A Weekend Visit To A Southeastern Pennsylvania Road Cut

[hitekmastr]

A Weekend Visit to A Road Cut Near Our Home

Nan was busy this weekend so I drove to a road cut on Route 422 south of Pottstown, PA - about 5 miles from our house. I had been told by a friend at the Delaware Valley Paleo Society that there wouldn't be any fossils here - from the geological record, I think this is part of the Gettysburg-Newark Lowland Formation which is described online as late Triassic. The shale is red with some green and gray mixed in here and there.

Telling me that there wouldn't be any fossils here was a challenge I couldn't resist. So I decided to see if I could find anything in this very barren but geologically interesting formation. What I found were fossils and impressions of a tree and twigs that resemble Siggilaria (which were extinct by the Triassic I believe), and a few other trace fossils and what I assume are some mineralizations that look like leaves but probably aren't. I wonder what kind of tree this bark pattern represents...any ideas?

The roadside exposure is a very steep slope covered with golf ball sized rubble and lots of larger rock formations protruding, here and there. The roadcuts are located along Route 422 several miles south of Pottstown, Pennsylvania. I studied everything that was visible, cracking lots of rocks to see what might be hidden. Nothing, no marine fossils, not even a freshwater clam. I began to feel that this might have been a dry area, or mostly dry area.

Then I came across a narrow cascade of rubble that had eroded off the steep wall and noticed some red shale pieces that looked like smooth bark of some kind. On closer inspection, I discovered several pieces (many were fragmented) that turned out to be a grooved bark pattern. In the first fossil (1.1, 1.2 and 1.3 with backview and closeup - see below) you can see: a) the bark pattern which resembles Siggilaria including one branch node (the round circle) and you can also see at the top where the bark ridges begin to branch into a diamond shaped pattern. Although this is supposed to be a Triassic formation, the tree bark has a Carboniferous look, but I'm not familiar with Triassic trees. Here are the images of the bark sample:

BARK 1.1 BARK 1.2

BARK 1.1 Back View BARK 1.1 CLOSE

Bark 2.1 and 3.1, and Fossil 4a(front) and 4b (back) - These are additional samples of what appear to be bark and branches/twigs:

BARK 2.1 BARK 3.1

FOSSIL 4a Front FOSSIL 4b Back

Twig 5 - Here is what appears to be a twig and twig impression:

TWIG 5

Not sure what this is:

FOSSIL 6

I assume these are mineralizations (dendrites) that look like leaf impressions but are chemical, not fossils - note the shale color is different from the red shale above (labeled Mineralization 1 and 2):

MIN1 MIN2

Anyway, I guess my point is that I visited a road cut that is close to home, easy to access, and where I was told there should be no fossils. I found quite a lot to look at and ponder, and best of all, despite being parked on the roadside for 3 hours, I wondered if I would receive a visit from curious police but not at all so I felt very comfortable, except for the times when I climbed some very steep sections and found it a bit tricky to make my way back down the steep crumbly slope (I got down by choosing a section that had small samplings and used those as grips on the way down).

I'm still not sure what else might be here or at other roadcuts but I have a hunch that this must be what fossil hunting in "dry" tree and plant areas might be like, since all the sources claim that not many dry forests were preserved as fossils because there wasn't much mud in the dry areas and they almost needed to be buried in a rockslide or freak flood to be preserved. Paleobotanists also suggest that the fossil record is heavily weighted toward wetland plants and trees so anything that comes from what was originally "dry" forest or meadow is worth inspecting.

Edited October 14, 2012 by hitekmastr

[Auspex]

The shapes are certainly enticing, but I'm not sure that they are incontrovertibly tree bark; they also could be ripple marks and mineral infillings of cracks. The moss-like mineral deposits are dendrites, probably manganese.

[hitekmastr]

The shapes are certainly enticing, but I'm not sure that they are incontrovertibly tree bark; they also could be ripple marks and mineral infillings of cracks. The moss-like mineral deposits are dendrites, probably manganese.

Fossil collecting is all about patterns, which is one of the big lessons for any collector - making sense of the patterns is tricky and can be misleading, I agree.

I have to admit, at first I thought the first "bark" sample (1.1) might have been a geological pattern and not bark until I looked more closely and saw the diamond shaped connections of the ridges at the top of the sample which is very barklike and that's the one that looks the least coincidental (see the outlines traced in yellow, below)...also there are other samples of this "bark" but much more fragmented that confirm this was a larger fossil, but I didn't collect or try to piece together those fragments. I would also argue that the opposite side of Bark 1.1 looks more like the interior of a tree which supports the tree theory. Also, all of these impressions were found in the same very small area.

To argue against "bark" the round circle in conjunction with the bark pattern would seem to suggest bark however I don't think the placement would be where a typical bark branch or root or leaf scar would be. Another bit of evidence for what it's worth is that the round circle goes all the way through the sample and shows up on the other side (the "interior" view).

Edited October 14, 2012 by hitekmastr

[elcoincoin]

min 1 and 2 : manganese oxyde for me (MnO2)

edited : wrote too fast: it is dentrites imo

Edited October 14, 2012 by elcoincoin

[Terry Dactyll]

I'm with Auspex ...I reckon sections of ripple marks... You do get changes in the 'ridge line' on these ripple marks... Heres some carboniferous ones I collected a while back have a close look... I quite like them I have the big one on my wall in my room now...

[Auspex]

Even if they are ripple marks, they are a record of the movement of (in this case) water; this particular structure is called "catenary".

There is even a discipline of study within sedimentology which is concerned with such! LINK

[Bullsnake]

We have some nice outcrops of that around here. I think they are fascinating, especially when you see the modern form in lakes, and can visualize the same thing happening way back then.

A lot of them are very busy with trackways, too, on both sides, but predominantly on the bottom.

[hitekmastr]

We have some nice outcrops of that around here. I think they are fascinating, especially when you see the modern form in lakes, and can visualize the same thing happening way back then.

A lot of them are very busy with trackways, too, on both sides, but predominantly on the bottom.

Fascinating - thanks everyone for the input - this trip report is a really good example of a visit to a site where there essentially aren't any fossils of the quality we're used to finding - well, ok, no fossils at all but traces and patterns and evidence of geological activity - but we learn something from every trip! Each site visit is a revelation and the education we're getting from these explanations from members helps us mature - really fast - as collectors!

Edited October 15, 2012 by hitekmastr

[Fossildude19]

Fascinating - thanks everyone for the input - this trip report is a really good example of a visit to a site where there essentially aren't any fossils of the quality we're used to finding - well, ok, no fossils at all but traces and patterns and evidence of geological activity - but we learn something from every trip! Each site visit is a revelation and the education we're getting from these explanations from members helps us mature - really fast - as collectors!

Michael,

I wouldnt completely give up on this roadcut. Like all Newark Supergroup areas, there are large spans devoid of fossils, but sometimes a few yards, feet, or even inches can mean the difference.

Keep at it, as ripple marks and mudcracks are great indicators of possible ichno fossils, and other fossils, potentially.

Look for the fine grained siltstones, mudstones and red shales, along with the gray shales which can sometimes have carbonized remains of conifers in them.

I frequently split hundreds of pounds of shale at my plant site to find only a few conifer fossils. Hard work, but rewarding when it does finally pay off.

Regards,

[Terry Dactyll]

We have some nice outcrops of that around here. I think they are fascinating, especially when you see the modern form in lakes, and can visualize the same thing happening way back then.

A lot of them are very busy with trackways, too, on both sides, but predominantly on the bottom.

Steve... WOW... I really like the look of those ripple marks... Very unusual how they have formed...possibly created in deeper water than the ones I found maybe?...

[hitekmastr]

Tim (and everyone),

Thanks for the encouragement - very cool. I visited this roadcut because I've been looking for something really close to home, a few minutes away, that I could visit now and then during the Fall/winter months. I agree there must be a pocket or two of fossils somewhere in this formation. The trace patterns I found were really encouraging and whether this is 1) a mostly dry environment, or 2) a deep water/mud environment, then it will take a LOT of searching and fracking of shale to find something, but then, anything found would be quite interesting. Actually, all the posts in reply to my trip report inspire me to keep going. Your comment about splitting "hundreds of pounds of shale" made me laugh like crazy because Nancy and I know what that means!

I'm in "Fall mode" right now which for me means looking for something a bit obscure, exotic, hard to find, difficult to identify, ideally close to home - all of that - as time permits. There is also an interesting olive green colored shale road cut on the same highway that I will check out soon. I don't understand the geology of the Newark formations at all and it's hard to find online - the geo maps I checked out suggest this is Triassic. There are several different types of rock in the formation, and trying to understand the distinction is also a challenge.

Also, Nancy indicated she wants to go back to St. Clair once more this Fall, because we know the site so well and feel like we're standing in the coal swamp when we're there so it looks like one more trip to our favorite site. On our last (4th) visit, I found some evidence of a forest fire with lots of "burned" roots and wood fossils mixed in with what appears to be grey ash. There is enough there to keep exploring for years - as evidenced by the fact that many of you on the Forum have already been exploring St. Clair for years and it's still producing!

[Fossildude19]

I don't understand the geology of the Newark formations at all and it's hard to find online - the geo maps I checked out suggest this is Triassic. There are several different types of rock in the formation, and trying to understand the distinction is also a challenge...

Michael,

Here is where I can actually help a bit.

Newark supergroup research material is actually very easy to find online.

Google "Newark Supergroup", +"fossils" , "Paul Olsen", "Brian Axsmith", "Pennsylvainia" "Bucks County" "Lockatong Fm." "Triassic fossils Pennsylvania". Don't forget to add "PDF", to get paper results.

Paul Olsen has allot of his papers online for free download. He is a main investigator of the Newark Supergroup. These search terms should yield some decent research material for you for hunting the Triassic fossils of PA.

Good luck with the search, and let me know if you need a hand with this portion of your fossil adventures.

Happy to help out.

Regards,

Edited October 15, 2012 by Fossildude19

[hitekmastr]

Michael,

Here is where I can actually help a bit.

Newark supergroup research material is actually very easy to find online.

Google "Newark Supergroup", +"fossils" , "Paul Olsen", "Brian Axsmith", "Pennsylvainia" "Bucks County" "Lockatong Fm." "Triassic fossils Pennsylvania". Don't forget to add "PDF", to get paper results.

Paul Olsen has allot of his papers online for free download. He is a main investigator of the Newark Supergroup. These search terms should yield some decent research material for you for hunting the Triassic fossils of PA.

Good luck with the search, and let me know if you need a hand with this portion of your fossil adventures.

Happy to help out.

Regards,

GREAT! Exactly what I need!