Brachiopods. What Conclusions Can I Make?

[eccentric1]

Hi everyone.

Apparently this is a pretty addicting pass time as I went out again this past weekend.

Again I found a few brachiopod specimens. They seem reasonably easy to find by just stream walking in this area. They are tiny but very interesting.

Seems to me that if these tiny brachiopods are easily found in my area (west-central Pa.) that other types of fossils from the same era must be present. Is it safe to conclude that trilobites, other species of larger braciopods and other fossils should certainly exist in the same area? I am afraid that I may have trained my eye to pick out the brachiopod shapes that I keep finding, and may be missing other less obvious shapes in the process.

Or could it be just brachiopods and marine plants in a given area???

Pictured below are a few tiny ones from this weekend.

Thanks for looking. Comments and input appreciated!

e1

[Auspex]

There would have been other members of that community; the question is "did they preserve?". Too, the paleo environment had plenty of time to change, with the cast of critters changing too; a stratigraphic difference of a few feet, or even inches, could bring forth a different assemblage of fossil fauna. Just searching higher or lower in the creek could yield different material. Maybe. It's all up to the rocks to keep or reveal their secrets. You can give yourself an edge (and engage your curiosity on rainy days) by studying whatever you can find about the local geology. The rocks are whispering; we need but learn to listen.

[piranha]

Hi e1,

Thanks for another great post. I will echo what Auspex has suggested. Learning about the stratigraphic time sequences of the area(s) you are hunting will help inestimably. Much can be gleaned just from knowing what county in west central PA you are collecting? Then a search of the literature can produce useful details such as formations and faunal assemblages to expect. Another way in that is often overlooked is networking with the local rock and mineral club. There are always folks within the ranks that are fossil-centric and generally happy to welcome another enthusiastic member to the fold.

[tracer]

ok, here's the secret foramula...

<looks around with beady eyes like a weasel>

"plastics!"

oh dang, forget that - wrong paradigm!

yer stuff looks a bit worn, so look further upstream til you figure where it's comin' from. find it fresh! [that's irony}.

there's really basically seven ways to find fossils. first is to do research, which can often be done for free and easy, and then just go to where your research leads you. second is to find out places from other people who know them. some of those people are here. snort them out and suck up to them until they spill their proadverbial guts. third way is to get on gogol earth and look at aerial photos to spot likely bare spots, like roadcuts, rivers, creeks, new exclamations, and other industrial atrocities of landscapaciousness. then go prowl those, and every other spot in the vicinity or umgebung. you'll eventually find the coolest stuff ever, and i can then take credit for it and brag about knowing you and all. i would say i'd use association with your fame to meet chicks but tj would tell his mom and i'd be skiddin' down the street faster than you can say "dinner's ready", which it is.

good luck.

[Shamalama]

Interesting Fossils. Looks like Devonian to Mississippian in age possibly. If you narrow down your search area (County, town or stream) I can probably tell you more exactly. West Central PA sounds like Mifflin, Huntingdon or Centre counties... or are you closer to Altoona?

It is possible to find Trilobites in any Paleozoic rocks but sometimes they are good hiders. Keep looking and eventually your eye will be able to distinguish more shapes. Tracer is right too, check upstream for an exposure of fresh rock or look in your local roadcuts.

[eccentric1]

Thank you all very much for sharing your experience with me. I am teetering between being a casual fossil finder and really getting into the intricacies of the hobby itself. This forum is certainly tipping the scale toward some serious study in my future. I appreciate it.

Interesting Fossils. Looks like Devonian to Mississippian in age possibly. If you narrow down your search area (County, town or stream) I can probably tell you more exactly. West Central PA sounds like Mifflin, Huntingdon or Centre counties... or are you closer to Altoona?

It is possible to find Trilobites in any Paleozoic rocks but sometimes they are good hiders. Keep looking and eventually your eye will be able to distinguish more shapes. Tracer is right too, check upstream for an exposure of fresh rock or look in your local roadcuts.

Hi Shamalama,

I guess I kind of mislead you on my search area by mixing rose points on you...

It would be more accurate to say central western Pa., namely Mercer County area. Almost into Ohio. I saw a graphic recently that puts the county squarely in a Devonian sea which would explain the things I am finding. I think it would be helpful, as pointed out by the good folks here, to study the geologic timeline specific to my area and then consider the present topography I am dealing with.

Upstream of my most promising area will take some landowner permissions, unfortunately the gift of gab is not my strong suit.

Thanks again all,

e1

[piranha]

Mercer County has three time periods; Pennsylvanian, Mississippian and Devonian.

LINK

Edited April 12, 2011 by piranha

[Fossildude19]

Eccentric1,

You are asking all the right questions, and you are heading in the right directions.

I think it will not take you too long to get the lay of the land there, and figure out what is what.

Just bring the enthusiasm of the hunt to the research table, and all will come together for you.'

Keep posting and keep learning,... you're getting there.

Regards.

[Ordovician_Odyssey]

Hi Eccen

I looked at the peices a bit and it looks like a found a orthoceras...

Looking at this, if it really is a orthocone, i beleive that it is safe to conlcude that trilobites would be found in the area... Seeing in all my previous studies, when orthocones are found, so are trilobites... this is due to predation apon the trilobites. keep looking and you may find a trilo!

[erose]

You need to look for rocks with a different type of preservation as well. Looks like you now have a number of molds in silt or sand stone. In those Devonian seas there were periods when the sea got a bit quieter and less debris (sand & silt) was being washed off the nearby land. When that happened limestones were laid down and in those beds you will find more shell material as well as other critters that needed the clear water to thrive. One suggestion would be to take the drive north up to Penn Dixie on day and see what some of the Devonian stuff up there looks like.

[Shamalama]

Hi Shamalama,

I guess I kind of mislead you on my search area by mixing rose points on you...

It would be more accurate to say central western Pa., namely Mercer County area. Almost into Ohio. I saw a graphic recently that puts the county squarely in a Devonian sea which would explain the things I am finding. I think it would be helpful, as pointed out by the good folks here, to study the geologic timeline specific to my area and then consider the present topography I am dealing with.

Upstream of my most promising area will take some landowner permissions, unfortunately the gift of gab is not my strong suit.

Thanks again all,

e1

Ok, That makes a bit more sense when you say Mercer County. How far from Shenango are you? The rocks out in your area are Devonian in the low valleys to Pennsylvanian as you climb up. They represent the infilling of a basin with sediments from the mountains off to the east that had been formed during the Acadian Orogeny. You'll see a layer cake of shale and sandstone with occasional thin limestone beds that record the variations of sea level over millions of years.

Based on your location and the local stratigraphy I'd say this is the likely description for your rocks:

Berea Sandstone through Venango Formation, undivided - Greenish-yellow and gray sandstone, siltstone, and shale succession, becoming more shaly and more gray downward; bottom of interval is bottom of Panama Conglomerate; Venango not mapped separately because upper key bed (Woodcock Sandstone) is missing. Includes, in descending order: Berea Sandstone, Bedford Shale, Cussewago Sandstone, Riceville Shale, and Venango Formation equivalent; contains marine fossils. Late Devonian in age.

Although you could have some of this too:

Cuyahoga Group - Medium-gray siltstone and dark-gray shale containing interbedded light-gray, flaggy sandstone. Includes, in descending order: Meadville Shale, Sharpsville Sandstone, and Orangeville Shale; marine fossils common. Early Mississippian in age.

Whatever it is, you have a chance to find some nice fossils and I'm sure the Trilo's are there. Good Luck!