Monday, April 30, 2012

Pyncnodonte convexa from the Navesink formation

One of the most common shells that is found within the Navesink formation in New Jersey is Pycnodonte. There are a couple of species with the one I'm showing you today being a Pyncnodonte convexa. It was found at Big Brook near Marlboro, New Jersey in the Navesink formation which is upper Cretaceous (Maastrichtian stage) in age.

Left valve top

Left valve anterior

Left valve, right side profile

Left valve interior

Left valve, left side profile. Note the worm tube that is embedded in the shell.

Left valve posterior

Here are a couple of the right valves which are smaller than the left valve and slightly convex.

Right valve top

Right valve interior

Right valve posterior

Right valve profile

Shells of these oysters are often colonized by epibonts such as sessile worms, sponges and bryozoans. You can see some Bryozoans that have colonized the gaps in the right valve shell below.

Here is a closer view of the worm tube that I indicated above:

Saturday, April 28, 2012

Choristothyris plicata from the Navesink Fm.

Choristothyris plicata is a common brachiopod found in the latest upper Cretaceous sediments (Maastrichtian stage) of the Navesink Formation in New Jersey. I have collected many specimens from the banks of Big Brook near Marlboro, Monmouth County, NJ.

Pedicle valve


Pedicle valve



A very good website for information about the geology of the NJ coastal plain as well as fossils that are found at Big brook is the website.

Thursday, April 26, 2012

Trypanites borings in a Prasopora bryozoan from the Verulam Fm.

While sorting through some fossils from the Verulam formation, in preparation for a display I was putting together for the DVPS show, I found this specimen of Prasopora with boring marks these holes. The holes are indications of a trace fossil called Trypanites. It's fairly common in hard carbonate substrates( like hardgrounds, corals and shells) and is the result of some kind of burrowing animal.

The animal would bore into the carbonate and make it's home there but has not left any other traces of what it was. Possibly it was a boring sponge, like Cliona, or a worm which had no hard parts.

Tuesday, April 24, 2012

Meristina brachiopod from the Keyser limestone

This is a brachiopod I found in an exposure of the Keyser formation called Meristina. It's fairly plain and featureless except for the sulcus.

Pedicle valve


Brachial valve (weathered)



The portion of the Keyser formation that I found this in is thin beds that are fairly shelly but have lots of complete specimens. This would indicate to me that it was a low energy reef like environment. Interestingly enough there are few bryozoans, coral or stromatoporids, which are typically the reef builders, in the same layer. So far I've not found any brachiopods in life position so it could represent a "pavement" or sorts that was periodically buried.

Sunday, April 22, 2012

Eccentricosta from the Keyser formation

At one locality where I collect from the Keyser formation I've found an interesting brachiopod called Eccentricosta. That name is was created in 1963 as a way of moving fossils called Chonetes jerseyensis into it's own genus away from Chonetes. This was done due to significant differences in some of the shell anatomy such that it deserved it's own genus. There is a paper that explains how and why this was done available from

Now onto the specimens! The shells that I have found all have been partially buried in the rock. This first specimen I cleaned off with a wire brush to expose it more. I can't tell if it's a pedicle or brachial valve though. The most telling feature are the radial ribs that decorate the surface.

Specimen #2

Specimen #3

Specimen #4

These fossils are fairly rare though as I read reports about the Keyser formation there is mention of zones that are traced via this fossil. I'm still learning how that works but I think faunal zones are designated by somewhat rare or unusual fossils.

Friday, April 20, 2012

Micro fossils in the North Evans Limestone

 After photographing the fossil wood from the North Evans Limestone (NEL) I took a closer look with my Zorb microscope/camera. The NEL is composed of fossil fragments that eroded out of Hamilton group and Genesse formation rocks right at the boundary between the middle and upper Devonian epochs. I'd read that fish teeth and bone fragments could be found within it along with conodonts and scolecodonts which are teeth and jaws from soft bodied animals (eel like vertebrates for the former and annelid worms for the latter). Below are pictures of some of what I found. Please note that the area shown in each picture is approximately 9mm across.

These are fragments of bone or placoderm armor that show rounded edges which is a clear indication of tumbling or reworking by waves.

This one is stained by pyrite as it was close to a piece of fossilized wood.

Conodont/Scolecodont teeth

Fish teeth

This last picture is of a shark tooth that is from Wellerodus wellsi.
Special thanks go out to Karl Wilson, who's website New York Paleontology I frequent regularly, for helping me ID this fossil. He sent me a paper by Susan Turner entitled "'DITTODUS' SPECIES OF EASTMAN 1899 AND HUSSAKOF AND BRYANT 1918 (MID TO LATE DEVONIAN)" Modern Geology, 1997, Vol. 21, pp. 87-119. In the paper she condenses some different genera into the single genus of Welleodus.

Karl's website has some pics of the many micro fossils that can be found in the NEL here.

Wednesday, April 18, 2012

Devonian aged Fossil wood from the North Evans Limestone

While visiting 18 mile creek south of Buffalo, NY I've found some thin slabs of limestone from the Genesse formation which are from a layer called the North Evans Limestone. The layer has been interpreted as a lag bed resulting from concentration of eroded material from Hamilton group and Genesse formation rocks. It only occurs in western New York in Erie county over a limited area. The the deposit is right at the boundary between the middle and upper Devonian (Givetian to Frasnian stages).

I was attracted by reports that I'd read indicating that fossilized wood could be found in this layer somewhat frequently. So far I have found several piece of small logs or branches that are carbonized and partially replaced by pyrite. It's fairly easy to spot pieces of limestone that have the wood within as you will see red streaks where the pyrite is weathering away.

This is a typical piece with a small branch.

A closeup reveals a cracked or crazed appearance similar to how some pottery glazes look. The white "veins" are calcite that has filled in the space.

This is a larger piece and even shows some minor coal.

A closeup of the coal.

I've found the best way to expose the wood is to try and split the slab of limestone where you see the red pyrite streaks. In the next post I'll show you some of the micro fossils that can be found in the limestone.

Monday, April 16, 2012

Lewistown Narrows roadcut

Along the route of US 322 in Juniata County, PA is a roadcut that exposes a neat fold in the rocks. It's called the Lewistown Narrows and is near the town of Macedonia. The project, started in 2004 and completed four years later, was designed to build a four lane section of road to replace the aging, crowded and dangerous (it was once in the top ten most dangerous sections of roadway in the nation) original two lane road. As part of the project a new cut through what is essentially the toe of Blue Mountain was made. This exposed a beautiful layer cake of the Turscarora formation with a little bit of Rose Hill formation on the side.

Here is a view of the western end of the cut. Remember to click on the picture to see the full view.

And here is a view of the center of the cut with beautiful stair step folds..

This is a closer view of the easternmost portion of the cut. The folding here is a little more complex.

The last pic shows some of the Tuscarora formation and the start of the Rose Hill formation. The Rose Hill formation is an olive to brown colored shale with thin beds of red to brown sandstone.

This is a geologic map view of the Narrows that I created with Google Earth and overlay files from the USGS website HERE. It looks as though the cut should be through a typical arch shaped anticline (the Blue Mountain anticline) but in reality it is not that simple .

Here is the same map but with the formations noted.

A regional view provides an even more complex picture. The thumbtack is the Lewistown Narrows. This area is right in the middle of the "bend" in the Appalachian mountains where the somewhat east to west trend turns and heads south-southwest.

This portion of the state is very tightly folded and you can see how the Juniata river follows the valley between the two ridges.

As for fossils, you can find some in the Rose Hill formation but the Tuscarora formation is fairly barren. The only fossils I've found in it are trace fossils like the Paleophycus below.

Paleophycus is a type of burrow that has been ascribed to a worm and is only found in the gray shaly layers between the white to tan colored sandstone layers. The sandstone likely represents a beach environment with the shale layers being temporary mud flats that formed as the sea level fluctuated.

The Tuscarora and Rose Hill formations are Silurian in age and range from the Llandovery to Wenlock epochs (Telychian to Sheinwoodian stages). The particular moment in time that this cut represents is the very latest Telychian stage. Below is a stratigraphic chart from the PA Geological Survey website HERE.

In comparison to other Silurian localities I've collected at, the Waldron Shale is about the same age as the Rochester shale of New York and they are considered to be Sheinwoodian in age; The Irondequoit limestone underlies the Rochester shale and is just above the Rose Hill shales in the Sheinwoodian stage; The Keyser formation is at the very top of the Silurian grading into the Devonian.