Mazon Creek Newcomer Review and Concretion Questions

[JackInThePulpit]

I live in Chicago and for a while I’ve been wanting to try Fossil Hunting in Mazon Creek.  My first trip three weekends ago I tried to have myself prepared but still wasn’t quite sure what I was getting myself into.  I hiked to the tipple area, there I had a really hard time telling rocks from concretions because especially in that area most of the rocks are covered in an orange rust.  I collected 5 gallons of what I later realized were almost exclusively rocks.  The trip was still worth it though because there were lots of these fast little lizards running around on top of the exposed coal, and I had never seen wild lizards in Illinois before.

 

Since then, I’ve done a lot more research and went on two more trips. I mostly collected along the northern ridge of the southern section of Monster Lake. I spend nearly the entire time crawling on my hands and knees through thick undergrowth up and down ridges.  I’m sort of used to off trail hiking like that so I wasn’t very bothered by the vegetation. For a beginner I think I’ve had good success, but I still have some questions about identifying the right kinds of concretions.

 

In an ESCONI youtube video on Mazon Creek they mention that siderite plates and diagonal concretions are no good and should be left behind.  Does anyone have any tips on how to better differentiate these?  For the plates, unless it’s obviously thin I can’t quite tell. I’ve included pictures of examples of what I couldn’t quite tell were plates or not. And for the diagonals I’m honestly not sure at all.

 

Other than that I’ve so far really enjoyed fossil collecting, and I intend to continue through the summer until I am either consumed by the undergrowth, or my limited freezer space creates a massive backlog. I’m lucky in that I haven’t gotten a single tick yet (and I check thoroughly).  I treat all of my hiking clothing and equipment with permethrin and I wear both the Picaridin lotion and Deet spray. The bugs run from me.

 

Here are some concretions that I wasn't sure if they were siderite plates or not.

 

Here are some I was more certain about

[Mark Kmiecik]

The ones that you are "more certain about" are the right stuff. I'd say that 90% or more of them are definitely the right stuff. You'll get even better at differentiating which are more likely to bear fruit as you go along, although sometimes you can get lucky with the lower percentage stuff, so unless you have more than you can carry out, they're all worth the effort. The lower percentage stuff will sometimes yield a beauty, but not often. Be sure you soak those in the tubs for at least ten days before you start freezing and thawing them. They have to be soaked completely, that is ALL the way through, for the freezing to have any affect. Otherwise you're just freezing off the outer layers which I'm sure you've already noticed are partly off on some of them due to freezing and thawing where they were lying during the winter months. Check every two or three cycles for any that show a crack developing around the edge. Take those out and let them dry for a couple of days. Tap lightly around the edge with a hammer while holding the concretion in your hand until it splits open. Holding it in your hand ensures that you are not hammering too hard -- it will prevent ruining an otherwise "once in a lifetime" find. If it won't split open, soak it again and continue the freeze/thaw cycles.

 

Just looking at what you have found tells me that you will probably have at least 25 good specimens. Good luck. By the way, nice haul for your third time out. As you have already learned, good things come to those who crawl through the thick stuff. P.S. -- Nylon and cordura work better than cotton in the thick stuff.

 

Post photos of all of them when they open, even the duds. There's things to learn from them too, and some that you may think are duds may be a species with which you are not yet familiar.

    

[JackInThePulpit]

30 minutes ago, Mark Kmiecik said:

The ones that you are "more certain about" are the right stuff. I'd say that 90% or more of them are definitely the right stuff. You'll get even better at differentiating which are more likely to bear fruit as you go along, although sometimes you can get lucky with the lower percentage stuff, so unless you have more than you can carry out, they're all worth the effort. The lower percentage stuff will sometimes yield a beauty, but not often. Be sure you soak those in the tubs for at least ten days before you start freezing and thawing them. They have to be soaked completely, that is ALL the way through, for the freezing to have any affect. Otherwise you're just freezing off the outer layers which I'm sure you've already noticed are partly off on some of them due to freezing and thawing where they were lying during the winter months. Check every two or three cycles for any that show a crack developing around the edge. Take those out and let them dry for a couple of days. Tap lightly around the edge with a hammer while holding the concretion in your hand until it splits open. Holding it in your hand ensures that you are not hammering too hard -- it will prevent ruining an otherwise "once in a lifetime" find. If it won't split open, soak it again and continue the freeze/thaw cycles.

 

Just looking at what you have found tells me that you will probably have at least 25 good specimens. Good luck. By the way, nice haul for your third time out. As you have already learned, good things come to those who crawl through the thick stuff. P.S. -- Nylon and cordura work better than cotton in the thick stuff.

 

Post photos of all of them when they open, even the duds. There's things to learn from them too, and some that you may think are duds may be a species with which you are not yet familiar.

    

Thank you, that’s good advice! And that’s only half of my second haul. My most recent haul I nearly filled 5 gallons! (The walk back is miserable) I’m probably not being selective enough though. Will you select partially opened ones? Here’s an example below, it wasn’t clear to me if it had really opened yet because it seems like more of a crater style opening. Will soaking and freezing open it further?

Thank you.

 

[deutscheben]

Welcome to the Mazon Creek collecting community!
 

That looks like a pretty typical Essexella- they often split unevenly like that, with one half much thicker than the other.

 

Best of luck, it sounds like you are putting in the time and effort to collect in volume, which is the best way to increase your chances of finding something good- I can’t say I have ever come close to filling a 5-gallon in a day at Pit 11. 

[JackInThePulpit]

10 hours ago, deutscheben said:

Welcome to the Mazon Creek collecting community!
 

That looks like a pretty typical Essexella- they often split unevenly like that, with one half much thicker than the other.

 

Best of luck, it sounds like you are putting in the time and effort to collect in volume, which is the best way to increase your chances of finding something good- I can’t say I have ever come close to filling a 5-gallon in a day at Pit 11. 

Thank you! With enough cliff bars and bug spray anything is possible.

[Mark Kmiecik]

2 hours ago, JackInThePulpit said:

Thank you! With enough cliff bars and bug spray anything is possible.

 

Plus determination! Hint: Walk as far out as you think you'll go and start filling the bucket on the way back to the car. If you have time make a second trip. That way you'll still have enough arm left to turn the steering wheel. One time at a particularly good location I filled nine 5-gallon buckets brimming over. That equalled five half-mile trips back to the car carrying two 90-pound buckets and back to the buckets to pick up two more, etc. I thought my arms were going to fall off on the ride home. That day I learned to collect while heading towards the car.

[JackInThePulpit]

23 hours ago, Mark Kmiecik said:

The ones that you are "more certain about" are the right stuff. I'd say that 90% or more of them are definitely the right stuff. You'll get even better at differentiating which are more likely to bear fruit as you go along, although sometimes you can get lucky with the lower percentage stuff, so unless you have more than you can carry out, they're all worth the effort. The lower percentage stuff will sometimes yield a beauty, but not often. Be sure you soak those in the tubs for at least ten days before you start freezing and thawing them. They have to be soaked completely, that is ALL the way through, for the freezing to have any affect. Otherwise you're just freezing off the outer layers which I'm sure you've already noticed are partly off on some of them due to freezing and thawing where they were lying during the winter months. Check every two or three cycles for any that show a crack developing around the edge. Take those out and let them dry for a couple of days. Tap lightly around the edge with a hammer while holding the concretion in your hand until it splits open. Holding it in your hand ensures that you are not hammering too hard -- it will prevent ruining an otherwise "once in a lifetime" find. If it won't split open, soak it again and continue the freeze/thaw cycles.

 

Just looking at what you have found tells me that you will probably have at least 25 good specimens. Good luck. By the way, nice haul for your third time out. As you have already learned, good things come to those who crawl through the thick stuff. P.S. -- Nylon and cordura work better than cotton in the thick stuff.

 

Post photos of all of them when they open, even the duds. There's things to learn from them too, and some that you may think are duds may be a species with which you are not yet familiar.

    

I was starting to soak some more concretions, and one cracked open. 
It has a very suspicious H shape. Anyone seen anything like it?

 

[Mark Kmiecik]

It's mineral staining caused by the iron involved in forming the concretion. What may have caused it is not evident in this specimen. I enlarged the image and looked carefully for a sign of anything organic. No joy. You could continue with freeze/thaw under the assumption that there may be something in another layer if the nodule has some thickness to it. If it's thin then I would write this one off as a dud.

[JackInThePulpit]

Some of my concretions are opening so I thought I’d share. I’ll start with what I’m not certain on.

 

I think this might be a Shrimp?

 

No clue on this one:

 

Bristle Worm?

 

At first I thought this was some sort of trail but now it looks segmented to me:

no clue on the following:

 

ferns:

 

Some sort of plant?

 

Calamites:

 

And last but not least, I think these all are jelly fish:
 

let me know what you all think!

 

Edited June 7, 2022 by JackInThePulpit
Removed duplicate photo

[RCFossils]

8 minutes ago, JackInThePulpit said:

Some of my concretions are opening so I thought I’d share. I’ll start with what I’m not certain on.

 

I think this might be a Shrimp?

 

No clue on this one:

 

Bristle Worm?

 

At first I thought this was some sort of trail but now it looks segmented to me:

no clue on the following:

 

ferns:

 

Some sort of plant?

 

Calamites:

 

And last but not least, I think these all are jelly fish:
 

let me know what you all think!

 

[RCFossils]

This one looks like a partial “H” Animal Etacystis communis.

[JackInThePulpit]

49 minutes ago, RCFossils said:

This one looks like a partial “H” Animal Etacystis communis.

Wow that’s exciting, I’ve read about this one a lot. I was so unsure of it though I almost didn’t post it. Are they common?

[Runner64]

On 6/6/2022 at 8:18 PM, JackInThePulpit said:

 

And last but not least, I think these all are jelly fish:

Yes, these are all Essexella

 

On 6/6/2022 at 8:18 PM, JackInThePulpit said:

no clue on the following:

 

ferns:

 

Some sort of plant?

 

Calamites:

\

 

These are all vegetation.  The ones you mention as Calamites are correct and the others are various ferns.

 

On 6/6/2022 at 8:18 PM, JackInThePulpit said:

Bristle Worm?

:

 

Possible but I don't believe I see any defining characteristics on it.

 

On 6/6/2022 at 8:18 PM, JackInThePulpit said:

 

No clue on this one:

 

 

This also looks like an Essexella jellyfish to me.

[JackInThePulpit]

I had a very confusing fossil open for me yesterday.  After a number of freeze/thaws a crack appeared on one side and I tapped it open, but I believe only half of it opened on the correct plane. The most apparent aspect of it is a pigmented area that looks to be the tail of a shrimp.  I think Shrimp is most likely but the shape and proportions are confusing.

 

What throws me off the most is the line impression which I have circled below. It looks like it leads into a plane of the fossil that's still hidden.

 

Here are some other photos of the fossil.

 

If anyone has any ideas on this one, let me know

 

 

[deutscheben]

I agree that is a shrimp, probably a partial or squashed one ( I have quite a few similar ones). It is indeed possible that more is preserved below the surface of the concretion, but it would be difficult to prep and probably not worth it for a relatively common creature like this.

[JackInThePulpit]

2 hours ago, deutscheben said:

I agree that is a shrimp, probably a partial or squashed one ( I have quite a few similar ones). It is indeed possible that more is preserved below the surface of the concretion, but it would be difficult to prep and probably not worth it for a relatively common creature like this.

Thank you! Also, I keep seeing prepping being mentioned on the forum, but I’m only vaguely familiar with it. It seems like something that would be better on other types of fossils. Is that something that can be done with Mazon Creek concretions? What techniques do people use? 

[stats]

Definitely a shrimp.  Congrats!  There might be more, it's hard to say.  Only a few people to prep on Mazon Creek fossils.   The concretions are very hard!

 

Cheers,

Rich

 

[JackInThePulpit]

45 minutes ago, stats said:

Definitely a shrimp.  Congrats!  There might be more, it's hard to say.  Only a few people to prep on Mazon Creek fossils.   The concretions are very hard!

 

Cheers,

Rich

 

Thank you Rich.
Do they just go at with a dremel? Or do they use that tiny jackhammer thing?

[stats]

22 hours ago, JackInThePulpit said:

Thank you Rich.
Do they just go at with a dremel? Or do they use that tiny jackhammer thing?

Probably an air scribe.

 

Cheers,

Rich