This specimen was found near Napoleon, IN and is from rocks deposited during the Silurian (Telychian to Sheinwoodian stage).
My friend Nathan found a larger and more complete specimen of Phragmoceras in his local Racine formation of Wisconsin.
Monday, August 20, 2012
Phragmoceras cephalopod from the Osgood Shale
Phragmoceras is a rare fossil that I found in the Osgood shale. It's a nautiloid (cephalopod ) that has a slightly curved shell. The fossil I found is only a partial but the shell decoration is still evident.
This specimen was found near Napoleon, IN and is from rocks deposited during the Silurian (Telychian to Sheinwoodian stage).
My friend Nathan found a larger and more complete specimen of Phragmoceras in his local Racine formation of Wisconsin.
This specimen was found near Napoleon, IN and is from rocks deposited during the Silurian (Telychian to Sheinwoodian stage).
My friend Nathan found a larger and more complete specimen of Phragmoceras in his local Racine formation of Wisconsin.
Saturday, August 18, 2012
Additional fossils from Lusters Gate
I wrote the previous post several months after I had visited the site near Lusters Gate northeast of Blacksburg, VA. Just a week ago I was breaking apart some of the shale that I had brought back with me and found a few more fossils.
The first fossil I found was this snail. It's pretty tiny and not well preserved so I don't think I will be able to positively ID it.
The next fossil is a internal mold of a brachiopod. Again, the fossil is so small and in poor condition.
This is a cephalon from a trilobite (which is what I wanted to find when I went to the site in the first place).
The trilobite is likely a Ampyxina powelli (Raymond, 1920) as ID'd by the helpful members of the Fossil Forum.
The above specimens came from a roadcut along Route 785 near Lusters Gate, Montgomery county, Virginia. The cut is listed as site #2 in the book "Fossil Collecting in the Mid-Atlantic States" by Jasper Burns. The Liberty Hall formation is dated to the middle Ordovician Mohawkian stage and is roughly equivalent to the Shippensburg and Chambersburg Limestones in PA. It is below the Lexington Limestone of Kentucky and is considered a part of the Black River-Trenton group in NY and Ontario.
The first fossil I found was this snail. It's pretty tiny and not well preserved so I don't think I will be able to positively ID it.
The next fossil is a internal mold of a brachiopod. Again, the fossil is so small and in poor condition.
This is a cephalon from a trilobite (which is what I wanted to find when I went to the site in the first place).
The above specimens came from a roadcut along Route 785 near Lusters Gate, Montgomery county, Virginia. The cut is listed as site #2 in the book "Fossil Collecting in the Mid-Atlantic States" by Jasper Burns. The Liberty Hall formation is dated to the middle Ordovician Mohawkian stage and is roughly equivalent to the Shippensburg and Chambersburg Limestones in PA. It is below the Lexington Limestone of Kentucky and is considered a part of the Black River-Trenton group in NY and Ontario.
Tuesday, August 14, 2012
Fossils from Lusters Gate, VA.
This past April I took a trip through Virginia and West Virginia exploring some sites that were listed in the book "Fossil Collecting in the Mid-Atlantic States" by Jasper Burns. One of the sites came with a recommendation from a couple of friends on the Fossil Forum. It is a roadcut northeast of Blackburg, VA near the village of Lusters Gate. Below is a view of the roadcut which you can see is very overgrown.
This shows the most obvious exposure of shale and also evidence of collecting by others. I spent about half a hour picking at the rocks looking for any of the trilobites that are known to be found here.
I didn't have much luck with the Trilobites but I did find some Climatograptus sp. graptolites on some of the bedding planes. Graptolites are primite animals that formed colonial structures similar to coral and bryozoan but they often floated in the currents rather than cement themselves to a substrate. They are found primarily in the lower Paleozoic but survived until the middle carboniferous.
This rock is interesting in that it has a large number of the graptolite fossils but also some stringy looking traces. Perhaps they were part of a large colony that was held together by the "strings".
Graptolites are hemichordates which means they have a primitive tube with nerves for part of their lives. It's thought that they are a connection between vertebrates and invertebrates (more specifically echinoderms) and came from a similar common ancestor. (Wikipedia)
The above specimens came from a roadcut along Route 785 near Lusters Gate, Montgomery county, Virginia. The cut is listed as site #2 in the book "Fossil Collecting in the Mid-Atlantic States" by Jasper Burns. The Liberty Hall formation is dated to the middle Ordovician Mohawkian stage and is roughly equivalent to the Shippensburg and Chambersburg Limestones in PA. It is below the Lexington Limestone of Kentucky and is considered a part of the Black River-Trenton group in NY and Ontario.
This shows the most obvious exposure of shale and also evidence of collecting by others. I spent about half a hour picking at the rocks looking for any of the trilobites that are known to be found here.
I didn't have much luck with the Trilobites but I did find some Climatograptus sp. graptolites on some of the bedding planes. Graptolites are primite animals that formed colonial structures similar to coral and bryozoan but they often floated in the currents rather than cement themselves to a substrate. They are found primarily in the lower Paleozoic but survived until the middle carboniferous.
This rock is interesting in that it has a large number of the graptolite fossils but also some stringy looking traces. Perhaps they were part of a large colony that was held together by the "strings".
Graptolites are hemichordates which means they have a primitive tube with nerves for part of their lives. It's thought that they are a connection between vertebrates and invertebrates (more specifically echinoderms) and came from a similar common ancestor. (Wikipedia)
The above specimens came from a roadcut along Route 785 near Lusters Gate, Montgomery county, Virginia. The cut is listed as site #2 in the book "Fossil Collecting in the Mid-Atlantic States" by Jasper Burns. The Liberty Hall formation is dated to the middle Ordovician Mohawkian stage and is roughly equivalent to the Shippensburg and Chambersburg Limestones in PA. It is below the Lexington Limestone of Kentucky and is considered a part of the Black River-Trenton group in NY and Ontario.
Sunday, August 12, 2012
Marcellus shale Crinoids
This past April I took a trip through Virginia and West Virginia exploring some sites that were listed in the book "Fossil Collecting in the Mid-Atlantic States" by Jasper Burns. This is an old shale pit that exposed some Marcellus formation rocks in Maryland.
The Marcellus shale is not know for it's fossils as it was a deep water black shale formed in anoxic conditions. It's more commonly known for being the rock formation that all the natural gas drillers in the NE are trying to "frack". However this site does happen to have some notable fossils of, surprisingly, Crinoids. Intact and articulated Crinoids. I spent about a hour searching the site and fossils can be found but they are very isolated and difficult to locate.
An isolated arm with pinnules.
More arms
I think there may be a calyx hidden where this three arms disappear into the rock.
This piece definitely has a calyx (on the right side of the slab) but the preservation is not good enough for an ID.
The only other fossil I found besides Crinoids were these occasional productid brachiopods.
I came across this specimen at a fossil show back in March that I think is from the same locality. I think it's an Arthroacantha similar to this specimen from the Silica Shale in Ohio. It's a nice piece to compare with what I found at the site myself and to tempt me to go back again.
I would be interested in learning more about this paleoecology of this site and how articulate crinoids came to be preserved here. Did they colonize the substrate when oxygen levels were higher only to succumb when the dropped again? Were they "blown" in by storm currents? Were they attached to floating debris but dropped off? Whatever the case it's a rare thing to find any parts of a crinoid articualted so I will be back to this site again in the future.
I came across this specimen at a fossil show back in March that I think is from the same locality. It's a nice piece to compare with what I found.
The above specimen came from an old quarry near Big Spring in Washington county, Maryland. The cut is listed as site #21 in the book "Fossil Collecting in the Mid-Atlantic States" by Jasper Burns. The Marcellus formation is part of the Givetian stage of the middle Devonian.
The Marcellus shale is not know for it's fossils as it was a deep water black shale formed in anoxic conditions. It's more commonly known for being the rock formation that all the natural gas drillers in the NE are trying to "frack". However this site does happen to have some notable fossils of, surprisingly, Crinoids. Intact and articulated Crinoids. I spent about a hour searching the site and fossils can be found but they are very isolated and difficult to locate.
An isolated arm with pinnules.
More arms
I think there may be a calyx hidden where this three arms disappear into the rock.
This piece definitely has a calyx (on the right side of the slab) but the preservation is not good enough for an ID.
The only other fossil I found besides Crinoids were these occasional productid brachiopods.
I came across this specimen at a fossil show back in March that I think is from the same locality. I think it's an Arthroacantha similar to this specimen from the Silica Shale in Ohio. It's a nice piece to compare with what I found at the site myself and to tempt me to go back again.
I would be interested in learning more about this paleoecology of this site and how articulate crinoids came to be preserved here. Did they colonize the substrate when oxygen levels were higher only to succumb when the dropped again? Were they "blown" in by storm currents? Were they attached to floating debris but dropped off? Whatever the case it's a rare thing to find any parts of a crinoid articualted so I will be back to this site again in the future.
I came across this specimen at a fossil show back in March that I think is from the same locality. It's a nice piece to compare with what I found.
The above specimen came from an old quarry near Big Spring in Washington county, Maryland. The cut is listed as site #21 in the book "Fossil Collecting in the Mid-Atlantic States" by Jasper Burns. The Marcellus formation is part of the Givetian stage of the middle Devonian.
Friday, August 10, 2012
Germany Valley overlook
This past April I took a trip through Virginia and West Virginia exploring some sites that were listed in the book "Fossil Collecting in the Mid-Atlantic States" by Jasper Burns. In my previous post I showed you some fossils from a roadcut into the Reedsville formation. Across from that roadcut, where I parked my car, is a pull off for an overlook of the Germany Valley. Below is a panorama of the view looking north with east to the right.
I found this view to be both peaceful and intriguing as it shows a couple of classic geologic features. The first thing I noticed was that the ridge line on the east side seemed to have, at one time, crossed the valley and dipped down. This meant that I was looking at an Anticline which is an "A" shaped fold of rocks which, in this case, was folded in an east-west direction. Not only was this an anticline but much of the rock had been eroded out of the middle and so it could be called a breached anticline. Something else I noticed about the geology was that this was a plunging anticline meaning the folded rock was bent again in another direction (this time north to south) like a dolphins back rising out of the water. Lets look at this from a higher angle with a Google earth map that has the topography exaggerated to better see the ridge lines.
And this is my interpretation of how the fold would have looked prior to the breach and erosion of the center.
Note that you can see at the north end of the valley how the valley closes in on itself and the ridgelines meet. This is the evidence for the plunging anticline. Below is a geologic map of the valley from Google Earth. I've picked out the two resistant rock layers that are the cause for the ridges; the Juniata formation and the Tuscarora formation. Both are hard sandstones that resist weathering more than the softer shales and limestones that make up the valley. You can see by the colors distinguishing different layers that the rocks are folded and repeat on each side of the valley.
Here is an excerpt from this James Madison University field trip guide to the same location:
Once you've taken in the scenery and geology of the view there are a couple of signs which tell of some historical events that occurred in the valley.
I found this view to be both peaceful and intriguing as it shows a couple of classic geologic features. The first thing I noticed was that the ridge line on the east side seemed to have, at one time, crossed the valley and dipped down. This meant that I was looking at an Anticline which is an "A" shaped fold of rocks which, in this case, was folded in an east-west direction. Not only was this an anticline but much of the rock had been eroded out of the middle and so it could be called a breached anticline. Something else I noticed about the geology was that this was a plunging anticline meaning the folded rock was bent again in another direction (this time north to south) like a dolphins back rising out of the water. Lets look at this from a higher angle with a Google earth map that has the topography exaggerated to better see the ridge lines.
And this is my interpretation of how the fold would have looked prior to the breach and erosion of the center.
Note that you can see at the north end of the valley how the valley closes in on itself and the ridgelines meet. This is the evidence for the plunging anticline. Below is a geologic map of the valley from Google Earth. I've picked out the two resistant rock layers that are the cause for the ridges; the Juniata formation and the Tuscarora formation. Both are hard sandstones that resist weathering more than the softer shales and limestones that make up the valley. You can see by the colors distinguishing different layers that the rocks are folded and repeat on each side of the valley.
Here is an excerpt from this James Madison University field trip guide to the same location:
At the overlook you can observe Germany Valley (Ordovician limestones at the culmination of the Wills Mountain anticline); the ridge crest of North Fork Mountain (Tuscarora Sandstone on the east limb of Wills Mountain anticline) to the east; and River Knobs (Tuscarora Sandstone on the west limb of Wills Mountain anticline), which also form the first set of "razorback" hills or ridges to the west. At the northeast end of Germany Valley the Tuscarora ridge forms a spectacular example of closure at the nose of the plunging anticline.
Once you've taken in the scenery and geology of the view there are a couple of signs which tell of some historical events that occurred in the valley.
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