My first Iowa hunting experience.

[fossilcrazy]

Before heading home from this year's M.A.P.S. Expo, I was turned on by a local, to a well known fossil collecting site. The place is called Gaft and is a very small hamlet in Dubuque County, Iowa. The roadcut just SW of the Gaft is an Upper Ordovician outcrop of the Maquoketa formation, the Elgin member. To say Orthoceras can be found there is an understatement. The tan Dolostone is just stuffed with the remains of this straight Nautiloid.

This is the level my block came from The block fell from this notch This is the Dolostone packed with fossils

A nice hand sample Breaking the rock freed many pieces An artist rendition of Isorthoceras sociale

[fossilcrazy]

Two more big blocks yielded more of the same.

In the lower shales the same species are completely flattened and only a thin white impression film.

A close up shows some kind of net like pattern.

[minnbuckeye]

Great site isn't it. Looks like you had fun. Whenever I get a chance to stop there , it still amazes me how many preserved fossils there are. How could there be THAT MANY cephalopods swimming around back then.

[fossilcrazy]

Some other species present are Graptolites, Gastropods, Stylolinas, Trilobites and I found a Phyllocarid not reported as noted fauna.

Orthograptus Hormotoma Coleolus

Calymene Caryocaris

[CBOB]

Those blocks are insane! Cool stuff!

[Jeffrey P]

Wow John! Those Orthoceras hash plates look spectacular. Congratulations. Haven't see anything like that except for those polished ones from Morocco. Thanks for sharing.

[fossilcrazy]

One last thing I wanted to point out is the Nacrea or "Mother of Pearl" color play on some of the pristine Isorthoceras.

The effect is a little hard to capture in a photo and the actual material smudges very easy.

[fossilcrazy]

I have a block cut and polished, but it isn't as dramatic as the Morocco material. I'll take a picture and post the results.

[Ridgehiker]

I have a block cut and polished, but it isn't as dramatic as the Morocco material. I'll take a picture and post the results.

I actually prefer the material you collected to the Morocco specimens...more natural.

Good to see graptolites. Usually the only other fauna I find among graptolites are very small inarticulate brachiopods.

[Ludwigia]

The block fell from this notch

Could it be that you may have helped it along a wee bit?

Looks to be a very productive site! Nice finds!

I have a block cut and polished, but it isn't as dramatic as the Morocco material. I'll take a picture and post the results.

I was about to suggest doing this, but you beat me to it.

[Ludwigia]

Good to see graptolites. Usually the only other fauna I find among graptolites are very small inarticulate brachiopods.

I assume they came from Bed 1, whereas the nautiloids are from Bed 7.

[doushantuo]

You mean to tell us the shell colour patterns are preserved???

[Ash]

Wow! Love the big plate!

[Mike Pocock]

Looks like you had a really good trip with some excellent finds, Thanks for sharing

Regards

Mike

[doushantuo]

if i read Holland,Gnoli,,Histon,et al(Boll.SPI,1994),correctly,orthocone accumulations might NOT be stratigraphically condensed,but could point to mass mortality(thus making them event beds?)

[Fossildude19]

Wow John - looks like you did quite well.

The orthocones are cool, but that Phyllocarid is awesome.

Congratulations.

Regards,

[Khyssa]

Wonderful finds. The nacrea is lovely.

[PaleoWilliam]

Great finds!

[Raggedy Man]

This site is pretty amazing and I visit it about once a month. I'm glad you were able to get some specimens before the hordes of smash and grab hunters cleaned it out. There are several other outcrops in that immediate area that I hear produce some nice trilobites.

Best regards,

Paul

[fossilcrazy]

Cutting and polishing didn't do much for the cephalopods except make some profile views.

[fossilcrazy]

if i read Holland,Gnoli,,Histon,et al(Boll.SPI,1994),correctly,orthocone accumulations might NOT be stratigraphically condensed,but could point to mass mortality(thus making them event beds?)

I haven't read the 1994 publication. The possible take on the Graf site is more like a lag deposit. The Isorthoceras can be seen with multiple tests inside one another. This would only happen if physical forces worked them in a winnowing water kind of current action during deposition. There must have been a mass mortality event with the high population count. This picture shows repeated Shale/Dolostone and Dolostone/Shale cycles. Each Dolostone layer is full of Isorthoceras.

[JUAN EMMANUEL]

I love the orthocone clusters. Thanks for sharing those orthocones remind me of the Treptoceras that are abundant here in Toronto.

[piranha]

On 4/21/2016 at 7:46 PM, fossilcrazy said:

 

Calymene 

 

 

'Calymene' is no longer valid for the Graf, Iowa calymenids. 

Whittington 1971 reclassified it: Thelecalymene mammillata

 

Whittington, H.B. (1971)
A new calymenid trilobite from the Maquoketa Shale, Iowa.
Smithsonian Contributions to Paleobiology 3(1)129-136.pdf