Excavating for fossils

[Rocky Stoner]

Hi Folks.

I have found over a hundred of these in a relatively small area. Basically, in my yard and garden.

I recently tilled a neighboring section up the ridge about 30' X 40' to look for more arrowheads and such. Found 2 arrowheads after the first rain, and maybe 20 of the fossils.

There is only a few inches of top soil, then there is soft yellow shale several feet deep in places. I drilled some 40" deep holes for a pole building by the garden and it was all the soft shale. The artifacts are of course in the top soil but my plow cuts into the shale several inches and I think this is where it exposes the fossils.

Couple questions:

Are these fossils already in pieces, or am I breaking them up with the plowing and tilling ?

Would I benefit from doing a "dig" of sorts in an effort to find more intact specimens ?

Also, is there a likelihood that they are all near the surface, or are they probably at any / all depths ?

Is so, how would I go about it with no machinery other than a small tractor with a plow ?

I'm in eastern WV at about 900 ft elevation on a small spur ridge near the base of a 3000 ft mountain in the Appalachian chain. (if that helps)

I'd really like to find more complete specimens, but am guessing they were all broken up long ago .... way before they got up here.

Thanks for looking.

Kind regards.

 

[ynot]

It is hard to say whether they are in the topsoil or the shale. The only way to know for sure is to do some excavation of the material.

Scrape off the topsoil in an area and do a more careful dig to see if You find any inside the shale.

You never know if You do not look.

You can check geologic maps of the area to identify the formation and age of Your finds.

[Kane]

Speaking of maps, here is a relatively simplified one of WV (there is a far more detailed one available, but this may serve its purpose for now).

[Rocky Stoner]

Thank you both for the info.

I'm going to mark off an untouched 10' x 10' area and methodically dissect it screening the topsoil for artifacts then carefully separating the shale in search of fossils. Will be a neat summer project.

 

Here are pics of another find here. It was found on the surface of tilled ground after a rain. I was surprised to find it "intact" and totally separate from the shale.

Brachiopod ?

 

[abyssunder]

Yes, it's a brachiopod.

[Ludwigia]

spiriferid brachiopod.

[Kane]

So when you match where you are situated and that map, what age comes up? It is looking so far that, for sure, you have Paleozoic deposits. Drilling down a bit more, you may be in the Devonian? This will really help you in terms of what you might expect to find as you excavate.  

 

And feel free to post pictures of your excavation in progress; it will be like we are on a vicarious dig.

[Rocky Stoner]

Hi Kane, I looked at several maps, then got confused with all of the formations but determined that it is Devonian in this area.

 

We had a little rain last night and this morning. I went to lay out my "dig" and this fellow caught my eye where I last tilled.

All I saw was a smooth arch protruding out of the dirt about the size of a pea. I was surprised after cleaning it up as it looks like a claw. Perfectly symmetrical and slick as a whistle. It has a cavity in the center just like modern critters.

I hope the attached pics do it justice.

Any idea what it might be ?

Thanks again Kane

[Kane]

Hm... This might be a goniatite. The curvature seems to suggest ammonoid. This is turning into an interesting detective story!

[Rocky Stoner]

I Wikied that ... and agree, thanks !

I believe I can see very faint remnants of (possibly) some of the zigzag sutures.

I'll keep you posted.

Kindest regards.

[Ludwigia]

+1 for goniatite.

[Rocky Stoner]

Hi Folks,

 I dug a small test pit about 3' x 5'.

The topsoil layer was +/-5" ... found no artifacts or fossils.

Then there is a +/-2" transition into the soft yellow shale, fractured but still generally in place. Found 3 pieces of the cephalopods.

I went down another foot or so and found nothing but layered shale, fairly easy to dig by prying out the layers with no sign of fossils.

Then I plowed that area (30' x 30') about 6" deep and found the cephs' in the first pic (after a rain).

At this point, it looks like they are in that transition layer and none of the breaks appear to be fresh so I suppose they were all broken up long ago. 

I'm anxious to till this patch several times between the rains and see what washes out.

 

While I was plowing, I went to the other end of my yard and plowed another "new" patch about 20' x 30'.

This area is much different. About 3" of topsoil, then into a much harder bluish shale that has many, many fossils. ( and a yellow jacket nest)

The attached attempts to show some them. Its almost a solid mass of critters.

 

If anyone (US) would like to have the chunk of shale in the pic to dissect, Id be happy to send it to you if you pay the postage.

I'd be interested in the discoveries of more experienced hands and eyes than mine.

 

Thanks.

 

 

[Kane]

This is quite exciting. I'm seeing a lot of familiar Paleozoic fossils in these. I hope you have something to pump out water from those areas! I would say continue down a bit further in a test area and index as you go; you are already finding that some layers are more productive than others, and that you might be able to follow them horizontally - or follow the layer however it may undulate. The difference of layers between two holes at equal depths might be explained by the sloping of the strata. Keep it up and keep posting the results of this dig!

[Miocene_Mason]

If you ID some of the fossils, some could be used to date specifically and find the specific formation.

[Rocky Stoner]

This USGS map shows me at the attached formation.

https://ngmdb.usgs.gov/Prodesc/proddesc_78332.htm

 

Thanks.

 

[Kane]

One of our members ( @Shamalama) maintains an excellent blog that features a lot of fossils from the Mahantango Formation. His finds - and associated pictures - are very good, and I've visited it on several occasions to identify some of my finds in places where I've collected that he has been to.

 

http://viewsofthemahantango.blogspot.ca/p/mahantango-formation-fossils.html

[Rocky Stoner]

Thanks for the link Kane.

One example I do not see there though is the cephalopods.

The geology here is hard to understand by a novice (or lesser).

Nothing I see describes the chalk like soft yellow shale that is in one spot (50' radius) on this ridge.

Above this, the ridge turns to chert and below it is the hard shale.

 

Anyway, I found the attached today.

Encouraging to find the one larger radiussed section. I measured it with radius gauges and found it is a section of a perfect conical shape with the smaller end being 1-1/4" diameter and the larger end 1-1/2" .

If this is part of the living chamber of a ceph', it would be the largest I've found ... by far.

The other one in the pic clearly shows the septum lines and measures 7/8" diameter.

 

Also, a couple more concretions, one really nice one.

 

Kind regards,

 

[ynot]

2 hours ago, Rocky Stoner said:

Nothing I see describes the chalk like soft yellow shale that is in one spot (50' radius) on this ridge.

Above this, the ridge turns to chert and below it is the hard shale.

The "soft yellow shale" could be partially decomposed shale.

Chert is not a bedrock type stone. It forms in nodules and concretions within other types of rock.

[Miocene_Mason]

10 hours ago, Rocky Stoner said:

This USGS map shows me at the attached formation.

https://ngmdb.usgs.gov/Prodesc/proddesc_78332.htm

 

Thanks.

 

That's what I thought, I have collected from this formation near Hancock, Maryland (not too far from you) but there are vast differences in the ecosystem. I haven't yet found a nautiloid or even a bryzoan. No spiniferids either up here. Soft yellow is just slightly eroded so it's muddied up a bit, the lower is darker because it doesn't face eroding forces, At least that's how it is when in Maryland.

[Rocky Stoner]

1 hour ago, ynot said:

The "soft yellow shale" could be partially decomposed shale.

That does make sense to me. But, for 200 meters along this ridge that I'm on, on one end where I dug the foundation for my house I hit extremely hard shale at about 12 to 16". Almost had to blast to get the footings in. Then at the other end where I built my barn we drilled with a 24" auger down over 4' in one spot and never did hit anything other than the yellow stuff. I understand the aging / weathering of the shale but do not understand the depth variation over such a small distance.

1 hour ago, ynot said:

Chert is not a bedrock type stone. It forms in nodules and concretions within other types of rock.

I did not realize that. Perhaps I am referring to limestone of sorts.

There is a mountain near me called Chert Mtn. that is primarily very hard whitish gray rubble at the surface. The locals call it chert rock. Quoting the lyrics of a popular song by the group Alabama, "Playing baseball with chert rocks" never made sense to me till now if chert concretions are common down south. I never could imagine playing ball with what we have here. These are more or less cubic, like dice, bricks and blocks.

I need to research "chert" a bit more for a better understanding.

 

Thanks MUCH !

[Rocky Stoner]

13 minutes ago, WhodamanHD said:

That's what I thought, I have collected from this formation near Hancock, Maryland (not too far from you) but there are vast differences in the ecosystem. I haven't yet found a nautiloid or even a bryzoan. No spiniferids either up here. Soft yellow is just slightly eroded so it's muddied up a bit, the lower is darker because it doesn't face eroding forces, At least that's how it is when in Maryland.

Yes, very diverse.

I find many, MANY fossils in the hard shale, but never a cephalopod like found here in the degraded shale.

Just had a thought. If: the shale degrades from weathering, freezing/thawing, fracturing, roots, silt, mud, dirt and the "hump" I refer to on the ridge was MORE fractured from localized uplift, the shale in that area might have degraded to a greater depth than further down the ridge where it is flatter ? ? ? Plausible ?

Thanks for the input.

[Miocene_Mason]

21 minutes ago, Rocky Stoner said:

Yes, very diverse.

I find many, MANY fossils in the hard shale, but never a cephalopod like found here in the degraded shale.

Just had a thought. If: the shale degrades from weathering, freezing/thawing, fracturing, roots, silt, mud, dirt and the "hump" I refer to on the ridge was MORE fractured from localized uplift, the shale in that area might have degraded to a greater depth than further down the ridge where it is flatter ? ? ? Plausible ?

Thanks for the input.

I would think that it's possible, raised land often erodes quicker than flat land, due to thinner layers of sediment. Many other factors could be at play though, and I'm no expert.

[ynot]

34 minutes ago, Rocky Stoner said:

. If: the shale degrades from weathering, freezing/thawing, fracturing, roots, silt, mud, dirt and the "hump" I refer to on the ridge was MORE fractured from localized uplift, the shale in that area might have degraded to a greater depth than further down the ridge where it is flatter

I think You got it (mostly).

There is also infusion from groundwater, which can be very acidic or mineral rich. It can remove or add minerals to the bedrock.

This type of action typically follows fault structures.

Now take all of that and spread it over 100 million years or more.

[Rocky Stoner]

4 hours ago, ynot said:

Chert is not a bedrock type stone. It forms in nodules and concretions within other types of rock.

Hi ynot,

I see that chert is also described as what I have here as "layered deposits".

http://geology.com/rocks/chert.shtml

 

Also, many of the arrowheads and other tools found here are of the chert described in the link. I have found hundreds of small razor sharp "chips" of chert in a relatively small area which was determined by a local authority to be where flint (chert) knapping was regularly done in the making of arrowheads and other tools. I also found 20+ arrowheads here in the yard and garden.

There are many fossils in the chert up on the mountain, next time I go up there, I will bring some back.

 

Thanks again.

 

[ynot]

23 minutes ago, Rocky Stoner said:

Hi ynot,

I see that chert is also described as what I have here as "layered deposits".

http://geology.com/rocks/chert.shtml

 

Also, many of the arrowheads and other tools found here are of the chert described in the link. I have found hundreds of small razor sharp "chips" of chert in a relatively small area which was determined by a local authority to be where flint (chert) knapping was regularly done in the making of arrowheads and other tools. I also found 20+ arrowheads here in the yard and garden.

There are many fossils in the chert up on the mountain, next time I go up there, I will bring some back.

 

Thanks again.

 

Should have added a qualifier. I have never heard of "chert" as a solid bedrock forming type stone. I have heard of quartzite being improperly called chert.

There are many cryptocrystalline quartz rocks-- chert, flint, agate, chalidone,jasper etc. All can be suitable for knapping.