Culpeper Basin Unknown

[patelinho7]

Hello all,

 

Quick backstory on this: I’ve been researching the Triassic Culpeper Basin of VA for a little while now. I’ve been paying more attention to various formations I see when I’m around northern VA especially after reading more about the stratigraphy of the area from old papers. I’ve taken a special interest in this red mudstone (or is it siltstone or sandstone? I don’t know the exact difference to be honest) because it’s what I’m familiar with. I participated in this program as a kid with Dr. Peter Kranz where he took us all over the DC area during a week in the summer and one spot was at a construction site in Manassas, where we looked for worm burrow ichnofossils. Talked recently with @Andúril Flame of the West about this. I had a couple small specimens from that trip with what I assumed to be the burrows/other traces so I knew roughly what rock type and structure to look for. And there’s plenty of this red rock all over NOVA. So I figured I would look at whatever red rocks I see just in case it would have something. Today I visited family in Ashburn VA and looked at some of these red mudstone-like rocks in their garden. They had gotten them from spoil piles when the community was under development to add to their garden decor. I saw sedimentary structures on many of the rocks, but this was the most clear one with something interesting going on. Just thought I’d post in case someone has insights on what it may be. Thanks!

 

Specifically, it’s the three-pointed marking on the rock. Is it a burrow trace, or maybe drag lines? It’s not a fracture or some other damage to the surface, the consistency of the rock surface changes and is almost like the soil was disturbed over that line and hardened as-is. 

apologies for lack of scale, didn’t have access to tools at the time and don’t have the specimen in my possession.

 

 

(Ashburn VA, Culpeper Basin-Newark Supergroup) 

[Andúril Flame of the West]

That’s certainly an intriguing specimen…

 

I agree that it is worth looking into and I am sure that @EMP or @cck will chime in with their expertise. In my rather uninformed opinion I would say it is probably some sort of sedimentary structure or possibly a worm burrow/tail drag of some sort. The reason I feel it may be a sedimentary structure is that I am rather familiar with these red sandstones (one source referred to them as hematitic sandstones though I am not sure if this is accurate) since I find them quite often in my yard and they often have interesting patterns. However, I could very well see it being a trace of some sort. Upon first viewing the pictures the marking reminded me of what a plant might look like but that is probably simply due to the symmetry of the supposed ‘leaves’. 

 

If this does turn out to be a trace fossil then I am the first to extend my congratulations! Either way, I do not doubt that you will soon come across some Culpeper Basin material. Best of luck in your explorations and I await your future posts .
 

 

[cck]

These look like mud cracks infilled to me… but that environment would be perfect for drags or other impressions… just not seeing them here. Keep your eyes open and good luck!

[patelinho7]

Alright, good to know. Thanks everyone. Good to know to continue keeping an eye out for these rocks.

[EMP]

Was going to say too they look like mud cracks. I agree those are generally a good sign for at least some worm burrows and maybe insect trackways. 

 

Let me know if you find any!

[cck]

Or insect eaters!

[Andúril Flame of the West]

44 minutes ago, cck said:

Or insect eaters!

 

Forgive me if this is obvious, but is this a fossil? I can't tell if I am supposed to be looking at the little raised 'nodules' or if there is something else that I am missing .

[patelinho7]

Yes I must agree that to the untrained eye, I’m not sure what I’m looking at on that rock.

[cck]

Hint

[cck]

They are positive track impressions of some critter

Edited June 5, 2023 by cck

[patelinho7]

2 hours ago, cck said:

They are positive track impressions of some critter

Ah I see, but of what critter?

[Andúril Flame of the West]

I suppose I might be able to make those out. Had I been on the field I without a doubt would have overlooked them.