Searching for Hell Creek Formation micro sites/micro lenses

[MarcoSr 2,895]

My sons and I have been searching different formations in MD/VA for many years so we know how to recognize the different formation layers and have a good idea where to find/or at least check for micro sites/micro lenses.  My sons have also been collecting the Eocene/Oligocene formations of Nebraska for years so again they know how to recognize the formation layers.  My younger son Mel moved to South Dakota in 2018 and began to also collect the Lance Formation and Hell Creek Formation.  However he is still learning the different formation layers.  His interest is dinosaur fossils from these formations.  My interests are the much smaller micro dinosaur fossils as well as the micro mammal, squamate, amphibian, and fish fossils.  I’m always bugging him to send me micro matrix.  He sent me matrix this Fall.  This post is about one batch of matrix.

 

Mel’s first approach was to send matrix from small areas that have high density surface concentrations of teeth and bones.  Where Mel is collecting is more flat and rolling with different Hell Creek layers exposed on the surface versus bluffs and small cliff faces.  Mel for Thanksgiving sent me a large USPS priority box of matrix (around three gallons) from a small 6 ft. by 6 ft. area that had a high concentration of dino teeth on the surface.  Although sand/clay based this matrix was hard as concrete.  I had to use a rock hammer and a small hand sledge hammer to break what he sent into more manageable pieces (definitely not recommended if you are looking for larger specimens).  That said the matrix broke down completely in a single day in buckets of very hot tap water and dawn dish soap.  I would every few hours use finger pressure to help break up clumps.  There was very little residue left after breakdown of this matrix.  The below picture shows the residue from about 1/3 of the matrix or around a gallon.

 

 

 

The below picture shows what I found.  On the left maybe some petrified wood?  Doesn’t really look like bone.  Maybe geologic.  In the middle there is a really nice Croc tooth (4mm), seed (5mm) (maybe modern?), and a partial gar fish scale (7mm).  On the right there are several definite small bones and a few specimens that could be bones.  Looks like a terrestrial/fluvial environment.

 

 

 

 

What I found was nice but not worth the effort to remove the matrix, send it to Virginia, break the matrix down, and then to search it.  Although like I said earlier, there was very little residue after breakdown, so it took only about 15 minutes to search all of the residue.

 

Sampling different sites/layers and trial and error can be extremely tedious and non-productive if you really don’t understand the formation layers and how to recognize them in the field.  So I reached out to a TFF member for advice and insight.  He explained the matrix types and gave advice on where to take matrix samples.  Taking matrix from areas with high density surface concentrations of larger fossils is one way to sample for micros like Mel did for this matrix.  However TFF member cautioned that lots of times these concentrations of larger fossils got washed from another layer to the current area years ago and that the underlying layer may not contain much at all as seemed to be the case with this area/layer for this matrix.  When you find a good micro site/layer it is very rewarding in the micros that you can find but these sites/micro layers can be difficult to find especially if you don’t have a lot of experience with the Formation.  If anyone reading this post has any advice or insight for looking for a Hell Creek Formation specific micro site/layer please post it in a reply.

 

Marco Sr.            

Edited December 3, 2019 by MarcoSr
changed to croc based upon replies

[jpc 3,418]

Hi marco sr.   This TFF member has given you all the advice he can.  : )

In the meanwhile, it is pretty snowy in our area, so field work is on hold. 

 

Any chance you can post close ups of these finds?

 

[MarcoSr 2,895]

1 hour ago, jpc said:

Hi marco sr.   This TFF member has given you all the advice he can.  : )

In the meanwhile, it is pretty snowy in our area, so field work is on hold. 

 

Any chance you can post close ups of these finds?

 

 

Jean-Pierre

 

Thank you for your advice.  It is very useful.

 

I can post close ups.  Which numbers below are you interested in?

 

 

 

 

Marco Sr.

 

[Mike from North Queensland 376]

Marco Sr as always it is interesting to read your reports on your search through the various matrix layers for the micro fossils and your desire to search for new material.

 

Mike 

[MarcoSr 2,895]

1 hour ago, Mike from North Queensland said:

Marco Sr as always it is interesting to read your reports on your search through the various matrix layers for the micro fossils and your desire to search for new material.

 

Mike 

 

Mike

 

Thank you.  It is always exciting for me to find new micro sites/micro matrix.  I just wanted to let TFF members know with this post that a lot of times things just don't work out as I had hoped.

 

Marco Sr.

[jpc 3,418]

3, 5 and all those on the right if that is not asking too much.  

[MarcoSr 2,895]

19 hours ago, jpc said:

3, 5 and all those on the right if that is not asking too much.  

 

Jean-Pierre

 

Closeups of specimens

 

3 Croc tooth 4mm

 

 

    

 

 

5 fish scale 7mm      Looking at this under magnification I still think that this is a fish scale but it could be geologic.

 

 

 

 

 

 

 

The following are what I though were bones or could be bones.

 

6 bone 11 mm

 

 

 

 

 

7 bone 7 mm

 

 

    

 

 

8 bone 5 mm

 

 

    

 

 

9 bone 4 mm

 

 

    

 

 

10 bone 3 mm

 

 

    

 

 

11 bone 3.5 mm

 

 

    

 

12 bone 5 mm

 

 

    

 

 

Marco Sr.

Edited December 3, 2019 by MarcoSr
change to croc based upon replies

[Troodon 18,070]

The tooth looks like Croc not Champosaurus 

[jpc 3,418]

42 minutes ago, Troodon said:

The tooth looks like Croc not Champosaurus 

I agree.  The fish scale looks a lot like a gar scale but it has some thing that bug me.  I think it might be geological.  

 

6 is the only one I can tell you anything about.. it looks like a fish spine. 

11 and 8 might be geological...

 

 

[The Jersey Devil 682]

3 hours ago, Troodon said:

The tooth looks like Croc not Champosaurus 

Do you have any tips for differentiation between the two?

[Troodon 18,070]

Both have a cutting edges but a champ is long and lean not bulbous 

[Mike from North Queensland 376]

22 hours ago, MarcoSr said:

Thank you.  It is always exciting for me to find new micro sites/micro matrix.  I just wanted to let TFF members know with this post that a lot of times things just don't work out as I had hoped.

 

Marco Sr.

Marco Sr.

 

So true when looking for micro material, but if you do not try you will not find.

Also to note for the TFF members that when collecting matrix for micro fossils from the same lens the amount of viable fossils can vary greatly as well as the composition with relation to hardness of the matrix can vary considerably. One site I collected from the matrix may be friable enough to sieve with a little water at one point and a metre away can be that hard that to work the material would need a bath in acid for a month. Having said that I have only collected matrix from cretaceous marine lenses that were as deposited when the animals died not from reworked material where the fossils have possibly been concentrated.

 

Mike

[MarcoSr 2,895]

2 hours ago, The Jersey Devil said:

Do you have any tips for differentiation between the two?

 

2 hours ago, Troodon said:

Both have a cutting edges but a champ is long and lean not bulbous 

 

5 hours ago, Troodon said:

The tooth looks like Croc not Champosaurus 

 

4 hours ago, jpc said:

I agree. 

 

 

Looking at the below figure and the text from DeMar Jr. 06 28 12 "An Illustrated Guide to latest Cretaceous Vertebrate Microfossils of the Hell Creek Formation of northeastern Montana"  I agree on croc tooth based upon the carina  offset and not running all the way to the base of the crown.  The very small size of this tooth, 4 mm, is why I really wasn't thinking croc.

 

 

Marco Sr.

[MarcoSr 2,895]

4 hours ago, jpc said:

I agree.  The fish scale looks a lot like a gar scale but it has some thing that bug me.  I think it might be geological.  

 

6 is the only one I can tell you anything about.. it looks like a fish spine. 

11 and 8 might be geological...

 

 

 

Jean-Pierre

 

I changed that tooth to croc in my posts above.  I wasn't expecting croc teeth as small as 4 mm.

 

That specimen doesn't look quite right to me also.  However, there are concentric faint lines that are really hard to see in the picture that match fish scales that I have.

 

I have only looked at a very small amount of Hell Creek matrix before this batch and haven't really learned the texture of the bones yet.  If a specimen doesn't have a distinctive shape like 8 and 11 it is hard for me to tell for sure.  I figured that they might be geologic.

 

Marco Sr.

[MarcoSr 2,895]

2 hours ago, Mike from North Queensland said:

Marco Sr.

 

Having said that I have only collected matrix from cretaceous marine lenses that were as deposited when the animals died not from reworked material where the fossils have possibly been concentrated.

 

Mike

 

Mike

 

The reworked lenses can really concentrate the micros.  The problem with reworked lenses is that the micros can be really beat up and water worn.  I have found a few reworked lenses that are very concentrated with micros and most of the fossils are pristine.  But that is not common at all.

 

Marco Sr.

[jpc 3,418]

 marco... look at the cross section on those two potentially non-bones.  It might be different than the others.

 

Yes. I see those concentric lines n the opossible gar scale, but the groove running through the whole of one side is not normal.  It is an odd one.  

[MarcoSr 2,895]

11 hours ago, jpc said:

 marco... look at the cross section on those two potentially non-bones.  It might be different than the others.

 

Yes. I see those concentric lines n the opossible gar scale, but the groove running through the whole of one side is not normal.  It is an odd one.  

 

Jean-Pierre

 

I took a really close look at the fish scale looking specimen.  Under really high magnification the concentric lines are really clear and definitely match a gar scale.  Also the groove looks like damage where a piece of the scale broke away.  So now I'm 99% sure it is a gar scale.

 

Looking at the cross section of the specimens was interesting.  The for sure bones were uneven, not fully solid and almost flaky looking.  Like a lot of the bony fish material that I see from the Paleocene through Pliocene.  Specimens 8 and 11 are even and solid.  So they definitely look different in the cross section.  However I haven't seen enough micro specimens from the Hell Creek Formation to really interpret that.  So for now, I won't toss them but will consider them geologic.

 

Marco Sr.