Id of Ordovician Trilobites of Bumastus and lookalikes of Decorah and Platteville Formation

[Tetradium]

#1 is one of the only complete trilobite I had not identify genus yet. Rolled up and in a tough to clean rock. Upper Decorah Formation (formerly Cummingham Formation). Cant see any eyes yet. 

 

 

#2 I had picked for size - Platteville Formation. Also because they have those lines you can see more clearly on the NE specimen. 

 

#3 is the tiniest of the Decorah formation group. 

 

#4 is the largest of the Decorah group. I had double and triple checked to see if it is a brachiopod - nope. 

 

#5 is the tiniest of the platteville group. Compare to #3 its much more strongly oval shaped. 

[Tetradium]

#6 is whatever leftover - a mixture of different genus and species from both formations. 

[Tetradium]

Oh I forgot #6 the one between the 19 and 20 cm is a bit of oddity - two trilobite pygidium on top of each other - I suspects the bottom one (seen on right side of rock in photo) is Isotelus. 

[Kane]

Not all your numbering is matching up with the photos, which is creating a bit of confusion. I can say that a few of these pieces in the second photo are Thaleops. 

[piranha]

2 hours ago, Tetradium said:

Upper Decorah Formation (formerly Cummingham Formation).

 

 

Cummingsville. 

Various authors have regarded it as a formation, but the overall consensus classify it as one of three members of the Galena Formation, overlying the Decorah Formation.

 

GALENA FORMATION
The Galena formation in southeastern Minnesota comprises carbonate rocks that overlie the Decorah shales and underlie evenly interbedded limestones and shales of the Dubuque formation. It consists of thin crinkly beds that are bonded into massive units separated by the more conspicuous bedding planes, which character gives the formation a thick-bedded gross appearance. It consists of three members: Cummingsville (new), Prosser, and Stewartville, in stratigraphic order. The Cummingsville is interbedded limestone and shaly limestone, the Prosser is limestone, and the Stewartville is dolomitic limestone.

 

The Cummingsville Member

Cummingsville is the name proposed for interbedded limestones and shaly limestones at the base of the Galena formation that were formerly included in the Prosser member. The name derives from the hamlet of Cummingsville, Olmsted County, Minnesota, on State Highway 30, 3.5 miles west of Chatfield.

 

Weiss, M.P. 1955
Some Ordovician Brachiopods from Minnesota and their Stratigraphic Relations. Journal of Paleontology, 29(5):759-774

 

 

text from: MIDWEST PALEO

[Tetradium]

6 hours ago, Kane said:

Not all your numbering is matching up with the photos, which is creating a bit of confusion. I can say that a few of these pieces in the second photo are Thaleops. 

The photos is matching up with the numbers to me. Its just photos stacking from top to bottom. The second post (#6 )was separate because I wasn't in the mood to separate any more. 

[Tetradium]

3 hours ago, piranha said:

 

 

Cummingsville. 

Various authors have regarded it as a formation, but the overall consensus classify it as one of three members of the Galena Formation, overlying the Decorah Formation.

 

GALENA FORMATION
The Galena formation in southeastern Minnesota comprises carbonate rocks that overlie the Decorah shales and underlie evenly interbedded limestones and shales of the Dubuque formation. It consists of thin crinkly beds that are bonded into massive units separated by the more conspicuous bedding planes, which character gives the formation a thick-bedded gross appearance. It consists of three members: Cummingsville (new), Prosser, and Stewartville, in stratigraphic order. The Cummingsville is interbedded limestone and shaly limestone, the Prosser is limestone, and the Stewartville is dolomitic limestone.

 

The Cummingsville Member

Cummingsville is the name proposed for interbedded limestones and shaly limestones at the base of the Galena formation that were formerly included in the Prosser member. The name derives from the hamlet of Cummingsville, Olmsted County, Minnesota, on State Highway 30, 3.5 miles west of Chatfield.

 

Weiss, M.P. 1955
Some Ordovician Brachiopods from Minnesota and their Stratigraphic Relations. Journal of Paleontology, 29(5):759-774

 

 

text from: MIDWEST PALEO

Maybe I got something else mixed up. Sometimes it happens too frequently for me. Its like how I keep getting the rocks all confused so recently I decided to just use carbonate - after all what's the visual differences between shaly limestone, dolomite, and crystalized limestone. 

[Tetradium]

6 hours ago, Kane said:

Not all your numbering is matching up with the photos, which is creating a bit of confusion. I can say that a few of these pieces in the second photo are Thaleops. 

Think of it as rulers dividing the pictures. #1 through #5. Then I posted #6 on a new post.