Posts Tagged ‘crinoid’

Sponge Encrusting Worm Tube Encrusting Bryzoa

June 10, 2010

At a crinoid garden that I have been working for a couple of years, I found this curious example of an epibiont on an epibiont.

First, a trepostomate bryozoan found its home, then some cornulites worm tubes found the bryozoan inviting.

Finally, the sponge.

When it was alive, it had to have been pretty cool looking with the worms sticking out of the sponge.

Width of photo about 3cm

Mag x10

You know the scale

Since, it was found at one of my crinoid “gardens”, here is a double from the same locality. I have pulled about 50 crinoids from this site(too lazy to check my notebook), and the Archaeocrinus sp. out number Pychnocrinus sp. by a substantial majority(again, too lazy to check my notebook), So these are probably Archaeocrinus sp.

Many of the crinoids at this site appear to be weathered, but they are from fresh exposures??? They are found in a thin lens of mudstone within a calcarenite/calcirudite. They are early Late Ordovician. Some researchers postulate that the abrupt changes in facies in the Central Kentucky region is due to weird structural crap associated with tensional forces at the close of the Taconic Orogeny to the east.

So, that leaves me wondering… were these critters left high and dry in their shallow lagoon/inlet by a regression, and then covered by a transgression??? It seems plausible. They could have laid there for months, or longer, since there were no land critters to pick at the carapaces.

Do you have another scenario??? Let me know.

Anyway, here is the double.

Width of photo about 10cm

Here is one that I have shown before. It is from a fresh exposure, so it can’t be weathered.
Width of photo about 6cm

Structural Inversion and the Origin of a Late Ordovician Carbonate Buildup:

The Ordovician Earth System

Correlations Across A Facies Mosaic…

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Deep Water Stuff

May 17, 2010

The Ordovician of New York has been a fascination of mine since reading of C.D. Walcott’s discoveries, there, many years ago. A couple of years ago, I was granted the opportunity to visit a newly discovered lagerstatten in the Lorraine Group of Upstate New York.

The site was discovered by an amateur paleontologist from the region. In his quest to better understand the geology and paleontology of New York, he found the site that we visited, and several others that have produced stunning soft-tissue preservation of annelids and arthropods.

The Martin Quarry is located in the Whetstone Gulf Formation of the Lorraine Group in New York about 60 or 70 km north of Beecher’s Trilobite Beds. The rocks were deposited in a deep foreland basin that formed as a result of the Taconic Orogeny during the early Late Ordovician. The Late Ordovician was a time of intense tectonic activity on the Laurentian continent. As a result, the rocks of the Lorraine are characterized by sequences of turbidites.

It is within the turbidites that the exceptional preservation of the fossils are found. Bedding planes reveal hash plates with numerous partial trilobites-among other critters, but within the beds, whole critters can be found. And, if one is in the right horizon, the critters soft parts are preserved in pyrite.

Some photos:

After picking up a prep guy(one of the best in the field) at JFK, we got stuck in a traffic jam on the Tappan Zee… at 03:00!

Curiously, crinoids are absent from the locality, but they were somewhere, nearby.

The first thing that I saw when walking up to the outcrop was this lovely cephalon. The site is known for its Triarthrus fauna, and I was expecting it, but… this was the first Triarthrus that I had seen in the field! I was stoked!
photo about 15cm wide

A photo of me chopping away.

A photo of My Good Friend Who Is A Dog chillin in the creek.

A cutie(photo about 10 or 12 cm wide)

photo about 2cm wide

photo about 1.5 cm wide

Some kind of reptile… I might add, this guy shouldered(literally) a couple of tons of shale in an attempt to protect his finds, only to put on the gloves for this critter.

Probably, 75-100 partials on the slab.

Lots of partials and some other things, too. It appears that there is at least one calymenid free cheek, and a Sowerbyella brack. width of photo about 25cm

A nice ventral that is now part of the Peabody Museum collection

The guy that found this quarry developed a revolutionary an innovative technique in the preparation of pyritized soft tissue recovery… his methodology, at first, seems counter-intuitive, and maybe destructive, but his results are telling.

Further reading and references:


Beyond Beecher’s Trilobite Bed: Widespread pyritization of soft tissues in the Late Ordovician Taconic foreland basin

Farrell, et. al. 2009

Pyritization of soft-bodied fossils: Beecher’s Trilobite Bed, Upper Ordovician, New York State
Briggs, et, al. 1991

\Turbidite depositional influences on the diagenesis of Beecher’s Trilobite Bed and the Hunsrück Slate; sites of soft tissue pyritization
Raiswell, et. al. 2008

EDIT: to add photos

In the “Garden”

May 8, 2010

Upon returning to the Bluegrass region of Central Kentucky a couple of years ago, the first outcrop that I planned to visit was the type section for the Millersburg mb. of the Lexington Lm.

Generally, though out the Late Ordovician, most of the Laurentian margins were experiencing transgressive sequences, but here, regressive shoal complexes associated with deep-seated tectonics produced the carbonate clastics common to the area.

The Lexington Lm. is a complex assemblage of limestone and shale facies where the changes can be abrupt-both laterally and vertical. The formation is generally a transgressive sequence that grades upwards into the deeper water limestone and shales. However, in the inner-bluegrass region, the Tanglewood and Millersburg members are an exception to the transgressing sea sequences.

The Tanglewood is a thick sequence of coarse-grained calcarenites with local unconformities and tidal influenced structures; many of the beds are cross stratified(The header for the blog is one of those sequences).

The Millersburg is typical of the complex facie relationships of the region. It inter-tongues with the other members of the Lexington above and below, and in some places, it is absent; it isn’t even consistent within its own framework. Drive a few kilometers down the road, or climb/ descend a few meters in the column, and the fauna/lithology changes. The Millersburg is nodular limestone and shale that was deposited above the wave base.

But, I love it! The Millersburg is one of my favorite members of the Lexington Limestone. It is the unit in which I found my first trilobite, and one of my first crinoids. While, it is more known among local invert geeks for the common fossils found in its beds, there are some beds that produce spectacular finds(if you read this blog, you will notice that most of the stuff contained in it is from the Millersburg).

So, back to the start of the post. Driving out Main Street, I noticed that those nefarious engineers had widened the road. It used to be a nice drive in the country; now it is a four lane highway with a median and shoulders to park your vehicle if it decides to quit working. That sent shudders up my spine! Then, as I approached the type section, my heart fell out. It was gone!

The type section gone? How could it be? Perhaps it was ignorance; maybe the reason was economic? Who knows? But, It was gone!

Unfortunately, the destruction of significant geologic treasures is common. I have to assume that the reason is ignorance… how many engineers could know the significance of what they are destroying when they plan their construction projects?

My favorite outcrop was no more. Oh well! One has to move on, and so, I did. About a kilometer down the road, and a 10 or so meters down in the column, there was a tongue of Millersburg sandwiched between some shallower stuff of the Tanglewood mb.

On one of my first visits to the site, I found a nice Pychnocrinus sp., but I didn’t find the bed that it came from. It was located in the float at the base of the outcrop.

width of photo about 10cm

With this clue, my latter visits to the site were spent in the area where I found that little cutie. At first, I wasn’t having a lot of luck locating the bed in which the crinoid was from, but then I climbed a little up in the column, and perched at the edge of a ledge, I found this large pinnate structure.

width of photo about 12cm

Just above the ledge was a bed of clay that pinched out a couple of meters in both directions. That small bed has produced over 40 crinoids in just the face of the bed.

Curiously, a lot of the crinoids appear to be severely weathered… even when pulled fresh from the rock. The rapid changes in lithology-vertically- is thought to be a result of changes in sea level due to tectonic forces related to the Taconic Orogeny. The bed might represent a paraconformity where a small uplift drained the area resulting in the bed’s exposure.

Pychnocrinus (?)

This is one that I found recently. microscope stage for scale

Calyx encrusted by a bryozoan(I’ve never seen this before)
width of photo about 20 cm

Lots of partials(you know the scale by now)

Some are hard to recognize, at first

I have prepped a lot of the crinoids, and some have turned out, nicely. I’ll put some of those up in the future.

Further reading and references:

Contributions To The Geology of Kentucky: Ordovician System

From the Cincinnati Arch to the Illinois Basin: geological field excursions

LITHOSTRATIGRAPHIC FRAMEWORK OF THE TANGLEWOOD BUILDUP, LEXINGTON LIMESTONE (UPPER ORDOVICIAN) OF THE BLUE GRASS REGION, CENTRAL KENTUCKY

Sequence stratigraphy and long-term paleoceanographic change in the Middle and Upper Ordovician of the eastern United States

Extinction, invasion, and sequence stratigraphy: Patterns of faunal change in the Middle and Upper Ordovician of the eastern United States

Crinoid Holdfasts

April 28, 2010

It is a busy week, so a quick post to show a few different crinoid holdfasts from the Ordovician of Central Kentucky.

This first one was recovered from a mud mound in the Tanglewood mb. of the Lexington Limestone in Fayette Co Ky. This outcrop is strange in that the Tanglewood is a calcarenite that was deposited above wave base, and has many local unconformities. As such, the fossils are generally broken and abraded.

At this locality, there is a mud bed that is of limited lateral extent(a few meters) that has produced numerous(about 50) Pychnocrinus sp and Archaeocrinus sp. About the only other fossils found in the bed are bryozoans, an occasional gastropod(Cyclonema varicsosum), and some scolecodonts. I’ll present those in the future.

Perhaps, it was a lagoon, or channel, that protected the community from currents and waves???

Notice the pinnate structure. There might be more to this one.

Close up of above.

Curiously, quite a few of the crinoids from the site are missing the calyx.

In Franklin Co Ky, there is another outcrop that has produced about 100 Reteocrinus sp. The bed containing the crinoids is in the Millersburg mb, and about a meter below the contact with Tanglewood. Since the ossicles are of a different shape than the Reteocrinus ossicles, this is probably from a pinnate form that is uncommon at this locality.

scale in cm

.A few crinoids from the outcrop can be seen HERE.

The last two are the ones that I mentioned in this post. They were recovered from the Clays Ferry Fm. in Franklin Co Ky.

The outcrop in which these were found is known to produce several species of crinoids, but I haven’t spent much time in the field, there. Perhaps, this summer?

A Lovely Critter

April 25, 2010

When driving to my sister’s house in Anderson Co. Ky, the road that I travel traverses the beautiful Kentucky River gorge. The Kentucky River is a meandering stream that was entrenched in its gorge by an uplift in the area during the early Pliocene.

The relatively recent uplift in the area has resulted in an immature drainage of the subsurface that is especially noticeable in periods of heavy rain. In the winter, after a low pressure system moves through the area dropping rain, and if the temps drop below freezing, stunning examples of the immaturity can be seen at many outcrops(more on that in a later post???)

Crossing the gorge on this route, one notices the Austin Nichols distillery; makers of some of the finest Bourbon that money can buy, and a progenitor of some of the greatest times that I have ever had…
Photobucket

… and probably at least one divorce!

The outcrop in the middle right of the photo is the Logana member of the Lexington Limestone. The Logana is a sequence of alternating limestones and shales that is, for the most part, poorly fossiliferous. For that reason, I never gave it much thought. However, at the base of the Logana is the Curdsville mb of the Lexington.

The Curdsville, though sparsely fossiliferous, has been known to produce, exceptionally rare and well preserved, echinoderms and trilobites in shaley partings separating some of the beds.

Finding a place to park for this outcrop is challenging; there used to be a roadside park adjacent to the outcrop in the days before the interstate system, but alas! No more(Too, It is dangerous, as the road is curvy and only about a meter distant). As luck would have it, about a kilometer up the hill is an area where a suitable place to pull over can be found.

So one day, with a little time on my hand, I checked it out.

I found a large boulder that had probably been blasted when the road was cut, and on the boulder was found this Iocrinus sp.
width of photo about 12cm

A few centimeters from the crinoid, this holdfast was found.
width of photo about 10cm

At the time, I only had a hammer and chisel, so I chopped the two pieces from the rock. Hence, the breakage.

Apparently, Iocrinus sp has not been found accompanied with a holdfast, often, and there is some debate as to its type holdfast, ie, was it sessile???

If the holdfast found intimately associated with this critter was its own, well…

addendum: I have worked the outcrop extensively. It is dangerous, and not worth your time. I have “pulled” anything of any substance… which was little, and there are many more productive outcrops in the region. DON’T GO THERE!

Not Seen, Often

April 21, 2010

Years ago, while at a friend’s farm in Anderson Co. Kentucky, I noticed a small bed of rock(calcilutite) in the Clays Ferry Formation(early Late Ordovician) that was composed of, almost entirely, “orthoceras” cephalopods and partial pieces of the trilobite Isotelus gigas. Upon further examination, I discovered that the bed contained quite a few complete, or nearly complete, trilobites.

With a little patience, and a hammer, one could pull, at least, one or two complete “bugs” with every trip.

One day while working the creek, I noticed a piece of float that contained 5 crinoid heads. I left the area shortly after, and unfortunately, was never able to locate the bed that contained the crinoids. Interestingly enough, the piece of float also contained a few conulariids(I’ll post those soon). The reason for the post is this beautiful, and somewhat rare, disparid crinoid-Columbicrinus sp. that was found that day. It is the best of the bunch. Now, that I am back in the area, I hope that the bed that contained this handsome critter will finally be located.

The grid is 1/4in(0.625cm)

Same scale

A Few Crinoids

April 16, 2010

A quick post to show some of the crinoids that I have pulled from one of the outcrops that I have been working in Franklin Co. Ky.

These were collected from, what is probably, the beginning of the Late Ordovician. All are Reteocrinus sp., and all scales are approximate.

This is one of the first sights that I saw when I walked up to the outcrop. Within a few centimeters of this stone, I found five more similar.

found beside the one above

Same as above after “blasting” it with 30 micron dolomite and sodium bicarb

At least four on this one(width of photo about 11cm

Maybe, NSFW if you are crinoid(notice the tegmen)

Nice rock

Up close of the one above(sorry about the over exposure)

More Seismites, and some fossils, too

April 13, 2010

North of Frankfort Ky, some outstanding outcrops of Ordovician rocks are exposed in road cuts along U.S. 27. The outcrops represent an accumulative sequence of sedimentation spanning several millions of years, and the fauna represented in the rocks are typical of Mid.-Late Ordovician shallow tropical seas-brachiopods, partial trilobites, bivalves, gastropods,… ect. All of the usual stuff.

I want to show you a few more photos of some seismites, but first, let me regress. I was in the area to work an outcrop that has been producing large numbers of crinoids, and other interesting oddities(like this and this). But, that morning I wasn’t having much luck finding anything. Though, as I was packing up to leave, I noticed some pinnate structure in a small stone.

Normally, I would pass on something so insignificant, but as this was a second species of crinoid at the outcrop, I picked it up and threw it in the backpack to further document the fauna at the site. When I started working this outcrop, I found a couple of pinnate arms from some kind of crinoid. Until this trip, I hadn’t seen any other crinoids other than the Reteocrinus sp. that are found in abundance in a small talus pile at the base of a small outcrop.

This is the insignificant pinnate structure after a little prep! I haven’t identified the critter yet, but I have an ideal.

A few other photos from the outcrop.

A big ol’ ambonychiid bivalve.

A hypostome from the trilobite Isotelus gigas. The critter that molted this would have been a monster… probably about 25cm!

Rynchonellids litter the ground at this outcrop.

A nice Hebertella frankfortensis.
anterior view

posterior of above

Strophomenids are nearly as common(Rafinesquina sp. in the lower center left).

A trepostomate bryozoan exposing the “tubes” of the zooecia.

A change in lithology from the Millersburg to the Tanglewood members of the Lexington Lm.

Cross bedding in the Tanglewood (a few centimeters from the contact).

On to the Owenton Rd.

A photo of the outcrop along the Owenton Rd. after turning from the bypass. I pulled this photo from Graham Young’s wonderful blog-Ancient Shore. He was in the region for the North American Paleontological Convention, last summer.

As the day was getting hot and humid, I didn’t spend much time at the outcrop looking for fauna, but I did find a few crinoid holdfasts(apparently, I have deleted them from my hard drive. I will re-photograph, and put them up in the future). But, I did save photos of the thick sequence of seismites.

close up of above

Unusual Trilobite Crinoid Association

April 6, 2010

Today’s photograph is of an unusual association of an odontopleurid trilobite and a diplobathrid crinoid that was collected from the Ordovician of Kentucky.

The trilobite(Acidaspis sp) is seen on the top most brachial of the crinoid(Reteocrinus sp.), in the photograph.

I am still trying to determine if the assemblage represents thanatocoenosic(death assemblage) preservation of a community, or post mordem predation by the trilobite, and then preservation.

Anyone have any thoughts?

Coprophagous Symbiosis

April 4, 2010

Poop eating gastropods are relatively rare in the Ordovician rocks of Central Kentucky, though they are better known from the Devonian. I pulled this Glyptocrinus sp and Cyclonema varicosum  from the Millersburg Mb. of the  Lexington Limestone in the spring of  ’86.

Ordovician

Lexington Lm

Millersburg Mb

Fayette Co. Ky.

The scale at the bottom of the photo is 1.00 in(2.54cm)