Mazon Creek Nodule Hoard From Fossil Rock

[digit]

I decided to create a new topic to illustrate the processing of the hoard of Mazon Creek nodules my wife Tammy and I dug from Fossil Rock campground in Wilmington, IL. The planned outing date got rained out but I was able to make it out two other days for some fossil oriented aerobics. If you missed the saga of the digging, you can catch-up on that here: http://www.thefossilforum.com/index.php?/topic/54669-6715-join-us-as-we-dig-300myo-fossils-in-the-francis-creek-shale/?p=589045

I hope to use this topic to show the freeze/thaw processing of the nodules we recovered and to showcase any interesting finds that pop-out in due course.

I had great fun yesterday packetizing handfuls of nodules into plastic shopping bags (since cleaned and recycled). I brought along enough suitcases to distribute the load and keep each suitcase just under the allowed 50 pounds (~22 kg) so the airlines wouldn't boot the bags. This morning I unpacked the bags and pulled out the clothes and other packing that I used to keep the ballast of nodule bags from getting tossed around inside the suitcases. I usually find a little paper note from the TSA whenever I pack odd things in my baggage but apparently a box of rocks was not unusual enough to raise the interest of the baggage screeners.

Here is what the suitcase looked like when the shoes and a few other (lighter) items were removed to reveal the good stuff.

Cheers.

-Ken

[digit]

Turns out all the nodules would fit into a 5-gallon bucket if packed well. Here is my cache of Mazon Creek goodness that I'll be having fun with over the summer till fossil hunting season starts up again here in South Florida. You can see the nodules are still coated with the muddy clay (now turned quite white). I've got some nice larger ones to balance out the smaller nodules. Some of the elongate ones scream "fern pinnule" (if you listen carefully enough). You can see one of the smaller oval nodules has already dried out a bit and has started to shed an outer shell of shale. From my experience last year the first couple of freeze/thaw cycles did little else but help these nodules peel away several "egg shell" layers to reveal the actual concretion inside.

The second photo shows the nodules after their first rinsing. I've split them into two buckets to make it easier to rinse and pour off the muddy water. After I took this image I filled up both buckets to allow the nodules to get their first good soaking. The aim here is to get the nodules permeated with water so that the the freeze portion of the cycling will cause the water to expand and separate off the outer layers. Once the nodules have stopped peeling like onions the goal is then to get enough water to penetrate the concretion to allow it to pop on the fossil plane. I'll let these soak for a week or so and then start batching off some of these into a plastic shoebox which will get to spend some chill time on a shelf in my freezer. I'll update this topic as things progress.

Cheers.

-Ken

[digit]

While the majority of the nodules continue their long soak in the bucket in my garage, I've grabbed a selection to start their first freeze/thaw cycle in my freezer. I've found that inexpensive plastic shoeboxes available in the organization section (with closet shelving and other storage bins) of my local home improvement store work well and stand up to the temperature cycling. I've cleared away the packets of frozen mango and other frozen foods from a convenient shelf and started the freeze portion of the cycling. After these have had a day or two to get as cold as they are going to get I'll pull them out and fill the box of rocks with some water from the hose and let it sit outside to thaw. Then I'll get to see which nodules want to shed their outer shells of slate as they progressively disrobe down to the concretion at the center. I'll take a few more photos throughout this method of popping nodules so those unfamiliar with it can envision the process.

The first batch--selected and in the chill chest:

Cheers.

-Ken

[TNGray]

Been there... Done That! The fun goes on for a long time! I had some in/out of the freezer for over two years. Alas they failed to yield even after that many cycles. Good Luck!

[digit]

I've found that for the stubborn ones (and even the less stubborn) that a few light taps around the edge with a hammer while inspecting the nodules after they've thawed is sometimes just enough persuasion to get a sticky nodule to release. These nodules will likely have to shed a few layers of wrapping before I get down to the splittable nodule enshrouded within.

Cheers.

-Ken

[digit]

I took the first batch of frosty nodules out of the freezer today and thawed them out. I've frozen nodules in this plastic shoe box topped-off with water and sans water like this and haven't really seen any difference in promoting nodule popping or shedding of the outer layers of shale. As a result I usually just scoop a load out of the 5-gallon bucket in which they are soaking and load them wet, but without a bath of water, into my freezer shelf. It makes the shoebox a little lighter to carry and the thawing happens quite a bit quicker without having to melt the ice matrix into which the nodules have been frozen. I'd love to hear anybody's opinion as to whether or not they have solid experience promoting one method or the other. As the work of nodule splitting is done by the expansion of the water permeating the nodules during the freeze phase and not during the thaw portion I just try to make sure the nodules stay as sodden as possible.

Here's a look at the first frosty load and the same batch filled with water from a hose to start them thawing:

Cheers.

-Ken

[digit]

The point of the first freeze/thaw cycles is to shed any outer layers of shale to get to the solid siderite concretion at the center. It seems to make sense that the water will better penetrate any micro-fissures in the concretion once the outer layers have been peeled away. I've got an old 30 cm x 30 cm concrete paver stone that I use while working these nodules. I find that a few light taps along the perimeter will start the outer layers separating if they are ready to shed. Here is an elongate nodule that had already started to strip off its outer layers just due to the drying out of the nodule once it had been removed from the ground. The only thing I needed to do to this one was peel it by hand like an onion.

Cheers.

-Ken

[digit]

Other nodules started shedding their shells like hardboiled eggs after a few light taps with the hammer. I've found that a small flat blade jeweler's screwdriver or various dental tools are quite effective in probing under the edge of a peeling layer to pry off additional portions of the outer shell.

The peeled nodules got a quick rinse to remove more of the mud and powdered shale that quickly turns the water in the bucket a sickly shade of brown looking like a most unappealing bucket of Café au lait. Once rinsed the slimmed-down nodules go into a second water-filled bucket in my garage. I'll slowly work my way through the bucket of nodules taking from one bucket and depositing into the other after the freeze/thaw cycle. Once all the nodules have had their turn in the freezer and the first bucket is empty I'll swap the "in" and "out" buckets and continue processing. This process will continue many times but the volume in the bucket slowly decreases due to shedded outer layers at first and later to the removal of the nodules as they pop and reveal their contents (or lack thereof).

This was a bit of what was shed from the first batch:

Cheers.

-Ken

[old bones]

Oh, this is fun! Keep the photos coming as the unveiling continues.

[ZiggieCie]

This will be a reference work that will last here for years.

[digit]

By now you all know that I am a rather verbose and illustrative raconteur. It's nested deep in my DNA and I can't help myself so I feel obligated to explain and instruct once I've acquired a modicum of knowledge. Detailing the process I use to pop these nodules to release their 300 myo treasures comes naturally to me and this forum provides a perfect outlet. Were I more into social media (which I definitely am not) I would have a blog to post my ramblings. Instead, TFF provides a perfect vessel for me to pour my loquaciousness into (and use big words like loquaciousness), When I'm talking (or typing) about a subject I'm passionate about it is hard to stop me (many have tried) so I hope that others may benefit from my story telling on this forum. I'm glad to see that others are attuned to my ramblings and appreciate them for what they may be worth.

More to come as the process unfolds.

Cheers.

-Ken

Edited June 20, 2015 by digit

[Plantguy]

Hey Ken, looks like you are having fun with this. I unfortunately havent been able to get up there to collect directly but have gone thru the process quite a few times. There is a level of excitement that's hard to describe with opening the freezer door and looking thru the pile to see what may have popped. Curious to see what you end up with. Good luck!

Regards, Chris

[digit]

Mazon Creek nodules are fun as you can enjoy the experience of the hunt when you first dig (or surface collect) the nodules. Then, once you've gathered your little dragon's hoard of treasures (albeit not glinty like gold) you then get to experience round two of the hunt while trying to pop the nodules to reveal their prizes. It's pretty easy to recognize that some nodules (the elongate ones mainly) definitely contain fossil impressions (usually fern pinnules). These provide a bunch of hopefuls out of my batch. The flat round ones always have the potential for something like a horseshoe crab so you say a little supplication to the fossil gods when you locate one of those and toss it into your bucket. Some of the more non-classically shaped ones are the real gamble. I'll coin the term "Baroque" for these odd-shaped nodules (like they do to make misshapen pearls sound expensive). Usually these have the lowest percentage probability of turning out something interesting but out of that small percentage the item possibly contained within may be something special (a cool bug perhaps). Out of the ones that you can tell from the outside are most definitely plant material (the elongated ovals or cigar shaped ones) the real unknown there is the state of preservation. I've had some gorgeous shaped nodules open to reveal less than stunning (but still of course cool) fossils or be so riddled with transverse fracture lines that the nodule breaks apart like a puzzle rather than splitting evenly like a hamburger bun. Then, if the fossil inside is worthy, you need to spend a bit of time and a dab or two of glue to reassemble to pieces back into a pair of halves. It's all good fun and I'm looking forward to what surprises are in store for me in that bucket of nods soaking patiently in my garage.

Cheers.

-Ken

[Stocksdale]

Great Info!! I think I'm taking a group of Boy Scouts to Fossil Rock in September. The kids are wanting to get fossils but I'm still trying to determine if that is the best place or not......

I have done the freeze/thaw process for all of the ones I've found. But I've wondered about the simple "hammer wacking method". I've heard the plant fossils have a slightly better tendency to open nicely with a hammer wack than the marine essex ones. Has anyone had experience with hitting them with a hammer without total destruction??

The reason I'm considering it is that the Boy Scout kids have a bit more instant gratification. Perhaps the chance of destroying the fossil is just too high and they should learn patience. Anyone have experience with the hammer method??

[digit]

Surface hunting is fun as well (and you can get into the Essex Biota in places like Mazonia/Braidwood State Fish & Wildlife Area) but this is not the optimal time of year for that. It can be done now but as the weeds and undergrowth have started growing again in the summer it is increasingly difficult to surface hunt. The vegetation will likely still be dense in September but towards October the leaves should be dropping and the undergrowth dying down. If you do wish to try surface hunting I'd suggest hunting in the Mazonia South Unit around the lakes and on any sloping surface you can find (map link for reference):

http://www.dnr.illinois.gov/Parks/Documents/MazoniaBraidwoodSiteMap.pdf

Nodules don't tend to weather out of the substrate as much on level ground so look for elevation and eroded areas that expose the clay/shale under the vegetation. Get further away from the roads and trails (bring a GPS or smartphone to make sure you get back out again by dropping a waypoint where you leave the trail). You are as likely to find ticks as nodules this time of year while clambering around in the underbrush so long pants and long sleeves will protect not only from scratches while squeezing around in the bushes but also (with liberal coatings with DEET) may protect you and the boys from being a tick feast.

This time of year (up and through September) I'd really be much more inclined to recommend Fossil Rock hunting. During the winter the ground can be too frozen to make digging for nodules feasible. I believe Mazonia/Braidwood has a fossil hunting season as well and if I remember they close down for deer and duck hunting in the autumn (they don't want fossil hunters rummaging around in the undergrowth during this for obvious reasons). My simplistic thought process is that Mazonia/Braidwood is a great spring/early summer place to surface hunt and Fossil Rock is awesome till the ground freezes.

The Braidwood Biota of Fossil Rock with easily identifiable fern foliage might be more fun for a group of younger boys as well. Finding a jellyfish 'blob' (Essexella ashera) in the Essex Biota may be less stunning to first time fossil hunters than an easy to comprehend fern pinnule.

I'd still warn against the brute force hammer method unless you have to. That being said, I've found tapping the edges with the hammer during the thaw portions of the cycles is a reasonable way to accelerate the peeling of the shale layers to get to the concretion. It can also help motivate a stubborn concretion to give up its prize but many of these 300 myo nodules have picked up a transverse crack or two over the millennia and I've seen quite a number of nodules disassemble into a puzzle with even light tapping. If the fossil inside looks to be in good condition I'll try to reassemble with glue but often the cracks have let in moisture over the years and degraded the fossil plane enough that I don't bother too hard to salvage these (at least not when you have a decent cache of nodules to work with).

Early on before I got educated I attempted the obvious and bashed away with a hammer. Mostly I found that such action would just chip off pieces from the outside rather than cleaving the nodule evenly in two. Then again, at the beginning most of my nodules were duds that I found while surface hunting and contained few fossils inside anyway. I'm not sure if you'll find anybody here who has experimented with taking a hammer aggressively to good quality nodules (like the ones that can be found in Fossil Rock) and bashed away to see what percentage can be opened without pulverizing though some may have some anecdotal evidence. Back 70-80 years ago when the are looked much different with fresh piles of overburden terraforming the landscape in this area, some of the first collectors wrote about wandering over mountains of clay and shale and splitting nodules on the spot so they only had to wrap-up and backpack out quality fossils. This was the golden age of Mazon Creek hunting--actually, not so much 'hunting' as 'shopping'. These days the amount of effort expended to come into possession of a decent nodule that looks to contain fern pieces makes it too precious to subject it to too much abuse. My two cents anyway as a novice Mazon Creek hunter.

When you do go please take lots of photos in the field and post a trip report. I'm sure we'd all enjoy reading about it and vicariously experiencing your hunt.

Cheers.

-Ken

[Stocksdale]

Thanks. It might be good for them to learn the freeze/thaw process and the value of patience anyway

If we go down there. We might camp at the Scout Reservation which is right on the Mazon River where we'd have access and look for nodules along the river. (if the river isn't too high). Then go to the Fossil Rock campground for the day.

I've been still debating whether to take them to get Mazon nodules or go to an Ordovician location where they'd more easily find brachiopods and such. Or perhaps the Rockford, Iowa Fossil Park where there is lots of easy picking Devonian fossils. (but that is quite a bit further away.) Maybe, I'll present the options to them.

[Ludwigia]

Great stuff! Please keep the stories and updates coming.

[digit]

Thanks. It might be good for them to learn the freeze/thaw process and the value of patience anyway

If we go down there. We might camp at the Scout Reservation which is right on the Mazon River where we'd have access and look for nodules along the river. (if the river isn't too high). Then go to the Fossil Rock campground for the day.

I've been still debating whether to take them to get Mazon nodules or go to an Ordovician location where they'd more easily find brachiopods and such. Or perhaps the Rockford, Iowa Fossil Park where there is lots of easy picking Devonian fossils. (but that is quite a bit further away.) Maybe, I'll present the options to them.

Is there a merit badge for patience? This would be a good way to earn it.

Camping along the Mazon River (Creek) sounds ideal and ties into the whole fossil hunting activity. I can't say I've actually seen the Mazon River and I need to remember to try to make a visit to this namesake locality when I'm up there next. Looking for nodules outcropping along the river's edge (if the level permits) sounds like it could be fun. Bring some shovels and teach them that hard work results in rewards of a nodular shape when/if you go to Fossil Rock.

Sounds like you have several alternatives as well. Maybe based on the success of one outing you could follow up with a few different locations. I, myself, would love to get into the other to places you mentioned and need to do some research into Ordovician and Devonian treasure hunts--always up for something new.

Great stuff! Please keep the stories and updates coming.

Had a few pop already. One small one has something linear inside it but I haven't looked at it under magnification yet to see it in detail. Several elongate nodules have fractured on transverse cracks. I'm going to attempt to glue those back together into a complete nodule and then see if I can coax them to split along the fossil plane. Will post some photos soon.

Cheers.

-Ken

[Auspex]

I Googled "heavy duty mil-spec freezer shelves", without any results...

Guess ya' just take your chances!

[digit]

Time for a bit of updates on this topic. Mostly the nodules continue to peel their outer layers of shale to reveal the solid concretion within. Occasionally, a few nodules will split rather early in the freeze that process. The ones that seem to unfold the quickest tend to be the "bark" type fossils. I'm assuming these striated fossils are likely Calamites or something similar. They never seem to have the rhomboidal scale-like leaf cushion pattern of the Lepidodendron bark impressions. These fossils always seem to have a fair amount of relatively loose friable black material along the fossil plane which is why I think they pop so early. The first one pictured below seems to have what may appear to be a nodal seem toward the more busted up left side (visible as a vertical line running transverse to the main axis of the fossil).

-Ken

[digit]

Here are a couple of the small rounds that have popped already. The image below is from a tiny nodule (only 2 cm long). Many times I will not take minis like this as I figure the chances of them holding something interesting (or even identifiable) are slim. Just as some lottery tickets are, despite the long odds, actually winners--good things occasionally do come in small packages. When this one popped I could see the linear shape but little more (without my glasses). Once it was rinsed and dried I was able to look at it under magnification to see that it has the elongate "pine-needle" appearance with a distinct midrib which seems to place it soundly within the group known as Cyperites. Not the largest Cyperites in my meager collection but I nice little addition given its diminutive size.

When this nodule popped and I first looked inside I thought it was a dud (and it still may be). I rinsed it off and set it aside to dry. Though this nodule is far from visually explicit I think I can see a bit of pattern in the small white dots (best seen in the left half in the image below). I could just be seeing things or this may be the faint trace of a pattern as is seen on lycopsids. For me the jury is still out on this one and without a vast number of Mazon Creek fossils to compare this to I'm relying on those on the forum who have more experience with these Braidwood Biota nodules to chime in and decide if this is something or just another example of wishful pareidolia.

-Ken

[digit]

And now an overdue post on the bane of my experience with Mazon Creek nodules--cracks.

During the freeze that process--often early during the shale peeling stage while working down to the concretion within--I have nodules split transverse to the apparent fossil plane. This can happen if I'm coaxing the shale layers off with gentle taps along the edge with a hammer or just while peeling off the shale encapsulation with a small flat-blade jeweler's screwdriver. The main culprit seems to be weaknesses in the nodule itself. Take for instance this nicely shaped nodule below. You can see the crack that has split this nodule in two and what is lying along this crack. It seems that this crack has occurred some time ago and white calcium? deposits have filled in along this crack. In the side-by-side end photo of the cracked surface you can see what appears to be the line of the fossil plane as well as what appears to be a blackish three dimensional piece of fossil material that is forming the core of this nodule. Several brown slate infilled cracks are also apparent on the bottom left corner of the split view of this nodule.

Based on the cross section visible along this crack it appears that this nodule does not contain a fern pinnule but some thicker piece of vegetative material. The only way to be able to see further into this nodule is to hope to get the nodule to split on a more planar direction. My concern is that the black material at the center may have little structural integrity and during the course of subsequent freeze/thaw cycles it may decompose into powdery fragments--only time will tell what will come of this nodule.

Here is another nodule that has peeled off its outer layers of the brown shale down to the more gray colored concretion within. You can plainly see the slate infilled cracks running perpendicular to the length of this nodule. Though it is solidly a single piece at the moment, I have little hopes that this one will split cleanly. I'm expecting it to disassemble into several pieces during the next few freeze/thaw cycles.

-Ken

[digit]

Continuing on the fragmentation theme here are a couple of freeze/thaw failures. The first was a very long thin nodule which my wife dubbed "the tusk" when she uncovered it. It was about the size (and nearly the shape) of a cigar. Given the shape I assumed it was more likely a thin elongate fossil like a Cyperites rather than a fern pinnule. After about 2 freeze/thaw cycles most of the outer shale layers had detached but then the inner nodule cleaved into several fragments. As there was not a broad fossil plane that would exist if it were a fern pinnule but only a twine-like fossil core to this nodule, elongate slivers peeled away and the nodule broke up even more than when I set it out to photograph it. I had hopes for this unusually shaped nodule but luck was not with me on this one.

Here is another fragmented nodule that resisted efforts at reconstruction. The tip of this nodule broke off during the shale peeling phase of the initial freeze/thaw cycles. As often seems to happen the tip piece split not only along the fossil plane (revealing the tip of a fern pinnule) but each half also bisected perpendicular to this split. I was easily able to fix the splits in the two halves of the tip with a little dab of glue. This left the main portion of the original nodule still unsplit. One light tap with a hammer was enough to get the rest of this nodule to unfold. More of the outer layer on the larger section peeled away than it did on the pieces near the tip as can be seen when I attempted to re-attach the tips to form two "complete" halves. The broken end of the nodule at the opposite end from the tip of this pinnule was open in the nodule when it was whole and the pinnae at this end (left side in the second image below) can be seen to be rather weathered. Museum quality this fossil is definitely not and the tip pieces (though in their original position) look a bit odd and out of place. I'll likely detach these pieces and only keep the main portion of the nodule. I may use this lesser quality pinnule fossil to experiment with using some weak acid to see if removing the white calcium deposits improves or detracts from the visual appearance of this fossil. I may do this on one half and post photos in the future. Not one for the display case but a good specimen to experiment with without fear of messing up a favorite piece.

-Ken

[digit]

Here's another Franken-fossil which took to re-assembly a bit better than the previous example. This nodule's shape fairly screamed "fern pinnule tip" and in this case you can actually judge a book by its cover. Just after this nodule had shed most of its outer brown shale layers, it split--but not cleanly. I think nodules with one squared-off broken end like this tend to split quicker as the water has an easier time getting into the fossil plane through the broken end. You can see that his nodule split along the main fossil plane but also cleaved into several chunks. The tip held together but I could see the crack running to the tip of the pinnule so just a bit of prying with a jeweler's screwdriver was all that was needed to separate the rest of the nodule's components.

After a bit of gluing the puzzle pieces together the two halves of the nodule have been reassembled. Other than a few small bits that have gone missing which distract from the appearance of this reconstruction, the nodule is not the worst I've seen but likely not destined for display. Once again you can see the additional weathering toward the broken end (visible as a blurred lack of detail at the bottom in the final photo). Broken pieces of larger nodules like this tend to pop quicker than more complete shaped nodules but the quality of the fossils within often suffers from weathering.

-Ken

[digit]

Here is yet another nodule that I had high hopes for but which an internal crack has shattered (along with my hopes). You can see the white calcium material that has infused this crack making the weak area on which this nodule split. You might be able to see what appears to be a slightly contorted fossil plane looking at the cross-section. If the animated GIF image I made works correctly you should be able to see what appears to me to be the fossil plane. Click on the right image below to see this animation.

I'm taking this nodule and a few other ones that looked hopeful but split badly and I'm soaking these in smaller cups (rather than tossing them in the 5-gallon bucket with the other nodules). This way I hope to be able to keep both pieces of these nodules together so that they may be reassembled if I can get them to pop along the fossil plane. I'll freeze and thaw them in these cups and see how that works.

More to follow as soon as something interesting happens.

Cheers.

-Ken

Edited July 4, 2015 by digit