Deer Lake Trilobite And Other Devonian Finds

[hitekmastr]

A Quick Trip to Deer Lake

Nan and I spent half a day at Deer Lake which is still beautifully exposed by the highway construction with lots of rock facings, rubble piles and exposed walls, also large rocks and boulders. There is a lot of iron content in the shale below the "Tully limestone" strata which is near the top and just below the limestone there are Dipleura trilobites although we have found mostly body parts and segments.

I also noticed that a lot of the assemblages include shells and other creatures were already dead when they were fossilized. Many of the shells in large assemblages are different types of brachiopods/pelecypods with holes in the shells suggesting they died and accumulated like shells do today at ocean shorelines, then were fossilized. Some clusters where all or most of the species are the same with no deterioration or predation suggest that they died together at the same time.

Students and fossil hounds have been scouring this area but there is a lot more to find and more being revealed as the construction continues. Nan and I have had pretty good luck this year with construction sites - most notably of course the Wattieza tree stumps we discovered.

We do have some questions about some of our Deer Lake finds - comments welcome:

1. Trilobites

We only found 2 trilobites this trip - this one is curled under at the bottom which is shown in these views:

2. Crinoids

These are some interesting crinoids:

3. Pleurodictyum Coral Patterns - (Not Clam Mold Patterns)

I thought these strange patterns were in the mold of a clam - there are tons of clam fossils at Deer Lake, some fairly large. These patterns were in a mold but apparently this is from a coral.

4. Spaghetti Shaped Fossils

And finally - here are some "spaghetti strands" Nan was wondering about - not sure what these are:

We found a LOT more fossils, including some assemblages that will make some nice displays. We were looking for larger pieces for display and found one large shell covered rock that is almost 2 feet long.

Edited September 1, 2013 by hitekmastr

[lmacfadden]

Really awesome finds!!

[fossilcrazy]

#3 Clam mold patterns would be Pleurodictyum corals that dissolved away leaving that pattern. Pleurodictyum Corals frequently lived as epibionts and grew on shells.

If you Google image Pleurodictyum you will see your pattern soon.

#2 Crinoids has some interesting Cirri (side arm) marks that were left when they disarticulated leaving a scar on the main "stem". I don't see that very often.

[Ridgehiker]

Thanks for sharing. Never seen that pattern on a crinoid. Almost like stacked bottle caps.

Yes, construction sites are worth checking out. A few meters of new exposure could potentially yield some incredible material.

Funny aside...when I read 'Deer Lake' a lake in Newfoundland came to mind. There are 3 million lakes in Canada....but only about a 180 thousand or 1 in 16 have a name. There are 1100 Official Deer Lakes. If all lakes were eventually named and the ratio stayed the same there would be about 18,000 'Deer Lakes'. Canadians lack imagination when naming lakes.

Edited August 31, 2013 by Ridgehiker

[hitekmastr]

I posted the crinoid showing that arrangement of holes around the perimeter of the stem because it struck me as unusual - so I really appreciate the explanation about the cirri.

The coral patterns are also fascinating to learn about.

Deer Lake is Deer Lake, Pennsylvania, but I know there are hundreds or thousands of Deer Lakes in the U.S. and Canada...

Thanks for the speedy explanations...

[squalicorax]

That articulated Dipleura is aweseome!

[snakebite6769]

Great finds, the dipleura is still on my list to find complete, lol. I will be at deer lake Monday

[hitekmastr]

Snakebite... Good luck at Deer Lake. The construction is extensive since they are extending the bypass. We could see that a lot of fossil hunters have already been scouring the site, even as large as it is - which is why we concentrated on some specific goals. We found one Dipleura earlier this year in a "wall" there and the Dipleura pictured here was found by my eagle-eye wife in the rubble! It is the most complete Dipleura we've found.

There are tons of rubble at this site, by the way. The shale has a very high iron content so it is very hard to split or fragment but that's ok because most of the fossils are visible on the surface of the rocks. There are also some very cool looking shell assemblages on olive green shale which makes the nicest displays, I think.

Here is a picture I took today after cleaning our "shell" finds - we were looking for display-worthy pieces in addition to anything that looked out of the ordinary. Here is one medium rock - are the segmented snakey looking tubes open crinoid stems or something else?

Here below is a "group shot" of my shell assemblage finds - I collected most of these (Nan is not a "shell enthusiast" - she prefers to look for trilobites) although some of these rocks have Dipleura segments on them:

I also have a 2 foot long piece that I will post in separate thread - I show the steps I took to "clean" the large piece although there is a lot of detail work remaining. Took some photos today and will post tomorrow, maybe in the "new collectors" section.

Have fun tomorrow - can't wait to see what you find!

Edited September 2, 2013 by hitekmastr

[hitekmastr]

More Deer Lake Fossils

Since there seems to be some interest, here are some closeups of the medium pieces in the previous "group shot" - interesting density and patterns. Some of these indicate that the creatures died together while still alive, and others show an assemblage that suggests they were dead when fossilized. The variety always amazes me:

Edited September 2, 2013 by hitekmastr

[MarleysGh0st]

This one is a bivalve called Orthonota undulata. It really makes a distinctive pattern when you find both valves together, as in this specimen!

Devonian Shell 1 Deer Lake PA.jpg

[hitekmastr]

We've found quite a few Orthonata fossils in the past but never one that has both halves. These are only a few representative examples of our finds - this site is only an hour from our home so we plan to revisit the site this Fall.

[Suvi]

Your photos are amazing!!

[snakebite6769]

You were very correct in the amount of work that has been done, pretty crazy!

She has an eye for those rubble finds! I was only there for a little bit because I had to go to another place I found, I did manage to find a few trilobites and some other really neat items, like a partially pyritized group of shells. I will be posting more in the forum I started yesterday. With plenty of pictures.