Mucrospirifer(?) near Detroit, from what strata/era?

[Jazz]

Hello fossil experts!

 

I have a background in geosciences but know very little about fossils. I found the below fossils along the Rouge River near Detroit (Michigan). Doing some quick research, I think these are from the Mucrospirifer order, probably of the Thedfordensis species. Do you agree? (longest is about 1.5 inch / 4 cm)

The thing I'm most puzzled about is from what strata they are from. The interweb tells me these Mucrospirifer here are mostly from the Middle Devonian (Antrim shale, Traverse Group), while the location where I found these (as well as all of the upstream terrain) has younger bedrock, from the early Carboniferous/Mississippian (Coldwater Shale). This Coldwater Shale is a pretty thick deposit so a river/glacier can not puncture it easily. I used the Bedrock Geology map from www.esrs.wmich.edu/mgs/webmgs/migis.html
 

Thank you very much for your insight!

Jazz

 

[Fossildude19]

I split out your post to make it's own topic.  

You should always use the start new topic button if you want to place a request for ID. 

It won't get seen by many in a different topic. 

Welcome to the Forum.  

[Tidgy's Dad]

Hello, Jazz, and a very warm welcome to TFF from Morocco. 

Firstly, the order is Spiriferida; Mucrospirifer is the genus.

The species will be M. thedfordensis or M. mucronata, the principal differences being that the former has a more V shaped sulcus with a curved floor and a fold which is low and domed, while M. mucronata  has a more U shaped sulcus with  a flatter bottom and the fold is gentle and more flattened. 

There may be other species bottom of the photo and left, but I can't see enough detail. 

[Jazz]

Hello fossil experts!

 

I have a background in geosciences but know little about fossils. I found the below fossils along the waterline of the Rouge River, a few miles north of Detroit (Michigan). Doing some research, I think these are from the Mucrospirifer order, probably of the Thedfordensis species. Do you agree? (longest is about 1.5 inch / 4 cm)

The thing I'm most puzzled about is from what strata and geologic era they are from. The interweb tells me these Mucrospirifer in Michigan are mostly from the Middle Devonian (Antrim shale, Traverse Group), while the location where I found these (as well as all of the upstream terrain) has younger bedrock, from the early Carboniferous/Mississippian (Coldwater Shale). This Coldwater Shale is a pretty thick deposit so a river/glacier can not puncture it easily. I used the Bedrock Geology map from www.esrs.wmich.edu/mgs/webmgs/migis.html

 

Any thoughts on this? Are these Mucrospirifer from the Middle Devonian or from the early Carboniferous/Mississippian?
Thank you,

Jasper

[Misha]

They do look like M. thedfordensis, and although the genus does go beyond the Devonian a little bit I am not so sure about this species. Also these animals come from marine deposits but in the Mississippian subperiod the sea covering Michigan began to withdraw and let more swampy freshwater terrain cover the area, these probably came from the Antrim as you mentioned and it is likely that part of it is exposed somewhere by the body of water since these shales can be found below the Coldwater shales

Also I forgot to mention,

Mucrospirifer is a genus not an order and when Identifying spiriferids it is often helpful to include pictures of their hinge.

[FossilDAWG]

I believe @crinus is familiar with that area and he may be able to help.  I am a bit surprised at the suggested age/formation as I did not think there was any lower Carboniferous anywhere near Detroit or north of there.  I will say that Mucrospirifer is abundant in those Devonian formations that belong to or are coordinated with the Hamilton group.  In the lower Carboniferous one finds Spirifer which resembles Mucrospirifer but differs in internal stru,cturea.

 

Don

[Tidgy's Dad]

This is a duplicate thread.

[Fossildude19]

Topics merged.   

[Jazz]

Thank you Tim for merging!

[crinus]

I am not aware of any Mississippian exposures anywhere near Detroit.  The nearest Mississippian exposure is at Jackson, Michigan.  I would suspect that those specimens are from glacial till that brought down a large piece of Devonian from up north.  Alpena area has lots of Devonian.  There is Devonian under the surface of Detroit and the other possibility is that they came from some digging in the area.   I have seen a lot of specimens at U of M that came from core samples.  As far as species is concerned, the latest thinking is all the species are mucronata.

Joe