Jump to content

orthocone collingswood from Newberry, MI


dalmayshun

Recommended Posts

This summer I was once again able to look for fossils near Newberry, MI in a degrading hill filled with drift. In my research recently, I came across a paper on the Collingwood formation drift in Newberry, and was excited to find exact descriptions of some of the layered rocks found there. I am including photos of one of them, split into its layers...and the orthocones revealed in thos layers. The orthocone has a very thin shell of some kind....they are always found flattened and usually with that line down the center indicating what was once rounded has been squished flat. In the 4.5 " orthocone showing (the third image and about 6" overall) even the open edge presents a somewhat curved opening. usually it is squared across. Over the years I have found these triangular shaped creatures filling the shale...from 1/4 " long smattering of them all over  a hashplate, to the ones that average 4 or so inches. I have not been able to figure them them out. The interesting paper I read doesn't mention them, which was a surprise to me since they are so plentiful. At any rate, If someone has a suggestion I would appreciate it. 

 

    The other thing I am curious about, is the geologic process that formed  this rock...for each of them, the split layers reveal creatures...in one of my rocks, each layer is filled with graptolites. So what was the process by which the layers formed....rain storms that  roiled the sediment and trapped a layer of animal...followed by a week or month or day or year storm that layered another 1/2 inch of sediment and captured another layer of creatures....and how did this layer than get broken up into cobbles....(the animal remains found in each of the layers sames to be consistent with all the other layers of each, so I am assuming a rather quick succession of silt was laid down....in a somewhat regular pattern. 

 

20190810_100833-picsay.jpg

20190810_101816-picsay.jpg

20190810_100849-picsay.jpg

20190810_100914-picsay.jpg

Link to comment
Share on other sites

this image of another orthcone, shows that collapsed center line indicating a tube, as well as the thinness of
the shell....in case it helps with id. This is from another cobble. 

20190810_105243-picsay.jpg

Link to comment
Share on other sites

I don't know the formation, but my firewood project is in a rain delay. :)

Perhaps a marine river delta. The graptolites would likely represent tropical storms sweeping in from open water.

Link to comment
Share on other sites

Thanks, were graptolites a deep water, still water, shallow water creature? I have a tendency to think of them as mosquito larva....

Link to comment
Share on other sites

I think surface water is a better term. They are found in deep water deposits, so they are slightly different than the average near shore dweller.

Link to comment
Share on other sites

Lol.  I didn't mean they were like mosquito larva but more like how the larva appear... near the surface and by the thousands sometimes.  So again, if they are deep water,  and the surface,  are they washed to shore to be buried... im interested in the process through which the creatures get trapped for preservation.  Thanks.  

Link to comment
Share on other sites

I'm afraid my knowledge of the subject doesn't go that deep. Maybe a real expert can shed more light ?

Link to comment
Share on other sites

The Collingwood and it's correlates such as the Billings Shale in the Ottawa area covered a large area encompassing southern Ontario, upstate New York, northern Michigan to the West, and all the way,to Anticosti Island in the St Lawrence estuary to the East.  It correlates with black shale formations in the Arctic Islands to the North.  Everywhere it represents a deepening of the water.  As well the sea floor.was somewhat anoxic, as fossils are commonly pyritized.  So, think cold, deep, and poor in oxygen, so far from land that the only sediment is the finest particles that can remain suspended.for.a.long time before settling out.  There was little in the way of benthic life, except for.a few species of trilobites that were adapted to anoxic conditions.  The graptolites were pelagic, floating at the surface and settling to the bottom when they died.  The same is likely true of the orthocones.  Think of schools of squid in surface waters of modern oceans.

 

Don

  • I found this Informative 3
Link to comment
Share on other sites

thanks so much. LOL, you know they say the "elderly" should keep learning to keep those ole synapses in the brain setting up new connections....the Fossil forum does that for me. I so appreciate the comments others make and their generosity in taking the time to do so. Thanks. 

  • I found this Informative 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...