Tips for hunting mahatango trilobites in Central PA

[flish]

I am new to hunting for Devonian fossils. I've had a little success at a well-known site in Schuylkill County. By little, I mean I found one trilobite. It's got me kind of hooked. 

 

I was talking about this new interest with a family friend who promptly told me that they have property in Perry County and they keep finding "little seashells in rock" in the creek that runs through it. I showed my friend pictures of brachiopods they we're very excited and said that's what they were finding. 

 

I used the app Rockd and indeed their property sits dead in the center of the Mahatango formation. This is very exciting news for me because I've been informed I'm allowed to go whenever I want. 

 

When I was looking at the site in Schuylkill County, it seemed as though people had been there a lot and I was looking through their scraps. That's how I found my trilobite. I don't actually know how to hunt this formation though. I generally surface hunt at Calvert Cliffs for shark teeth and other Marine fossils from the Miocene. The site that I've gone to with Devonian fossils is all of 40 square feet wide. There are no tricks or secrets to hunting there I don't think. 

 

Do you have any advice for me as I try to unlock the mysteries at the site? I have sifters of all kinds and a hammer with a chisel on the back of it that was recommended for hunting Devonian sites. I've never used the chisel to find a fossil though. I'm assuming I'm looking for the gray rock that breaks really easily that I see at my other site but that's all I know to look for. Well that and brachiopods. 

 

Thanks for any and all guidance. 

[FranzBernhard]

Welcome to TFF from Austria!

 

Now you have a fossil site for your own! Congrats!

 

1. Take your time.

2. Examine every rock in the creek, at the banks of the creek and every other rock. Turn every rock around and look closely.

3. This is to get a feeling for the area, the rocks and the potential different fossils.

4. For further proceeding, wait for tips of local members .

Good luck!

Franz Bernhard

 

[Fossildude19]

Pictures of the site would be helpful.

 

 

Splitting rock is different depending on the type of rocks. Some rocks split on nice bedding planes. Others do not.

 

I have personally found that splitting rocks to the smallest possible size exposes some of the best fossils.

 

Good luck.

[Kane]

As recommended above, careful scanning of surfaces and taking advantage of any splittable layers is good advice. That said, studying the formation is also recommended. You can think of it like a layered lasagna where some layers are just ricotta, others noodles, and eventually somewhere along that stack will be the meat. Sometimes these intervals or sequences repeat in a stratigraphic column, and other times they are one-offs. What may be blank at one horizon may be just off an inch from a productive layer. 

 

It is good to understand faunal associations as well. Assuming trilobites died where they lived, they might congregate around other fauna, such as corals or bryozoans that might have acted as shelter or food, just as one would expect to find remains of termites in piles of wood as opposed to sand dunes. Getting a hold of the literature for study can be very helpful in that regard. 

 

One method is to do a kind of top to bottom inspection of each layer to examine a sample from each. If you encounter a cluster of trilobite parts (or even a complete one), or if the layer seems particularly busy, you might flag that for following horizontally. 

 

If there are no in situ layers and you are left with talus, Tim's advice very much holds. Splitting others' splits further can reveal what haste misses. Sometimes it is the case that a recent split reveals nothing but dirt and blobs, but after a while of weathering the trilobite becomes visible. When working with talus, I tend to follow the sequence of surface scan, flip, and split. 

[FossilDAWG]

An advantage of talus is that often the rock splits better with a bit of weathering.  Weaknesses develop along bedding planes and around fossils, allowing the rock to split more easily and reveal fossils.  As an example, I brought home some chunks of mudstone/shale from a known trilobite site in Virginia and left it to "age" outside for about a year.  When fresh, the rock tended to break in conchoidal fractures, often through the fossils.  After it aged for a while, freeze/thaw cycles and wet/dry cycles allowed it to split along bedding planes.  When I picked it up it basically fell into two halves, exposing a surface with seven (!) complete trilobites.

 

Don