since anemones have been found in those rocks, these don't appear to have characteristics common to load casts, and they appear similar to the pictures of the trace fossils above, I would lean towards these being trace fossils.