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In this thread I will be posting my best finds from Mazon Creek localities - so far I’ve only visited Mazonia-Braidwood fish & wildlife area and the Braceville coal mine spoil pile. “Mazon Creek beds” is a colloquial term for a Pennsylvanian Lagerstätte preserved in the Francis Creek shale member of Carbondale formation in several areas of Northern Illinois, including Mazon creek itself. Back 310 million years ago, that area was a river delta that preserved remains of both aquatic and terrestrial organisms in siderite concretions, that now (in the Holocene) you can find and open yourself to reveal the fossils. It is typically divided into two separate biotas - Braidwood, which is largely terrestrial, and Essex biota that is more marine. So far, I have only collected at Essex localities. So, I will start with by far the most common organism in the Essex biota - Essexella ascherae cnidarian, that was first thought to be a jellyfish and is now considered a sea anemone. They mostly preserve as “blobs” of quite diverse shapes. Here are some of my favorites - first, two large specimens from Braceville. This plate preserves 8 small individuals, also from Braceville. These two smaller ones are from Mazonia, Tipple hill area. Note that if Essexella was an anemone, they are positioned upside down in the pictures.

Just got back today from my first trip to Mazonia-Braidwood (pit 11) this year! I unfortunately couldn't make it on the opening weekend, and was afraid we won’t find anything this late - but I ended up being pleasantly surprised. By this point I ran out of concretions to freeze-thaw from last year, so I’m very excited for the next few months We decided to go back to the Tipple hill area. Here is what it looks like now - open, barren fields of rocks 99.9999% of which are not what we are looking for. What I found especially challenging about this area, is that there are numerous concretions that have perfect shapes, but are not actually the right type of rock - yellow/light orange. I haven’t seen them at other places within Mazonia. I tried cracking a few last year, but they just have quartz (?) crystals on the inside. I guess they are not actually from Francis Creek shale? I forgot to take pictures, but would be curious to hear from people familiar with this. And of course, here are a few dinosaur eggs (the right type of rock) in situ Here is the total haul. Probably not a lot for this site, but this is definitely the most productive pit 11 trip I’ve had so far. Even better, unlike my previous visits, this time I found quite a few fossils in already open concretions. Here is a shrimp molt Both halves of a Calamites I think this is a Cyperites leaf These two halves of Annularia whorls cracked on the drive home And, of course, a neat anemone - Essexella ascherae. Surprisingly, this is the only one we found (so far). Will keep this thread updated with new fossils as I freeze-thaw the remaining concretions. I will also be back to Mazonia this weekend, but will probably go to a different site. I’m hoping this will become a mega-thread of all of my future Mazon creek trips. Out of all of the fossil sites I ever collected at, this is genuinely one of my favorites, if not the favorite - amazing fossils you can’t find anywhere else, plus instant gratification from finding concretions is always followed by delayed gratification over months of opening them. Here are my past trips to Mazonia and Braceville in 2023:

I'm new to fossil hunting myself. So let me add a few things that I haven't seen in the forums for finding sites. First off, I kinda took the long approach. I'll give the steps I have taken. I tried to jump to the "point me to a site to dig and find a fossil", litterally only 1 site in Illinois <where I live> is famous and openned to all for part of the year... Mazon Creek <which unfortunately is a day trip away for me> So started using google. Everything still pointed to Mazon Creek or Rockford area <even farther away>. Now Mazon creek fossils are famous and worth the trip and chance to collect. But, its heavily collected, over grown this time of year. <I learned the hard way by visiting> Now onto my approach to this. I started with some of original geological surveys for my state. <talking 1880's reports for my state>. The great part about this portion was reading the reports and understanding what was here before all the major cities, highways, dams and general human land modifications that have occured. The shear amount of geographic modifications we humans do, its down right scary. But, the best part about this. It is that these first geologists where not biased to one location or another. They noted what they found and where. The Economical surveys have proven to be my best finds so far, Since the geologists used the found fossils at these sites to build up the picture of the geological layering and composition of the forming regions. And the best part is they were using the same Quadrangle maps that became standard for the USGS civil mapping projects back then. The maps break down to the township and section locations then break down to the location with in the grid. It really narrows it down quite a bit. In addition to the geology of a area, they not unique features at times, stone quarrys, clay pits and old mines. Not only vertical mines, but also slope mines and bank excavations. Nearly all of these sites have been abandoned and forgotten now. From the orginal surveys I worked up thru the years. I did not read every county within the survey. I concentrated on things within an hour drive of home. So this narrowed my reading down to approx 8 counties. Unfortunately what i found going up thru the surveys and closer to present. They changed more and more into technical mobo jumbo that I didnt go to college for. They were less and less deverse and started to lack clues of where to locate my objective. Which was always easily reachable fossils. Most of those surveys are free online, either thru your state geological survey department or most e-book retailers even have some for free. Personally I have a nook, so i use Barnes and Nobles, IGSG and USGS for alot of my stuff. Additionally Quadrangle maps, 7.5 minute, 30 minute and 1:100,000 USGS maps and topographies. I cant stress they maps enough. These maps come in MANY types. examples I use now: topography, surface deposit, quaternary deposit, loess, moraines deposits. Now the newer maps <since 2008> have been updated to be more percise than the older maps, so somethings are a little off from what you will read in these old surveys. But Its easy to cross reference the locations since each of the locations will mention the land holders name 9 times out of 10. With that information you can check at a local library in that county for a Plat Book for the year in question and narrow it down further. But most of the times you get the general area. Now the above information will kinda give you a idea of whats actually around and under all that concrete thats been poured. Next came the fun parts and also make interesting days trips for learning the geology in your area. Geological Field Trip Guide Books! Geological Field Trip Guide Books are basicly a field trip containing a route, locations and points of interest. Here in Illinois the ISGS has 4 annual field trips. They are basicly a way to engage the public to geology. Each book has a Full route, Map, distance, what is at each stop and some historical facts. They are designed to not only follow along with on the day of that planned field trip, but also to be followed by other groups or individuals at later times. In nearly each field trip I have read thru, there is at least 1 stop for collecting Rocks or Fossils. And each time they have been a site I may have driven past a dozen times in my life and never thought to look there. Older field guides are usually available for free off most geological survey sites. However newer ones may cost a few dollars. Most have been made available online but pre 1985 ones here in Illinois have to be purchased printed for a couple bucks from the geological survey. Now next up on my reading list was my state geology book. Here in Illinois our ISGS <Illinois State Geological Survey> has a book written by them with a complete overview of the state geology. This filled in alot of gaps for me and has started to lay a firm ground work for my knowlege <It ain't all greek anymore!!!> I attempted to read this first, but alot didnt make sense to me, partly due to the fact the local geology was a mystery since I just moved here not long ago. Beyond that I have read a few other geology books for my area of the country. At last I found my "bible" per say at my local library. Its called "Fossils for Amateurs - A handbook for collectors" by Russel P. MacFall and Jay Wollin. I really wish I would have started with this book. The book was written in 1972, but every bit of it is still valid. This is a "must" purchase. After borrowing it from the library, I ended up searching and buying a near mint copy off Amazon for $11. Unfortunately there are no active geological clubs around me. There was one, but there website has been defunct for over 2 years now. Check for a local club, this would be a great option. Last but not least, Surfing the net! I just browse and find some interesting things now and again. Some youtube video, flickr <thanks to alot of cams now having GPS>, facebook, news article or blog post. Found a few leads this way. I will also say i've found a few sites that were illegal to hunt and collect in this way too. But take those sites and view the geology and most times you will find a site outside of the park boundaries that is accessable and huntable Now all thru my journey thru this "education" process I have been documenting the sites mentioned thru all of these sources thru Google Earth. This gives me the satalite view of the areas and a way to plot them. Once I visit a site and locate specimans I use my Garmin GPS to note the exact location and Log them in my journal. That way I can update the locations on my google earth files. In addition, google earth and streetview are excellent for discovering rock outcrops, streams, and interesting features while Im planning my excursion. This allows me to have a goal, but also gives me alternate sites incase the first place is a bust. So that has been my approach, so far I have cataloged approx 50 sites from my research. I've only had time so far to Verify 3 due to work schedule and crappy spring-summer weather. Each one in a place that was "Bull dozed by glaciers" and buried under yards of loess. Luckily for me, There are Silurian and thin devonian beds in my coverage area. And I am quite partial to those eras. But most eras above the Pennsylvanian has been cleared by the glacial advances over the last 100k years. Still I have hope that maybe one day I'll come accross some loess from the jurassic that was sheared off and deposited in a moraine contaning a dino bone and become the first person to locate one in Illinois Ok thats my 2 cents and journey. I'm moving this from a response I added in the Q&A forum on the advice of CoCo My take of this may be a bit unique, but so far I believe its working. And one other thing, which has turned out to be my biggest and best reference so far. This site, and the people on it!

Last weekend I had the opportunity to spend a few hours collecting in a quarry in northern Illinois that exposes most of the Galena Group (Late Ordovician). There was lots of fresh rock to hunt through, and it was a good and productive trip. As usual, lots of gastropod molds were found. Hormotoma sp. Liospira sp. Sinuites sp. Lophospira sp. Subulites sp. Unknown gastropod. Looks like Liospira but appears to curl in the opposite direction. Brachiopods show up too. Most common are molds of what I believe are Rafinesquina (@Tidgy's Dad?). The inarticulate Pseudolingula iowensis is somewhat common. Specimens are almost always crushed and missing shell, but they usually have some shell preservation which contrasts nicely with the yellow matrix. Occasional bivalve molds are found. This one has calcite? crystals. Trilobite parts are uncommon, and the only species I've seen from this quarry is Thaleops, possibly Thaleops laurentiana. Here is a cephalon I found. Now for my favorite finds of the day. A partial specimen of the small receptaculitid Ischadites iowensis. Fisherites is very common at this site, but I had not come across Ischadites before. A partial conulariid. Judging by the visible cross section, the back side is present, so this should hopefully prep out nicely. And finally, what might end up being a complete trilobite. Not sure if there is any more buried, but it does look like at least some of the shell is preserved, so fingers crossed!

Hi, I am a graduate student from Chicagoland looking to get into fossil hunting. I recently started school in Wisconsin and I am hoping that I can make some good finds in this state. I have tried fossil hunting in the Mazon Creek area of Illinois, but I only ever found a single horse tail fossil and a hermit's shanty over there. Overall, the area is a pain to search unless you have a boat to access the islands in the lakes and I am hoping I will have better luck in Wisconsin while I am here.

I found this on the banks of the Mississippi River in Illinois. So I don’t know where it originated. So I can’t help with age or formation or even a general location. I posted on a couple fossil pages on Facebook and going to try here. Any help will be great. Rough size is in pictures but they are 7.93 mm wide and 6.31 mm tall roughly. If you have questions I’ll try to answer them the best I can. Thank you

ive been reading this PDF as to understand how PLSS descriptions work, and its *mostly* been making sense to me: PLSSTutorial-1.pdf however, i have one small issue in the guide, it mentions basing the "range" and "township" positions off of a "starting point" but, it doesn't specify why the starting point is where it's at, and it also doesn't explain where/how to identify a state's starting point is the "starting point" a fixed position on a state? or does it vary, say, based off the description given in a PLSS coordinate, like the one I've attached? (covered the county name for the sake of confidentiality) big thanks to anyone who can help out!

I found these two somewhat close together on an eroding hillside just south of WI in Stephenson County, IL.

Hello, I've stumbled onto this site while doing research on doing scientific illustrations of green River fish. I've prepared many specimens over the years, but now want to do accurate illustrations of these fish. The research involves gathering as many fossil images as possible, and then finding living relatives and using them as references. Very time consuming, but for accuracy, one cannot find enough references.

Hello nice to meet u

I’m sure I will happen upon the right website at some point to identify it, but haven’t yet… certain it’s easily identified by the experienced. Can anyone help? I assume it’s a sponge? Maybe coral? Type? Thank you. Illinois.

Hi, everyone. I found this rock yesterday in Illinois. I was thinking it could be petrified wood. I had my doubts, so posted elsewhere looking for an ID and received a response of “some type of coral”. Later in the night, while looking up fossil corals, I happened upon the word “Chaetetes“. When I looked it up, a few pictures seem like a close match…maybe exact? I’m wondering what the experienced think about it. Thank you.

I'm in the process of photographing and cataloging specimens from a new site and thought some here might enjoy seeing some specimens as I go. These fossils were collected in eastern Illinois from the roof shales of the Herrin (No. 6) Coal. They are middle Pennsylvanian (Desmoinesian) in age. The Herrin (No. 6) Coal is the second to last coal member of the Carbondale Formation. For reference, the Mazon Creek biota occurs in the Francis Creek Shale Member, which overlies the first coal member of the Carbondale Formation, the Colchester (No. 2) Coal. Here's a general stratigraphic section of the Carbondale for reference. This biota has similarities to the Mazon Creek biota, but the flora especially is quite different. The fauna so far seems typical of terrestrial Pennsylvanian sites: bivalves, branchiopods, indeterminate arthropod parts, and a single shark egg. This biota is not well studied, and thus many names here are provisional pending a possible formal study. Scale bars are 1cm unless noted otherwise. Dunbarella striata Calamostachys tuberculata Alethopteris gibsonii Cyperites bicarinatus

Hi I hope I’m doing this right. I live on a small farm in northwest Illinois just south of Wisconsin. Half my place is a wetland with a creek running through it; it has changed very little since the first plat of the area was drawn in the mid 1800s. I find a lot of fossils and quartzy and other rocks/minerals and I’m here to learn more about what I find. Thanks!

Hello, it’s been awhile! I’ve been opening up some Mazon Pit 11 stuff and came across this thing. I try to keep myself pretty grounded when it comes to Mazon stuff, because I’m horribly bad at ID’ing anything in a concretion. That said, any chance this is an annelid worm? Thank you as always!

I found this handsome mystery in a Central Illinois creekbed. While I think it could be a sponge, it doesn't resemble any that I'm already familiar with. I wonder if it could be Brooksella Alternata, however that seems unlikely due to it coming from Illinois and not further south. I'm stumped, but beyond curious. Any input would be a dream. 20240219_214229.mp4

Hello everyone. Been a while since I've been back on....life amiright!? Anyways coming back on the hunt with 2 kids now plus myself. Got some sites up my sleeve to pay a visit and re-visit. Lot of posts to go thru to look at others collections. Again...hello

I've been spending a lot of time lately studying the Mazon Creek flora, and am continuously astonished by the diversity and quality of specimens that can be found. I don't think we see enough plants on the forum, so I figured I would go ahead and share some of my favorite finds. First is a specimen I recently shared, and a fitting start to the thread. This is Crenulopteris acadica, the most common true fern found in the Mazon Creek flora. It has been the most common plant I find, accounting for probably half my finds. Next is a favorite of mine. This is a section of Calamites (probably C. cisti) encrusted by a number microconchids. I always enjoy finding concretions with associations of different species. Last for now is a specimen of the rare seed fern Callipteridium neuropteroides with great coloration.

Hello I’m joe from southern Illinois. Been lurking in the shadows for awhile decided to join. Been doing fossils for about 6-7 years now. I have a few things I need help with identifying and some things to show off and maybe help some people out and learn a ton. Want to know anything else feel free to ask.

Because of this forum I found out about the Burpee Museum . The world’s best assistant and general laborer offered to take me there today. Prepare to be spammed with photos.

Hello, Could I get an ID on this mazon creek unknown? It has pretty high relief and strong segmentation with makes me think arthropod like a millipede, but I don't see any legs so maybe it's an annelid worm or something.

I've been chipping away at this cobble when I have spare time, and slowly exposing this fossil. I found the stone itself in western Illinois, relatively near the rivers. The matrix is shockingly tough, I can only rarely make a difference with any sort of precision, unpowered hand tool. Each grain of sand is firmly in place and does not want to leave. The exposed matrix was originally reddish to brownish, though newly exposed faces of chips broken off lack the red-brown color (the reddish color is entirely lost in the photos). Presumably the stone is Mississippian or Devonian. Other fossils in this rock are all flakey white brachiopod material ranging from 0.5 cm to 4 cm across at the widest points. I have tested some matrix scraps against vinegar, which dissolved the stone around the sand grains, but left the sand grains untouched. I've decided to hold off on any more matrix removal until I know what I should expect to find in the matrix. I found a second one of these, but it chipped off and lost it in my prep area outside. When it comes to the horses & zebras adage I always put more consideration into the zebras than I should, which is why I'm hoping this is some part of a vertebrate but more likely an oddly colored crinoid bit. We just don't have much vertebrate material where I'm at. The photos with circular borders are taken through a stereoscope at 15x magnification. The others have some level of digital zoom applied, but have a scale nearby (mm, cm). I apologize for any focus issues, this new phone has a finicky camera.